Median Nerve: Course & Innervation

Median Nerve:
The median nerve originates from lateral and medial cords of the brachial plexus.

Lateral root arises from the anterior divisions of superior and middle trunks, has contributions from ventral roots of C5-C7
Medial root arises from the anterior division of the inferior trunk and has contributions from ventral roots of C8-T1

It is one of the five main nerves originating from the brachial plexus.

Course of the Median Nerve

Median nerve continues down the arm with brachial artery, when it initially lies lateral to the artery, and later crosses over to lie medial to it around halfway down the arm
Next, it passes within medial part of the antecubital fossa within the two heads of the pronator teres muscle
Then it goes through anterior forearm within flexor digitorum superficialis and flexor digitorum profundus muscles and performs three branches:

Anterior interosseous nerve – descends simultaneously the anterior interosseous membrane with the anterior interosseous artery.

Deep branch – penetrates into hand through the carpal tunnel beneath flexor retinaculum of the wrist, within the flexor carpi radialis and the flexor digitorum superficialis tendons.

Superficial/palmar cutaneous branch – while arises just before the wrist and pierces carpal ligament to penetrate the carpal tunnel – this nerve is therefore not affected by carpal tunnel syndrome.

Sensory Supply of the Median Nerve

The median nerve provides none sensory innervation to the upper arm
The skin over the thenar eminence
The lateral ⅔ palm of the hand
The palmar aspect of lateral 3½ fingers
The dorsal fingertips of lateral 3½ fingers (thumb, index, middle and half of the ring finger)

Motor Supply of the Median Nerve

The median nerve provides none motor supply to the axilla or upper arm
Median nerve supply all muscles of the anterior compartment of forearm except the flexor carpi ulnaris muscle and medial two parts of flexor digitorum profundus muscle
Flexor carpi radialis muscle—flexes and abducts the wrist
Pronator teres and pronator quadratus muscle – pronation of the forearm
Palmaris longus muscle – flexion of the wrist and tenses palmar aponeurosis
Lateral two parts of flexor digitorum profundus muscle – flexes the index and the middle fingers at DIPJs
Flexor digitorum superficialis muscle – flexion of the fingers at PIPJs
Flexor pollicis longus muscle – flexes the thumb at IPJ
Intrinsic muscles of hand – LOAF muscles
Lateral two lumbricals muscle – flexes the MCPJs and extend the IPJs of the index and middle finger
Opponens pollicis muscle – opposes the thumb
Abductor pollicis brevis muscle – abducts the thumb
Flexor pollicis brevis muscle– flexes the thumb at MCPJ