Carpal tunnel syndrome. Carpal tunnel syndrome is a condition in which there is excessive pressure on the median nerve. This is the nerve in the wrist that allows feeling and movement to parts of the hand. Carpal tunnel syndrome can lead to numbness, tingling, weakness, or muscle damage in the hand and fingers. The median nerve provides feeling and movement to the thumb side of the hand. This includes the palm, thumb, index finger, middle finger, and thumb side of the ring finger.