Nerve
Musculocutaneous nerve
Arm motor supply that continues to forearm skin
High-yield
Its motor targets are coracobrachialis, biceps brachii and brachialis. Damage weakens elbow flexion and the biceps contribution to supination, while muscles supplied by other nerves may preserve some movement.
Overview
From the lateral cord, this nerve usually enters coracobrachialis before traveling between biceps and brachialis. After giving muscular branches, it continues near the elbow as a sensory nerve to the lateral forearm.
Learning this group? Read How to learn the brachial plexus.
Reference facts
- Root value
- Usually C5-C7 through the lateral cord
- Course
- Typically pierces coracobrachialis, descends between biceps and brachialis and emerges beside the biceps tendon as the lateral antebrachial cutaneous nerve
- Motor
- Coracobrachialis, biceps brachii and most of brachialis
- Sensory
- Lateral forearm skin through anterior and posterior branches of its cutaneous continuation
Mnemonic
Trace three arm muscles in order of the route: through coracobrachialis, then between biceps and brachialis, then out toward lateral forearm skin.
Clinical correlation
A proximal lesion can combine weak elbow flexion, reduced biceps reflex and altered lateral forearm sensation. An injury limited to its distal cutaneous continuation can change sensation while sparing the arm muscles.
Frequently asked questions
What are the roots of the musculocutaneous nerve?
Usually C5-C7 through the lateral cord.
What muscles does the musculocutaneous nerve supply?
The musculocutaneous nerve supplies the coracobrachialis, biceps brachii and most of brachialis.
What is the sensory distribution of the musculocutaneous nerve?
Lateral forearm skin through anterior and posterior branches of its cutaneous continuation.
What is the course of the musculocutaneous nerve?
Typically pierces coracobrachialis, descends between biceps and brachialis and emerges beside the biceps tendon as the lateral antebrachial cutaneous nerve.