The musculocutaneous nerve is one of the four nerves that supply the muscles and skin of the arm, forearm, and hand. The median, radial, and ulnar are the other three nerves. It arises from the lateral cord of brachial plexus as a side branch, at the level of the lower border of the pectoralis minor muscle. The musculocutaneous nerve innervates the coracobrachialis, biceps brachii, and the brachialis anticus muscle as well as the skin of forearm.
This important nerve is composed of fibers originating from the fourth, fifth, and sixth cervical roots (C4, C5, C6). Having emerged from the lateral cord, it perforates the coracobrachialis muscle in the upper portion of arm. Then it travels obliquely down between the biceps brachii and brachialis anticus muscle. Giving off side branches, the musculocutaneous nerve extends along the radial side of forearm as the lateral cutaneous nerve, running into the wrist, in front of the radial artery. There it divides into smaller nerve filaments that run over the carpal bones to come up to the surface to supply the subcutaneous tissue and a portion of skin of hand.
Below, schematic drawing of brachial plexus showing the musculocutaneous nerve.
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