Imaging description

Imaging findings of pneumomediastinum consist of gas outlining the mediastinal structures (Figure 27.1). Gas within the mediastinum may dissect superiorly along the fascial planes, which can lead to subcutaneous emphysema in the neck and anterior chest (Figure 27.1). Occasionally the gas can dissect along the peribronchovascular interstitial tissue into the fissural pleura. A pneumothorax can occur from gas rupturing from the fissural pleura or directly from the mediastinal pleura. The gas can also extend between the heart and diaphragm giving the appearance of air along the entire diaphragm. This is known as the continuous diaphragm sign [1]. Gas in the mediastinum can also dissect to or from the abdomen via the retroperitoneal space (Figure 27.1).

Importance

It is important to know the etiology of a pneumomediastinum. Spontaneous pneumomediastinum generally has a benign course. However, potentially life-threatening complications such as tension pneumothorax or tension pneumomediastinum [2] can occur. Other serious causes of pneumomediastinum include perforation of the esophagus, trachea or bronchus, or hollow abdominal viscus. If pneumomediastinum persists or the etiology is unclear, further evaluation with CT abdomen, esophagram, esophagoscopy, or bronchoscopy may need to be performed.