Carpal tunnel syndrome - What is it?

Carpal tunnel syndrome is caused by pressure on a nerve in your wrist. It can be painful. At first, your hand may start to tingle or feel numb at night. You might find you drop things as your grip becomes weaker.

Your carpal tunnel is a narrow gap running through the bones and ligaments in your wrist. A nerve that gives you feeling in your hand (the median nerve) passes through this tunnel. So do the tendons (cords of tissue) that bend your fingers and wrist.

The median nerve passes through your carpal tunnel. Your carpal tunnel is quite narrow and rigid. It's easy for the nerve inside the tunnel to get squeezed. This interferes with the messages that the nerve is sending to your brain. You might feel unusual sensations of numbness, tingling, burning or pain in your thumb, fingers and palm of your hand.[1] Your symptoms could be worse at night or when you wake up (many people sleep with their wrist bent and pressing on the nerve).[2]

It's not easy to say exactly what causes carpal tunnel syndrome.[3] But certain things make you more likely to get it. These things are called risk factors. They include:[3] [4]

Having had a small carpal tunnel since you were born
Getting an injury to your wrist that causes swelling, such as a fracture or sprain
Regularly doing things that put a lot of pressure on the wrist and where you repeat a movement. There are many activities like this. Examples include using power tools, cleaning, sewing and working on an assembly line
Having fluid retention(extra fluid in your body) during pregnancy or the menopause
Having a cyst (a swelling full of fluid) or tumour (a growth) in your carpal tunnel
Having certain medical conditions, such as diabetes or rheumatoid arthritis.[1]
Being overweight (or losing weight quickly) may cause swelling around the median nerve.

References

Rempel D, Evanoff B, Amadio PC, et al. Consensus criteria for the classification of carpal tunnel syndrome in epidemiologic studies. American Journal of Public Health. 1998; 88: 1447-1451.
National Institute of Neurological Disorders and Stroke. Carpal Tunnel Syndrome Fact Sheet. Available at http://www.ninds.nih.gov/disorders/carpal_tunnel/carpal_tunnel.htm (accessed on 12 June 2008).
von Schroeder H, Botte MJ. Carpal tunnel syndrome. Hand Clinics. 1996; 12: 643-655.
De Krom MCTF, Kester A, Knipschild P, et al. Risk factors for carpal tunnel syndrome. American Journal of Epidemiology. 1990; 132: 1102-1110.

Glossary

menopause: When a woman stops having periods, it is called the menopause. This usually happens around the age of 50.
cysts: A cyst is a sac or cavity that develops under your skin and is filled with fluid. Cysts are benign, which means that they are not cancerous.
diabetes: Diabetes is a condition that causes too much sugar (glucose) to circulate in the blood. It happens when the body stops making a hormone called insulin (type 1 diabetes) or when insulin stops working (type 2 diabetes).
rheumatoid arthritis: If you have rheumatoid arthritis, your joints get painful, swollen and stiff. Rheumatoid arthritis is caused by inflammation inside your joints. It happens when your immune system attacks the lining of your joints.

This information does not replace medical advice. If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.