Carpal tunnel syndrome (CTS) is a condition caused by compression of the median nerve as it passes through a short tunnel in the wrist. The bones of the wrist joint form a C shape, which has a fibrous roof. The nerve and the tendons that bend the fingers and thumb all pass through this tunnel (see diagram). Anything that reduces the space available in this tunnel will squash the softest structure, which unfortunately is the nerve.
CTS may be related to pregnancy, diabetes, thyroid disease and rheumatoid arthritis, as well as trauma and other rarer conditions. Though many people will have none of these problems. Symptoms of CTS include tingling, pins and needles or numbness mainly in the thumb, index and middle fingers; clumsiness and pain in the hand and forearm can also occur. With severe symptoms there may be wasting of the muscles at the base of the thumb.
The diagnosis of CTS can normally be made by listening to the symptoms that you describe and the examination performed in the clinic. Sometimes if it is not clear further tests such as nerve conduction studies or ultrasound scan may be used.