Hamman's sign revisited. Pneumothorax or pneumomediastinum?

Louis Hamman described distinctive chest noises and emphasized their association with pneumomediastinum in 1937. However, the etiology of Hamman's sign remains incompletely defined and its association with pneumothorax underemphasized. We present a patient with pneumothorax and Hamman's sign assessed by computed chest tomography. Tomography suggested an alternate genesis of Hamman's sign; free pleural air may be cyclically channeled through a lung fissure thus creating chest sounds.