A previously healthy 16-year-old man felt acute retrosternal pain and persistent dyspnoea after extended exertion at sports. His electrocardiogram, echocardiogram, and serum levels of cardiac enzymes, were all normal. The thoracic X-ray, however, revealed pneumomediastinum (black arrows) with pneumopericardium (white arrows), and led to the diagnosis of spontaneous pneumomediastinum. On the second day, cutaneous emphysema was observed in the patient's neck. Under a regime of analgesia and reduced activity, the symptoms resolved completely after 4 days.

Radiological findings in pneumomediastinum may be minimal, with localised areas of diminished density around the mediastinal organs and vessels on the X-ray. Contrast radiography, and computerised tomographic scanning, may be needed to exclude more severe conditions, such as gastro-oesophageal perforation, mediastinitis, and aspiration or ingestion of foreign bodies. Alveolar rupture, with subsequent spreading of trapped air along the peribronchovascular sheaths into the mediastinum, is presumed to produce pneumomediastinum. Acute and chronic hyperventilation, sudden shifts of intra-thoracal pressure, and iatrogenic manoeuvres have all been suggested as possible etiologies.¹

Figure 1.