The median nerve is formed by the union of a lateral root (from the lateral cord, C5–C7) and a medial root (from the medial cord, C8–T1) of the brachial plexus. It initially lies lateral to the brachial artery in the arm, before crossing anteriorly to run medial to it. At the elbow it passes deep to the bicipital aponeurosis and median cubital vein.
In the forearm, the nerve travels between the two heads of pronator teres and then continues deep to flexor digitorum superficialis, within its fascial sheath. Near the wrist, it lies superficial between flexor digitorum superficialis and flexor carpi radialis, just deep to palmaris longus tendon. It enters the carpal tunnel beneath the flexor retinaculum, superficial to the long flexor tendons, to supply the hand.
| Region | Branch |
|---|---|
| Upper arm | No motor branches, but may communicate with musculocutaneous nerve |
| Forearm | Pronator teres |
| Flexor carpi radialis | |
| Palmaris longus | |
| Flexor digitorum superficialis | |
| Flexor pollicis longus (via anterior interosseous nerve) | |
| Flexor digitorum profundus (radial half only) | |
| Distal forearm | Palmar cutaneous branch (supplies skin over thenar eminence; not affected in carpal tunnel syndrome) |
| Hand (Motor) | Motor supply (LOAF) |
| • Lateral 2 lumbricals | |
| • Opponens pollicis | |
| • Abductor pollicis brevis | |
| • Flexor pollicis brevis | |
| Hand (Sensory) | • Palmar surface of the thumb, index, middle and radial half of the ring finger |
| • Dorsal surface of distal phalanges of the same digits (proximal dorsal regions supplied by radial nerve) |
https://youtu.be/LSls4MWv3MQ?si=nd0bfIAFfoqrCbzk
Damage at wrist
Damage at elbow
Anterior interosseous nerve lesion