The median nerve goes from the forearm through the wrist (carpal tunnel) and into the hand. It is the main source of sensation on the palm side of the fingers and thumbs, except for the little finger. It also provides nerve signals for the muscles in the thumb. Since carpal tunnel syndrome is caused by pressure on the median nerve, anything that irritates or squeezes the median nerve can lead to carpal tunnel syndrome. Damage to the wrist, like breaking it, or other causes of inflammation, can put pressure on the median nerve. Most often, there is not a single cause for the development of carpal tunnel syndrome.