Carpal Tunnel Syndrome

© Reed Group

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).

History: Individuals may describe pain, tingling, numbness, or a feeling of weakness in the wrist, hand, or fingers. In mild cases, the symptoms are intermittent and often worsen at night or when the individual first arises in the morning. The individual may complain of decreased grip strength, dropping items more frequently than usual, and having problems pinching or grasping items or making a fist. The fingers may at times feel "locked," and the individual may feel a need to shake the hand and fingers to unlock them. On occasion, pain may radiate into the forearm, shoulder, neck, or chest. The hands or lower arms may feel weak in the morning after sleeping with wrists flexed. Performance of detailed tasks such as writing or tying shoes may be difficult. Symptoms may occur during specific activities or at particular times, such as while holding a phone or a newspaper, gripping a steering wheel, or sleeping. The individual may not be sensitive to hot and cold by touch.

Physical exam: The physical exam may reveal no abnormalities. Subjectively altered sensation may be noted in the distribution of the median nerve in the thumb and the first three fingers, with no changes in sensation in the palm. Even though patients frequently complain of "swelling," soft tissue swelling is not usually observed in CTS. In chronic or severe cases, the palm may appear to be wasting away near the thumb (thenar eminence atrophy). In severe cases, weakness of thumb opposition and decreased sensation in the distal phalanges of the thumb and first three fingers (2 point discrimination and/or monofilament testing) may be noted. The individual may be shown a diagram of the hand and wrist to indicate where pain or other sensations are present. An unaffected little finger may indicate CTS.

Tapping on the volar aspect of the wrist over the course of the median nerve near the front of the wrist typically reproduces the tingling feeling in the hand or forearm (Tinel's sign). Positioning the wrist in a fully flexed posture for 60 seconds may reproduce the pain and tingling (Phalen's sign). These methods have a high rate of both false positive and false negative findings. Hand grip strength test may show weakness.

Tests: Electrodiagnostic nerve tests are performed to evaluate nerve function (e.g., nerve conduction velocity, electromyography). Nerve conduction tests apply small electric shocks and measure the speed with which nerves are able to transmit impulses. Mild cases may show prolonged motor and/or sensory distal latency of the median nerve and slowing of the conduction speed in the carpal tunnel. Moderate cases show conduction block, in which some of the axons or nerve fibers fail to transmit impulses, resulting in decreased amplitude (voltage) on nerve conduction. Severe cases, which are uncommon, show significant prolongation of motor latency and reduced conduction speed, evidence of axon loss or death of some of the axons in the nerve. There is no agreement about the definitions of mild, moderate, or severe CTS with regard to electrodiagnostic testing, but abnormal results on nerve conduction tests confirm CTS.

Electromyography involves insertion of a fine needle into a muscle and recording of the electric impulses so that electrical activity seen on a monitor can reveal damage to the nerve supplying the muscle tested. The most severe cases will show voltage or at least conduction block), suggesting more severe nerve injury.

Blood tests (serology) to detect possible underlying rheumatoid arthritis (sedimentation rate), diabetes, and thyroid disease are frequently performed. Plain film x-rays of the wrist are used to rule out bony abnormalities, but are almost always normal. MRI and ultrasound are currently considered to be experimental methods of evaluating for the presence of CTS. If a tumor in the carpal tunnel is a rare but possible explanation for an individual's carpal tunnel syndrome, MRI may be used.

Conservative management remains effective in most cases of carpal tunnel syndrome. After a diagnosis of CTS, reduction of the symptoms and the identification of activities that increase the symptoms, both at home and at work, are the first goals. Individuals should receive therapy from an occupational therapist, a physical therapist, or a hand therapist (Gerritsen, "Conservative Treatment Options"). The first objective of therapy is to reduce pain and swelling, using modalities such as heat and cold (Braddom). The hand and wrist are elevated to reduce swelling and may be positioned in a static resting hand splint to decrease movement in the painful region and to provide proper alignment (Gerritsen, "Splinting vs Surgery"; Muller; O'Connor). After pain is consistently reduced, activities to increase muscle flexibility, range of motion, strength, and body posture are a second objective. During this stage the therapist also monitors sensory status and, if deficits are noted, provides sensory re-education (Muller). Patient education also addresses awareness of body posture during task performance. An ergonomic evaluation may also be beneficial (Wilson). Clinicians and therapists must work with the individual to devise plans that reduce activities that increase the symptoms in the course of daily activities to increase overall comfort and function. In the workplace, modified work is important until symptoms resolve. This needs to be specifically addressed with company representatives if possible. Some have programs with alternative work options. Additional information may provide insight into the rehabilitation needs of these individuals (Evans).