(Fig. 1)

(Figs. 2a and 2b)

(Fig. 3)

Findings: CT Topogram shows extensive streaky lucencies in the upper chest and soft tissues of the neck . The hemidiaphragms appear continuous (Fig 1). The CT shows extensive lucency throughout the mediastinum (Figs. 2a, 2b). This lucency tracks inferiorly within the retrocrural space into the upper abdomen (Fig. 3). Note the extensive peripheral parenchymal opacities.

Diagnosis: Pneumomediastinum. Bleomycin drug toxicity.

Discussion: Pneumomediastinum can occur from a variety of sources. It can occur secondary to communication from the esophagus or central tracheobronchial tree. This can be traumatic or iatrogenic in nature. Pneumomediastinum can also be secondary to rupture of the alveoli into the interstitial space, with central dissection into the mediastinum. Secondary complications include pneumothorax, pneumopericardium and pneumoperitoneum. Alveolar rupture into the mediastinum has been reported as a secondary complication from foreign bodies or mucous plugging, coughing, emesis and forced Valsalva maneuver.

Radiographically, pneumomediastinum presents with linear lucencies that can outline mediastinal structures. Characteristically, pneumomediastinum is seen adjacent to the aorta, and can be seen outlining the pulmonary arteries, left usually more prominent than right. Other signs include the continuous hemidiaphragm sign and the V sign of Nacleros. The diagnostic challenge can occur in distinguishing pneumomediastinum from pneumothorax. Often, upright views and decubitus views are needed to distinguish these entities. In addition, the distinction between pneumopericardium and pneumomediastinum can be problematic. In general, pneumopericardium will present as a well defined lucency around the circumference of the heart, and will not extend above the pericardial reflection at the level of the pulmonary outflow tract.

References:
Bejvan SM and Goodwin JD. Pneumomediastinum: Old Signs
and New Signs. AJR 1996;166:1041-1048

Fraser RG, Pare JAP, Pare PD, Fraser RS, Genereux GP. Diagnosis
of Diseases of the Chest, 3rd ed. Philadelphia: Saunders, 1991:2801-2813.

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