Click on Images for Enlarged View
Findings: Extraluminal gas is seen outlining the inner surface of the mediastinal pleura, lateral to the superior left heart border (on the PA view) and anterior to the heart (on the lateral view). Lucent streaks also outline both pulmonary arteries and the ascending aorta. The remainder of the chest is unremarkable.
Diagnosis: Pneumomediastinum.
Discussion:Pneumomediastinum has a variety of causes. It can be due to alveolar rupture associated with either elevated alveolar pressure or alveolar disease, laceration of the tracheobronchial tree or gastrointestinal tract, or gas tracking into the mediastinum from the neck, retroperitoneum, or chest wall.
It is often asymptomatic, but may cause chest pain or dyspnea. A pneumothorax can also be a complication if there is a rupture of the mediastinal pleura.
Pneumomediastinum is manifested by thin lucent streaks of gas that outline mediastinal structures elevating the mediastinal pleura and may extend into the neck or chest wall. The most common location for the gas to be seen is just superior to the heart on the left (as in this case). Gas is also commonly seen outlining the ascending aorta, aortic arch, and its branches, the pulmonary arteries, and the trachea and adjacent bronchi.
It can sometimes be difficult to distinguish a pneumomediastinum from a pneumothorax and/or pneumopericardium. However, careful evaluation of the location and distribution of the gas will usually differentiate these conditions. Often an upright or decubitus view can be helpful, as the gas in a pneumothorax or pneumopericardium shifts with changes in a patient’s position, unlike a pneumomediastinum. However, it must not be forgotten that a pneumomediastinum can coexist with either a pneumothorax or pneumopericardium.
References:
Bejvan SM, Godwin JD. Pneumomediastinum: Old Signs and New Signs.
JR 1996;166:1041-1048.
Submitted by: