Median nerve

Roots

Lateral (C5–C7) and medial (C8–T1) cords — the classic 'median combination' straddling the axillary artery.

Course

Descends the arm beside the brachial artery without branching, crosses the cubital fossa medial to the biceps tendon, passes between the two heads of pronator teres, and runs between the flexor digitorum superficialis and profundus before entering the carpal tunnel deep to the flexor retinaculum.

Motor supply

All forearm flexors except flexor carpi ulnaris and the ulnar half of flexor digitorum profundus; the thenar muscles (abductor pollicis brevis, flexor pollicis brevis, opponens) and the lateral two lumbricals.

Sensory supply

Palmar thumb, index, middle and radial half of ring finger — and the dorsal skin over the nail beds of the same digits.

Clinical relevance

Carpal tunnel syndrome — the commonest entrapment neuropathy: night pain, thenar wasting and positive Phalen and Tinel signs. A proximal lesion produces the 'hand of benediction' on making a fist; anterior interosseous branch lesions weaken thumb-index pinch.

Related conditions

• Carpal tunnel syndrome