Median innervated hypothenar muscle: anomalous branch of median nerve in the carpal tunnel.

A hypothenar motor branch of the median nerve in the carpal tunnel was observed and its motor function was documented by direct intraoperative nerve stimulation in two patients having carpal tunnel releases. The hypothenar branch left the median nerve at the midcarpal tunnel area. It crossed the tunnel superficial to the flexor tendons and penetrated the transverse carpal ligament ulnarly to innervate the abductor digiti quinti. Such branching of the median nerve at this level has not been reported previously. Good visualization of the carpal tunnel and careful dissection of its content even in the so called safe zone ulnar to long axis of palmaris longus tendon is recommended.