Unusual nerve supply of biceps from ulnar nerve and median nerve and a third head of biceps

Abstract

ABSTRACTVariations in branching pattern of the brachial plexus are common and have been reported by several investigators. Of the four main nerves traversing the arm, namely median, ulnar, radial and musculocutaneous, the ulnar and median nerve do not give any branches to muscles of the arm. Ulnar nerve after taking origin from medial cord of brachial plexus runs distally through axilla on medial side of axillary artery till middle of arm, where it pierces the medial intermuscular septum and enters the posterior compartment of arm. Ulnar nerve enters forearm between two heads of flexor carpi ulnaris from where it continues further. It supplies flexor carpi ulnaris , flexor digitorum profundus and several intrinsic muscles of hand . We recently observed dual supply of biceps muscle from ulnar and median nerves in arm. Musculocutaneous nerve was absent. Although communications between nerves in arm is rare, the communication between median nerve and musculocutaneous nerve were described from the 19th century which could explain innervation of biceps from median nerve. But no accurate description of ulnar nerve supplying biceps could be found in literature. Knowledge of anatomical variation of these nerves at level of upper arm is essential in light of the frequency with which surgery is performed to transfer nerve fascicles from ulnar nerve to biceps in case of brachial plexus injuries. We also observed third head of biceps, our aim is to describe the exact topography of this variation and to discuss its morphological.