Uploaded March 2026 | Updated September 2026, 3 weeks ago

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00:00 Introduction
00:53 What this video will cover
01:30 What is the mediastinum?
02:19 Mediastinal borders and boundaries
03:39 Two main classification systems of the mediastinum
05:35 Anatomical classification (traditional division)
08:28 ITMIG classification (modern CT-based system)
09:39 Prevascular compartment – structures & pathology
10:31 Visceral compartment – structures & pathology
11:24 Paravertebral compartment – structures & pathology
13:01 Systematic 6-step approach to mediastinal differential diagnosis
20:14 Clinical example: applying the framework
21:45 Ending

In this video I break down the anatomy of the mediastinum in anatomy, surgery and radiology

Definition and Boundaries

- Mediastinum: central compartment of thoracic cavity between the two lungs
- Superior boundary: thoracic inlet (T1, first rib, superior manubrium)
- Inferior boundary: diaphragm
- Anterior boundary: sternum
- Posterior boundary: thoracic vertebral bodies (T1-T12)
- Lateral boundaries: mediastinal pleura (parietal pleura lining lungs)

Traditional Anatomical Classification

- Sternal angle (angle of Louis): key landmark at T4-T5 disc level dividing mediastinum, corresponds to tracheal bifurcation and aortic arch
- Superior mediastinum: thoracic inlet to sternal angle containing aortic arch, brachiocephalic veins, SVC, upper thymus, trachea, esophagus, thoracic duct, phrenic and vagus nerves
- Inferior mediastinum: subdivided into anterior, middle, and posterior compartments
- Anterior mediastinum: between sternum and pericardium containing thymic remnant, fat, lymph nodes, internal thoracic vessels
- Middle mediastinum: contains pericardium, heart, great vessel origins, phrenic nerves
- Posterior mediastinum: between pericardium and spine containing descending aorta, esophagus, azygos/hemiazygos veins, thoracic duct, sympathetic chain

ITMIG Radiological Classification

- Prevascular compartment: anterior to great vessels and pericardium containing thymus/thymic remnant, site of "4 T's" (thymoma, thyroid, teratoma, terrible lymphoma)
- Visceral compartment: central zone containing heart, pericardium, great vessels, airways (trachea, carina, bronchi), esophagus, mediastinal lymph nodes. Home to lymphadenopathies and visceral pathology.
- Paravertebral compartment: along spine (vertical line 1 cm posterior to anterior vertebral body margin) containing sympathetic chain, intercostal vessels, site of neurogenic tumors (70-80% of posterior masses)

Systematic Approach to Mediastinal Masses

- Step 1: Identify compartment on axial CT
- Step 2: Consider patient age (children/adolescents: lymphoma, germ cell tumors, neurogenic tumors; young adults 20-40: lymphoma, germ cell tumors, thymic hyperplasia; middle-aged/older: thymoma, thyroid masses, metastatic disease)
- Step 3: Analyze imaging characteristics (fat suggests teratoma/thymolipoma, cystic features suggest thymic/bronchogenic/pericardial cyst, solid enhancing patterns, calcifications in teratomas and treated lymphoma)
- Step 4: Add clinical context (myasthenia gravis with thymoma, B symptoms with lymphoma, elevated AFP/beta-HCG with germ cell tumors)
- Step 5: Choose appropriate imaging (chest X-ray for screening, contrast-enhanced CT as gold standard, MRI for cystic vs solid differentiation and neurogenic tumors, PET-CT for lymphoma staging and treatment response)
- Step 6: Synthesize findings for diagnosis

Common Mediastinal Pathology

- Prevascular masses: thymoma (most common in adults 40+), lymphoma (Hodgkin's and non-Hodgkin's), germ cell tumors, thyroid extension
- Visceral compartment: lymphadenopathy (lung cancer, lymphoma, sarcoidosis), esophageal masses, bronchogenic cysts, pericardial effusions
- Paravertebral masses: neurogenic tumors (schwannomas, neurofibromas, ganglioneuromas), osteomyelitis, paravertebral abscesses

Sources:

- Carter BW, Benveniste MF, Madan R, et al. (2017). ITMIG Classification of Mediastinal Compartments and Multidisciplinary Approach to Mediastinal Masses. RadioGraphics, 37(2):413-436
- Whitten CR, Khan S, Munneke GJ, Grubnic S. (2007). A Diagnostic Approach to Mediastinal Abnormalities. RadioGraphics, 27(3):657-671
- Shields TW. (1983). Primary tumors and cysts of the mediastinum. In: General Thoracic Surgery. Philadelphia: Lea & Febiger
- Gray's Anatomy, 41st Edition (2015). The Mediastinum. Elsevier
- Juanpere S, et al. (2013). A Diagnostic Approach to the Mediastinal Masses. Insights into Imaging, 4(1):29-52

Images from: ResearchGate, ScienceDirect, Radiology Key, RSNA RadioGraphics, Kenhub, PMC, BJR Open

Programs used: Complete Anatomy by 3d4medical, Biorender, Powerpoint, Canva, Word, Camtasia, Audiate.