Pathology.—Pneumomediastinum is the presence of gas in mediastinal tissue outside the esophagus and tracheobronchial tree. It may be caused by spontaneous alveolar rupture, with subsequent tracking of air along the bronchovascular interstitium into the mediastinum. Pneumomediastinum is particularly associated with a history of asthma, severe coughing, or assisted ventilation.
Radiographs and CT scans.— Pneumomediastinum appears as lucent streaks on chest radiographs, mostly vertically oriented (Fig 53). Some of these streaks may outline vessels and main bronchi. (See also pneumopericardium.) [Fleischner Society]