Abstract: A system and method for determining an access trajectory to a target site to safely place a surgical access instrument (e.g., guide wire, dilator, cannula, etc.) through a tissue (e.g., muscle, fat, brain, liver, lung, etc.) without damaging nearby neurovascular structure is described herein. The trajectory determination system includes a nerve stimulation probe and a dilator guide having a plurality of guide channels and registerable to an operating table in a fixed orientation. Motor nerve stimulation (e.g., EMG, MMG) is performed with the stimulation probe positioned in each of said plurality of guide channels to generate a map of nerve locations within intervening anatomical structures (e.g., muscle, bone, etc.) between the dilator guide and the surgical target site. Available access pathways are determined based on the nerve location data and displayed on a display unit.