Transcranial Motor-evoked Potentials Research Articles

Clinical Neurophysiological Methods Verify Improvement in the Motor Neural Transmission in Patients with Surgically Treated Idiopathic Scoliosis in Long-Term Follow-up

The evaluation of patients after the surgical correction of idiopathic scoliosis in a long-term follow-up with clinical neurophysiological methods has not been presented in detail. This study aimed to compare the results of neurophysiological studies in 45 girls with scoliosis of Lenke types 1–3 performed pre- (T0) and postoperatively, 1 week after surgery (T1) and 6 months after surgery (T2). The parameter values of the surface electromyography while attempting maximal contraction (mcsEMG) and the transcranial motor-evoked potentials (MEPs) recorded in the anterior tibial muscles, as well as the electroneurography (ENG) of the peripheral transmission in the peroneal nerve motor fibers, were compared. The results indicate that efferent neural conduction function both centrally and peripherally, and TA muscle function slightly improved immediately after the surgical correction of scoliosis, and further normalization appeared after six months in the long-term follow-up (at p = 0.03). The sEMG recordings indicate that half a year after surgical treatment in IS patients, the TA muscle motor unit recruitment function, as well as the muscle strength evaluated with Lovett’s scale, was comparable to the normal condition. The ENG recording results indicated a gradual reduction in the motor fiber injury symptoms, mainly of the axonal type, in the peroneal nerves. The surgeries also improved the lumbar ventral roots’ neural transmission to a normal functional status. The MEP amplitude parameter values recorded after the surgical scoliosis corrections in T1 indicated a slight improvement in the efferent transmission of neural impulses within the fibers of the spinal tracts; in the long-term T2 observation period, they reached values comparable to those recorded in healthy volunteers, bilaterally. Preoperatively (T0), the results of all the neurophysiological study parameters in the IS patients were asymmetrical at p = 0.036–0.05 and recorded as worse on the concave side, suggesting the lateralization of neurological motor deficits. One week postoperatively (T1), this asymmetry was recorded as gradually reduced, showing almost no difference between the right and left sides six months later (T2). The presented algorithm for the neurophysiological assessments performed in the pre-, intra-, and long-term postoperative periods using the mcsEMG, MEP, and ENG neurophysiological examinations, together with the clinical studies, may help in the comprehensive functional evaluation of the spinal cord tracts and ventral root neural conduction, which allows the detection of the subclinical neurological changes related to scoliosis itself and the consequences of the corrective surgery. Such an evaluation can also be significant in making final decisions regarding IS surgeries and their personalization after attempting conservative treatments with bracing and kinesiotherapy. Neurophysiological studies, as a sensitive biomarker, allowed us to predict and ascertain the final result of IS treatment in the long-term follow-up, which showed the health status of patients as being comparable to that of healthy volunteers.

Influence of Preoperative Motor Score and Patient Comorbidities on Transcranial Motor-Evoked Potential Acquisition in Intracranial Surgery: A Retrospective Cohort Study.

Intraoperative neurophysiological monitoring plays a pivotal role in modern neurosurgery, aiding in real-time assessment of eloquent neural structures to mitigate iatrogenic neural injury. This study represents the largest retrospective series to date in monitoring corticospinal tract integrity during intracranial surgery with transcranial motor-evoked potentials (TCMEPs), focusing on the influence of demographic factors, comorbidities, and preoperative motor deficits on the reliability of intraoperative neurophysiological monitoring. While the impact of patient-specific factors affecting TCMEP monitoring in spine surgery is well-documented, similar insights for intracranial surgery are lacking. A total of 420 craniotomy patients were retrospectively analyzed from electronic medical records from December 2017 to February 2023, excluding patients without preoperative Medical Research Council scores or medical histories. Using intrinsic hand muscles as a robust data set, 840 hand TCMEPs acquired during intracranial surgery were assessed. Demographic and clinical factors, including preoperative motor scores, were analyzed to identify associations with TCMEP acquisition and amplitude. Nonparametric statistics and multivariate regression analysis were employed. TCMEPs were successfully acquired in 734 (87.7%) patient hands, even in the presence of preoperative motor deficits in 13.9% of total patient hands. Preoperative motor scores did not predict the ability to acquire baseline TCMEPs (P = .6). Notably, older age (P < .001) and hypertension (P = .01) were independent predictors of lower TCMEP acquisition rates. Preoperative motor scores significantly influenced TCMEP amplitudes, with higher scores correlating with higher amplitudes (1771 [SD = 1550] eve vs 882 [SD = 856] μV, P < .0001). Older age (P < .001) and chronic kidney disease (P = .04) were also associated with reduced TCMEP amplitudes. Our investigation into TCMEPs during intracranial surgery demonstrated a notably high acquisition rate in hand muscles, irrespective of preoperative motor deficits. Preoperative motor scores reliably correlated with TCMEP amplitudes in a linear fashion while advanced age and renal disease emerged as independent predictors of lower TCMEP amplitudes.

Intraoperative seizures during neuro-oncological supratentorial surgery: the role of prophylaxis with levetiracetam and intraoperative monitoring in a consecutive series of 353 patients.

The aim of this paper was to understand the role of prophylaxis with levetiracetam at skin incision in preventing convulsive intraoperative seizures (IOS) during neurosurgical procedures with and without intraoperative neuromonitoring (IONM). Authors retrospectively reviewed the Institutional database for cases of supratentorial brain tumors undergoing surgical resection performed from January 2021 to October 2022. Patients were operated on both under general anesthesia and awake, using motor-evoked potentials (MEP) and direct cortical stimulation for cortical mapping. 1000 mg ev of Levetiracetam before skin incision in case of a history of seizures was administrated. We excluded all infratentorial cases. Three hundred fisty three consecutive cases were retrieved. IOS occurred in 22 patients (6.2%). Prophylaxis with Levetiracetam was administered in 149 patients, and IOS occurred in 16 cases (10.7%) in this group of patients. The IOS rate in the case of no Levetiracetam prophylaxis administration (3.5%) was significantly lower (P<0.001, OR=3.38 [1.35-8.45], RR=3.12 [1.32-7.41]). The Penfield technique stimulation evoked seven of all 22 IOS reported (31.8%) (P=0.006, RR 5.4 [1.44 -20.58], OR 21 [2.3-183.9]), and the train-of-five technique stimulation caused two of all registered IOS (8.7%) (P=0.2, RR 2.3 [0.99-5.67], OR 6.5 [0.55-76.17]). Transcranial MEPs evoked no IOS. Under levetiracetam prophylaxis, the IOS rate was not significantly lower than in the group of patients without Levetiracetam prophylaxis, regardless of the histology of the tumor and IONM. Neither the transcranial stimulation (MEP) nor train-of-five technique stimulation increases the risk of convulsive IOS, as Penfield technique stimulation does.

Effects of Anesthetic Choice on the Incidence of Transcranial-Motor Potential-Induced Oral Trauma

ABSTRACT Transcranial motor-evoked potentials (TcMEPs) play an integral role in assessing motor tract function in surgical procedures where motor function is at risk. However, transcranial stimulation creates a risk for oral trauma. Several studies have reported on distinct factors that can influence the rate of TcMEP-induced oral trauma, but little is known about how an anesthetic regimen can influence this rate. In this retrospective review, we investigated the incidence of oral injury under total intravenous anesthesia (TIVA) and balanced anesthesia in 66,166 cases from 2019 to 2021. There were 295 oral injuries in our sample, yielding an incidence of 0.45%, which is in line with ranges reported in the literature. A total of 222 of the injured patients were sedated with balanced anesthesia, while the remaining 73 were under TIVA anesthetics. This difference in distribution was statistically significant (p < 0.0002). Our findings suggest TIVA is associated with lower risk of oral trauma when TcMEPs are monitored, thereby improving patient safety.

Transcranial Motor Evoked Potentials as a Predictive Modality for Postoperative Deficit in Cervical Spine Decompression Surgery - A Systematic Review and Meta-Analysis.

Systematic Review and Meta-analysis. The purpose of this study was to evaluate whether transcranial motor evoked potential (TcMEP) alarms can predict postoperative neurologic complications in patients undergoing cervical spine decompression surgery. A meta-analysis of the literature was performed using PubMed, Web of Science, and Embase to retrieve published reports on intraoperative TcMEP monitoring for patients undergoing cervical spine decompression surgery. The sensitivity, specificity, and diagnostic odds ratio (DOR), of overall, reversible, and irreversible TcMEP changes for predicting postoperative neurological deficit were calculated. A subgroup analysis was performed to compare anterior vs posterior approaches. Nineteen studies consisting of 4608 patients were analyzed. The overall incidence of postoperative neurological deficits was 2.58% (119/4608). Overall TcMEP changes had a sensitivity of 56%, specificity of 94%, and DOR of 19.26 for predicting deficit. Reversible and irreversible changes had sensitivities of 16% and 49%, specificities of 95% and 98%, and DORs of 3.54 and 71.74, respectively. In anterior procedures, TcMEP changes had a DOR of 17.57, sensitivity of 49%, and specificity of 94%. In posterior procedures, TcMEP changes had a DOR of 21.01, sensitivity of 55%, and specificity of 94%. TcMEP monitoring has high specificity but low sensitivity for predicting postoperative neurological deficit in cervical spine decompression surgery. Patients with new postoperative neurological deficits were 19 times more likely to have experienced intraoperative TcMEP changes than those without new deficits, with irreversible TcMEP changes indicating a much higher risk of deficit than reversible TcMEP changes.

Multimodal Intraoperative Neurophysiological Monitoring in Cranial and Spinal Tumour Surgeries: A Descriptive Observational Study.

Intraoperative neurophysiological monitoring (IONM) involves monitoring the functional integrity of critical brain regions and pathways as well as identifying and preserving functionally viable neural tissues (mapping) during surgery using electrophysiological techniques. Multimodality combines various neurophysiological techniques to optimise diagnostic effectiveness and to improve the outcomes of the surgeries. The present study is a case series with comprehensive and illustrative descriptions of the neurophysiological changes in five neuromonitored cases of cranial and spinal cord tumour surgeries conducted with a multimodal approach. The cases were monitored with somatosensory evoked potentials (SSEP), transcranial motor evoked potentials (TcMEP), and both free run and triggered electromyography (fEMG and tEMG). No false negative outcomes were identified in the cases studied as there was an association of absence of change in SSEP and TcMEP both, with no neurological deficit postoperatively.Two cases were identified as having true positive neuromonitoring alerts.No false positive alerts were found in any case. Multimodal monitoring using SSEP, TcMEP, and EMG (fEMG and tEMG) in cranial and spinal tumour surgeries can improve performance with fewer false-negative and false-positive results. Neuromonitoring approaches used in combination can provide reliable information regarding postoperative neurological outcomes.

Feasibility, Safety and Reliability of Surgeon-Directed Transcranial Motor Evoked Potentials Monitoring in Scoliosis Surgery.

(1) Background: Neuromonitoring is essential in corrective surgery for scoliosis. Our aim was to assess the feasibility, safety and reliability of "surgeon-directed" intraoperative monitoring transcranial motor evoked potentials (MEP) of patients. (2) Methods: A retrospective single-center study of a cohort of 190 scoliosis surgeries, monitored by NIM ECLIPSE (Medtronic), between 2017 and 2021. Girls (144) and boys (46) (mean age of 15 years) were included. There were 149 idiopathic and 41 secondary scoliosis. The monitoring consisted of stimulating the primary motor cortex to record the MEP with muscular recording on the thenar, vastus lateralis, tibialis anterior and adductor hallucis muscles. (3) Results: The monitoring data was usable in 180 cases (94.7%), with 178 true negatives, no false negatives and one false positive. There was one true positive case. The predictive negative value was 100%. The monitoring data was unusable in 10 cases (i.e., three idiopathic and seven secondary scoliosis). (4) Conclusions: Simplified transcranial MEP monitoring known as "surgeon-directed module" is usable, safety and reliable in surgery for moderate scoliosis. It is feasible in 95% of cases with a negative predictive value of 100%.

Utility of transcranial motor-evoked potential changes in predicting postoperative deficit in lumbar decompression and fusion surgery: a systematic review and meta-analysis.

The primary aim of this study was to evaluate whether TcMEP alarms can predict the occurrence of postoperative neurological deficit in patients undergoing lumbar spine surgery. The secondary aim was to determine whether the various types of TcMEP alarms including transient and persistent changes portend varying degrees of injury risk. This was a systematic review and meta-analysis of the literature from PubMed, Web of Science, and Embase regarding outcomes of transcranial motor-evoked potential (TcMEP) monitoring during lumbar decompression and fusion surgery. The sensitivity, specificity, and diagnostic odds ratio (DOR) of TcMEP alarms for predicting postoperative deficit were calculated and presented with forest plots and a summary receiver operating characteristic curve. Eight studies were included, consisting of 4923 patients. The incidence of postoperative neurological deficit was 0.73% (36/4923). The incidence of deficits in patients with significant TcMEP changes was 11.79% (27/229), while the incidence in those without changes was 0.19% (9/4694). All TcMEP alarms had a pooled sensitivity and specificity of 63 and 95% with a DOR of 34.92 (95% CI 7.95-153.42). Transient and persistent changes had sensitivities of 29% and 47%, specificities of 96% and 98%, and DORs of 8.04 and 66.06, respectively. TcMEP monitoring has high specificity but low sensitivity for predicting postoperative neurological deficit in lumbar decompression and fusion surgery. Patients who awoke with new postoperative deficits were 35 times more likely to have experienced TcMEP changes intraoperatively, with persistent changes indicating higher risk of deficit than transient changes. Diagnostic Systematic Review.

Effect of intraoperative muscle relaxation reversal on the success rate of motor evoked potential recording in patients undergoing spinal surgery: a randomized controlled trial

BackgroundPartial neuromuscular blockade (NMB) has been applied for some surgeries to reduce bleeding and prevent patient movement for spinal surgery. Sugammadex selectively binds to rocuronium in the plasma and consequently lowers the rocuronium concentration at the neuromuscular junction. In this study, we aimed to observe whether the success rate of transcranial motor-evoked potential (TceMEP) can be increased by sugammadex compared with partial NMB during spinal surgery.MethodsPatients who underwent elective spinal surgery with TceMEP monitoring were randomly assigned to the sugammadex group and control group. Rocuronium was continuously infused to maintain the train of four counts (TOFc) = 2. The sugammadex group discontinued rocuronium infusion at the time of TceMEP monitoring and was infused with 2 mg/kg sugammadex; the control group was infused with the same dose of saline.ResultsA total of 171 patients were included. The success rate of TceMEP monitoring in the sugammadex group was significantly higher than that in the control group. TceMEP amplitudes were greater in the sugammadex group than in the control group at 5 min, 10 min, and 20 min after the start of motor-evoked potential monitoring. The latencies of upper extremity TceMEPs monitoring showed no difference between groups. TOF ratios were greater in the sugammadex group at 5 min, 10 min, and 20 min after the start of motor-evoked potential monitoring. There were no adverse effects caused by sugammadex.ConclusionsSugammadex can improve the success rate of motor-evoked potential monitoring compared with moderate neuromuscular blockade induced by continuous infusion of rocuronium in spinal surgery.Trial registrationThe study was registered on clinicaltrials.gov.cn on 29/10/2020 (trial registration number: NCT04608682).

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.

Prospective multicenter study. 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). 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. 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). 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.

Total Intravenous Anesthesia Protocol for Decreasing Unacceptable Movements during Cerebral Aneurysm Clipping with Motor-Evoked Potential Monitoring: A Historical Control Study and Meta-Analysis.

Injury can occur during intraoperative transcranial motor-evoked potential (MEP) monitoring caused by patient movement related to insufficient neuromuscular blocking agent use. Here, we evaluated the incidence of unacceptable movements in patients undergoing intraoperative MEP monitoring following our anesthetic protocol. We reviewed the anesthesia records of 419 patients who underwent unruptured cerebral aneurysm clipping with intraoperative MEP monitoring. The anesthetic protocol included target-controlled infusion with a fixed effect-site propofol concentration of 3 μg/mL and an adjustable effect-site remifentanil concentration of 10-12 ng/mL. We compared our findings of the intraoperative parameters and incidence of spontaneous movement and respiration with those of published meta-analysis studies. Spontaneous movement and respiration occurred in one (0.2%) patient each. The meta-analysis included six studies. The pooled proportions of spontaneous movement and respiration were 6.9% (95% confidence interval [CI], 1.3-16.5%) and 4.1% (95% CI, 0.5-14.1%), respectively. The proportion of spontaneous movement in our study was significantly lower than that in previous studies (p = 0.013), with no significant difference in spontaneous respiration (p = 0.097). Following our center's anesthesia protocol during cerebral aneurysm clipping resulted in a low incidence of spontaneous respiration and movement, indicating its safety for patients undergoing intraoperative MEP monitoring.

The adjunct use of descending neurogenic-evoked potentials when transcranial motor-evoked potentials degrade into warning criteria in pediatric spinal deformity surgery: minimizing false-positive events.

This studies objective was to evaluate the utility of descending neurogenic-evoked potentials (DNEPs) in the setting of transcranial motor-evoked potentials (TCeMEPs) degradation into warning criteria during pediatric spinal deformity surgery. An institutional spinal cord monitoring database was queried to identify all primary and revision pediatric spinal deformity cases, < / = 21years of age performed from 1/2006 to 12/2021, in which TCeMEPs were the primary motor tract assessment modality which degraded into warning criteria, with subsequent initiation of adjunct DNEPs. Fourteen surgical cases (0.42%; 3351 total cases) in fourteen patients met inclusion criteria. Mean age was 13.2years (7.5-21.3). syndromic (n = 7), kyphosis (n = 3), congenital (n = 2), and idiopathic (n = 2). Three-column osteotomies (3CO)were done in eight patients. TCeMEPs degraded into warning criteria during screw placement (n = 7), 3CO performance/closure (n = 4), or deformity correction (n = 3). DNEPs were present in all cases of warning-criteria TCeMEPs and one case had degradation of DNEPs. Intraoperative Stagnara wake-up tests were performed in only 2/14 cases, with one transient new neurologic deficit (NND). In this specific scenario, DNEPs sensitivity was 50%, specificity 100%, positive predictive value 100%, and negative predictive value 92% to detect aNND. DNEPs were useful in assessing spinal cord function in the setting of TCeMEP data degradation in complex pediatric deformity surgeries. DNEPs demonstrated a higher specificity and positive predictive value in this clinical setting than TCeMEPs when assessing long-term neurologic function after surgery. Based on this small cohort, DNEPs appear to be a useful adjunct modality to TCeMEPs, in this challenging clinical scenario.

Transcranial MEP threshold voltages and current densities simulated with finite element modelling

ObjectiveThe aim of this study was to compare stimulation thresholds and current densities in the brain for transcranial motor evoked potentials (tcMEPs) from the hands and feet with linked quadripolar (LQP), M3-M4 and C1-C2 electrode montages. MethodsTwenty-five patients underwent cerebral vascular surgery with tcMEP monitoring. tcMEP voltage thresholds were compared between LQP (C1, M3, C2, M4), C1-C2, and M3-M4 montages. In a finite element model (FEM), hand, arm, and leg regions of interest (ROIs) on the cortical motor homunculus were segmented. Current densities in these ROIs at tcMEP thresholds were compared across tcMEP electrode montages. ResultsLQP tcMEP thresholds were 61.5 volts for hands and 95.2 volts for feet. Thresholds were higher for M3-M4 (hands, 89.4 V; feet, 141.3 V) and C1-C2 (hands: 137.3 V; feet: 194.7 V). Total current at threshold voltage was greater for LQP (hands, 210.9 mA; feet, 311.3 mA) compared to M3-M4 (hands, 166.8 mA; feet, 256.6 mA), but similar to C1-C2 (hands, 246.7 mA; feet, 341.1 mA). In FEM simulations, current density and local current density topography in the hand ROI at threshold were very similar for LQP, M3-M4 and C1-C2. ConclusionsTcMEP voltage thresholds were least for LQP, and lesser for M3-M4 compared to C1-C2. In FEM simulations, resistance to current to hand ROI was ordered the same (LQP < M3-M4 < C1-C2). The local distribution of current density in motor cortex with tcMEP was mainly determined by cortical geometry. SignificanceCurrent densities and resistance to current simulated with FEM may explain threshold requirements for tcMEP electrode montages.

Impact of multimodal intraoperative neurophysiological monitoring of the spinal cord during spine and spinal cord surgeries

BackgroundThere is growing evidence of the valuable role of multimodal intraoperative neurophysiological monitoring (IONM) during spine and spinal cord surgeries, as it provides an opportunity to recognize functional changes of the neural elements, usually in the reversible stage, during complex surgical manipulations. Therefore, it may reduce the risk of postoperative neurological dysfunction and improve functional outcomes. The aim of the current study was to evaluate the efficacy of multimodal IONM for preventing and predicting iatrogenic neurological dysfunction during spinal cord and spine surgeries.ResultsSignificant alerts had occurred in 9 out of 24 patients; however, all the changes were reversible and did not contribute to postoperative clinical deterioration. Only one case got worsened in the early postoperative follow-up period, with stable intraoperative monitoring.ConclusionIntraoperative monitoring is a valuable tool in spine and spinal cord surgeries. Combined transcranial motor-evoked potential (TcMEP), somatosensory-evoked potential (SSEP), and spontaneous electromyography (EMG) monitoring may prevent permanent motor deficit and enhance the postoperative outcomes.

Factors Affecting Transcranial Motor-Evoked Potential Measurements Using Single-Train Stimulation with an Increased Number of Pulses during Adolescent Scoliosis Surgery: A Prospective Observational Study.

Measurement of transcranial motor-evoked potentials (TcMEPs) during scoliosis surgery helps detect postoperative new neurological defects. However, TcMEP interpretation is difficult owing to the influence of intraoperative physiological, pharmacological, and time-related factors as well as stimulation conditions. In this study, we aimed to investigate the effect of the abovementioned factors on TcMEP amplitude using single-train stimulation with an increased number of pulses (STS-INP) during adolescent scoliosis surgery; moreover, we evaluated the complications of TcMEP measurement. We included 50 patients and 706 TcMEP measurements. A total of 1412 TcMEP waveforms were analyzed, each on the bilateral abductor pollicis brevis, tibialis anterior, and abductor hallucis muscles. We estimated the mean difference (95% confidence interval (CI)) and predicted mean difference (95% CI) evaluated using the interquartile range of each factor, based on a mixed-effect model with random intercepts for TcMEP amplitude. The predicted mean differences in TcMEP amplitude were clinically small compared with the actual TcMEP amplitude, suggesting that each factor had a limited effect on TcMEP amplitude. No intraoperative bite injuries or seizures were observed. Using STS-INP during adolescent scoliosis surgery may enable accurate measurement of TcMEP amplitude with neither complications nor the influence of various intraoperative factors.

Usefulness of the H-Reflex for Intraoperative Monitoring of Thoracoabdominal Aneurysms.

Intraoperative neurophysiologic monitoring in thoracoabdominal aneurysms (TAAA) is essential to avoid intraoperative spinal cord injury). Motor and somatosensory evoked potentials may be considered intraoperative tools for detecting spinal cord injury. H-reflex is a well-known neurophysiologic technique to evaluate L5-S1 root. Current evidence supports the observation that H-reflex changes may occur with spinal cord damage as high as the cervical level. This study aimed to evaluate the usefulness of the H-reflex in these surgeries. The use of intraoperative H-reflex in TAAA monitoring was evaluated in 12 patients undergoing open or endovascular repair of TAAA for a period of four years (2016-2020) using somatosensory evoked potentials (SSEPs) and transcranial motor evoked potentials (TcMEPs) and bilateral H-reflex. Six neurophysiologic alarms were recorded in five of the 12 patients. Summarizing the neurophysiologic changes of our series, we considered a peripheral change when we detected a unilateral loss of SSEPs, TcMEPs, and H-reflex. Instead, we assumed a central change when we detected a unilateral or bilateral loss of TcMEPs and H-reflex with normal SSEPs, which we considered a sign of spinal cord ischemia. Interestingly H-reflex always changed significantly in combination with TcMEPs in the same fashion. According to our series, H-reflex can detect intraoperative changes with the same sensitivity as TcMEPs in TAAA surgeries. With the support of other techniques, it can be useful to localize the origin of the lesion (peripheral or central spinal cord), to help in surgical decision-making to avoid postoperative neurologic damage. Based on our results, we recommend the systematic use of H-reflex in TAAA surgeries.

Failure of Sequential Compression Device Detected by Neuromonitoring during Minimally Invasive Posterior Scoliosis Surgery

AbstractIntraoperative neuromonitoring is recommended as standard practice for corrective scoliosis surgery. Common methods include somatosensory-evoked potentials (SSEPs) and transcranial motor-evoked potentials (TcMEPs), which have been shown to have a high diagnostic accuracy in detecting new neurological deficits postoperatively. Sequential compression devices (SCDs) are a common method for thromboprophylaxis in spine surgery and are not known to have many device-related complications. To date, there have been no reports of lower extremity ischemia secondary to SCD deflation failure detected by multimodality neuromonitoring during minimally invasive posterior spine surgery. We, therefore, present a case report of an 18-year-old male with adolescent idiopathic scoliosis who underwent minimally invasive posterior spinal fusion with instrumentation. Intraoperative decrease in SSEPs and TcMEPs were noted in the left leg shortly after incision before any instrumentation or reduction occurred. Further examination revealed that the left leg was hypoperfused compared with the right leg and that the left SCD was not properly deflating. Bilateral SCDs were removed, and perfusion and neuromonitoring returned to baseline immediately. Bilateral SCDs and the machine were replaced, and neuromonitoring remained within normal limits for the rest of the surgery. The patient had no postoperative neurologic or vascular deficits. Early detection of lower extremity ischemia by neuromonitoring resulted in the prompt identification and addressing of SCD malfunction, sparing devastating neurological and vascular injury to the patient's leg. This case reinforces the importance of neuromonitoring within spine surgery.

Motor Evoked Potential

Motor evoked potential(MEP)is the most widely used intraoperative neurophysiological monitoring measure. It includes cortical direct stimulation MEP(dMEP), which directly stimulates the primary motor cortex of the frontal lobe identified by short-latency somatosensory evoked potentials, and transcranial MEP(tcMEP), which involves high-current or high-voltage transcranial stimulation using cork-screw electrodes installed in the scalp. dMEP is performed in brain tumor surgery close to the motor area. tcMEP is simple, safe, and widely used in spinal and cerebral aneurysm surgeries. The increase in sensitivity and specificity with compound muscle action potential(CMAP)after peripheral nerve stimulation normalization performed in MEP to remove the effect of muscle relaxants is unclear. However, tcMEP for decompression in compressive spinal and spinal nerve diseases may predict the recovery of postoperative neurological symptoms with CMAP normalization. The anesthetic fade phenomenon can be avoided with CMAP normalization. The cutoff rate of loss of amplitude that causes postoperative motor paralysis in intraoperative MEP monitoring is 70%-80%, and setting an alarm at each facility based on this is necessary.

Transcranial Motor Evoked Potentials as a Predictive Modality for Postoperative Deficit in Cervical Spine Surgery – A Meta-analysis (P6-4.006)

<h3>Objective:</h3> To evaluate whether intraoperative transcranial motor evoked potential (TcMEP) changes can predict postoperative neurologic complications in patients undergoing cervical spine surgery. <h3>Background:</h3> Cervical decompression and fusion surgeries are commonly performed to relieve spinal cord and nerve root impingement. Potential intraoperative injury to the spinal cord and nerve roots poses a nontrivial risk for consequent postoperative deficits. Although neuromonitoring with intraoperative TcMEPs is often used in cervical spine surgery, its therapeutic value remains controversial. <h3>Design/Methods:</h3> A meta-analysis of the literature using PubMed to retrieve literature on intraoperative TcMEP monitoring during cervical spine surgery, excluding aneurysms, tumors, and trauma, was performed. Data collection included study design, patient demographics, procedure type/approach/indication, modalities used, TcMEP alarm criteria, TcMEP changes (including reversible and irreversible changes), and postoperative neurological deficit. The sensitivity, specificity, and diagnostic odds ratio (DOR) of overall, reversible, and irreversible TcMEP changes for predicting postoperative neurological deficit were calculated. <h3>Results:</h3> Nineteen studies were included in the final analysis. The total cohort consisted of 45,367 patients, and the incidence of postoperative neurological deficits was 0.37% (168/45367). Of the total cohort, 1.36% (619/45367) had a significant intraoperative TcMEP change. The incidence of postoperative neurological deficits in patients with intraoperative TcMEP changes was 15.67% (97/619), while the incidence in those without was 0.16% (71/44677). TcMEP changes had a sensitivity of 59%, specificity of 95%, and DOR of 26.92 for predicting neurologic deficit. Reversible and irreversible changes had sensitivities of 17% and 47%, specificities of 95% and 98%, and DORs of 3.02 and 56.29, respectively. <h3>Conclusions:</h3> TcMEP monitoring has high specificity but low sensitivity for predicting deficits in cervical spine surgery. Patients with postoperative deficits were 27 times more likely to have experienced intraoperative TcMEP changes than those without deficits, with irreversible changes indicating a higher risk of injury than reversible changes. <b>Disclosure:</b> Mr. Reddy has nothing to disclose. Dr. Gorijala has nothing to disclose. Mr. Chang has nothing to disclose. Dr. Anetakis has nothing to disclose. Jeffery Balzer has nothing to disclose. Donald Crammond has nothing to disclose. Dr. Shandal has nothing to disclose. Dr. Lee has nothing to disclose. The institution of Dr. Shaw has received research support from LSRS. The institution of Dr. Shaw has received research support from CSRS. The institution of Dr. Shaw has received research support from AO Spine. Dr. Shaw has received intellectual property interests from a discovery or technology relating to health care. The institution of Dr. Thirumala has received research support from University of Pittsburgh.

Upper extremity neuromonitoring changes are more common than lower extremity during spinal fusion for Scheuermann's kyphosis.

The purpose of this study is to determine the incidence of intraoperative neuromonitoring (IONM) changes and postoperative neurologic deficit in patients with Scheuermann's Kyphosis (SK) undergoing posterior spinal fusion (PSF). Single-center, retrospective chart review of the clinical, surgical and IONM data (somatosensory evoked potential (SSEP) and neurogenic motor evoked potential (NMEP) or transcranial motor evoked potential (TcMEP)) from patients with SK undergoing PSF at our center from 1993 to 2021. One hundred and four SK patients (mean 16.4 ± 1.9years) underwent PSF with correction of kyphosis from mean 79.4 ± 10.8° to 35.4 ± 13.9°. MEP data were obtained using either NMEP in 34.6% of patients) or TcMEP in 65.4% of patients. Only 3.8% of cases had lower extremity (LE) IONM changes during surgery, with no postoperative neurologic deficits in those patients. IONM changes occurred more frequently in the upper extremities (UE) with 14 (13.4%) patients having changes in UE SSEPs. Patients with UE IONM changes had significantly longer surgical times (p = 0.0096) and higher number of levels fused (p = 0.003) compared to patients without changes. Their weight, but not BMI, was also significantly higher (p = 0.036). These UE IONM changes resolved with arm repositioning in all but one patient who had a postoperative UE neurapraxia that resolved by 6weeks. There was 1 postoperative transient femoral nerve palsy without IONM changes thought to be due to patient positioning. The incidence of critical LE IONM changes during PSF for SK is 3.4%, which is similar to that reported in AIS. UE IONM changes are significantly more common at 13.4%, revealing that these patients are vulnerable to malpositioning of the arms during surgery.