Symptoms and causes

Symptoms

Carpal tunnel syndrome symptoms usually start gradually. The first symptoms often include numbness or tingling in your thumb, index and middle fingers that comes and goes.

Carpal tunnel syndrome may also cause discomfort in your wrist and the palm of your hand. Common carpal tunnel syndrome symptoms include:

  • Tingling or numbness. You may experience tingling and numbness in your fingers or hand. Usually the thumb and index, middle or ring fingers are affected, but not your little finger. Sometimes there is 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. The sensation 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 a tendency to 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.

When to see a doctor

See your doctor if you have persistent signs and symptoms suggestive of carpal tunnel syndrome that interfere with your normal activities and sleep patterns. Permanent 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 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 resulting from rheumatoid arthritis.

There is no single cause in many cases. It may be that a combination of risk factors contributes to the development of the condition.

Risk factors

A number of factors have been associated with carpal tunnel syndrome. Although they may not directly cause carpal tunnel syndrome, they may increase your chances of developing or aggravating median nerve damage. 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 with 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. Illnesses that are characterized by inflammation, such as rheumatoid arthritis, can affect the lining around the tendons in your wrist and put pressure on your median nerve.
  • Obesity. Being obese is a significant risk factor for carpal tunnel syndrome.
  • Alterations in the balance of body fluids. 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 resolves on its own after pregnancy.
  • Other medical conditions. Certain conditions, such as menopause, obesity, thyroid disorders and kidney failure, may increase your chances of carpal tunnel syndrome.
  • Workplace factors. It's possible that 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.

    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 an association between computer use and carpal tunnel syndrome. 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.