Carpal Tunnel Syndrome
What Is Carpal Tunnel Syndrome?
The carpal tunnel is a passageway that runs from the forearm through the wrist. Bones form three walls of the tunnel and a strong, broad ligament bridges over them. The median nerve, which supplies feeling to the thumb, index, and ring fingers, and the nine tendons that flex the fingers, passes through this tunnel. This nerve also provides function for the muscles at the base of the thumb (the thenar muscles). Usually, carpal tunnel syndrome (CTS) is considered an inflammatory disorder caused by repetitive stress, physical injury, or medical conditions that cause the tissues around the median nerve to become swollen. The protective lining of the tendons within the carpal tunnel can become inflamed and swell or the ligament that forms the roof over the median nerve becomes thicker and broader and presses on it. Just as stepping on a hose slows the flow of water through a garden hose, so compression on the median nerve fibers by the swollen tendons and thickened ligament slows down the transmission of nerve signals through the carpal tunnel. The result is pain, numbness, and tingling in the wrist, hand, and fingers (except the little finger, which is not affected by the median nerve).
What Causes Carpal Tunnel Syndrome?
It is often very difficult to determine whether the cause of carpal tunnel syndrome is primarily due to work conditions or an underlying medical problem. CTS almost always occurs in adults and most adults work; carpal tunnel syndrome, then, is very likely to be associated with the work place whether or not it is actually caused by work itself. Indeed, estimates of work-related CTS vary wildly. Some studies suggest that more than half are due to workplace factors and others that few cases of CTS are actually caused by conditions on the job. In one study, for example, obesity or diseases such as diabetes, hypothyroidism, and arthritis occurred in the majority of people with work-associated CTS. Such conditions are known contributors to carpal tunnel disorder. It is most likely that many cases of CTS occur from a combination of factors, including a predisposing medical condition exacerbated by work stress and psychologic and social stressors. In most patients with CTS, an underlying cause for the disorder cannot be determined. The issue is clouded by economic concerns: carpal tunnel syndrome is a major contributor to workmen's compensation cases. It is in the employer's interest, therefore, to seek medical causes for hand and wrist pain, which are not covered by compensation costs, and it is in the employee's interest to relate the pain to the job so that the carpal tunnel disability is covered.
Repetitive Stress, High Force, Vibration, and Poor Posture. Researchers have found evidence of a positive association between CTS and highly repetitive work, high force, vibration, and poor posture, with the evidence being very strong when these factors are combined. In 1994 330,000 disorders related to work requiring repetitive motion were reported, an increase of 10% over 1993 and 15% over 1992 figures. High force and work involving vibration have also been strongly associated with CTS. In addition to carpal tunnel syndrome, such work related disorders are referred to by several different terms: repetitive stress injuries, cumulative trauma disorder, overuse syndromes, and chronic upper limb pain syndrome. All of these problems are generally associated with repetitive and forceful use of the hands that damage muscles and bones of the upper extremities. One study indicated that repetitive motion disorders account for nearly half of all reported work-related illness, of which carpal tunnel syndrome is estimated to account for 41%. Incorrect posture also may play a role in the development of CTS in people who work at computer and other types of keyboards. The tendency to roll the shoulders forward, round the lower back, and thrust the chin forward can shorten the neck and shoulder muscles, compressing nerves in the neck. This, in turn, can affect the wrist, fingers, and hand. Evidence is not as strong for a causal relationship, because people with poor posture may also have physical abnormalities that increase the risk for CTS.
PsychosocialFactors in the Workplace. Studies indicate that psychosocial factors in the workplace, such as intense deadlines, interpersonal relationships, and job design, are major contributors to carpal tunnel pain. Such psychosocial conditions are more likely to be important factors in contributing to CTS in office workers, although they also complicate the condition in workers whose work is primarily physical. [ See also,Who Gets Carpal Tunnel Syndrome,below.]
Injuries and Medical Conditions
A multicenter team recently reported that underlying medical conditions may be more likely to cause CTS than repetitive movements linked to work. In the study, 40% of patients diagnosed with CTS had conditions that could account for nerve disorder; they included obesity, diabetes, and autoimmune disorders, such as hypothyroidism, rheumatoid arthritis, and systemic lupus erythematosus. Only about 12% knew they had such conditions. Many of the underlying diseases that may be contributing to the development of CT are also associated with a more severe case. In a study of patients who had surgery for carpal tunnel syndrome, those with inflammatory arthritis (such as rheumatoid arthritis or lupus) were highly likely to have hand pain severe enough to require surgery. Hypothyroidism and diabetes also increased the risk for surgery. In autoimmune diseases, the body's immune system is abnormally attacking its own tissue, causing widespread inflammation, including in many cases in the carpal tunnel that results in median nerve entrapment. Some experts believe that carpal tunnel syndrome may actually be one of the first symptoms in a number of these diseases. Carpal tunnel syndrome can also be caused by multiple myeloma, Waldenstrom's macroglobulinemia, Down's syndrome, gout, and non-Hodgkin's lymphoma. Acromegaly, a disease that causes abnormally long bones, is a cause of CTS. One study also found that people with hepatitis C sometimes have symptoms of CTS. Bone dislocations and fractures can narrow the carpal tunnel, thereby exerting pressure on the median nerve. People who undergo hemodialysis are at risk for CTS caused by build-up in the hand of certain proteins called beta 2-microglobulin. Certain medications that effect the immune system, such as interleukin-2, which is administered to some cancer patients, may cause temporary CTS. There have been some reports of CTS caused by anticlotting drugs, such as warfarin.
Fluid retention during pregnancy or hormonal changes associated with menopause can cause swelling and symptoms of carpal tunnel syndrome.
Inherited and Inborn Factors
Some studies have reported a higher risk for carpal tunnel in people with a family history of the problem, indicating a genetic susceptibility in some people. In inherited carpal tunnel syndrome, the disorder is more likely to develop early on and in both hands than if it is caused by other factors. It should be noted, however, that inherited CTS is very rare. Some researchers are particularly interested in abnormalities in certain genes that regulate myelin, a fatty substance that serves as insulation for nerve fibers. Some people may be born with abnormalities of the carpal bones .
What Are the Symptoms of Carpal Tunnel Syndrome?
Symptoms of carpal tunnel syndrome usually progress gradually over weeks and months and, in some cases, years. The first symptoms may be pain in the wrist and hand or numbness and tingling of the index, middle, and ring fingers. They are often in both hands. Patients may also experience a sense of weakness and a tendency to drop things. They may lose the sense of heat and cold or feel that their hands are swollen even though there is no visible swelling. Symptoms may occur not only when the hand is being used but also when it is at rest. In fact, the disorder may be distinguished from similar conditions by pain occurring at night after going to bed. In some cases, labor-related CTS symptoms first occur outside of work, so patients may fail to associate the symptoms with work-related activity. Anyone with recurrent or persistent pain, numbness and tingling, or weakness of the hand should consult a physician for a diagnosis.
What Other Diseases Show the Same Symptoms As Carpal Tunnel Syndrome?
About 25% of patients with work-related repetitive stress disorders also have evidence of other similar conditions that resemble, but are not, carpal tunnel syndrome. A definitive diagnosis is often difficult. Most require treatments similar to those used for CTS: rest, immobilization, steroid injections, and even surgery if conservative management is unsuccessful.
Nerve Entrapment Disorders. Repetitive work can cause pressure on the median nerve in locations other than the wrist and can also affect other nerves in the arm and hand. The branch of the median nerve that runs through the palm of the hand can be damaged directly by repeated pounding or by the use of certain tools requiring a strong grip using the palm, such as needle-nosed pliers. The median nerve can also be pinched up in the forearm.
The ulnar nerve supplies sensation to the ring and little fingers. Like the median nerve, it too can become trapped as a result of repetitive stress, with subsequent loss of sensation in these fingers and the outer half of the palm. This condition, known as ulnar tunnel syndrome, can be a separate disorder or appear with CTS. In the latter case, release surgery for CTS usually also relieves the ulnar nerve entrapment. The ulnar nerve can also be affected at the elbow.
Tendon-Related Disorders. Tenosynovitis (swelling of the tendon sheath) in the hands and fingers is also a repetitive stress injury and can effect various parts of the hand and fingers. One or more fingers may feel painful and stiff, especially in the morning; the wrist may be swollen. Trigger finger (also called snapping finger) is a condition brought on when a tendon thickens, leaving the finger in a bent position. It is a common complication of rheumatoid arthritis; it also may occur in diabetes or for unknown causes. De Quervain's disease involves tenosynovitis at the base of the thumb. These disorders are often present with carpal tunnel syndrome.
Patients who have tendinitis (swelling of the tendon) feel pain in the involved area, which is intensified when they contract the muscles adjoining the tendon or when the physician stretches the affected finger or part of the hand.
Thoracic Outlet Syndrome
Pinched nerves in the neck may also cause weakness in the hands. A disorder known as thoracic outlet syndrome caused by compression of nerves and blood vessels running down the neck into the arm can cause symptoms very similar to CTS. The compression occurs at the first rib in the front of the shoulder. A physician may be able to diagnose the condition by detecting diminished blood flow in the arm as the patient raises the affected hand and turns his or her head toward the opposite side. Although the condition is uncommon, a correct diagnosis is important to differentiate it from CTS. Treatments for thoracic outlet syndrome are useless for CTS.
Arthritic conditions, including rheumatoid arthritis, gout, and osteoarthritis, can all cause pain in the hands and fingers.
Raynaud's phenomenon produces symptoms of numbness and tingling or pain in the fingers of one or both hands. It is usually brought on by cold or stress and is treated with warmth or, in severe cases, medications that may open blood vessels. People with this disorder, in fact, appear to be at higher risk for carpal tunnel syndrome and there may be some associations between the two conditions.
Who Gets Carpal Tunnel Syndrome?
A 1999 study in Sweden reported that 14% of the population surveyed complained of symptoms such as pain, numbness, and tingling in the hands, but only one in five of these people actually had CTS that could be confirmed through examination and testing. Estimates of risk for CTS vary from country to country, with relatively higher work-associated risks reported in the United States, for example. Older people are at higher risk than younger adults. It is very rare in children. The wide variation in severity and the difficulty in diagnosis make it hard to pinpoint specific figures.
People with Underlying Medical Conditions
A number of illnesses and injuries can predispose individuals to carpal tunnel syndrome, including autoimmune diseases and arthritic conditions. [For a detailed description see Injuries and Medical Conditions under What Causes Carpal Tunnel Syndrome? above.]
Workers at High Risk
At high risk are those whose occupations combine force and repetition of the same motion in the fingers and hand for long periods. Such workers include those in the meat and fish packing industries and workers using vibrating tools, like jackhammers or chain saws. Meat packers complained of pain and loss of hand function as long ago as the 1860's. Even today, the incidence of carpal tunnel syndrome in meat, poultry, and fish packing industries may be as high as 15%. Workers in these industries and those who assemble airplanes have the highest risk of CTS, according to one study. In addition, high risk for CTS has been reported in other assembly line workers (such as food and beverage processing), cake decorators, postal workers, dentists, and dental technicians, virtually any workers who use their hands and wrists repetitively.
Even though the increased number of people using computer keyboards has provoked much publicity about their risk for CTS, it is actually lower than those in occupations involving heavy labor. The force of the movement may, however, be a particular factor for CTS in typists. One study observed that typists with CTS struck the keys with greater force than those without the disorder. Some workers may not even be aware of the amount of force they exert while performing their jobs. For example, the fingers of typists whose speed is 60 words per minute exert up to 25 tons of pressure each day.
People who engage intensively in certain domestic occupations, including knitting, sewing and needlepoint, cooking, housework, carpentry, and extensive use of power tools, are also at risk. Many leisure activities in the home can contribute to the development of CTS, including computer games, sports, and card playing.
Many studies indicate that women have a significantly higher risk for carpal tunnel syndrome than men do. The explanation for this greater risk is unknown. The hand-intensive nature of housework and typing may contribute to a higher incidence in women. Hormonal changes, however, appear to play a major role as evidenced by an increased incidence in CTS symptoms while taking oral contraceptives or hormone replacement therapy and during pregnancy, the postpartum period, and menopause. In one study of pregnant women with CTS, the condition developed at any point during pregnancy; no single trimester posed a higher risk than others. New-onset CTS during pregnancy that is severe and persistent enough to require treatment is uncommon, however, and most cases either resolve spontaneously after delivery or improve with conservative treatment such as steroid injections or wrist supports. Breast feeding, which temporarily lowers natural steroid hormone levels, has been linked to flare-ups of inflammatory disorders such as CTS. Women are also at significantly higher risk for autoimmune disorders than men are; such disorders are highly linked to CTS .
Obesity is highly linked with carpal tunnel syndrome. CTS is also more common in those with square wrists (the thickness and width are about the same) than in those with the more common rectangular wrists, although other studies have failed to confirm this. There has been some suggestion that the size of the carpal tunnel may play a role in the disorder, but one study found no difference in size between women who had CTS and those who did not have it. Some researchers claim that poor upper back strength makes people more susceptible to injuries in the upper extremities, including carpal tunnel syndrome.
Cigarette smoking, poor nutrition, previous injuries, and stress can increase one's risk for carpal tunnel syndrome.
How Serious Is Carpal Tunnel Syndrome?
Carpal tunnel syndrome can range from a minor inconvenience to a disabling condition, depending on its cause and persistence and the individual characteristics of the patient. Many cases of CTS are mild, and some resolve on their own. Once a woman with pregancy-associated CTS gives birth, for instance, the swelling in her wrists and other symptoms almost always subside. Proper treatment of other medical conditions that cause CTS can often help reduce wrist swelling.
In severe untreated cases, however, the thenar muscles at the base of the thumb may whither and sensation may be permanently lost. CTS can become so crippling that people can no longer do their job or even perform simple tasks at home.
Carpal tunnel syndrome exacts a psychologic toll. Anyone who cannot use his or her hands is bound to be depressed and suffer from low self-esteem. A worker with CTS may be forced to give up his or her livelihood. An employee experiencing hand pain may try to ignore it and put more stress on the wrists, leading to poor work performance. Because the disease is not readily visible, coworkers and managers may harass CTS sufferers and accuse them of faking to get out of work.
At home, people may suffer from daily pain and loss of freedom. They cannot contribute actively to their families because they may not be able to drive a car or do ordinary tasks, such as picking up groceries. They may become still more depressed if they have to give up enjoyable sports and hobbies, golf or tennis or riding a bicycle.
CTS has had a severe impact on American businesses. Recent data suggests that five to 10 workers out of every 10,000 will miss work each year because of CTS. Such workers miss an average of 30 days each time, which is more than the work loss reported for back pain cases. Workers with CTS become easily fatigued, experience pain and discomfort, and may not perform up to par. In one study, nearly half of all employees diagnosed with CTS had changed jobs or were absent 30 months after the diagnosis. It is difficult to determine the exact cause of CTS, and employers are concerned about high worker's compensation costs due to CTS, which may or may not be due to working conditions. Needless to say, those receiving compensation are more likely to be absent from work longer than those not being paid, particularly if the employer is contesting the case. (Those not being compensated and so needing to stay at work, however, may be in pain and not working efficiently and may even be endangering themselves.) Although some companies are concerned that patients will falsify their symptoms in order to acquire workmen's compensation benefits, one study showed that workers whose employment made them eligible for benefits reported their disabilities just as accurately as those without the possibility for compensation. The medical costs and loss of productivity because of CTS has been estimated to average $29,000 per injured worker. Work-related injuries (including CTS) that involve joints and muscles cost the country about $20 billion every year.
How Can Carpal Tunnel Syndrome Be Prevented?
No single mode of prevention exists for carpal tunnel syndrome. If the underlying cause is a medical condition, controlling the problem can prevent CTS. Simple common sense may help minimize some risk factors predisposing to work-related CTS or other cumulative trauma disorders. A patient can learn how to adjust the work area, handle tools, or perform tasks in ways that put less stress on the hands and wrists. Exercise programs to strengthen the fingers, hands, wrists, forearms, shoulders, and neck may help prevent CTS. It should be stressed, however, that there has been no evidence that any of these methods can provide complete protection against CTS. Nevertheless, companies are now taking action to help prevent repetitive stress injuries. In a major survey, 84% reported that they were modifying equipment, tasks, and processes; 83% were analyzing their workstations and jobs, and 79% were buying new equipment.
Ergonomics is the study and control of posture, stresses, motions, and other physical forces on the human body engaged in work. Altering the way a person performs repetitive activities may help prevent inflammation in the hand and wrist from progressing into full-blown carpal tunnel syndrome. For example, replacing old tools with ergonomically designed new ones can be very helpful.
Rest Periods and Avoiding Repetition. Anyone who does repetitive tasks should begin with a short warm-up period, take frequent break periods, and avoid overexertion of the hand and finger muscles whenever possible. Employers should be urged to vary tasks and work content.
Good Posture. Good posture is extremely important in preventing carpal tunnel syndrome, particularly for typists and computer users. A keyboard operator should sit with the spine against the back of the chair with the shoulders relaxed, the elbows along the sides of the body, and wrists straight. The feet should be firmly on the floor or on a footrest. Typing materials should be at eye level so that the neck does not bend over the work. Keeping the neck flexible and head upright maintains circulation and nerve function to the arms and hands. Poorly designed office furniture is a major contributor to bad posture. Chairs should be adjustable for height, with a supportive backrest. Employers should be advised that the higher cost of a custom designed chair for a worker whose body does not fit a standard chair is still far less than the medical or absentee costs of an injured employee.
Techniques and Tools for Reducing Force. The force placed on the fingers, hands, and wrists by a repetitive task contributes importantly to CTS. To alleviate the effect of force on the wrist, tools and tasks should be designed so that the wrist position is the same as it would be if the arms dangled in a relaxed manner at the sides. No task should require the wrist to deviate from side to side or to remain flexed or highly extended for long periods.
Keyboard operators should adjust the tension of the keys so that depressing the keyboard does not cause fatigue. The hands and wrists should remain in a relaxed position to avoid excessive force on the keyboard. For computer users, replacing the mouse with a trackball device and the standard keyboard with a jointed-type are helpful substitutions. Wrist rests, which fit under most keyboards, can help keep the wrists and fingers in a comfortable position. One study documented significantly improved satisfaction and reduced hand pain in workers who used alternative geometry keyboards, particularly the Microsoft Natural Keyboard and to a lesser extent the Apple Adjustable Keyboard. These keyboards are designed to allow the user to adjust and modify hand positions as well as key tension.
Repetitive stress injuries have also been associated with the computer mouse. Some people recommend keeping the mouse as close to the keyboard and the computer users body as possible to reduce shoulder muscle movement. The mouse should be held lightly with the wrist and forearm relaxed. Some people also cut their mousepad in half to reduce movement.
The handles of such tools as screwdrivers, scrapers, paint brushes, and buffers should be designed so that the force of the worker's grip is distributed across the muscle between the base of the thumb and the little finger, not just in the center of the palm. People who need to hold any objects, such as a pencil, steering wheel, or tools, for long periods of time should grip them as loosely as possible.
In order to apply force appropriately, the ability to feel an object is extremely important. Tools with textured handles are helpful. Working at low temperatures, which reduces sensation in hands and fingers, should be avoided if possible.
Reducing Vibration. Tools and machines should be designed to minimize vibrations. Protective equipment, such as shock absorbers, can reduce vibrations. Bicyclists who ride frequently on rough roads should wear thick cycling gloves to lessen the shock transmitted to the hands and wrists.
Hand and wrist exercises may help reduce the risk of developing carpal tunnel syndrome. Isometric and stretching exercises can strengthen the muscles in the wrists and hands, as well as the neck and shoulders, improving blood flow to these areas. Performing the following simple exercises for four to five minutes every hour may be helpful.
Wrists. Make a loose right fist, palm up, and use the left hand to press gently down against the clenched hand. Resist the force with the closed right hand for five seconds, but be sure to keep the wrist straight. Next, turn the right fist palm down and press against the knuckles with the left hand for five seconds. Finally, turn the right palm so the thumb-side of the fist is up and press down again for five seconds. Repeat with the left hand.
Another easy wrist exercise requires first holding one hand straight up next to the shoulder with fingers together and palm facing outward. (The position looks like a shoulder-high salute); next, with the other hand, bend the hand being exercised backward with the fingers still held together and hold for five seconds; and third, spread the fingers and thumb open while the hand is still bent back and hold for five seconds. Repeat five times for each hand.
A third simple exercise is called wrist circles. First hold the second and third fingers up and close the others. Draw five clockwise circles in the air with the two fingertips. Draw five more counterclockwise circles. Repeat with the other hand.
Fingers and Hand. The first exercise is the finger bend and stretch. Clench the fingers of one hand into a fist tightly, and then release, fanning out the fingers. Do this five times. Repeat with the other hand.
To exercise the thumb, bend it against the palm beneath the little finger and hold for five seconds. Spread the fingers apart, palm up, and hold for five seconds. This should be repeated five to 10 times with each hand. Then, gently pull the thumb out and back and holding for five seconds, repeating five to 10 times with each hand.
Forearms. Excessive use of the hands can cause the forearm muscles to tighten, increasing pressure on tendons as they pass through the wrist. Stretching these muscles will reduce this tension. Place the hands together in front of the chest, fingers pointed upward in a prayer-like position. Keeping the palms flat together, raise the elbows to stretch the forearm muscles. Stretch for 10 seconds. Then gently shake the hands limp for a few seconds to loosen them. Repeat frequently when the hands or arms tire from activity.
Neck and Shoulders. Sit upright and place the right hand on top of the left shoulder. Hold that shoulder down and slowly tip the head down toward the right. Keep the face pointed forward, or even turned slightly toward the right. Hold this stretch gently for five seconds. Repeat on the other side.
A second exercise requires standing in a relaxed position with the arms at the side. Shrug the shoulders up, then squeeze the shoulders back, then stretch the shoulders down, and then press them forward. The entire exercise should take about seven seconds.
General Exercise. A regular exercise regimen using a combination of aerobic and resistance training techniques strengthens the muscles in the shoulders, arms, and back, helps reduce weight, and improves overall health and well-being. Some experts have reported that people who are physically fit, including athletes, joggers, and swimmers, have a lower risk for cumulative trauma disorders. People with any chronic medical condition or with risk factors for heart disease should check with their physicians about an appropriate regimen.
What Tests May Be Required to Diagnose Carpal Tunnel Syndrome?
The first step in diagnosing CTS is to determine whether an underlying medical condition is causing it. The next step is to evaluate the possible association between the disorder and the patient's job. Most likely, many cases of CTS are a combination of a medical problem exacerbated by repetitive stress factors at work.
Medical and Personal History
The patient should give the physician a detailed history of complaints, including any daily activities that require repetitive hand or wrist actions, abnormal postures, or other chronic situations that could affect the nerves in the neck, shoulders, and hands. The patient should report whether the symptoms especially appear at night or after particular tasks. The physician should also rule out other medical conditions, such as arthritis or diabetes, that may be precipitating CTS.
Experts emphasize the need to fully examine patients presenting symptoms of CTS. Relying only on CTS symptoms and personal or work histories may result in the failure to detect (and thus properly treat) underlying medical conditions that could be serious. For specifically finding signs of CTS, the doctor will perform simple maneuvers called provocative tests. In one test, the physician taps over the median nerve to produce a tingling or mild shock-sensation (called Tinel's sign). The patient may also be asked to try and reproduce CTS symptoms by using so-called wrist-flexion tests. In Phalen's test, the patient rests the elbows on a table and lets the wrists dangle with fingers pointing down and the backs of the hands pressed together (like backward praying). If symptoms develop within a minute, CTS is indicated. (If the test lasts for more than a minute even patients without CTS may develop symptoms.) The physician may also test for muscle weakness by pressing on the thumb as the patient holds it and the little finger together.
Some physicians use a diagram of a hand and wrist, which is usually divided into six regions. The patients are asked to indicate where their symptoms, including pain, numbness, or tingling, are by locating the affected areas on the diagram. The patients may also be asked to rate the severity of their symptoms.
If the doctor suspects that an underlying medical condition may be exacerbating the symptoms, laboratory tests will be performed. The doctor may take an x-ray, for example, to check for arthritis or fractured bones.
Electrodiagnostic tests that analyze the electric waveforms of nerves and muscles to detect median nerve compression in the carpal tunnel are the best methods for diagnosing CTS at this time. Nerve conduction studies and electromyographies are the electrodiagnostic tests most commonly performed. (It should be noted, however, that these tests do not predict carpal tunnel syndrome. Workers without symptoms who show abnormal results on these tests are no more likely to develop CTS symptoms than those with normal results and no symptoms.) Modifications and improvements of these tests are continually being made. To perform nerve conduction studies, surface electrodes are first fastened to the hand and wrist. Small electric shocks are then applied to the nerves in the fingers, wrist, and forearm to measure the speed of conduction of sensory and motor nerve fibers. To perform electromyography, a fine sterile, wire electrode is inserted briefly into a muscle and the electrical activity is displayed on a viewing screen. Electromyography can be quite painful, and some experts question, in fact, whether it adds any valuable diagnostic information. They suggest it be limited to unusual cases or when other tests indicate that the condition is aggressive and may increase the risk for rapid, significant injury.
Certain conditions, such as obesity and anxiety, can slow the speed of electrical conduction and skew the results. Women and the elderly normally have slower conduction times than younger adult men. Temperature also affects nerve conduction speed. Room temperature should be strictly controlled and physicians should take into consideration any climatic conditions that might affect outcome. Both tests are fairly accurate, however, and can detect 84% of people who have carpal tunnel syndrome, and eliminate 95% of cases that are not true carpal tunnel syndrome. They can also detect causes of symptoms that mimic CTS but should be attributed to other problems, such as pinched nerves in the neck or elbow or thoracic outlet syndrome. Ruling out other causes is extremely important in order to avoid unnecessary surgery for CTS. Physicians who perform these tests should be certified by the American Board of Electrodiagnostic Medicine, which uses rigorous standards in qualifying doctors.
Magnetic resonance imaging (MRI) has been found to be accurate in determining the severity of carpal tunnel syndrome. Investigators are adapting this technique to distinguish weak nerve signals from surrounding tissue and within a few years, MRI may be able to precisely diagnose CTS. It is too expensive, even now, for routine use, but it may be effective for detecting any internal injuries that might be causing the problem. MRI may also be valuable in selecting surgical candidates when electrodiagnostic tests produce unusual results or indicate more severe disease than expected. The use of ultrasound imaging is also showing promise in revealing abnormalities in the wrist indicative of CTS. X-rays of the wrist are not useful.
Some researchers reported that a computer-assisted device that measures pinch and grip strength and finger pressure was very promising for providing an accurate and consistent tool for diagnosing carpal tunnel syndrome.
What Are Nonsurgical Treatments for Carpal Tunnel Syndrome?
Conservative Therapy. It is critical to begin treating early phases of carpal tunnel syndrome before the damage progresses. If possible the patient should avoid activities at work or home that may aggravate the syndrome. Conservative treatment works best in men under 40 and least well in young women.
The affected hand and wrist should be rested for at least two weeks; this allows the swollen, inflamed tissues to shrink and relieves pressure on the median nerve. Ice may provide relief. Some patients have reported that alternating warm and cold soaks have been beneficial. If hot applications relieve pain, most likely the problem is not caused by CTS but by another condition producing similar symptoms.
Some people wear a wrist splint or brace at night or during sports to help keep the wrist from bending. The splint is used for several weeks or months depending on the severity of the problem. Except for anecdotal reports, no evidence exists that these supports actually help. Some experts believe that wrist supports may actually exacerbate the problem by reducing circulation and restricting movement so that the shoulder muscles tense up.
Physical Therapy. If symptoms subside, the patient may proceed with a supervised hand and wrist strengthening exercise program usually offered by physical or occupational therapists. One study found that most people with CTS felt improvement after two months of physical therapy that included exercises to improve balance and posture.
Ultrasound. Ultrasound treatment is a procedure that bombards the wrist with sound waves. In one study, ultrasound reduced symptoms, and relief lasted for at least six months. A more recent study, however, found it to be no better than placebo treatment, and it also raised the question of possible ultrasound damage to motor nerve conduction.
Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen, may help reduce swelling and pain. It should be noted that long-term use of these medications can cause gastrointestinal problems, even bleeding. If these painkillers are unsuccessful, the doctor may inject an anesthetic or a corticosteroid (such as cortisone) into the carpal tunnel to shrink the swollen tissues and relieve pressure on the nerve. To avoid attrition of the tendon, no more than three injections of cortisone should be given. It should be noted that the pain may increase for a day or two after the injection and skin color may change. Diuretics, such as trichlormethiazide, which reduce fluid in the body, may also be used. In one study, a short-term regimen of low doses of the oral corticosteroid prednisolone was more effective than either an NSAID (tenoxicam) or the diuretic trichlormethiazide. In fact, neither the NSAID nor the diuretic was any more effective than a placebo (a "sugar" pill). Oral corticosteroids can have serious side effects if used for long periods, however, and the study did not continue beyond one month, so long-term risks and benefits of this treatment for CTS are unknown. The drug naftidrofuryl (Praxilene) dilates bloods vessels, increases oxygen transport, and appears to have some capability for nerve regeneration. In Europe, it was used after surgery to treat the palm of the hand that had atrophied due to carpal tunnel syndrome. All patients who were treated in the study showed total or partial recovery. High doses of this drug can cause kidney problems. More work is needed on this interesting treatment.
In some, but not all, studies deficiencies of vitamin B6 (pyridoxine) have been associated with CTS. One study supported this association and, furthermore, reported that high levels of vitamin B6 were associated with fewer CTS symptoms. The same study also reported that high levels of vitamin C relative to low vitamin B6 levels were associated with a higher prevalence and greater frequency of symptoms. It should be noted that high doses of vitamin B6 can be toxic and cause nerve damage.
Many alternative therapies are offered to sufferers of carpal tunnel syndrome and other repetitive stress disorders. Most are harmless, but the benefits are unproved. Acupuncture has helped some people relieve pain. New techniques employing painless laser acupuncture may prove to be particularly effective. The National Institutes of Health issued a Consensus Statement on Acupuncture in 1997 which declared this ancient form of treatment useful as a supplement to standard treatment or even as part of a comprehensive management program of CTS. Chiropracty has been useful for some people whose condition is produced by pinched nerves. Some patients have reported possible benefit from using certain herbal oils, such as arnica oil. In one preliminary study, a regimen of 11 yoga postures designed to stretch, strengthen, and balance upper body joints proved superior to no treatment or the use of wrist splints in reducing pain, increasing grip strength, and relieving certain other signs and symptoms of CTS. There have been unproven claims for a number of herbal remedies, including creams containing arnica, vitamin B6, and choline (another B vitamin). People should approach nontraditional methods very cautiously and should check with their physician before trying any of them.
Research indicates that anxiety, depression, and even pain related to CTS can be ameliorated to some extent with cognitive behavior therapy. The focus of this therapeutic approach is to change negative thinking about ones ability to manage pain. Cognitive therapy is particularly helpful in defining and setting limits. Cognitive therapy may be expensive and not covered by insurance, although it is usually of short duration, typically six to 20 one-hour sessions, plus homework, which usually includes attempting a task that the patient has avoided because of negative thinking. Even if people cannot afford therapy, support groups for carpal tunnel syndrome and other sufferers of repetitive stress injuries can be very helpful in exchanging information and offering specific advice and solace. Stress management techniques can also be useful in dealing with the psychologic and emotional issues accompanying these injuries.
What Are the Surgical Procedures for Carpal Tunnel Syndrome?
This report discusses four different surgical procedures for carpal tunnel syndrome: open release; mini open release; endoscopy; and percutaneous balloon carpal tunnel-plasty. The decision for whether and when to have surgery to correct CTS is a troubling one for patients. In one long-term study most patients experienced CTS symptoms for only six to nine months, but 22% of the subjects had symptoms for eight or more years. There is no test that can determine whether symptoms will resolve or become worse in most people.
Candidates for Surgery
A number of experts believe that release surgery is performed too often and that CTS sufferers should pursue conservative treatment and physical therapy as aggressively as possible before choosing this more invasive option. Nevertheless, other experts argue that often the condition is progressive and will worsen over time without surgery, which generally brings good results. Waiting too long may also significantly reduce the benefits of surgery; one study indicated that surgery was most successful when it was performed within three years of the diagnosis of the disorder.
Electrodiagnostic tests for nerve conduction and magnetic resonance imaging scans are used to determine severity and who would most benefit from surgery. One study suggested that workers who had normal or near-normal nerve conduction results before surgery were least likely to benefit from surgery. Those with significantly slow nerve conduction and other abnormal results showed the most improvement after surgery. One study indicated that patients most likely to be satisfied with the surgery are those who had less preoperative muscle weakness and whose symptoms were worse at night.
Patients with CTS from nerve damage due to medical conditions, such as diabetes, rheumatoid arthritis, or hypothyroidism, appear to have the same outcome as those without such conditions and so such disorders should not preclude them from surgery.
It is generally recommended that if symptoms persist for four to six months and if muscles begin to atrophy in the base of the palm, the patient may require surgery. The procedure does not cure all patients, and because it permanently cuts the carpal ligament, some wrist strength is often lost.
Specific Release Surgeries
Open Release Surgery. Traditionally, surgery for CTS entails an open surgical procedure performed in an outpatient facility. A local anesthetic is injected either into the wrist and hand or higher up the arm. The surgeon makes a two-inch incision in the palm. In some cases the incision must be extended into the forearm. The surgeon the makes further incision in the muscles of the and until the carpal ligament is visible. The carpal ligament is then cut free from the underlying median nerve. The ligament is literally released and therefore the pressure on the median nerve is relieved.
Mini-Open Release . A variation known as a mini-open release technique uses an incision that is only about an inch and a half, and it can be performed in the doctor's office with only a local anesthetic. The operation takes only about 12 minutes. The results of one small study reported no infection, no injury to the median nerve, and no loss of finger mobility, or recurrence of CTS after a year. |
Endoscopy. Endoscopy for carpal tunnel syndrome is a less invasive procedure than standard open release. One or two 1/2-inch incisions are made in the wrist and palm, and one or two endoscopes, pencil-thin tubes, are inserted. A tiny camera and a knife are inserted through the lighted tubes. While observing the underside of the carpal ligament on a screen, the surgeon cuts the ligament to free the compressed median nerve. Patients do not end up with a surgical scar and can often return to work within half the time as in standard open surgery. In one study, 98% of patients experienced relief of numbness and weakness and in 90% pain was reduced. Only 12% of patients required more than two doses of pain relievers after the operation. Nearly 85% of patients who were not on workers compensation returned to work within a month. One 1998 analysis reported that success rates average about 96%, complication rates are 2.7%, and failure rates are 2.6%. As surgeons gain more experience with this procedure, studies are now reporting similar success and complications rates to standard open surgeries. In some studies, patients had better grip strength after endoscopy than after standard release, and, in many studies, patients reported less pain and returned to normal activities earlier than those who had the open release procedure. A recent review of the literature reports that overall, endoscopic release results in improved physical functioning and a faster return to work than does open release.
Complications with endoscopy, including tingling or loss of sensation in the fingers, increase with surgeons who are less experienced. Usually, such complications are temporary. In some patients pain and other CTS symptoms may still persist or recur following endoscopy severely enough to require follow-up open release procedures. Patients should not be shy about asking for the number of endoscopic procedures their surgeons have performed. Some experts believe that there may be a higher recurrence rate of CTS with endoscopy because the view of the hand is limited during this procedure and surgeons may not see complicating conditions that may require treatment. (In the open release procedure, the surgeon has a full view of the structures in the hand.) Long-term studies are needed to determine this.
Postsurgery Recovery. For some patients, release surgery relieves CTS symptoms of numbness and tingling immediately. In one study, grip and pinch strengths exceeded preoperative status within six weeks. Peak improvement may take a long time; in one study improvement took an average of almost 10 months. People who have the operation on both hands are completely incapacitated for about two weeks and must have someone to help them at home. Returning to strenuous work right after surgery may cause the symptoms to recur, and patients generally stay out of work for at least month and often much longer, depending upon the type of surgery and severity of the condition. To help rebuild wrist strength, physical therapy is very important. Hand exercises can help restore circulation, muscle strength, and joint flexibility in the hand and wrist. Wearing a splint to immobilize the wrist after surgery confers no benefits.
Complications and Long-Term Outcome. In spite of the success of carpal tunnel surgery, treatment failure and complication rates range in studies from 3% to 19%. Postsurgery complications may include nerve damage, infection, scarring, pain, and stiffness. The incision site may remain sore for months, and some patients experience some scar pain for years with open release. Certain people will always experience residual numbness in the fingertips. Reasons for failure include incomplete release of the ligament, extensive scarring, and recurrence of the disorder due to underlying medical disorders. If scarring or medical conditions are the cause of failure, symptoms generally return in one to one and half years after surgery.
At highest risk for surgical failure or a poorer outcome are the elderly, those with very severe preoperative symptoms, and people involved with heavy manual labor, particularly those working with vibrating tools. One five-year study found that people who had been working at heavy labor stayed out longer and appeared to have slower improvement, but responses after five years did not differ among occupational groups. In some studies, however, only slightly more than half the people who used vibrating hand-held tools were symptom-free three years after their operations. Because between 10% and a third of patients lose some wrist strength with both endoscopy and open release, patients who have jobs requiring high amounts of force to the hand and wrist may not be able to perform them after surgery. Such workers may also have problems in other parts of the upper body, including elbows and shoulders, that are not resolved with surgery and can persist. Studies indicate the between 10% and 15% of patients change jobs after the operation.
Percutaneous Balloon Carpal Tunnel-Plasty
Percutaneous balloon carpal tunnel-plasty is a technique that alleviates CTS without cutting the carpal ligament. Through a 1/4-inch incision in the base of the palm, the doctor inserts a balloon through a catheter under the ligament and inflates the balloon with saline solution to stretch the ligament and free the nerve. In one small study, all of the patients reported relief of symptoms with no postoperative complications. This experimental technique is not yet widely available and some experts believe it is unlikely to be.
Surgical Intervention for Recurring Carpal Tunnel Syndrome
If pain and symptoms recur the release procedure may be repeated. In some severe cases when scarring is extensive, surgeons may choose to sever the nerves that are responsible for the pain using a procedure called external or internal neurolysis. One study indicated that neurolysis should be considered if no recovery is indicated three months after surgery, after which improvement is unlikely.
In another procedure for recurrent carpal tunnel, physicians may take muscle flaps or even fatty tissue from other parts of the body and implant them at the site of the nerve injury. Such flaps enhance the development of new blood vessels, provide padding, and possibly serve as a bed for nerve regrowth. These implants may be used with or without nerve dissection. Another procedure called vein wrapping uses grafts taken from veins helps protect the scarred nerves.
Board of Editors
- Harvey Simon, MD, Editor-in-Chief, Massachusetts Institute of Technology; Physician, Massachusetts General Hospital
- Stephen A. Cannistra, MD, Oncology, Associate Professor of Medicine, Harvard Medical School; Director, Gynecologic Medical Oncology, Beth Israel Deaconess Medical Center
- Masha J. Etkin, MD, PhD, Gynecology, Harvard Medical School; Physician, Massachusetts General Hospital
- John E. Godine, MD, PhD, Metabolism, Harvard Medical School; Associate Physician, Massachusetts General Hospital
- Daniel Heller, MD, Pediatrics, Harvard Medical School; Associate Pediatrician, Massachusetts General Hospital; Active Staff, Children's Hospital
- Paul C. Shellito, MD, Surgery, Harvard Medical School; Associate Visiting Surgeon, Massachusetts General Hospital
- Theodore A. Stern, MD, Psychiatry, Harvard Medical School; Psychiatrist and Chief, Psychiatric Consultation Service, Massachusetts General Hospital
- Carol Peckham, Editorial Director
- Cynthia Chevins, Publisher
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