Carpal tunnel syndrome is pain, tingling, and other problems in your hand because of pressure on the median nerve in your wrist.
The median nerve and several tendons run from your forearm to your hand through a small space in your wrist called the carpal tunnel. The median nerve controls movement and feeling in your thumb and first three fingers (not your little finger).
Pressure on the median nerve causes carpal tunnel syndrome. This pressure can come from swelling or anything that makes the carpal tunnel smaller. Things that can lead to carpal tunnel syndrome include:
Illnesses such as hypothyroidism, rheumatoid arthritis, and diabetes.
Making the same hand movements over and over, especially if the wrist is bent down (your hands lower than your wrists), or making the same wrist movements over and over.
Wrist injuries and bone spurs.
Smoking, because it can reduce blood flow to the median nerve.