Carpal tunnel syndrome

Overview

Carpal tunnel syndrome is one of the most common hand conditions. It is caused by pressure on the median nerve in the carpal tunnel. The carpal tunnel is a narrow passageway in the wrist. It is on the palm side of the hand.

When the median nerve becomes compressed in the carpal tunnel, symptoms can include numbness, tingling and weakness in the fingers and hand.

Wrist structure, health conditions and repeated hand motions may play a part in carpal tunnel syndrome.

Proper treatment often lessens the tingling and numbness and restores hand function.

Symptoms

Symptoms of carpal tunnel syndrome tend to start slowly and include:

• Tingling and numbness. Tingling and numbness may occur in the fingers or hand and come and go. Most of the time, the thumb, index, middle and ring fingers are affected, but not the little finger. You might have a feeling like an electric shock in these fingers. These symptoms often happen while holding a steering wheel, phone or book, or they may wake you from sleep.

  The feeling also can travel from the wrist up the arm.

  Many people "shake out" their hands to try to lessen their symptoms. The numb feeling may become constant over time.

• Weakness. People with carpal tunnel syndrome may have weakness in the hand and drop objects. This may be due to numbness or to a lack of strength in the thumb's pinching muscles, which the median nerve also controls.

When to see a doctor

See a healthcare professional if you have symptoms of carpal tunnel syndrome that get in the way of your usual activities and sleep patterns. Lasting nerve and muscle damage can occur without treatment.

Causes

Carpal tunnel syndrome is caused by pressure on the median nerve.

The median nerve runs from the forearm through a passageway in the wrist to the hand. The passageway is known as the carpal tunnel. The median nerve provides feeling to the palm side of the thumb and all the fingers except the little finger. This nerve also provides signals to move the muscles around the base of the thumb. This movement is known as motor function.

Anything that squeezes or irritates the median nerve in the carpal tunnel space may lead to carpal tunnel syndrome. A broken wrist can narrow the carpal tunnel and irritate the nerve. Rheumatoid arthritis or other diseases can cause swelling that puts pressure on the nerve.

Many times, there is no single cause of carpal tunnel syndrome. Or the cause may not be known. It may be that a mixture of risk factors plays a part in the condition.

Risk factors

Many factors have been linked with carpal tunnel syndrome. Although they may not cause carpal tunnel syndrome directly, they may raise the risk of irritation or damage to the median nerve. These include:

• Physical factors. A broken or dislocated wrist can change the space within the carpal tunnel. So can arthritis-related changes to the small bones in the wrist. These changes can put pressure on the median nerve.

  People who have smaller carpal tunnels may be more likely to have carpal tunnel syndrome.

• Sex assigned at birth. Carpal tunnel syndrome is more common in women. This may be because the carpal tunnel area tends to be smaller in women than in men. Or it may be due to the effect of hormones on the lining of the tendons in the carpal tunnel.
• Nerve-damaging conditions. Some chronic illnesses, such as diabetes, increase the risk of nerve damage, including damage to the median nerve.
• Inflammatory conditions. Rheumatoid arthritis, gout and other inflammatory conditions can cause swelling in the tendons in the wrist. This can put pressure on the median nerve.
• Medicines. Some studies have shown a link between carpal tunnel syndrome and anastrozole (Arimidex), a medicine used to treat breast cancer.
• Obesity. Having obesity is a risk factor for carpal tunnel syndrome.
• Fluid retention. When the body holds on to extra fluid, that fluid may increase the pressure within the carpal tunnel and irritate the median nerve. This is common during pregnancy and menopause. Carpal tunnel syndrome that happens during pregnancy tends to get better on its own after pregnancy.
• Other medical conditions. Certain conditions, such as thyroid conditions and kidney failure, may raise the chances of getting carpal tunnel syndrome.

• Workplace factors. Repeated movements that flex the wrist may create pressure on the median nerve. Examples include working with vibrating tools or on an assembly line. Such work also may worsen existing nerve damage. Pressure on the nerve can be worse if the work is done in a cold environment.

  But evidence is not clear, and these factors haven't been proved as direct causes of carpal tunnel syndrome.

  Many studies have explored whether there is a link between computer use and carpal tunnel syndrome. Some evidence suggests that mouse use, but not the use of a keyboard, may be related to carpal tunnel syndrome. There has not been enough evidence to support computer use as a risk factor for carpal tunnel syndrome. But computer use may cause a different form of hand pain.

Prevention

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Ideal seated workstation posture

Ideal seated workstation posture

Lessen stress on the hands and wrists to help prevent carpal tunnel syndrome. While using a keyboard, do not bend the wrists all the way up or down.

There are no proven ways to prevent carpal tunnel syndrome. But you can lessen stress on the hands and wrists with these methods:

• Reduce the force and relax your grip. If your work involves a cash register or keyboard, for instance, hit the keys softly.
• Take short, frequent breaks. Gently stretch and bend your hands and wrists from time to time. Switch up tasks when possible. This is extra important if you use equipment that vibrates or that requires you to use a great amount of force. Taking a break for even a few minutes each hour can make a difference.
• Watch your form. Do not bend your wrist all the way up or down when using a keyboard. A relaxed middle position is best with the wrists in line with the floor. Keep your keyboard at elbow height or slightly lower.
• Improve your posture. Moving your body to view a computer screen can cause the wrong posture. Instead, adjust the screen height and distance to align with a correct posture. The wrong posture rolls shoulders forward, shortens the neck and shoulder muscles, and compresses nerves in the neck. This can cause neck pain and bother the hands and arms.
• Change your computer mouse. Make sure that your computer mouse is easy to use and doesn't strain your wrist.