You're working
at your desk, trying to ignore the tingling or numbness
you've had for months in your hand and wrist. Suddenly,
a sharp, piercing pain shoots through the wrist
and up your arm. Just a passing cramp? More likely
you have carpal tunnel syndrome, a painful progressive
condition caused by compression of a key nerve in
the wrist.
What is carpal
tunnel syndrome?
Carpal tunnel syndrome
occurs when the median nerve, which runs from the
forearm into the hand, becomes pressed or squeezed
at the wrist. The median nerve controls sensations
to the palm side of the thumb and fingers (although
not the little finger), as well as impulses to some
small muscles in the hand that allow the fingers
and thumb to move. The carpal tunnel - a narrow,
rigid passageway of ligament and bones at the base
of the hand ¾ houses the median nerve and tendons.
Sometimes, thickening from irritated tendons or
other swelling narrows the tunnel and causes the
median nerve to be compressed. The result may be
pain, weakness, or numbness in the hand and wrist,
radiating up the arm. Although painful sensations
may indicate other conditions, carpal tunnel syndrome
is the most common and widely known of the entrapment
neuropathies in which the body's peripheral nerves
are compressed or traumatized.
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What are the
symptoms of carpal tunnel syndrome?
Symptoms usually
start gradually, with frequent burning, tingling,
or itching numbness in the palm of the hand and
the fingers, especially the thumb and the index
and middle fingers. Some carpal tunnel sufferers
say their fingers feel useless and swollen, even
though little or no swelling is apparent. The symptoms
often first appear in one or both hands during the
night, since many people sleep with flexed wrists.
A person with carpal tunnel syndrome may wake up
feeling the need to "shake out" the hand
or wrist. As symptoms worsen, people might feel
tingling during the day. Decreased grip strength
may make it difficult to form a fist, grasp small
objects, or perform other manual tasks. In chronic
and/or untreated cases, the muscles at the base
of the thumb may waste away. Some people are unable
to tell between hot and cold by touch.
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What are the
causes of carpal tunnel syndrome?
Carpal tunnel syndrome
is often the result of a combination of factors
that increase pressure on the median nerve and tendons
in the carpal tunnel, rather than a problem with
the nerve itself. Most likely the disorder is due
to a congenital predisposition - the carpal tunnel
is simply smaller in some people than in others.
Other contributing factors include trauma or injury
to the wrist that cause swelling, such as sprain
or fracture; overactivity of the pituitary gland;
hypothyroidism; rheumatoid arthritis; mechanical
problems in the wrist joint; work stress; repeated
use of vibrating hand tools; fluid retention during
pregnancy or menopause; or the development of a
cyst or tumor in the canal. In some cases no cause
can be identified.
There is little clinical
data to prove whether repetitive and forceful movements
of the hand and wrist during work or leisure activities
can cause carpal tunnel syndrome. Repeated motions
performed in the course of normal work or other
daily activities can result in repetitive motion
disorders such as bursitis and tendonitis. Writer's
cramp - a condition in which a lack of fine motor
skill coordination and ache and pressure in the
fingers, wrist, or forearm is brought on by repetitive
activity - is not a symptom of carpal tunnel syndrome.
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Who is at risk
of developing carpal tunnel syndrome?
Women are three times
more likely than men to develop carpal tunnel syndrome,
perhaps because the carpal tunnel itself may be
smaller in women than in men. The dominant hand
is usually affected first and produces the most
severe pain. Persons with diabetes or other metabolic
disorders that directly affect the body's nerves
and make them more susceptible to compression are
also at high risk. Carpal tunnel syndrome usually
occurs only in adults.
The risk of developing
carpal tunnel syndrome is not confined to people
in a single industry or job, but is especially common
in those performing assembly line work - manufacturing,
sewing, finishing, cleaning, and meat, poultry,
or fish packing. In fact, carpal tunnel syndrome
is three times more common among assemblers than
among data-entry personnel. A 2001 study by the
Mayo Clinic found heavy computer use (up to 7 hours
a day) did not increase a person's risk of developing
carpal tunnel syndrome.
During 1998, an estimated
three of every 10,000 workers lost time from work
because of carpal tunnel syndrome. Half of these
workers missed more than 10 days of work. The average
lifetime cost of carpal tunnel syndrome, including
medical bills and lost time from work, is estimated
to be about $30,000 for each injured worker.
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How is carpal
tunnel syndrome diagnosed?
Early diagnosis and
treatment are important to avoid permanent damage
to the median nerve. A physical examination of the
hands, arms, shoulders, and neck can help determine
if the patient's complaints are related to daily
activities or to an underlying disorder, and can
rule out other painful conditions that mimic carpal
tunnel syndrome. The wrist is examined for tenderness,
swelling, warmth, and discoloration. Each finger
should be tested for sensation, and the muscles
at the base of the hand should be examined for strength
and signs of atrophy. Routine laboratory tests and
X-rays can reveal diabetes, arthritis, and fractures.
Physicians can use
specific tests to try to produce the symptoms of
carpal tunnel syndrome. In the Tinel test, the doctor
taps on or presses on the median nerve in the patient's
wrist. The test is positive when tingling in the
fingers or a resultant shock-like sensation occurs.
The Phalen, or wrist-flexion, test involves having
the patient hold his or her forearms upright by
pointing the fingers down and pressing the backs
of the hands together. The presence of carpal tunnel
syndrome is suggested if one or more symptoms, such
as tingling or increasing numbness, is felt in the
fingers within 1 minute. Doctors may also ask patients
to try to make a movement that brings on symptoms.
Often it is necessary
to confirm the diagnosis by use of electrodiagnostic
tests. In a nerve conduction study, electrodes are
placed on the hand and wrist. Small electric shocks
are applied and the speed with which nerves transmit
impulses is measured. In electromyography, a fine
needle is inserted into a muscle; electrical activity
viewed on a screen can determine the severity of
damage to the median nerve. Ultrasound imaging can
show impaired movement of the median nerve. Magnetic
resonance imaging (MRI) can show the anatomy of
the wrist but to date has not been especially useful
in diagnosing carpal tunnel syndrome.
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How is
carpal tunnel syndrome treated?
Treatments for carpal
tunnel syndrome should begin as early as possible,
under a doctor's direction. Underlying causes such
as diabetes or arthritis should be treated first.
Initial treatment generally involves resting the
affected hand and wrist for at least 2 weeks, avoiding
activities that may worsen symptoms, and immobilizing
the wrist in a splint to avoid further damage from
twisting or bending. If there is inflammation, applying
cool packs can help reduce swelling.
Non-surgical treatments
Drugs
- In special circumstances, various drugs can
ease the pain and swelling associated with carpal
tunnel syndrome. Nonsteroidal anti-inflammatory
drugs, such as aspirin, ibuprofen, and other nonprescription
pain relievers, may ease symptoms that have been
present for a short time or have been caused by
strenuous activity. Orally administered diuretics
("water pills") can decrease swelling. Corticosteroids
(such as prednisone) or the drug lidocaine can
be injected directly into the wrist or taken by
mouth (in the case of prednisone) to relieve pressure
on the median nerve and provide immediate, temporary
relief to persons with mild or intermittent symptoms.
(Caution: persons with diabetes and those who
may be predisposed to diabetes should note that
prolonged use of corticosteroids can make it difficult
to regulate insulin levels. Corticosterioids should
not be taken without a doctor's prescription.)
Additionally, some studies show that vitamin B6
(pyridoxine) supplements may ease the symptoms
of carpal tunnel syndrome.
Exercise
- Stretching and strengthening exercises can be
helpful in people whose symptoms have abated.
These exercises may be supervised by a physical
therapist, who is trained to use exercises to
treat physical impairments, or an occupational
therapist, who is trained in evaluating people
with physical impairments and helping them build
skills to improve their health and well-being.
Alternative
therapies - Acupuncture and chiropractic
care have benefited some patients but their effectiveness
remains unproved. An exception is yoga, which
has been shown to reduce pain and improve grip
strength among patients with carpal tunnel syndrome.
Surgery
Carpal tunnel release
is one of the most common surgical procedures
in the United States. Generally recommended if
symptoms last for 6 months, surgery involves severing
the band of tissue around the wrist to reduce
pressure on the median nerve. Surgery is done
under local anesthesia and does not require an
overnight hospital stay. Many patients require
surgery on both hands. The following are types
of carpal tunnel release surgery:
Open
release surgery, the traditional
procedure used to correct carpal tunnel syndrome,
consists of making an incision up to 2 inches
in the wrist and then cutting the carpal ligament
to enlarge the carpal tunnel. The procedure is
generally done under local anesthesia on an outpatient
basis, unless there are unusual medical considerations.
Endoscopic
surgery may allow faster functional
recovery and less postoperative discomfort than
traditional open release surgery. The surgeon
makes two incisions (about ½" each) in the
wrist and palm, inserts a camera attached to a
tube, observes the tissue on a screen, and cuts
the carpal ligament (the tissue that holds joints
together). This two-portal endoscopic surgery,
generally performed under local anesthesia, is
effective and minimizes scarring and scar tenderness,
if any. One-portal endoscopic surgery for carpal
tunnel syndrome is also available.
Although symptoms
may be relieved immediately after surgery, full
recovery from carpal tunnel surgery can take months.
Some patients may have infection, nerve damage,
stiffness, and pain at the scar. Occasionally the
wrist loses strength because the carpal ligament
is cut. Patients should undergo physical therapy
after surgery to restore wrist strength. Some patients
may need to adjust job duties or even change jobs
after recovery from surgery.
Recurrence of carpal
tunnel syndrome following treatment is rare. The
majority of patients recover completely.
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How can carpal
tunnel syndrome be prevented?
At the workplace,
workers can do on-the-job conditioning, perform
stretching exercises, take frequent rest breaks,
wear splints to keep wrists straight, and use correct
posture and wrist position. Wearing fingerless gloves
can help keep hands warm and flexible. Workstations,
tools and tool handles, and tasks can be redesigned
to enable the worker's wrist to maintain a natural
position during work. Jobs can be rotated among
workers. Employers can develop programs in ergonomics,
the process of adapting workplace conditions and
job demands to the capabilities of workers. However,
research has not conclusively shown that these workplace
changes prevent the occurrence of carpal tunnel
syndrome.
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What research
is being done?
The National Institute
of Neurological Disorders and Stroke (NINDS), a
part of the National Institutes of Health, is the
federal government's leading supporter of biomedical
research on neuropathy, including carpal tunnel
syndrome. Scientists are studying the chronology
of events that occur with carpal tunnel syndrome
in order to better understand, treat, and prevent
this ailment. By determining distinct biomechanical
factors related to pain, such as specific joint
angles, motions, force, and progression over time,
researchers are finding new ways to limit or prevent
carpal tunnel syndrome in the workplace and decrease
other costly and disabling occupational illnesses.
Percutaneous
balloon carpal tunnel-plasty is an
experimental technique that can ease carpal tunnel
pain without cutting the carpal ligament. In this
procedure, a ¼-inch cut is made at the base of the
palm. The doctor then inserts a balloon through
a catheter under the carpal ligament and inflates
the balloon to stretch the ligament and free the
nerve. Patients in one small study of pertucaneous
balloon carpal tunnel-plasty reported relief of
symptoms with no postoperative complications; most
of them were back to work within 2 two weeks. This
experimental technique is not yet widely available.
Randomized clinical
trials are being designed to evaluate the effectiveness
of educational interventions in reducing the incidence
of carpal tunnel syndrome and upper extremity cumulative
trauma disorders. Data to be collected from an NINDS-sponsored
clinical study of carpal tunnel syndrome among construction
apprentices will provide a better understanding
of the specific work factors associated with the
disorder, furnish pilot data for planning future
projects to study its natural history, and assist
in developing strategies to prevent its occurrence
among construction and other workers. Other research
will discern differences between the relatively
new carpal compression test (in which the examiner
applies moderate pressure with both thumbs directly
on the carpal tunnel and underlying median nerve,
at the transverse carpal ligament) and the pressure
provocative test (in which a cuff placed at the
anterior of the carpal tunnel is inflated, followed
by direct pressure on the median nerve) in predicting
carpal tunnel syndrome. Scientists are also investigating
the use of alternative therapies, such as acupuncture,
to prevent and treat this disorder.
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