A variation of the brachial plexus characterized by the absence of the musculocutaneous nerve: a case report.

A variation of the brachial plexus characterized by the absence of the musculocutaneous nerve on both sides was observed during the dissection of a 72 year-old female cadaver. The long thoracic nerve included only the fibers from C5 and C6 on the left side. The musculocutaneous nerve was absent and two branches from the lateral cord innervated the coracobrachialis muscle. The median nerve innervated the biceps brachii and brachialis muscles in the arm and also gave off the lateral antebrachial cutaneous nerve. Additionally, a communicating branch was found from the median nerve to the ulnar nerve in the forearm. The knowledge of the anatomical variations of the peripheral nerve system can help give explanation when encountering an incomprehensible clinical sign.