Warning Thresholds on the Basis of Origin of Amplitude Changes in Transcranial Electrical Motor-Evoked Potential Monitoring for Cervical Compression Myelopathy

Abstract

If we had established the warning threshold as 30% of the control amplitude, we would likely have prevented both cases of postoperative motor deficits, but 106 (30.3%) cases would have become positive cases. If we had established the warning threshold separately as wave disappearance for the spinal tract and 30% of the control amplitude for the spinal segments, sensitivity and specificity would have been 100% and 83.7%, respectively. Dividing the warning threshold on the basis of origin of amplitude changes could reduce false-positive cases and prevent intraoperative injuries.

A new alarm point of transcranial electrical stimulation motor evoked potentials for intraoperative spinal cord monitoring: a prospective multicenter study from the Spinal Cord Monitoring Working Group of the Japanese Society for Spine Surgery and Related Research

“…Based on one false-negative case that resulted in transient paralysis of the patient's triceps muscle, we speculated that there are differences in alarm points between segmental spinal cord injury and spinal tract injury. 15 Further investigation might reveal the differences in the alarm points for spinal pathology and the site of intraoperative spinal cord injury.…”

Exploration of the Intraoperative Motor Evoked Potential

“…At present, there have been lots of studies concerning the application of transcranial motor evoked potential (MEP) to cervical spine surgery, including the value of predicting postoperative neurological deficits 1,2 ; the optimal mode of electric stimulation 3 , and warning thresholds 4 and others. On the contrary, some controversies regarding the intraoperative monitoring also present in cervical surgery, including high false positive rate, 5 low efficiency 6,7 , and lack of reliable warning criteria for CCM.…”

Intraoperative Motor-Evoked Potential Disappearance versus Amplitude-Decrement Alarm Criteria During Cervical Spinal Surgery: A Long-Term Prognosis

“…As found in our study, partial MEP amplitude decrements can lead to immediate postoperative motor deficits, but these issues resolve at 3 to 6 months after surgery. Previous studies employing different alarm criteria have evaluated postoperative motor deficits after different durations, including immediately after surgery,468 24 hours after surgery,11 or at discharge,9 or the exact date of evaluation was not reported or was unclear 235710…”

“…Numerous alarm criteria have been suggested for monitoring intraoperative MEP changes with the aim of preventing postoperative motor deficits, including increases in the stimulation threshold,2 changes in MEP waveform morphology,3 MEP amplitude decrements of 50%,45 70%,67 and 80%8 compared to baseline, and the disappearance of MEPs 91011. Among those, the MEP disappearance has been the primary alarm criterion for spinal cord monitoring due to the varying nature of MEP amplitudes,12 and this criterion can be effective at preventing postoperative motor deficits 913.…”