An unusual cause of carpal tunnel syndrome. Case report.

A 38 year old woman with carpal tunnel syndrome of the right hand was treated with operative decompression, initially successfully. Subsequently, she developed a compartment syndrome after an injury. On re-exploration, an accessory palmaris longus muscle was encasing the median nerve at the distal forearm and passing through the flexor sheath, underneath the flexor retinaculum, inserted into the deep palmar fascia.