Mediastinal Disorders

Mediastinal Anatomy - Chest Central

• Divided by transverse thoracic plane (sternal angle of Louis to T4-T5 IV disc).
  • Superior Mediastinum: Above this plane.
    • Contents: Thymus, great vessels (SVC, aortic arch & branches), trachea, esophagus, thoracic duct, phrenic & vagus nerves.
  • Inferior Mediastinum: Below this plane; subdivided.
    • Anterior: Sternum to pericardium. Contents: Thymus remnants, lymph nodes, fat.
    • Middle: Contains pericardium & heart. Contents: Heart, great vessel roots (ascending aorta, pulm. trunk, SVC), phrenic nerves.
    • Posterior: Pericardium to vertebrae (T5-T12). Contents: Esophagus, descending aorta, azygos/hemiazygos veins, thoracic duct.

⭐ The posterior mediastinum is the most common location for neurogenic tumors (e.g., schwannoma, neurofibroma).

Mediastinal Masses - Compartment Clues

Mediastinal masses are localized by compartment, aiding differential diagnosis.

• Anterior Mediastinum: (📌 "4 T's")
  • Thymoma: Associated with Myasthenia Gravis.
  • Teratoma/GCT (Germ Cell Tumors): Fat, fluid, calcification.
  • Thyroid (goiter): Retrosternal extension.
  • Terrible Lymphoma: Hodgkin's & Non-Hodgkin's.
• Middle Mediastinum:
  • Lymphadenopathy: Sarcoidosis, TB, lymphoma, metastases.
  • Cysts: Bronchogenic (most common), pericardial, esophageal duplication.
  • Vascular: Aortic aneurysms, vessel anomalies.
• Posterior Mediastinum: (Neurogenic tumors are most common)
  • Neurogenic tumors: Schwannoma, neurofibroma, ganglioneuroma.
  • Esophageal lesions: Tumors, diverticula, achalasia.
  • Paravertebral: Abscess, hematoma, EMH (Extramedullary Hematopoiesis).

⭐ 30-50% thymoma pts develop Myasthenia Gravis; 10-15% MG pts have thymoma.

Clinical Syndromes - Red Flag Roundup

• Compressive Symptoms:
  • SVC Syndrome: Facial/arm swelling, plethora, JVD. (Common with Lung Ca, lymphoma).
  • Airway (Trachea/Bronchi): Dyspnea, cough, stridor, post-obstructive pneumonia.
  • Esophagus: Dysphagia.
  • Nerves:
    • Recurrent Laryngeal: Hoarseness.
    • Phrenic: Diaphragmatic paralysis (elevated hemidiaphragm).
    • Sympathetic Chain: Horner's Syndrome (ipsilateral ptosis, miosis, anhydrosis).
• Paraneoplastic Syndromes:
  • Thymoma: Myasthenia Gravis (MG), pure red cell aplasia, hypogammaglobulinemia.
  • Germ Cell Tumors: ↑AFP (non-seminomatous), ↑β-hCG (choriocarcinoma, some seminomas).
  • Lymphoma: B-symptoms (fever, drenching night sweats, weight loss >10% in 6 months).

⭐ Myasthenia Gravis is the most common paraneoplastic syndrome associated with Thymoma, occurring in 30-50% of patients with thymoma.

Diagnostics & Key Disorders - Scan & Solve

• Imaging: CXR (initial), CT+C (gold standard), MRI (neuro/vascular), PET (malignancy).

• Markers: AFP (NSGCT), β-hCG (GCT), LDH (Lymphoma).

• Biopsy: EBUS-TBNA, CT-guided, Mediastinoscopy, VATS.

• Key Disorders:

  • Thymoma: Anterior; Myasthenia Gravis (30-50%).
  • Lymphoma: Most common; Hodgkin/NHL.
  • GCT: Anterior; Teratoma, Seminoma, NSGCT.
  • Neurogenic: Posterior; Schwannoma.
  • Mediastinitis: Acute (post-op/rupture), Chronic (fibrosing). 📌 Anterior: Thymoma, Teratoma, Thyroid, (Terrible) Lymphoma.

⭐ Lymphoma is the most common primary mediastinal tumor.

High‑Yield Points - ⚡ Biggest Takeaways

• Anterior mediastinum: Key masses are Thymoma, Teratoma/Germ cell tumors, Thyroid, and Lymphoma (the 4 T's).
• Thymoma is frequently linked to Myasthenia Gravis.
• Posterior mediastinum: Neurogenic tumors are most common here and overall.
• SVC syndrome: Caused by compression (e.g., lung cancer, lymphoma); presents with facial/arm swelling.
• Germ cell tumors can elevate AFP and/or β-hCG.
• Acute mediastinitis: Often due to esophageal perforation (Boerhaave's); a surgical emergency.