BILATERAL 4-HEADED BICEPS BRACHII MUSCLES - THE MEDIAN NERVE AND BRACHIAL-ARTERY PASSING THROUGH A TUNNEL FORMED BY A MUSCLE SLIP FROM THE ACCESSORY HEAD

Bilateral four-headed biceps brachii muscles were observed in the diss ected cadaver of a 95-year-old Japanese woman. The third head on both sides originated from the humerus at the insertion of the coracobrachi alis and inserted into the distal part of the biceps brachii and the p roximal part of the common biceps tendon on the ipsilateral side. The fourth head on both sides arose from a thin fibrous origin from the in tertubercular sulcus and the insertion of the pectoralis major, and in serted into the confluence of the biceps brachii and the third head. T his anomaly is relatively rare. Moreover, the left third head gave off a muscle slip into the posterior fascia of the pronator teres, formin g a tunnel. The median nerve and the brachial artery passed through th e tunnel, where the nerve and artery seemed to be compressed. The poss ible production of clinical symptoms: given the anatomy, is discussed. (C) 1998 Wiley-Liss, Inc.