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Carpal tunnel syndrome (CTS) is a condition in which thickened tendons or ligaments in the wrist compress the median nerve that runs from the forearm to the hand. The median nerve is the main nerve of the hand. Its branches enter the hand through a narrow passageway (carpal tunnel) formed by the wrist bones (carpal bones) and the tough membrane that holds the tendons in place (transverse carpal ligament). The median nerve supplies sensation to the thumb, index finger, middle finger, and, in most people, to part of the ring finger. Because this passageway is rigid, thickening of structures, inflammation, swelling, or increased fluid retention may compress the nerve (nerve entrapment), causing pain and numbness in the fingers (particularly the thumb and the index and middle fingers) and serious hand weakness. Pain may eventually extend to the arm, shoulder, or rarely even the neck. Sensation in the palm is not affected because the branch of the median nerve to the palm does not go through the carpal tunnel.
Any condition, trauma, or injury that increases pressure on the median nerve and tendons in the carpal tunnel can result in carpal tunnel syndrome, including a smaller carpal tunnel than normal, wrist injury such as sprains or fractures that produce swelling and alter the shape and size of the carpal tunnel, overactive pituitary gland, underactive thyroid, synovitis of rheumatoid arthritis, repeat use of vibrating hand tools, fluid retention during pregnancy or menopause, or the presence of a cyst or tumor.
Risk: Specific risk factors for carpal tunnel syndrome remain controversial; there are few clinical data to show that repetitive or forceful hand and wrist movement can result in carpal tunnel syndrome. No single ergonomic risk factor is sufficient; multiple, simultaneous ergonomic risk factors must be present for work or recreational activity to contribute to development of carpal tunnel syndrome. Possible ergonomic risk factors include any type of activity that involves highly repetitive wrist motion, holding the wrist in awkward positions for sustained periods of time, forceful pinching or gripping, and work-task stresses. Examples might include working for long periods of time with vibrating power tools or performing heavy assembly line work. Excessive typing or computer work was in the past suspected by clinicians to have contributed to the risk of CTS.
Underlying conditions that may increase the risk of developing CTS include rheumatoid arthritis, renal failure, diabetes mellitus, acromegaly, multiple myeloma, amyloidosis, obesity, recent tuberculosis, and bacterial or fungal infection that spreads into the carpal tunnel.
Carpal tunnel syndrome is more common in those who develop trigger digit, elbow tendinopathy (epicondylitis), and ulnar nerve mononeuropathy at the elbow. Those associations raise the question of a congenital predisposition to musculoskeletal disorders.
Trauma or injury such as a wrist fracture that decreases the size of the carpal tunnel or wrist sprain that causes swelling of the synovial tissue covering the tendons in the carpal tunnel (tenosynovitis) may increase the risk of CTS. It may also occur in some individuals with degenerative neck conditions (cervical spondylosis). An increased frequency of CTS has been shown in alcoholics, and smokers may experience worse symptoms and a longer recovery time from CTS than nonsmokers.
Women are 3 times more likely to develop the syndrome than men because of their typically smaller carpal tunnel. Risk increases with advancing age. For women, the peak time for developing CTS is between ages 45 and 54. Women who are pregnant, taking oral contraceptives, or going through menopause are also more prone to develop the condition due to fluid retention ("Carpal Tunnel Syndrome"). Incidence and Prevalence: An estimated 5% of the US population is affected by carpal tunnel syndrome (Fuller). Only adults develop CTS (NINDS). |