Multiple variations in the course and motor branching pattern of the musculocutaneous nerve with unusual communication with the median nerve.

Abstract

Anatomic variations in course and motor branching pattern of the musculocutaneous nerve (MCN) with unusual communication with the median nerve were determined on the left arm of a 62-year-old formalin fixed male cadaver. The MCN did not pierce the coracobrachialis muscle. It provided 4 primary motor branches. The first branch emerged 1.5 cm inferior to the coracoid process to innervate the coracobrachialis muscle. The second branch emerged 8 cm inferior to the coracoid process to innervate the biceps brachii muscle. The third branch to brachialis muscle emerged 13.9 cm inferior to the coracoid process. The last branch to the common belly of biceps brachii muscle emerged 19.6 cm inferior to the coracoid process. Two communications with the median nerve were observed. The proximal thick communicating branch had the direction from the MCN to the median nerve while the distal one was a small nerve bundle with a direction from the median nerve to the MCN. The present report provided evidence of multiple variations in one MCN which had not been reported previously. Anatomic variation in this case has clinical implications, considering that injury of the MCN in the upper part of arm would cause unexpected paralysis of flexor muscles of forearm and thenar muscle due to communications between this and median nerve.