Carpal tunnel syndrome (CTS) is a compression syndrome in which the median nerve is compressed on its way through the carpal tunnel at the wrist. The carpal tunnel is formed by the carpal bones and the flexor retinaculum.

Typical complaints are tingling and numbness in the thumb, index and middle fingers and the radial half of the ring finger. Symptoms frequently occur at night. In advanced stages, weakness of the thenar muscles may develop.