CTICasesSpontaneous Pneumomediastinum (Marijuana-induced)
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Imaging findings
Chest radiographs and CT demonstrate pneumomediastinum with gas tracking into the neck, causing subcutaneous emphysema. A subtle pleural line was initially misinterpreted as pneumothorax, but on expiration and further review, it was identified as a 'pseudo pneumothorax' due to its dirty appearance and discontinuation, distinct from the clean gas of a true pneumothorax. Lateral radiographs nicely show streaks of gas outlining mediastinal structures, including a 'ring around the artery sign' and gas separating thymic tissue. CT confirms air tracking along the pulmonary vein, indicating a lung origin.
Key takeaways
Spontaneous pneumomediastinum, often triggered by activities like marijuana smoking (due to Valsalva maneuvers and barotrauma), presents with characteristic radiographic signs such as mediastinal gas outlining structures (e.g., ring around the artery), subcutaneous emphysema, and separation of thymic tissue. It's crucial to differentiate this from pneumothorax or pneumopericardium based on gas distribution and characteristics. Air tracking along pulmonary veins is a reliable sign of a lung origin via the Macklin phenomenon.
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