The method involves determining whether the change in position is occurred on the basis of pre-operative position of a nerve tract (100) and the intra-operative position of a nerve tract relative to a marker device. The difference in the position is identified when the position of pre-operative nerve tract differs from the position of intra-operative nerve tract and both the positions are respectively displayed. Independent claims are included for the following: (1) computer program for determining and identifying change in position of nerve tract； (2) device for determining and identifying change in position of nerve tract； and (3) navigation system.
