- Clinical science
The median nerve is a peripheral nerve originating in the cervical roots C5–T1 of the brachial plexus. It supplies motor innervation to the anterior forearm flexors, the thenar muscles, and the two lateral lumbricals as well as sensory innervation to the lateral palm and anterior, lateral three and a half fingers. Motor and sensory deficits depend on whether the lesion is proximal (above the elbow) or distal (below the elbow). While proximal lesions present with the “hand of benediction,” distal lesions present with either the “pinch sign” (anterior interosseous nerve syndrome) or, in the case of , with mildly impaired thumb and index finger motion. Both proximal lesions and carpal tunnel syndrome result in reduced sensation in the area of the thumb, index and middle finger. Anterior interosseus nerve syndrome does not cause any sensory deficits. Chronic injuries to the nerve result in atrophy of median nerve innervated muscles while acute injuries do not have this feature. Treatment is mostly conservative and focuses on rest and immobilization.
- Traumatic: e.g., fractures (humerus fracture causing proximal lesion), carpal bone dislocations, or penetrating injuries (gunshots, lacerations, etc)
- Chronic compression; : e.g., in the carpal tunnel (see ; ) or between the forearm muscles (anterior interosseous nerve syndrome) or by a nerve sheath tumor (schwannoma of the median nerve)
The median nerve runs from the axilla to the elbow, in the medial side of the arm in the medial bicipital groove. It enters the forearm through the two heads of the pronator teres muscle. After branching off into a motor nerve (anterior interosseous nerve), it courses distally between the superficial and deep layers of the forearm's flexor compartment to reach the wrist, where it branches off into a sensory nerve (the palmar cutaneous branch of the median nerve) before entering the hand through the carpal tunnel.
|Location||Motor deficit||Sensory deficit|
|Proximal (above elbow)|| |
|Distal (below elbow)|| |
|Distal (within wrist)|| || |
A high/proximal lesion of the median nerve manifests in the hand of benediction, while a low/distal lesion does not!
- Bottle sign
In the case of , the following signs are also present:
- Nerve conduction study
- Electromyography (EMG)
- Avoid repetitive wrist activities
- See treatment for