imaging in brain tumor

Imaging in brain tumor

Prof.Dr.Abdul Gofar Sastrodiningrat,SpBS(K).Koleksi Pribadi. Dipakai di lingkungan sendiri. Tidak untuk disebarluaskan

Imaging in brain tumor

1 Brain imaging in Astrocytoma 5OverviewClassification of astrocytomasCharacteristic of astrocytomasImaging of brain tumorsPreferred ExaminationLimitations of techniquesComputed TomographyMagnetic Resonance Imaging

Magnetic Resonance SpectroscopyPerfusion-weighted imagingDiffusion-tensor imagingFunctional MRIAstrocyte characteristic on MRIRecent studies

Nuclear ImagingAngiography

2 Imaging in Brain Ependymoma 20OverviewPreferred ExaminationRadiographyMagnetic Resonance ImagingUltrasonography

3 Imaging in Brain Meningioma 27OverviewAnatomy

Preferred ExaminationLimitations of techniquesDifferential diagnosis and other problems to be condideredRadiologic interventionSpecial concerns

RadiographyDegree of confidenceFalse positives/negatives

Computed TomographyDegree of confidenceFalse positives/negatives

Magnetic Resonance ImagingGadolinium warningDegree of confidenceFalse positives/negatives

Ultrasonography


AngiographyDegree of confidenceFalse positives/negatives

4 Imaging in Chordoma 46OverviewPreferred ExaminationRadiographyComputed Tomography

Intracranial chordomasSaccrococcygeal chordomasSpinal chordomas

Magnetic Resonance ImagingIntracranial chordomasSaccrococcygeal chordomasChondromasCraniopharyngiomasPituitry adenomasClivus meningiomaLymphoma

5 Imaging in Cranial Nerve Schwannoma 59OverviewAnatomy

Preferred ExaminationLimitations of techniquesDifferential diagnosis and other problems to be condideredRadiologic interventionSpecial concerns

RadiologyComputed Tomography

Degree of confidenceFalse positives/negatives

Magnetic Resonance ImagingGadolinium warningDegree of confidenceFalse positives/negatives

Angiography

6 Craniopharyngioma Imaging 76Overview

Preferred ExaminationLimitations

RadiographyComputed TomographyMagnetic Resonance ImagingUltrasonographyNuclear ImagingAngiography


7 Imaging in Glioblastoma Multiforme 88Overview

Preferred ExaminationRadiographyComputed TomographyMagnetic Resonance ImagingNuclear ImagingAngiography

8 Brain Imaging in Hemangioblastoma 92Overview

Preferred ExaminationComputed TomographyMagnetic Resonance Imaging

9 Medulloblastoma Imaging 100Overview

Preferred ExaminationLimitations of techniques

Computed TomographyDegree of confidence

Magnetic Resonance ImagingDegree of confidence

Nuclear ImagingDegree of confidence

AngiogramDegree of confidence

10 Imaging in Oligodendroglioma 114Overview

Preferred ExaminationDiagnosisTreatment

Computed TomographyMagnetic Resonance Imaging

Degree of confidenceFalse positives/negatives

11 Imaging in Spinal Meningioma 122Overview

Summary of the 2007 WHO Grading Scheme for MeningiomaPreferred ExaminationLimitations of techniques

RadiographyDegree of confidence

Cxomputed TomographyDegree of confidence

Magnetic Resonance ImagingDegree of confidence


False positives/negativesUltrasonographyAngiography

Brain Imaging in Astrocytoma Author

Felice J Esposito, DO Staff Physician, Department of Radiology, Mercy Catholic Medical Center

Overview

Primary intra-axial brain tumors account for approximately two thirds of all brain neoplasms, whereas the remaining one third is made up of metastases. As a group, gliomas are the most common brain tumors and include astrocytomas, oligodendrogliomas, ependymomas, and choroid plexus tumors.[1] Astrocytomas account for approximately 80% of all gliomas and are the most common supratentorial tumor in all age groups. [2] See images of brain astrocytomas below.

Grade II astrocytoma in a 27-year-old woman. Nonenhanced CT scan shows a heterogeneous, ill-defined, hypoattenuating area in the right temporal lobe.


http://emedicine.medscape.com/article/339299-overview



Grade III astrocytoma in a 33-year-old woman. Nonenhanced studies (right) show a mixed-attenuation lesion (solid and cystic areas) in the right parietal lobe with adjacent vasogenic edema. After contrast enhancement (left), the solid component is enhancing.

Grade IV astrocytoma in a 73-year-old man. Top row (left to right), Nonenhanced CT images and fluid-attenuated inversion recovery (FLAIR) MRI. Bottom row, Axial nonenhanced and enhanced and coronal enhanced T1-weighted MRIs. CT demonstrates an inhomogeneous area of abnormal attenuation in the right temporal lobe that extends to the parietal region, with surrounding edema and mass effect. Enhanced MRI demonstrates heterogeneous enhancement, extensive vasogenic edema, and mass effect. Note the ependymal and subependymal enhancement involving the adjacent lateral ventricle and enhancement of the adjacent dura; this finding is consistent with spread.

Classification of astrocytomas

The following World Health Organization (WHO) classification system for astrocytomas is the most widely accepted system:

WHO grade II astrocytoma - Diffuse astrocytomas, including fibrillary astrocytomas, protoplasmic astrocytomas, gemistocytic astrocytomas

WHO grade III astrocytoma - Anaplastic astrocytomas

WHO grade IV astrocytoma - Glioblastomas, including giant-cell glioblastomas and gliosarcomas

WHO grade II astrocytoma - Pleomorphic xanthoastrocytoma

WHO grade II astrocytoma - Choroid glioma


Pilocytic astrocytomas

Subependymal giant-cell astrocytomas

Characteristics of astrocytomas

Astrocytomas are often divided into circumscribed or infiltrating tumors. Pilocytic astrocytomas and subependymal giant-cell astrocytomas are in the circumscribed group because they tend to respect anatomic boundaries and because they do not invade. Grade II, III, and IV astrocytomas are infiltrating because of their tendency to insinuate and invade. Tumor cells are often found distant from the imaged mass.

Pleomorphic xanthoastrocytomas occupy an intermediate position; although they are well circumscribed and slow growing, malignant progression may occur.

Imaging of brain tumors

Brain-tumor imaging has dramatically progressed over the past few decades with the development and refinement of computed tomography (CT) scanning, magnetic resonance imaging (MRI), positron emission tomography (PET) scanning, and advanced MR sequences.

Linscott et al compared pilomyxoid astrocytomas and pilocytic astrocytomas to determine whether they had imaging characteristics that would help in distinguishing between them, since the histopathology of pilomyxoid astrocytomas is distinct from that of pilocytic astrocytomas. CT and MRI scans, pathology reports, and clinical information from 21 patients with pathology-confirmed pilomyxoid astrocytomas were retrospectively reviewed. The investigators found that almost 50% of the tumors were located outside the typical hypothalamic/chiasmatic region and that intratumoral hemorrhage occurred in 25% of patients.[3]

Preferred examination

At present, contrast-enhanced MRI is the imaging modality of choice. The large amount of streak artifact in the posterior fossa that can be encountered with CT scanning does not affect MRI. The sensitivity of MRI studies is 82-100%, and the specificity is 81-100%. The excellent intrinsic contrast of conventional MRI makes it a sensitive study. The addition of contrast material and additional sequences can substantially improve the specificity. Additional techniques include MR spectroscopy (MRS), which allows clinicians to characterize the chemical composition of the mass by determining the presence and/or alteration of components such as lactate, N -acetylaspartate (NAA), choline (Cho), and myo-inositol (Ins). See the images below.


Low-grade astrocytoma in a 52-year-old woman. Top row (left to right), Nonenhanced CT scan, fluid-attenuated inversion recovery (FLAIR) MRI, and diffusion-weighted MRI. Bottom row (left to right), Single-voxel spectroscopic image showing with region of interest, spectrum, and perfusion image. Images show an ill-defined, hypoattenuating lesion in the right centrum semiovale extending to the left side through the body of the corpus callosum. The lesion has increased signal intensity on the FLAIR image. The true nature of the lesion cannot be easily established on anatomic imaging. Magnetic resonance spectroscopy (MRS) shows mild elevation of the choline (Cho) peak in relation to the N-acetylaspartate (NAA) peak with an inverted lactate peak. The findings are compatible with a low-grade neoplasm.

Two investigational sequences are often helpful in difficult cases, though the resultant images should be interpreted with caution. The first is perfusion-weighted imaging improves characterization of the tumor and aids in equivocal cases when other causes of signal abnormality are suggested, such as with demyelinating lesions, infarcts, and abscesses. The second is diffusion-tensor imaging, which can demonstrate the relationship of the tumor to white matter tracts.

Although MRI has distinct advantages over CT scanning, contrast-enhanced CT scanning is still used at many centers as the imaging modality for the evaluation of intra-axial mass lesions. The sensitivity of contrast-enhanced CT scanning is 65-100%, and the specificity is 72-100%. Positive aspects of CT scanning include relatively short scanning times, decreased cost, and an open environment for patients with claustrophobia.[4, 5]

Limitations of techniques

MRI and CT scanning can depict the gross morphologic characteristics of the tumor, its relationship with adjacent tissue, and certain aspects of the chemical composition of the


tumor (with MRS). Perfusion-weighted and diffusion-tensor images must be interpreted with caution.

Tumor margins are often difficult to determine with accuracy. Studies have demonstrated that the extent of tumoral involvement in grades I-III astrocytomas is underestimated when current conventional imaging is used. Although MRS has been useful, it also causes underestimation of the tumor burden. Tumor cells have been demonstrated well beyond the margin of any imaging abnormality.

Although imaging is instrumental in diagnosing the tumor and in evaluating the extent of disease or recurrence, only biopsy helps in determining the grade of tumor.

Computed Tomography

The appearance of astrocytomas on CT scans partly depends on their grade. Low-grade astrocytomas typically appear as homogeneous areas of decreased attenuation. They are relatively well circumscribed and 20% have associated calcification. Although low-grade tumors usually do not enhance, rare tumors demonstrate minimal enhancement.

Specific low-grade tumors have imaging characteristics that can increase the specificity of CT scanning. Pilocytic astrocytomas often appear as a cystic lesion with an eccentric mural nodule that strongly enhances after the administration of contrast agent. Subependymal giant-cell astrocytomas are typically near the foramen of Monro and usually occur in patients with tuberous sclerosis. Pleomorphic xanthoastrocytomas are typically supratentorial, cortically based masses with strong heterogeneous enhancement. The adjacent dura and meninges often enhance, creating the dural-tail appearance.

Grade III astrocytomas appear more heterogeneous. Edema is often appreciated, calcification is rare, and the enhancement pattern is usually more pronounced.

Grade IV astrocytomas are even more heterogeneous than tumors of other grades on CT scans, and they almost always enhance strongly. Hemorrhage and necrosis are common, but calcification is not. Extensive edema and mass effect are usually appreciated. This grade often involves both hemispheres by spreading by means of the corpus callosum or commissures.

With CT scanning, the scarcity of edema and mass effect with low-grade lesions may make the true extent of pathology difficult to ascertain. Furthermore, small lesions may not be visible if contrast material is not used.

See images of brain astrocytomas below.


Grade II astrocytoma in a 27-year-old woman. Nonenhanced CT scan shows a heterogeneous, ill-defined, hypoattenuating area in the right temporal lobe.

Grade III astrocytoma in a 71-year-old man. Contrast-enhanced (left) and nonenhanced (right) images show a cystic lesion with thick walls in the left parietal lobe, with thick rim enhancement on the enhanced image. Moderate surrounding vasogenic edema causes mass effect on the atrium of the left lateral ventricle.

Grade IV astrocytoma in a 73-year-old man. Top row (left to right), Nonenhanced CT images and fluid-attenuated inversion recovery (FLAIR) MRI. Bottom row, Axial nonenhanced and enhanced and coronal enhanced T1-weighted MRIs. CT demonstrates an inhomogeneous area of abnormal attenuation in the right temporal lobe that extends to the parietal region, with surrounding edema and mass effect. Enhanced MRI demonstrates heterogeneous enhancement, extensive vasogenic edema, and mass effect. Note the ependymal and subependymal enhancement involving the adjacent lateral ventricle and enhancement of the adjacent dura; this finding is consistent with spread.


Recurrent grade IV astrocytoma in the region of the right caudate and putamen in a 76-year-old man. Top row (left to right), Nonenhanced CT scan, nonenhanced T1-weighted MRI, T2-weighted MRI, and fluid-attenuated inversion recovery (FLAIR) MRI. Second row from top (left to right): Diffusion-weighted MRI, apparent diffusion coefficient (ADC) map, and axial and coronal contrast-enhanced T1-weighted MRIs. Third row from top: Perfusion-weighted MRIs show increased flow in the caudate and putamen but not in the other areas of abnormal signal intensity. Bottom row: Axial spectroscopic image shows the 2 regions of interest in the right caudate corresponding to the multivoxel spectra. Note the large, infiltrating mass centered in the right basal ganglia and extending to the right frontal lobe, temporal lobe, and insula. Image shows thick peripheral enhancement and central necrosis. Multivoxel spectroscopy demonstrates decreased N-acetylaspartate (NAA), elevated choline, and elevated lactate values in thecaudate.


Magnetic Resonance Imaging

MRI has increased the sensitivity and specificity in imaging astrocytomas. With the advent of the new techniques (MRS, perfusion-weighted imaging, and diffusion-tensor imaging), specificity has further improved.[6, 7, 8]

Magnetic resonance spectroscopy

MRS allows cerebral metabolites to be assessed by suppressing the signal of water and by interrogating for entities, including NAA, Cho, creatine (Cr), lactate, and lipids. The 2 main MRS techniques are single-voxel spectroscopy (shown in the image below) and chemical-shift imaging.[9, 10] Single-voxel spectroscopy is used to detect the signal from a single region during 1 measurement. Chemical-shift imaging uses additional phase-encoding pulses to obtain signals.

Normal pattern on single-voxel magnetic resonance spectroscopy (MRS) of 4 key molecules show relative heights and typical values. N-acetylaspartate (NAA) peaks at 2.0 ppm (tallest peak). Creatine (Cr) peaks at 3.0 ppm. Choline (Cho) peaks at 3.2 ppm. Myo-inositol (MI) peaks at 3.6 ppm.


Image show no evidence of recurrence in a 37-year-old woman with a history of grade 3 astrocytoma who underwent resection 7 years ago. Coronal contrast-enhanced T1-weighted, diffusion-weighted, and apparent diffusion coefficient (ADC) imaging were initially performed, followed by multivoxel magnetic resonance spectroscopy (MRS) and perfusion imaging. Because findings on cross-sectional imaging were not conclusive, additional studies were performed. MRS shows low levels of N-acetylaspartate (NAA), creatine (Cr), and choline (Cho) in an area of encephalomalacia, with a normal spectrum in the rest of the brain. Perfusion imaging shows no increased activity in the area of concern. These findings are compatible with gliosis.

With cerebral gliomas, MRS is used to assess the spectral pattern, metabolite intensities, and ratios to help grade the tumor and/or predict treatment response (see the image below). MRS can also help in evaluating for tumoral recurrence and treatment response. The intensity of NAA is correlated with neuronal density and viability. Cho is involved in the turnover of cell membranes and neurotransmitters. Cr serves as a reserve for high-energy phosphates in the cytosol of neurons. Cerebral lactate is always abnormal and indicates ineffective cellular oxidative metabolism. Free lipids are present in areas of necrosis. Compared with normal tissues, cerebral gliomas consistently


show lowered NAA intensity, elevated Cho (indicating increased membrane metabolism), and a stable or reduced Cr concentration. An Ins peak is described in certain low-grade tumors.

Perfusion-weighted imaging

Perfusion-weighted imaging involves several image acquisitions during the first pass of a bolus of contrast agent. This method allows the imager to determine the relative cerebral blood volume (rCBV). In general, the greater the rCBV, the higher the grade of tumor. Lack of notable flow indicates a nonneoplastic etiology with abnormal signal intensity, such as demyelination. Of note, mixed oligodendrogliomas can have low rCBV. Besides the prognostic information it provides, perfusion-weighted imaging can increase the yield of brain biopsy and help in differentiating recurrent neoplasm from radiation necrosis.

Diffusion-tensor imaging

Diffusion-tensor imaging is an experimental sequence that allows the imager to evaluate the structure and orientation of the white matter tracts. This sequence takes advantage of the fact that myelin restricts diffusion of water molecules in directions perpendicular to the fiber orientation. This sequence can help in determining whether neoplasm involves white matter pathways, improving the precision of surgical planning and the placement of radiation ports.

Functional MRI

Although not used in the diagnosis of astrocytomas, functional MRI (fMRI) deserves mention because it can be an important part of presurgical planning. A blood oxygen–dependent sequence is applied as the patient performs various tasks involving motor, sensory, visual, auditory, and language functions. Increased blood flow to a part of the brain is correlated with increased metabolic activity. The results are used to determine whether tumor involves vital structures (eloquent areas), a finding that may possibly affect surgical decisions.

Astrocyte characteristics on MRI

Low-grade astrocytomas are typically hyperintense on T2-weighted images. On T1-weighted images, most low-grade astrocytomas are hypointense relative to white matter. Contrast enhancement may be absent or, at best, mild. Exceptions include the mural nodule of pilocytic astrocytoma and the strong heterogeneous enhancement of pleomorphic xanthoastrocytomas. Astrocytomas are often associated with enhancement of the adjacent dura and meninges, giving the dural-tail appearance. MRS may show an elevated Cho peak and decreased NAA peak. An elevated Cho-Cr ratio or a depressed NAA-Cr ratio suggests tumor. This holds true for all high-grade tumors and many, but not all, low-grade tumors. (Some low-grade tumors may not have an elevated Cho peak.) Perfusion MRI studies fail to demonstrate increased rCBV.

Grade III astrocytomas often invade structures without destroying them, causing their ill-defined borders. The mass is inhomogeneous and bright on T2-weighted images.


Surrounding edema and/or tumor infiltration is usually appreciated. Enhancement is usually seen. Perfusion MRI demonstrates increased relative cerebral flow volume.

Grade IV astrocytomas (GBM) are usually discovered as bulky disease, and necrosis is a hallmark of this grade. These lesions usually enhance peripherally, in a nodular and irregular manner, and they cause a large amount of mass effect and edema. These tumors often cross the corpus callosum, giving them a typical butterfly shape. Areas of hemorrhage and necrosis are common, and spectroscopy demonstrates high Cho, high lactate, high lipid, and low NAA values. Short–echo time (TE) studies demonstrate an absent or low myo-inositol peak. Perfusion studies demonstrate elevated rCBV.

See MRI images of brain astrocytomas below.

Pilocytic astrocytoma in a 20-year-old man. Top row (left to right), sagittal, coronal, and axial contrast-enhanced T1-weighted MRIs. Bottom row: Axial fluid-attenuated inversion recovery (FLAIR), diffusion, and apparent diffusion coefficient (ADC) images. Note the cystic mass with an intensely enhancing mural nodule in the inferior cerebellar vermis, as well as the mass effect on the brainstem, upper cervical cord, cerebellum, and fourth ventricle.


Grade II astrocytoma in a 30-year-old man. Nonenhanced T2-weighted MRI shows a well-circumscribed area of increased signal intensity in the left temporal lobe.


Grade II astrocytoma. Left, Fluid-attenuated inversion recovery (FLAIR) image demonstrates an area of increased signal intensity in the parietooccipital region. Right, Perfusion MRI demonstrates decreased relative cerebral blood volume (rCBV), consistent with a low-grade neoplasm. The final pathologic diagnosis was a grade II astrocytoma.


Grade III astrocytoma in a 33-year-old woman. Top row (left to right), Axial nonenhanced and contrast-enhanced T1-weighted, proton density–weighted, and fluid-attenuated inversion recovery (FLAIR) MRIs. Bottom row (left to right), Sagittal nonenhanced and contrast-enhanced T1-weighted MRIs, axial diffusion-weighted images, and axial apparent diffusion coefficient (ADC) map. T1-weighted images demonstrate a well-defined area of mixed signal intensity in the right parietal lobe extending to the corpus callosum with adjacent vasogenic edema. Mixed areas represent hemorrhage. Contrast-enhanced images show minimal enhancement of the lesion. Also appreciated is dural enhancement secondary to previous intervention.


Grade III astrocytoma in a 71-year-old man. Top row (left to right), Axial nonenhanced and contrast-enhanced T1-weighted, proton density–weighted, and fluid-attenuated inversion recovery (FLAIR) MRIs. Bottom row (left to right), Sagittal nonenhanced and contrast-enhanced T1-weighted MRIs, axial diffusion-weighted images, and axial apparent diffusion coefficient (ADC) map. Images show a cystic, well-defined lesion in the left parietal region with surrounding vasogenic edema and a thick rim enhancement on enhanced images. Diffusion and ADC images shows no evidence of acute restriction.

Recent studies

In a study, Bing et al concluded that first-pass perfusion MRI is a quick and useful way to differentiate between pilocytic astrocytomas and hemangioblastomas. They also maintained that the maximum rCBV (rCBVmax), defined as the ratio between the CBVmax in tumor tissue and the CBV in healthy, contralateral white matter, is indicative of the tumor type. Because pilocytic astrocytomas and hemangioblastomas can present the same morphologic characteristics on conventional MRI sequences, the authors studied 11 patients with pilocytic astrocytomas and 8 with hemangioblastomas, who underwent first-pass perfusion MRI to differentiate the tumors.[11]

The investigators found that the difference between the rCBVmax of pilocytic astrocytomas (rCBVmax = 1.19 ± 0.71, range 0.6-3.27) and that of hemangioblastomas (rCBVmax = 9.37 ± 2.37, range 5.38-13) was significant. The first-pass curve crossed the baseline, corresponding to vascular permeability problems in pilocytic astrocytomas and hemangioblastomas.


Nuclear Imaging

Primary brain tumors generally have increased glucose metabolism on [18F]fluorodeoxyglucose (FDG) PET scan studies (see the image below). [12, 13] The degree of metabolic activity is correlated with the grade of the tumor and the patient's prognosis. Low-grade tumors may demonstrate little to no increased uptake, whereas grade IV lesions often have uptake that overshadows that of the gray matter.

A, Image in a patient after resection of a left frontoparietal, high-grade astrocytoma. Positron emission tomography (PET) demonstrates increased activity in this region, consistent with recurrence.

B, Image in another patient being evaluated for recurrence of a high-grade astrocytoma. Image shows no abnormally increased activity to suggest recurrence.

Angiography

Angiography is being used in several ongoing trials to assess the intratumoral treatment of grade III and IV astrocytoma.

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AVAILABEL AT : http://emedicine.medscape.com/article/336695-overview#a24


Imaging in Brain Ependymoma Author

William Jeffery Klein, MD Radiologist, Radiology Alliance, PC

William Jeffery Klein, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, Medical Society of Virginia, and Radiological Society of North America

Coauthor(s)

Michael G D'Antonio, MD Clinical Associate Professor of Radiology, Louisiana State University Health Sciences Center, New Orleans; Consulting Staff Radiologist, Jefferson Radiology Associates, Inc, West Jefferson Medical Center

Hugh J F Robertson, MD, DMR, FRCPC, FRCR, FACR Professor Emeritus of Radiology, Professor of Clinical Radiology, Louisiana State University Health Sciences Center, New Orleans; Clinical Professor of Radiology, Tulane University School of Medicine; Active Staff, Department of Radiology, University Hospital

Hugh J F Robertson, MD, DMR, FRCPC, FRCR, FACR is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Neuroradiology, American Society of Spine Radiology, Louisiana State Medical Society, Orleans Parish Medical Society, Radiological Society of North America, Royal College of Physicians and Surgeons of Canada, Royal College of Radiologists, and Royal Society of Medicine

Overview

Ependymoma is a central nervous system (CNS) neoplasm composed of glial cells that have differentiated along ependymal lines. These lesions occur most commonly in the ependymal lining of the ventricles, but they also arise in the filum terminale and the central spinal canal.[1, 2, 3, 4] See the image below.

Ependymoma arising from the fourth ventricle. A 13-year-old girl with recent onset of headache, nausea, vomiting, and papilledema. Nonenhanced axial computed tomography image demonstrates a large, round tumor arising from the fourth ventricle with attenuating nodular calcifications. Obstructive hydrocephalus is noted with frontal lobe white matter of low attenuation resulting from subependymal cerebrospinal fluid absorption.



http://www.rsm.ac.uk/

http://www.rsm.ac.uk/

http://www.rcr.ac.uk/

http://rcpsc.medical.org/index.php?pass=1

http://www.rsna.org/


http://www.opms.org/

http://www.lsms.org/

http://www.theassr.org/

http://www.theassr.org/

http://www.asnr.org/

http://www.arrs.org/

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http://www.acr.org/


http://www.msv.org/


http://www.acr.org/

Preferred Examination

Radiologic imaging plays a role in both the diagnostic workup and treatment of patients with ependymoma; imaging is essential to assess for response to therapy and recurrence. Patients with CNS symptoms routinely undergo cross-sectional imaging. Computed tomography (CT) scanning is often the modality used initially to evaluate for intracranial hemorrhage, mass, or mass effect. A general limitation of CT is radiation exposure. Additionally, the use of iodinated contrast material may sometimes be associated with nausea, vomiting, and rare anaphylactoid reactions. Limitations of CT with respect to ependymoma include imprecise anatomic detail.

If a tumor is suspected, magnetic resonance imaging (MRI) is the next study performed. In fact, MRI is the chief modality used in the study of ependymomas. MRI better characterizes CNS tumors, and findings often lead to a presumptive diagnosis. CT scanning is a useful adjunct. Before the development of cross-sectional and multiplanar imaging, angiography and pneumoencephalography were used to localize brain masses and characterize tumor vascularity.

General limitations of MRI include its cost and the need for patient cooperation. Patient motion is a cause of considerable artifact. Many patients, especially children and patients with claustrophobia, require sedation. Another general limitation is the incompatibility of MRI with numerous foreign and/or medically implanted objects, such as pacemakers. Finally, MRI is of limited benefit in the evaluation of cortical bone and the detection of calcium.

Ultrasonography, nuclear medicine studies, angiography, and radiography are of no benefit in the workup of ependymoma.

The final diagnosis of ependymoma, as with most CNS neoplasms, is achieved with tissue sampling; however, when correlated with demographic and clinical features, MRI and CT scan findings can be strongly suggestive of ependymoma.

Radiography

Radiographic findings are included only for historical interest. A study by Barone and Elvidge demonstrated that in 45 pathology-proven cases of ependymoma, intracranial calcifications were present in 6 patients.[5] The pineal gland was calcified in 4 patients, and the pineal gland was displaced from the midline in 2 patients. Separation of the sutures occurred in 12 patients. In the 43 patients in whom ventriculography was performed, 41 demonstrated hydrocephalus with identification of the site of obstruction.[5]


MRI has supplanted CT scanning as the diagnostic modality of choice in the workup and follow-up observation of intracranial neoplasms, including ependymoma. The most





appropriate role for MRI in the treatment of ependymoma is in the detection of tumor and direction of its resection and/or irradiation. MRI is used to monitor ongoing treatment and to survey for recurrence. Although the MRI findings can be of great help in narrowing the differential diagnosis of brain tumors, final diagnosis is achieved through histologic sampling.

Solid portions of ependymoma are typically isointense to hypointense relative to white matter on short recovery time/echo time (TR/TE) T1-weighted images. The tumor is hyperintense to white matter on long TR/TE T2-weighted images. As many as 50% of ependymomas demonstrate signal heterogeneity, which may indicate calcification, necrosis, methemoglobin, hemosiderin, or tumor vascularity.[6, 7, 8] For example, hyperintense foci on both T1- and T2-weighted images suggest methemoglobin in subacute hemorrhage of 1-4 weeks in age, whereas hypointense foci on both T1- and T2-weighted images suggest hemosiderin, calcium, or necrosis. See the images below.

Fourth-ventricle ependymoma in a 63-year-old man with headaches. T1-weighted sagittal image demonstrates an oval, fourth ventricular tumor with hypointense signal. Moderate obstructive hydrocephalus of the lateral and third ventricles is noted.


Fourth-ventricle ependymoma. T1-weighted coronal postgadolinium image in the same patient as in the previous image. Homogeneous enhancement of a fourth ventricular mass is noted, with extension downward through the foramen of Magendie. Pathologic analysis demonstrated subependymoma.

Punctate calcific foci are difficult to diagnose prospectively but are present in as many as 45% of ependymomas.[8, 9] See the following images.

Anaplastic brain parenchymal ependymoma in a 5-year-old girl with seizures. T1-weighted axial image demonstrates a heterogeneous mass in the right frontal lobe. Note the bright contrast enhancement within the neoplasm and areas of low signal intensity consistent with calcification.

Anaplastic parenchymal ependymoma in the same patient as in the previous image. T2-weighted axial image shows heterogeneous high signal intensity in the tumor and adjacent vasogenic edema, with low-signal-intensity calcifications. There was no connection with the lateral ventricle noted on imaging or at the time of surgery. Pathologic analysis demonstrated malignant (anaplastic) ependymoma.


Cystic changes result in high signal intensity on T2-weighted MRIs, as shown in the images below.

Anaplastic ependymoma of the lateral ventricle in an 8-week-old girl with hydrocephalus. Gadolinium-enhanced coronal T1-weighted image demonstrates a large anaplastic ependymoma of the left lateral ventricular roof. Note the cystic component, mass effect, and subfalcine herniation.

Anaplastic ependymoma of the lateral ventricle in the same patient as in the previous image. Gadolinium-enhanced axial T1-weighted image demonstrates a large anaplastic ependymoma of the left lateral ventricular roof. Note the cystic component, mass effect, and subfalcine herniation.

Signal heterogeneity is a feature useful in distinguishing ependymoma from the more homogeneous medulloblastoma. Calcification and hemorrhagic foci are more typical of ependymoma than medulloblastoma. Additionally, ependymomas are more apt to extend through the foramina of Luschka and Magendie, hence the term plastic ependymoma (see the following images). Similarly, choroid plexus papilloma is more homogeneous than ependymoma and lacks the typical irregular margins and surrounding edema of ependymoma.

Ependymoma arising from the fourth ventricle in a 50-year-old woman with a history of dizziness and nausea, progressive over several years. A lobulated mass on this proton density–weighted sagittal image arises from the fourth ventricle and extends distally through the foramen of Magendie. Pathologic analysis demonstrated cellular ependymoma. Note the hydrocephalus.


Fourth-ventricle ependymoma in the same patient as in the previous image. A lobulated mass on this proton density–weighted coronal image arises from the fourth ventricle and extends distally through the foramen of Magendie. Pathologic analysis demonstrated cellular ependymoma.

Enhancement with gadolinium is useful in differentiating tumor from adjacent vasogenic edema and normal brain parenchyma. Without intravenous contrast enhancement, T2-weighted images are more reliable in differentiating tumor margins than are T1-weighted images.[9]

Some reports describe ependymomas that cause displacement of the vein of the lateral recess of the fourth ventricle on cerebral arteriography.[9] This vein normally courses from the transverse and lateral supratonsillar veins along the anterior and lateral aspect of the superior pole of the cerebellar tonsil. It then courses lateral to the cerebellopontine angle, over the brachium pontis, to join the petrosal vein. Ependymoma expanding the fourth ventricle and its lateral recesses can displace this vein posteriorly and laterally.

Supratentorial ependymomas can differ in appearance from intraventricular ependymomas. Supratentorial ependymomas are more commonly located in the brain parenchyma than infratentorial ependymomas, which are often intraventricular. Swartz and colleagues reported that 83% of supratentorial ependymomas were located in the parenchyma. [10]

Supratentorial ependymomas tend to be larger than infratentorial ependymomas, with 94% being larger than 4 cm in one study.[11] In addition, supratentorial extraventricular ependymomas are often extraventricular and more often have a cystic component, with or without a mural nodule. In these cases, the differential diagnosis includes ganglioglioma, pleomorphic xanthoastrocytoma, and pilocytic astrocytoma. In the posterior fossa, medulloblastoma and cerebellar astrocytoma can mimic the appearance of an ependymoma.[5]

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy.

NSF/NFD has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. Characteristics



include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see FDA Information on Gadolinium-Based Contrast Agents or Medscape.

Ultrasonography

The role of ultrasonography in the evaluation of ependymoma is limited. Fetal ultrasonography and pediatric transcranial sonography are used primarily as screening tools for other pathologic conditions but can detect hydrocephalus reliably. A study by Han and colleagues demonstrated that 6 of 1528 infants undergoing transcranial ultrasonography had a pathologically proven brain neoplasm.[9] One patient had ependymoma. Ultrasonography demonstrated a solid echoic fourth ventricular mass with localized, well-defined, anechoic cystic areas.[9] These findings are not sensitive or specific for ependymoma.

Availabel at : http://emedicine.medscape.com/article/341527-overview#a24


http://www.medscape.com/viewarticle/550122

http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm142882.htm


Imaging in Brain Meningioma Author

German C Castillo, MD, FACR. FICS Assistant Professor, Department of Diagnostic and Interventional Radiology, Harvard Clinic and Central University of Ecuador

German C Castillo, MD, FACR. FICS is a member of the following medical societies: American Roentgen Ray Society, International College of Surgeons, and Radiological Society of North America

Overview

Meningiomas represent 15% of all brain tumors. These lesions are the most common extra-axial tumors in the brain and the most frequently occurring tumors of mesodermal or meningeal origin.[1, 2, 3, 4, 5]

Advances in radiologic imaging techniques, such as computed tomography (CT) scanning and magnetic resonance imaging (MRI), have improved the surgeon's ability to predict the success for complete removal of the mass. Imaging information about the dural attachment site, location and severity of edema, and displacement of critical neurovascular structures is useful for planning the operative approach and affects outcome.[6, 7, 8] See the images below.

Brain meningioma. Posterior tentorial meningioma on a coronal contrast-enhanced computed tomography scan. A hyperattenuating and well-marginated mass is adjacent to the tentorium. Pooling of cerebrospinal fluid, subtle edema, homogeneous enhancement, and ventricular dilatation are demonstrated.




http://www.icsglobal.org/


Brain meningioma. Nonenhanced computed tomography scan shows a malignant meningioma in the frontal convexity that appears as a spontaneously hyperattenuating mass. The cystic cavity may be tumor necrosis, old hemorrhage, cystic degeneration, or trapped cerebrospinal fluid. Edema and midline shift to the left anterior aspect is observed.

Brain meningioma. Nonenhanced computed tomography scan shows a malignant meningioma in the frontal convexity. The hyperattenuating and inhomogeneous enhancing mass and a ring-shaped enhancement is shown.

Brain meningioma. Parietal-convexity meningioma. Selective injection of the left middle meningeal artery shows inhomogeneous enhancing tumor. Intense vascularity is appreciated on the posterior aspect of the mass. Drainage veins are not seen.

Brain meningioma. Nonenhanced T1-weighted sagittal magnetic resonance image demonstrates a typical parasagittal meningioma. A homogeneous, long-T1, round mass with thin capsule is present. The tumor is attached to the left sagittal dura. Mass effect is noted against the ventricular trigone.


Brain meningioma. Nonenhanced axial magnetic resonance image demonstrates a typical parasagittal meningioma. T1-weighted image shows a homogeneous, long-T1, round mass with thin capsule. The tumor is attached to the left side of the falx. Mass effect is noted on the adjacent gyri.

Neuroradiologists and neurosurgeons must be aware of both the typical and atypical imaging appearances of meningiomas, as there is some correlation with different histologic types of tumor.

The World Health Organization (WHO) classifies meningiomas into 3 categories: (1) typical or benign (88-94%), (2) atypical (5-7%), and (3) anaplastic or malignant (1-2%). Significant factors contributing to recurrence include atypical and malignant histologic types (WHO classification) and heterogeneous tumor contrast enhancement on CT scans.

Anatomy

Meningiomas arise from arachnoid cells, particularly those packing the arachnoid villi, which protrude as fingerlike projections into the walls of the dural veins and sinuses. Most meningiomas grow inward toward the brain as discrete well-defined, dural-based masses and are spherical or lobulated. Flat tumors termed en plaque infiltrate the dura and grow as a thin carpet or sheet of tumor along the convexity dura, falx, or tentorium. Dural attachment of meningiomas can be pedunculated or broad-based (sessile). Because the pia and arachnoid form a membranous barrier between brain and tumor, some meningiomas grow into the subarachnoid space, but invasion of the brain is infrequent.


MRI is preferred for the diagnosis and evaluation of brain meningiomas. CT scanning well depicts bony hyperostosis, which may be difficult to appreciate on MRI. CT scanning may, however, fail to demonstrate en plaque and posterior fossa meningiomas.


CT scanning has limitations in performing direct imaging in any other plane than axial. However, with the onset of spiral CT scanning and, more recently, multisection or multidetector-row CT (MDCT) scanning, the quality of sagittal and coronal images that can be reconstructed from axial data has increased significantly. CT scanning is less helpful than MRI in differentiating different types of soft tissue.


Differential diagnosis and other problems to be considered

Brain astrocytoma, cavernous angiomas of the brain, neurofibromatosis type 2, central nervous system (CNS) sarcoidosis and CNS tuberculosis are included in the differential diagnosis. Other conditions to consider are dural vascular malformation, hemangioma, and extramedullary hematopoiesis.

Radiologic intervention

The development of catheters and the continued refinement of embolic materials and radiographically controlled interventional procedures have contributed to improved treatment of patients with brain meningiomas. The clinician must be aware of the active participation of the neurosurgeon and neuroradiologist in the therapy of neurosurgical patients.[9, 10]

The best available treatment for benign meningiomas is complete surgical resection of the tumor. Nevertheless, interventional neuroradiologists should contribute in performing preoperative embolization to reduce the blood supply to the tumor. All meningiomas are benefited by embolization, but especially those with a complex presentation, giant meningiomas, meningiomas exhibiting malignant or angioblastic characteristics, or meningiomas involving the skull base, scalp, or critical vascular structures.The preoperative embolization of meningiomas is commonly used to facilitate surgery.

Embolization can be carried out at the same time as the diagnostic angiography session or may occur later if detailed procedural planning is required. Distal, homogeneous, and permanent occlusion of the vascular bed by injecting small particles (150-300 microns of polyvinyl alcohol [PVA]) through microcatheters is the goal. Bilateral dural devascularization shortens the surgical resection time and permits total removal of the tumor. The procedure causes tumor necrosis, expanding the spectrum of meningiomas that can be safely resectioned during surgery.

PVA particles ranging in size from 100 to 2000 microns have been used, but the newer class of deformable particles and Bead Block have been shown to be more effective in distal embolotherapy to reach the capillary bed of the meningioma. Embospheres can be tagged with chemotherapeutic agents. Several meningiomas of the convexity have been embolized with Embospheres in our experience.

Approximately 2% of patients have complications associated with embolization that result in neurologic deficits. At the theoretical level, embolization may reduce the likelihood of recurrence. Embolization also may be the only treatment required in older or high-risk patients. See the images below.








Brain meningioma. Cerebellopontine angle meningioma. T2-weighted magnetic resonance image shows a hyperintense mass attached to the petrous bone. Sharply defined tumor margin, subtle edema, and mass effect on the fourth ventricle and the brainstem are present. Hyperintensity on the T2-weighted image indicates a soft tumor consistency and microhypervascularity, which is seen more often in aggressive, angioblastic, or meningothelial meningioma.


Brain meningioma. Cerebellopontine angle meningioma. Selective angiogram of right occipital artery shows focal hypervascularity through the auricular artery. Early and delayed staining is seen.

Brain meningioma. Cerebellopontine angle meningioma. Right occipital artery embolized with polyvinyl alcohol particles before surgery.

Multiple meningiomas. A: Sagittal T1-weighted magnetic resonance image (MRI) demonstrates posterior fossa and parietal meningiomas. B: Gadolinium enhancement on sagittal T1-weighted MRI shows intense enhancing of the masses. C: T2-weighted coronal MRI shows stable hypointense appearance of the posterior mass after endovascular embolization

Malignant and multiple meningiomas. A 47-year-old white male underwent gamma knife surgery due to left convexity meningioma, followed by microsurgical removal of the tumor in 2001. A, B: Four years later, in 2005, MRI showed a stable residual parietal/occipital mass. The left sigmoid sinus is occluded. C, D: One small right frontal meningioma also underwent radiosurgery at the same time. Edema and intense enhancing after gadolinium injection is demonstrated.


A-D: Coronal T2-weighted and enhanced T1-weighted magnetic resonance images demonstrate quick growth of a convexity mass toward the tentorium and the petrous bone. This bone structure is filled with liquid in its inferior aspect. Surgical biopsy reported "atypical meningioma."

Coronal computed tomography scan. This bone window shows petrous bone destruction and partial lack of bone plane after surgical removal of the tumor.

Digital subtraction angiography. A, B: Left external carotid artery shows early and delayed stain of the mass through media meningeal, superficial temporal arteries. C: Occipital artery. D: The branches were embolized before the surgical procedure. The tumor was partially removed due to cranial base involvement.


Frontal meningioma. A, B: Slow growth and surrounding edema is seen on magnetic resonance imaging (MRI) control of this tumor. Coronal, enhanced-T1 weighted and fluid attenuation inversion recovery (FLAIR) sequences are shown. C, D: Digital angiography. Right media meningeal branch demonstrates feeding of the tumor. It was not embolized.

A: 3-dimensional (3-D)-enhanced T1-weighted magnetic resonance image (MRI) image shows residual meningioma at the cranial base after second surgical removal. B: Coronal T2-weighted MRI shows intense edema surrounding the frontal mass. C: 3-D image on enhanced T1-weighted MRI demonstrates frontal meningioma underlying the orbital right sulcus. D: Gadolinium-enhanced, axial T1-weighted image shows 1 of the 3 focal hyperintense masses discovered only on this sequence. Brain metastases from meningioma have not been proved.

Special concerns

A growing number of lawsuits that name radiologists involve special procedures. [11, 12, 13, 14]

Good technique, good planning, and informed consent, which includes the involvement of the interventional neuroradiologist, can help physicians prevent most claims.

Radiography

In most patients, no findings of meningiomas are present on plain radiographic examination. Plain skull images may demonstrate calcification in meningiomas of the skull base or convexity. Meningiomas displayed reactive hyperostosis without connection to the size of the tumor. Rare osteolysis is associated with the benign and aggressive meningiomas.


Degree of confidence

Most plain skull radiographs do not depict signs of meningiomas. Meningiomas en plaque have diffuse hyperostosis, more frequently observed over the sphenoid wing and pterion. This finding results in a high degree of confidence.

False positives/negatives

Calcification within the tumor is a considerably less frequent plain radiographic manifestation; therefore, false-negative results occur. Most patients with brain meningiomas do not undergo radiographic imaging because the diagnosis has been made directly with CT scanning or MRI.

Computed Tomography

CT scanning has several advantages in the imaging of meningiomas.[15, 16, 17, 18, 19, 20, 21, 22]

Invasion of surrounding dura frequently provokes an osteoblastic response, causing hyperostosis.[23]

This imaging modality is used best for demonstrating calcification of meningiomas (see the images below). The CT nature of the calcification may be nodular, fine and punctate, or dense.

Brain meningioma. Nonenhanced computed tomography scan demonstrates a middle fossa meningioma. The calcified mass is attached to the anterior ridge of the right petrous bone. Ring and punctate calcification are depicted. Edema is not appreciated.


Two different cases. A, B: Computed tomography (CT) scans depict calcified meningiomas from the parietal convexity. C: Nonenhanced axial CT image shows homogeneous calcified mass attached to the right parietal bone. Soft-tissue tumor is seen at the posterior aspect of the calcification (large arrow). Other minor calcifications on the left cerebral hemisphere are caused by a parasitic disease. D: Coronal T2-weighted magnetic resonance image demonstrates calcium deposit (star) surrounded by solid tissue (small arrow); edema is not seen in this case.

CT scanning is effective in showing hyperostosis, bone destruction, and erosion at the site of the dural attachment (see the following images). Hyperostosis is seen in 15-20% of patients.


Brain meningioma. Nonenhanced computed tomography scan shows a malignant meningioma in the frontal convexity that appears as a spontaneously hyperattenuating mass. The cystic cavity may be tumor necrosis, old hemorrhage, cystic degeneration, or trapped cerebrospinal fluid. Edema and midline shift to the left anterior aspect is observed.

Brain meningioma. Nonenhanced computed tomography scan shows a malignant meningioma in the frontal convexity. The hyperattenuating and inhomogeneous enhancing mass and a ring-shaped enhancement is shown.

Brain meningioma. Malignant frontal-convexity meningioma. Computed tomography scan of the frontal internal table and diploe shows erosion and bone infiltration.

CT scanning can also show acute tumor hemorrhage and widened vascular grooves in the calvarium. In addition, homogeneous masses with attenuation similar to the surrounding brain make up 25-33% of meningiomas. The remainder are hyperattenuating compared with the brain. Meningiomas can exhibit extensive edema. Inhomogeneous enhancement can result due necrosis or rare hemorrhage. Edema is absent in 50% of patients because of slow growth, but it may be extensive. Edema predominantly affects white matter, and it resembles fingers of low attenuation units. See the images below.


Brain meningioma. Nonenhanced computed tomography scan shows an isoattenuating sphenoid-wing meningioma. The left sylvian fissure is partially collapsed.

Brain meningioma. Computed tomography scan shows an isoattenuating sphenoid-wing meningioma. The contrast-enhancing mass is attached to the major sphenoid wing and was demonstrated only after the intravenous injection of contrast material.

Contrast-enhanced CT scanning displays moderate to strong homogeneous enhancement in most tumors. Steinhoff et al observed a nodular blush in 97%, a mixed inhomogeneous blush in 0.5%, and a ring blush in 1.5%.[24] In a study by Naidich et al, tumor blush was nodular and nearly homogeneous in 70% of patients, inhomogeneous in 24% of patients, and ringlike in 2% of patients.[25]

Cystic components of the meningiomas may be present inside the tumor or between the tumor and the adjacent brain, so-called trapped CSF. Peripheral cysts resulting from trapped CSF can also be present. See the image below.


Brain meningioma. Posterior tentorial meningioma on a coronal contrast-enhanced computed tomography scan. A hyperattenuating and well-marginated mass is adjacent to the tentorium. Pooling of cerebrospinal fluid, subtle edema, homogeneous enhancement, and ventricular dilatation are demonstrated.


Meningiomas are well-circumscribed peripheral or falcine masses that deform the brain. About 90% of meningiomas are demonstrated on CT scans. The main role of CT scanning, as opposed to other imaging modalities, is the demonstration of adjacent bone changes and calcification within the lesion.

Atypical CT scan features are the primary reason for preoperative misdiagnosis. Posterior fossa meningiomas may be missed by this imaging modality, as will be some en plaque lesions. CT scanning can fail to demonstrate cystic changes in intracranial meningiomas. CT scan features, such as irregular areas of nonenhancing mass and well-defined regions of persistent low attenuation, are the reason for preoperative misdiagnosis.


False-negative findings can occur with cystic changes in brain meningiomas; false-positive findings can occur with large dural calcification, which can mimic the disease.



An important advantage of MRI in the imaging of meningiomas is its superior resolution of different types of soft tissue, multiplanar capability, and 3-dimensional (3-D) reconstruction (see the images below).[17, 18]

Parasagittal meningioma. A: Nonenhanced Sagittal T1-weighted magnetic resonance image (MRI) shows a solid dural isointense mass with bone invasion and compression against the parietal cortex. B: Contrast-enhanced sagittal T1-weighted MRI demonstrates partially intense enhancement of the tumor. C: Coronal T2-weighted image shows isointense mass meaning hard tissue. This finding is observed on fibroblastic meningiomas. D: Contrast-enhanced T1-weighted axial MRI shows hyperintense image located within the bony marrow.

A: Noncontrast angio-magnetic resonance image (MRI) on lateral view demonstrates occluded superior sagittal sinus due to meningioma invasion. B: MRI reconstruction shows sagittal venous obstruction and 3-dimensional (3-D) appearance of the tumor.

MRI can demonstrate tumor vascularity, arterial encasement, venous sinus invasion, and the relationship between the tumor and surrounding structures. This modality is particularly advantageous in depicting the juxtasellar area and the posterior fossa and in demonstrating the rare presence of disseminated disease via the CSF. The multiplanar capability is often the best means to visualize the broad contact of tumors to the meninges, tumor capsules, and meningeal contrast enhancement adjacent to the tumor.[26, 27, 28] See the following images.


Brain meningioma.

Nonenhanced T1-weighted sagittal magnetic resonance image demonstrates a typical parasagittal meningioma. A homogeneous, long-T1, round mass with thin capsule is present. The tumor is attached to the left sagittal dura. Mass effect is noted against the ventricular trigone.

Brain meningioma.

Nonenhanced axial magnetic resonance image demonstrates a typical parasagittal meningioma. T1-weighted image shows a homogeneous, long-T1, round mass with thin capsule. The tumor is attached to the left side of the falx. Mass effect is noted on the adjacent gyri.


Brain meningioma.

Coronal T2-weighted magnetic resonance image demonstrates a typical parasagittal meningioma. Isointense and inhomogeneous tumor without peripheral edema indicates a more fibrous and harder character (ie, a fibroblastic meningioma).

Brain meningioma.

Contrast-enhanced T1-weighted axial magnetic resonance image demonstrates a typical parasagittal meningioma. A homogeneous, enhancing, globose mass is depicted.


Brain meningioma.

Contrast-enhanced T1-weighted coronal magnetic resonance image shows a typical parasagittal meningioma. A homogeneous, enhancing, globose mass is depicted.

On nonenhanced T1-weighted images, most meningiomas have no signal intensity difference compared with cortical gray matter. Fibromatous meningiomas may be more hypointense than the cerebral cortex. Meningiomas are hyperintense on T2-weighted images, and T2-weighted images also show the extent of edema. See the images below.


Multiple meningiomas. A: Sagittal T1-weighted magnetic resonance image (MRI) demonstrates posterior fossa and parietal meningiomas. B: Gadolinium enhancement on sagittal T1-weighted MRI shows intense enhancing of the masses. C: T2-weighted coronal MRI shows stable hypointense appearance of the posterior mass after endovascular embolization.

Malignant and multiple meningiomas. A 47-year-old white male underwent gamma knife surgery due to left convexity meningioma, followed by microsurgical removal of the tumor in 2001. A, B: Four years later, in 2005, MRI showed a stable residual parietal/occipital mass. The left sigmoid sinus is occluded. C, D: One small right frontal meningioma also underwent radiosurgery at the same time. Edema and intense enhancing after gadolinium injection is demonstrated.

On MRI and CT, meningiomas exhibit the same enhancement appearance after the injection of contrast medium. Intense enhancement is seen in 85% of tumors. A ring appearance may represent a capsule.

Meningiomas have a collar of thickened, enhancing tissue that surrounds their dural attachment; this is also known as a dural tail. This sign represents thickened dura, which may be either reactive or neoplastic. A dural tail occurs in approximately 65% of meningiomas and 15% of other peripheral tumors; therefore, it is a good predictor of lesion identity. Although this radiographic feature is not specific for meningiomas, it is highly suggestive of the diagnosis.

Histologic subtypes may have different MRI appearances, but this does not suffice for a histologic diagnosis by using MRI.


Hyperintensity on T2-weighted images indicates soft-tumor consistency and microhypervascularity. This is seen more often in aggressive, angioblastic, or meningothelial tumors. T2-weighted signal intensity is best correlated with both the histology and consistency of the meningioma. Generally, low-intensity portions of the tumor on T2-weighted images indicate a more fibrous and harder character (eg, fibroblastic meningiomas), whereas higher-intensity portions indicate a softer character (eg, angioblastic tumor).[29, 30, 31]

A typical meningioma is a homogeneous, markedly enhancing extra-axial mass. It may show meningeal cysts, ring enhancement, fatty transformation, and en plaque morphology. Malignant meningiomas may invade the calvarium and cerebral parenchyma (1%).

Most meningiomas can be diagnosed by MRI.[17, 18, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41] MRS reveals lactate in embolized areas of the meningioma immediately after embolization. Lipids are not observed before the third day after embolization and are always associated with avascular and soft tissue at the time of surgery.

Gadolinium warning

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Systemic Fibrosis. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.

NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.


In general, the sensitivity and specificity of MRI are high in the diagnosis of meningiomas. MRI has proved to be superior in delineation of the tumor and its relation with surrounding structures. However, MRI is unreliable for recognition of tumor calcification, and acute hemorrhage is often difficult to image with this modality.


False-negative findings of tumor calcium must be considered. Delineation of acute hemorrhage into tumor with conventional sequences is a disadvantage of MRI and may generate false findings.



http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm152672.htm


Ultrasonography

The location of intratumoral hemorrhage, cystic changes inside or outside of the tumor mass, calcifications, invasion of the parenchyma by malignant meningiomas, and lobulated or multilobulated masses is demonstrable only with intraoperative ultrasonography.

Angiography

Although magnetic resonance angiography (MRA and magnetic resonance venography [MRV]) have decreased the role of classical angiography, the latter remains a powerful tool for embolization and planning surgery. Angiography is still indispensable if embolization of the tumor is deemed necessary (see the image below).[39, 42, 43]

A: Noncontrast angio-magnetic resonance image (MRI) on lateral view demonstrates occluded superior sagittal sinus due to meningioma invasion. B: MRI reconstruction shows sagittal venous obstruction and 3-dimensional (3-D) appearance of the tumor.

Meningiomas are supplied by meningeal branches of the internal and external carotid artery (see the following images). Basal meningiomas of the anterior and middle cranial fossa and meningiomas of the wings of the sphenoid bone are commonly supplied by the internal carotid artery. Other supratentorial meningiomas are supplied by the internal and external carotid arteries.

Brain meningioma. Middle fossa meningioma. Internal carotid artery demonstrates considerable supply from petrous branch. The external carotid artery provided the main blood supply to the tumor.


Brain meningioma. Parasellar meningioma. Lateral projection from internal carotid angiography shows multiple opacified tumoral vessels in a radial distribution. Circumferential narrowing of the supraclinoid carotid portion is depicted.

Tumors that arise along the falx, the sphenoidal ridge, and the convexity are supplied by the middle meningeal artery. Falcine meningiomas can be supplied additionally by the anterior meningeal artery. Parasellar and tentorium tumors are supplied by the hypophyseal meningeal artery. Direct meningeal arteries from the cavernous sinus can supply meningiomas of the middle cranial fossa. Intraventricular tumors are supplied by anterior and posterior choroidal arteries. See the images below.

Brain meningioma. Cerebellopontine angle meningioma. Selective angiogram of right occipital artery shows focal hypervascularity through the auricular artery. Early and delayed staining is seen.

Brain meningioma. Cerebellopontine angle meningioma. Right occipital artery embolized with polyvinyl alcohol particles before surgery.


Digital subtraction angiography. A, B: Left external carotid artery shows early and delayed stain of the mass through media meningeal, superficial temporal arteries. C: Occipital artery. D: The branches were embolized before the surgical procedure. The tumor was partially removed due to cranial base involvement.

Embolization may be the only treatment required in older or high-risk patients. Meningeal vessels from the internal carotid artery should supply the tumor. Mass effect should persist after embolization of the middle meningeal artery.

As an alternative to traditional catheter angiography, 3-D CT angiography may depict the relationship between skull base meningiomas and neighboring bony and vascular structures clearly, quickly, and with minimal risk to the patient.


Angiography has a high degree of confidence in recognizing the arterial source of the meningioma. Tumor feeding can be identified with a low rate of false-positive and/or false-negative findings.


Arterial findings have a high sensitivity and specificity in the diagnosis of meningiomas. Angiography shows an arterial map for preoperative embolization with a low false-finding rate.

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http://emedicine.medscape.com/article/341624-overview#a24


Imaging in Chordoma Author

Paule Peretti, MD Neuroradiologist, Radiological Department, Sainte Marguerite Hospital, France

Paule Peretti, MD is a member of the following medical societies: French Society of Radiology

Coauthor(s)

Hervé Brunel, MD Physician, Department of Neuroradiology, Montpellier of Pr Bonafé, France

Guillaume Gorincour, MD Physician, Department of Neuroradiology, University Hospital of Marseilles, France

Overview

Chordomas are tumors originating from embryonic remnants of the primitive notochord. Because chordomas lie in bone, they are usually extradural and induce bone destruction (see the images below).[1, 2] These are rare tumors with an estimated incidence of 0.51 cases per million. Clival chordomas represent less than 0.2% of all intracranial tumors. Although there is no racial predilection for chordomas, the incidence in males is 2-fold greater than in women (2:1), and the tumors are found primarily in adults, occurring rarely in patients younger than 30 years.

Morphology of chordoma. Contrast-enhanced sagittal T1-weighted spin-echo image. Chordoma of the upper part of the clivus with posterior extension to the pontine cistern. The bone appears expanded in this early form.

Differential diagnosis between chordoma and invasive pituitary adenoma. Sagittal contrast-enhanced T1-weighted magnetic resonance image. 6a. Clivus chordoma with posterior extension into the pontine cistern and compression of brainstem. The tumor appears lobulated and enhances heterogeneously, whereas the pituitary gland shows more marked enhancement, suggesting that the tumor does not arise from it. 6b. Invasive pituitary adenoma. The signal of the mass in the sphenoid is not homogeneous. No posterior extension is observed; extension is mostly into the sphenoid sinus. The pituitary gland is not visible.


http://www.sfrnet.org/

The pathophysiology of chordomas as observed on magnetic resonance imaging (MRI) scans, show a signal heterogeneity possibly due to a variety of components, including fluid and gelatinous mucoid substance (associated with recent and old hemorrhage) and necrotic areas within the tumor (see the following images). In some patients, calcification and sequestered bone fragments are seen as well. In addition to conventional chordomas, chondroid chordomas, which are composed of cartilaginous hyaline tissue, have shorter T1- and T2-weighted MRI signals because of low water content.

Chordoma. Coronal T1-weighted spin-echo magnetic resonance image. The high signal is a result of hemorrhage.

Chordoma. Contrast-enhanced sagittal gradient-echo T1-weighted magnetic resonance image demonstrates heterogeneous, lobulated tumor.

Differentiating chordomas from chondrosarcomas using both radiologic and histologic criteria can be difficult. Immunohistochemical studies using cytokeratin antibodies and epithelial membrane antigen (negative in chondrosarcomas, positive in chordomas) can make the distinction. Chondroid forms can represent low-grade chondrosarcomas, which also is controversial. Metastatic epithelial neoplasms should be considered in the differential diagnosis as well.

Metastatic spread of chordomas is observed in 7-14% of patients with lymph node, pulmonary, bone, cerebral, or abdominal visceral involvement, predominantly from massive tumors. In true malignant forms of chordomas there occasionally are areas of typical chordoma, as well as undifferentiated areas, most often suggestive of fibrosarcoma; the prognosis is poor.


MRI and computed tomography (CT) scanning have complementary roles in the evaluation of chordoma.[3] CT scanning is needed to assess the degree of bone involvement or destruction and to detect patterns of calcification within the lesion, whereas MRI provides excellent 3-dimensional (3-D) analysis of the posterior fossa (especially the brainstem), sella turcica, cavernous sinuses, and middle cranial fossa.[4] However, MRI does not depict calcifications and the precise involvement of skull base osteolysis as well as CT scanning, especially for skull base foramina (see the image below).


Computed tomography scan of 2 patients with chordoma. Coronal plane (left): midline tumor with lateral extension, skull base destruction, and carotid canal lysis on the right. Note the calcification or osseous debris. Axial plane (right): lysis of clivus (arrow).

Similarly, in the spine, MRI and CT scanning are complementary. In addition, it is much easier and more time efficient to survey large areas of the spinal axis and roots (or indeed, the entire spinal axis) with MRI than with CT scanning.

Radiography

Chordomas have 4 pathognomonic characteristics on plain film evaluation: expansion of the bone, rarefaction, trabeculation, and calcification, as seen in the image below. The usual radiographic pattern is lytic, with frequent calcification or sequestered bone fragments.

Sacrococcygeal chordoma. Plain radiograph of the pelvis showing expansion of the sacrum, bone rarefaction, and large mass of soft tissue with some trabeculations.

However, radiographs are neither specific nor sensitive for detecting chordoma; for intracranial chordomas, plain films are no longer used. In addition, although plain films are often the first examination for sacrococcygeal and spinal chordomas, CT scanning and MRI are necessary for the diagnosis. Finally, even if a destructive clival lesion is observed on plain films, the size of the tumor may be grossly underestimated not only because portions of a chordoma may have little or no calcification present but also because the soft-tissue component is not visualized.

Computed Tomography

CT scanning is essential, highly sensitive, and accurate for evaluating bony integrity, bone destruction, and calcifications or bone fragments within the lesion. On CT scans, the chordomas appear homogeneous, with a density comparable to that of muscles. The tumor appearance on contrast enhancement is heterogeneous. Calcification is found in less than one half of patients, and differentiation from sequestered bone fragments is difficult.[5, 6, 7]


Intracranial chordomas

The most characteristic appearance of an intracranial chordoma is of a centrally located soft-tissue mass arising from the clivus and causing adjacent bone destruction.[8] Calcification is common, and areas of low attenuation within the soft-tissue mass — representing the myxoid and gelatinous material found on pathologic examination — are occasionally found on CT scans. CT scanning reliably demonstrates petrous apex involvement and lysis of the skull base foramina.

Sacrococcygeal chordomas

Chordomas are often massive, well-delineated tumors that shift the fatty tissue of the pelvis and involve bone structures and the epidural area. Peripheral sclerosis may be observed in approximately 50% of patients, and frequently, a discrepancy is found between a large soft-tissue component and the area of bone involvement. In addition, regional lymph nodes are usually invaded.

The most reliable sign of sacral chordomas is the destruction of several sacral vertebrae associated with a tissue mass anterior to the sacrum. However, the association of osteolytic lesions and soft masses involving the discs and the vertebrae suggests other diagnoses, such as neurofibromas, lymphomas, metastases, and plasmacytomas.

Spinal chordomas

Infrequently, chordomas arise in the mobile (ie, cervical, thoracic, lumbar) spine (15%). [9] The cervical spine is the most common site for these tumors, with a predominance in the C2 vertebra; the thoracic[10] and lumbar areas of the spine are involved less frequently.

Initially, the presentation of chordoma on CT scan is of bone destruction centered in the vertebral body, with an associated, anteriorly or laterally situated, paraspinal soft-tissue mass that may contain calcification. Following vertebral body involvement, the pedicles, laminae, and spinal process then become involved as well; however, adjacent intervertebral disc spaces are usually spared.

Chordomas that occur in vertebrae above the sacrum appear to originate in a single vertebral body, initially producing lytic changes and ultimately resulting in vertebral collapse. Occasionally, contiguous vertebrae are involved, with sparing of the discs.

Epidural extension of the tumor is usual. Although both CT scanning and MRI can define the extravertebral extension of the tumor (the main bulk of the tumor is usually anterior to the spine), MRI is the best technique to evaluate extension of the tumor.

CT scans depicting chordomas are provided below.


CT scans depicting chordomas are provided below.

Computed tomography scan of 2 patients with chordoma. Coronal plane (left): midline tumor with lateral extension, skull base destruction, and carotid canal lysis on the right. Note the calcification or osseous debris. Axial plane (right): lysis of clivus (arrow).

Computed tomography scan. Note the calcification. Image courtesy of Editions Masson, Paris, 2002.

Computed tomography scan. Recurrence of a sacrococcygeal chordoma. Note tumoral infiltration of gluteal muscles displacing the rectum anteriorly. Image courtesy of Editions Masson, Paris, 2002.

Computed tomography scan of sacrococcygeal chordoma. Note the sacral lysis with trabeculations.


Computed tomography scan of sacrococcygeal chordoma. Note the tumoral calcification in this huge pelvic tumor.

Computed tomography scan of sacrococcygeal chordoma. Note the right sacroiliac joint lysis.


Among imaging methods that contribute to the diagnosis, MRI is particularly reliable; this modality is highly accurate in assessing the soft-tissue extent of chordomas and in evaluating involvement of adjacent tissues.[11]

T1- and T2-weighted sequences are needed before and after gadolinium injection. The best tool for demonstrating tumoral site and extension and for selecting the surgical approach is 3-dimensional (3-D) MRI.[12] Indeed, for clival chordomas, 3-D gradient-echo T1-weighted sequences are helpful, because they visualize the tumor in 3 planes within a short time and with a good analysis of tumoral signal.[13]

Evaluation of the precise extent of the tumor and the degree of involvement of adjacent tissues is best performed by MRI. These attributes are relevant to diagnosis and choice of treatment (biopsy or surgical and/or radiosurgical treatment).

Intracranial chordomas

MRI specifically shows tumor extension into critical structures, such as the cavernous sinuses, the circle of Willis, and the brainstem.[4, 14] Chordomas originate from the midline, with varying degrees of lateral extension. This characteristic predilection for the midline may aid in the differential diagnosis. Morphology and signal of the tumor are other elements in diagnosis.


Several authors have reported atypical sites of chordoma. These lesions probably originate from ectopic notochord, and their prognosis differs from that of typical chordomas. The extension of chordomas is primarily posterior, with involvement of the pontine cistern and, occasionally, of the premedullary cistern. Anterior extension, which is also frequent, primarily occurs in massive tumors with significant destruction of the skull base. [15] This can be anterosuperior to the sella turcica, displacing the pituitary gland, or anteroinferior to the nasopharynx or middle cranial fossa. Overall, extension is primarily along the anteroposterior axis rather than laterally. However, some limited lateral extension commonly does occur into the cavernous sinuses, affecting treatment. It is observed in as many as 75% of patients.

Chordomas can also involve the petrous apex. However, contrary to intrinsic petrous apex tumors (ie, rhabdomyosarcomas, metastases, plasmacytomas, cholesterol granulomas, epidermoid cysts), they originate from the midline.

The expansion of the bone in the early stage indicates that the tumor arises from bone and not from adjacent structures. This feature disappears as the tumor enlarges further. Skull base chordomas are well delineated at the outset, as they displace adjacent structures; however, more advanced tumors become invasive and have a pseudomalignant appearance with bone erosion and soft-tissue invasion.

Most chordomas are isointense or demonstrate low signal on T1-weighted images. Some tumors an also demonstrate high signal, which is related on histologic examination to hemorrhage and mucinous collections. Tumoral signal on T1-weighted sequences is thus not entirely reliable. Most chordomas exhibit high signal on T2-weighted images, which is also nonspecific.

Following gadolinium injection, chordomas usually show lobulated areas with a honeycomb appearance corresponding to low signal areas within the tumor.[16] Chordoma signal is described as heterogeneous after gadolinium injection and on T1- and T2-weighted images. The pattern of contrast enhancement can be related to the pathologic features of the tumors, which are organized in lobules with mucinous and gelatinous contents. This may be a useful diagnostic sign. The borders of the tumor are better delineated with gadolinium injection.[16]

Sacrococcygeal chordomas

MRI provides detailed multiplane information, with excellent contrast of the tumor and its surrounding anatomic structures. On MRI, sacrococcygeal chordomas are lobulated tumors, typically with low to intermediate signal intensity on T1-weighted images and heterogeneous high signal intensity on T2-weighted images. The pattern of gadolinium enhancement is the same as for clival chordomas.


Tumoral extension is important to ascertain for preoperative planning and is observed as follows:

Proximal extension - Bone and sacral canal Distal-lateral extension - Gluteus maximus, hamstrings, and sciatic nerve and notch

Anterior extension - Retroperitoneal lymph nodes and rectum

Posterior extension - Subcutaneous fat

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or magnetic resonance angiography scans.

NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see FDA Information on Gadolinium-Based Contrast Agents or Medscape.

Other neoplasms can be difficult to differentiate from chordomas.[17] A few of these are discussed below.

Chondromas

Chondromas may have the same radiologic appearance as chordomas (see the image below). They originate from embryonic remnants of the primitive cartilage and tend to arise from and extend more laterally into the sellar and cerebellopontine-angle regions.

Topography of chordoma. Differential diagnosis between chordoma and chondroma. 4a. Coronal contrast-enhanced T1-weighted spin-echo image. Clival chordoma with a lateral extension to the left cavernous sinus. The tumor is median with a lateral extension. 4b. Coronal contrast-enhanced T1-weighted gradient-echo image of a laterosellar chondroma. This image demonstrates the strictly lateral localization of the tumor.





Craniopharyngiomas

Craniopharyngiomas have a different topography in addition to a relatively characteristic signal. The tumors are suprasellar, sellar, or infrasellar and are rarely at the level of the nasopharynx. Generally, the site is more anterior and superior, and extension is almost always posterosuperior (interpeduncular cistern).

Pituitary adenomas

Invasive pituitary adenomas usually affect the sphenoid sinus (see the following image), although in some patients they are posterior, in which case the hypophysis is not visible. Usually, the pontine cistern is not involved. Of course, clinical and biologic data are the primary indications of pituitary origin, except in nonsecreting adenomas. See the image below.

Differential diagnosis between chordoma and invasive pituitary adenoma. Sagittal contrast-enhanced T1-weighted magnetic resonance image. 6a. Clivus chordoma with posterior extension into the pontine cistern and compression of brainstem. The tumor appears lobulated and enhances heterogeneously, whereas the pituitary gland shows more marked enhancement, suggesting that the tumor does not arise from it. 6b. Invasive pituitary adenoma. The signal of the mass in the sphenoid is not homogeneous. No posterior extension is observed; extension is mostly into the sphenoid sinus. The pituitary gland is not visible.

Clivus meningiomas

Clivus meningiomas are differentiated easily from chordomas. They have a large dural attachment and do not appear similar to bone tumors. Homogeneity of their signal is an additional element.

Lymphoma

Aside from clinical data, few criteria exist for diagnosing lymphoma of the skull base. Similarly, bone metastases can be found in any part of the skull base with extensive osteolysis and a rapid course. Because skull base metastases are relatively infrequent in the absence of a primary neoplasm, the differential diagnosis is easier. Neither type of tumor is frequent. Nasopharyngeal malignancies typically extend more anteriorly.


MRI studies depicting chordomas are provided below.

Morphology of chordoma. Contrast-enhanced sagittal T1-weighted spin-echo image. Chordoma of the upper part of the clivus with posterior extension to the pontine cistern. The bone appears expanded in this early form.

Recurrence of clival chordoma following surgery. Contrast-enhanced sagittal T1-weighted gradient-echo image showing brainstem and foramen magnum invasion.


Chordoma. Coronal T1-weighted spin-echo magnetic resonance image. The high signal is a result of hemorrhage.

Chordoma. Contrast-enhanced sagittal gradient-echo T1-weighted magnetic resonance image demonstrates heterogeneous, lobulated tumor.

Sagittal contrast-enhanced T1-weighted magnetic resonance image. Note the heterogeneous gadolinium enhancement (same patient as in previous image).


Sagittal T2-weighted magnetic resonance image. The tumor appears lobulated and shows high signal (same patient as in previous image). Image courtesy of Editions Masson, Paris, 2002.

Sacrococcygeal chordoma. Sagittal T1-weighted magnetic resonance image showing a huge, well-delineated tumoral mass invading the sacral canal, extending into the pelvis, and shifting the fat, uterus, bladder, and rectum. Image courtesy of Editions Masson, Paris, 2002.

Sagittal contrast-enhanced T1-weighted magnetic resonance image. Note the lobulated heterogeneous contrast enhancement (same patient as in previous image). Image courtesy of Editions Masson, Paris, 2002.


Coronal T1-weighted magnetic resonance image (same patient as in previous image). Image courtesy of Editions Masson, Paris, 2002.

Coronal contrast-enhanced T1-weighted magnetic resonance image (same patient as in previous image). Image courtesy of Editions Masson, Paris, 2002.

Coronal T1-weighted magnetic resonance image. Tumoral infiltration of the thigh. Image courtesy of Editions Masson, Paris, 2002.

Axial T1-weighted magnetic resonance image (same patient as in previous image). Image courtesy of Editions Masson, Paris, 2002.



Imaging in Cranial Nerve Schwannoma Author

Mahesh Jayaraman, MD Interventional Neuroradiology Fellow, Department of Radiology, Stanford University Medical Center

Mahesh Jayaraman, MD is a member of the following medical societies: Radiological Society of North America

Coauthor(s)

Lawrence M Davis, MD Assistant Professor of Diagnostic Imaging (Clinical), Department of Diagnostic Imaging, Warren Alpert Medical School at Brown University

Lawrence M Davis, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Neuroradiology, Radiological Society of North America, and Rhode Island Medical Society

Overview

Before the advent of magnetic resonance imaging (MRI), imaging of the cranial nerves (CNs) was difficult, and mass lesions arising from these nerves was often indirectly detected only by looking at bony changes in the skull base foramen or by using invasive techniques such as cisternography and angiography. Current imaging techniques provide noninvasive highly detailed imaging of most of the CNs and the lesions (eg, schwannomas) that affect them. [1, 2,

3, 4]

Patients with CN schwannomas can present with loss of function of the affected nerve, but they can also be asymptomatic. In these latter patients, the lesion may be incidentally discovered on computed tomography (CT) scans or MRIs obtained for reasons other than the evaluation of a schwannoma.

CN schwannomas are usually isolated lesions, except when they are associated with neurofibromatosis type 2.[5] NF2 is also called the multiple inherited schwannomas, meningiomas, and ependymomas (MISME) syndrome. NF2 is characterized by bilateral vestibular schwannomas. Schwannomas of the other CNs occur more frequently in NF2, and the presence of one of the rare CN schwannomas should suggest the possibility of NF2. Meningiomas and intramedullary ependymomas of the spinal cord also occur in NF2.

Schwannomas arise from the nerve sheath and consist of Schwann cells in a collagenous matrix.[6] These lesions account for 6-8% of intracranial neoplasm; vestibular schwannomas are the most common CN schwannomas, followed by trigeminal and facial schwannomas and then glossopharyngeal, vagus, and spinal accessory nerve schwannomas. A study of patients undergoing MRI for indications other than the evaluation of schwannoma revealed an estimated prevalence of 0.07%.

Varying growth patterns in schwannomas are described as Antoni type A neurilemoma and type B neurilemoma. Although type A tissue has elongated spindle cells arranged in irregular streams and is compact in nature, type B tissue has a looser organization, often with cystic






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spaces intermixed within the tissue. The cystic spaces can result in high signal intensity on T2-weighted MRIs.

Schwannomas involving the oculomotor, trochlear, abducens, and hypoglossal nerves are rare. See the images below.

Contrast-enhanced T1-weighted magnetic resonance image at the level of the internal auditory canal shows a strongly enhancing cisternal vestibular schwannoma (arrow) that compresses the adjacent pons and cerebellum and distorts the fourth ventricle.

Contrast-enhanced T1-weighted axial magnetic resonance image through the internal auditory canal shows a heterogeneously enhancing intracanalicular-cisternal vestibular schwannoma (white arrow). Anterior to the schwannoma, a tumor-related cyst is depicted (black arrow).

Intracanalicular vestibular schwannoma. Axial constructive interference in the steady state (CISS) magnetic resonance image shows a 3-mm mass (arrow) in the internal auditory canal as a filling defect in the bright cerebrospinal fluid.

Vestibular schwannoma. Axial contrast-enhanced T1-weighted magnetic resonance image confirms an intracanalicular mass (arrow).


Bilateral vestibular schwannomas. Axial contrast-enhanced T1-weighted magnetic resonance image reveals bilateral vestibular schwannomas (arrows), which are diagnostic of neurofibromatosis type 2.

Anatomy

Motor neurons of the oculomotor nerve (ie, CN III) leave the midbrain at the level of the tegmentum and emerge in the interpeduncular cistern. Here, it passes between the posterior cerebral artery (PCA) above) and the superior cerebellar artery (SCA) below, and it turns anteriorly to enter the cavernous sinus. In the cavernous sinus, the oculomotor nerve courses along the lateral wall; it is the most superior of all the nerves in the sinus. The nerve enters the orbit via the superior orbital fissure and then splits into superior and inferior divisions.

From the trochlear nucleus in the midbrain, fibers of the trochlear nerve (ie, CN IV) cross the midline dorsal to the cerebral aqueduct and exit the midbrain dorsally. From here, the fibers run around the midbrain to the ventral surface. Like the oculomotor nerve, the trochlear nerve also courses between the PCA and SCA and along the lateral wall of the cavernous sinus. It enters the orbit at the superior orbital fissure.

The trigeminal nerve (ie, CN V) exits the brainstem at the level of the mid pons, and its 3 divisions—the ophthalmic (CN V1), maxillary (CN V2), and mandibular (CN V3) branches—together proceed anteriorly toward the trigeminal ganglion in the Meckel cave, as shown in the image below. From here, the mandibular division exits inferiorly via the foramen ovale. The maxillary and ophthalmic divisions continue anteriorly along the lateral aspect of the cavernous sinus. Eventually, the ophthalmic division enters the orbit via the superior orbital fissure, while the maxillary division exits the cranial vault through the foramen rotundum.

Lymphoma of the Meckel cave. Coronal contrast-enhanced T1-weighted magnetic resonance image shows an enhancing mass in the Meckel cave on the right (white arrow). The left Meckel cave is without tumor (black arrow). Lymphomatous meningitis can mimic a cranial nerve schwannoma.


The abducens nerve (ie, CN VI) exits the brainstem ventrally at the level of the junction of the pons and medullary pyramid and courses anterolaterally toward the dorsum sellae, passing over the petrous apex where it makes a sharp turn to enter the cavernous sinus. In the sinus, the abducens nerve is medial to CN IV, CN V1, and CN V2. Along with the oculomotor and trochlear nerves, the abducens nerve also enters the orbit via the superior orbital fissure, then enters the deep surface of the lateral rectus muscle.

The paths of the facial nerve (ie, CN VII) and vestibular nerve (ie, CN VIII) are intimately associated. They exit the brainstem at the pontomedullary junction, with the facial nerve slightly medial to the vestibular nerve. From there, they enter the internal auditory canal (IAC). Once in the IAC, the facial nerve courses in the superior-anterior quadrant of the canal, while the vestibular division of the vestibular nerve courses in the posterior superior and inferior quadrants, and the cochlear division courses in the inferior-posterior quadrant. CN VIII then enters the labyrinth. (The mnemonic for this arrangement is "Seven-Up and Coke [ie, cochlear] down.")

The facial nerve enters the labyrinth (labyrinthine segment), courses anteriorly in the temporal bone to the geniculate ganglion, turns posteriorly to pass beneath the lateral semicircular canal (tympanic segment) and then inferiorly to course through the mastoid (vertical segment), and exits the temporal bone via the stylomastoid foramen. Finally, the facial nerve courses within the parotid gland (parotid segment) before branching.

The glossopharyngeal (ie, CN IX), vagus (ie, CN X), and accessory (ie, CN XI) nerves emerge cranial to caudal, in that order, from the ventral medulla, lateral to the medullary olive. From there, they course toward the jugular foramen and exit the skull base at the jugular foramen. The glossopharyngeal nerve is located in the pars nervosa of the jugular foramen, and the vagus and accessory nerves are located within the more posterior pars vascularis.

The hypoglossal nerve (CN XII) is formed by the fusion of multiple rootlets that emerge from the ventrolateral sulcus between the medullary olive and pyramid. The nerve exits the cranial vault via the hypoglossal canal, then lies medial to CN IX, CN X, and CN XI.


MRI with the use of gadolinium-based contrast medium is the technique of choice for imaging the CNs.[1, 4, 7] MRI provides the highest degree of soft-tissue resolution, can provide images in multiple planes, and is not encumbered by bone artifact from the skull base. CT scanning is ideal for evaluating the secondary effects on the neural foramen.[2]


CT evaluation is limited primarily to the assessment of bony changes in the skull base. Artifact from the skull base limits the soft-tissue resolution of CT scans, particularly in small lesions.[2] Plain radiography has no role in the evaluation of the lesions.


Aside from a patient's claustrophobia or incompatible hardware, the only significant imaging drawback of MRI is that CT scanning can be more sensitive in depicting adjacent bone destruction.[2]

Differentials and other problems to be considered

The differential diagnosis varies with the location, but meningiomas can occur in similar regions and have similar imaging appearances as schwannomas. The differing growth patterns, as well as the dural tail and associated hyperostosis that can be seen with meningiomas, are often helpful differentiating factors. See the image below.

Cerebellopontine angle meningioma. Axial contrast-enhanced T1-weighted magnetic resonance image through the cerebellopontine angle shows a large cisternal mass. The intracanalicular component (white arrow) can mimic a vestibular schwannoma, although the broad-based dural attachment (red arrows) is more consistent with a meningioma.

Cerebrospinal fluid (CSF) spread of metastatic disease or lymphoma can appear as a focal CN mass. In patients with carcinomatous meningitis and lymphoma, focal metastatic masses can involve the cranial nerves and mimic a schwannoma. See the images below.

Lymphoma of the Meckel cave. Coronal contrast-enhanced T1-weighted magnetic resonance image shows an enhancing mass in the Meckel cave on the right (white arrow). The left Meckel cave is without tumor (black arrow). Lymphomatous meningitis can mimic a cranial nerve schwannoma.





Carcinomatous meningitis. Coronal contrast-enhanced T1-weighted magnetic resonance image reveals bilateral cranial nerve V (white arrows) and cranial nerve VIII masses (red arrows). The patient had lung cancer with cerebrospinal fluid spread manifesting as multiple cranial nerve masses.

Neuritis (ie, inflammation of a nerve) can be confused with a mass. See the images below.

Facial neuritis. Axial contrast-enhanced T1-weighted magnetic resonance image shows enhancement of the distal intracanalicular, labyrinthine, and geniculate, segments (arrow) of cranial nerve VII.

Facial neuritis. Coronal contrast-enhanced T1-weighted magnetic resonance image shows enhancement of the labyrinthine and tympanic segments of cranial nerve VII (arrow).


NF2 is one of the phacomatoses characterized by multiple intracranial schwannomas, meningiomas, and ependymomas. Bilateral vestibular schwannomas are diagnostic of this entity, but patients can have schwannomas involving any CN (CN III-XIII). See the image below.

Bilateral vestibular schwannomas. Axial contrast-enhanced T1-weighted magnetic resonance image reveals bilateral vestibular schwannomas (arrows), which are diagnostic of neurofibromatosis type 2.

Other conditions to be considered include glomus tumors of the head and Neck and NF1.

Radiologic intervention

Stereotactic radiosurgery (SRT) (ie, gamma knife radiosurgery) largely has replaced surgical resection for the treatment of vestibular schwannomas, particularly when the lesions do not compress the brainstem. Lesions should be smaller than 3 cm. Studies have demonstrated rates of tumor control (ie, lesion stabilizes or shrinks) of greater than 95% and a rate of hearing preservation of approximately 70%. Although less well studied, other CN schwannomas also can be treated with radiosurgery.[8, 9, 10, 11]

Nishioka et al demonstrated stereotactic radiotherapy is an effective alternative to surgical resection for patients with nonacoustic intracranial nerve schwannomas not only for long-term local tumor control but also preservation of neurofunction. [12] Following stereotactic radiotherapy, tumor size decreased in 3 patients, remained stable in 13, and increased in 1. Neurologic symptoms improved in 8 patients and remained unchanged in 9 patients. In 1 patient, an increase in tumor size necessitated microsurgical resection. No worsening of neurologic symptoms or development of new cranial nerve deficits was reported.[12]

Special concerns

Failure to perform MRI when CN tumors are suggested is a concern. In particular, CT scans of the brain are inadequate for evaluating CNs, and the reliance of negative CT findings to exclude a CN lesion may lead to liability.

Radiography

No role exists for plain radiographic evaluation of schwannomas. Findings on conventional radiographs are nonspecific, and typically, lesions are visualized on plain radiographs only when they are large.





Computed Tomography

On nonenhanced CT scans, most schwannomas are isoattenuating relative to brain parenchyma. Calcification or areas of hemorrhage are rare. On contrast-enhanced CT scans, the enhancement pattern is typically homogeneous.[2]

Bone-window images can demonstrate remodeling of the adjacent skull base, such as expansion of the IAC by vestibular schwannomas and expansion of the facial canal by facial schwannomas. Expansion of the jugular foramen by CN IX, CN X, or CN XI schwannomas can also be seen. See the image below.

Computed tomography scan through the skull base shows soft-tissue expansion of the facial nerve canal in the petrous bone (arrow).

Thin-collimation CT imaging of the skull base can be helpful in evaluating bone destruction. This finding is useful in differentiating jugular foramen schwannomas from paragangliomas. See the image below.

Glomus jugulare. Axial computed tomography scan obtained through the skull base shows extensive bone destruction (arrows), unlike the smooth expansion seen with schwannomas.


With CT scanning, large lesions can be diagnosed with a high degree of confidence. However, distinguishing a schwannoma from a meningioma may not be possible by using CT scanning. A small lesion that affects a CN cannot be confidently excluded.



CT findings can be false-negative in small lesions. Occasionally, a false-positive diagnosis occurs because a streak artifact in the cerebellopontine angle cistern mimics a lesion.


Similar to CT imaging, MRI tends to depict schwannomas as homogeneous masses.[1, 7]

Schwannomas are typically isointense or slightly hypointense relative to gray matter on T1-weighted images and slightly hypointense to CSF on T2-weighted images. Gadolinium enhancement is typically homogeneous, although larger schwannomas can show areas of cystic degeneration and heterogeneous signal intensity; these findings are based on increased numbers of areas with Antoni type B histologic features.

High-resolution, thin-section, heavily T2-weighted, 3-dimensional (3-D) sequences have been used to look for acoustic neuromas. On images obtained with these sequences, individual nerves in the cistern and internal auditory canal (IAC) can be visualized as linear filling defects in the bright CSF. Small masses can be identified without the use of an intravenously administered contrast agent. See the image below.


Vestibular schwannomas are the most common CN schwannomas. Typically, the masses are located in the cerebellopontine angle (CPA) and centered at the porus, with extension into the IAC. Their appearance has been described as that of a comet tail or ice cream cone, with the cone as the


intracanalicular extension and the ice cream as the cisternal component. The long axis of the tumors is parallel to the petrous surface. See the images below.

Contrast-enhanced T1-weighted magnetic resonance image at the level of the internal auditory canal shows a strongly enhancing cisternal vestibular schwannoma (arrow) that compresses the adjacent pons and cerebellum and distorts the fourth ventricle.

Contrast-enhanced T1-weighted axial magnetic resonance image through the internal auditory canal shows a heterogeneously enhancing intracanalicular-cisternal vestibular schwannoma (white arrow). Anterior to the schwannoma, a tumor-related cyst is depicted (black arrow).



Vestibular schwannoma. Axial contrast-enhanced T1-weighted magnetic resonance image confirms an intracanalicular mass (arrow).

Occasionally, tumors can be entirely intracanicular, in which case the primary differential diagnosis is a meningioma of the CPA. Unlike vestibular schwannomas, meningiomas tend to form obtuse angles with the adjacent petrous bone, are typically hemispheric, and often extend into the middle fossa as a result of herniation. Meningiomas can be differentiated by their broad base of attachment along the petrous bone and by the presence of a dural tail. Meningiomas uncommonly extend into the IAC.[7] See the image below.

Cerebellopontine angle meningioma. Axial contrast-enhanced T1-weighted magnetic resonance image through the cerebellopontine angle shows a large cisternal mass. The intracanalicular component (white arrow) can mimic a vestibular schwannoma, although the broad-based dural attachment (red arrows) is more consistent with a meningioma.

Schwannomas of the facial nerve can occur along any segment, but they frequently involve the geniculate ganglion and extend proximally or distally from there. MRI and CT imaging characteristics are similar to those of vestibular schwannomas. The location of the mass results in variable growth patterns. In the IAC, facial schwannomas are indistinguishable from vestibular lesions. When facial schwannomas cross the petrous bone to involve both the middle and posterior fossa, they cross in the mid portion of the petrous bone. In contrast, trigeminal schwannomas cross near the petrous apex. Lesions in the geniculate ganglion can be mistaken for temporal lobe lesions, and imaging in the coronal plane is useful in evaluating the lesions. See the images below.


Facial schwannoma. Axial T1-weighted magnetic resonance image at the level of the internal auditory canal shows a soft-tissue mass (arrow) along the course of the tympanic segment of the facial nerve.

Facial schwannoma. Coronal contrast-enhanced T1-weighted magnetic resonance image shows a schwannoma (arrow) involving the mastoid segment of cranial nerve VII.

Thompson et al elucidated the appearance of the schwannoma on MRIs and demonstrated that enhanced MRI is the imaging modality of choice for facial nerve schwannomas. [13] All lesions in their study involved 2 or more contiguous segments of the facial nerve, with 28 (93%) involving 3 or more segments. The median number of segments involved per lesion was 4, with a mean of 3.83. Geniculate involvement was most common, present in 29 patients (97%). CPA and IAC involvement was significantly related to sensorineural hearing loss (SNHL).[13] Seventeen patients (57%) presented with facial nerve dysfunction, which manifested in 12 patients as facial nerve weakness or paralysis and in 8 patients as involuntary movements of the facial musculature.[13]

Trigeminal schwannomas can arise in the Meckel cave or in the cistern along the course of the nerve.[14] Extension and expansion of the foramen rotundum or ovale is common, and the masses can have a bilobed appearance. Tumors can also grow posteriorly to involve the posterior fossa, or they can grow anteriorly into the cavernous sinus. Trigeminal schwannomas tend to have a more cystic component than other schwannomas. See the images below.


Trigeminal schwannoma. Coronal T2-weighted magnetic resonance image shows a hyperintense mass in the right cavernous sinus (arrow).

Trigeminal schwannoma. Axial contrast-enhanced T1-weighted magnetic resonance image at the level of the mid pons shows a strongly enhancing mass involving the left cranial nerve V in the cistern (black arrow) and Meckel cave (white arrow).

Trigeminal schwannoma. Axial constructive interference in the steady state (CISS) magnetic resonance image shows a mass in the region of the cisternal segment of the right cranial nerve V (white arrow). The left cranial nerve V without tumor (black arrow) is also depicted.


Trigeminal schwannoma. Coronal contrast-enhanced T1-weighted magnetic resonance image shows the mass arising from the cisternal segment of the right cranial nerve V. The left cranial nerve V (without tumor) is also shown (arrow).

Glossopharyngeal, vagus, or accessory nerve schwannomas are rare and difficult to distinguish from one another. The tumors are classified on the basis of their growth patterns: Type A lesions grow predominantly intracranially, type B lesions grow predominantly at the jugular foramen, and type C lesions grow predominantly extracranially. CT scan and MRI characteristics are similar to those of other schwannomas. In contrast to the more common paragangliomas in this region, schwannomas expand but do not infiltrate the adjacent bone. Unlike paragangliomas, which infiltrate and erode adjacent bone, schwannomas smoothly expand the bone and leave an intact cortical margin. See the images below.

Glossopharyngeal schwannoma. Axial contrast-enhanced T1-weighted magnetic resonance image shows a large extra-axial mass that compresses the brainstem (black arrows) and extends into the skull base (white arrows).


Glossopharyngeal schwannoma. Coronal contrast-enhanced T1-weighted magnetic resonance image shows a mass (arrows) extending through the skull base via the jugular foramen.

Hypoglossal schwannomas have growth patterns and imaging characteristics similar to those of jugular foramen schwannomas. When large enough, the tumors can erode the hypoglossal canal to such an extent that their differentiation from jugular foramen schwannomas can be difficult.[15]

Schwannomas of the abducens nerve (ie, CN VI) are rare. They are reported to occur in the prepontine cistern, with a heterogeneous appearance on CT scans and MRIs and extension into the adjacent cavernous sinus. As with other schwannomas, meningioma is the primary differential diagnosis, and the presence of areas of cystic change (which have high signal intensity on T2-weighted images) can suggest the likelihood of schwannoma instead of meningioma. Similarly, CN IV schwannomas are rare. See the image below.

Cranial nerve IV schwannoma. Axial and coronal contrast-enhanced T1-weighted magnetic resonance images demonstrate a small mass (arrows) involving the cisternal segment of cranial nerve IV adjacent to the midbrain. Courtesy of Glenn A Tung, MD, Brown Medical School.

Schwannomas of the oculomotor nerve are reported in the literature, but they are exceedingly rare. The tumors can present as masses in the suprasellar cistern, and they can be difficult to distinguish from meningiomas in this region.

Gadolinium warning

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Systemic Fibrosis. The disease has occurred in patients with



moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.



A diagnosis of a CN mass can be made with a high degree of confidence by using MRI.


False-positive findings occur primarily in the jugular fossa, where slow flow in the jugular bulb can mimic a mass. A false-negative diagnosis can occur if imaging is inadequate—for example, if the image sections are too thick or if fat suppression is not used in evaluating the skull base.

Angiography

Angiography is not used as a diagnostic modality for schwannomas. However, when studied with angiography, schwannomas typically appear hypovascular; this finding distinguishes them from paragangliomas when the lesion is in the jugular fossa. See the images below.

Glossopharyngeal schwannoma. Digital subtraction angiogram obtained with an ascending pharyngeal arterial injection reveals a moderately hypervascular schwannoma (arrows), which is atypical for schwannomas.



http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm152672.htm

Glomus jugulare. Digital subtraction angiogram shows a markedly hypervascular mass (arrow).



Craniopharyngioma Imaging Author Jeffrey R Wasserman, DO Diagnostic Radiologist, Manatee Memorial Hospital and Lakewood Ranch Medical

Center

Jeffrey R Wasserman, DO is a member of the following medical societies: American Medical Association

Coauthor(s) Robert A Koenigsberg, DO, MSc, FAOCR Professor, Director of Neuroradiology, Program Director, Diagnostic

Radiology and Neuroradiology Training Programs, Department of Radiology, Hahnemann University Hospital, Drexel University College of Medicine

Robert A Koenigsberg, DO, MSc, FAOCR is a member of the following medical societies: American Osteopathic Association, American Society of Neuroradiology, Radiological Society of North America, and Society of NeuroInterventional Surgery

Overview

Craniopharyngioma is a histologically benign, extra-axial, slow-growing tumor that predominantly involves the sella and suprasellar space (see the images below).

Contrast-enhanced T1-weighted image demonstrates a complex cystic mass (arrow) in the suprasellar space.


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Axial contrast-enhanced CT scan in a 65-year-old man demonstrates a large, calcified suprasellar mass with anterior displacement of the A1 segment of the anterior cerebral arteries (yellow arrows). The anterior communicating artery is not well depicted.

Contrast-enhanced T1-weighted image in a 66-year-old woman (same patient as in following image) obtained in a slightly lateral parasagittal plane demonstrates irregular enhancement of the solid components (arrow) and the outer rim of the tumor, which has a predominantly cystic composition.

Sagittal nonenhanced T1-weighted image demonstrates a heterogeneous, cystic mass (arrows) in the suprasellar space (same patient as in previous image).

Despite its histologic appearance, craniopharyngiomas occasionally behave like malignant tumors. They can metastasize, and patients can have severe symptoms that usually require surgery and/or radiation therapy (with intracystic chemotherapy in some pediatric patients). Recurrences, both local and along surgical tracts, have been reported, as has meningeal seeding. Characteristic radiographic findings help in differentiating craniopharyngiomas


from other tumors that can occur in the same anatomic region. Zenker first described craniopharyngioma in 1857.[1, 2, 3, 4, 5]


CT and MRI are the complementary examinations of choice. Today, the best imaging tool is MRI, both with and without contrast enhancement.

CT can clearly demonstrate the characteristic calcifications and size of the tumor, whereas MRI exquisitely demonstrates the size and extent of the tumor and involvement of the third ventricle. MRI results can confirm cystic features of the tumor. Sequences such as fluid-attenuated inversion recovery (FLAIR), gradient-echo (GRE) imaging, and diffusion-weighted imaging, as well as MR spectroscopy, can be used to make a confident and correct diagnosis.

Plain radiography may show abnormalities; however, CT or MRI is still needed regardless of the plain radiographic findings. CT and MRI have supplanted angiography as the primary diagnostic modality; today, magnetic resonance angiography (MRA) or CT angiography (CTA) may be helpful in differentiating the tumor from an aneurysm of the anterior communicating artery.

In the later postoperative period, CT can be performed to establish the baseline for future follow-up scans and to determine the number and size of residual flecks of calcification. In the immediate postoperative period (first 48 h) and later, gadolinium-enhanced MRI may be performed to establish a baseline appearance and to determine whether residual tumor is present.[6, 7, 8, 9, 10, 11, 12, 13, 14, 15]

Nonenhanced CT may be required to detect calcifications if typical MRI findings are absent. A papillary-type lesion can be missed on MRI or CT when no characteristic cystic component is present or when lesions are not enhanced after the administration of intravenous (IV) contrast material (as occurs in approximately 10% of patients).

Limitations

MRI cannot be used in patients with pacemakers or implanted ferromagnetic metallic objects or in those with metallic foreign bodies in the brain, spinal cord, or soft tissues near important vascular structures. The use of MRI also is limited in patients with claustrophobia and in those who are unable to remain stationary for the required time. Both CT and MRI evaluations require IV contrast enhancement; therefore, IV access is needed.

Failure to make the diagnosis is a pitfall because tumor calcifications on CT may be misinterpreted as enhancing aneurysms, and correlation with cerebral angiographic findings may be needed to differentiate the 2 entities. In addition, calcifications appear as signal voids on MRI and can be misinterpreted as aneurysms. MRA should be performed in questionable cases.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK],



gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.




http://www.fda.gov/cder/drug/advisory/gadolinium_agents_20061222.htm


Radiography

A lateral radiogram of the skull may demonstrate calcifications in either the sella turcica or suprasellar space (see the first image below), or it may demonstrate sellar expansion or erosion of clinoid process or dorsum sella (see the second image below).

Digital radiograph in a 23-year-old woman demonstrates characteristic calcifications (arrow) in the suprasellar space. This appearance can easily be misinterpreted as that of an aneurysm.

Digital radiograph in a 39-year-old man demonstrates characteristic expansion of the sella turcica (arrows).

These calcifications can be confused with curvilinear calcifications observed with large aneurysms (occasionally referred to as eggshell calcifications). An aneurysm may be differentiated on contrast-enhanced CT, which demonstrates characteristic enhancement of the remainder of the lumen of the aneurysm, and on MRI, which shows heterogeneity of signal intensity and misregistration artifact from turbulent or pulsatile flow in the aneurysm. MRA further helps to elucidate the diagnosis in questionable cases.[2, 7, 8, 9, 11, 16]

The degree of confidence for a negative result is low because small calcifications can be missed easily. When observed, calcifications are a nonspecific finding. Soft tissue visualization on plain radiography is poor; therefore, differentiation of the type of tumor present is not possible without further imaging.


Computed Tomography

On CT, the adamantinomatous-type tumor appears as a predominately cystic mass (see the image below) with a solid component (>90%).

Axial CT scan in a 39-year-old man (same patient as in the following image) obtained without contrast enhancement demonstrates a large, cystic mass (arrow) in the suprasellar space that has predominantly fluid attenuation.

The solid component appears isoattenuating and usually contains calcifications (>80%). The sella may be expansile, and hydrocephalus may be present, depending on the exact location of the tumor. Tumors of the papillary type are usually solid and isoattenuating; they are rarely calcified. Occasionally, craniopharyngioma may appear as an intraventricular, homogeneous soft tissue mass without calcifications but possibly with hypoattenuating regions; this is observed in the papillary subtype.[9]

The location of the adamantinomatous subtype is characteristic because most are located in the sella or suprasellar region. Contrast enhancement is characteristic of the solid component (see the first image below) and cyst wall (90% cases), and an enhanced study may demonstrate displacement of the A1 segment of the anterior cerebral artery (see the second image below). Displacement of the optic chiasm also may be observed.


CT scan in a 39-year-old man (same patient as in the previous image) obtained with intravenous contrast agent shows enhancement of the anterior, solid component (arrows).

Axial contrast-enhanced CT scan in a 65-year-old man demonstrates a large, calcified suprasellar mass with anterior displacement of the A1 segment of the anterior cerebral arteries (yellow arrows). The anterior communicating artery is not well depicted.

On CT, the cystic component of the tumor extends anteriorly and/or laterally and typically wraps around the solid component. Conversely, the solid component characteristically extends posteriorly and laterally.

The degree of confidence is high because CT is sensitive for calcifications and for visualizing the cystic nature of masses. As with MRI, the noncalcified, papillary variant may sometimes be missed. A Rathke cleft cyst is rarely calcified, whereas more than 90% of craniopharyngiomas are calcified.


On MRI, the more common adamantinomatous subtype appears as a predominately cystic suprasellar mass with a solid component (see the image below). Characteristic calcifications may not be discernible, though gradient-echo (GRE) images may show susceptibility effects from calcified components. Cystic areas appear hyperintense on T2-weighted and fluid-


attenuated inversion recovery (FLAIR) images with heterogeneous isointense to hypointense solid components.[7, 9, 11, 13, 17, 18]

Contrast-enhanced T1-weighted image demonstrates a complex cystic mass (arrow) in the suprasellar space.

Changes in signal intensity vary on T1-weighted images, depending on the cystic contents, which can appear hyperintense if they have a high protein, blood product, and/or cholesterol content in the classic adamantinomatous type. In the papillary variety, solid components appear isointense on T1-weighted images.

Magnetic resonance (MR) spectroscopy shows a prominent lipid spectrum (around 1 ppm) in terms of the cystic contents. Diffusion-weighted images demonstrate variable signal intensity, which reflects the cystic contents.

The sella may be expansile, and hydrocephalus may be present, depending on the exact location of the tumor. Compression of the third ventricle may occur; when present, such compression helps in distinguishing craniopharyingioma from Rathke's cleft cyst or pituitary adenoma. Occasionally, craniopharyngiomas appear as intraventricular, homogeneous, soft tissue masses without calcifications. They may contain regions of low signal intensity; this is observed in the papillary subtype.

Some craniopharyingiomas can be both intrasellar and suprasellar, having a "snowman" appearance.[18] The location of the adamantinomatous subtype is characteristic, with most tumors located in the sellar or suprasellar region (see the images below).

Coronal T1-weighted image in a 65-year-old man obtained through the sella turcica. Image demonstrates a predominantly sellar lesion (arrows) with some suprasellar extension.


Contrast-enhanced T1-weighted image in a 66-year-old woman (same patient as in following image) obtained in a slightly lateral parasagittal plane demonstrates irregular enhancement of the solid components (arrow) and the outer rim of the tumor, which has a predominantly cystic composition.

Sagittal nonenhanced T1-weighted image demonstrates a heterogeneous, cystic mass (arrows) in the suprasellar space (same patient as in previous image).

Contrast enhancement is characteristic (see the images below). MR angiography may demonstrate displacement of the A1 segment of the anterior cerebral artery; displacement of the optic chiasm may also be observed.

Sagittal contrast-enhanced T1-weighted MRI demonstrates a complex cystic, suprasellar mass that is heterogeneously enhancing (arrow).


Gadolinium-enhanced parasagittal T1-weighted MRI in a 23-year-old woman (same patient as in the previous image) demonstrates the characteristic enhancement of the solid component (arrow) of craniopharyngioma.

On MRI, the cystic component of the tumor extends anteriorly and/or laterally and typically wraps around the solid component (see the images below).

T1-weighted MRI of a 23-year-old woman (same patient as in the following 2 images) demonstrates a suprasellar mass with characteristic intermediate- to high-signal material in the cystic material (arrows).

Sagittal T1-weighted MRI in a 23-year-old woman (same patient as in the following image) demonstrates the high signal intensity of the cystic material (yellow arrow).

Conversely, the solid component of the tumor characteristically extends posteriorly and laterally (see the image below).


Axial contrast-enhanced T1-weighted MRI demonstrates enhancement of the solid component (arrows) of the lesion.

Adjacent brain parenchyma may show hyperintensity on T2-weighted or FLAIR images, which indicates edema from compression of optic chiasm and/or tracts, gliosis, or tumor invasion. Recurrence in both the local tumor bed and along surgical tracts may the result of implantation of craniopharyngioma tissue. Therefore, post-treatment MRI has been recommended, even in patients whose primary tumor was resected completely.[13, 18]

The degree of confidence is high. Although MRI without a GRE sequence can be insensitive for calcifications, it is sensitive for determining the fluid or soft tissue content of a given area. False-positive results may occur as a result of misidentification of a similar lesion in the differential diagnosis.

A Rathke cleft cyst (RCC) can usually be differentiated because it is rarely calcified, whereas 64-92% of craniopharyngiomas are calcified. An RCC is also usually associated with anterior infundibular displacement and does not have a solid component. In addition, it shows contrast enhancement less frequently than other tumors do. Small RCCs may be indistinguishable from the rare intrasellar craniopharyngiomas.

A suprasellar arachnoid cyst has angular margins and is entirely cystic, with no solid component or enhancement.

Hypothalamic or chiasmatic astrocytomas arise at their respective locations and appear solid with areas of necrosis. The pilocytic variety may show cystic changes; however, calcification is less common with this tumor than with others. A moderate degree of enhancement may be seen.

Meningiomas demonstrate the dural tail sign, which is absent with craniopharyngiomas. Meningiomas also have a wide dural base and densely adhere to the dura. A craniopharyngioma can grow to more than 5 cm, but most are smaller. Conversely, a germinoma is almost always large, and its signal intensity and enhancement are homogeneous. A cystic component rarely is observed, and a pineal satellite lesion may be present.


Pituitary adenoma is rare in children; it is mostly intrasellar in the microadenoma variety. Macroadenomas may have suprasellar components with cystic, hemorrhagic, and enhancing areas; findings closely mimic those of a craniopharyngioma. However, calcification is rare.

Teratomas contain mixed solid and cystic components, as do craniopharyngiomas, but teratomas typically contain some fat.

Epidermoids can be distinguished by their characteristic scalloped margins and by the fact that, with epidermoids, there is minimal or no peripheral enhancement. Epidermoids are typically strongly hyperintense on diffusion-weighted images. Dermoids also contain a fatty component.

Ultrasonography

With the wide availability and documented accuracy of CT and MRI, ultrasonography has not been accepted as a universal tool for the evaluation of pituitary masses. A few case reports have described the use of ultrasonography with color Doppler imaging in the antenatal diagnosis of fetal craniopharyngiomas. Adult craniopharyngiomas have also been evaluated with the use of color Doppler and ultrasonographic contrast agents. [9, 11, 14]

However, the modality is operator dependent, it can be limited because of beam attenuation by the bony skull vault, and lesions may be missed.

Nuclear Imaging

Although evidence of increased metabolic activity in the tumor mass and surrounding brain has been observed, nuclear evaluation is not preferred for the diagnosis of craniopharyngioma.

Angiography

Most of the findings relate to displacement of the cerebral vasculature secondary to mass effect. Specifically, the position of the anterior cerebral artery is well correlated with the location of the tumor. When the A1 segment of the anterior cerebral artery and the anterior communicating artery are in the usual position, the tumor is contained entirely or almost entirely within the sella.

When the A1 segment and the anterior communicating artery are elevated (see the image below) but the basilar artery is in the usual position, the tumor protrudes anteriorly and projects between the optic nerves, deviating the chiasm posteriorly. When the A1 segment and the anterior communicating artery are elevated and the basilar artery is displaced posteriorly, the tumor protrudes posteriorly and pushes the chiasm anteriorly. Stretching of the posterior communicating arteries also may be noted. An unreliable finding is a small, vascular blush in the region of the tumor.


Angiogram obtained in the anteroposterior projection clearly shows elevations of the A1 segment of the anterior cerebral artery (arrows) and anterior communicating artery.

CTA and MRA have supplanted angiography as the primary diagnostic techniques, and angiography is now rarely needed to differentiate the tumor from an aneurysm of the anterior communicating artery.



Imaging in Glioblastoma Multiforme Author : Alex Lobera, MD Chairman, Department of Radiology, Memorial Medical Center, Las Cruces, New Mexico

Overview

Glioblastomas (malignant glioma) are the most common adult malignant brain tumors, [1, 2, 3]

and 20% of all primary brain neoplasms are glioblastoma multiforme tumors. Glioblastoma multiforme (GBM; malignant glioma) is the highest-grade form of astrocytoma and makes up about two thirds of all brain astrocytomas. The prognosis for this tumor is at the extreme worst end because of its high-grade status.[1, 4] See the images below

T1-weighted axial gadolinium-enhanced magnetic resonance image demonstrates an enhancing tumor of the right frontal lobe. Image courtesy of George Jallo, MD.

T2-weighted image demonstrates the same lesion as in the previous image, with notable edema and midline shift. This finding is consistent with a high-grade or malignant tumor. Image courtesy of George Jallo, MD.



Computed tomography (CT) scanning can demonstrate the tumor and associated findings; however, in making the glioblastoma multiforme (GBM; malignant glioma) diagnosis, CT scanning may cause small tumors to be missed. A small low-grade glioma that is missed with a screening study may eventually progress to glioblastoma multiforme (GBM; malignant glioma). In addition, this modality may not depict all multifocal lesions. Cerebrospinal fluid (CSF) spread, particularly early spread, may also be difficult to diagnose with CT scanning.

Magnetic resonance imaging (MRI) is significantly more sensitive to the presence of tumor, as well as its associated findings, in the inclusion of peritumoral edema, and is the modality of choice for the examination of a patient with suspected or confirmed glioblastoma multiforme (GBM; malignant glioma). This lesion is a highly infiltrative tumor; thus, tumor cells are usually found beyond the margins of an area of abnormal signal intensity on MRIs. Central nervous system (CNS) metastases are frequent, but extracerebral metastases are rare.

After surgery, differentiating between recurrent tumor and scar tissue on the basis of MRI findings alone may be difficult. Positron emission tomography (PET) scanning is useful in this regard.[5, 6, 7, 8, 9, 10, 11, 12]

Because of the highly variable appearance of the tumor, it may sometimes mimic other conditions, such as an infarct, an abscess, or even a tumefactive plaque in multiple sclerosis, and thereby delay diagnosis. In terms of the imaging appearance and the appearance of a mass in the spectrum from low-grade astrocytoma to glioblastoma multiforme (GBM; malignant glioma), the following generalizations can be made (although some exceptions apply):

The incidence of calcification decreases in the spectrum from low-grade astrocytoma to glioblastoma multiforme (GBM; malignant glioma).

The incidence of enhancement increases in the spectrum from low-grade astrocytoma (preserved blood-brain barrier [BBB], low enhancement frequency) to glioblastoma multiforme (GBM; malignant glioma) (disrupted BBB).

Hemorrhage, necrosis, mass effect, and edema incidence patterns are the same as those for enhancement.

Unless hemorrhagic changes are present, most tumors are hypointense on T1-weighted MRIs and hyperintense on T2-weighted MRI.

Enhancement on CT scans means enhancement on MRIs.

Some forms of glioblastoma multiforme (GBM; malignant glioma) are considered variants. Giant cell glioblastoma (monstrocellular GBM) is a variant of GBM but has the same imaging findings as those of GBM.


Radiography

Radiographs are not used in the evaluation of the primary tumor. However, in cases of tumors that invade the calvarium, x-ray studies may demonstrate skull erosion changes. In the uncommon case with distant skeletal metastases, radiographs may demonstrate these as well.

Computed Tomography

CT scan results offer a relatively high degree of confidence for the diagnosis of glioblastoma multiforme (GBM; malignant glioma). However, some lesions may mimic glioblastoma multiforme (GBM; malignant glioma), such as space-occupying lesions including brain abscess, infarct with hemorrhagic transformation, and neoplasms of a lower grade than that of glioblastoma multiforme (GBM; malignant glioma). In addition, some types of demyelinating lesions (eg, giant multiple sclerosis plaques) may mimic glioblastoma multiforme (GBM; malignant glioma), and the multifocal form of GBM may be indistinguishable from diffuse multiple sclerosis.

With gliomatosis cerebri, CT scan findings may be normal, or images can show widespread low-attenuating regions, with no focal mass and no enhancement.

Nonenhanced CT scan findings may include a heterogeneous poorly marginated mass; internal areas of low or fluid attenuation that are the foci of necrosis (present in as many as 95% of GBMs); internal areas of high attenuation that are the foci of hemorrhage or, rarely, calcifications (more common if GBM is the result of transformation of a low-grade astrocytoma or after therapy); and a significant mass effect and edema (vasogenic distribution of the edema).

Enhanced CT scans include significant enhancement of findings such as irregularity and inhomogeneity; possible ring enhancement; possible, but uncommon, solid enhancement; possible little enhancement possible in diffuse forms.


MRI has a high degree of confidence in the diagnosis of glioblastoma multiforme (GBM; malignant glioma). In fact, it has the highest degree of confidence of any imaging modality. Some lesions, mainly space-occupying lesions with hemorrhagic components, may mimic glioblastoma multiforme (malignant glioma) on MRIs. These include abscesses and infarcts.

MRI findings demonstrate a heterogeneous mass that is generally of low signal intensity on T1-weighted images and high signal intensity on T2-weighted images.[13] There are internal cystic areas, internal flow voids representing prominent vessels, internal areas of high signal intensity on T1 (hemorrhagic foci), neovascularity, necrotic foci, significant peritumoral vasogenic edema, and significant mass effect. Irregular but intense enhancement after the administration of gadolinium-based contrast material (same pattern as with enhanced CT scanning) is also found, as are metastatic foci of intracerebral metastasis that are common with GBM (MRI has a higher sensitivity to these lesions than CT scanning.)


Gliomatosis cerebri is seen as a diffuse white-matter abnormality with signs of increased intracranial pressure, including ventricular compression and subarachnoid space obliteration (the differential diagnosis includes normal pressure hydrocephalus).

Gliosarcoma are usually well-circumscribed, sarcomatous or infiltrative gliomatous elements that possibly resemble meningiomas. Other imaging findings are similar to those of glioblastoma multiforme (GBM; malignant glioma).

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], and gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.


Nuclear Imaging

Positron emission tomography (PET) scanning is a useful adjunct to the evaluation of glioblastoma multiforme (GBM; malignant glioma), particularly after resection. In this setting, differentiation of residual or recurrent tumor and postoperative edema or scarring is often difficult on MRIs or CT scans. PET scanning with 18-fluorodeoxyglucose (FDG) is useful in cases of active tumor, which shows high metabolic activity and glucose utilization, and in cases of simple postoperative edema or scars, which usually have no increased activity.

In the setting of resection for known tumor, the finding of increased tracer uptake at the surgical site is a reliable indicator of recurrent disease. However, after radiotherapy, increased activity may be seen at the surgical site without tumor recurrence. False-positive findings occur after radiation therapy, when active granulation tissue can metabolize FDG, which may limit the sensitivity of the study in this setting. An epileptogenic focus near the surgical site may show increased uptake on PET scanning, particularly if epileptic activity is high.

Angiography

Angiographic findings associated with glioblastoma multiforme (GBM; malignant glioma) include the following: hypervascular mass with tumor blush; prominent feeding and draining vessels, as well as arteriovenous shunting (this may mimic an arteriovenous malformation); aberrant vessels and vascular pooling and stasis (common); and mass effect, which is seen as displacement of vessels.





Angiography has low specificity for the diagnosis of glioblastoma multiforme (GBM; malignant glioma). Although images may show vascular displacement on the basis of the mass effect of the tumor, virtually any other space-occupying lesion may have similar findings. In addition, the hypervascularity of glioblastoma multiforme (GBM; malignant glioma) may mimic vascular malformations. Thus, any space-occupying lesion or vascular malformation with hypervascularity may cause a false-positive finding. Small tumors or those with a high infiltrative component and little or no vascular displacement may cause a false-negative finding.



Brain Imaging in Hemangioblastoma Author

Rocio Jocelyn Urena, MD Radiologist, Imaging Consultants of South Florida

Rocio Jocelyn Urena, MD is a member of the following medical societies: American College of Radiology, European Society of Radiology, and Radiological Society of North America

Coauthor(s)

Helmuth W Gahbauer, MD Assistant Clinical Professor, Department of Radiology, Yale University School of Medicine

Helmuth W Gahbauer, MD is a member of the following medical societies: American College of Radiology and American Society of Neuroradiology

Overview

Hemangioblastomas are considered to be benign neoplasms and represent 1-2% of all primary central tumors. Historically, hemangioblastomas are linked to von Hippel-Lindau (VHL) disease.[1] In 1927, Arvid Lindau reported the connection between retinal angiomas and hemangiomas of the cerebellum.

VHL is an autosomal dominant condition involving chromosome 3 characterized by specific benign and malignant tumors with variable expressivity.[2, 3] Cerebellar hemangioblastoma is the most common initial manifestation, affecting 64% of patients with VHL. [4] In many series, cerebellar hemangioblastoma is the most important cause of mortality, affecting 47.7% of patients with VHL,[5] followed by renal cell carcinoma.[5, 6]

In patients with a positive family history, a single cerebellar hemangioblastoma is sufficient to make the diagnosis. If no known family history exists, at least 2 cerebellar hemangioblastomas or 1 hemangioblastoma plus 1 visceral tumor are necessary to justify the diagnosis of VHL.

Various organs can be involved.[5] Of patients presenting with hemangioblastomas, 70% do not have a family history, and 3-25% of these patients have tumors associated with VHL. Hemangioblastoma appears to be associated more with VHL than previously reported, and it has been suggested that all patients with sporadic nonhereditary tumors should be evaluated for evidence of VHL disease.[4, 6, 7]

See the hemangioblastoma images below.



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Patient with von Hippel-Lindau disease. T1-weighted gadolinium-enhanced MRI shows an enhancing nodule. Coronal T2-weighted MRI shows a small high-signal-intensity cyst.

Sagittal T1-weighted gadolinium-enhanced MRI shows a homogeneous intense enhancing tumor in the cistern magna.

The nidus of the tumor abuts the pia matter, from which the tumor receives its vascular supply. The tumor is more frequently superficial than deep. Of hemangioblastomas, 60-70% are cystic, and the remainder are solid. Solid tumors are more common in the brainstem and supratentorial locations than elsewhere. The mural nodule is hypervascular and relatively small, less than 15 mm in diameter.


From a macroscopic point of view, hemangioblastomas can appear as solid or cystic tumors with mixed forms. Four types can be distinguished, as follows:

Type 1, or the simple cyst form, is rare (6%) and characterized by a cyst with clear fluid and smooth walls and without evidence of a mural nodule at angiography or surgery.

Type 2, or the macrocystic form, is the most frequent (65%) and characterized by a cyst of variable size with a mural nodule of approximately 1 cm.

Type 3, or the solid form (25%), has a solid consistency with blurred limits and marked vascularization.

Type 4, or the microcystic form (4%), is solid but contains small cysts of a few millimeters in size; therefore, 75% of infratentorial hemangioblastomas have a cystic component of variable size (see the image below).


Contrast-enhanced MRI is considered to be the best method for screening patients with von Hippel-Lindau (VHL) and to be the first evaluation used in symptomatic patients. However, preoperative angiography remains important for defining feeding vessels and aiding in embolization.[8, 9]

Prior to MRI, contrast-enhanced CT scanning was performed frequently; however, beam-hardening artifacts produced by the petrous and vertebral bone limited its use.

MRI is superior to nonenhanced CT in the detection of vascular components of the tumor. [8,

10] Contrast-enhanced CT has the same sensitivity as nonenhanced MRI; however, it is inferior to contrast-enhanced MRI.[8] Contrast-enhanced MRI permits the identification of small tumor nodules. In addition, MRI is helpful in separating cystic and solid components of the tumor from edema. Patients with VHL should be screened, and follow-up studies should be performed at 6 months.

The sensitivity of MRI increases with the use of gadolinium-based contrast material. Angiography is better in the detection of small (< 1 cm) vascular tumor components, and it is


better for showing the vascular nature, supply, and drainage of tumors, compared with CT.[11] However, CT and MRI depict tumor cysts better.[12]

Use of a gadolinium-based contrast agent is mandatory in the evaluation of hemangioblastomas because it increases the sensitivity for small, solid lesions.[11, 13] When the diagnosis of hemangioblastoma is established, a careful evaluation for other small enhancing lesions should be performed because of the multiple lesions seen in some patients. The presence of multiple lesions has an important impact on the prognosis.[6]

In hemangioblastomas located near the pia, differentiation from meningiomas can be difficult in certain patients. It is always important to look for characteristics that can help in diagnosing a vascular tumor, which is particularly important before surgery. In some patients, complete removal of the mural nodule is enough; however, in patients in whom the transition from solid tumor to cystic tumor with a mural nodule has been observed, the radiologist should perform careful follow-up imaging to assess the behavior of the lesions.

Further follow-up studies should be performed at 1-year intervals to detect the development of additional tumors and monitor progression of existing lesions.[8] Early treatment improves the outcome. Using MRI and CT at 1- to 2-year intervals, Conway et al identified 74% of lesions that required surgery before the patients became symptomatic.[4]

For excellent patient education resources, visit eMedicine's Cancer and Tumors Center. Also, see eMedicine's patient education article Brain Cancer.

Computed Tomography

On CT scans, the tumor appears well circumscribed, solid, or cystic, with a mural nodule. Usually, the nodule is smaller than the cyst. This feature helps in differentiating it from cystic astrocytoma, which tends to have a larger nodule. The cyst is hypoattenuating on CT scans.[14, 15, 16, 17]

In precontrast studies, the nodule is isoattenuating relative to the surrounding brain tissue, but it is hyperattenuating in occasional cases. After the administration of contrast material, the attenuation is equivalent or higher than that of the straight sinus, and the nodule enhances homogeneously. Commonly, the nodule abuts a pial surface. Multiplanar CT and MRI help in identifying the subpial localization (see the image below).

T1-weighted postgadolinium MRI shows 2 subpial, enhancing nodules in a patient with von Hippel-Lindau disease. One nodule is small and present in the cistern magna; the other is in the cervical spine.


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Generally, the cyst wall does not enhance, but occasionally, it can appear as a paper-thin line of enhancement that represents a combination of compressed cerebellar tissue and gliosis. Occasionally, the edge of the tentorium can be misinterpreted as an enhancing rim, with differentiation made by using coronal sections.

CT shows all the clinically significant features of hemangioblastoma, along with secondary features such as hydrocephalus and edema. False-negative results are found in patients with small nodules (< 5 mm) that can be obscured by posterior fossa artifacts; therefore, CT is not a sensitive screening procedure. False-positive results are rare. Metastases and cystic astrocytoma can appear similar. A diagnostic pitfall is the hemangioblastoma with a small central lucency, which can be interpreted as a necrotic metastasis. In this case, the ringlike enhancement of the necrotic nodule is thick and irregular.[14]


MRI with gadolinium enhancement is the best study for screening, with the highest sensitivity and specificity compared with CT and nonenhanced MRI. Large studies are necessary to achieve a high degree of confidence; however, the advantages are obvious. [8, 12,

13, 18]

Intracranial hemangioblastomas can manifest as 3 morphologic patterns based on the macroscopic pathology. These are well correlated with the MRI findings and include the following[19, 9] :

Cyst with a small mural nodule Solid mass with a central cystic component

Solid tumor without a cystic component

A cyst with a small mural nodule is the most common presentation. Cystic fluid surrounding the nodule is hyperintense on T1-weighted images and hyperintense on T2-weighted images. Characteristics of the fluid vary slightly related to protein content. The mural nodule is isointense on T1-weighted images and demonstrates high signal on T2-weighted images. After the administration of gadolinium-based contrast medium, the nodule shows prominent enhancement and the cyst does not enhance (see the image below).[19]

Coronal and axial T1-weighted gadolinium-enhanced MRIs show a large cyst with a peripheral intense enhancing mural nodule.


Solid masses with a central cyst behave similarly; therefore, the different morphologic patterns have been postulated to be part of the natural history of a solid tumor that develops a cystic component around or within it (see the images below).[20, 21]

Patient with von Hippel-Lindau disease. T1-weighted gadolinium-enhanced MRI shows an enhancing nodule. Coronal T2-weighted MRI shows a small high-signal-intensity cyst.

Patient with von Hippel-Lindau disease (same patient as in previous image at 1-year follow-up). Coronal T1-weighted gadolinium-enhanced MRI shows an enhancing nodule that has grown in size adjacent to a low-signal-intensity cyst. T2-weighted MRI shows a cystic area that has increased in size, with high-signal-intensity characteristics.

Solid hemangioblastomas occur less frequently than the other patterns (see the image below). The lesion is isointense or hypointense on T1-weighted images and

hyperintense on T2-weighted images. Transition from a solid tumor to a classic cystic tumor with a small mural nodule has been reported. Occasionally, signal in solid tumor

components can be heterogeneous on T1-weighted images, with areas of increased signal within the solid portion. These regions may represent lipid in the stromal cells or

methemoglobin from hemorrhage.[10]

Sagittal (top left) and coronal (top right) T1-weighted gadolinium-enhanced MRI images in a patient with von Hippel-Lindau disease presenting with 2 infratentorial hemangioblastomas. The larger tumor shows with cystic central areas. Bottom left, T1-weighted MRI shows that both lesions have low signal intensity. Bottom right, Abdominal axial image of the same patient shows multiple cysts in the pancreas.


Medulloblastoma Imaging Author

Djamil Fertikh, MD Attending Physician, Division of Radiology, Association of Alexandria Radiologists

Djamil Fertikh, MD is a member of the following medical societies: American College of Radiology, American Medical Association, American Society of Neuroradiology, and Radiological Society of North America

Overview

One half of primary brain tumors in children originate in the posterior fossa. Medulloblastomas are highly malignant tumors; they are the most common malignant posterior fossa tumor in the pediatric population. They are characterized by their tendency to seed along the neuraxis, following cerebrospinal fluid (CSF) pathways, and they represent one of the few brain tumors, including ependymoma, pinealoblastoma, and lymphoma, to metastasize to extraneural tissues. Originally classified as a glioma, medulloblastoma is now referred to as a primitive neuroectodermal tumor (PNET). (See the images below.)[1, 2, 3, 4, 5, 6]

Medulloblastoma. Unenhanced CT shows a high-density midline tumor in the posterior fossa with a small amount of surrounding vasogenic edema exerting mass effect on the fourth ventricle, with a moderate degree of hydrocephalus.






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Medulloblastoma in a 27-year-old man. Nonenhanced sagittal T1-weighted image shows a poorly defined, laterally situated, hypointense cerebellar mass with a small cystic area.


Of medulloblastoma patients, 10-30% demonstrate CSF dissemination at diagnosis, mandating evaluation of the entire neuraxis with contrast-enhanced studies. Extra-axial metastases account for 5% of cases; most metastases are to the bone; less frequently, metastases are to the liver and lymph nodes.

Children with nondisseminated medulloblastoma have a high likelihood of long-term survival, with a 5-year survival rate of 80%. Intensified therapy has been shown to increase survival in children with disseminated disease. However, the quality of life in long-term survivors remains an important issue, because most survivors have neurologic and cognitive deficits.[7]

Medulloblastomas have been associated with basal nevus syndrome (Gorlin syndrome), Turcot syndrome, ataxia telangiectasia, xeroderma pigmentosum, and blue rubber bleb syndrome.

Standard treatment is surgery followed by radiation to the entire neuraxis. Medulloblastomas are radiosensitive. Gross total resection of the tumor, when possible, is the aim of surgery. Resection usually is achieved in 50% of patients, according to Thapar et al.[8]

Signaling pathways that regulate medulloblastoma tumor formation have been discovered. Advances in the molecular biology of medulloblastoma indicate that better understanding of the growth control mechanisms in medulloblastoma may lead to the development of new therapies for the disease.[9, 10]


Although medulloblastoma has a highly characteristic appearance on computed tomography (CT) scanning, magnetic resonance imaging (MRI) is the preferred tool. The multiplanar capability of MRI provides better 3-dimensional visualization of the extent of the tumor, as well as better visualization of edema and herniation, when present. MRI also is better for evaluating the remainder of the neuraxis for metastasis. In addition, MRI spectroscopy may help better delineate the tumor's boundaries.[11, 12, 13, 14]


With CT scanning, only axial images can be obtained; by contrast, with MRI, any plane can be used for imaging. On CT scans, posterior fossa images often are degraded by beam-hardening artifacts.


Computed Tomography

Medulloblastomas are highly cellular; therefore, on noncontrast CT, their classic appearance is that of a high-density midline mass. In most patients (90%), a varying degree of hydrocephalus is apparent (see the image below.) Variable amounts of asymmetric edema are seen in approximately 90% of patients.

Medulloblastoma. Unenhanced CT shows a high-density midline tumor in the posterior fossa with a small amount of surrounding vasogenic edema exerting mass effect on the fourth ventricle, with a moderate degree of hydrocephalus.


On enhanced CT scans, a marked homogeneous enhancement of the tumor is seen (see the image below). In rare circumstances (13%), calcifications are found.

Medulloblastoma. Following intravenous injection of contrast material, the tumor shows marked diffuse and homogeneous enhancement.


Metastatic nodular seeding may be seen in the supratentorial subarachnoid space on contrast-enhanced CT scans and in the spinal canal on CT myelography.

Necrotic, cystic areas and hemorrhage are seen in approximately 10-16% and 3% of patients, respectively.


In a child, especially a boy, the presence of a high-density midline posterior fossa mass with diffuse marked enhancement is highly suspicious for medulloblastoma.

CT scanning is superior to MRI in depicting small punctate calcifications.


Medulloblastomas are hypointense to isointense on T1-weighted images. (See the images below.)


Medulloblastoma in a 27-year-old man. Nonenhanced sagittal T1-weighted image shows a poorly defined, laterally situated, hypointense cerebellar mass with a small cystic area.


Medulloblastoma. Axial MRI of the posterior fossa shows a right-sided laterally located mass with mixed isointense and hyperintense signal intensity. Surrounding edema is seen as high signal intensity.


Medulloblastoma. Coronal T1-weighted postcontrast image shows a markedly enhancing peripheral tumor.


Medulloblastoma in a 6-year-old boy. Sagittal T1-weighted image shows a slightly hyperintense mass in the region of vermis with compression of the fourth ventricle and obstructive hydrocephalus. The brain stem is also compressed by this mass. The lateral and third ventricles are dilated.


Medulloblastoma. Axial T1-weighted image shows a hypointense mass in the midline, just posterior to the fourth ventricle. The fourth ventricle and brain stem are displaced anteriorly and compressed.


Medulloblastoma. Axial T1-weighted postcontrast image demonstrates an irregular, heterogeneous enhancing mass. Note the dilatation of both temporal horns, indicating obstructive hydrocephalus.


On T2-weighted images, appearances may vary from isointense to hyperintense. (See the image below.)

Medulloblastoma. Axial T2-weighted image reveals a predominantly isointense mass to gray matter with small foci of cystic changes.

Medulloblastomas classically demonstrate heterogeneous hypointense or isointense signal. Calcifications appear as areas of signal void on T2-weighted images.

The pattern of enhancement after intravenous injection of gadolinium is similar to that after injection of iodinated contrast material on CT. However, the greater sensitivity of MRI often


enables appreciation of a slightly heterogeneous enhancing pattern that is not as readily evident with CT.


NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness.

The blurring of cerebellar folia and fissures, representing tumor spread via CSF pathways (best depicted on midline sagittal images), is a helpful sign. Subarachnoid or intraventricular seeding usually demonstrates contrast enhancement.

Drop metastases appear as high signal foci on contrast-enhanced T1-weighted images in the extramedullary and intradural space; occasionally, they are subpial in location.

Proton spectroscopy demonstrates a nonspecific elevation of the choline peak, representing cell membrane turnover; a decreased aspartate peak, representing loss of neuronal tissue; and variable lipid and lactate.


Because of the age group in which medulloblastomas occur, as well as the location and general appearance of the tumors, the degree of confidence usually is high with MRI.

Nuclear Imaging

No findings specific to medulloblastoma have been described; however, single-photon emission CT (SPECT) and positron emission tomography (PET) scanning complement CT scanning and MRI. Although the mechanism of uptake is not clearly understood, 80% of pediatric tumors show uptake of thallium-201 chloride (201 TI). These techniques also are important in differentiating high-grade from low-grade tumors and residual tumor from postoperative changes.


Thallium SPECT and fluorine-18-flurodeoxyglucose PET are complementary in diagnosing gliomas, although thallium SPECT was found to correlate more significantly with malignancy. In a series of 19 patients, Kahn et al demonstrated that the sensitivity and specificity for



tumor recurrence is 69% and 40%, respectively, for201 TI, and 81% and 40%, respectively, for PET.[15]

Angiography

Angiographic findings are not diagnostic. Medulloblastoma may demonstrate abnormal neovascularity. Because medulloblastoma is a posterior fossa tumor, anterior displacement of the precentral cerebellar vein may be seen. Posterior and inferior displacement of the inferior vermian vein also may be seen.


Angiographic findings are nonspecific for the diagnosis of medulloblastoma and are only indicative of a space-occupying lesion.



Imaging in Oligodendroglioma Author

Paule Peretti, MD Neuroradiologist, Radiological Department, Sainte Marguerite Hospital, France

Paule Peretti, MD is a member of the following medical societies: French Society of Radiology

Coauthor(s)

Hervé Brunel, MD Physician, Department of Neuroradiology, Montpellier of Pr Bonafé, France Maryline Barrié, MD Assistant Lecturer in Oncology, Universite De La Mediteranee Olivier Chinot, MD Lecturer, Department of Oncology, Universite De La Mediteranee

Overview

Oligodendroglioma is a well-differentiated, diffusely infiltrating tumor of adults that is typically located in the cerebral hemispheres and is predominantly composed of cells that morphologically resemble oligodendroglia. Examples of oligodendrogliomas are provided below.[1, 2]

Lateral radiograph of the skull in a 44-year-old man with a 3-year history of epileptic seizures. This radiograph shows a left frontal oligodendroglioma. Note the vermicular calcifications that are projecting on the frontal lobe.

Computed tomography scan of a low-grade oligodendroglioma. This image shows hypoattenuation of the left frontal lobe without contrast enhancement.

According to several studies, survival in patients with oligodendrogliomas is not correlated with tumor location or surgical removal. Rather, survival seems to be primarily correlated with the histologic features, clinical findings (age at onset, epilepsy vs deficit), and radiologic criteria (especially contrast enhancement).[3, 4, 5, 6]


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Computed tomography (CT) scanning and magnetic resonance imaging (MRI) are complementary exploratory techniques that are suitable for imaging oligodendrogliomas.[7]

However, tumor calcification is better defined on CT scans than on MRI.[8]

Diagnosis

Because of the typically slow growth of oligodendrogliomas, the elapsed time between the initial symptoms and clinical diagnosis may vary from 1 week to 12 years. However, with easy access to MRI, this interval has been greatly reduced.

Treatment

Approximately two thirds of anaplastic oligodendrogliomas and oligoastrocytomas respond to a combination of surgery, radiation, and PCV chemotherapy. The efficacy of radiotherapy on overall survival has been demonstrated, but the optimal timing is unknown. Although immediate postoperative radiation therapy is indicated for incompletely resected higher-grade oligodendrogliomas, its use for partially resected low-grade tumors is controversial.[9]

For excellent patient education resources, visit eMedicine's Cancer and Tumors Center. Also, see eMedicine's patient education article Brain Cancer.

Computed Tomography

Oligodendrogliomas are the brain tumors with the highest frequency of calcification. CT scanning must be performed before and after the injection of contrast material to avoid missing the presence of calcifications. Typically, a round or oval, well-limited, and fairly large peripheral lesion is revealed. The tumor matrix is either hypoattenuating or isoattenuating and occasionally hyperattenuating because of tumoral hemorrhage or calcification.

Calvarial erosion in association with slow-growing, peripherally located oligodendrogliomas is occasionally noted. Calvarial erosion also appears to be independent of the tumor grade. Contrast enhancement is sometimes difficult to visualize because of the presence of calcification. (See the images below.)

Contrast-enhanced computed tomography scan in a 44-year-old man with a 3-year history of epileptic seizures. The patient has a left frontal oligodendroglioma. This image reveals a calcified hypoattenuating lesion that is invading the corpus callosum.


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Contrast-enhanced computed tomography scan in a 50-year-old man. This image reveals recurrence of a frontal oligodendroglioma in the right basal ganglia that was excised 6 years earlier.

Computed tomography scan of a low-grade oligodendroglioma. This image reveals a well-demarcated, left frontal hypoattenuating lesion with a small calcification.

Computed tomography scan of a low-grade oligodendroglioma. This image shows hypoattenuation of the left frontal lobe without contrast enhancement.

Computed tomography scan of a low-grade oligodendroglioma. This image shows left frontal hypoattenuation that mainly involves the white matter.


Tumoral calcification, seen in approximately 40% of patients, is better defined on CT scans than on MRIs. It seems to have no direct correlation with the tumor grade.



Oligodendrogliomas do not behave specifically; they are usually heterogeneous but have a relatively low intensity on T1-weighted sequences and a high intensity on T2-weighted sequences. Peritumoral edema is nicely depicted with T2-weighted sequences and with fluid-attenuated inversion recovery sequences, which are sensitive, but surrounding vasogenic edema is not common in oligodendrogliomas. Perifocal edema is less often observed in low-grade oligodendrogliomas. Small cystic-appearing regions and hemorrhage are commonly found in the mass. Examples of low-grade oligodendrogliomas are presented below.[10]

Axial fluid-attenuated inversion recovery magnetic resonance imaging scan of a low-grade oligodendroglioma (same patient as in the 2 Images that follow). This image shows heterogeneous high signal intensity in the left frontal lobe.

Axial T1-weighted magnetic resonance image of a low-grade oligodendroglioma. This image shows heterogeneous low signal intensity in the left frontal lobe that involves the cortex and white matter. Note the mass effect on the cortical sulci.

Sagittal gadolinium-enhanced T1-weighted magnetic resonance image of a low-grade oligodendroglioma. This image demonstrates no contrast enhancement.


Sagittal T1-weighted sequence magnetic resonance of a low-grade oligodendroglioma (same patient as in the 4 images that follow). This image shows heterogeneous low signal intensity involving the frontal lobe. Note the involvement of the corpus callosum.

Sagittal gadolinium-enhanced T1-weighted magnetic resonance image of a low-grade oligodendroglioma. This image shows a huge infiltrative lesion in the frontal lobe, no contrast enhancement, and a mass effect on the cortical sulci.

Axial T2-weighted sequence magnetic resonance image of a low-grade oligodendroglioma. This image shows heterogeneous high signal intensity in the left frontal lobe and low signal intensity in the white matter of the right parietal lobe that corresponds to a cavernous hemangioma.

Axial gadolinium-enhanced T1-weighted magnetic resonance image of anaplastic transformation of a low-grade oligodendroglioma, 4 years later. This image depicts local recurrence after surgery, with contrast enhancement in the left frontal lobe.


Axial gadolinium-enhanced T1-weighted magnetic resonance image of anaplastic transformation of a low-grade oligodendroglioma, 4 years later. This image shows multifocal recurrence. A contrast-enhanced tumoral nodule is seen in the right temporal lobe. Note the left retro-ocular cavernous hemangioma.

Contrast enhancement is better seen with MRI than with CT scanning,[11, 12, 13, 14] especially with magnetization-transfer, T1-weighted spin-echo MRI sequences after

gadolinium enhancement. The importance of contrast enhancement for the prognosis of these tumors has been emphasized, as it seems to be the strongest negative factor

affecting survival. Because the detection of contrast enhancement is of paramount importance, postcontrast MRI should always be performed; however, it appears that the

presence or absence of contrast enhancement is not a specific finding for simply discriminating low-grade from anaplastic oligodendrogliomas. Images of an anaplastic

oligodendroglioma are presented below.[12]

Axial gadolinium-enhanced T1-weighted magnetic resonance image of an anaplastic oligodendroglioma (same patient as in the image that follows). This image shows heterogeneous contrast enhancement in the medial part of the left parieto-rolandic region.

Axial T1-weighted gadolinium-enhanced magnetic resonance image of an anaplastic oligodendroglioma, 2 months after chemotherapy. This image shows disappearance of the contrast enhancement.

MR spectroscopy is a new technique to the field that provides spatially encoded chemical information for normal and tumoral tissue in selected regions of the brain. This technique is a safe, noninvasive means of performing biochemical analyses in vivo.[15]


MR diffusion imaging can also be contributive: lower apparent diffusion coefficient (ADC) values that are indicative of water restriction are noted in high-grade tumors compared with the higher ADC values that are seen in low-grade tumors.

MR perfusion imaging is a noninvasive method of assessing the tumor microvasculature.

Such perfusion imaging has been used to calculate the perfusion parameters in gliomas, guide biopsies, provide prognostic information, and demonstrate differences in the vascularity of low-grade astrocytomas and oligodendrogliomas.

Increased vascular density is apparently seen in both low-grade and high-grade oligodendrogliomas. That pattern is in contrast to the pattern noted in fibrillary astrocytomas, for which microvascular proliferation is seen in only the higher-grade tumors.

Perfusion MR results (regional cerebral blood volume [rCBV] measurements) correlate with histologic differences in the tumor vasculature between low-grade oligodendrogliomas and astrocytomas. Low-grade oligodendrogliomas are more vascular than astrocytomas on both histologic evaluation and perfusion MR. Thus, perfusion MR is useful for improving the specificity of the diagnosis of grade II oligodendrogliomas and grade II astrocytomas.




The oligodendroglioma anatomic situation and tumoral limits are better defined on MRI than on CT scanning. A large proportion of oligodendrogliomas is peripherally situated, and the tumor usually involves the whole thickness of the cortex. MRI is particularly reliable for appreciating cortical involvement. The frontal lobes are most often involved, followed by the temporal, parietal, and occipital lobes.

Occasionally, stereotactic biopsy is performed outside of the area of contrast enhancement, leading to a falsely reassuring diagnosis (ie, low-grade oligodendroglioma). The visualization of such a contrast enhancement on MRI modifies the grading of the tumor, which becomes anaplastic. Gradient-echo sequences are highly sensitive to calcification and therefore are a useful adjunct.






High-grade oligodendrogliomas may be difficult to differentiate from the more frequent glioblastoma multiforme. However, the presence of tumor calcification, a peripheral location, and the sometimes associated calvarial erosion may indicate an oligodendroglioma.

The most difficult lesion to differentiate is the astrocytoma that appears as a hypoattenuating, nonenhancing mass on CT scans. However, these astrocytic tumors tend to be deeper in location, extend along the fiber tracts, and usually lack calcification.

Two other conditions that must be considered in the differential diagnosis are (1) dysembryoplastic neuroepithelial tumor (partial seizures beginning before age 20 y, nonneurologic deficit, cortical tumoral topography on MRI) and (2) central neurocytoma (midline tumor). Immunomarkers and electron microscopy may help in the definitive diagnosis.

Angiography

The most frequent finding with angiography is a vascular void (see the image below). A slight hypervascularization that is suggestive of malignant transformation is seldom seen.

Lateral carotid angiograph of a low-grade oligodendroglioma. This image shows a vascular void due to the tumor.



Imaging in Spinal MeningiomaAuthor

Chi-Shing Zee, MD Chief of Neuroradiology, Professor, Departments of Radiology and Neurosurgery, University of Southern California School of Medicine

Chi-Shing Zee, MD is a member of the following medical societies: American Society of Neuroradiology

Coauthor(s) http://emedicine.medscape.com/article/336141-overview#a21

John L Go, MD Assistant Professor of Clinical Radiology, Director, Spinal Imaging and Intervention, Division of Neuroradiology, University of Southern California Keck School of Medicine

Armen Hovanessian, MD Clinical Instructor, Department of Radiology, University of Southern California School of Medicine

Overview

Meningiomas are the second most common tumor in the intradural extramedullary location, second only to tumors of the nerve sheath. Meningiomas account for approximately 25% of all spinal tumors. Approximately 80% of spinal meningiomas are located in the thoracic spine, followed by cervical spine (15%), lumbar spine (3%), and the foramen magnum (2%). Most intradural spinal tumors are benign and potentially resectable. The prognosis after surgical resection is excellent.[1, 2, 3, 4, 5]

Images of spinal menigioma are provided below.

Intradural extramedullary meningioma in the lower thoracic region. Sagittal nonenhanced T1-weighted MRI demonstrates an isointense mass compressing the lower spinal cord.



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Axial T1-weighted contrast-enhanced MRI shows a right-sided intradural extramedullary enhancing mass compressing and displacing the cord to the left.

Coronal T1-weighted MRI shows a dural-based enhancing mass lesion with a small component extending into the right neuroforamen.

Sagittal reformation nonenhanced CT scan shows a calcified mass in the spinal canal.

Summary of the 2007 WHO Grading Scheme for Meningiomas

Grade I: Meningothelial, fibroblastic, transitional, angiomatous, microcystic, secretory, lymphoplasmacytic, metaplastic, psammomatous; does not fulfill criteria for grade II or III.

Grade II (Atypical): Chordoid, clear cell; 4 or more mitotic cells per 10 hpf and/or 3 or more of the following: increased cellularity, small cells, necrosis, prominent nucleoli, sheeting, and/or brain invasion in an otherwise grade I tumor.

Grade III (Anaplastic):Papillary, rhabdoid; 20 or more mitoses per 10 hpf and/or obviously malignant cytologic characteristics such that tumor cell resembles carcinoma, sarcoma, or melanoma.



Magnetic resonance imaging (MRI) with intravenous injection of gadolinium-based contrast agent is the preferred examination. If MRI is not available, computed tomography (CT) myelography may demonstrate the lesion.

MRI can provide information regarding tumor signal intensity and contrast enhancement. Because MRI has multiplanar imaging capability, the extra-axial location of a meningioma is illustrated clearly.




MRI is contraindicated in patients with pacemakers, certain types of aneurysm clips, metallic foreign bodies in the eye and elsewhere. Patients with claustrophobia may have difficulty holding still in the MRI unit long enough to complete the examination.

Radiography

Plain radiographic findings are usually normal. On occasion, localized widening of the canal may be seen. In rare cases, spinal meningiomas may have an extradural component, which can cause enlargement of the neuroforamen. Calcifications are rarely visible on plain radiographs (1-5%) and usually psammomatous in nature.


On plain images, the degree of confidence is low.

Computed Tomography

CT scans obtained without the intravenous injection of contrast material occasionally demonstrate a hyperattenuating lesion resulting from psammomatous calcification or dense tumor tissue. CT scans obtained with the intravenous injection of contrast material may show a homogeneous enhancing tumor. CT image of spinal meningioma is provided below.






Sagittal reformation nonenhanced CT scan shows a calcified mass in the spinal canal.

Myelography or CT myelography is required to demonstrate the intradural extramedullary location of the mass.

The spinal cord is displaced away from the lesion and usually compressed. A sharp meniscus is seen where the contrast agent caps the lesion from above and below. The subarachnoid space on the side of the lesion is widened.


On CT scans, the degree of confidence is moderate.


MRI demonstrates the intradural extramedullary location of meningiomas. Lesions are usually isointense to spinal cord on both T1-weighted and T2-weighted images. Lesions are sometimes hypointense on T1-weighted images and hyperintense on T2-weighted images. Homogeneous intense enhancement of the lesion is seen after an intravenous injection of gadolinium-based contrast agent.

Most spinal meningiomas demonstrate broad-based dural attachment. On occasion, a densely calcified meningioma may demonstrate hypointensity on T1-weighted and T2-weighted images. The spinal cord is displaced away from the lesion and usually compressed. The subarachnoid space above and below the lesion is widened, and a meniscus capping the lesion may be seen.

MRI images of spinal meningioma are provided below.


Intradural extramedullary meningioma in the lower thoracic region. Sagittal nonenhanced T1-weighted MRI demonstrates an isointense mass compressing the lower spinal cord.

Sagittal T2-weighted MRI shows an isointense mass lesion that compresses the cord.

Sagittal T1-weighted contrast-enhanced MRI demonstrates an intensely enhancing intradural extramedullary mass lesion with dural attachment.

Axial T1-weighted contrast-enhanced MRI shows a right-sided intradural extramedullary enhancing mass compressing and displacing the cord to the left.


Spinal meningioma with intradural, extramedullary, and extradural components. Sagittal nonenhanced T1-weighted MRIs show a lesion isointense to the spinal cord. Low signal intensity is seen involving the C6 vertebral body, consistent with bony sclerosis.

Axial T2-weighted MRI shows a mixed-intensity lesion on the right side of the spinal canal extending through the right neuroforamen. Curvilinear low signal intensity in the mass lesion results from calcification. The spinal cord is compressed and displaced to the left side.

Sagittal contrast-enhanced T1-weighted MRIs show an intensely enhancing mass compressing the cervical cord. Enhancement of the posterior portion of the C5 vertebral body results from tumor invasion.

Coronal T1-weighted MRI shows a dural-based enhancing mass lesion with a small component extending into the right neuroforamen.



On MRI, the degree of confidence is high.


A meningioma with intradural and extradural components occasionally mimic a nerve sheath tumor, or a nerve sheath tumor with a predominant intradural component may mimic a meningioma. However, nerve sheath tumors usually have hyperintensity on T2-weighted images, whereas meningiomas usually are isointense to the spinal cord on T2-weighted images. Most meningiomas are lateral or dorsal, whereas most nerve sheath tumors are ventral. Furthermore, a mass lesion with both intradural and extradural components is most likely to be a nerve sheath tumor.

Ultrasonography

Intraoperative ultrasonography may be performed after laminectomy as a tool to localize the mass, which is usually echogenic.

Angiography

Spinal angiography usually shows a hypervascular lesion with tumor blush. More important, spinal angiography is performed to identify the location of the artery of Adamkiewicz, which is usually in the lower thoracic region, most frequently on the left side. Care must be taken not to damage the artery during surgery because the artery supplies the spinal cord. Spinal angiography is performed for surgical planning if the meningioma is in the lower thoracic region, regardless of the side of the meningiom



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