Carpal tunnel syndrome (CTS) is a collection of characteristic symptoms and signs that occurs following compression of the median nerve within the carpal tunnel. Usual symptoms include numbness, paresthesias, and pain in the median nerve distribution. These symptoms may or may not be accompanied by objective changes in sensation and strength of median-innervated structures in the hand. [1, 2] See image below.
Until the advent of electrophysiologic testing in the 1940s, carpal tunnel syndrome (CTS) commonly was thought to be the result of compression of the brachial plexus by cervical ribs and other structures in the anterior neck region. It is now known that the median nerve is damaged within the rigid confines of the carpal tunnel, initially undergoing demyelination followed by axonal degeneration. Sensory fibers often are affected first, followed by motor fibers. Autonomic nerve fibers carried in the median nerve also may be affected.
The cause of the damage is subject to some debate; however, it seems likely that abnormally high carpal tunnel pressures exist in patients with CTS. This pressure causes obstruction to venous outflow, back pressure, edema formation, and ultimately, ischemia in the nerve.
The risk of development of CTS appears to be associated, at least in part, with a number of different epidemiologic factors, including genetic, medical, social, vocational, avocational, and demographic.  A complex interaction probably exists between some or all these factors, eventually leading to the development of CTS. Definite causative factors, however, are far from clear.
The incidence of carpal tunnel syndrome is 1-3 cases per 1000 subjects per year; prevalence is approximately 50 cases per 1000 subjects in the general population. Incidence may rise as high as 150 cases per 1000 subjects per year, with prevalence rates greater than 500 cases per 1000 subjects in certain high-risk groups.
A paucity of population-based studies of carpal tunnel syndrome (CTS) exists; however, the incidence and prevalence in developed countries seems similar to the United States (eg, incidence in the Netherlands is approximately 2.5 cases per 1000 subjects per year; prevalence in the United Kingdom is 70-160 cases per 1000 subjects). [4, 5, 6] CTS is almost unheard of in some developing countries (eg, among nonwhite South Africans).
Carpal tunnel syndrome is not fatal, but it can lead to complete, irreversible median nerve damage, with consequent severe loss of hand function, if left untreated.
Whites are probably at highest risk of developing carpal tunnel syndrome (CTS). The syndrome appears to be very rare in some racial groups (eg, nonwhite South Africans).  In North America, white US Navy personnel have CTS at a rate 2-3 times that of black personnel. 
The female-to-male ratio for carpal tunnel syndrome is 3-10:1.
The peak age range for development of carpal tunnel syndrome (CTS) is 45-60 years. Only 10% of patients with CTS are younger than 31 years.
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