Carpal tunnel syndrome is caused by pressure on the median nerve. The carpal tunnel is a narrow passageway surrounded by bones and ligaments on the palm side of your hand. When the median nerve is compressed, the symptoms can include numbness, tingling and weakness in the hand and arm.
The anatomy of your wrist, health problems and possibly repetitive hand motions can contribute to
carpal tunnel syndrome.
Proper treatment usually relieves the tingling and numbness and restores wrist and hand function.
Carpal tunnel syndrome symptoms usually start gradually and include:
- Tingling or numbness. You may notice tingling and numbness in your fingers or hand. Usually the thumb and index, middle or ring fingers are affected, but not your little finger. You might feel a sensation like an electric shock in these fingers.
The sensation may travel from your wrist up your arm. These symptoms often occur while holding a steering wheel, phone or newspaper, or may wake you from sleep.
Many people “shake out” their hands to try to relieve their symptoms. The numb feeling may become constant over time.
- Weakness. You may experience weakness in your hand and drop objects. This may be due to the numbness in your hand or weakness of the thumb’s pinching muscles, which are also controlled by the median nerve.
Carpal tunnel syndrome is caused by pressure on the median nerve.
The median nerve runs from your forearm through a passageway in your wrist (carpal tunnel) to your
hand. It provides sensation to the palm side of your thumb and fingers, except the little finger. It also provides nerve signals to move the muscles around the base of your thumb (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, as can the swelling and inflammation caused by rheumatoid arthritis.
Many times, there is no single cause of carpal tunnel syndrome. It may be that a combination of risk
factors contributes to the development of the condition.
A number of factors have been associated 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:
- Anatomic factors. A wrist fracture or dislocation, or arthritis that deforms the small bones in the wrist, can alter the space within the carpal tunnel and put pressure on the median nerve.
People who have smaller carpal tunnels may be more likely to have carpal tunnel syndrome.
- Sex. 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.
Women who have carpal tunnel syndrome may also have smaller carpal tunnels than women who don’t have the condition.
- Nerve-damaging conditions. Some chronic illnesses, such as diabetes, increase your risk of nerve damage, including damage to your median nerve.
- Inflammatory conditions. Rheumatoid arthritis and other conditions that have an inflammatory component can affect the lining around the tendons in your wrist and put pressure on your median nerve.
- Medications. Some studies have shown a link between carpal tunnel syndrome and the use of anastrozole (Arimidex), a drug 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 your carpal tunnel, irritating the median nerve. This is common during pregnancy and menopause. Carpal tunnel syndrome associated with pregnancy generally gets better on its own after pregnancy.
- Other medical conditions. Certain conditions, such as menopause, thyroid disorders, kidney failure and lymphedema, may increase your chances of carpal tunnel syndrome.
- Workplace factors. Working with vibrating tools or on an assembly line that requires prolonged or repetitive flexing of the wrist may create harmful pressure on the median nerve or worsen existing nerve damage, especially if the work is done in a cold environment.
However, the scientific evidence is conflicting and these factors haven’t been established work as direct causes of carpal tunnel syndrome.
Several studies have evaluated whether there is an association between computer use and carpal tunnel syndrome. Some evidence suggests that it is mouse use, and not the use of a keyboard, that may be the problem. However, there has not been enough quality and consistent evidence to support extensive computer use as a risk factor for carpal tunnel syndrome, although it may cause a different form of hand pain.
There are no proven strategies to prevent carpal tunnel syndrome, but you can minimize stress on
your hands and wrists with these methods:
- Reduce your force and relax your grip. If your work involves a cash register or keyboard, for instance, hit the keys softly. For prolonged handwriting, use a big pen with an oversized, soft grip adapter and free-flowing ink.
- Take short, frequent breaks. Gently stretch and bend hands and wrists periodically. Alternate tasks when possible. This is especially important if you use equipment that vibrates or that requires you to exert a great amount of force. Even a few minutes each hour can make a difference.
- Watch your form. Avoid bending your wrist all the way up or down. A relaxed middle position is best. Keep your keyboard at elbow height or slightly lower.
- Improve your posture. Incorrect posture rolls shoulders forward, shortening your neck and shoulder muscles and compressing nerves in your neck. This can affect your wrists, fingers and hands, and can cause neck pain.
- Change your computer mouse. Make sure that your computer mouse is comfortable and doesn’t strain your wrist.
- Keep your hands warm. You’re more likely to develop hand pain and stiffness if you work in a cold environment. If you can’t control the temperature at work, put on fingerless gloves that keep your hands and wrists warm.
Your doctor may ask you questions and conduct one or more of the following tests to determine
whether you have carpal tunnel syndrome:
- History of symptoms. Your doctor will review the pattern of your symptoms. For example, because the median nerve doesn’t provide sensation to your little finger, symptoms in that finger may indicate a problem other than carpal tunnel syndrome.
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 during the night, or you may notice the numbness when you wake up in the morning.
- Physical examination. Your doctor will conduct a physical examination. He or she will test the feeling in your fingers and the strength of the muscles in your hand.
Bending the wrist, tapping on the nerve or simply pressing on the nerve can trigger symptoms in many people.
- X-ray. Some doctors recommend an X-ray of the affected wrist to exclude other causes of wrist pain, such as arthritis or a fracture. However, X-rays are not helpful in making a diagnosis of carpal tunnel syndrome.
- Electromyography. This test measures the tiny electrical discharges produced in muscles. During this test, your doctor inserts a thin-needle electrode 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, and also may rule out other conditions.
- Nerve conduction study. In a variation of electromyography, two electrodes are taped to your 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 your condition and rule out other conditions.
Treat carpal tunnel syndrome as early as possible after symptoms start. In the early stages, simple
things that you can do for yourself may make the problem go away. For example:
- Take more-frequent breaks to rest your hands.
- Avoid activities that make symptoms worse.
- Apply cold packs to reduce swelling.
options include wrist splinting, medications and surgery. Splinting and other conservative treatments are more likely to help if you’ve had only mild to moderate symptoms that come and go for less than 10 months. If you have numbness in your hands, you need to see a doctor.
If the condition is diagnosed early, nonsurgical methods may help improve carpal tunnel syndrome,
- Wrist splinting. A splint that holds your wrist still while you sleep can help relieve nighttime symptoms of tingling and numbness. Even though you only wear the splint at night, it can also help prevent daytime symptoms. Nighttime splinting may be a good option if you’re pregnant because it does not involve the use of any medications to be effective.
- Nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs, such as ibuprofen (Advil, Motrin IB, others), may help relieve pain from carpal tunnel syndrome in the short term.
There isn’t evidence, however, that these drugs improve carpal tunnel syndrome.
- Corticosteroids. Your doctor may inject your carpal tunnel with a corticosteroid such as cortisone to relieve pain. Sometimes your doctor uses an ultrasound to guide these injections.
Corticosteroids decrease inflammation and swelling, which relieves pressure on the median nerve. Oral corticosteroids aren’t considered as effective as corticosteroid injections for treating carpal
If carpal tunnel syndrome is caused by rheumatoid arthritis or another inflammatory arthritis, then treating the arthritis may reduce symptoms of carpal tunnel syndrome.
However, this is unproved.
Carpal tunnel release
Surgery may be appropriate if your symptoms are severe or don’t respond to other treatments.
The goal of carpal tunnel surgery is to relieve pressure by cutting the ligament pressing on the
The surgery may be performed with two different techniques:
- Endoscopic surgery. Your surgeon uses a telescope-like device with a tiny camera attached to it (endoscope) to see inside your carpal tunnel. Your surgeon cuts the ligament through one or two small incisions in your hand or wrist. Some surgeons may use ultrasound instead of a telescope to guide the tool that cuts the ligament.
Endoscopic surgery may result in less pain than does open surgery in the first few days or weeks after surgery.
- Open surgery. Your surgeon makes an incision in the palm of your hand over the carpal tunnel and cuts through the ligament to free the nerve.
Discuss the risks and benefits of each technique with your surgeon before surgery. Surgery risks may
- Incomplete release of the ligament
- Wound infections
- Scar formation
- Injuries to the nerves or blood vessels
During the healing process after the surgery, the ligament tissues gradually grow back together while allowing more room for the nerve. This internal healing process typically takes several months, but the skin heals in a few weeks.
Your doctor generally will encourage you to use your hand after the ligament has healed, gradually
working back to normal use of your hand while initially avoiding forceful hand motions or extreme wrist positions.
Soreness or weakness may take from several weeks to a few months to resolve after surgery. If your
symptoms were very severe, symptoms may not go away completely after surgery.