Impact of Preoperative Motor Status for the Positive Predictive Value of Transcranial Motor-Evoked Potentials Alerts in Thoracic Spine Surgery: A Prospective Multicenter Study by the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Prospective multicenter study. OBJECTIVE: To investigate the validity of transcranial motor-evoked potentials (Tc-MEP) in thoracic spine surgery and evaluate the impact of specific factors associated with positive predictive value (PPV). METHODS: One thousand hundred and fifty-six cases of thoracic spine surgeries were examined by comparing patient backgrounds, disease type, preoperative motor status, and Tc-MEP alert timing. Tc-MEP alerts were defined as an amplitude decrease of more than 70% from the baseline waveform. Factors were compared according to preoperative motor status and the result of Tc-MEP alerts. Factors that showed significant differences were identified by univariate and multivariate analysis. RESULTS: Overall sensitivity was 91.9% and specificity was 88.4%. The PPV was significantly higher in the preoperative motor deficits group than in the preoperative no-motor deficits group for both high-risk (60.3% vs 38.3%) and non-high-risk surgery groups (35.1% vs 12.8%). In multivariate logistic analysis, the significant factors associated with true positive were surgical maneuvers related to ossification of the posterior longitudinal ligament (odds ratio = 11.88; 95% CI: 3.17-44.55), resection of intradural intramedullary spinal cord tumor (odds ratio = 8.83; 95% CI: 2.89-27), preoperative motor deficit (odds ratio = 3.46; 95% CI: 1.64-7.3) and resection of intradural extramedullary spinal cord tumor (odds ratio = 3.0; 95% CI: 1.16-7.8). The significant factor associated with false positive was non-attributable alerts (odds ratio = .28; 95% CI: .09-.85). CONCLUSION: Surgeons are strongly encouraged to use Tc-MEP in patients with preoperative motor deficits, regardless of whether they are undergoing high-risk spine surgery or not. Knowledge of PPV characteristics will greatly assist in effective Tc-MEP enforcement and minimize neurological complications with appropriate interventions.

Return-to-Sport Rate, Type of Sport, Frequency of Participation, and Patient Satisfaction After Elective Spinal Surgery in the Elderly Population.

Background: The number of elderly sports participants is increasing, and the possibility of return to sport (RTS) has become an important part of surgical decision making in this population. Purpose: To investigate RTS after elective spinal surgery in elderly patients. Study Design: Case series; Level of evidence, 4. Methods: We enrolled patients aged ≥65 years with a history of preoperative or preinjury sports participation who underwent elective spinal surgery at a single institution between 2019 and 2021. At minimum 12-month follow-up, a questionnaire was administered to each participant to assess postoperative RTS, timing of return, frequency and type of pre- and postoperative activities, and satisfaction (scored 1-10). Descriptive statistical analyses were performed, and regression models were developed to examine the influence of age and sex, as well as surgical site, on RTS. Results: A total of 53 patients (mean ± SD age, 73.8 ± 5.2 years; 24 women) were included, and 23 (43.4%) returned to sports at a median 6 months (interquartile range, IQR, 2-6 months). The RTS rate by surgical site was 17 of 34 (50%) for the lumbar spine and 6 of 17 (35.3%) for the cervical spine. There were no statistically significant differences in RTS rate by surgical site, age, or sex. Overall, 6 of 17 patients returned to golf, 4 of 6 to dance, 2 of 5 to swimming, and 1 of 5 to tennis. Of patients who returned, 34.8% participated in sports 5 times per week and 26.1% participated 3 times per week. The median satisfaction score after RTS was 8 (IQR, 6-9). Conclusion: RTS after spinal surgery was achieved in 43% patients at 1-year minimum follow-up, with high satisfaction scores. More than half of the returning patients participated in sports activities ≥3 times per week.

Role of Transcranial Motor Evoked Potential Monitoring During Traumatic Spinal Injury Surgery: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: A prospective multicenter observational cohort study. OBJECTIVE: This study aimed to investigate the role of transcranial motor evoked potential (TcMEP) monitoring during traumatic spinal injury surgery, the timing of TcMEP alerts, and intervention strategies to avoid intraoperative neurological complications. SUMMARY OF BACKGROUND DATA: Intraoperative neuromonitoring, including TcMEP monitoring, is commonly used in high-risk spinal surgery to predict intraoperative spinal cord injury; however, little information is available on its use in traumatic spinal injury surgery. METHODS: The TcMEP monitoring data of 350 consecutive patients who underwent traumatic spinal injury surgery (mean age, 69.3 y) between 2017 and 2021 were prospectively reviewed. In this study, a TcMEP amplitude reduction ≥70% was established as a TcMEP alert. A rescue case was defined as a case with the recovery of TcMEP amplitudes after certain procedures and without postoperative neurological complications. RESULTS: Among the 350 patients who underwent traumatic spinal injury surgery (TcMEP derivation rate 94%), TcMEP monitoring revealed seven true-positive (TP) (2.0%), three rescues (0.9%; rescue rate 30%), 31 false-positive, one false-negative, and 287 true-negative cases, resulting in 88% sensitivity, 90% specificity, 18% positive predictive value, and 99% negative predictive value. The TP rate in patients with preoperative motor deficits was 2.9%, which was higher than that in patients without preoperative motor deficits (1.1%). The most common timing of TcMEP alerts was during decompression (40%). During decompression, suspension of surgery with intravenous steroid injection was ineffective (rescue rate, 0%), and additional decompression was effective. CONCLUSION: Given the low prevalence of neurological complications (2.3%) and the low positive predictive value (18.4%), single usage of TcMEP monitoring during traumatic spinal injury surgery is not recommended. Further efforts should be made to reduce FP alert rates through better interpretation of multimodal Intraoperative neuromonitorings and the incorporation of anesthesiology to improve the positive predictive value. LEVEL OF EVIDENCE: 3.

Current Trends in Intraoperative Spinal Cord Monitoring: A Survey Analysis among Japanese Expert Spine Surgeons.

Introduction: Although intraoperative spinal neuromonitoring (IONM) is recommended for spine surgeries, there are no guidelines regarding its use in Japan, and its usage is mainly based on the surgeon's preferences. Therefore, this study aimed to provide an overview of the current trends in IONM usage in Japan. Methods: In this web-based survey, expert spine surgeons belonging to the Japanese Society for Spine Surgery and Related Research were asked to respond to a questionnaire regarding IONM management. The questionnaire covered various aspects of IONM usage, including the preferred modality, operation of IONM, details regarding muscle-evoked potential after electrical stimulation of the brain (Br(E)-MsEP), and need for consistent use of IONM in major spine surgeries. Results: Responses were received from 134 of 186 expert spine surgeons (response rate, 72%). Of these, 124 respondents used IONM routinely. Medical staff rarely performed IONM without a medical doctor. Br(E)-MsEP was predominantly used for IONM. One-third of the respondents reported complications, such as bite injuries caused by Br(E)-MsEP. Interestingly, two-thirds of the respondents did not plan responses to alarm points. Intramedullary spinal cord tumor, scoliosis (idiopathic, congenital, or neuromuscular in pediatric), and thoracic ossification of the posterior longitudinal ligament were representative diseases that require IONM. Conclusions: IONM has become an essential tool in Japan, and Br(E)-MsEP is a predominant modality for IONM at present. Although we investigated spine surgeries for which consistent use of IONM is supported, a cost-benefit analysis may be required.

Efficacy of Transcranial Motor Evoked Potential Monitoring During Intra- and Extramedullary Spinal Cord Tumor Surgery: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Multicenter prospective study. OBJECTIVES: Although intramedullary spinal cord tumor (IMSCT) and extramedullary SCT (EMSCT) surgeries carry high risk of intraoperative motor deficits (MDs), the benefits of transcranial motor evoked potential (TcMEP) monitoring are well-accepted; however, comparisons have not yet been conducted. This study aimed to clarify the efficacy of TcMEP monitoring during IMSCT and EMSCT resection surgeries. METHODS: We prospectively reviewed TcMEP monitoring data of 81 consecutive IMSCT and 347 EMSCT patients. We compared the efficacy of interventions based on TcMEP alerts in the IMSCT and EMSCT groups. We defined our alert point as a TcMEP amplitude reduction of ≥70% from baseline. RESULTS: In the IMSCT group, TcMEP monitoring revealed 20 true-positive (25%), 8 rescue (10%; rescue rate 29%), 10 false-positive, a false-negative, and 41 true-negative patients, resulting in a sensitivity of 95% and a specificity of 80%. In the EMSCT group, TcMEP monitoring revealed 20 true-positive (6%), 24 rescue (7%; rescue rate 55%), 29 false-positive, 2 false-negative, and 263 true-negative patients, resulting in a sensitivity of 91% and specificity of 90%. The most common TcMEP alert timing was during tumor resection (96% vs. 91%), and suspension surgeries with or without intravenous steroid administration were performed as intervention techniques. CONCLUSIONS: Postoperative MD rates in IMSCT and EMSCT surgeries using TcMEP monitoring were 25% and 6%, and rescue rates were 29% and 55%. We believe that the usage of TcMEP monitoring and appropriate intervention techniques during SCT surgeries might have predicted and prevented the occurrence of intraoperative MDs.

Efficacy of D-Wave Monitoring Combined With the Transcranial Motor-Evoked Potentials in High-Risk Spinal Surgery: A Retrospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Retrospective multicenter cohort study. OBJECTIVES: We aimed to clarify the efficacy of multimodal intraoperative neuromonitoring (IONM), especially in transcranial electrical stimulation of motor-evoked potentials (TES-MEPs) with spinal cord-evoked potentials after transcranial stimulation of the brain (D-wave) in the detection of reversible spinal cord injury in high-risk spinal surgery. METHODS: We reviewed 1310 patients who underwent TES-MEPs during spinal surgery at 14 spine centers. We compared the monitoring results of TES-MEPs with D-wave vs TES-MEPs without D-wave in high-risk spinal surgery. RESULTS: There were 40 cases that used TES-MEPs with D-wave and 1270 cases that used TES-MEPs without D-wave. Before patients were matched, there were significant differences between groups in terms of sex and spinal disease category. Although there was no significant difference in the rescue rate between TES-MEPs with D-wave (2.0%) and TES-MEPs (2.5%), the false-positivity rate was significantly lower (0%) in the TES-MEPs-with-D-wave group. Using a one-to-one propensity score-matched analysis, 40 pairs of patients from the two groups were selected. Baseline characteristics did not significantly differ between the matched groups. In the score-matched analysis, one case (2.5%) in both groups was a case of rescue (P = 1), five (12.5%) cases in the TES-MEPs group were false positives, and there were no false positives in the TES-MEPs-with-D-wave group (P = .02). CONCLUSIONS: TES-MEPs with D-wave in high-risk spine surgeries did not affect rescue case rates. However, it helped reduce the false-positivity rate.

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

STUDY DESIGN: A prospective multicenter observational study. OBJECTIVE: The aim was to investigate the validity of transcranial motor-evoked potentials (Tc-MEP) in cervical spine surgery and identify factors associated with positive predictive value when Tc-MEP alerts are occurred. SUMMARY OF BACKGROUND DATA: The sensitivity and specificity of Tc-MEP for detecting motor paralysis are high; however, false-positives sometimes occur. MATERIALS AND METHODS: The authors examined Tc-MEP in 2476 cases of cervical spine surgeries and compared patient backgrounds, type of spinal disorders, preoperative motor status, surgical factors, and the types of Tc-MEP alerts. Tc-MEP alerts were defined as an amplitude reduction of more than 70% from the control waveform. Tc-MEP results were classified into two groups: false-positive and true-positive, and items that showed significant differences were extracted by univariate analysis and detected by multivariate analysis. RESULTS: Overall sensitivity was 66% (segmental paralysis: 33% and lower limb paralysis: 95.8%) and specificity was 91.5%. Tc-MEP outcomes were 33 true-positives and 233 false-positives. Positive predictive value of general spine surgery was significantly higher in cases with a severe motor status than in a nonsevere motor status (19.5% vs . 6.7%, P =0.02), but not different in high-risk spine surgery (20.8% vs . 19.4%). However, rescue rates did not significantly differ regardless of motor status (48% vs . 50%). In a multivariate logistic analysis, a preoperative severe motor status [ P =0.041, odds ratio (OR): 2.46, 95% confidence interval (95% CI): 1.03-5.86] and Tc-MEP alerts during intradural tumor resection ( P <0.001, OR: 7.44, 95% CI: 2.64-20.96) associated with true-positives, while Tc-MEP alerts that could not be identified with surgical maneuvers ( P =0.011, OR: 0.23, 95% CI: 0.073-0.71) were associated with false-positives. CONCLUSION: The utility of Tc-MEP in patients with a preoperative severe motor status was enhanced, even in those without high-risk spine surgery. Regardless of the motor status, appropriate interventions following Tc-MEP alerts may prevent postoperative paralysis.

Transcranial Motor-evoked Potentials for Intraoperative Nerve Root Monitoring During Adult Spinal Deformity Surgery: A Prospective Multicenter Study.

STUDY DESIGN: A prospective, multicenter study. OBJECTIVE: This study clarified the uses and limitations of transcranial motor-evoked potentials (Tc-MEPs) for nerve root monitoring during adult spinal deformity (ASD) surgeries. SUMMARY OF BACKGROUND DATA: Whether Tc-MEPs can detect nerve root injuries (NRIs) in ASD surgeries remains controversial. MATERIALS AND METHODS: We prospectively analyzed neuromonitoring data from 14 institutions between 2017 and 2020. The subjects were ASD patients surgically treated with posterior corrective fusion using multichannel Tc-MEPs. An alert was defined as a decrease of ≥70% in the Tc-MEP's waveform amplitude from baseline, and NRI was considered as meeting the focal Tc-MEP alerts shortly following surgical procedures with postoperative nerve root symptoms in the selected muscles. RESULTS: A total of 311 patients with ASD (262 women and 49 men) and a mean age of 65.5 years were analyzed. Tc-MEP results revealed 47 cases (15.1%) of alerts, including 25 alerts after 10 deformity corrections, six three-column osteotomies, four interbody fusions, three pedicle screw placements or two decompressions, and 22 alerts regardless of surgical maneuvers. Postoperatively, 14 patients (4.5%) had neurological deterioration considered to be all NRI, 11 true positives, and three false negatives (FN). Two FN did not reach a 70% loss of baseline (46% and 65% loss of baseline) and one was not monitored at target muscles. Multivariate logistic regression analysis revealed that risk factors of NRI were preexisting motor weakness ( P <0.001, odds ratio=10.41) and three-column osteotomies ( P =0.008, odds ratio=7.397). CONCLUSIONS: Nerve root injuries in our ASD cohort were partially predictable using multichannel Tc-MEPs with a 70% decrease in amplitude as an alarm threshold. We propose that future research should evaluate the efficacy of an idealized warning threshold (e.g., 50%) and a more detailed evoked muscle selection, in reducing false negatives.

Efficacy of Intraoperative Neuromonitoring Using Transcranial Motor-Evoked Potentials for Degenerative Cervical Myelopathy: A Prospective Multicenter Study by the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: A prospective multicenter observational study. OBJECTIVE: To elucidate the efficacy of transcranial motor-evoked potentials (Tc(E)-MEPs) in degenerative cervical myelopathy (DCM) surgery by comparing cervical spondylotic myelopathy (CSM) to cervical ossification of the posterior longitudinal ligament (OPLL) and investigate the timing of Tc(E)-MEPs alerts and types of interventions affecting surgical outcomes. SUMMARY OF BACKGROUND DATA: Although CSM and OPLL are the most commonly encountered diseases of DCM, the benefits of Tc(E)-MEPs for DCM remain unclear and comparisons of these two diseases have not yet been conducted. METHODS: We examined the results of Tc(E)-MEPs from 1176 DCM cases (840 CSM /336 OPLL) and compared patients background by disease, preoperative motor deficits, and the type of surgical procedure. We also assessed the efficacy of interventions based on Tc(E)-MEPs alerts. Tc(E)-MEPs alerts were defined as an amplitude reduction of more than 70% below the control waveform. Rescue cases were defined as those in which waveform recovery was achieved after interventions in response to alerts and no postoperative paralysis. RESULTS: Overall sensitivity was 57.1%, and sensitivity was higher with OPLL (71.4%) than with CSM (42.9%). The sensitivity of acute onset segmental palsy including C5 palsy was 40% (OPLL/CSM: 66.7%/0%) whereas that of lower limb palsy was 100%. The most common timing of Tc(E)-MEPs alerts was during decompression (63.16%), followed by screw insertion (15.79%). The overall rescue rate was 57.9% (OPLL/CSM: 58.3%/57.1%). CONCLUSION: Since Tc(E)-MEPs are excellent for detecting long tract injuries, surgeons need to consider appropriate interventions in response to alerts. The detection of acute onset segmental palsy by Tc(E)-MEPs was partially possible with OPLL, but may still be difficult with CSM. The rescue rate was higher than 50% and appropriate interventions may have prevented postoperative neurological complications.Level of Evidence: 3.

Transcranial Motor-evoked Potential Alert After Supine-to-Prone Position Change During Thoracic Ossification in Posterior Longitudinal Ligament Surgery: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: A prospective, multicenter study. OBJECTIVE: To evaluate the usefulness of transcranial motor-evoked potentials (Tc-MEPs) during supine-to-prone position change for thoracic ossification of the posterior longitudinal ligament (T-OPLL). SUMMARY OF BACKGROUND DATA: Supine-to-prone position change might be a risk of spinal cord injury in posterior decompression and fusion surgeries for T-OPLL. METHODS: The subjects were 145 patients with T-OPLL surgically treated with posterior decompression and fusion using Tc-MEPs in 14 institutes. Tc-MEPs were monitored before surgery from supine-to-prone position and intraoperatively in seven institutes and only intraoperatively in the other seven institutes because of disapproval of the anesthesia department. In cases of Tc-MEP alert after position change, we adjusted the cervicothoracic posture. When the MEP did not recover, we reverted the position to supine and monitored the Tc-MEPs in supine position. RESULTS: There were 83 and 62 patients with/without Tc-MEP before position change to prone (group A and B). The true-positive rate was lower in group A than group B, but without statistical significance (8.4% vs. 16.1%, P = 0.12). In group A, five patients who had Tc-MEP alert during supine-to-prone position change were all female and had larger body mass index values and upper thoracic lesions. Among the patients, three underwent surgeries after cervicothoracic alignment adjustment, and two had postponed operations to 1 week later with halo-vest fixation because of repeated Tc-MEP alerts during position change to prone. The Tc-MEP alert at exposure was statistically more frequent in group B than in group A ( P = 0.033). CONCLUSION: Tc-MEP alert during position change is an important sign of spinal cord injury due to alignment change at the upper thoracic spine. Tc-MEP monitoring before supine-to-prone position change was necessary to prevent spinal cord injury in surgeries for T-OPLL.

Characteristics of Tc-MEP Waveforms for Different Locations of Intradural Extramedullary Tumors: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Prospective multicenter study. OBJECTIVE: To examine transcranial motor-evoked potential (Tc-MEP) waveforms in intraoperative neurophysiological monitoring in surgery for intradural extramedullary (IDEM) tumors, focused on the characteristics for cervical, thoracic, and conus lesions. SUMMARY OF BACKGROUND DATA: IDEM tumors are normally curable after resection, but neurological deterioration may occur after surgery. Intraoperative neurophysiological monitoring using Tc-MEPs during surgery is important for timely detection of possible neurological injury. METHODS: The subjects were 233 patients with IDEM tumors treated surgically with Tc-MEP monitoring at 9 centers. The alarm threshold was ≥70% waveform deterioration from baseline. A case with a Tc-MEP alert that normalized and had no new motor deficits postoperatively was defined as a rescue case. A deterioration of manual muscle test score ≥1 compared to the preoperative value was defined as postoperative worsening of motor status. RESULTS: The 233 patients (92 males, 39%) had a mean age of 58.1 ±â€Š18.1 years, and 185 (79%), 46 (20%), and 2 (1%) had schwannoma, meningioma, and neurofibroma. These lesions had cervical (C1-7), thoracic (Th1-10), and conus (Th11-L2) locations in 82 (35%), 96 (41%), and 55 (24%) cases. There were no significant differences in preoperative motor deficit among the lesion levels. Thoracic lesions had a significantly higher rate of poor baseline waveform derivation (0% cervical, 6% thoracic, 0% conus, P < 0.05) and significantly more frequent intraoperative alarms (20%, 31%, 15%, P < 0.05). Use of Tc-MEPs for predicting neurological deficits after IDEM surgery had sensitivity of 87% and specificity of 89%; however, the positive predictive value was low. CONCLUSION: Poor derivation of waveforms, appearance of alarms, and worse final waveforms were all significantly more frequent for thoracic lesions. Thus, amplification of the waveform amplitude, using multimodal monitoring, and more appropriate interventions after an alarm may be particularly important in surgery for thoracic IDEM tumors.Level of Evidence: 3.

Characteristics of Cases with Poor Transcranial Motor-evoked Potentials Baseline Waveform Derivation in Spine Surgery: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Prospective multicenter study. OBJECTIVE: The purpose of the study is to examine cases with poor baseline waveform derivation for all muscles in multichannel monitoring of transcranial motor-evoked potentials (Tc-MEPs) in spine surgery. SUMMARY OF BACKGROUND DATA: Intraoperative neuromonitoring (IONM) is useful for identifying neurologic deterioration during spinal surgery. Tc-MEPs are widely used for IONM, but some cases have poor waveform derivation, even in multichannel Tc-MEP monitoring. METHODS: The subjects were 3625 patients (mean age 60.1 years, range 4-95; 1886 females, 1739 males) who underwent Tc-MEP monitoring during spinal surgery at 16 spine centers between April 2017 and March 2020. Baseline Tc-MEPs were recorded from the deltoid, abductor pollicis brevis, adductor longus, quadriceps femoris, hamstrings, tibialis anterior, gastrocnemius, and abductor hallucis (AH) muscles after surgical exposure of the spine. RESULTS: The 3625 cases included cervical, thoracic, and lumbar lesions (50%, 33% and 17%, respectively) and had preoperative motor status of no motor deficit, and motor deficit with manual muscle testing (MMT) ≥3 and MMT <3 (70%, 24% and 6%, respectively). High-risk surgery was performed in 1540 cases (43%). There were 73 cases with poor baseline waveform derivation (2%), and this was significantly associated with higher body weight, body mass index, thoracic lesions, motor deficit of MMT <3, high-risk surgery (42/1540 [2.7%] vs. 31/2085 [1.5%], P < 0.05), and surgery for ossification of the posterior longitudinal ligament (OPLL). Intraoperative waveform derivation occurred in 25 poor derivation cases (34%) and the AH had the highest rate. CONCLUSION: The rate of poor baseline waveform derivation in spine surgery was 2% in our series. This was significantly more likely in high-risk surgery for thoracic lesions and OPLL, and in cases with preoperative severe motor deficit. In such cases, it may be preferable to use multiple modalities for IONM to derive multichannel waveforms from distal limb muscles, including the AH.Level of Evidence: 3.

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: A Prospective Multicenter Cohort Study of 1934 Cases.

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. Meanwhile, applying the JSSR alarm point for Group C potentially needed attention.Level of Evidence: 3.

Effects of Preoperative Motor Status on Intraoperative Motor-evoked Potential Monitoring for High-risk Spinal Surgery: A Prospective Multicenter Study.

STUDY DESIGN: Prospective multicenter observational study. OBJECTIVE: To evaluate transcranial motor-evoked potentials (Tc-MEPs) baseline characteristics of lower limb muscles and to determine the accuracy of Tc-MEPs monitoring based on preoperative motor status in surgery for high-risk spinal disease. SUMMARY OF BACKGROUND DATA: Neurological complications are potentially serious side effects in surgery for high-risk spine disease. Intraoperative spinal neuromonitoring (IONM) using Tc-MEPs waveforms can be used to identify neurologic deterioration, but cases with preoperative motor deficit tend to have poor waveform derivation. METHODS: IONM was performed using Tc-MEPs for 949 patients in high-risk spinal surgery. A total of 4454 muscles in the lower extremities were chosen for monitoring. The baseline Tc-MEPs was recorded immediately after exposure of the spine. The derivation rate was defined as muscles detected/muscles prepared for monitoring. A preoperative neurological grade was assigned using the manual muscle test (MMT) score. RESULTS: The 949 patients (mean age 52.5 ±â€Š23.3 yrs, 409 males [43%]) had cervical, thoracic, thoracolumbar, and lumbar lesions at rates of 32%, 40%, 26%, and 13%, respectively. Preoperative severe motor deficit (MMT ≤3) was present in 105 patients (11%), and thoracic ossification of the posterior longitudinal ligament (OPLL) was the most common disease in these patients. There were 32 patients (3%) with no detectable waveform in any muscles, and these cases had mostly thoracic lesions. Baseline Tc-MEPs responses were obtained from 3653/4454 muscles (82%). Specificity was significantly lower in the severe motor deficit group. Distal muscles had a higher waveform derivation rate, and the abductor hallucis (AH) muscle had the highest derivation rate, including in cases with preoperative severe motor deficit. CONCLUSION: In high-risk spinal surgery, Tc-MEPs collected with multi-channel monitoring had significantly lower specificity in cases with preoperative severe motor deficit. Distal muscles had a higher waveform derivation rate and the AH muscle had the highest rate, regardless of the severity of motor deficit preoperatively.Level of Evidence: 3.

Characteristics of Tc-MEP Waveforms in Spine Surgery for Patients with Severe Obesity.

STUDY DESIGN: Prospective multicenter study. OBJECTIVE: The aim of this study was to evaluate transcranial motor evoked potential (Tc-MEP) waveform monitoring in spinal surgery for patients with severe obesity. SUMMARY OF BACKGROUND DATA: Spine surgeries in obese patients are associated with increased morbidity and mortality. Intraoperative Tc-MEP monitoring can identify neurologic deterioration during surgery, but has not been examined for obese patients. METHODS: The subjects were 3560 patients who underwent Tc-MEP monitoring during spine surgery at 16 centers. Tc-MEPs were recorded from multiple muscles via needle or disc electrodes. A decrease in Tc-MEP amplitude of ≥70% from baseline was used as an alarm during surgery. Preoperative muscle weakness with manual muscle test (MMT) grade ≤4 was defined as a motor deficit, and a reduction of one or more MMT grade postoperatively was defined as deterioration. RESULTS: The 3560 patients (1698 males, 47.7%) had a mean age of 60.0 ±â€Š20.3 years. Patients with body mass index >35 kg/m2 (n = 60, 1.7%) were defined as severely obese. Compared with all other patients (controls), the rates of preoperative motor deficit (41.0% vs. 29.6%, P < 0.05) and undetectable baseline waveforms in all muscles were significantly higher in the severely obese group (20.0% vs. 1.7%, P < 0.01). Postoperative motor deterioration did not differ significantly between the groups. The sensitivity and specificity of the alarm criterion for prediction of postoperative neurologic complications were 75.0% and 83.9% in severely obese patients and 76.4% and 89.6% in controls, with no significant difference between the groups. CONCLUSION: Tc-MEPs can be used in spine surgery for severely obese cases to predict postoperative motor deficits, but the rate of undetectable waveforms is significantly higher in such cases. Use of a multichannel waveform approach or multiple modalities may facilitate safe completion of surgery. Waveforms should be carefully evaluated and an appropriate rescue procedure is required if the alarm criterion occurs.Level of Evidence: 3.

Efficacy of Intraoperative Intervention Following Transcranial Motor-evoked Potentials Alert During Posterior Decompression and Fusion Surgery for Thoracic Ossification of the Posterior Longitudinal Ligament: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Prospective, multicenter, observational study. OBJECTIVE: The aim of this study was to investigate the efficacy of intervention after an alert in intraoperative neurophysiological monitoring (IONM) using transcranial motor-evoked potentials (Tc-MEPs) during surgery for thoracic ossification of the posterior longitudinal ligament (T-OPLL). SUMMARY OF BACKGROUND DATA: T-OPLL is commonly treated with posterior decompression and fusion with instrumentation. IONM using Tc-MEPs during surgery reduces the risk of neurological complications. METHODS: The subjects were 79 patients with a Tc-MEP alert during posterior decompression and fusion surgery for T-OPLL. Preoperative muscle strength (manual muscle testing [MMT]), waveform derivation rate at the start of surgery (baseline), intraoperative waveform changes; and postoperative motor paralysis were examined. A reduction in MMT score of ≥1 on the day after surgery was classified as worsened postoperative motor deficit. An alert was defined as a decrease in Tc-MEP waveform amplitude of ≥70% from baseline. Alerts were recorded at key times during surgery. RESULTS: The patients (35 males, 44 females; age 54.6 years) had OPLL at T1-4 (n = 27, 34%), T5-8 (n = 50, 63%), and T9-12 (n = 16, 20%). The preoperative status included sensory deficit (n = 67, 85%), motor deficit (MMT ≤4) (n = 59, 75%), and nonambulatory (n = 26, 33%). At baseline, 76 cases (96%) had a detectable Tc-MEP waveform for at least one muscle, and the abductor hallucis had the highest rate of baseline waveform detection (n = 66, 84%). Tc-MEP alerts occurred during decompression (n = 47, 60%), exposure (n = 13, 16%), rodding (n = 5, 6%), pedicle screw insertion (n = 4, 5%), posture change (n = 4, 5%), dekyphosis (n = 2, 3%), and other procedures (n = 4, 5%). After intraoperative intervention, the rescue rate (no postoperative neurological deficit) was 57% (45/79), and rescue cases had a significantly better preoperative ambulatory status and a significantly higher baseline waveform derivation rate. CONCLUSION: These results show the efficacy of intraoperative intervention following a Tc-MEP alert for prevention of neurological deficit postoperatively.Level of Evidence: 2.

Arthroscopic treatment for Morel-Lavallée lesion of the thigh: A case report and literature review.

INTRODUCTION: Morel-Lavallée lesion (MLL) is a posttraumatic closed degloving soft tissue injury, in which the subcutaneous tissues are separated from the underlying fascia. Surgical treatment is recommended if conservative management fails. The conventional surgical treatment for the lesion is surgical drainage and debridement. PRESENTATION OF CASE: A 51-year-old male patient presented with swelling of the right thigh incurred during a traffic accident. The lesion was diagnosed with MLL. The MLL was successfully treated with a minimally invasive arthroscopic treatment after failure of conservative treatment. The arthroscopic treatment was chosen because of the patient's comorbidity that posed a risk of surgical wound complications. In addition, negative pressure wound therapy (NPWT) was performed postoperatively to ensure healing and to prevent recurrence of the lesion. The patient was successfully treated and the healing of the lesion was also confirmed with MRI. DISCUSSION: In a patient with a risk of wound complications due to a comorbidity, this minimally invasive arthroscopic treatment is useful. In addition, NPWT was used to ensure healing and to prevent recurrence. Although the use of NPWT combined with endoscopic treatment has not been reported, additional NPWT reported in this case may be helpful to ensure healing. CONCLUSION: In case of MLL with a risk of surgical complications, the arthroscopic treatment is a reasonable method and achieves the goal of an open surgical debridement without increased morbidity.

Understanding the effect of non-surgical factors in a transcranial motor-evoked potential alert: A retrospective cohort study.

BACKGROUND: Intraoperative neuromonitoring (IONM) is important for detecting neurological dysfunction, allowing for intervention and reversal of neurological deficits before they become permanent. Of the several IONM modalities, transcranial electrical stimulation of motor-evoked potential (TES-MEP) can help monitor the activity in the pyramidal tract. Surgery- and non-surgery-related factors could result in a TES-MEP alert during surgery. Once the alert occurs, the surgeon should immediately intervene to prevent a neurological complication. However, TES-MEP monitoring does not provide sufficient data to identify the non-surgery-related factors. Therefore, this study aimed to identify and describe these factors among TES-MEP alert cases. METHODS: In this multicenter study, data from 1934 patients who underwent various spinal surgeries for spinal deformities, spinal cord tumors, and ossification of the posterior longitudinal ligament of the spine from 2017 to 2019 were collected. A 70% amplitude reduction was set as the TES-MEP alarm threshold. All surgeries with alerts were categorized into true-positive (TP) and false-positive (FP) cases according to the assessment of immediate postoperative neurological deficits. RESULTS: In total, TES-MEP alerts were observed in 251 cases during surgery: 62 TP and 189 FP IONM cases. Overall, 158 cases were related to non-surgery-related factors. We observed 22 (35.5%) TP cases and 136 (72%) FP cases, which indicated cases associated with non-surgery-related factors. A significant difference was observed between the two groups regarding factors associated with TES-MEP alerts (p < 0.01). The ratio of TP and FP cases (related to non-surgery-related factors) associated with TES-MEP alerts was 13.9% (22/158 cases) and 86.1% (136/158 cases), respectively. CONCLUSIONS: Non-surgery-related factors are proportionally higher in FP than in TP cases. Although the surgeon should examine surgical procedures immediately after a TES-MEP alert, surgical intervention may not always be the best approach according to the results of this study.

Adverse Events Related to Transcranial Electric Stimulation for Motor-evoked Potential Monitoring in High-risk Spinal Surgery.

STUDY DESIGN: Prospective multicenter study. OBJECTIVE: The aim of this study was to study the incidence of nonneurologic adverse events related to transcranial electric stimulation (TES) for intraoperative spinal cord monitoring (IOM) with motor-evoked potentials (MEPs) (Tc(E)- MEPs) and determine the need for safety precautions. SUMMARY OF BACKGROUND DATA: Tc(E)-MEPs monitoring requires high-voltage multipulse TES that causes widespread muscle contraction and movement. Improved awareness of TES-induced movement-related adverse events is needed. METHODS: We analyzed data from 2643 patients who underwent high-risk spinal surgery with intraoperative Tc(E)-MEPs at 11 spinal centers from 2010 to 2016. Information about neurologic and non-neurologic postoperative complications was collected, including type of surgical procedure, operative time, estimated blood loss, and treatment for postoperative adverse events. RESULTS: A 70% drop in Tc(E)-MEPs amplitude, which was the alarm criterion to interrupt surgery, predicted postoperative motor deficits with 93.5% sensitivity, 91.0% specificity, a false-positive rate of 8.2%, and a false-negative rate of 0.3%. Non-neurologic adverse events developed in 17 (0.64%) patients and were most commonly because of bite injuries (0.57%), including 11 cases of tongue laceration, two cases of lip laceration, and two cases of tooth breakage. Four (0.15%) tongue lacerations required surgical repair with sutures and two tooth breakages required dental treatment. One patient had hair loss corresponding to the TES site. One patient, who underwent additional IOM with transpharyngeal stimulation, had severe nasal hemorrhage following electrode placement by nasal route, which resolved spontaneously. Non-neurologic adverse events did not significantly affect the accuracy of IOM assessment. Neither operative times nor blood loss significantly influenced the occurrence of adverse events. CONCLUSION: During TES-IOM, both the surgeon and monitoring team must consider the possibility-although rare-of non-neurologic adverse events, particularly bite injuries. Such complications can be minimized by using a soft bite-block and frequently evaluating the intraoral integrity of the anesthetized patient. LEVEL OF EVIDENCE: 4.

Alert Timing and Corresponding Intervention With Intraoperative Spinal Cord Monitoring for High-Risk Spinal Surgery.

STUDY DESIGN: Prospective multicenter study. OBJECTIVE: To analyze the incidence of intraoperative spinal neuromonitoring (IONM) alerts and neurological complications, as well as to determine which interventions are most effective at preventing postoperative neurological complications following IONM alerts in high risk spinal surgeries. SUMMARY OF BACKGROUND DATA: IONM may play a role in identifying and preventing neural damage; however, few studies have clarified the outcomes of intervention after IONM alerts. METHODS: We analyzed 2867 patients who underwent surgery for high risk spinal pathology using transcranial electrical motor-evoked potentials from 2010 to 2016. The high-risk spinal surgery cases consisted of 1009 spinal deformity cases, 622 cervical ossification of posterior longitudinal ligament (OPLL) cases, 249 thoracic-OPLL cases, 771 extramedullary spinal cord tumor cases, and 216 intramedullary spinal cord tumor (IMSCT) cases. We set a 70% amplitude reduction as the alarm threshold for transcranial electrical motor-evoked potentials and analyzed the outcomes of the interventions following monitoring alerts and postoperative neurological deficits. RESULTS: The true positive, false positive, true negative, false negative, and rescue cases of IONM comprised 126, 234, 2362, 9, and 136 cases, respectively. Most alerts and interventions occurred during correction and release in deformity cases, posterior decompression and dekyphosis in OPLL cases, and tumor resection and surgery suspension with steroid injection in spinal cord tumor cases; however, individual interventions varied. The rescue rates (number of patients rescued with intervention after IONM alert/number of true positive cases plus rescue cases) for deformity, cervical-OPLL, thoracic--OPLL, extramedullary spinal cord tumor, and IMSCT cases were 61.4% (35/57), 82.1% (32/39), 40% (20/50), 52.5% (31/59), and 31.6% (18/57), respectively. CONCLUSION: Our prospective multicenter study identified potential neural damage in 9.5% of cases and 52% rescue cases using IONM. Although the rescue ratios for t-OPLL and IMSCT were relatively low, appropriate intervention immediately after an IONM alert may prevent neural damage even in high-risk spinal surgeries. LEVEL OF EVIDENCE: 3.