Mediastinal Pathology

Mediastinal Anatomy - Compartment Command

Mediastinum: Central thorax. Classifications: Felson (CXR), ITMIG/IASLC (CT).

Felson's Compartments (Lateral CXR):

ITMIG Classification (CT-based): Prevascular, Visceral, Paravertebral compartments.

⭐ Exam Favourite: The anterior border of the middle mediastinum is the anterior aspect of the pericardium.

Anterior Mediastinum - Terrific T‑Time

📌 Mnemonic: The 5 Ts

Middle & Posterior Mediastinum - Central & Spinal Surprises

• Middle Mediastinum:
  • Lymphadenopathy: Most common.
    • Causes: Lymphoma (bulky, discrete), TB (central necrosis, rim enhancement), Sarcoidosis (bilateral hilar/paratracheal, often symmetrical), Metastases.
  • Cysts: Well-defined, fluid density (0-20 HU), non-enhancing.
    • Bronchogenic: Near carina/main bronchi, most common congenital.
    • Pericardial: Right cardiophrenic angle typically.
    • Esophageal duplication: Posterior, may compress esophagus.
  • Vascular: Aortic aneurysm, dilated pulmonary artery (e.g., in pulmonary HTN).
• Posterior Mediastinum:
  • Neurogenic Tumors: Most common primary posterior masses. Often round, sharp margins.
    • Schwannoma: Most frequent; possible cystic changes; "dumbbell" with neural foraminal extension.
    • Neurofibroma: Can be multiple in NF1.
    • Ganglioneuroma: Often larger, elongated.
  • Esophageal Pathology:
    • Tumors: Carcinoma (irregular thickening), leiomyoma (smooth submucosal).
    • Diverticula: E.g., epiphrenic (outpouching).
  • Paravertebral:
    • Extramedullary hematopoiesis: Lobulated masses in chronic anemia.
    • Infection/Abscess: E.g., TB spondylitis with paraspinal abscess.
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⭐ Neurogenic tumors are the most common primary posterior mediastinal masses.

Acute Mediastinum - Alarming Air & Anger

Pneumomediastinum (Air)

• Etiology: Spontaneous, Trauma (e.g., Boerhaave syndrome), Iatrogenic.
  • 📌 Mackler's Triad (Boerhaave): Vomiting, chest pain, subcutaneous emphysema.
• Signs: Hamman's sign (crunch), subcutaneous emphysema.
• Imaging:
  • X-ray: Continuous diaphragm sign, thymic sail sign (children), perivascular air.
  • CT: Confirms air.

⭐ Hamman's sign (mediastinal crunch) is a pathognomonic auscultatory finding in pneumomediastinum.

Mediastinitis (Anger)

• Etiology: Esophageal perforation, Post-surgical (e.g., CABG), Descending necrotizing (oropharyngeal).
• Clinical: Sepsis, chest pain.
• Imaging (CT): Fluid collections, gas bubbles, fat stranding, abscess, effusions.

High‑Yield Points - ⚡ Biggest Takeaways

• Anterior Mediastinum: Remember the 4 T's (Thymoma, Teratoma, Thyroid, Terrible Lymphoma).
• Thymoma: Most common primary anterior tumor; strong link to Myasthenia Gravis.
• Teratoma: Common GCT; shows fat, fluid, calcification.
• Middle Mediastinum: Think lymphadenopathy (lymphoma, sarcoidosis) and developmental cysts.
• Posterior Mediastinum: Neurogenic tumors (schwannoma) are most frequent.
• Hodgkin's Lymphoma: Often presents with contiguous mediastinal lymphadenopathy.
• Sarcoidosis: Classic bilateral hilar and right paratracheal lymphadenopathy.