A Rare Anatomical Variant of the Thenar Motor Branch Encountered during Carpal Tunnel Release

Abstract

Iatrogenic injury to the thenar motor branch of median nerve, though rare, is a serious complication during carpal tunnel decompression. The incidence is high when there is variation in the thenar motor branch and hence we should be aware of the common as well as unusual and rare anatomical variants. As uncommon variations render the thenar branch more prone for iatrogenic injury knowing more would surely save one’s day while doing a carpal tunnel release. We present a rare anatomical variant of the thenar motor branch of the median nerve that we encountered during open carpal tunnel release. The thenar motor branch was originating from the ulnar side of the median nerve proximal to the transverse carpal ligament, traversing subligamentous and joining a communicating branch from the median nerve distal to the transverse carpal ligament. The nerve was accidentally cut intraoperatively, which was immediately identified and repaired. At the postoperative follow-up after 6 months, patient has recovered thenar function with the ability to write with his right hand with good opposition.