Pneumomediastinum

This radiograph demonstrates extensive pneumomediastinum. There is marked symmetric subcutaneous emphysema in the chest wall and neck. The muscle fibers of the pectoralis muscles are appreciable, indicated subpectoral air. Streaky lucencies are seen in the superior mediastinum extending to the neck, a classic finding in pneumomediastinum. A single lucent line is seen just above the diaphragm that appears to connect the left and right pleural spaces. This is called the “continuous diaphragm sign” and indicates pneumomediastinum. By following this line to the left and the right of the heart, the pericardial edges are appreciated several centimeters from the myocardium, indicating marked pneumopericardium. The medial wall of the aorta is also appreciable due to air in the posterior mediastinum.

These findings were ultimately attributed to the Macklin effect. CT excluded tracheal and esophageal leaks and interstitial emphysema was identified.