musculocutane

The musculocutaneous nerve is a peripheral nerve of the upper limb that arises from the lateral cord of the brachial plexus, typically containing fibers from the C5 to C7 roots. It leaves the axillary region and enters the arm by piercing the coracobrachialis muscle, then descends between the biceps brachii and the brachialis.

In the arm its motor responsibility is to innervate the anterior compartment muscles: coracobrachialis, biceps brachii, and brachialis (part of its fibers). Through its terminal branch, the lateral antebrachial cutaneous nerve, it provides sensory innervation to the skin of the lateral forearm. This cutaneous distribution generally extends from near the elbow to the distal forearm, contributing to the forearm’s sensory map.

Clinical significance centers on injury or compression of the nerve, which can result in weakness of elbow flexion and forearm supination, along with sensory loss on the lateral forearm. Causes include trauma to the humerus, compression in the arm, or iatrogenic injury during IV injections or surgical procedures. Anatomical variations exist; in some individuals the nerve may take a different course, or pierce or bypass surrounding muscles differently, which can influence both presentation and risk during interventions.

Overall, the musculocutaneous nerve is essential for elbow flexion and forearm rotation, and for providing sensation to the lateral forearm.