Palmaris profundus tendon prohibiting endoscopic carpal tunnel release: case report.

Palmaris profundus is an aberrant muscle of forearm and wrist anatomy. It has no discernible function, but its tendon has been implicated as a cause of carpal tunnel syndrome. Previously, all cases of palmaris profundus in the literature have been encountered during either open surgery or cadaveric dissection. We report a case of palmaris profundus encountered during attempted single-portal endoscopic carpal tunnel release, necessitating conversion to an open approach. There was a unique point of tendon insertion onto the undersurface of the transverse carpal ligament, more proximal than what has been previously described in the literature. There were other anomalies present as well, including a persistent median artery and bifid median nerve. Given the volar position of the structure, its proximal point of insertion, and its minimal bulk, we did not feel that this was the cause of our patient's carpal tunnel syndrome.