Bilateral accessory flexor muscle of the forearm giving rise to a variant head of the first lumbrical

Guiyun ZHANG, Bruce A. FENDERS

Abstract

We describe a bilateral accessory deep flexor in the forearm that originated from the lateral side of the forearm. The relatively large tendon bifurcated distally to form two branches, one of which was associated with a variant head of the first lumbrical muscle. The presence of an accessory tendon and a variant muscle within the carpal tunnel may contribute to median nerve compression and development of carpal tunnel syndrome in some patients.