Mediastinium

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Introduction
 The mediastinum is the region in the chest
between the pleural cavities that contain the
heart and other thoracic viscera except the lungs
 Boundaries
 Lateral
 Anterior
 Posterior
 Superior
 Inferior
- parietal pleura
- sternum
- vertebral column and paravertebral
gutters
-thoracic inlet
- diaphragm
Mediastinal Anatomy
The Mediastinum
Normal Mediastinum
 Anterior mediastinum
 Everything lying forward of and superior to the heart shadow
 Boundaries
 Sternum, first rib, imaginary curved line following the anterior
heart border and brachiocephalic vessels from the diaphragm to the
thoracic inlet
 Contents
 Thymus gland, substernal extension of the thyroid and parathyroid
gland and lymphatic tissues
Normal Mediastinum
 Middle mediastinum
 Dorsal to the anterior mediastinum, extends from the lower edge
of the sternum along the diaphragm and then cephalad along the
posterior heart border and posterior wall of the trachea
 Contents
 Heart, pericardium, aortic arch and its major branches, innominate
veins and superior vena cava, pulmonary arteries and hila, trachea,
group of lymph nodes, phrenic and upper vagus nerve
Normal Mediastinum
 Posterior Mediastinum
 Occupies the space between the back of the heart and trachea and
the front of the posterior ribs, and paravertebral gutter
 It extends from the diaphragm cephalad to the first rib
 Contents
 Esophagus, descendng aorta, azygos and hemiazygos vein,
paravertebral lymph nodes, thoracic duct, lower portion of the
vagus nerve and the symphathetic chain
Clinical Presentation
 Asymptomatic mass
 Incidental discovery – most common
 50% of all mediastinal mass are asymptomatic
 80% of such mass are benign
 More than half are malignant if with symptoms
Clinical Presentation
 Effects on Compression or invasion of adjacent tissues
 Chest pain, from traction on mediastinal mass, tissue invasion,
or bone erosion is common
 Cough, because of extrinsic compression of the trachea or
bronchi, or erosion into the airway itself
 Hemoptysis, hoarseness or stridor
 Pleural effusion, invasion or irritation of pleural space
 Dysphagia, invasion or direct invasioin of the esophagus
 Pericarditis or pericardial tamponade
 Right ventricular outflow obstruction and cor pulmonale
Clinical Presentation
 Superior vena cava
 Vulnerable to extrinsic compression and obstruction because it is thin
walled and its intravascular pressure is low, and relatively confined by
lymph nodes and other rigid structures
 Superior vena cava syndrome
 Results from the increase venous pressure in the upper thorax , head
and neck
 characterized by dilation of the collateral veins in the upper portion of
the head and thorax and edema oand phlethora of the face, neck and
upper torso, suffusion and edema of the conjunctiva and cerebral
symptoms such as headache, disturbance of consciousness and visual
distortion
 Bronchogenic carcinoma and lymphoma are the most common
etiologies
Clinical Presentation
 Hoarseness, invading or compressing the nerves
 Horners syndrome, involvement of the sympathetic
ganglia
 Dyspnea, from phrenic nerve involvement causing
diaphragmatic paralysis
 Tachycardia, secondary to vagus nerve involvement
 Clinical manifestations of spinal cord compression
Clinical Presentation
 Systemic symptoms and syndromes
 Fever, anorexia, weight loss and other non specific
symptoms of malignancy and granulomatous
inflammation
 Pneumomediastinum
 Air in the mediastinum is a common complication of
mechanical ventilation is also commonly encountered in
some conditions
 Pain is the most common symptom
 Results from stretching of the mediastinal tissues
 Substernal and aggravated by breathing and changing position
 Dyspnea, dysphagia, subcutaneous crepitation
 Mediastinitis
 Acute inflammation of the mediastinum
 Substernal chest pain, chills, high fever, prostration
Techniques for visualizing the mediastinum
and its content
 Radiographic technique
 Standard postero antero and lateral views
 Most mediastinal tumors are discovered
 Fluoroscopy and tomography
Computed tomography
 Can identify normal anatomic variations and fluid filled
cyst
 Site of the origin of the mass can be better identified
 100% specificity for the CT appearance of teratomas,
thymolipoma, omental fat herniation
 Overall accuracy for predicting mediastinal mass is only
48%
Computed tomography
 Limitation
 Horizontal oriented structures and boundaries are difficult to
evaluate
 Abnormalities in the aortopulmonary window area and the
subcarinal area
 CT has become the initial imaging procedure of choice for
evaluation of mediastinum in patients with primary
mediastinal mass or with lung cancer
Magnetic Resonance Imaging
 Assesses tissue by measuring the radiofrequency
induced nuclear resonance instead of measuring the
attenuation of transmitted ionizing radiation
 Coronal and sagittal planes are better viewed, vertical
structures and boundaries are better evaluated
 Superior sulcus tumors, lesions invading the
medistinum, chest wall and diaphragm
 And possible invasion of the brachial plexus, and
for evaluating vertebral invasion
Magnetic Resonance Imaging
 Limitations
 Distinguish poorly between hilar mass and adjacent
collapsed or consolidated lung
 Cannot distinguish between a benign and a malignant causes
for lymph node enlargement
Ultrasonography
 For cystic nature of mediatinal mass
 Useful in guiding endoscopic biopsy technique
Radionuclide imaging
 Rely on the localization of markers based on specific
metabolic or immunologic properties of the target tissue
 Potential ability to diagnose and stage a malignancy and
identify distant metastasis
 Planar imaging with gallium 67 and thallium-201
POSITRON EMISSION TOMOGRAPHY
 The technique is not infallible because certain non-
neoplastic processes, including granulomatous and
other inflammatory diseases as well as infections,
may also demonstrate positive PET imaging
 Size limitations are also an issue, with the lower limit
of resolution of the study being approximately 7 to 8
mm depending on the intensity of uptake of the
isotope in abnormal cells
 One should not rely on a negative PET finding for
lesions less than 1 cm on CT scan
ENDOSCOPIC ULTRASOUND
 Superior ability to sample
the posterior mediastinum
through the esophageal
wall
 For patients with lung
cancer and posterior
mediastinal adenopathy
seen on chest CT scan
 EUS has a sensitivity and
specificity of 90% and
100%, respectively.
Mediastinoscopy
 Allows direct inspection and biopsy of lymph nodes or
other masses on the superior portion of the anterior
mediastinum
MEDIASTINOSCOPY
 Mediastinoscopy remains the gold standard for
invasively staging the mediastinum
 If there is mediastinal adenopathy on CT, often a
surgical mediastinal procedure is performed
 Mediastinoscopy is most often used to sample lymph
nodes in the
 Paratracheal (station 4)
 Anterior subcarinal (station 7)
 The subcarinal area is more difficult to sample and
thus has a lower yield
MEDIASTINOSCOPY
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