CTS from WebMd

The carpal tunnel is the passageway in the wrist and is made
up of the arching carpal bones (eight bones in the wrist) and the ligament
connecting the pillars of the arch (the transverse carpal ligament). The median
nerve and the tendons that connect the fingers to the muscles of the forearm
pass through the tightly spaced tunnel.
Carpal tunnel syndrome occurs when
the median nerve becomes pinched due to swelling of the nerve or tendons or
both. The median nerve provides sensation to the palm side of the thumb, index,
middle fingers, as well as the inside half of the ring finger and muscle power
to the thumb. When this nerve becomes pinched, numbness, tingling and sometimes
pain of the affected fingers and hand may occur and radiate into the
forearm.

While there are many possible causes of carpal tunnel
syndrome, the vast majority of people with the condition have no known
cause.
However, we do know that excessive repetitive movements of the arms,
wrists or hands can aggravate the carpal tunnel bringing out the symptoms of
carpal tunnel syndrome. Untreated, this can become chronic, but when detected
early, carpal tunnel syndrome can be treated and recovery is possible in a few
months. Severe carpal tunnel syndrome can also be treated, but recovery may take
up to a year or longer and may not be complete.

source- webmd.com