Carpal tunnel syndrome is one of the most common hand conditions. It is caused by pressure on the median nerve in the carpal tunnel of the wrist. The carpal tunnel is a narrow passageway surrounded by bones and ligaments on the palm side of the hand. When the median nerve is compressed, symptoms can include numbness, tingling and weakness in the thumb and fingers.

Wrist anatomy, health conditions and possibly repetitive hand motions can contribute to carpal tunnel syndrome.

Proper treatment usually relieves the tingling and numbness and restores hand function.

Symptoms of carpal tunnel syndrome usually start gradually and include:

• Tingling and numbness. Tingling and numbness may occur in the fingers or hand. Usually 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 occur while holding a steering wheel, phone or newspaper, or they may wake you from sleep.

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

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

• Weakness. People with carpal tunnel syndrome may experience weakness in the hand and drop objects. This may be due to numbness or to weakness of the thumb's pinching muscles, which also are controlled by the median nerve.

When to see a doctor

See your healthcare professional if you have symptoms of carpal tunnel syndrome that interfere with your usual activities and sleep patterns. Permanent nerve and muscle damage can occur without treatment.

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, known as the carpal tunnel. The median nerve provides sensation to the palm side of the thumb and all of 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 wrist fracture can narrow the carpal tunnel and irritate the nerve. This also may occur due to swelling and inflammation caused by rheumatoid arthritis or other diseases.

Many times, there is no single cause of carpal tunnel syndrome. Or the cause may not be known. It may be that a combination of risk factors contributes to the development of the condition.

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

• Anatomical factors. A wrist fracture or dislocation can alter the space within the carpal tunnel. Arthritis that causes changes to the small bones in the wrist can affect the carpal tunnel. 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 generally more common in women. This may be because the carpal tunnel area is relatively 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.

  Women who have carpal tunnel syndrome also may have smaller carpal tunnels than do women who don't have the condition.

• 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 conditions that cause swelling, known as inflammation, can affect the lining around 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. Being obese is a risk factor for carpal tunnel syndrome.
• Body fluid changes. Fluid retention may increase the pressure within the carpal tunnel, irritating the median nerve. This is common during pregnancy and menopause. Carpal tunnel syndrome that happens with pregnancy generally gets better on its own after pregnancy.
• Other medical conditions. Certain conditions, such as thyroid disorders, kidney failure and lymphedema, may increase the chances of getting carpal tunnel syndrome.

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

  However, the scientific evidence is conflicting and these factors haven't been established as direct causes of carpal tunnel syndrome.

  Several studies have evaluated 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 quality and consistent evidence to support extensive computer use as a risk factor for carpal tunnel syndrome. However, computer use may cause a different form of hand pain.

To diagnose carpal tunnel syndrome, your healthcare professional may ask you questions about your symptoms. You also may need one or more tests to find out whether you have carpal tunnel syndrome:

• History of symptoms. The pattern of your symptoms is important in making a diagnosis. Carpal tunnel syndrome symptoms usually occur while holding a phone or a newspaper or gripping a steering wheel. They also tend to occur at night and may wake you from sleep. Or you may notice the numbness when you wake up in the morning.

  But the median nerve doesn't provide sensation to the little finger. If you have symptoms in that finger, you may have a condition other than carpal tunnel syndrome.

• Physical exam. Your healthcare professional tests the feeling in the fingers and the strength of the muscles in the hand.

  Bending the wrist, tapping on the nerve or simply pressing on the nerve can trigger symptoms in many people.

• X-ray. You may need an X-ray of the affected wrist to exclude other causes of wrist pain, such as arthritis or fracture. However, X-rays are not helpful in making a diagnosis of carpal tunnel syndrome.
• Ultrasound. An ultrasound of the wrist provides a picture of the tendons and nerves. This can help show whether the nerve is being compressed.
• Electromyography. This test measures the tiny electrical discharges produced in muscles. During this test, a thin-needle electrode is inserted into specific muscles to evaluate the electrical activity when muscles contract and rest. This test can identify damage to the muscles controlled by the median nerve. The test also may rule out other conditions.
• Nerve conduction study. In a variation of electromyography, two electrodes are taped to the skin. A small shock is passed through the median nerve to see if electrical impulses are slowed in the carpal tunnel. This test may be used to diagnose the condition and rule out other conditions.

These steps may provide temporary symptom relief:

• Take short, frequent breaks from repetitive activities involving the use of the hands.
• Lose weight if you are overweight or obese.
• Rotate the wrists and stretch the palms and fingers.
• Take a pain reliever, such as acetaminophen (Tylenol, others), aspirin, ibuprofen (Advil, Motrin IB, others) or naproxen sodium (Aleve).
• Wear a snug, not tight, wrist splint at night. You can buy these without a prescription at most drugstores or pharmacies.
• Do not sleep on the hands.

If pain, numbness or weakness persists, see your healthcare professional.

Alternative therapies in your treatment plan may help you manage carpal tunnel syndrome. You may have to experiment to find a treatment that works for you. Always check with your healthcare professional before trying any complementary or alternative treatment.

• Yoga. Yoga postures designed for strengthening, stretching and balancing the upper body and joints may help reduce pain and improve grip strength.
• Hand therapy. Early research suggests that certain physical and occupational hand therapy techniques may reduce symptoms of carpal tunnel syndrome.

Here's some information to help you get ready for your appointment and what to expect from your healthcare professional.

What you can do

• Take note of when your symptoms are at their worst. Does any activity seem to make them worse, or do you notice them at a certain time of day?
• Keep track of the things you've tried to do to make the symptoms better.
• Write down the medicines you've taken to manage your symptoms.

What to expect from your doctor

Your healthcare professional may ask:

• How long have you had the problem?
• Did it come on suddenly or develop over time?
• Is it getting better, getting worse or staying the same?
• Are there certain activities that seem to cause it, make it worse or make it better?

What you can do in the meantime

There are some simple things you can do before you see a healthcare professional for the first time.

First, try to learn whether any activities seem to make your symptoms worse. Change how you do those activities or don't do them, if possible. For example, if driving seems to cause symptoms, try changing the position of your hands on the steering wheel.

You also might try using a wrist splint at night to see if that helps the symptoms.