A split and conjoined median nerve in the forearm.

We observed a variation of the median nerve that split into two divisions in the proximal forearm and conjoined into a single cord in the distal forearm before entering the carpal tunnel. The medial division was larger than the lateral division. An aberrant muscular slip from the flexor digitorum superficialis ran over the medial division of the split median nerve. The muscular slip over the medial division might have caused an entrapment syndrome of this nerve due to several muscular and cutaneous branches originating from the medial division. This variation of the median nerve has not been reported to our knowledge and may affect diagnosis and treatment of any neuropathy of the median nerve.