Combination of six variations in a single arm

Abstract

Variations on the neuromuscular structures of the upper limb reflect the complex development of that region. Many of them may be important during surgical and/or diagnostic procedures; however, some of them are of academic interest. Here we report a case of six neuromuscular variations in a single upper limb. During routine educational dissection for the undergraduate medical students at the Department of Anatomy, Faculty of Medicine, Hacettepe University, Ankara, Turkey, we came across six variations on the left upper limb of a 43-year-old well-built male cadaver. We conformed to the steps described in Grant’s Dissector during the dissection, and photographed the case with a Nikon Coolpix camera. The biceps brachii showed an accessory head that originated from the tendon of pectoralis major, ran downwards superficial to the long head and joined the distal 1/3 of the muscle mass. A thin muscle band accompanying the lateral side of the pectoralis major was identified as pectoralis quartus. It was originated from the sixth rib and inserted to the coracoid process. The coracobrachialis was double-headed having a common origin from the coracoid process, separating into two after a short course and joining again at the middle level of the arm. Musculocutaneous nerve did not pierce the coracobrachialis. Instead, it ran beneath the two bellies of the muscle. The lateral cord of the brachial plexus passed between the two bellies of coracobrachialis; then divided into musculocutaneous nerve and the lateral root of the median nerve at a lower level than usual. The right upper limb showed no variations. The variations described here maybe commonly encountered individually; however, the combination of six of them in a single arm is previously unreported.