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Causes
By Mayo Clinic staffThe cause of carpal tunnel syndrome is pressure on the median nerve. The median nerve is a mixed nerve, meaning it has a sensory function and also provides nerve signals to move your muscles (motor function). The median nerve provides sensation to your thumb, index finger, middle finger and the middle-finger side of the ring finger.
Pressure on the nerve can stem from anything that reduces the space for it in the carpal tunnel. Possible causes include:
- Other health conditions. Some examples include rheumatoid arthritis, certain hormonal disorders — such as diabetes, thyroid disorders and menopause — fluid retention due to pregnancy, or deposits of amyloid, an abnormal protein produced by cells in your bone marrow.
- Repetitive use or injury. Repetitive flexing and extending of the tendons in the hands and wrists, particularly when done forcefully and for prolonged periods without rest, also can increase pressure within the carpal tunnel. Injury to your wrist can cause swelling that exerts pressure on the median nerve.
- Physical characteristics. It may be that your carpal tunnel is more narrow than average.
- Carpal tunnel syndrome fact sheet. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/carpal_tunnel/detail_carpal_tunnel.htm. Accessed Dec. 5, 2008.
- Carpal tunnel syndrome. American Academy of Orthopaedic Surgeons. http://orthoinfo.aaos.org/topic.cfm?topic=a00005. Accessed Dec. 5, 2008.
- Carpal tunnel syndrome. American Society for Surgery of the Hand. http://www.assh.org/Content/NavigationMenu/PatientsPublic/HandConditions/CarpalTunnelSyndrome/Carpal_Tunnel_Syndr.htm. Accessed Dec. 5, 2008.
- Sheon RP. Clinical manifestations and diagnosis of carpal tunnel syndrome. http://www.uptodate.com/home/index.html. Accessed Nov. 25, 2008.
- Sheon RP. Etiology of carpal tunnel syndrome. http://www.uptodate.com/home/index.html. Accessed Nov. 25, 2008.
- Scott KR, et al. Treatment of carpal tunnel syndrome. http://www.uptodate.com/home/index.html. Accessed Nov. 25, 2008.
- Hunter AA, et al. Surgery for carpal tunnel syndrome. http://www.uptodate.com/home/index.html. Accessed Nov. 25, 2008.
