Carpal tunnel syndrome causes pain and tingling in the hand and the fingers. Usually the thumb, index and middle finger are affected because the median nerve branches supply these fingers.
The median nerve gives off a branch before the carpal tunnel, which supplies the skin over the front of the thumb. This is called the Palmar Cutaneous Branch. Because it comes off before the carpal tunnel this area is often not involved in Carpal Tunnel Syndrome.
The median nerve gives off a motor nerve branch to the muscles that power the thumb. These muscles are the small muscles that give shape to the front of the hand. In severe carpal tunnel syndrome these muscles can become paralysed. The thumb will still be able to bend, but it won't move away from the hand, and so the pinch becomes very weak. Weak pinch can be hugely debilitating for activities of daily living.
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