Peripheral mononeuropathies occur only rarely in association with decompres
sion illness. The sites previously reported to be affected are areas of pot
ential entrapment in which a peripheral nerve traverses a confined area. In
these instances, the pathophysiology has been presumed to be mechanical pr
essure in an enclosed space by a gas bubble. A rare case is now presented o
f a peripheral mononeuropathy of the medial branch of the deep peroneal ner
ve in a scuba diver following surfacing from a 195 foot dive. This case dif
fers from prior reports of mononeuropathy in association with decompression
illness in that the affected nerve does not traverse a confined site in wh
ich mechanical compression by a gas bubble is likely. The mechanism of inju
ry is hypothesized to be a manifestation of decompression illness with a ga
s bubble causing blood flow obstruction and an ischemic infarct.