Anatomical Variation of the Recurrent Motor Branch of the Median Nerve.

The recurrent motor branch (RMB) of the median nerve has commonly thought to originate proximal to the terminal digital branches, although its anatomical course and number may vary. We report a rare variation of the RMB that arose from the second common palmar digital nerve. The median nerve bifurcated into the first and second common palmar digital nerves distal to the transverse carpal ligament, with the RMB dividing from the second common palmar digital nerve and traveling retrograde to enter the abductor pollicis brevis muscle. This high origin variation may be at increased risk of injury during procedures of the hand.