What causes carpal tunnel?

Usually unknown: Pregnancy, hypothyroid, repetitive stress injury.

Nerve compression: Carpal tunnel syndrome is compression of the median nerve in the wrist. Common causes are repetitive stress and pregnancy. Typical symptoms are burning and tingling in the hands at night.

Median n compression: Carpal tunnel syndrome is caused by compression of the median nerve at the wrist. This is usually worse in the dominant hand and more common in typist and people using jackhammer. There is repetitive motion of the wrist. Symptoms include weakness opening jars and numbness of thumb to ring finger. Often pain will wake one up at night and is relieved with shaking of the hand.

See below: The median nerve becomes compressed by the transverse carpal ligament that forms the roof of the carpal tunnel as it passes through the carpal tunnel.