Carpal tunnel syndrome is a condition in which the median nerve is squeezed where it passes through the wrist. This often happens because the tendons in the wrist have become swollen and they press on the nerve.
The median nerve controls some of the muscles that move the thumb and it carries information back to the brain about sensations in your thumb and fingers. When the nerve is squeezed it can cause pain, aching, tingling or numbness in the affected hand.
The symptoms tend to be worse at night and may disturb your sleep, but you may notice it most when you wake up in the morning. Hanging your hand out of bed or shaking it around will often relieve the pain and tingling.
You may not notice the problem at all during the day, though certain activities – such as writing, typing, DIY or housework – can bring on symptoms.
Sometimes the condition can be mistaken for something else. For example, pressure on nerves in the neck due to disc problems or arthritis can cause similar symptoms.
A nerve conduction test may help if there's any doubt about the diagnosis.
Carpal tunnel syndrome is a common problem. It's often caused by work-related activities, such as typing, and repetitive movements, although some cases may be related to arthritis of the wrist, thyroid disease and pregnancy. Your risk of developing it may be greater if your job places heavy demands on your wrist or if you use vibrating tools.