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Introduction: Intraoperative neuromonitoring (IOM) of motor/somatosensory evoked potentials is a well-established approach for reducing ischemic complications after aneurysm clipping. Research question: To determine the predictive validity of IOM for postoperative functional outcome and its perceived added value for intraoperative real-time feedback of functional impairment in the surgical treatment of unruptured intracranial aneurysms (UIAs). Material and methods: Prospective study of patients scheduled for elective clipping of UIAs between 02/2019–02/2021. Transcranial motor evoked potentials (tcMEP) were used in all cases, a significant decline was defined as loss of ≥50% in amplitude or 50% latency increase. Clinical data were correlated to postoperative deficits. A surgeon's questionnaire was conceived. Results: 47 patients were included, median age 57 years (range 26–76). IOM was successful in all cases. In 87.2%, IOM was stable throughout surgery, although 1 patient (2.4%) demonstrated a permanent postoperative neurological deficit. All patients with an intraoperatively reversible tcMEP-decline (12.7%) showed no surgery-related deficit, regardless of the decline duration (range 0.5–40.0 ​min; mean: 13.8). Temporary clipping (TC) was performed in 12 cases (25.5%), with a decline in amplitude in 4 patients. After clip-removal, all amplitudes returned to baseline. IOM provided the surgeon with a higher sense of security in 63.8%. Discussion and conclusion: IOM remains invaluable during elective microsurgical clipping, particularly during TC of MCA and AcomA-aneurysms. It alerts the surgeon of impending ischemic injury and offers a way of maximizing the time frame for TC. IOM has highly increased surgeons’ subjective feeling of security during the procedure.

Objectives: Motor evoked potential (MEP) monitoring is a reliable method for real-time assessment of corticospinal tract integrity. However, the potential benefits of MEP monitoring during degenerative spine surgery remain controversial. This study aims to determine the role of MEP monitoring during surgery for cervical spondylotic myelopathy (CSM) in prediction of prognosis., Methods: Transcranial electrical stimulation was performed to elicit MEPs during dorsal decompression for the treatment of CSM. MEP-threshold levels were assessed separately at the beginning and end of the surgery in upper extremity muscles corresponding to nerve roots at the level of/distal to the decompression site. Clinical outcome was measured using the modified Japanese Orthopedic Association score (mJOA)., Results: The study included 47 patients. 31 patients (66 %) showed improvements in neurological function at discharge. A measurable improvement in the majority of tested muscles, or in at least one muscle group, in a given patient highly correlated with mJOA score increase at discharge (p < 0.001) with an odds ratio of 10.3 (CI:2.6-34.4) and 11.4 (CI:2.8-41.3), respectively. Conversely, MEP deterioration was not associated with worse clinical outcome, nor was it predictive of failure to recover., Conclusion: MEP improvement during CSM surgery seems to be highly predictive of early postoperative neurological recovery and could indicate subclinically enhanced signal conduction. This highlights the potential of MEP monitoring as an intraoperative, real-time predictive tool for clinical recovery after decompression in patients with CSM., Competing Interests: Declaration of competing interest None to declare., (Copyright © 2024 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

Objective: D-wave can safely monitor the corticospinal-tract (CST)-function regarding gross-motor outcome of lower extremities, but it is still unknown whether i)D-wave can also safely monitor the gross-motor outcome of distal upper extremities in those patients undergoing high-cervical intramedullary-spinal-cord-tumor (IMSCT)-resection (enabling epidural D-wave-placement below C5) and ii)multimodal IONM can also predict fine-motor/complex hand function., Methods: We prospectively assessed 20 patients undergoing IMSCT-surgery above the C4/5-level with multimodal IONM (D-wave/mMEPs/EMG/SSEPs). Detailed gross-/fine-motor and complex hand function was assessed pre- and postoperatively and during long-term follow-up (mean:29.5 ± 18.8 months) and correlated with IONM-findings., Results: D-wave monitoring was without intraoperative critical changes in all patients and none had any permanent postoperative gross-motor deficits. However, D-wave did not allow to predict the occurrence of mild permanent postoperative deficits affecting fine-motor function which was the case in 8% for distal upper extremities. The complex distal upper extremities' function assessed by Nine-Hole-Peg-Test (reflecting the complex motor/sensory interaction for hand-usability) was permanently deteriorated in 15% postoperatively and only the combination of D-wave/mMEPs/EMG/SSEPs was able to provide a viable predictive power (specificity:79%/sensitivity:43%)., Conclusions: In high-cervical IMSCT-surgery, unimpaired D-wave reliably predicts preserved gross-motor function, but fails to sufficiently cover distal upper extremities' fine-motor/complex function., Significance: Our study underlines the importance of multimodal IONM for fine-motor/complex hand function., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objectives: To report the clinical and electrophysiological findings in two patients with multifocal motor neuropathy (MMN) and bilateral absent patellar and Achilles tendon reflexes despite normal strength of quadriceps and calf muscles. Methods: The medical history and clinical evaluation were completed by electrophysiological tests: sensory and motor nerve conduction studies, needle electromyography, motor-evoked potentials (MEPs) after transcranial magnetic stimulation, patellar T (tendon) responses, quadriceps and soleus H (Hoffman) reflex recordings. Results: In the two patients, history, clinical evaluation, nerve conduction studies, favorable response to intravenous immunoglobulins, and positive anti-GM1 antibodies fulfilled the diagnosis of MMN. The lower limbs were asymptomatic, except for a unilateral weakness of foot dorsiflexion. The patellar and Achilles tendon reflexes disappeared during the course of the disease. The sensory nerve conduction studies were normal or minimally modified, M-wave and MEP/M amplitude ratio to the quadriceps were normal, patellar T (tendon) responses were virtually absent, and H-reflex to the quadriceps and soleus muscles were absent. Conclusions: These observations, which show the interruption of the reflex afferent pathway, raise the question of Ia afferent involvement in the lower limbs of these two patients with MMN. Further investigations should determine the frequency and significance of these findings in this disorder.

Objectives: Target localization for deep brain stimulation (DBS) is a crucial step that influences the clinical benefit of the DBS procedure together with the reduction of side effects. In this work, we address the feasibility of DBS target localization in the globus pallidus internus (GPi) aided by intraoperative motor evoked potentials (MEP) with emphasis on the reduction of capsular side effects., Material and Methods: Micro-macroelectrode recordings were performed intraoperatively on 20 patients that underwent DBS treatment of the GPi (GPi-DBS). MEP were elicited intraoperatively by microelectrode stimulation during stereotactic DBS surgery. We studied the relationship between MEP thresholds and the internal capsule (IC) proximity., Results: We found a significant correlation between intraoperative MEP thresholds and IC proximity., Conclusions: We provide further evidence of the role of MEPs for DBS target localization in the GPi, which extends and confirms the usefulness of MEPs as previously reported by DBS target localization studies dealing with the subthalamic and thalamic nuclei. Our approach is advantageous in that it provides criteria to determine the DBS target without the need to rely on a patient's response while avoiding capsular effects., Competing Interests: Declaration of competing interest CT reports no conflict of interest. PN received travel expenses from Abbott Medical and Boston Scientific, manufacturers of DBS devices. PJS received speaker honoraria and travel reimbursement from Abbott Medical. JV received consultant fees and/or travel grants and/or research grants from Abbott, Boston Scientific, Medtronic, UniQure. AS reports grants from German Research Council; personal fees from Medtronic Inc., Boston Scientific, Abbott Medical, UCB, and Teva Pharma. SJG received honoraria and/or travel expenses from Abbott Medical, Boston Scientific, Inomed and Medtronic., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Transcranial direct current stimulation (tDCS) is used to modulate neuronal activity, but the exact mechanism of action (MOA) is unclear. This study investigates tDCS-induced modulation of the corticospinal excitability and the underlying MOA. By anesthetizing the scalp before applying tDCS and by stimulating the cheeks, we investigated whether stimulation of peripheral and/or cranial nerves contributes to the effects of tDCS on corticospinal excitability., Materials and Methods: In a randomized cross-over study, four experimental conditions with anodal direct current stimulation were compared in 19 healthy volunteers: 1) tDCS over the motor cortex (tDCS-MI), 2) tDCS over the motor cortex with a locally applied topical anesthetic (TA) on the scalp (tDCS-MI + TA), 3) DCS over the cheek region (DCS-C), and 4) sham tDCS over the motor cortex(sham). tDCS was applied for 20 minutes at 1 mA. Motor evoked potentials (MEPs) were measured before tDCS and immediately, 15, 30, 45, and 60 minutes after tDCS. A questionnaire was used to assess the tolerability of tDCS., Results: A significant MEP amplitude increase compared with baseline was found 30 minutes after tDCS-MI, an effect still observed 60 minutes later; no time∗condition interaction effect was detected. In the other three conditions (tDCS-MI + TA, DCS-C, sham), no significant MEP modulation was found. The questionnaire indicated that side effects are significantly lower when the local anesthetic was applied before stimulation than in the other three conditions., Conclusions: The significant MEP amplitude increase observed from 30 minutes on after tDCS-MI supports the modulatory effect of tDCS on corticospinal neurotransmission. This effect lasted one hour after stimulation. The absence of a significant modulation when a local anesthetic was applied suggests that effects of tDCS are not solely established through direct cortical stimulation but that stimulation of peripheral and/or cranial nerves also might contribute to tDCS-induced modulation., Competing Interests: Conflict of Interest Emma Lescrauwaet, Ann Mertens, Chloé Algoet, Evelien Carrette, and Robrecht Raedt reported no conflict of interest. Debby Klooster was supported by a FWO junior postdoctoral grant (1259121N). Mathieu Sprengers, Steven Beumer, and Rob Mestrom were partially funded by the Dutch PPP Allowance made available by Health Holland, Top Sector Life Sciences & Health, to EpilepsieNL. Kristl Vonck obtained a Bijzonder Onderzoeks Fonds (BOF) grant of Ghent University for the purchase of transcranial magnetic stimulation (TMS) equipment, obtained consultancy fees from LivaNova, Synergia Medical, All Man Foundation, Precisis, and Angelini Pharma and participates in the advisory board of LivaNova, Synergia Medical, Precisis, and Angelini Pharma. Paul Boon obtained a BOF grant of Ghent University for the purchase of TMS equipment, obtained consultancy fees from LivaNova, Medtronic, and Angelini Pharma and participates in the advisory board of LivaNova, Synergia Medical, and Medtronic., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Objective: Tetanic stimulation of a peripheral nerve prior to transcranial electrical stimulation (TES) may enhance motor evoked potential (MEP) amplitudes. The purpose of this study was to investigate the post-tetanic MEP (p-MEP) technique in improving MEP amplitudes., Methods: Conventional TES MEPs (c-MEP) and p-MEPs with left upper limb stimulation (p-MEP UL ) or left lower limb stimulation (p-MEP LL ) were performed in 26 patients. Bilateral hand and foot MEP amplitudes obtained with each protocol were compared. Subgroup comparisons were performed for myelopathy and peripheral neuropathy patients. Within-subject amplitude differences between c-MEP and each p-MEP technique were compared using a Wilcoxon test., Results: The mean age of the patients was 52.7 years (range, 12-79 years). Overall, p-MEP UL resulted in MEP improvement in 25 of 26 (96%) patients, and p-MEP LL improved MEPs in 19 of 26 (73%) patients. The increase in MEP amplitudes were statistically significant in all muscle groups except left foot. Similar improvements were seen in the myelopathy group; in the neuropathy group, p-MEP UL produced similar results, but p-MEP LL did not., Conclusions: The p-MEP technique can improve MEP amplitudes, including in patients with myelopathy. In patients with peripheral neuropathy, the results were mixed., Significance: Tetanic stimulation can enhance intraoperative MEP amplitudes., (Published by Elsevier B.V.)

Competing Interests: The authors declare that they have no conflicts of interest.

Background: Postoperative hemiparesis following frontal lobe lesion resection is alarming, and predicting motor function recovery is challenging. Supplementary motor area (SMA) syndrome following resection of frontal lobe lesions is often indistinguishable from postoperative motor deficit due to surgical injury of motor tracts. We aimed to describe the use of intraoperative transcranial electrical stimulation (TES) with motor evoked potential monitoring data as a diagnostic tool to distinguish between SMA syndrome and permanent motor deficit (PMD)., Methods: A retrospective analysis of 235 patients undergoing craniotomy and resection with TES-MEP monitoring for a frontal lobe lesion was performed. Patients who developed immediate postoperative motor deficit were included. Motor deficit and TES-MEP findings were categorized by muscle group as left upper extremity, left lower extremity, right upper extremity, or right lower extremity. Statistical analysis was performed to determine the predictive value of stable TES-MEP for SMA syndrome versus PMD., Results: This study included 20 patients comprising 29 cases of immediate postoperative motor deficit by muscle group. Of these, 27 cases resolved and were diagnosed as SMA syndrome, and 2 cases progressed to PMD. TES-MEP stability was significantly associated with diagnosis of SMA syndrome (P = 0.015). TES-MEP showed excellent diagnostic utility with a sensitivity and positive predictive value of 100% and 92.6%, respectively. Negative predictive value was 100%., Conclusions: Temporary SMA syndrome is difficult to distinguish from PMD immediately postoperatively. TES-MEP may be a useful intraoperative adjunct that may aid in distinguishing SMA syndrome from PMD secondary to surgical injury., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Temporal predictability and intensity of an impending nociceptive input both shape pain experience and modulate laser-evoked potentials (LEPs) amplitude. However, it remains unclear whether and how these two factors could influence pain-induced corticospinal excitability modulation. The current study investigated the influence of nociceptive stimulation intensity and temporal predictability on motor-evoked potentials (MEPs) modulation, in parallel to their effect on pain perception and LEPs amplitude. Twenty participants completed electroencephalographic and transcranial magnetic stimulation experiments during which two laser nociceptive stimulation intensities (high and low) were either unpredictably delivered (random delay) or preceded by a fixed-timing cue (fixed delay). The amplitude of the conditioned MEPs was significantly reduced only for the high nociceptive stimulation and was not affected by the temporal predictability of pain (despite the fact that temporal predictability modulated the amplitude of P2 LEP component amplitude). However, a posteriori analyses based on patterns of pain-induced MEPs modulation revealed that participants in which nociceptive stimulation resulted in an increase in corticospinal excitability were more affected by the predictability of pain (i.e. increasing corticospinal excitability even more when pain occurrence was predictable), regardless of the nociceptive stimulation intensity; whereas participants in which nociceptive stimulation resulted in a decrease in corticospinal excitability were sensitive to the intensity of the stimulation but not its predictability. These results suggest a potential influence of cognitive factors such as temporal predictability on the response of the motor system in the presence of pain for some participants, contributing to explain, at least in part, the high variability highlighted in a number of previous studies.

Objectives: Central neuropathic pain (CNP) is associated with altered corticomotor excitability (CE), which can potentially provide insights into its mechanisms. The objective of this study is to describe the CE changes that are specifically related to CNP., Methods: We evaluated CNP associated with brain injury after stroke or spinal cord injury (SCI) due to neuromyelitis optica through a battery of CE measurements and comprehensive pain, neurological, functional, and quality of life assessments. CNP was compared to two groups of patients with the same disease: i. with non-neuropathic pain and ii. without chronic pain, matched by sex and lesion location., Results: We included 163 patients (stroke=93; SCI=70: 74 had CNP, 43 had non-neuropathic pain, and 46 were pain-free). Stroke patients with CNP had lower motor evoked potential (MEP) in both affected and unaffected hemispheres compared to non- neuropathic pain and no-pain patients. Patients with CNP had lower amplitudes of MEPs (366 μV ±464 μV) than non-neuropathic (478 ±489) and no-pain (765 μV ± 880 μV) patients, p < 0.001. Short-interval intracortical inhibition (SICI) was defective (less inhibited) in patients with CNP (2.6±11.6) compared to no-pain (0.8±0.7), p = 0.021. MEPs negatively correlated with mechanical and cold-induced allodynia. Furthermore, classifying patients' results according to normative data revealed that at least 75% of patients had abnormalities in some CE parameters and confirmed MEP findings based on group analyses., Discussion: CNP is associated with decreased MEPs and SICI compared to non-neuropathic pain and no-pain patients. Corticomotor excitability changes may be helpful as neurophysiological markers of the development and persistence of pain after CNS injury, as they are likely to provide insights into global CE plasticity changes occurring after CNS lesions associated with CNP., Competing Interests: Declaration of Competing Interest The authors report no conflict of interest or disclosures relevant to the manuscript., (Copyright © 2023 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

Background: The critical role of different adjuncts in improving the neurological outcome in intrinsic brain lesions affecting eloquent areas is demonstrated by their more diffuse utilization. Neurosurgeons often rely on preoperative and intraoperative diffusion tensor imaging tractography to improve the operative strategy and prognosis. We aimed to identify and validate a diffusion tensor imaging-based classification considering the relationship between the brain lesion and the corticospinal tract to predict a >50% reduction of motor evoked potentials (MEPs) during surgical excision of lesions involving the motor pathways., Methods: We included patients consecutively enrolled at our institution between April 2020 and September 2022 with 3 patterns of increasing complexity according to the relationship between the lesion and the corticospinal tract as identified on preoperative diffusion tensor imaging. Outcome measures were >50% reduction in intraoperative MEPs and neurological outcome defined as unchanged, improved, or worsened., Results: The study included 83 patients. A statistically significant linear trend between higher rates of reduction of MEPs and higher classification grades was observed (P = 0.001), with sensitivity 0.60, specificity 0.88, accuracy 0.83, and area under the curve 0.75. Higher grades were associated with worse neurological outcomes (P = 0.02)., Conclusions: The classification proved reliable in anticipating reduction in intraoperative MEPs and in predicting neurological outcome. Using this classification in patients undergoing surgery for lesions involving the motor pathways could help in counseling the patient, surgical planning, enhancing teamwork of operating room personnel, and improving the patient's prognosis., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Objectives: The purpose of this study was to determine the effect of common transcranial magnetic stimulation (TMS) waveforms (monophasic and biphasic) on resting motor threshold (RMT), active motor threshold (AMT), and motor evoked potential (MEP) amplitudes in the biceps and first dorsal interosseous (FDI) because waveforms may affect motor targets differently. We also determined test-retest reliability., Methods: Ten individuals participated in two sessions of TMS delivered to the motor cortex. Monophasic stimulation to induce a posterior-anterior current in the brain (mono PA ) and biphasic posterior-anterior then anterior-posterior (bi PA-AP ) were applied in each session in random order. In each session, there were four blocks of measurements (2 muscles × 2 waveforms) of RMT, AMT and MEPs at the hotspot location. MEPs were normalized to the maximum EMG signal., Results: RMTs and AMTs were lower for mono PA compared to bi PA-AP stimulation for the biceps (p<0.01) and FDI (p<0.01). Normalized MEPs were greater for mono PA compared to bi PA-AP stimulation in the FDI (p=0.01) and not different in the biceps (p=0.86). Motor thresholds were not different between sessions suggesting high reliability (p<0.01). Normalized MEPs had very low reliability across sessions in the FDI, and moderate reliability in the biceps., Discussion: Preliminary investigation suggests the effect of TMS waveform on motor thresholds is similar in upper limb proximal and distal muscles, but the effect differs per motor target for MEPs. Further, test-retest reliability of waveform effects was sensitive to target muscle. These findings may contribute to improve the efficacy and reliability of TMS for clinical use., Competing Interests: Conflict of Interest The authors have no conflict of interest related to this study to declare., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

Objective: During neurosurgical procedures, strip electrodes should have low impedance and sufficient adherence on the brain surface. We evaluated the signal quality, safety, and performance of a novel strip electrode (WISE Cortical Strip, WCS®), with conductive electrode contacts created with platinum nanoparticles embedded in a polymer base., Methods: In a multicenter interventional, non-inferiority study, we compared WCS to a conventional strip electrode (Ad-Tech). We recorded impedance and somatosensory evoked potentials (SEP) and determined the signal-to-noise ratio (SNR). We performed direct stimulation of the motor cortex. An external clinical event committee rated safety and adverse events and users rated usability., Results: During 32 brain surgeries in the paracentral region, WCS was rated safe and effective in signal transmission. Two seizure events were classified as probably related to the stimulation with WCS. The users rated WCS adhesion to the brain as satisfactory but reported difficulties sliding the WCS under the dura. The median (IQR) impedance of WCS was lower than for Ad-Tech: 2.7 (2.3-3.7) vs 5.30 (4.3-6.6) kΩ (p < 0.005). The SNR of SEP was non-inferior for WCS compared to Ad-Tech., Conclusions: The impedance of WCS was lower than Ad-Tech without safety limitations. In small craniotomies not exposing the motor cortex its use may be limited., Significance: Low impedance electrodes facilitate recordings with high SNR., Competing Interests: Conflict of interest None of the authors have potential conflicts of interest to be disclosed. All authors declare that they participated in the study without receiving personal compensation. AS, KS, JS are members of the IOM board of inomed Medizintechnik GmbH and have received speaker honoraria. MCN has reviewed documentation for WISE and his institution has received research funds from WISE Srl., (Copyright © 2022 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objective: To determine the electrodiagnostic characteristics of facial onset sensory and motor neuronopathy (FOSMN)., Methods: Electrophysiological data from 10 FOSMN patients in Newcastle-upon-Tyne and Sydney were reviewed. Relevant literature was reviewed., Results: Findings on standard electrophysiological assessment were in broad agreement with those published: blink reflexes were abnormal in all but one patient; sensory nerve action potentials were reduced but compound muscle action potentials preserved; mixed acute and chronic neurogenic change was identified on needle electromyography in bulbar and cervico-thoracic muscles in approximately 50% of patients. Upper limb somatosensory evoked potential (SEP) central conduction times were increased (n = 4) and progressed on repeat testing (n = 3). Upper motor neuron dysfunction was revealed by several measures [ipsilateral motor evoked potentials (MEPs) (n = 1); reduced short interval intra-cortical inhibition on threshold-tracking transcranial magnetic stimulation (n = 2); absent beta-band intermuscular coherence (n = 3)]., Conclusions: Electrodiagnostic investigation of FOSMN should include blink reflex testing, SEPs and tests of upper motor neuron function. The combination of progressive lower motor neuron disease and upper motor neuron disease on neurophysiological investigation provides further support for the contention that FOSMN is a rare variant of motor neurone disease., Significance: These findings will aid the neurologist and neurophysiologist in making a confident diagnosis of FOSMN, thus expediting appropriate care., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Introduction: Accuracy is crucial in Deep Brain Stimulation (DBS). Electrophysiological and image-based techniques are used to avoid suboptimal positioning. Macrostimulation is the gold standard to delineate the therapeutic window intraoperatively. Despite this, electrode revision rates due to malpositioning are as high as 17%. The goal was to compare motor evoked potentials (MEPs) with the gold standard of Macrostimulation. We assessed accuracy and precision as well as the correlation in predicting motor side effects at the initial mapping 4 weeks postoperatively., Methods: In this prospective study intraoperative MEPs from 94 contacts in 16 patients undergoing STN DBS under local anesthesia were correlated to the postoperative threshold for stimulation-induced motor side effects and compared to intraoperative Macrostimulation. Analysis of accuracy, precision and correlation (Pearson) was performed., Results: MEPs of the upper extremity had a mean percentage error of 25% (SD 38.8%) and correlated significantly with the motor threshold at postoperative mapping (R=0.235). Macrostimulation was less accurate and precise with a mean percentage error of - 68% (SD 78.8%) but had a higher correlation (R=0.388). MEPs rarely (3%) overestimated the threshold by maximally 1 mA. In contrast, Macrostimulation overestimated the threshold by over 1 mA in 69% leading to a false sense of security., Conclusion: MEPs are feasible in an awake setting during Deep Brain Stimulation in the STN for PD patients. MEPs of the upper extremity are more accurate and precise predicting the motor threshold and avoid a false sense of security in comparison to the gold standard of Macrostimulation., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Objective: An increase in the latency of a motor evoked potential might be as significant as a decrease in amplitude to predict a significant and clinically symptomatic neurological injury in spinal surgery for adolescent idiopathic scoliosis. The aim of the study was to investigate the impact of monitoring of latency of motor evoked potentials during spinal surgery for adolescent idiopathic scoliosis by describing intraoperative data., Methods: Preoperative recordings of 50 patients undergoing posterior spinal fusion for idiopathic scoliosis were studied. Latencies of appearance of the motor evoked potential curves on the right and left side were recorded for each group of muscles at several key moments during the procedure (basal, before the first implant, before and after corrective maneuvers)., Results: Mean latencies were approximately the same in each muscle group on the right and the left side, before and after correction. There was no significant increase in latency during surgery. Overall results showed that the measured latency did not differ significantly between the two age groups (p=0.07). Negative correlation between height and the means of latencies was recorded in the abductor pollicis brevis and abductor digiti minimi (r=0.4; p=0.009), rectus femoris (r=0.4; p=0.01), tibialis anterior (r=0.4; p=0.007), and abductor hallucis (r=0.5; p=0.0004). No significant correlation was found between age and intraoperative parameters., Conclusion: Intraoperative latency could be a reliable intraoperative monitoring criteria with low variability, that might be used to predict postoperative motor deficits in surgery for adolescent idiopathic scoliosis., Competing Interests: Declaration of Competing Interest The authors declare that their search was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

Objectives: One of the main challenges posed by the surgical deep brain stimulation (DBS) procedure is the successful targeting of the structures of interest and avoidance of side effects, especially in asleep surgery. Here, intraoperative motor evoked potentials (MEPs) might serve as tool to identify the pyramidal tract. We hypothesized that intraoperative MEPs are useful to define the distance to the pyramidal tract and reduce the occurrence of postoperative capsular side effects., Materials and Methods: Motor potentials were evoked through both microelectrode and DBS-electrode stimulation during stereotactic DBS surgery on 25 subthalamic nuclei and 3 ventral intermediate thalamic nuclei. Internal capsule proximity was calculated for contacts on microelectrode trajectories, as well as for DBS-electrodes, and correlated with the corresponding MEP thresholds. Moreover, the predictivity of intraoperative MEP thresholds on the probability of postoperative capsular side effects was calculated., Results: Intraoperative MEPs thresholds correlated significantly with internal capsule proximity, regardless of the stimulation source. Furthermore, MEPs thresholds were highly accurate to exclude the occurrence of postoperative capsular side effects., Conclusions: Intraoperative MEPs provide additional targeting guidance, especially in asleep DBS surgery, where clinical value of microelectrode recordings and test stimulation may be limited. As this technique can exclude future capsular side effects, it can directly be translated into clinical practice., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Objectives: To assess the accuracy of intraoperative neurophysiological monitoring (IONM) in predicting immediate and 3-month postoperative neurological new deficit (or deterioration) in patients benefiting from spinal cord (SC) surgery; and to identify factors associated with a higher risk of postoperative clinical worsening., Methods: Consecutive patients who underwent SC surgery with IONM were included. Pre and postoperative clinical (modified McCormick scale), radiological (lesion-occupying area ratio), and electrophysiological features were collected., Results: A total of 99 patients were included: 14 (14.1%) underwent extradural surgery, 50 (50.5%) intradural extramedullary surgery, and 35 (35.4%) intramedullary surgery. Cumulatively, multimodal IONM (motor and somatosensory evoked potentials, D-wave whenever possible) significantly predicted postoperative deficits (p<0.001), with a sensitivity, specificity, positive predictive value, and negative predictive value of 0.81, 0.93, 0.83, and 0.92, respectively. Sixty (60.6%) patients displayed no IONM change, whereas 39 (39.4%) displayed IONM worsening. In multivariate analysis, predictors for postoperative clinical worsening were: abnormal preoperative electrophysiological assessment (p=0.03), intramedullary tumor (p<0.001), lesion-occupying area ratio ≥0.7 (p<0.001), and IONM alterations (p<0.001). Three months after the surgical procedure, in patients presenting at least one of the risk factors described above, 45/81 (55.6%) and 19/81 (23.5%) were clinically and electrophysiologically improved, respectively; while 13/81 (16.0%) and 10/81 (12.3%) were clinically and electrophysiologically worsened., Conclusion: Multimodal IONM is an essential tool to guide SC surgery, and enables the accurate prediction of postoperative neurological outcome. Specific attention should be given to patients presenting with preoperative electrophysiological abnormalities, large tumor volume, and intramedullary tumor location., Competing Interests: Conflict of Interest None., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

Objectives: Despite the introduction of several adjuncts to improve spinal perfusion, spinal cord ischemia (SCI) remains a devastating complication of thoracoabdominal aortic aneurysm (TAAA) repair. Our aim was to assess the effects on clinical outcome of interventions triggered by motor evoked potentials (MEP) alerts. Furthermore, we want to assess whether a multimodal intraoperative neurophysiologic monitoring (IONM) protocol is helpful for stratifying patients according to the risk of SCI at the end of the vascular phase of surgery., Methods: We prospectively studied one-hundred consecutive patients who underwent TAAA repair. We applied a multimodal IONM including MEP, somatosensory evoked potentials (SEP) and peripheral nerve monitoring techniques. Signal deteriorations were classified as reversible/irreversible according to whether they recovered or not at the end of monitoring (EOM), set at the end of the vascular phase of surgery. Significant MEP changes drove a series of corrective measures aimed to improve spinal perfusion., Results: The rate of immediate postoperative motor deficits consistent with SCI was significantly higher with irreversible MEP deteriorations compared to reversible ones. The interpretation of MEP findings at the EOM led to the development of risk categories for SCI, based on the association between MEP results and motor outcome., Conclusions: Our data seem to justify interventions made to reverse MEP deterioration in order to improve the clinical outcome. A multimodal IONM protocol could improve MEP interpretation at the end of the vascular phase of surgery, supporting the surgeon in their decision-making, before concluding vascular maneuvers., Competing Interests: Declaration of Competing Interest The authors report no conflicts of interest relevant to this article., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Objective: Intraoperative neuromonitoring (IONM) is useful during spinal cord operations, but whether IONM is necessary for posterior cervical surgeries for degenerative conditions is unknown. We evaluated the utility of somatosensory evoked potential (SSEP) and motor evoked potential (MEP) monitoring as a tool for predicting new postoperative neurologic deficits during posterior decompression and fusion for degenerative cervical spine conditions., Methods: We retrospectively reviewed posterior cervical operations performed at our institute over a 4-year period. Patients with postoperative neurologic deficits were identified, and a detailed analysis performed to ascertain whether SSEP or MEP monitoring accurately predicted the onset of new postoperative deficits., Results: Overall, 498 patients were included in the analysis (median age 66 years; range: 22-93 years). SSEP monitoring was performed in all patients, and both SSEP and MEP monitoring were performed in 121 patients (24%). Twenty-one patients (4.2%) had new postoperative neurologic deficits. SSEP had significantly higher specificity (90%) but lower sensitivity (33%) than MEP (74% specificity [P = 0.008], 50% sensitivity [P = 0.01]) for detecting neurologic compromise intraoperatively. For SSEP, the positive predictive value (PPV) and negative predictive value (NPV) in detecting intraoperative changes that translated to new postoperative neurological deficits were 12% and 97%, respectively, whereas for MEP, the PPV and NPV were 6% (P = 0.009) and 98% (P = 0.20), respectively., Conclusions: IONM during posterior cervical operations for degenerative conditions of the spine is not reliable at predicting new postoperative neurologic deficits in patients treated for degenerative conditions, but may provide peace of mind to the surgeon intraoperatively when no abnormalities are detected., (Copyright © 2022. Published by Elsevier Inc.)

Background: Maximizing the patient's onco-functional balance is the central tenet of brain tumor surgery. Consequently, numerous surgical adjuncts have been developed to facilitate identification of the tumor-brain interface and preservation of functional anatomy. Among these, intraoperative neurophysiologic monitoring (IONM) with direct cortical stimulation (DCS) and subcortical stimulation (SCS) remains the gold standard for real-time, functional mapping of motor and language activity. Stimulation techniques are not standardized and vary significantly across institutions, however. This is particularly true with SCS for mapping motor function., Methods: We reviewed the state of subcortical IONM and mapping techniques, including historical and predicate literature as well as new and emerging techniques. Here we discuss their evolution, clinical utility, and limitations to direct future research and application., Results: Our evaluation of the background and current clinical use of DCS and SCS techniques and protocols and identification of current trends and limitations focuses specifically on methods of SCS, given the heterogeneity in the published literature. We suggest directions to optimize the clinical utility of these tools., Conclusions: Despite significant heterogeneity in published techniques, trends support use of the Taniguchi method for SCS. Novel dynamic stimulation techniques may improve accuracy. Prospective studies to define standardized guidelines are needed., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Objective: To report on neurophysiological outcomes derived from transcranial magnetic stimulation (TMS) following autologous mesenchymal stem cells (aMSCs) therapy in patients with multiple sclerosis (MS)., Methods: 20 adults with confirmed MS were recruited to participate in a phase II randomized control trial to assess the safety and potential benefits of aMSCs infusion. At Week 0, patients were randomly assigned to receive either aMSCs (n = 9) or a placebo infusion (n = 11). At Week 24, the placebo group received the aMSCs infusion. Blind assessments were performed at Weeks 0, 24 and 48. Outcomes consisted of TMS measures of corticomotor excitability and motor conduction along with measures of motor impairments and disability., Results: Post-infusion, no change was detected in measures of corticomotor excitability or measures of intra- or interhemispheric inhibition. The latency of motor evoked potentials and central motor conduction time were significantly prolonged. These changes in motor conduction were associated with declines in hand dexterity post-infusion., Conclusion: Clinical and neurophysiological measures showed no improvement following aMSCs therapy in this cohort of MS patients., Significance: Although promising, stem cell therapy remains elusive regarding its benefits in influencing disease activity in MS patients., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Thoraco-abdominal aneurysm (TAA) repair carries a significant risk of spinal cord infarction. The latter results from irreversible changes in the spinal cord arterial network, e.g., sacrifice of the segmental arteries. Intra-operative neurophysiology with somatosensory and especially motor evoked potential (SEP and MEP respectively) monitoring, has emerged as an effective tool to assess the efficiency of the collateral blood flow, detect reversible spinal cord ischemia and guide the peri-operative multidisciplinary management to prevent postoperative paraplegia. The main roles of such monitoring include diagnosis of spinal cord vs peripheral limb ischemia, titration of mean arterial pressure during aortic clamping, the guidance of selective re-implantation of critical segmental arteries, and management of hemodynamics in the immediate postoperative period. In addition, manipulation of the aortic arch and proximal descending aorta, adds the risk of cerebral infarction from both low flow state and/or thromboembolic events. As such, EEG monitoring may be a useful add-on for either assessment of the efficiency of cerebral cooling as a neuroprotective method and/or for detection and treatment of reversible cerebral ischemia. This chapter presents the multimodality approach to open TAA monitoring as a versatile tool for the prevention of devastating postoperative neurologic deficits., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Electrophysiological monitoring of the peripheral nervous system during a variety of surgeries provides useful information that supplements and complements preoperative assessment. Monitoring improves localization and understanding of the underlying pathophysiology of peripheral nerve lesions leading to more rational treatment decisions and improved outcomes. Monitoring is accomplished by adaptation of routine electrodiagnostic techniques (i.e., nerve conduction studies, evoked potentials, and electromyography) with special attention to technical factors including electrical and movement artifact. These techniques have been successfully applied during surgery for entrapment neuropathies, traumatic nerve injury and repair, peripheral nerve tumors, and adjacent structure procedures that risk peripheral nerve injury. A clear understanding of the anatomy and neurophysiology is necessary, as is understanding and performing the difficult technical aspects of these studies to provide accurate information to enhance patient outcome and recovery. As in any intraoperative neurophysiologic monitoring (IONM) setting, constant and accurate communication between the IONM team, surgeon, and anesthesia team is critically important to meet these goals., (Copyright © 2022 Elsevier B.V. All rights reserved.)

There are many recent advances in intraoperative evoked potential techniques for mapping and monitoring neural function during surgery. In particular, somatosensory evoked potential optimization speeds surgical feedback, motor evoked potentials provide selective motor system information, and new visual evoked potential methods promise reliable visual system monitoring. This chapter reviews these advances and provides a comprehensive background for understanding their context and importance., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Surgery to correct a spinal deformity incurs a risk of injury to the spinal cord and roots. Injuries include postoperative paraplegia. Surgery for cervical myelopathy also incurs risk for postoperative motor deficits, as well as nerve injury most commonly at the C5 root. Risks can be mitigated by monitoring the nervous system during surgery. Ideally, monitoring detects an impending injury in time to intervene and correct the impairment before it becomes permanent. Monitoring includes several modalities of testing. Somatosensory evoked potentials measure axonal conduction in the spinal cord posterior columns. This can be checked almost continuously during surgery. Motor evoked potentials measure conduction along the lateral corticospinal tracts. Because motor pathway stimulation often produces a patient movement on the table, these often are tested periodically rather than continuously. Electromyography observes for spontaneous discharges accompanying injuries, and is useful to assess misplacement of pedicle screws. Literature demonstrates the usefulness of these techniques, their association with reducing motor adverse outcomes, and the relative value of the techniques. Neurophysiologic monitoring for scoliosis, kyphosis, and cervical myelopathy surgery are addressed, along with background information about those conditions., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Cerebral ischemia during carotid endarterectomy occurs via several mechanisms: inadequate collateral blood flow during carotid cross-clamping, thromboembolism due to carotid manipulation, and/or rethrombosis at the surgical site. Perioperative strokes increase not only the morbidity of endarterectomy but also its short- and long-term mortality. However, while several predictors of cerebral ischemia have been identified, precise individual risk is hard to assess. Since nonselective shunting during carotid cross-clamping is neither risk-free nor eliminates perioperative stroke, it is advisable to apply intraoperative monitoring techniques for detection and reversal of cerebral ischemia, which may occur at various stages of the procedure. This chapter addresses the methods available for monitoring, with an emphasis on neurophysiologic techniques, which are preferable given their direct assessment of how a decrease in cerebral blood flow impacts brain function. These include electroencephalography, somatosensory evoked potentials, and transcranial motor evoked potentials. Details regarding the methodology, advantages, disadvantages, and interpretation of these tests will be discussed within the anatomic, physiologic, surgical, and anesthetic contexts., (Copyright © 2022 Elsevier B.V. All rights reserved.)

This chapter describes the feasibility, utilization, and value of intraoperative neurophysiologic monitoring (IONM) in cerebrovascular cases. Practical advice on the integration of these adjunct methods into the modern neurosurgical operating room is based on our own neurophysiologic and neurosurgical experience. Most IONM is done for anterior circulation aneurysms. Somatosensory and motor evoked potentials are the modalities of choice covering vascular territories of the internal, anterior, and middle cerebral arteries. While monitoring both hemispheres with the unoperated side as control, monitoring focus is laid upon those territories at risk and bearing the aneurysm. The specificity of IONM is close to 1, and sensitivity ranges from 0.2 to 1, depending on the categorization of transient changes. The overall likelihood of worsened neurologic outcome after any intraoperative signal deterioration (transient or permanent) is 0.4., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Objective: Conventional time-series parameters are unreliable descriptors of motor-evoked potentials (MEPs) in brain tumor patients. Frequency domain analysis is suggested to provide additional information about the status of the cortico-spinal motor system. Aim of the present study was to describe the time-frequency representation of MEPs and its relation to the motor performance., Methods: This study enrolled 17 consecutive brain tumor patients with impaired dexterity. After brain mapping of the affected (AH) and non-affected (NAH) hemisphere, TMS was applied to the hotspots of the abductor pollicis brevis muscles (APB). Using a Morlet wavelet approach, event-related spectral perturbation (ERSP) and inter-trial coherence (ITC) of the MEPs were calculated and compared to the Grooved Pegboard Test (GPT). Additionally, inter- and intra-subject reliability was assessed by the intraclass correlation coefficient (ICC)., Results: MEPs were projecting to a frequency band between 30 and 400 Hz with a local maximum between 100 and 150 Hz. There was a significant ERSP and ITC reduction of the AH in comparison to the NAH. In contrast, no interhemispheric differences were depicted in the conventional time-series analysis. ERSP and ITC values correlated significantly with GPT results (r = 0.35 and r = 0.50). Time-frequency MEP description had good inter-and intra-subject reliability (ICC = 0.63)., Conclusions: Brain tumors affect corticospinal transmission resulting in a reduction of temporal and spectral MEP synchronization correlating with the dexterity performance., Significance: Time-frequency representation of MEPs provide additional information beyond conventional time-domain features., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Transcranial magnetic stimulation (TMS) can be a useful tool for the assessment of the brain functional reorganization in subjects with hemiplegic cerebral palsy (HCP). In this review, we performed a systematic search of all studies using TMS in order to explore the neuroplastic changes that occur in HCP patients. We aimed at investigating the usefulness of TMS to explore cortical excitability, plasticity and connectivity changes in HCP. Children with HCP due to unilateral lesions of the corticospinal system had ipsilateral motor evoked potentials (MEPs) similar to those recorded contralaterally. TMS studies demonstrated that occupational and constraint-induced movement therapy were associated with significant improvements in contralateral and ipsilateral corticomotor projection patterns. In addition, after intensive bimanual therapy, children with HCP showed increased activation and size of the motor areas controlling the affected hand. A TMS mapping study revealed a mediolateral location of the upper and lower extremity map motor cortical representations. Deficits in intracortical and interhemispheric inhibitory mechanisms were observed in HCP. Early hand function impairment correlated with the extension of brain damage, number of involved areas, and radiological signs of corticospinal tract (CST) degeneration. Clinical mirror movements (MMs) correlated with disability and CST organization in subjects with HCP and a positive relationship was found between MMs and MEPs strength. Therefore, TMS studies have shed light on important pathophysiological aspects of motor cortex and CST reorganization in HCP patients. Furthermore, repetitive TMS (rTMS) might have therapeutic effects on CST activities, functional connectivity and clinical status in children with HCP., Competing Interests: Declaration of Competing Interest None of the authors has potential conflicts of interest to be disclosed., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Objectives: Non-invasive brain stimulation (NIBS) is beneficial to many neurological and psychiatric disorders by modulating neuroplasticity and cortical excitability. However, recent studies evidence that single type of NIBS such as transcranial direct current stimulation (tDCS) does not have meaningful clinical therapeutic responses due to their small effect size. Transcranial near-infrared stimulation (tNIRS) is a novel form of NIBS. Both tNIRS and tDCS implement its therapeutic effects by modulating cortical excitability but with different mechanisms. We hypothesized that simultaneous tNIRS and tDCS is superior to single stimulation, leading to a greater cortical excitability., Methods: Sixteen healthy subjects participated in a double-blind, sham-controlled, cross-over designed study. Motor evoked potentials (MEPs) were used to measure motor cortex excitability. The changes of MEP were calculated and compared in the sham condition, tDCS stimulation condition, tNIRS condition and the simultaneous tNIRS and anodal tDCS condition., Results: tDCS alone and tNIRS alone both elicited higher MEP after stimulation, while the MEP amplitude in the simultaneous tNIRS and tDCS condition was significantly higher than either tNIRS alone or tDCS alone. The enhancement lasted up to at least 30 minutes after stimulation, indicating simultaneous 820 nm tNIRS with 2 mA anodal tDCS have a synergistic effect on cortical plasticity., Conclusions: Simultaneous application of tNIRS with tDCS produces a stronger cortical excitability effect., Significance: The simultaneous tNIRS and tDCS is a promising technology with exciting potential as a means of treatment, neuro-enhancement, or neuro-protection., Competing Interests: Declaration of Competing Interest None of the authors has any conflict of interest to disclose., (Copyright © 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objective: Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder that is associated with cognitive disabilities. Based on studies involving animals, the hypothesized cause of these disabilities results from increased activity of inhibitory interneurons that decreases synaptic plasticity. We obtained transcranial magnetic stimulation (TMS)-based measures of cortical inhibition, excitability and plasticity in individuals with NF1., Methods: We included 32 NF1 adults and 32 neurotypical controls. Cortical inhibition was measured with short-interval intracortical inhibition (SICI) and cortical silent period (CSP). Excitability and plasticity were studied with intermittent theta burst stimulation (iTBS)., Results: The SICI and CSP response did not differ between NF1 adults and controls. The response upon iTBS induction was significantly increased in controls (70%) and in NF1 adults (83%). This potentiation lasted longer in controls than in individuals with NF1. Overall, the TMS response was significantly lower in NF1 patients (F(1, 41) = 7.552, p = 0.009)., Conclusions: Individuals with NF1 may have reduced excitability and plasticity, as indicated by their lower TMS response and attenuation of the initial potentiated response upon iTBS induction. However, our findings did not provide evidence for increased inhibition in NF1 patients., Significance: These findings have potential utility as neurophysiological outcome measures for intervention studies to treat cognitive deficits associated with NF1., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objective: To improve estimates of motor evoked potential (MEP) performance during spine deformity surgeries by accounting for potential confounders., Methods: A meta-analysis of MEPs for spine deformity surgeries determined the probability of a MEP deterioration which recovered by the end of surgery, P(RSC), and the conditional probability of no new post-operative deficit given an RSC, P(NND|RSC), stratified by category of intraoperative adverse event associated with the MEP deterioration. A structural causal model (SCM) and propensity score matching accounted for intraoperative adverse events and patient diagnosis as potential confounders., Results: MEPs changes (either reversible, RSC or irreversible, IRREV) were reported for 295 of 5055 cases (6%) in 21 studies. The probability of no new motor deficit, P(NND), plotted against the probability of a RSC, P(RSC), for studies in the meta-analysis was highly significant (r = 0.71, p < 0.001). P(RSC) was 0.76 for an alert associated with correction, less for osteotomies (0.48, p = 0.0008), and tended to be higher for hypotension (0.92, p = 0.06). P(NND|RSC) was 0.94 for correction, less for positioning (0.82), and osteotomies (0.86), and greater for hypotension (1.0). In the SCM, a RSC after an alert was a highly significant and independent predictor of no new motor deficits (odds 25.2, p < 0.001)., Conclusion: There are significant differences in P(RSC) for hypotension and osteotomies, and in P(NND) for osteotomies and instrumentation, compared to correction. P(RSC) is a significant and independent predictor of outcomes., Significance: When MEPs are used for spine deformity surgeries, accounting for adverse events associated with an alert and patient diagnosis as potential confounders is expected to improve RSC prediction of post-operative outcomes and estimates of RSC efficacy in improving outcomes., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objectives: To analyze the somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) in neurologically asymptomatic Chiari malformation-associated scoliosis (CMS) patients with and without syringomyelia as compared with those in idiopathic scoliosis (IS) ones, and to identify whether the deformities have impacts on the neurophysiological monitoring., Patients and Methods: This study included neurologically asymptomatic CMS patients undergoing posterior correction surgery between January 2010 and January 2016. IS patients were involved as control group and a subgroup of age- and height-matched IS patients were selected. The age, standing height and Cobb angles of main curve were measured. The SEPs latency and amplitude, MEPs amplitude, and the rate of abnormal SEPs pathologic change were compared between CMS and IS patients using independent-sample t-test and Chi-square test., Results: Sixty CMS patients and 210 IS patients were included. There was no difference between CMS patients and IS or matched IS patients in SEPs latency and amplitude, MEPs amplitude or rate of abnormal SEPs (p > 0.05). Forty-eight CMS patients concurrent with syringomyelia were associated with higher Cobb angle of main curve and lower SEPs amplitude than those without syringomyelia (p < 0.05). No significant difference was found between CMS patients with and without syringomyelia in age, height, SEPs latency, MEPs amplitude or rate of abnormal SEPs (p > 0.05)., Conclusion: Neurologically asymptomatic CMS patients showed similar absolute values of neurophysiological monitoring with IS patients. The syringomyelia in CMS indicated more severe curvature and lower SEPs amplitude even after posterior fossa decompression., Competing Interests: Declaration of Competing Interest The authors report no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Objective: To assess the usefulness of upper limb (UE) motor evoked potential (MEPs) as a marker of motor impairment in a cohort of people with progressive multiple sclerosis (PwPMS)., Methods: we evaluated UE and lower extremities (LE) MEPs, 6-minutes walk-test (6MWT), 10-meter walk-test (10MWT), EDSS, 9-hole peg-test (9HPT), and measures of strength (MRC) and tone (MAS) to the UE and LE in 50 PwPMS (EDSS 4.0-6.5; P ≥ 3, C ≤ 2)., Results: Bilateral absence of LE-MEPs, found in 74% of cases, was associated with worse 10MWT and 6MWT. UE-MEPs were rarely absent (8%) but often delayed (74%). Abnormal UE-MEPs were associated with worse performance at 9HPT (25.8 vs 33.2 s). UE-MEPs latency correlated with 10MWT (rho = 0.597), 6MWT (rho = -0.425) and EDSS (rho = 0.296)., Conclusion: UE-MEPs may represent a clinically relevant outcome measure to quantify corticospinal tract integrity in PwPMS, at least when LE-MEPs cannot provide a measurable response., Significance: The strive for novel remyelination strategies in MS points to the need for quantitative conduction measurements in addition to clinical outcomes. The frequent absence of MEPs to the lower limbs in PwPMS may greatly limits their usefulness in monitoring progression or response to therapies. With this respect, the upper extremities may represent a better target., (Copyright © 2019. Published by Elsevier B.V.)

Objective: To evaluate cylindrical depth electrodes in the interhemispheric fissure as an alternative to subdural strip electrodes for direct cortical stimulation (DCS) leg motor evoked potential (MEP) monitoring., Methods: A cylindrical depth electrode was positioned in the interhemispheric fissure of 37 patients who underwent supratentorial brain surgery. Leg sensory and motor cortices were localized by highest tibial nerve somatosensory evoked potential amplitude and lowest DCS leg MEP threshold; the lowest-threshold electrode was then used for DCS leg MEP monitoring., Results: Intraoperative leg MEPs were obtained from all the patients in the series. The mean intensity applied for leg MEP monitoring with the cylindrical depth electrode was 15.2 ± 4.0 mA. No complications secondary to neurophysiological monitoring were detected., Conclusions: Lower extremity MEPs were consistently recorded using a multi-contact cylindrical depth electrode in the interhemispheric fissure by DCS., Significance: Cylindrical depth electrodes may be a safe and effective alternative for DCS in the interhemispheric fissure, where subdural strips are difficult to place., (Copyright © 2019 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objective: We aimed at assessing the usefulness of motor evoked potentials (MEPs) for exploring the integrity of striated sphincters and pelvic floor motor innervation in normal subjects and of repetitive transcranial magnetic stimulation TMS (rTMS) in patients with neurogenic bladder dysfunction., Methods: A systematic literature search was conducted using PubMed and Embase., Results: We identified, reviewed and discussed 11 articles matching the inclusion criteria., Conclusions: The assessment of MEPs could represent a useful tool in the investigation of patients with urologic disorders. High frequency rTMS can improve detrusor contraction and/or urethral sphincter relaxation in patients with multiple sclerosis and bladder dysfunction. Low frequency (LF) rTMS seems to be an effective treatment of neurogenic lower urinary tract dysfunctions in subjects with Parkinson's disease and possibly other neurodegenerative disorders. Furthermore, rTMS might have the potential to restore bladder and bowel sphincter function after incomplete spinal cord injury. LF rTMS could also relieve some symptoms of bladder pain syndrome and chronic pelvic pain., Significance: The clinical applicability of MEPs appears to be questionable, since a poor reproducibility was detected for all pelvic floor muscles. The use of rTMS in this field is emerging and the results of a few preliminary studies should be replicated in controlled, randomized studies with larger sample sizes., (Copyright © 2019 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Background: The motor evoked potentials (MEPs) elicited by single-pulse transcranial magnetic stimulation (TMS) vary considerably at rest, but the mechanism underlying this amplitude variation is largely unknown. We hypothesized that prestimulus EEG oscillations modulate the subsequent MEPs in a state-dependent manner., Objective: We studied the relationship between prestimulus alpha/beta oscillations and MEPs during eyes open (EO)/closed (EC) conditions, and then modulated TMS intensity in the EO condition. Furthermore, we developed an EEG-triggered TMS system ("informed open-loop") to verify our hypothesis., Methods: TMS was applied to the left motor cortex. We first compared EEG power differences between high- and low-amplitude MEP epochs in the EO and EC conditions when using a high TMS intensity. Next, we evaluated the effects of varying TMS intensities (high vs. low) on the EEG-MEP relationship. Finally, we used EEG-triggered TMS to determine whether prestimulus EEG oscillations predicted MEP amplitudes., Results: Prestimulus higher-power alpha/low-beta bands produced larger MEPs only in the high-intensity EO condition. A positive relationship between EEG power and MEP amplitude was observed at C3 and left frontal electrodes. This relationship was obscured when using the lower TMS intensity but was observed in the high-intensity condition at the C3 electrode. EEG-triggered TMS demonstrated that higher alpha power predicted higher MEP amplitudes, but beta power at around 20 Hz did not., Conclusions: A causal relationship between alpha/low-beta oscillations and MEP amplitudes at rest requires high TMS intensity delivered when eyes are open. This association may allow us to develop a new informed open-loop TMS protocol., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: Corkscrew (CS) electrodes are usually used for transcranial electrical stimulation (TES) in the intraoperative monitoring of motor evoked potentials (MEP). Direct cranial stimulation with peg-screw (PS) electrodes can elicit MEP. The present study investigated the difference in the initial threshold between PS and CS electrodes for intraoperative MEP monitoring., Methods: We retrospectively analyzed TES-MEP monitoring for supratentorial surgery in 72 patients. Of these 72 patients, 44 were monitored with PS and CS electrodes (PS/CS group) and 28 were monitored with CS and CS electrodes (CS/CS group). TES was used to deliver electrical stimulation by a train of 4-pulse anodal constant current stimulation. The initial threshold in each electrode was checked and analyzed., Results: In the PS/CS group, the initial threshold with the PS electrode was 38.3 ± 15.1 mA (mean ± standard deviation) on the affected side, and the initial threshold with the CS electrode was 51.4 ± 13.9 mA on the unaffected side. The initial threshold with the PS electrode was significantly lower than that with the CS electrode (P = 0.0001). In the CS/CS group, the initial threshold was 56.2 ± 16.5 mA on the affected side and 62.1 ± 18.6 mA on the unaffected side, with no statistically significant difference (P = 0.23)., Conclusion: The initial threshold to elicit MEP was significantly lower with the PS electrode than with the CS electrode. A PS electrode can be used as a feasible stimulation electrode for TES-MEP., (Copyright © 2019. Published by Elsevier Inc.)