Carpal Tunnel Syndrome
What is Carpal Tunnel Syndrome?
Nine tendons needed to bend the fingers stretch from the forearm into the
hand through a passageway in the wrist called the carpal tunnel. Carpal
bones form three walls of the tunnel and a strong, broad transverse carpal
ligament bridges the top. The median nerve, which supplies feeling to the
thumb, index, and ring fingers, and the tendons that flex the fingers, also
passes through this tunnel. Carpal tunnel syndrome (CTS) occurs when the
protective lining of the tendons within the carpal tunnel swells, or when
the ligament that forms the roof becomes thicker and broader. Eventually,
the swollen tendons and ligaments press on the median nerve, a process
called nerve entrapment, and can result in numbness, tingling, and pain in
the wrist, hand, and fingers.
Carpal tunnel syndrome is categorized as a
cumulative trauma disorder; these are problems generally associated with
repetitive and forceful use of the hands that damage muscles and bones of
the upper extremities. Other terms that are used to define and categorize
carpal tunnel syndrome are repetitive strain injuries (RSI), overuse
syndromes, chronic upper limb pain syndrome, or repetitive motion disorders.
What causes Carpal Tunnel Syndrome?
Although most often associated with occupations or tasks requiring
high-force, high-repetitive hand motions, the injury can be provoked by
other conditions. Some experts believe that incorrect posture may play a
large role in the development of CTS, particularly 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. Bone dislocations and fractures can
narrow the carpal tunnel, thereby exerting pressure on the median nerve.
Fluid retention during pregnancy or due to the hormonal changes associated
with menopause can cause swelling and symptoms of carpal tunnel syndrome.
Certain other medical conditions, such as rheumatoid arthritis, diabetes, and thyroid hormone deficiency, can also cause inflammation in the carpal tunnel and median nerve entrapment. In many patients with CTS, an underlying cause for the disorder cannot be discovered.
What are the symptoms?
Just as stepping on a hose slows the flow of water through a garden hose, so
the compression of the median nerve fibers by the swollen tendons and
thickened ligament slows down the transmission of nerve signals through the
carpal tunnel and results in pain, numbness, and tingling in the wrist,
hand, and fingers.
Symptoms 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 fingers. Patients may also notice a sense of
weakness with 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 with the use of the hand but with the
hand at rest or at night after going to bed. In some cases, work-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.
Accompanying Disorders
About 25% of patients with work-related carpal
tunnel syndrome also have evidence of other cumulative trauma disorders.
Even when they occur alone, many of these repetitive stress disorders may
have symptoms similar to 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, as well as on other nerves in the
arm and hand. The branch of the median nerve that runs through the palm of
the hand can be damaged 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 in the forearm.
Like the median nerve, the ulnar nerve, which controls the ring and little
fingers, can also 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 appear as a
separate disorder or with carpal tunnel syndrome. 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.
Pinched Nerves or Blood Vessels. Pinched nerves in the neck may 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. The condition is diagnosed by a
physician who detects diminished blood flow in the arm, as the patient
raises the affected hand and turns his or her head towards the opposite
side.
Other Diseases. 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. These conditions should be ruled out by the physician.
Who gets Carpal Tunnel Syndrome?
Occupational Risks. In 1992, according to the Bureau of Labor statistics, an
estimated one million out of 2.3 million work-related injuries were
associated with cumulative trauma. This may be a low estimate of the true
number of cases, since, in 1988 2.8 million people reported to their doctors
symptoms that they believed were those of carpal tunnel syndrome. The wide
variation in severity and the difficulty in diagnosis makes it hard to
pinpoint specific figures. It is certainly true, however that the incidence
of cumulative trauma disorder has increased dramatically in recent years,
probably due to automation and the widespread use of the computer.
Researchers have defined six key risk factors for the development of
work-related cumulative trauma disorders, most of which also apply to the
development of CTS: (1) repetition, (2) high force, (3) awkward joint
posture, (4) direct pressure, (5) vibration, and (6) prolonged constrained
posture. At highest risk are workers whose tasks require repeating the same
motion in the fingers and hand for long periods. 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.
Meat packers complained of pain and loss of hand function as long ago as the
1860Ős. Even today, the incidence of CTS in the meat packing industry may be
as high as 15%. In addition to butchers and meat packers, CTS has been
reported in assembly line workers, cake decorators, postal workers,
jackhammer operators, file clerks, assembly workers, virtually any group of
workers who uses their hands and wrists repetitively. The use of the
computer has had a great impact on the increased incidence of this problem,
with people at risk including reporters, editors, data entry clerks, graphic
designers, programmers, and anyone using the computer heavily.
Activities in the home can also contribute to the development of CTS,
including many hobbies and household tasks. Knitting, sewing and
needlepoint, cooking and housework, playing computer games, sports, card
playing, carpentry, and extensive use of power tools are among the many
activities that may contribute to CTS.
Gender and Age. Women suffer CTS three times as often as do men. The
explanation for this is unknown, but an increased incidence while taking
oral contraceptives and during pregnancy and menopause seems to indicate
that hormonal changes may make women more susceptible. The hand-intensive
nature of housework and typing may also contribute to a higher incidence in
women. Older people also are more likely than younger ones to complain of
CTS, possibly because nerve velocity slows down as people age.
Physical Characteristics. In a recent study, obese workers were 3.5 to 4.1
times more likely to have abnormal median nerve conduction than slender
people. Some studies have also suggested that CTS is 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 finding. Some researchers also claim that poor upper
back strength makes people more susceptible to injuries in the upper
extremities, including CTS.
Medical Conditions. Medical conditions that cause swelling in the wrist,
such as arthritis, thyroid disease, diabetes, and acromegaly may increase
susceptibility to CTS. In one study, 15% to 25% of people with diabetes had
carpal tunnel syndrome. In addition, cigarette smoking, poor nutrition,
previous injuries, and stress can increase one's risk.
Prevention
No single mode of prevention exists for carpal tunnel syndrome. It is
important, however, to use common sense and ergonomic controls to help
minimize 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. If the underlying cause
is a medical condition, controlling the problem can prevent CTS.
Ergonomic Controls. 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.
Repetition and Rest. 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
rotate the tasks of their employees and vary the work content so that
workers are given a variety of tasks.
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 foot rest. 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.
Force. The force placed on the fingers, hands, and wrists by a task may
contribute importantly to CTS, particularly when the task is repeated often.
To alleviate the effect of force on the wrist, tools and tasks should be
designed so that the wrist position is maintained 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 new jointed-type are helpful substitutions. Wrist rests, which fit
under most keyboards, can help keep the wrists and fingers in a comfortable
position.
Undue force on the palm occurs with the use of tools such as screwdrivers,
scrapers, paint brushes, and buffers. The handles of such tools 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.
In order to apply force appropriately, the ability to feel an object is
extremely important. Tools with textured handles are helpful. Working at low
temperature, which reduces sensation in hands and fingers, should be avoided
if possible.
Vibration. Tools and machines should be designed to minimize vibrations.
Protective equipment can reduce vibrations. Bicyclists who ride on rough
roads should wear thick cycling gloves to lessen the shock transmitted to
the hands and wrists.
Exercise. Hand and wrist exercises may help reduce the risk of developing
CTS. 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. Any exercise program should be undertaken cautiously, however,
and a physician consulted to be sure it is appropriate for the patient's
condition. If a patient experiences any pain or discomfort, he or she should
discontinue the exercise and check with the physician. The old adage, No
pain-no gain, does not apply in the case of CTS. 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 this series of exercises five times for each 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, bend the hand 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, 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. In
addition, one can stretch the thumb by gently pulling it 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 away to 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, 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.
Tests for CTS
Medical and Personal History. Discomfort or fatigue in the fingers, hands,
wrists, or arms may be caused by simple physical exertion without injury or
may signal the onset of carpal tunnel syndrome. Because carpal tunnel
syndrome often affects a person's work and may also involve worker's
compensation benefits, it is very important to evaluate the possible
association between the disorder and the patient's job. The patient should'
give the physician a detailed history of complaints, including daily work
activities and whether the symptoms appear especially at night or after
tasks. The physician should rule out other medical conditions, such as
arthritis or diabetes, that may be precipitating CTS.
Physical Examination. During a physical examination, the doctor will perform
simple maneuvers. If carpal tunnel syndrome is present, tapping over the
median nerve may produce a tingling or mild shock-sensation. The patient
will also be asked to try and reproduce the symptoms by holding the hands
together in front of the chest in a prayer position with the wrists bent out
for one minute. If these tests are positive, then the patient has the
physical signs as well as the symptoms of CTS.
Laboratory Tests. 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. The treating physician may arrange for
electrodiagnostic tests to confirm the diagnosis of carpal tunnel syndrome,
to determine the severity of the condition, and to rule out other causes.
There are two common types of electrodiagnostic tests: nerve conduction
studies and electromyographies. The tests are performed by specially trained
physicians who analyze the electric wave forms of nerves and muscles to
detect median nerve compression in the carpal tunnel. To perform nerve
conduction studies, surface electrodes are fastened to the hand and wrist
and small electric shocks are 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. Certain conditions, such as obesity, cold, and anxiety, can
slow the speed of conduction and skew the results. Women and the elderly
normally have slower conduction times than adult men. 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 which
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. Costs for these
tests are between $300 and $600. Physicians who are best qualified to
perform the test are those certified by the American Board of
Electrodiagnostic Medicine, which uses rigorous standards in qualifying
doctors.
How is CTS treated?
Early Treatment.
Conservative Therapy. It is critical to begin treating early phases of carpal tunnel syndrome before
the damage progresses. 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. A wrist
splint or brace may be worn 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
anecdotes of improvement, 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. Ice can be applied to 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 an inflammation not caused by CTS but by
another condition producing similar symptoms. The patient should reduce any risk factors at work
or home that may aggravate the syndrome. Conservative treatment works best in men under 40 but
least well in young women.
Drug Treatment. Anti-inflammatory agents, such as ibuprofen, may reduce swelling within the
carpal tunnel. If conservative treatment is unsuccessful, the doctor may inject an anesthetic or a
corticosteroid 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.
Physical Therapy. If symptoms subside, the patient may proceed with a supervised hand and wrist
strengthening exercise program usually offered by a 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.
Laser Light Therapy. One recent study found that automobile workers with CTS who were treated
with a process known as cold laser light had greater improvement in grip strength and range of
wrist movement than those treated with physical therapy. The process uses low-energy laser light
that penetrates, but does not cut, the skin and stimulates cells activity in the injured areas.
Release Surgical Procedures. 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 requires permanently cutting the carpal ligament, it often results in some loss
of wrist strength. Although carpal tunnel surgery is one of the most common procedures in the
U.S., no studies have been done to determine the long-term outcome for patients after they return to
work. A number of experts believe that this surgery is performed too often and that CTS sufferers
should pursue conservative treatment and physical therapy as aggressively as possible before
deciding to undergo surgery. Nevertheless, surgery may be necessary in certain cases, and it can be
very beneficial.
Open 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 and cuts the carpal ligament free from the
underlying median nerve. This surgery is called a "release", because cutting the ligament relieves
the pressure on the median nerve. Carpal tunnel release is the most commonly performed hand
surgery with more than 100,000 procedures each year. Open surgery effectively relieves symptoms
in 85% to 90% of patients, who can usually return to work within two months. The risk of
complications is less than one percent.
Endoscopy. In the last five years, a surgical procedure has emerged which uses an
endoscope, a
pencil-thin lighted tube. One or two 1/2-inch incisions are made in the wrist and palm, and one or
two endoscopes are inserted. A tiny camera and a knife are inserted through the lighted tube. While
observing the under surface 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 return to work
within a month, about half the time as in standard open surgery.
Endoscopy, however, is more
expensive than open surgery by about $500 and studies to date have not found it to be any more
effective than standard open release surgery. This is a relatively new procedure and complications,
including tingling or permanent loss of sensation in the fingers, increase with surgeons who are less
experienced.
Post surgery. For some patients, release surgery relieves CTS symptoms of numbness and tingling
immediately, but the incision site may remain sore for as long as three months. Returning to
strenuous work right after surgery may cause the symptoms to recur, and patients generally stay out
of work for at least month, depending upon the type of surgery and severity of the condition.
People who have the operation on both hands are completely incapacitated for about two weeks and
must have someone to help them at home. In one major study, people were out of work an average
of 4 months and 8% were out for more than a year. In this study, 67% returned to the same job and
15% to a different one.
With both types of surgery, nearly 25% of patients lose some wrist strength and may not be able to
perform jobs that require high amounts of force to the wrist. People involved with heavy manual
labor, particularly those working with vibrating tools, have a poorer outcome than others. In some
studies only slightly more than half the people who used vibrating hand-held tools were
symptom-free three years after their operations. Still, surgery can be beneficial in many cases. Older
patients or those with a severe case of CTS may still experience symptoms weeks or even months
after surgery. Post surgery complications may include nerve damage, infection, scarring, pain, and
stiffness.
To help rebuild wrist strength, physical therapy is very important. Hand exercises can help rebuild
circulation, muscle strength, and joint flexibility in the hand and wrist.
Percutaneous Balloon Carpal Tunnel Plasty. Percutaneous balloon carpal
tunnel-plasty is a
new technique still under investigation, which 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. Most of them were back to work within two weeks. This experimental technique,
which costs about $1,500, is not yet widely available.
Alternative Therapies. 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. Chiropracty has been useful for some people whose condition is produced by pinched nerves. A few years ago, many people hoped that vitamin B6 would be successful in alleviating symptoms, but it is no longer considered effective, and high amounts can cause nerve damage. Some patients have reported possible benefit from using certain herbal oils, such as arnica oil, but people should approach nontraditional methods very cautiously and should check with their physician before trying any.
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