Median Nerve

It is a branch of brachial plexus and supplies motor inervation to the flexor muscles of forearm and short muscles of hands, and sensory innervation to the palmar aspect of later three and half phalanges and palm. Where does the median nerve lie? What does the median nerve innervate? How is the median nerve compressed? The above query has been answered below in detail.

Origin of median nerve

It is formed by the lateral and medial roots of median nerve originated from lateral and medial cord of brachial plexus respectively.

Where does the median nerve lie?

It arises from the axilla as mentioned above and descends in the arm lateral to the brachial artery whereas in the lower arm it crosses the brachial artery and descends medial to the brachial artery. In cubital fossa it passes medial to brachial artery, gives muscular branches and anterior interosseous nerve, proximal to the heads of pronator teres muscle, which descends anterior to interosseous membrane; and enters the forearm. Here it travels between the two heads of pronator teres muscles and descends between the plane of flexor digitorum superficialis and flexor digitorum profundus muscles. Just before the wrist it gives palmar cutaneous branch that descends superficial to flexor retinaculum whereas the median nerve passes beneath the flexor retinaculum in which it gives a branch, recurrent branch of median nerve, and continues as palmar digital branch of median nerve.  

Branches of median nerve; and what does the median nerve innervate?

It gives muscular branches to the flexor muscles of forearm (pronator teres, flexor carpi radialis, palmaris longus and flexor digitorum superficialis) and anterior interosseous nerve that innervates flexor policis longus, pronator quadratus and radial part of flexor digitorum profundus. Just proximal to flexor retinaculum it gives palmar cutaneous branch that provides sensory supply to thenar eminence and proximal palmar region, and in flexor retinaculum it branches off recurrent branch that supplies thenar muscles (abductor pollicis brevis, flexor pollicis brevis and opponens pollicis) and continues as palmar digital branch of median nerve that supplies palmar aspect of lateral three and half fingers.

What is median nerve compression?

Carpal tunnel is the most common site of median nerve compression. It also known as carpal tunnel syndrome. Carpal tunnel is a fibro-osseous tunnel formed by flexor retinaculum and carpal bones. Repetitive wrist movement, wrist injuries and certain medical conditions such as hypothyroidism or diabetes mellitus can lead to compression of the nerve in that area. It causes tingling sensation in the palmar aspect of lateral three and half fingers and thenar muscles wasting and pain in that region. Analgesics and decompression of nerve can ameliorate the symptoms.  

Common sites of median nerve injury

The nerve is injured often at elbow and wrist joint. The injuries associated with particular location lead to distinct symptoms. Loss of sensation of lateral half of hand along with impaired flexion at wrist joint, and lateral metacarpophalangeal and interphalangeal joints take place if nerve damage at elbow joint whereas compression on nerve under carpal tunnel at wrist joint causes symptoms mentioned in carpal tunnel syndrome section above