Apparatus for locating a nerve and for protecting nerves from injury during surgery

An apparatus for locating a nerve, comprising:

• a surgical instrument for delivering a stimulus to a nerve;
• a detector for detecting a response of the nerve to a stimulus delivered to the nerve by said surgical instrument;
• a recorder for recording the intensity of the response of the nerve;
• means for evaluating the recorded response of the nerve, wherein said recorded response is evaluated against a predetermined criterion;
• a modulator for automatically modulating the magnitude of a subsequent stimulus delivered to the nerve, wherein the modulator modifies the subsequent stimulus delivered to the nerve based on the recorded response of the nerve to the previously delivered stimulus so as to hold the level of the nerve's response substantially constant at a predetermined value;
• and
• an indicator for conveying to the user the proximity of the surgical instrument relative to the nerve.