Carpal tunnel syndrome is a progressively painful hand and arm condition caused by a pinched nerve in the wrist, the median nerve. A number of factors can contribute to this such as the anatomy of the wrist, underlying health problems and patterns of hand use. The carpal tunnel is a narrow passage way about as big around as your thumb on the palmar side of the wrist. The tunnel protects a main nerve to your hand and 9 tendons that bend your fingers. Compression of this nerve produces numbness, pain and eventually hand weakness and loss of coordination.