1. Topics Normal anatomy and contents of the mediastinum
Clinical manifestations produced by diseases and lesions in the region
Diagnostic evaluation and techniques for imaging the mediastinal contents and methods for obtaining tissue for cytologic and histologic examination

2. 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 - parietal pleura
Anterior - sternum
Posterior - vertebral column and paravertebral gutters
Superior thoracic inlet
Inferior - diaphragm

3. Mediastinal Anatomy

4. The Mediastinum

5. MEDIASTINUM IN CROSS SECTION

6. 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

7. 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

8. 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

9. Normal Mediastinum
There are some authors that consider the most superior portion of the anterior mediastinum as a separate, fourth compartment
Other authors divide it into 7 groups
1. Thoracic inlet, 2. anterior mediastinum, 3. super aortic area, 4. infra aortic area, 5. supra azygos area, 6. infra azygos area and 7. hila

10. 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

11. 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

12. 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

13. 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

14. Clinical Presentation
Systemic symptoms and syndromes
Fever, anorexia, weight loss and other non specific symptoms of malignancy and granulomatous inflammation

15. 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

16. Mediastinitis Acute inflammation of the mediastinum
Substernal chest pain, chills, high fever, prostration

17. Techniques for visualizing the mediastinum and its content
Radiographic technique
Standard postero antero and lateral views
Most mediastinal tumors are discovered
Fluoroscopy and tomography

18. 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%

19. 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

20. 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

21. 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

22. Ultrasonography For cystic nature of mediatinal mass
Useful in guiding endoscopic biopsy technique

23. 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

24. 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

25. 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.

26. Mediastinoscopy
Allows direct inspection and biopsy of lymph nodes or other masses on the superior portion of the anterior mediastinum

27. MEDIASTINOSCOPY Paratracheal (station 4)
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

28. MEDIASTINOSCOPY