Abstract
A policy of obtaining a routine chest radiograph in every young patient with unexplained chest pain or dyspnoea led to the diagnosis of 14 cases of spontaneous pneumomediastinum within four years, whereas only two cases from former years could be found retrospectively. One patient had recurrent spontaneous pneumomediastinum, the first case so far reported. Analysis of admission data suggested that this entity may be much more common than is generally believed, and may be second only to spontaneous pneumothorax as a cause of admission of young, healthy individuals experiencing sudden chest pain or shortness of breath. After reviewing the published reports we propose the following definition of spontaneous mediastinal emphysema: the non-traumatic presence of free air in the mediastinum in a patient with no known underlying lung disease. When it occurs without associated pneumothorax it is benign. The incidence of spontaneous pneumomediastinum for the four-year period under study was 1 per 12 850 admissions.