What are the causes of Carpal tunnel syndrome?
For most patients, the cause of their carpal tunnel syndrome is unknown. In most of the cases symptoms of carpal tunnel syndrome (CTS) are caused by squashing (compression) of the median nerve at the wrist.
The median nerve runs from your forearm through a passageway in your wrist (carpal tunnel) to your hand. The median nerve is responsible for two main functions:
- Carrying physical sensations such as your sense of touch from your hand to your brain
- Carrying nerve signals from your brain to your hand, controlling movement
Any pressure on the median nerve can disrupt the nerve signals, affecting your sense of touch and hand movements.
The median nerve can become compressed if the tissues inside the tunnel become swollen or the tunnel narrows over time.
What are the risk factors for Carpal tunnel syndrome?
In most cases, it's not known what causes the median nerve to become compressed, although a number of things increase the risk of developing CTS. These include:
- 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.