Causes
The median nerve carries messages between the thumb, index finger, middle finger, and the brain. Pain, touch, and sensation are transmitted to the brain and instructions to move muscles are sent from the brain.
The transverse ligament runs across the inside of the wrist like a watch strap. The carpal tunnel is the space between this and the bones on the outside of the wrist. The tendons, muscles of the fingers, blood vessels, and nerves pass through it. The median nerve lies on top of them on the inside of the wrist. There is just enough room for it between the tendons and the transverse ligament.
Carpal tunnel syndrome results when there is increased pressure on the median nerve and tendons within the carpal tunnel. It is usually a combination of things that causes the increased pressure. Factors that contribute to the development of carpal tunnel syndrome include:
- trauma or injury to the wrist
- certain medical conditions (e.g., rheumatoid arthritis, hypothyroidism or underactive thyroid, diabetes)
- repetitive movements of the hand or wrist
- cysts or tumors
- pregnancy
- frequent use of vibrating hand tools
- having wrists too small for all the ligaments and nerves to fit properly
In many cases, the exact cause cannot be determined.