Your carpal tunnel is a narrow passageway that runs through your wrist. The passageway is held open by small bones, and the roof of the tunnel is made of a band of connective tissue.
This entire structure serves to protect the median nerve that runs from your forearm into your hand. This nerve controls the muscles at the base of your thumb and enables sensation in your index, middle, and ring fingers and thumb.
Carpal tunnel syndrome happens when this passageway becomes narrowed, adding pressure to the median nerve. That can happen in several ways.