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Seen on chest X-ray or CT when the mediastinum appears broader than normal.
Causes:
Aortic aneurysm (especially of the arch).
Lymphadenopathy (tuberculosis, lymphoma, metastasis).
Mediastinal tumors (thymoma, teratoma, thyroid mass).
Hemorrhage or trauma.
Important because it may compress trachea, esophagus, or great veins, causing dyspnea, dysphagia, and venous congestion.
Displacement of mediastinal structures toward or away from one lung.
Shift toward one side: due to lung collapse (atelectasis) or fibrosis pulling the mediastinum.
Shift away from one side: due to pleural effusion, pneumothorax, or large mass pushing it.
Clinical sign: displacement of trachea and apex beat.
Usually caused by bronchogenic carcinoma or mediastinal lymph node enlargement.
Results in distension of veins of face, neck, and upper limb with facial swelling and cyanosis.
Collateral venous channels (azygos system, internal thoracic, and vertebral veins) enlarge to bypass obstruction.
Aneurysmal dilation of the arch or descending aorta may compress surrounding structures:
Trachea → Cough and dyspnea
Esophagus → Dysphagia
Recurrent laryngeal nerve → Hoarseness of voice
Sympathetic trunk → Horner’s syndrome
May present as mediastinal widening on radiograph or pulsatile mass in the chest.
Infection or inflammation of mediastinal connective tissue, often from esophageal perforation, tracheostomy, or cardiac surgery.
Causes severe chest pain, fever, and respiratory distress.
Can spread rapidly due to the loose areolar tissue of the mediastinum.
Presence of air in the mediastinum, usually due to alveolar rupture, tracheobronchial tear, or esophageal perforation.
Air may spread to the neck and face causing subcutaneous emphysema (crackling on palpation).
Seen on radiographs as streaks of radiolucency in the mediastinum.
Tumors may arise from any mediastinal structure:
Anterior mediastinum: thymoma, teratoma, thyroid mass, lymphoma.
Middle mediastinum: pericardial cyst, enlarged lymph nodes.
Posterior mediastinum: neurogenic tumors, esophageal masses.
Symptoms result from compression of trachea, esophagus, or major vessels.
Diagnosis: CT/MRI or mediastinoscopy with biopsy.
Enlargement of thymus (thymoma or thymic hyperplasia) may cause:
Pressure on trachea or SVC, producing cough or venous congestion.
Association with myasthenia gravis (autoimmune weakness).
Accumulation of fluid in the pericardial cavity (within middle mediastinum) compresses the heart.
Causes distended neck veins, hypotension, muffled heart sounds (Beck’s triad).
Emergency drainage by pericardiocentesis is life-saving.
Esophageal carcinoma may produce dysphagia due to encroachment on the lumen and invasion of adjacent structures (trachea, aorta).
Hiatus hernia and esophageal varices also relate to this region.
Enlargement occurs in SVC obstruction or right heart failure as a collateral drainage route.
Visible on X-ray as a paratracheal shadow on the right side.
Injury to the thoracic duct during surgery or trauma causes leakage of chyle (lymph rich in fat) into the pleural cavity.
Leads to milky pleural effusion requiring drainage.
Common in children; arise from sympathetic ganglia or nerve sheaths.
May cause back pain, Horner’s syndrome, or paraplegia by spinal compression.
Performed through a small incision above the suprasternal notch to inspect or biopsy mediastinal lymph nodes or masses.
Helps diagnose tuberculosis, sarcoidosis, or metastasis.
Pain from pericardium or diaphragmatic pleura (phrenic nerve) may be referred to the shoulder tip (C4 dermatome).
Pain from esophagus or heart may radiate to substernal or left arm region.
The mediastinum, though compact, is a high-risk zone for compression syndromes, infections, and tumors. Its clinical relevance lies in how pathologies of distinct mediastinal parts mimic each other through shared nerve pathways and radiological appearances — making thorough anatomical knowledge crucial for accurate diagnosis and management.
Mnemonics make the maze-like mediastinum easier to remember. Below are the simplified and high-yield memory aids for gross anatomy and clinical recall.
Mnemonic: “SAMI divides the chest”
S → Superior mediastinum
A → Anterior mediastinum
M → Middle mediastinum
I → Inferior mediastinum (posterior part included)
Mnemonic: “SAD PALS”
S → Sternum (anterior)
A → Aorta and vertebral column (posterior)
D → Diaphragm (inferior)
P → Pleura (lateral)
A → Aperture (thoracic inlet, superior)
L → Lungs (on each side)
S → Sternum (repetition helps with orientation in cross sections)
Mnemonic: “Thymus Veins Arteries Trachea Esophagus Duct Spine”
→ Thymus → Great Veins → Arch of Aorta and its branches → Trachea → Esophagus → Thoracic Duct → Vertebral column.
Mnemonic: “ABC”
A → Arch of Aorta
B → Brachiocephalic trunk
C → Left Common carotid and Left subclavian arteries
Mnemonic: “ALAS”
A → Arch of aorta (nerve hooks under it)
L → Ligamentum arteriosum (nerve passes behind it)
A → Ascends in tracheoesophageal groove
S → Supplies larynx (intrinsic muscles except cricothyroid)
Mnemonic: “A Middle Posterior — AMP”
A → Anterior mediastinum (Thymus remnants, fat, lymph nodes)
M → Middle mediastinum (Heart, pericardium, great vessels)
P → Posterior mediastinum (Aorta, Azygos, Thoracic duct, Esophagus, Sympathetic trunks)
Mnemonic: “DATE VSS”
D → Descending aorta
A → Azygos and hemiazygos veins
T → Thoracic duct
E → Esophagus
V → Vagus nerves (forming esophageal plexus)
S → Sympathetic trunk
S → Splanchnic nerves
Mnemonic: “Great 5-9, Less 10-11, Least 12”
Greater splanchnic → T5–T9 → Celiac ganglion
Lesser splanchnic → T10–T11 → Aorticorenal ganglion
Least splanchnic → T12 → Renal plexus
Mnemonic: “4 Ts”
Thymoma
Teratoma
Thyroid (ectopic or retrosternal goitre)
Terrible lymphoma
Mnemonic: “Heart Pumps Vital Power”
H → Heart and pericardium
P → Phrenic nerves with pericardiacophrenic vessels
V → Great vessels (ascending aorta, pulmonary trunk, SVC, IVC)
P → Pulmonary veins and arteries
B → Main bronchi (Roots of lungs)
Mnemonic: “A.I.V.”
A → Azygos vein
I → Internal thoracic veins
V → Vertebral venous plexus
These form alternate routes to drain blood into the inferior vena cava when the SVC is compressed.
Mnemonic: “Pretty Tall Attractive Elegant Spine”
→ Pericardium → Trachea → Aorta → Esophagus → Spine
Helps visualize cross-sectional anatomy on CT or MRI.
Mnemonic: “I Ate 10 Eggs At 12”
I (8) → Inferior vena cava (T8)
Ate (10) → Esophagus (T10)
12 (12) → Aorta (T12)
These correspond to their vertebral levels and mediastinal associations.
Mnemonic: “3 A’s + 3 M’s”
Aortic aneurysm
Aortic dissection
Azygos vein enlargement
Mediastinal tumor
Metastasis
Massive lymphadenopathy
Mnemonic: “MEDI-ASTINUM”
M → Myocardial ischemia
E → Esophageal spasm
D → Diaphragmatic irritation
I → Inflammatory pericarditis
All can radiate to left shoulder, neck, or arm via phrenic or sympathetic nerves.
Mnemonic: “VET”
V → Vena cava (T8)
E → Esophagus (T10)
T → Thoracic aorta (T12)
Mnemonic: “Phrenic feels the Pain”
→ Any inflammation involving pericardium or diaphragmatic pleura produces shoulder pain (C3–C5 dermatomes) via phrenic nerve.
Mnemonic: “Vessels-Vagus-Vertebra”
From front to back in CT sections — great vessels, then vagus/esophagus, then vertebral bodies.
These mnemonics neatly compress the mediastinum’s complicated anatomy, divisions, and clinical associations into memorable cues, perfect for viva and rapid recall before exams.
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