articles magnetic imaging neurological disorders · (ctm). thestudyaimswereto lookat the role...

Archives ofDisease in Childhood 1990; 65: 922-929

ORIGINAL ARTICLES

Magnetic resonance imaging in neurologicaldisorders

Alun C Elias-Jones, Timothy Jaspan, David H Mellor, Brian S Worthington

AbstractTo investigate the role of magnetic resonanceimaging (MRI) in neurological disorders, 115children were studied in two groups. Group A(78 patients) was studied by paired computedtomography and MRI cranial scans. Group B(37 patients) was studied by paired computedtomography assisted myelography (CTM) andMRI spinal scans. In group A, the scans weregenerally equivalent for supratentorial tumoursand for investigating fits, hydrocephalus,benign intracranial hypertension, and cerebralatrophies, but MRI scanning was superior forposterior fossa tumours and cysts. In group B,MRI scans were superior for intrameduliaryspinal tumours, spinal dysraphic problemswith tethering or syrinx, and were comple-mentary to CTM in diastematomyelia.

The advent of magnetic resonance imaging(MRI) has provided a further powerful tool forthe investigation of diseases of the centralnervous system. Current limited availability ofscanning time and of health service resources,however, makes the prudent selection ofpatients for its use imperative.

Consequently, this study was devised tocompare the usefulness of MRI cranial andspinal scans with cranial computed tomographyand computed tomography assisted myelography(CTM). The study aims were to look at the roleof MRI in childhood neurological disorders, tocompare the accuracy of diagnosis with com-puted tomograms, and to identify the patho-logical entities where specific scanningmodalities are preferable, and others where themodalities are equivalent or complementary.Thus the study hoped to identify the mostappropriate initial investigation in certain clini-cal situations.

then compared with the final clinical diagnosis.The scans were then graded for diagnostic valueaccording to the following classification: grade1-both scans were negative (normal); grade2-both scans were positive and equivalent;grade 3-the MRI scan was superior to thecomputed tomogram; grade 4-the computedtomogram was superior to the MRI scan.Informed parental consent was obtained

before both computed tomography and MRIscanning.

ResultsThe results from comparing the radiological

PU

University Hospital,Queens Medical Centre,Nottingham NG7 2UH,Department ofPaediatricsAlun C Elias-JonesDavid H MellorDepartment of RadiologyTimothy JaspanBrian S WorthingtonCorrespondence to:Dr Elias-Jones.Accepted 13 February 1990

Subjects and methodsOne hundred and fifteen children (60 girls and55 boys) aged 2 days-17 years (mean 9-2 years)were studied. In group A, 78 children werestudied with paired computed tomograms andMRI cranial scans. The scans were performedon the same day in most children, and all withintwo weeks of each other. In group B, 37children were studied with paired CTM andMRI spinal scans. The imaging units used werethe Picker 1200SX for computed tomographyand a Picker 0-15 Tesla Resistive System forMRI scanning.The scans in both groups were reported by

the same neuroradiologist who was given theclinical details. The radiological diagnosis was

Figure 1 An 8year old girl. (a) Computed tomogramshowing tumour extension into the left geniculate region(curved arrow) ofhistologically proved optic chiasm glioma.(b) T2 weighted (TR=2000 msec, TE=80 msec) sagittalMRI scan demonstrating a large suprasellar high signalmass. As axial images were not obtained the posteriorextension was not appreciated.

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Magnetic resonance imaging in neurological disorders

Table I Results of group A: computed tomography and MRI cranial scans

Pathology Both scans Both scans MRI Computed Totalnegative positive superior tomography(grade 1) (grade 2) (grade 3) superior

(grade 4)

(1) Tumours:(a) Supratentorial - 16 4 1 21(b) Infratentorial 1 5 8 - 14

(2) Cysts - 2 3 - 5(3) Hydrocephalus or benign intracranial

hypertension 1 8 - - 9(4) Atrophic states - 3 - - 3(5) Degenerative states - 3 2 - 5(6) Fits 8 3 - - 11(7) Miscellaneous neurological disorders 7 1 2 - 10

Total 17 41 19 1 78

(a)

(c) (d)Figure 2 A 12year old girl. (a)Axial computed tomogram through the posteriorfossa. An intrinsic lesion is inferred by thepresence oftissue bulging into the right side ofthefourth ventricle (arrows); however, tumour defintion is poor. (b)Axial and(c) sagittal T2 weighted (TR=2000 msec, TE=80 msec). (d) Coronal TI weighted inversion recovery (TR= 1660 msec,TI -400 msec) section clearly defines the lesion (arrows) and localises it within the brainstem and involves the right middlecerebellarpeduncle (histology: brainstem glioma).

diagnosis and the final clinical diagnosis madeon discharge for the two groups are shown intables 1 and 2.

GROUP A (TABLE 1)(la) Tumours-supratentorialThere were 21 children with suspected supra-tentorial tumours. The scans in 16 (76%) cases

were judged to be equivalent, whereas in four(19%) patients the MRI was superior in definingthe anatomy and extent of the tumour. Thesefour tumours included single cases of pilocyticastrocytoma, choroid plexus carcinoma, opticchiasm glioma, and mid brain glioma. Thesingle case where the computed tomogram wasadjudged to be superior had an optic chiasmpilocytic astrocytoma. The computed tomo-

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(a)

Figure 3 A 7year old boy. (a) Axial computed tomography section. Appreciable atrophy is present but no definiteparenchymal lesion is seen. (b) Axial T2 weighted (TR=2000 msec, TE=80 msec) section shows multiplefoci ofhigh signalin the subcortical white matter ofboth cerebral hemispheres.

Table 2 Results of group B: paired CTM and MRI spinal scans

Pathology Both scans Both scans MRI CTM Totalnegative positive superior superior(grade 1) (grade 2) (grade 3) (grade 4)

(1) Spina bifida aperta/cystica - 6 10 16(2) Diastematomyelia - 3 - - 3(3) Tight filum terminale syndrome (±syrinx) - 1 3 1 5(4) Spinal tumours (+syrinx) - 2 3 1 6(5) Miscellaneous spinal disorders 3 1 3 - 7

Total 3 13 19 2 37

gram showed posterior extension of the tumouralong the optic tract. This extension was notwell visualised on MRI, which had given theerroneous diagnosis of a hypothalamic glioma(fig 1). The appropriate use of axial magneticresonance images, however, would probablyhave demonstrated clearly the full extent of thelesion along the specific pathways.

(lb) Tumours-infratentorialThe 14 children with suspected infratentorialtumours included a boy with symptoms ofheadache, ataxia, and nystagmus in whom bothscans were negative and his symptoms subse-quently resolved. In the remaining 13 childrenthe studies were judged to be equivalent in five(39%) (three medulloblastomas, one brain stem

(a) (b)(b)Figure 4 A 13year old girl. (a) Immediate postmyelographic axial computed tomogram through LS. Neural (short curved arrow) and lipomatous (long curvedarrow) tissue is seen to pass posteriorly into a meningocele (straight arrow). Nerve roots can be seen arisingfrom the anterior surface ofthe low cord. (b) Tiweighted (TR=500 msec, TE=40 msec) sagittal scan. The relationship ofthe higher signal lipomatous tissue (short curved arrows) can be clearly seen, lying onthe dorsal surface ofthe cord (long curved arrow), both passing posteriorly into the bilobed meningocele.

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(b)Figure S A 3year old girl. (a) Anterior-posterior viewfrom myelogram showing the classicalappearances ofa double aracknoid-dural sac diastematomyelia with an interposed bone spur(arrow). The cord above the split appears a little bulky. (b) Postmyelographic computedtomogram through the cord at the T12 level shows no obvious abnormality. Delayed scanningwas not performed. (c) Ti weighted (TR=S00 msec, TE=40 msec) sagittal scan demonstratesa septated sringohydromyelic cavity in the cord above the cleft (curved arrow). Thefibro-osseous spur (straight white arrow) is seen. An unsuspectedfilar lipoma (straight blackarrmow) is noted.

glioma, one juvenile astrocytoma) and the MRIwas superior in eight (62%) (three cerebellarastrocytomas (fig 2), two medullary astro-cytomas, and single cases of medulloblastoma,brain stem glioma, and a tectal plate glioma). Inall cases where a tumour was present, however,an abnormality was picked up by both imagingmodalities.

(2) CystsFive patients had cystic lesions, of which four

were arachnoid cysts. In three the MRI scanwas judged to be superior, defining the compli-cated anatomical connections particularly whenthe posterior fossa was involved.

(3) Hydrocephalus or benign intracranialhypertenswnNine children had suspected hydrocephalus orbenign intracranaial hypertension. In the onepatient with benign intracranial hypertensionboth scans were normal. In the remaining eightcases with hydrocephalus abnormalities weredetected equally well by both techniques.

(4) Atrophic statesThree children had atrophic states clearlydemonstrated by either scan.

(5) Degenerative statesFive children were investigated for suspecteddegenerative disorders, of whom in one caseeach of Krabbe's leucodystrophy, Wilson'sdisease, and optic neuritis the scans wereequivalent. However, in two children the MRIwas superior demonstrating pathology not seenon the computed tomogram. One had Leigh'sdisease with a left medullary lesion demon-strated, and the other had florid changes ofdemyelination (fig 3) not seen on the computedtomogram.

(6) FitsEleven children were investigated for trouble-some focal fits whose electroencephalogramshad suggested an underlying structural abnor-mality. In eight both scans were normal. In theremaining three both scans identified the abnor-malities including one with tuberous sclerosis,one with cerebral atrophy, and one with cogeni-tal hamartoma.

(7) Miscellaneous neurological disordersTen children had a variety of suspected orknown neurological disorders. In seven bothscans were negative. One child had a lentiformnucleus infarct clearly seen on both scans. TheMRI was superior in two, identifying a cavumseptum pellucidum in one, and haematomassecondary to vasculitis in the other.

For the whole of group A (table 1) 58 out of78 (74%) scans were equivalent (either positiveor normal). In one child the computed tomo-gram was superior, and in 19 (24%) the MRIwas superior, particularly with posterior fossatumours and cysts and certain degenerativedisorders.

GROUP B (TABLE 2)(1) Spina bifida apertalcysticaSixteen patients were investigated after thedevelopment of new neurological signs suggest-ing cord tethering or cavitation. In six the scanswere judged to be equal, but in 10 the MRI wassuperior particularly in subjects with lipomyelo-meningoceles in the lumbosacral region (fig 4).

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(a) (b)Figure 6 A 12year old bay. (a) Postmyelographic computed tomogram shows an apparently normal distal thoracic cord. Delayed scanning was notperformed. (b) Ti weighted (TR=500 msec, TE=40 msec) scan shows a linear central syringohydromyelic cavity (arrow) in a low lying cord. The thickenedtetheringfilum terminale was better demonstrated by computed tomography.

(2) DiastematomyeliaThree patients had diastematomyelias whichwere equally well demonstrated by both imag-ing techniques. While CTM more clearlydefined the finer neural detail and fibro-osseousseptum, if present, between the two hemicords,MRI provided additional information as to thepresence of associated cord cavitation (seen intwo of the cases) (fig 5).

(3) Tight filum terminale syndromeFive children had a tight filum terminale

syndrome. In one the scans were of equivalentvalue. In three the MRI scan was superior,demonstrating an associated syrinx in two (fig6), and in the other with kyphoscoliosis showingcord thinning. A single child with arthrogryposisand scoliosis had cord tethering which was moreclearly defined by CTM.

(4) Spinal tumoursSix children had spinal tumours; in three theMRI was the superior examination (fig 7)whereas in two the studies were equal. A single

(a) (b)Figure 7 A 2year old girl. (a) Postmyelographic computed tomogram. There is diffuse expansion ofthe cord at T12, but lesion definition and tissuecharacterisation is poor. (b) TI weighted (TR=500 msec, TE=40 msec) sagittal section demonstrates a well circumscribed cystic structurefelt to represent anintramedullary dermoid, confirmed at surgery.

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(b)Figure 8 A 3year old girl. (a) Postmyelogram computed tomogram shows a small amount ofextradural soft tissue (arrows) indenting the anterior theca. Subtle end plate changes can beseen in the posterior aspect ofthe vertebral body. (b) SagittalSTIR (TR= 1100 msec,TI= 100 sec). Florid high signal is seen in the bodies ofL2 andL3 adjacent to the abnormalinterposed disc which shows signal reduction and loss ofheight, features characteristic ofdiscitis.

girl had intrathecal droplet metastases seen on

CTM that could not be demonstrated withcertainty by MRI.

(5) Miscellaneous spinal disordersThree children with bladder dysfunction or

long tract signs, or both, had normal scans. Thescans were equally informative in one child withmesodermal dysplasia. The MRI was superiorin three children, including one with cervicalcord trauma from a knife stab wound, one afterprevious scoliosis surgery with an associatedlipoma, and a girl with discitis (fig 8).

Thus in group B (table 2) the imagingtechniques were equivalent in 16 out of 37

(43%) (either positive or negative), the MRI wassuperior in 19 (51%) and CTM was better in two(5%).

DiscussionIn certain fortunate centres the availability of afull range of imaging methods enables possibleneurological problems to be investigated invarious alternative ways. In many district andreferral hospitals, however, MRI scanning, andeven computed tomography, may not be freelyavailable. Given the current concerns aboutscarce health resources it is important thatchildren are investigated by the nlost appro-priate method. We have attempted to suggestpossible guidelines for the use ofMRI scanning.The performance of both scans has possible

advantages in yielding greater certainty ofdiagnosis and providing complementary infor-mation. Greater expertise in the scanning tech-niques may also result. In addition even thoughan additional scan may not alter the diagnosis itmay well aid the neurosurgeon in planningoperative intervention such as the case shown infig 9, where the computed tomogram showed alarge enhancing mass based on the left thalamus,considered to be inoperable by the neuro-surgeon. The magnetic resonance scan, how-ever, showed a well circumscribed lesionadjacent to the skull base, which was felt to beaccessible by a subtemporal approach. This wassuccessfully done leaving the child with minordisability only.The coronal plane most nearly approximates

to the operative field in posterior fossa tumoursand the siting and extent of the necessarycraniotomy can best be assessed from suchsections. Posterior and inferior extension oftumour into the vallecula, cisterna magna, andupper cervical canal; lateral extension into thecerebellar peduncles and cerebellopontinecisterns and superior extension through thetentorial hiatus can be readily assessed from thecoronal perspective.The indiscriminate use of both scanning

methods would, however, be wasteful of oftenlimited resources with an average cost in ourunit for an enhanced computed tomogram of£155 and for an MRI cranial scan of £206.Average costs ofCTM are £312, and for an MRIspinal study £206. Performing both scans canplace an extra burden upon the patient andfamily, as well as necessitating longer hospital-isation and potentially straining the family'sresources to cover the hospital stay.

Although the numbers were not large, thisstudy showed that MRI and computed tomo-graphy cranial scans gave identical informationwhen investigating the possibility of a structurallesion in a child with epilepsy. Previous reportshave suggested the superiority ofMRI scanningin this clinical situation. 1 2Our advice would beto do computed tomography, and if the scan isnegative consider requesting an MRI scan onlyif seizures are difficult to control despite optimalanticonvulsant treatment.

Similarly, in most children with hydro-cephalus, benign intracranial hypertension, orcerebral atrophies either scanning method

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(c) (d)

Figure 9 A 7yearoldgirl. (a)Enhanced axial computed tomogram demonstratinga ratherpoorlydefined strongly enhancinglesi tn the deep left temporal region, extending to the left cerebral peduncle. (b) Coronal and (c) sagittal Ti weighted (SE500 msec, TE=40 msec) sections show a clearly defined low signal lesion (arrows). On the basis ofthe coronal scan theneurosurgeon felt that a subtemporal approach wasfeasible and a macroscopic resection obtained. (d) Six months postsurgicalTI weighted section. No tumour residuum demonstrated (pathology: juvenile pilocytic astrocytoma).

(according to the ease of availability) could beexpected to yield the same information.

Posterior fossa tumours and cysts are usuallybest investigated by MRI.=s Suspected supra-tentorial lesions can be investigated initially byeither method, although it appears that in mostcases the MRI scan will be at least as good as thecomputed tomogram.

In children with complicated spinal dysraphicabnormalities, particularly those with associatedlipomas, the MRI scans tend to be moreinformative.6 Similarly in children with intra-medullary spinal tumours the MRI scans yieldgreater information. However, subtle metastaticdeposits may be more clearly seen on CTM.

In the investigation of children with dia-stematomyelia the two methods tend to becomplementary. However, MRI is consistentlysuperior for the demonstration of unsuspectedor occult cord cavitation.

It is especially in the sphere of dysraphiclesions and assessment of childhood kypho-scoliotic states that close liaison between thereferring clinician and neuroradiologist is essen-tial to optimise the diagnostic information frommagnetic resonance scanning. The choice ofcorrect imaging parameters may considerablyenhance the accuracy of the examination. Inparticular the appropriate use ofpulse sequenceswill reduce the risk of failing to identify subdeintraspinal lesions and enable more precisetissue characterisation.

In children with degenerative disorders suchas multiple sclerosis,7 8 and for studying mye-lination disorders and patterns in infancy, MRIscanning provides clearer and more accurateinformation.9 10

This study has been based upon the compari-son between computed tomography and a lowfield (0 15 Tesla (T)) MRI system. It is accepted

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that imaging employing mid or high fieldsystems considerably improves the diagnosticaccuracy and resolution capabilities of thismodality. The field homogeneity at 0-15T issuboptimal and the inability to obtain cardio-respiratory gating produced relatively poorquality imaging in the spine. The wider use ofhigher field systems will lead to improved spinalimaging especially when coupled with fastsequences and improved surface coils. Anadvantage of a low field system has been theability to perform general anaesthetics withminimal modification of the equipment. Mostpatients scanned in our study, however, weregiven oral sedation only. Where possible selec-tion of the shorter TI weighted spin echosequences enabled a reduction in the overallscan time.

Since this study the introduction ofgadoliniumdiethylene triamine pentacetic acid (DTPA) hasconsiderably improved the imaging capabilitiesof MRI with the ability to define intrinsic andextrinsic central nervous system pathology withgreater sensitivity. It is foreseen that this willlead to the more frequent use of MRI scanningin the neuraxis.

In conclusion, where MRI imaging is notfreely available, we would recommend that it isbest reserved for children with a suspectedposterior fossa tumour or cyst, for complicated

spinal abnormalities, and for certain suspecteddegenerative disorders. Furthermore, MRIenables the use of potential frequent or serialscanning without the attendant risks of a heavyradiation burden to this young group of patients.

We thank Mr J Punt, Mr T Hope, and Mr J Firth for permissionto study children who were under their care.

1 Triulzi F, Franceschi M, Fazio F, Del Maschio A. Non-refractory temporal lobe epilepsy: 1.5T MR imaging.Radiology 1988;166:181-5.

2 Lesser RP, Modic MT, Weinstein MA, et al. Magneticresonance imaging (1.5 Tesla) in patients with intractablefocal seizures. Arch Neurol 1986;43:367-71.

3 Gentry LR, Jacoby CG, Turski PA, Houston LW, StrotherCM, Sackett JF. Cerebellopontine angle-petromastoid masslesions: comparative study of diagnosis with MR imagingand CT. Radiology 1987;27:301-3.

4 Holland BA, Brant-Zawadzki M, Norman D, et al. Magneticresonance imaging of primary intracranial tumours: areview. Int J Radiat Oncol Biol Phys 1985;11:315-21.

5 Kjos BO, Brant-Zawadzki M, Kucharczyk W, Kelly W,Norman D, Newton TH. Cystic intracranial lesions:magnetic resonance imaging. Radiology 1985;155:363-9.

6 Jaspan T, Worthington BS, Holland IM. A comparativestudy of magnetic resonance imaging and computedtomography-assisted myelography in spinal dysraphism. BrJ Radiol 1988;61:445-53.

7 Scotti G, Scialfa G, Biondi A, et al. Magnetic resonance inmultiple sclerosis. Neuroradiology 1986;28:319-23.

8 Jacobs L, Kinkel WR, Polachini I, Kinkel RP. Correlationsof nuclear magnetic resonance imaging, computerizedtomography and clinical profiles in multiple sclerosis.Neurology 1986;36:27-34.

9 Holland B, Haas D, Norman D, et al. MRI of normal brainmaturation. American Jowunal of Neuroradiology 1986;7:201-8.

10 Barkovich AJ, Kjos BO, Jackson DE, Norman D. Normalmaturation of the neonatal and infant brain; MR imaging at1.5T. Radiology 1988;166:173-80.


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