Overview

The musculocutaneous nerve is a terminal branch of the brachial plexus. It powers the main elbow-flexing muscles at the front of the upper arm and continues as a sensory nerve to the lateral forearm.

Origin and Course

It usually arises from the lateral cord with fibres from C5-C7. It commonly pierces coracobrachialis, then travels between biceps brachii and brachialis.

Function

It supplies coracobrachialis, biceps brachii and brachialis. These muscles flex the elbow; biceps also contributes strongly to forearm supination. Its terminal sensory branch supplies the thumb-side of the forearm.

Common Injuries

Isolated injury is rare. Traction, compression, surgery or a broader lateral cord injury may affect it.

Pain, Weakness and Sensory Patterns

Possible findings include weaker elbow flexion or supination and altered sensation along the lateral forearm. Other nerves and muscles partly preserve elbow flexion, so weakness may not be complete.

Clinical Relevance

Clinicians compare strength, reflexes and sensation to distinguish this nerve from cervical root or other plexus problems.

References

Standring S, ed. Gray's Anatomy. 42nd ed. Elsevier; 2020.
Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. 9th ed. Wolters Kluwer; 2023.

Musculocutaneous Nerve