Carpal tunnel syndrome is a condition that affects one of the primary nerves in the wrist area. The carpal tunnel is a narrow passageway surrounded by bones and ligaments on the palm side of the hand. The leading cause of carpal tunnel syndrome is extra pressure on the median nerve at the wrist inside the tunnel. The extra pressure can come from swelling or inflammation of the contents inside the tunnel. Carpal tunnel syndrome symptoms include wrist pain, numbness, tingling, and weakness.