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The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, [1] and has contributions from ventral roots of C6-C7 (lateral cord) and C8 and T1 (medial cord). [1] [2]
In the palm of the hand, the median nerve is covered by the skin and the palmar aponeurosis, and rests on the tendons of the Flexor muscles.Immediately after emerging from under the transverse carpal ligament the median nerve becomes enlarged and flattened and splits into a smaller, lateral, and a larger, medial portion.
Unlike most of the median nerve innervation of the hand, the palmar branch travels superficial to the Flexor retinaculum of the hand. Therefore, this portion of the median nerve usually remains functioning during carpal tunnel syndrome. [1]
In the palm of the hand the median nerve is covered by the skin and the palmar aponeurosis, and rests on the tendons of the flexor muscles. Immediately after emerging from under the transverse carpal ligament the median nerve becomes enlarged and flattened and splits into a smaller, lateral, and a larger, medial portion.
Cutaneous innervation of the upper limbs is the nerve supply to areas of the skin of the upper limbs (including the arm, forearm, and hand) which are supplied by specific cutaneous nerves. Modern texts are in agreement about which areas of the skin are served by which cutaneous nerves, but there are minor variations in some of the details.
The median nerve innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, the first and second lumbricals. The ulnar nerve innervates the remaining intrinsic muscles of the hand. [3] [4] All muscles of the hand are innervated by the brachial plexus (C5–T1) and can be classified by innervation: [1] [4] [5]
The volar branch (ramus volaris; anterior branch), the larger, passes usually in front of, but occasionally behind, the vena mediana cubiti (median basilic vein).. It then descends on the front of the ulnar side of the forearm, distributing filaments to the skin as far as the wrist, and communicating with the palmar cutaneous branch of the ulnar nerve.
Median nerve palsy is often caused by deep, penetrating injuries to the arm, forearm, or wrist. It may also occur from blunt force trauma or neuropathy. [2] Median nerve palsy can be separated into 2 subsections—high and low median nerve palsy. High MNP involves lesions at the elbow and forearm areas.