Carpal tunnel syndrome occurs when the median nerve, which runs from the
forearm into the palm of the hand, becomes pressed or squeezed at the wrist.
The median nerve controls sensations to the palm side of the thumb , as well as
impulses to some small muscles in the hand that allow the index finger and
thumb to move. The carpal tunnel – a narrow, rigid passageway of ligament and
bones at the base of the hand – 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.
What are the symptoms of carpal tunnel syndrome?
Symptoms usually start gradually, with frequent burning, tingling, or
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.
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. Other disorders such as bursitis and tendonitis have
been associated with repeated motions performed in the course of normal work or
other activities.. Writer’s cramp may also be brought on by repetitive
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.
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,
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.
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.
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. Corticosteroids 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
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
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.
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 inch 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. Single portal endoscopic
surgery for carpal tunnel syndrome is also available and can result in less
post-operative pain and a minimal scar. It generally allows individuals
to resume some normal activities in a short period of time.
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.
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.