A combined variation of the musculocutaneous nerve associated with a supernumerary head of the biceps brachii muscle

Abstract

Single anatomical variation in the upper limb is common, but the coexistence of neuromuscular anomalies is still rare. We found a combined neuromuscular variation in the upper limb in a 61-year-old Korean male cadaver, whose cause of death was laryngeal carcinoma, during a routine dissection course for medical students. In his left arm, a supernumerary head of the biceps brachii muscle attached to the anteromedial surface of mid-humerus and united distally with the long and short heads of the biceps brachii muscle (BBM). The musculocutaneous nerve, which did not pierce the coracobrachialis muscle but gave 2 muscular branches, had a communicating branch to the median nerve. Since the presence of the supernumerary head of the BBM might affect the course and branching of the musculocutaneous nerve, knowing different patterns of the musculocutaneous variation associated with the BBM variations is essential for anatomists and clinicians.