Two lesser known but useful signs of neonatal pneumothorax.

Two lesser known signs of neonatal pneumothorax are presented: the "large, hyperlucent hemithorax" sign and the "medial stripe" sign. In a review of 113 consecutive cases of proven neonatal pneumothorax, the large, hyperlucent hemithorax was the presenting sign in 29 and the medial stripe in 12 (25% and 11%, respectively). A left-sided preponderance of both signs but especially of the large, hyperlucent hemithorax remained unexplained. The practical significance of the signs, differential diagnosis, and influence of the Mach effect are described.