The small bones which form the universal joint of the wrist are arranged in an arc. A big strong ligament sits across the front of this arc forming the roof of the carpal tunnel. Through the carpal tunnel, pass the tendons that drive the fingers and thumb together with the main nerve that supplies the thumb side of the hand – this is the median nerve.
Carpal tunnel syndrome results from increased pressure in the carpal tunnel causing pressure on the median nerve. It presents as numbness and tingling on the thumb side of the hand and sometimes weakness in the thumb.
Ageing can cause thickening of the lining of the carpal tunnel and pressure on the nerve, but sustained physical activity or pregnancy can cause thickening around the tendons which also compromise the volume of the carpal tunnel and cause pressure on the nerve.
The hand may go to sleep with sustained activity through the day or, as we tend to sleep with our wrist flexed, this further compromises the carpal tunnel and not infrequently causes waking at night. Splinting can be effective in reducing the wakening. Surgery is sometimes indicated.