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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]
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. Low median nerve palsy results from lesions at the wrist. Compression at the different levels of the median nerve produce variable symptoms and/or syndromes. [citation needed] The areas are:
In the human body, the carpal tunnel or carpal canal is a flattened body cavity on the flexor (palmar/volar) side of the wrist, bounded by the carpal bones and flexor retinaculum. It forms the passageway that transmits the median nerve and the tendons of the extrinsic flexor muscles of the hand from the forearm to the hand. [1]
The median nerve provides feeling or sensation to the thumb, index finger, long finger, and half of the ring finger. At the level of the wrist, the median nerve supplies the muscles at the base of the thumb that allow it to abduct, move away from the other four fingers, as well as move out of the plane of the palm.
This muscle originates from the medial epicondyle of the humerus as part of the common flexor tendon. It runs just laterally of flexor digitorum superficialis and inserts on the anterior aspect of the base of the second metacarpal , and has small slips to both the third metacarpal and trapezium tuberosity.
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.
The anterior interosseous nerve classically innervates 2.5 muscles: which are deep muscles of the forearm flexor pollicis longus; pronator quadratus; the radial (lateral) half of flexor digitorum profundus (inserting on the second and third digits) and the inferior radioulnar, wrist and carpal joints.