The symptoms of carpal tunnel syndrome are caused by compression of the median nerve. The median nerve has two main functions:
- it relays physical sensations, such as your sense of touch, from your hand to your brain, and
- it relays nerve signals from your brain to your hand, allowing you to move your hand and fingers.
The compression of the median nerve can disrupt these nerve signals, which means that both your sense of touch and your ability to move your hand can be affected.
Compression of the median nerve can occur when the tendons that run through the carpal tunnel become inflamed and swollen.
Risk factors for carpal tunnel syndrome
The exact reason why changes to the structure of the carpal tunnel occur in some people is unknown, but a number of risk factors for CTS have been identified. These are outlined below.
Family history:
CTS seems to run in families. About 25% of people with the condition have a close relative who also has CTS. Exactly how and why the condition is spread through families is not fully understood.
Health conditions:
Certain health conditions appear to increase the risk of a person developing CTS. These include:
- rheumatoid arthritis,
- diabetes,
- gout,
- lupus (a condition where the immune system attacks healthy tissue),
- under-active thyroid gland (hypothyroidism),
- obesity; particularly in young people,
- damage or fracture to the wrist,
- oedema (excess fluid in the body’s tissue),
- heart failure, and
- Lyme disease (a bacterial infection that is caused by ticks).
Carpal tunnel syndrome is also common in pregnancy.
Less commonly, CTS occurs when a person has an abnormal wrist structure, such as an unusually narrow carpal tunnel, or as a result of cysts, growths or swellings of the tendons or blood vessels that pass through the carpal tunnel.
