Electromyography System
Methods for determining structural integrity of a bone within the spine of a patient, the bone having a first aspect and a second aspect, wherein the second aspect separated from the first aspect by a width and located adjacent to a spinal nerve. The methods involve (a) applying an electrical stimulus to the first aspect of the bone; (b) electrically monitoring a muscle myotome associated with the spinal nerve to detect if an onset neuro-muscular response occurs in response to the application of the electrical stimulus to the first aspect of the bone; (c) automatically increasing the magnitude of the electrical stimulus to until the onset neuro-muscular response is detected; and (d) communicating to a user via at least one of visual and audible means information representing the magnitude of the electrical stimulus which caused the onset neuro-muscular response.
1 . A method of advancing a surgical instrument to a spinal target site during surgery, comprising,
(a) advancing said surgical instrument toward said spinal target site via a minimally invasive approach through the body tissue of a patient containing one or more spinal nerves;
(b) emitting from an electrode situated near a distal end of said surgical instrument a stimulation signal of known intensity while concurrently monitoring for the presence of a resulting neuro-muscular response from at least one electromyography electrode positioned on the patient and configured to detect the electrical charge associated with muscle activity;
(c) automatically varying the intensity of said stimulation signal until a neuromuscular response is detected;
(d) comparing the stimulation intensity level at which the neuro-muscular response was detected to a predetermined stimulation intensity level to indicate the relative proximity of said spinal nerve to said distal end of said surgical instrument;
(e) communicating to a user the determined relative proximity; and
(f) adjusting one of the position and trajectory of advancement of said surgical instrument away from said spinal nerve when said relative proximity of said spinal nerve to said distal end of said instrument is determined to be too close.
2 . The method of claim 1 , wherein said surgical instrument is a surgical probe.
3 . The method of claim 1 , wherein said surgical instrument is a surgical access instrument.
4 . The method of claim 3 , wherein said surgical instrument is a cannula.
5 . The method of claim 1 , wherein the intensity level of the stimulation signal is incrementally varied.
6 . The method of claim 1 , wherein the intensity level of the stimulation signal is increased.
7 . The method of claim 1 , wherein said spinal nerve is one of a plurality of spinal nerves exiting from successive vertebrae.
8 . The method of claim 1 , wherein communicating to said operator involves at least one of visually and audibly indicating to said operator the intensity level of the stimulus signal that resulted in said neuro-muscular response.
9 . The method of claim 8 , wherein audibly indicating to said user involves sounding an alarm to indicate the relative proximity determined.
10 . The method of claim 9 , wherein the volume of the alarm is varied depending on the relative proximity determined.
11 . The method of claim 9 , wherein the frequency of the alarm is varied depending on the relative proximity determined.
12 . The method of claim 8 , wherein visually indicating to said user involves the step of displaying a color.
13 . The method of claim 12 , wherein the color is varied depending on the relative proximity of the nerve detected.
14 . The method of claim 1 , further comprising:
repeating steps (a)-(f) until said surgical instrument said spinal target site.
15 . The method of claim 5 , wherein the stimulation signal is varied by constant increments.
16 . The method of claim 15 , wherein the intensity of the stimulation signal is increased by 0.5 mA increments.
17 . The method of claim 7 , wherein the intensity of the stimulation signal is increased by 4 mA increments.
18 . The method of claim 7 , wherein the intensity of the stimulation signal is increased within a range having a minimum stimulation intensity level and a maximum stimulation intensity level.
19 . The method of claim 1 , wherein said neuromuscular response comprises an EMG response having an amplitude greater than a predetermined minimum value.
20 . The method of claim 19 , wherein said amplitude greater than a predetermined minimum amplitude is a peak-to-peak amplitude greater than the predetermined minimum value.