IntroductionIntroduction

The The mediastinum mediastinum is the region in the is the region in the chest between the pleural cavities that chest between the pleural cavities that contain the contain the heart and other thoracic heart and other thoracic viscera except the lungsviscera except the lungs

Boundaries Boundaries Lateral Lateral - parietal pleura- parietal pleura AnteriorAnterior - sternum- sternum Posterior Posterior - vertebral column and - vertebral column and

paravertebral paravertebral guttersgutters SuperiorSuperior -thoracic inlet -thoracic inlet InferiorInferior - diaphragm- diaphragm

Mediastinal AnatomyMediastinal Anatomy

The MediastinumThe Mediastinum

Normal MediastinumNormal Mediastinum

Anterior mediastinumAnterior mediastinum Everything lying forward of and superior to Everything lying forward of and superior to

the heart shadowthe heart shadow BoundariesBoundaries

Sternum, first rib, imaginary curved line following Sternum, first rib, imaginary curved line following the anterior heart border and brachiocephalic the anterior heart border and brachiocephalic vessels from the diaphragm to the thoracic inletvessels from the diaphragm to the thoracic inlet

ContentsContents Thymus gland, substernal extension of the thyroid Thymus gland, substernal extension of the thyroid

and parathyroid gland and lymphatic tissuesand parathyroid gland and lymphatic tissues

Normal MediastinumNormal Mediastinum

Middle mediastinumMiddle mediastinum Dorsal to the anterior mediastinum, extends from the Dorsal to the anterior mediastinum, extends from the

lower edge of the sternum along the diaphragm and lower edge of the sternum along the diaphragm and then cephalad along the posterior heart border and then cephalad along the posterior heart border and posterior wall of the tracheaposterior wall of the trachea

ContentsContents Heart, pericardium, aortic arch and its major branches, Heart, pericardium, aortic arch and its major branches,

innominate veins and superior vena cava, pulmonary innominate veins and superior vena cava, pulmonary arteries and hila, trachea, group of lymph nodes, arteries and hila, trachea, group of lymph nodes, phrenic and upper vagus nerve phrenic and upper vagus nerve

Normal MediastinumNormal Mediastinum

Posterior MediastinumPosterior Mediastinum Occupies the space between the back of the heart and Occupies the space between the back of the heart and

trachea and the front of the posterior ribs, and trachea and the front of the posterior ribs, and paravertebral gutterparavertebral gutter

It extends from the diaphragm cephalad to the first rib It extends from the diaphragm cephalad to the first rib ContentsContents

Esophagus, descendng aorta, azygos and hemiazygos Esophagus, descendng aorta, azygos and hemiazygos vein, paravertebral lymph nodes, thoracic duct, lower vein, paravertebral lymph nodes, thoracic duct, lower portion of the vagus nerve and the symphathetic chain portion of the vagus nerve and the symphathetic chain

Clinical PresentationClinical Presentation

Asymptomatic massAsymptomatic mass Incidental discovery – most commonIncidental discovery – most common 50% of all mediastinal mass are asymptomatic50% of all mediastinal mass are asymptomatic 80% of such mass are benign80% of such mass are benign More than half are malignant if with More than half are malignant if with

symptomssymptoms

Clinical PresentationClinical Presentation

Effects on Compression or invasion of adjacent Effects on Compression or invasion of adjacent tissuestissues

Chest painChest pain, from traction on mediastinal mass, tissue , from traction on mediastinal mass, tissue invasion, or bone erosion is commoninvasion, or bone erosion is common

CoughCough, because of extrinsic compression of the , because of extrinsic compression of the trachea or bronchi, or erosion into the airway itselftrachea or bronchi, or erosion into the airway itself

Hemoptysis, hoarseness or stridorHemoptysis, hoarseness or stridor

Pleural effusion, invasion or irritation of pleural spacePleural effusion, invasion or irritation of pleural space

Dysphagia, invasion or direct invasioin of the Dysphagia, invasion or direct invasioin of the esophagusesophagus

Pericarditis or pericardial tamponadePericarditis or pericardial tamponade

Right ventricular outflow obstruction and cor Right ventricular outflow obstruction and cor pulmonalepulmonale

Clinical PresentationClinical Presentation

Superior vena cavaSuperior vena cava Vulnerable to extrinsic compression and obstruction Vulnerable to extrinsic compression and obstruction

because it is thin walled and its intravascular because it is thin walled and its intravascular pressure is low, and relatively confined by lymph pressure is low, and relatively confined by lymph nodes and other rigid structuresnodes and other rigid structures

Superior vena cava syndromeSuperior vena cava syndrome Results from the increase venous pressure in the Results from the increase venous pressure in the

upper thorax , head and neck upper thorax , head and neck characterized by dilation of the collateral veins in the characterized by dilation of the collateral veins in the

upper portion of the head and thorax and edema upper portion of the head and thorax and edema oand phlethora of the face, neck and upper torso, oand phlethora of the face, neck and upper torso, suffusion and edema of the conjunctiva and cerebral suffusion and edema of the conjunctiva and cerebral symptoms such as headache, disturbance of symptoms such as headache, disturbance of consciousness and visual distortionconsciousness and visual distortion

Bronchogenic carcinoma and lymphoma are the Bronchogenic carcinoma and lymphoma are the most common etiologiesmost common etiologies

Clinical PresentationClinical Presentation

Hoarseness, invading or compressing the Hoarseness, invading or compressing the nervesnerves

Horners syndrome, involvement of the Horners syndrome, involvement of the sympathetic gangliasympathetic ganglia

Dyspnea, from phrenic nerve involvement Dyspnea, from phrenic nerve involvement causing diaphragmatic paralysiscausing diaphragmatic paralysis

Tachycardia, secondary to vagus nerve Tachycardia, secondary to vagus nerve involvementinvolvement

Clinical manifestations of spinal cord Clinical manifestations of spinal cord compressioncompression

Clinical PresentationClinical Presentation

Systemic symptoms and syndromesSystemic symptoms and syndromes

Fever, anorexia, weight loss and other non Fever, anorexia, weight loss and other non specific symptoms of malignancy and specific symptoms of malignancy and granulomatous inflammationgranulomatous inflammation

PneumomediastinumPneumomediastinum Air in the mediastinum is a common Air in the mediastinum is a common

complication of mechanical ventilation is also complication of mechanical ventilation is also commonly encountered in some conditionscommonly encountered in some conditions

Pain is the most common symptomPain is the most common symptom Results from stretching of the mediastinal Results from stretching of the mediastinal

tissuestissues Substernal and aggravated by breathing and Substernal and aggravated by breathing and

changing positionchanging position Dyspnea, dysphagia, subcutaneous Dyspnea, dysphagia, subcutaneous

crepitationcrepitation

MediastinitisMediastinitis Acute inflammation of the mediastinumAcute inflammation of the mediastinum Substernal chest pain, chills, high fever, Substernal chest pain, chills, high fever,

prostrationprostration

Techniques for visualizing the Techniques for visualizing the mediastinum and its contentmediastinum and its content

Radiographic techniqueRadiographic technique

Standard postero antero and lateral views Standard postero antero and lateral views Most mediastinal tumors are discoveredMost mediastinal tumors are discovered

Fluoroscopy and tomographyFluoroscopy and tomography

Computed tomographyComputed tomography

Can identify normal anatomic variations and Can identify normal anatomic variations and fluid filled cystfluid filled cyst

Site of the origin of the mass can be better Site of the origin of the mass can be better identifiedidentified

100% specificity for the CT appearance of 100% specificity for the CT appearance of teratomas, thymolipoma, omental fat teratomas, thymolipoma, omental fat herniationherniation

Overall accuracy for predicting mediastinal Overall accuracy for predicting mediastinal mass is only 48%mass is only 48%

Computed tomographyComputed tomography

LimitationLimitation Horizontal oriented structures and boundaries Horizontal oriented structures and boundaries

are difficult to evaluateare difficult to evaluate Abnormalities in the aortopulmonary window Abnormalities in the aortopulmonary window

area and the subcarinal areaarea and the subcarinal area

CT has become the initial imaging CT has become the initial imaging procedure of choice for evaluation of procedure of choice for evaluation of mediastinum in patients with primary mediastinum in patients with primary mediastinal mass or with lung cancermediastinal mass or with lung cancer

Magnetic Resonance Magnetic Resonance ImagingImaging

Assesses tissue by measuring the Assesses tissue by measuring the radiofrequency induced nuclear resonance radiofrequency induced nuclear resonance instead of measuring the attenuation of instead of measuring the attenuation of transmitted ionizing radiationtransmitted ionizing radiation

Coronal and sagittal planes are better viewed, Coronal and sagittal planes are better viewed, vertical structures and boundaries are better vertical structures and boundaries are better evaluatedevaluated

Superior sulcus tumors, lesions invading the Superior sulcus tumors, lesions invading the medistinum, chest wall and diaphragm medistinum, chest wall and diaphragm

And possible invasion of the brachial plexus, And possible invasion of the brachial plexus, and for evaluating vertebral invasionand for evaluating vertebral invasion

Magnetic Resonance Magnetic Resonance ImagingImaging

LimitationsLimitations Distinguish poorly between hilar mass and Distinguish poorly between hilar mass and

adjacent collapsed or consolidated lungadjacent collapsed or consolidated lung Cannot distinguish between a benign and a Cannot distinguish between a benign and a

malignant causes for lymph node enlargementmalignant causes for lymph node enlargement

UltrasonographyUltrasonography

For cystic nature of mediatinal massFor cystic nature of mediatinal mass

Useful in guiding endoscopic biopsy Useful in guiding endoscopic biopsy technique technique

Radionuclide imagingRadionuclide imaging

Rely on the localization of markers based Rely on the localization of markers based on specific metabolic or immunologic on specific metabolic or immunologic properties of the target tissueproperties of the target tissue

Potential ability to diagnose and stage a Potential ability to diagnose and stage a malignancy and identify distant metastasismalignancy and identify distant metastasis

Planar imaging with gallium 67 and Planar imaging with gallium 67 and thallium-201thallium-201

POSITRON EMISSION POSITRON EMISSION TOMOGRAPHYTOMOGRAPHY

The technique is not infallible because The technique is not infallible because certain non-neoplastic processes, including certain non-neoplastic processes, including granulomatous and other inflammatory granulomatous and other inflammatory diseases as well as infectionsdiseases as well as infections,, may also may also demonstrate positive PET imagingdemonstrate positive PET imaging

Size limitationsSize limitations are also an issue, with the are also an issue, with the lower limit of resolution of the study being lower limit of resolution of the study being approximately approximately 7 to 8 mm7 to 8 mm depending on the depending on the intensity of uptake of the isotope in intensity of uptake of the isotope in abnormal cellsabnormal cells

One should not rely on a negative PET One should not rely on a negative PET finding for lesions less than 1 cm on CT scanfinding for lesions less than 1 cm on CT scan

ENDOSCOPIC ENDOSCOPIC ULTRASOUND ULTRASOUND

Superior ability to Superior ability to sample the sample the posterior posterior mediastinummediastinum through the through the esophageal wallesophageal wall

For patients with For patients with lung cancer and lung cancer and posterior mediastinal posterior mediastinal adenopathyadenopathy seen on seen on chest CT scanchest CT scan

EUS has a sensitivity EUS has a sensitivity and specificity of and specificity of 90% and 100%, 90% and 100%, respectively.respectively.

MediastinoscopyMediastinoscopy

Allows direct inspection and biopsy of Allows direct inspection and biopsy of lymph nodes or other masses on the lymph nodes or other masses on the superior portion of the anterior superior portion of the anterior mediastinummediastinum

MEDIASTINOSCOPY MEDIASTINOSCOPY

Mediastinoscopy Mediastinoscopy remains the remains the gold standardgold standard for invasively staging the mediastinumfor invasively staging the mediastinum

If there is If there is mediastinal adenopathymediastinal adenopathy on CT, on CT, often a surgical mediastinal procedure is often a surgical mediastinal procedure is performed performed

MediastinoscopyMediastinoscopy is most often used to is most often used to sample lymph nodes in the sample lymph nodes in the Paratracheal (station 4) Paratracheal (station 4) Anterior subcarinal (station 7) Anterior subcarinal (station 7)

The subcarinal area is more difficult to The subcarinal area is more difficult to sample and thus has a lower yieldsample and thus has a lower yield

MEDIASTINOSCOPYMEDIASTINOSCOPY