Carpal tunnel syndrome (CTS) is a disorder that causes pain and weakness in the hand and wrist. CTS develops from problems in the nerves of the hands -- not the muscles, as some people believe. The symptoms of CTS can range from mild to incapacitating.
The Carpal Tunnel and Median Nerve
To understand how carpal tunnel syndrome arises, it is important to know the parts of the hand and wrist that are involved.
The Carpal Tunnel. The carpal tunnel is a passageway that forms beneath the strong, broad transverse ligament. This ligament is a bridge that extends across the lower palm and connects the bones of the wrist (carpals) that form an arch below the tunnel.
The Median Nerve and Flexor Tendons. The median nerve and nine flexor tendons pass under the ligament bridge and through the carpal tunnel (similar to a river). They extend from the forearm up into the hand:
- The flexor tendons are fibrous cords that connect the muscles in the forearm to the fingers (two to each finger and one to the thumb). They allow flexing of the fingers and clenching of the fist.
- The median nerve plays two important roles. It supplies sensation to the palm side of the thumb, index, middle, and ring fingers, and to the flexor tendons. It provides function for the muscles at the base of the thumb (the thenar muscle).
Review Date: 02/17/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.