The median nerve is one of the five main nerves originating from the brachial plexus and provides motor and sensory innervation to parts of the forearm and hand.
Origin
The median nerve is formed from a lateral root from the lateral cord and a medial root from the medial cord of the brachial plexus. It forms from nerve roots originating at C5-T1.
Course
In the axilla, the median nerve lies lateral to the axillary artery. It enters the arm and descends in the medially between biceps brachii and triceps brachii. It cross the brachial artery.
In the cubital fossa, the median nerves lies medial to the brachial artery and the biceps brachii tendon. Gives articular branches to the elbow joint
The median nerve enters the forearm between the two heads of pronator teres muscle and gives off the anterior interosseous nerve.
It courses towards the wrist with the ulnar nerve and ulnar vessels (deep to flexor digitorum superficialis).
It enters the hand through the carpal tunnel (the only nerve to traverse the carpal tunnel), passes deep to the flexor retinaculum at the wrist, and superficial to FPL, FDS
On entering the palm, it gives off motor and cutaneous branches.
Branches
- Anterior interosseous nerve - supplies flexor pollicis longus, pronator quadratus and radial half of flexor digitorum profundus
- Located in forearm, anterior to interosseous membrane, between flexor pollicis longus and flexor digitorum profundus
- Motor branch in the hand - supplies thenar muscles and the radial two lumbricals
- Palmar cutaneous branch - cutaneous innervation to the palmar aspect of the thumb, index and middle fingers and the radial half of the ring finger. Palmar cutaneous branch arises proximal to carpal tunnel & remains superficial to FR
- Articular branches to the elbow, wrist, carpal and phalangeal joints
- Terminal branches to 1st-3rd common palmar digital &proper digital nerves; supply lumbricals & volar skin of fingers
Variant anatomy
- high division or bifid median nerve
- median nerve (normal or bifid) may be accompanied by a persistent median artery of the forearm
- accessory branches arising proximal or distal to the carpal tunnel
- variant course of thenar branch