Introduction: the median nerve (C6, 7, 8, T1) is the major nerve of the arm.
Formation: it is formed in the axilla by the Union of a lateral root from the lateral cord and a medial root of the medial cord of the brachial plexus
In the arm: it runs distally on the lateral side of the brachial artery until it reaches the middle of the arm where it crosses to the medial side of the humerus. It descends into the cubital fossa where it lies deep to the bicipital aponeurosis and the medial cubital fossa where it lies deep to the bicipital aponeurisis and the median cubital vein.
Forearm: the median nerve lies on the brachial is muscle in the forearm and passes between the two heads of the protonor teres. It then descends deep to the flexor digitorum supericialis. It continues distally between this muscle and the flexor digitorium profundus.
Wrist: here the median nerve becomes superficial at the ulnar side of the flexor carpi radial is deep to the tendon of palmaris longus.
Surface marking of the nerve is along a line drawn from the middle of the cubital fossa medial to the brachial artery to a point on the wrist on the ulnar side of the tendon of flexor carpi radialis.
Branches: the median nerve gives no branches in the axilla or arm only in the forearm and hand.
A. Articular: passes to the elbow joint
B. Muscular: anterior interosseus nerve to the muscles of the flexor compartment of the arm.
C. Cutaneous: palmer cutaneous to the skin on the radial side of the palm and dorsal aspect of the radial 3½ digits.
Clinical correlates:
A. If the median nerve is damaged at the elbow there is muscle impairment and protonation of the forearm is lost.
B. If damaged at the wrist, the thenar muscles (excluding the adductor pollicis) and the radial two lumbricals are paralysed resulting in loss of sensation over the thumb, adjacent 2½ digits and radial ⅔ of the palm of the hand.
C. The pronator syndrome: this is nerve entrapement syndrome caused by compression of the median nerve in the elbow