Musculocutaneous nerve
Nervus musculocutaneus
Also known as: lateral cutaneous nerve of forearm, lateral antebrachial cutaneous nerve
The nerve of the anterior (flexor) compartment of the arm, from the lateral cord (C5–C7). It supplies coracobrachialis, biceps brachii and brachialis, then continues as the lateral cutaneous nerve of the forearm.
Overview
The musculocutaneous nerve leaves the lateral cord opposite pectoralis minor. It pierces coracobrachialis about 5 cm below the coracoid process, which is a reliable landmark. It then runs downward and laterally between biceps brachii and brachialis, supplying all three flexors of the arm. Just above the elbow it emerges lateral to the biceps tendon and pierces the deep fascia to become the lateral cutaneous nerve of the forearm. This supplies the skin along the lateral (radial) forearm as far as the wrist, lying near the cephalic vein. Brachialis has a dual supply: its small lateral part is supplied by the radial nerve. This is why elbow flexion is only partly lost after a musculocutaneous injury.
- Location
Axilla → through coracobrachialis → between biceps and brachialis in the anterior arm → lateral forearm skin.
Anatomy
- Innervation
- Motor: coracobrachialis, biceps brachii and brachialis (most of it).
• Sensory: the skin of the lateral forearm (lateral cutaneous nerve of the forearm) and the elbow joint.- Nerve roots
C5, C6, C7 (lateral cord).
- Course
Lateral cord → pierces coracobrachialis → descends between biceps (superficial) and brachialis (deep) → emerges lateral to the biceps tendon in the cubital fossa → lateral cutaneous nerve of the forearm.
Function
- Flexion of the elbow (biceps, brachialis)
- Powerful supination of the forearm (biceps)
- Flexion and adduction of the arm at the shoulder (coracobrachialis, biceps)
- Sensation of the lateral forearm
- Efferent limb of the biceps reflex (C5–C6)
Clinical significance
Musculocutaneous nerve injury
Isolated injury is uncommon. It occurs with penetrating trauma, anterior shoulder dislocation, heavy weightlifting (entrapment within coracobrachialis) or shoulder surgery. The result is weak elbow flexion and supination, a lost biceps reflex and sensory loss along the lateral forearm. Elbow flexion is still possible through brachioradialis (radial nerve), pronator teres and the radially supplied part of brachialis.
Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.