The United States government has recognized that repetitive-stress injuries represent a major source of pain and disability for office and factory workers. The most common repetitive-stress injury to the upper extremity is Carpal Tunnel Syndrome (CTS). In a study of all claims accepted by the US Department of Labor, Office of Workers' Compensation Programs (OWCP), from 1993 through 1994, CTS was one of the most costly diagnoses and represented the highest in expenditures for surgical services [1]. Although the study indicated that while CTS represented a relatively small percentage of all workers' compensation cases, the health care and indemnity costs were considerable. The Occupational Safety and Health Administration (OSHA) is now prepared to require employers to install ergonomics programs to help minimize and prevent these injuries. With the advent of home computers, more people are experiencing this repetitive-stress injury during their personal time, too. Untreated CTS can result in prolonged symptoms of pain and disability and permanent nerve damage. Find out what CTS is, how it is diagnosed, what the possible causes are, and what can be done for prevention and treatment in this article.

What is Carpal Tunnel Syndrome?
Carpal Tunnel Syndrome (CTS) is a compression of the median nerve in the carpal tunnel of the wrist. If you turn your palm up and look at your wrist, you can see and feel some of the flexor tendons of the wrist and fingers as they cross over the carpal tunnel. The tunnel actually contains nine tendons that are involved in flexing the wrist and fingers, as well as the median nerve. A thick ligament called the transverse carpal ligament or flexor retinaculum forms the top of the tunnel and covers the tendons on the palm side of the hand and the carpal bones of the hand form the bottom of the tunnel. When the wrist is in a neutral position or straight, the most room for the tendons exists. However, when the wrist is flexed (held downward), the space decreases and there is more potential for nerve compression. When the median nerve is compressed by the transverse carpal ligament, it causes the signs and symptoms of CTS.

Signs, Symptoms, and Diagnosis
The signs and symptoms of CTS are numbness, tingling, and pain in the thumb, index, middle, and half of the ring finger, weak thumb movements, and weakness in rotating the hand palm down (pronation) or in flexing the wrist [2]. Patients usually complain of pain at night and of dropping things. There are two prominent clinical tests that are performed to help determine a CTS diagnosis. Phalen’s test is positive if tingling of the fingers is felt when the hands are pressed together for more than sixty seconds while they are both flexed downward [3]. A Tinel's sign is exhibited when tapping over the tunnel results in tingling throughout the median nerve distribution. Electromyography and nerve conduction velocity tests are also used to help verify a CTS diagnosis.

What Causes Carpal Tunnel Syndrome?
There are many reasons why the median nerve gets compressed in the carpal tunnel. One common cause of CTS is overuse or cumulative trauma. Constant wrist flexion, repetitive wrist flexion and extension, along with wrist rotation and finger flexion (gripping) can cause tendinitis (inflammation) of the flexor tendons. This chronic swelling can lead to a fibrosis or thickening of the transverse carpal ligament. One study of 352 workers from three different companies showed that repetitiveness of work was found to be significantly associated with a prevalence of reported discomfort in the wrist, hand, or fingers and a strong association with carpal tunnel syndrome [4]. Improper workstation set-up, asymmetrical task performance, and repetition without rest breaks can also contribute to cumulative trauma. Sports and recreational activities that can lead to CTS are lacrosse, gymnastics, cycling, throwing sports, racquet sports, knitting, needlepoint, piano playing, cooking, computer games, and typing, to name a few. Even serious weightlifters whose muscles hypertrophy (enlarge) and take up too much space in the carpal tunnel could be at risk [5]. CTS can also be related to systemic medical illnesses like diabetes, hypothyroidism, and rheumatoid arthritis. Acute trauma, where the wrist is hit and the contents of the carpal tunnel are injured, can be a cause of CTS. In addition, several cases have been made for CTS originating from congenital defects, wrist shape, and pregnancy. There have been studies to show that obesity may be related statistically to CTS [6]. And sometimes, there is no known cause, as in idiopathic CTS.

Treatment
Typical conservative treatment involves modalities like ice and ultrasound to decrease inflammation. Avoiding gripping or pinching activities, especially with the wrist flexed, and wearing a splint can calm down tendinitis. Stretching and strengthening the wrist and finger flexors and extensors when the acute phase is over and performing nerve and tendon glide exercises are part of a physical therapy protocol
As far as pharmacological and surgical interventions go, conservative treatment with drugs is attempted first before a surgical carpal tunnel release is performed. Non-steroidal anti-inflammatory medications are sometimes prescribed, but oral corticosteroids have shown to be more effective [7]. A single injection with steroids close to the carpal tunnel may result in long term improvement and should be considered before surgical decompression [8].
Alternative medicine has shown some promise in treating CTS. A yoga-based regimen was found more effective than wrist splinting or no treatment in relieving some symptoms and signs of carpal tunnel syndrome [9]. The yoga consisted of 11 yoga postures designed for strengthening, stretching, and balancing each joint in the upper body along with relaxation given twice weekly for 8 weeks. With regards to acupuncture, even the National Institute of Health (NIH) believes that acupuncture may be useful as an adjunct treatment to be included in a comprehensive management program or as an acceptable alternative.
In reviewing 12 years of CTS outcomes, researchers concluded that the limited evidence available indicated: 1) steroid injections and oral use of B6 were associated with pain reduction; 2) in comparison to splinting, range of motion exercises appeared to be associated with less pain and fewer days to return to work; 3) cognitive behavior therapy yielded reductions in pain, anxiety, and depression; and, 4) multidisciplinary occupational rehabilitation was associated with a higher percentage of chronic cases returning to work. They also lamented that despite the emerging evidence that the cause of CTS is multifactorial, the majority of outcome studies have focused on only on single interventions directed at individual factors [10].

Prevention
Prevention can be as simple as good strength and flexibility and monitoring repetitive wrist motions and gripping activities. Research has suggested that reducing the duration, frequency, or intensity of exposure to forceful repetitive work, extreme wrist postures, and vibration is likely to result in a reduction of the incidence or severity of CTS in working populations [11].
Ergonomics or the way a workstation is designed can be of significant importance. Proper positioning of furniture (like desks and chairs) and equipment (like computers) will result in correct posture and placement of the wrists during typing. The wrists should be straight and even, not bent up or down. Using different geometric keyboards or ergonomically designed mice can decrease the chance of CTS [12]. Taking frequent rest breaks and developing consistent work/rest cycles, where during the rest cycle some type of stretching movement is performed, can also help prevent CTS.

References
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2. Tortora, G.J. and S.R. Grabowski, Principles of Anatomy and Physiology. Eighth ed. 1996, New York: HarperCollins College Publishers. 380.
3. Phalen, G.S., The carpal-tunnel syndrome. Clinical evaluation of 598 hands. Clin Orthop, 1972. 83: p. 29-40.
4. Latko, W.A., et al., Cross-sectional study of the relationship between repetitive work and the prevalence of upper limb musculoskeletal disorders. Am J Ind Med, 1999. 36(2): p. 248-259.
5. Weinstein, S.M. and S.A. Herring, Nerve problems and compartment syndromes in the hand, wrist, and forearm. Clin Sports Med, 1992. 11(1): p. 161-188.
6. Lam, N. and A. Thurston, Association of obesity, gender, age and occupation with carpal tunnel syndrome. Aust N Z J Surg, 1998. 68(3): p. 190-193.
7. Chang, M.H., et al., Oral drug of choice in carpal tunnel syndrome. Neurology, 1998. 51(2): p. 390-393.
8. Dammers, J.W., M.M. Veering, and M. Vermeulen, Injection with methylprednisolone proximal to the carpal tunnel: randomised double blind trial [In Process Citation]. Bmj, 1999. 319(7214): p. 884-886.
9. Garfinkel, M.S., et al., Yoga-based intervention for carpal tunnel syndrome: a randomized trial [see comments]. Jama, 1998. 280(18): p. 1601-1603.
10. Feuerstein, M., et al., Clinical management of carpal tunnel syndrome: a 12-year review of outcomes. Am J Ind Med, 1999. 35(3): p. 232-245.
11. Viikari-Juntura, E. and B. Silverstein, Role of physical load factors in carpal tunnel syndrome. Scand J Work Environ Health, 1999. 25(3): p. 163-185.
12. Tittiranonda, P., et al., Effect of four computer keyboards in computer users with upper extremity musculoskeletal disorders. Am J Ind Med, 1999. 35(6): p. 647-661.