The mediastinum BY Dr Nikhil Bansal

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The mediastinum Radiology by Dr Nikhil Bansal

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The mediastinum BY Dr Nikhil Bansal

  1. 1. The Mediastinum By Dr Nikhil Bansal
  2. 2. Introduction • Mediastinal disease is usually initially demonstrated on a CXR and appear as a mediastinal soft tissue mass, widening or pneumomediastinum. • However it may appear normal in the presence of mediastinal disease which is subsequently clearly demonstrated by CT or MRI.
  3. 3. NORMAL ANATOMY
  4. 4. Mediastinal Boundaries Compartment Anteriorly Posteriorly Anterior Sternum Anterior aspect of trachea and posterior margin of heart Middle Anterior aspect of trachea and posterior margin of heart A vertical line drawn along the thoracic vertebrae 1 cm behind their anterior margins Posterior Vertical line drawn along the thoracic vertebrae 1 cm behind their anterior margins Costovertebral junction A M P
  5. 5. Mediastinal Contents Compartment Main Strictures Anterior Fat, lymph nodes, thymus, heart, ascending aorta Middle Trachea, bronchi, lymph nodes, oesophagus, descending aorta Posterior Para vertebral soft tissues Mediastinal Masses Compartment % Malignant Anterosuperior 59 Middle 29 Posterior 16
  6. 6. Approach 1. Is the mass actually in the mediastinum or is it in the lung? 2. If in the mediastinum, then in which compartment? 3. What is the differential diagnosis for the mass?
  7. 7. • PA and lateral chest films are the first step in distinguishing from which mediastinal compartment the mass is arising from. • CT & MRI is the next step, better characterizing the nature and extent of the lesion, thus narrowing the differential diagnosis. MRI is especially good at looking for spinal canal invasion in posterior mediastinal masses • Tissue biopsy is required for definitive diagnosis, and surgical resection for definitive cure. Investigations
  8. 8. Clues to locate mass to mediastinum Mediastinal masses are lined by parietal pleura, so will have: Masses in the lung parenchyma typically: – Smooth contour – Tapered borders – May be seen bilaterally – Are surrounded by air – May contain air bronchograms – Will be on one side only
  9. 9. Which compartment? 1. Cervicothoracic sign 2. Thoracoabdominal sign 3. Hilum overlay and convergence signs 4. Effect on adjacent structures  Trachea  Ribs  Heart
  10. 10. Cervicothoracic sign • Described by Felson: ▫ “If a thoracic lesion is in anatomic contact with the soft tissues of the neck, its contiguous border will be lost.” • The anterior mediastinum ends at the level of the clavicles. • The posterior mediastinum extends much higher. • Therefore ▫ any mass that remains sharply outlined in the apex of the thorax must be posterior and entirely within the chest, and ▫ any mass that disappears at the clavicles must be anterior and extends into neck
  11. 11. Cervicothoracic sign Which compartment do you think this mass is in?
  12. 12. Click for lateral view
  13. 13. See sharp margin above clavicle Click for lateral view
  14. 14. Click for answer
  15. 15. Click for answer This should help!
  16. 16. Cervicothoracic sign • Answer: Mass is in posterior mediastinum. We know because it remains sharply outlined in apex of thorax, indicating that it is surrounded by lung. • This particular example is a ganglioneuroma
  17. 17. Cervicothoracic sign Which compartment do you think this mass is in?
  18. 18. Click for answer
  19. 19. Mass “disappears” at clavicle Click for answer
  20. 20. Cervicothoracic sign • Answer: Mass lies in anterior mediastinum. We know this because it disappears at the level of the clavicle where it extends into the neck. • This particular example is Non-Hodgkins lymphoma
  21. 21. Thoracoabdominal sign • A sharply marginated mediastinal mass seen through the diaphragm must lie entirely within the chest. • The posterior costophrenic sulcus extends far more caudally than the anterior aspect of the lung • Therefore ▫ Any mass that extends below the dome of the diaphragm and remains sharply outlined must be in the posterior compartments and surrounded by lung, and ▫ Any mass that terminates at dome of diaphragm must be anterior
  22. 22. Click for answer
  23. 23. Can you see the outline of the mass below the diaphragm? Click for answer
  24. 24. Thoracoabdominal sign • Answer: Margin of mass is apparent and below diaphragm, therefore this must be in the middle or posterior compartments where it is surrounded by lung • This example is a ‘Lipoma’
  25. 25. Hilum overlay and convergence signs • Principle of hilum overlay ▫ The proximal segments of the R and L main pulmonary arteries lie lateral to the cardiac silhouette on PA film • With pericardial effusion or cardiac enlargement, this relationship is unchanged • An anterior mediastinal mass will overlap the main pulmonary arteries, therefore they will be seen within the margins of the mass • Hilum convergence ▫ To distinguish between enlarged pulmonary artery and mediastinal mass • If branches of the pulmonary artery converge toward a central mass enlarged PA • If branches of PA converge toward the heart rather than the central mass mediastinal tumor
  26. 26. Hilum overlay sign Can you see the pulmonary arteries on the following radiograph?
  27. 27. Click for answer
  28. 28. Hilum can be seen through mass Click for answer
  29. 29. Hilum overlay sign • Answer: this must be an anterior mediastinal mass because it overlaps rather than “pushes out” the main pulmonary arteries • This particular example is a thymoma
  30. 30. Can you see the pulmonary arteries on the following radiograph?
  31. 31. Yes!! Click for more info
  32. 32. Hilum overlay sign • Heart is enlarged, but hilar vessels still visible lateral to the cardiac silhouette • This case is pericardial effusion
  33. 33. Effect on adjacent structures • Trachea ▫ May see deviation or narrowing of trachea with anterior compartment masses • Ribs/ vertebrae ▫ May see bony destruction with posterior compartment masses
  34. 34. Anterior Mediastinal Masses (30% of mediastinal masses) • The 4 T‟s ▫ Thymoma  Generally over age 40 ▫ Teratoma  Generally under age 40 ▫ Thyroid  Goiter or neoplasm ▫ Terrible lymphoma
  35. 35. Thymoma • Clinical clues ▫ 70% of cases in patients ages 40-60 ▫ Associated with  myasthenia gravis (in 50%)  pure red cell aplasia (in 5%)  Hypogammaglobulinemia (in 5%) ▫ Asymptomatic in 20-50% ▫ 35% are invasive ▫ Tx: resection + RT if invasive • Radiographic clues ▫ Often overlies aortopulmonary window ▫ Punctate, ringlike calcification in 20% ▫ Usually seen unilaterally ▫ 25-50% are undectectable on CXR  CT is better at 91% sensitivity
  36. 36. Thymic cyst • May be congenital or acquired. • On plain radiographs, thymic cysts are indistinguishable from other nonlobulated thymic masses, notably thymomas. • CT scans show a well-defined cystic mass demonstrating CT attenuation values typically consistent with fluid. The appearance, however, may vary if haemorrhage or infection complicate the cyst. Curvilinear calcification of the cyst wall may occur in a few cases.
  37. 37. Teratoma • Clinical clues ▫ Most patients < 30 y.o. ▫ 50-75% symptomatic with cough, dyspnea, chest pain • Radiographic clues ▫ Well-defined, rounded or lobulated mass ▫ May contain calcification, teeth or fat ▫ Commonly have fluid- containing cystic areas
  38. 38. Eight year old male with a heart murmur
  39. 39. ▫ PA and lateral chest films show a large anterior mediastinal mass causing narrowing and rightward deviation of the trachea. The mass is not calcified.
  40. 40. CT exam show a low density mass in the anterior mediastinum with irregular walls with calcium in it. Dx Teratoma, Anterior Mediastinal
  41. 41. Thyroid goiter • Clinical clues ▫ Affect females > males (3:1) ▫ Account for 10% of anterior mediastinal masses ▫ Usually asymptomatic • Radiographic clues ▫ + cervicothoracic sign ▫ Often displace or narrow trachea ▫ Calcification seen in 25%, and is dense and well- defined
  42. 42. Thyroid goiter Trachea is deviated to left Mass disappears at level of clavicle
  43. 43. Lymphoma • Clinical clues ▫ Hodgkins (Reed-Sternberg cells) ▫ Bimodal distribultion: in 20s and at age >50 ▫ Account for only 20-30 of all lymphomas but accounts for up to 85% mediastinal lymphoma ▫ 20-30% pts have “B” sx ▫ Non-Hodgkins ▫ Age > 55 ▫ Accounts for 80% of lymphomas but only 20% present as mediastinal mass • Radiographic clues ▫ Identical findings for Hodgkins and Non-Hodgkins lymphoma ▫ Mass may be multi-lobular ▫ Usually affects multiple nodes ▫ Often extends beyond anterior compartment ▫ Calcification rare prior to treatment
  44. 44. Mass disappears at level of clavicle
  45. 45. PA and lateral chest films show a large, lobulated anterior mediastinal mass displacing the trachea to the right. Twelve year old female with a chest mass
  46. 46. A chest CT exam shows the mass to extend from the neck to the diaphragm, compressing the tracheal and left mainstem bronchus leading to left lower lobe atelectasis. The chest wall mass is partially eroding the sternum and there is periosteal reaction. Axillary adenopathy is present also. Dx:Lymphoma, Hodgkin, Anterior Mediastinal, Sternal Involvement
  47. 47. PA and lateral chest films show an anterior mediastinal mass and a large right pleural effusion.
  48. 48. Two contiguous slices from an enhanced chest CT exam show a homogenous, solid, anterior mediastinal mass and a large right pleural effusion. Dx-Lymphoma, Non- Hodgkin, Anterior Mediastinal
  49. 49. Germ Cell Tumours It is a well defined round or oval soft tissue mass, which usually project to only one side of the anterior mediastinum. The soft tissue mass may also contain a peripheral rim or central nodular calcification or even a rudimentary tooth. A rapidly increase in the size of the mass show internal hemorrhage or development of malignancy.
  50. 50. Fat Deposition There is smooth widening of the superior mediastinum without trachial displacement. Pleuropericardial cyst: They appear as a well defined round, oval or triangular soft tissue mass which can alter in shape on respiration.
  51. 51. Anterior and middle mediastinal lymph node enlargement
  52. 52. Thoracic aorta aneurysm
  53. 53. Middle Mediastinal Masses (30% of mediastinal masses) • The 4 A‟s ▫ Adenopathy  TB/fungal  Sarcoid  Neoplasm (bronchogenic CA, mets, lymphoma, leukemia)  Infections (EBV, AIDS) ▫ Awful primary neoplasm  Tracheal, esophageal ▫ Aneurysm/vascular ▫ Abnormalities of development  Bronchogenic cyst- often between carina and esophagus  Pericardial cyst  Esophageal duplication cyst
  54. 54. Three year old male with an incidentally noted chest mass
  55. 55. ▫ Single slice from an enhanced chest CT exam shows the mass to be non-enhancing, posterior to the right bronchi, and next to the esophagus. ▫ Dx: Esophageal Duplication
  56. 56. Eighteen year old female with an incidentally noted chest mass
  57. 57. Esophageal duplication cyst
  58. 58. Bronchogenic cysts • On the chest radiograph, bronchogenic cysts typically appear as smooth, sharply marginated mediastinal masses. On CT scans they appear as round or oval homogeneous masses with well-defined margins with barely or no perceptible walls.
  59. 59. Paratracheal Cystic Lesion
  60. 60. Posterior Mediastinal Masses: (40% of mediastinal masses) • Neurogenic tumors most common ▫ Sympathetic ganglion tumors: neuroblastoma, ganglioneuroma ▫ Nerve root tumors: schwannoma, neurofibroma • Less common ▫ Vertebral body abscess or tumor ▫ Vascular: aneurysm or hematoma ▫ Developmental: Bochdalek hernia
  61. 61. Neural tumors • Clinical ▫ 70-80% are benign ▫ 50% of pts are asymptomatic ▫ Schwannoma is the most common ▫ Tx: resection • Radiographic findings ▫ Well-defined mass with a smooth or lobulated outline ▫ Can be very large ▫ +/- calcification
  62. 62. Posterior mediastinal mass What is the finding in the following radiograph?
  63. 63. Click to see lateral view
  64. 64. Can easily see posterior location
  65. 65. Posterior mediastinal mass What is it? „Shwannoma‟
  66. 66. PA and lateral chest films show a mediastinal mass that had enlarged in the 4 year interval that may be spreading the right 5th and 6th ribs apart.
  67. 67. • An enhanced chest CT exam shows a homogeneous mass, of fatty density, with a few septations, in the right posterior mediastinum causing some anterior displacement of the right main stem bronchus. • Dx:Lipoma, Posterior Mediastinal
  68. 68. Descending aorta aneurysm
  69. 69. Bochdalek hernia
  70. 70. Thank You
  71. 71. PA and lateral chest films show a soft tissue mass in the right posterior costophrenic sulcus.
  72. 72. Final Diagnosis: Intrathoracic Kidney
  73. 73. PA and lateral chest films from the day of admission demonstrate a large round opacity in the left lower lobe that abuts the diaphragm
  74. 74. Two coronal T1 weighted images and one axial T2 weighted image from an MRI exam from the 5th hospital day demonstrate a posterior mediastinal mass that extends into the retrocrural regions of the chest bilaterally and that enhances uniformly. There is no evidence of metastatic disease. Dx-Sequestration, Extralobar
  75. 75. large mass in the posterior mediastinum on the left.
  76. 76. Bone window images from a chest CT exam from the day of diagnosis demonstrate a large spherical calcified left paravertebral mass measuring 12 x 11 x 8 cm in size. There is a pleural effusion and a shift of mediastinal structures to the right. The mass appears to extend via the retrocrural space into the abdomen causing displacement of the left kidney and inferior vena cava. The mass crosses the midline. Some minimal thoracic vertebral body remodeling and rib thinning is seen on the left. No spinal canal invasion or liver metastases are seen
  77. 77. MRI exam performed 3 weeks after diagnosis. Coronal and sagittal T1 weighted images without contrast, and coronal and axial T2 weighted MRI images could not definitely identify the left adrenal gland, and therefore suggested it could be the origin of the midline mass. There was evidence of tumor invasion into several neural foramina and the spinal canal. Dx-Neuroblastoma

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