What causes carpal tunnel syndrome?

Carpal tunnel syndrome is caused by compression of a nerve when it passes through the wrist.

The nerve affected is the median nerve, which carries the sense of touch to the thumb and most of the first three fingers, and controls movement for some of the hand muscles.

This nerve runs from the spinal cord down the arm then through the carpal tunnel – a narrow passageway in the wrist with just enough room for the tendons and nerves that pass through it. Swollen or thickened tendons are a sign there is less space for the median nerve, and it can become compressed.

Carpal tunnel syndrome can be caused by anything that makes the nerves or tendons larger, or makes the tunnel that they run through smaller. Common causes include overuse of the wrist, injuries to the wrist, arthritis and pregnancy.

Symptoms can include nerve pain in the hand or wrist, tingling and numbness in the fingers and palm, or a sense of weakness in the hand.

Treatments for carpal tunnel syndrome include splinting the wrist, anti-inflammatory medicines and avoiding activities that are troublesome for the hand. Surgery may be needed for some people.