The median nerve in the wrist is a major nerve that passes from the forearm, through the carpal tunnel, into the hand, providing sensation to the palm side of the thumb, index, middle, and part of the ring fingers, and controlling muscles at the base of the thumb.
In-Depth Explanation
Anatomy and Location
The median nerve originates in the brachial plexus, a network of nerves in the shoulder and neck. It travels down the arm, forearm, and eventually enters the wrist. In the wrist, it passes through a narrow passageway called the carpal tunnel. This tunnel is formed by bones on three sides and a tough ligament (the transverse carpal ligament) on the fourth. After passing through the carpal tunnel, the median nerve branches out to supply sensory and motor functions in the hand.
Function
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Sensory Function: The median nerve provides sensation to the skin on the palmar (palm) side of the thumb, index finger, middle finger, and the radial (thumb-side) half of the ring finger.
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Motor Function: The median nerve controls the thenar muscles, which are located at the base of the thumb and are responsible for movements such as thumb abduction (moving the thumb away from the hand), opposition (touching the thumb to the other fingers), and flexion (bending the thumb across the palm).
Clinical Significance
The median nerve is often involved in a common condition called carpal tunnel syndrome. This occurs when the median nerve becomes compressed within the carpal tunnel, leading to symptoms such as:
- Numbness and tingling in the thumb, index, middle, and radial half of the ring finger.
- Pain in the wrist and hand.
- Weakness in the hand, particularly in the thumb muscles.
- Symptoms often worse at night.
Carpal tunnel syndrome can be caused by a variety of factors, including repetitive hand movements, pregnancy, arthritis, and trauma to the wrist. Treatment options include conservative measures such as splinting and physical therapy, as well as surgical release of the transverse carpal ligament to relieve pressure on the median nerve.
