Validity of the Alarm Point in Intraoperative Neurophysiological Monitoring of the Spinal Cord by the Monitoring Working Group of the Japanese Society for Spine Surgery and Related Research

Abstract

Study Design. Prospective multicenter cohort study. Objective. The aim of this study was to validate an alarm point of intraoperative neurophysiological monitoring () formulated by the Monitoring Working Group (WG) of the Japanese Society for Spine Surgery and Related Research (JSSR). Summary of Background Data. The Monitoring WG of the JSSR formulated an alarm point of IONM using transcranial electrical stimulation-muscle motor evoked potentials (Tc(E)-MEPs) and has conducted a prospective multicenter study. The validity of the JSSR alarm point of ! 70% decreased in Tc(E)-MEPs for each high-risk surgery and any other spine surgeries has not been verified. Methods. Patients who underwent spine and spinal cord surgery with IONM in 16 Japanese spine centers in the Monitoring WG of the JSSR from 2017 to 2018 were enrolled. The patients were divided into the high-risk surgery group (Group HR) and the common surgery group (Group C). Group HR was defined by ossification of the posterior longitudinal ligament (OPLL), spinal deformity, and spinal cord tumor. Group C was classified as other spine surgeries. The alarm point was defined as a !70% decrease in the Tc(E)-MEPs. Results. In Group HR, the sensitivity and specificity were 94.4% and 87.0%, respectively. In Group C, the sensitivity and specificity were 63.6% and 91.9%. The sensitivity in Group C was statistically lower than that in Group HR (P < 0.05). In Group HR, the sensitivity and specificity in OPLL were 100% and 86.9%, respectively. The sensitivity and specificity in spinal deformity were 87.5% and 84.8%, respectively, and the sensitivity and specificity in spinal cord tumors were 92.9% and 89.9%, respectively. The sensitivity and specificity in each high-risk surgery showed no significant difference. Conclusion. The alarm point of IONM by the Monitoring WG of the JSSR appeared to be valid for each disease in Group HR.

The Utility of Transcranial Stimulated Motor-Evoked Potential Alerts in Cervical Spine Surgery Varies Based on Preoperative Motor Status

“…Similar to our previous studies, a 70% decrease in amplitude from the control waveform was defined as a Tc-MEP alert. [8][9][10] A new-onset motor deficit was defined as an immediate decrease of one or more grades in manual muscle test (MMT) immediately after surgery from preoperative MMT. Any delayed onset paralysis was not included in the new-onset motor deficit group.…”

“…The high-risk group and the general group were classified as follows. The following items were collected for analysis: (1) age, (2) sex, (3) body mass index, (4) type of spinal disorders, (5) incidence of Tc-MEP alert, (6) the surgical maneuvers immediately preceding Tc-MEP alert, (7) motor status; a severe motor status was defined as preoperative MMT grade 3 or less, (8) surgery time (min), ( 9) estimated blood loss (g), (10) range of the surgical site (number of vertebrae), (11) location of surgery (C3-6: mobile vs. occipital-cervical or cervicothoracic: junction), ( 12) type of paralysis: (a) delayed onset segmental palsy, (b) acute onset segmental palsy, and (c) lower limb palsy, and (13) the classification of intradural spinal cord tumors: (a) intramedullary tumors, (b) extramedullary tumors, and (c) dumbbell-shaped tumors. Factors contributing to the occurrence of Tc-MEP alerts that could not be identified with surgical maneuvers Tc-MEP alerts were defined as nonattributed alerts.…”

“…In Japan, the Tc-MEP alert criterion is universally accepted as a 70% decrease in amplitude from the baseline waveform and its accuracy is high. 7,10 However, the positive predictive value (PPV) varies depending on the spinal disorders, surgical technique, and the location of surgery. To the best of our knowledge, the factors contributing to the efficacy of Tc-MEP alerts for cervical spine surgeries have not yet been identified.…”

Current Trends in the Surgical Management of Intramedullary Tumors: A Multicenter Study of 1,033 Patients by the Neurospinal Society of Japan

“…According to the criteria defined by the respective studies, the motor and sensory evoked potentials predicted the emergence of new postoperative neurologic morbidities in 83.8% and 80.8% of the cases, respectively [ 29 ]. Nonetheless, judgments based on spinal cord monitoring may have false-positives and false-negatives in predicting postoperative neurological function [ 30 , 31 ]. Especially, rates of the false-positives were reported as high as 50% and 59% in the 2 recent studies from Japan analyzing intraoperative motor evoked potential recordings [ 30 , 31 ].…”

“…29 Nonetheless, judgments based on spinal cord monitoring may have false-positives and false-negatives in predicting postoperative neurological function. 30,31 Especially, rates of the false-positives were reported as high as 50% and 59% in the 2 recent studies from Japan analyzing intraoperative motor evoked potential recordings. 30,31 Since the critical points in the neuromonitoring in predicting new postoperative deficits were different among studies and have not been established, neurosurgeons should still take responsibility for deciding the degree of surgical resection in each case.…”