Neural locating system

1. A neural monitoring system comprising:

an elongate medical instrument having a distal end portion configured to extend within an intracorporeal treatment area of a subject, the elongate medical instrument including a plurality of electrodes disposed on the distal end portion, each electrode respectively being configured to provide an electrical stimulus;

a non-invasive mechanical sensor configured to be placed in mechanical communication with a muscle of the subject and to generate a mechanomyography output signal corresponding to a sensed mechanical movement of the muscle; and

a processor in communication with the elongate medical instrument and the mechanical sensor, and configured to:

provide a respective electrical stimulus to each of the plurality of electrodes, the electrical stimulus having a predetermined current magnitude;

receive the mechanomyography output signal; and

triangulate a relative direction between a nerve and the distal end portion of the elongate medical instrument via an amplitude of the received mechanomyography output signal and a current magnitude of each respective electrical stimulus, wherein the nerve innervates the muscle.

2. The system of claim 1 , wherein the processor is configured to provide the respective electrical stimulus to each of the plurality of electrodes in a sequential manner.

3. The system of claim 1 , wherein the processor is configured to provide the respective electrical stimulus to each of the plurality of electrodes in a concurrent manner;

wherein each respective electrical stimulus includes a plurality of current pulses provided at a stimulation frequency; and

wherein the stimulation frequency for each respective electrical stimulus is unique.

4. The system of claim 1 , wherein the non-invasive mechanical sensor includes an accelerometer, a microphone, a strain gauge, or a piezoelectric device.

5. The system of claim 1 , further comprising a display device; and

wherein the processor is further configured to provide an indication of the relative direction between the nerve and the distal end portion of the elongate medical instrument via the display device.

6. The system of claim 1 , wherein the processor is further configured to maintain a three dimensional nerve map using the triangulated relative direction between the nerve and the distal end portion of the elongate medical instrument and a monitored location of the distal end portion of the elongate medical instrument within the intracorporeal treatment area.

7. The system of claim 6 , further comprising a display device; and

wherein the processor is further configured to display the three dimensional nerve map via the display device.

8. The system of claim 6 , further comprising a display device; and

wherein the processor is further configured to merge the three dimensional nerve map with an anatomical image, and display the merged three dimensional nerve map and anatomical image via the display device.

9. The system of claim 6 , further comprising a robotic controller operative to control the motion of the elongate medical instrument; and

wherein processor is further configured to output the three dimensional nerve map to the robotic controller; and

wherein the robotic controller is configured to at least one of control or constrain the motion of the elongate medical instrument in response to the received three dimensional nerve map.

10. A neural monitoring system comprising:

an elongate medical instrument having a distal end portion configured to extend within an intracorporeal treatment area of a subject, the elongate medical instrument including at least four electrodes disposed on the distal end portion, each electrode respectively being configured to provide an electrical stimulus;

a non-invasive mechanical sensor configured to be placed in mechanical communication with a muscle of the subject and to generate a mechanomyography output signal corresponding to a sensed mechanical movement of the muscle; and

a processor in communication with the elongate medical instrument and the mechanical sensor, and configured to:

provide a respective electrical stimulus to each of the at least four electrodes, the electrical stimulus having a predetermined current magnitude;

receive the mechanomyography output signal; and

triangulate a relative direction between a nerve and the distal end portion of the elongate medical instrument via an amplitude of the received mechanomyography output signal and a current magnitude of each respective electrical stimulus, wherein the nerve innervates the muscle.

11. The system of claim 10 , wherein the elongate medical instrument has a longitudinal axis extending between a proximal end portion and the distal end portion of the instrument; and

wherein three of the at least four electrodes define a plane that is transverse to the longitudinal axis.

12. The system of claim 11 , wherein one of the at least four electrodes is disposed on a distal side of the plane and is separated from the plane by a distance.

13. The system of claim 10 , wherein the processor is configured to provide the respective electrical stimulus to each of the at least four electrodes in a sequential manner.

14. The system of claim 10 , wherein the processor is configured to provide the respective electrical stimulus to each of the at least four electrodes in a concurrent manner;

wherein each respective electrical stimulus includes a plurality of current pulses provided at a stimulation frequency; and

wherein the stimulation frequency for each respective electrical stimulus is unique.

15. The system of claim 10 , wherein the non-invasive mechanical sensor includes an accelerometer, a microphone, a strain gauge, or a piezoelectric device.

16. The system of claim 10 , wherein the at least four electrodes is at least 8 electrodes disposed in a common plane.