As with most structures within the human body, there are variations to normal anatomy. The median nerve typically runs just underneath the transverse carpel ligament. After it passes through this ligament it tends to branch off into many smaller nerves. Each of these branches allows for a certain function to occur. One important branch of the median nerve is the motor branch. This nerve branch allows for the movement of the thumb, and its specific location can vary. Another branch of the median nerve provides for feeling of the thumb and palm. It also has many variations in location.
Your doctor is well aware of these variations in nerve branch locations and the techniques used during surgery maximize the protection of the median nerve and its branches. However, because of these variations, in rare instances, it is possible to cut this nerve or its branches during the surgery. This can result in loss of feeling or strength in the palm, thumb or fingers.