Mononeuropathy of the medial branch of the deep peroneal nerve in a scuba diver.

Peripheral mononeuropathies occur only rarely in association with decompression illness. The sites previously reported to be affected are areas of potential entrapment in which a peripheral nerve traverses a confined area. In these instances, the pathophysiology has been presumed to be mechanical pressure in an enclosed space by a gas bubble. A rare case is now presented of a peripheral mononeuropathy of the medial branch of the deep peroneal nerve in a scuba diver following surfacing from a 195 foot dive. This case differs from prior reports of mononeuropathy in association with decompression illness in that the affected nerve does not traverse a confined site in which mechanical compression by a gas bubble is likely. The mechanism of injury is hypothesized to be a manifestation of decompression illness with a gas bubble causing blood flow obstruction and an ischemic infarct.