Median nerve

At a glance

English

Median nerve

Latin (TA2)

Nervus medianus

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the median nerve

The median nerve forms in the axilla when a lateral root from the lateral cord and a medial root from the medial cord of the brachial plexus join in front of the axillary artery, so it carries fibres from C5 or C6 to T1. In the arm it runs with the brachial artery, first on its lateral side and then crossing in front of it to lie medially by the time it reaches the cubital fossa.

At the elbow it lies under the bicipital aponeurosis and on brachialis, then leaves the fossa between the two heads of pronator teres, the deep head separating it from the ulnar artery. It descends on the deep surface of flexor digitorum superficialis, resting on flexor digitorum profundus. Above the wrist it comes to the surface between the tendons of flexor carpi radialis and flexor digitorum superficialis and then passes under the flexor retinaculum, within the carpal tunnel, alongside the long flexor tendons.

In the forearm it supplies every flexor except flexor carpi ulnaris and the ulnar half of flexor digitorum profundus. Direct branches reach flexor carpi radialis, pronator teres, flexor digitorum superficialis and palmaris longus; the anterior interosseous branch serves flexor pollicis longus, the radial half of flexor digitorum profundus and pronator quadratus. In the hand a short recurrent branch serves abductor pollicis brevis, opponens pollicis and the superficial head of flexor pollicis brevis, and digital branches supply the first two lumbricals and the palmar skin of the thumb, index, middle and radial half of the ring finger, with their nail beds. A palmar branch, given off above the wrist, supplies the central palm and thenar skin.

Carpal tunnel syndrome, compression of the nerve inside the tunnel, is the most common nerve entrapment in the body. It brings tingling and numbness in the radial three and a half digits, and later wasting of the thenar muscles, while the palm is spared because its branch runs above the retinaculum. A supracondylar fracture of the humerus can injure the nerve above the elbow, causing loss of pronation and of flexion in the radial digits, so that an attempted fist leaves the index and middle fingers straight, the hand of benediction. Wrist cuts, compression by pronator teres and anterior interosseous palsy are other patterns.

Course and supply

Arises from

Lateral and medial roots from the lateral cord (C5 to C7) and medial cord (C8, T1) of the brachial plexus, uniting in front of the axillary artery.

Ends in

Ends in the palm by dividing into the recurrent (thenar) branch and the common and proper palmar digital nerves.

Supplies

Motor to most forearm flexors and pronators, the thenar muscles and the first two lumbricals; sensory to the palmar side of the lateral three and a half digits with their nail beds and to the lateral palm.