The extrapleural air sign in pneumomediastinum.
D003937:Diagnosis, Differential; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000175:diagnosis*; D008171:Lung Diseases / Q000175:diagnosis; D008478:Mediastinal Emphysema / Q000175:diagnosis*; D013902:Radiography, Thoracic