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Background: We aimed to determine the diagnostic accuracy of intraoperative muscle motor evoked potentials (mMEPs) in predicting postoperative motor deficits in individual muscles of patients with benign intramedullary spinal cord tumors (IMSCTs), and to correlate them with long-term functional outcome. Methods: A retrospective study of patients operated for benign IMSCTs from 2009 to 2021 was performed. Sixty-nine patients in whom baseline mMEP recordings were obtained from at least one muscle were included for analysis. A persistent drop of the baseline mMEP by ≥ 50% from baseline was considered significant. Results: The mean age of the patients was 33.2 ± 15.8 years and 47 (68.1%) of them were male. The most common tumor was ependymoma (56.5%). Baseline mMEPs were obtained in 400/1011 muscles that were monitored. Postoperative worsening of motor power was noted in 109/400 (27.3%) muscles with baseline mMEP recordings compared to 213/611 (34.9%) muscles with no baseline recordings (p = 0.01). Patients who had deterioration of mMEPs had a significantly higher rate of worsening of muscle power postoperatively compared to those who had no deterioration of mMEPs (100% vs. 30.2%, p < 0.001). The sensitivity of mMEPs in predicting postoperative motor function in monitored muscles was 53.1% (95% CI 43.5–62.6), specificity was 97.9% (95% CI 95.5–99.2), PPV was 90.9% (95% CI 81.6–95.7) and NPV was 84.1% (95% CI 81.3–86.6). At median follow-up of 18.5 (IQR 13–40) months, there was no significant difference in Nurick grade between patients who had intraoperative deterioration of mMEPs and those who did not. Conclusions: Intraoperative mMEP reduction had high specificity and low sensitivity for predicting immediate postoperative neurological deficits following IMSCT resection. However, the majority of patients who had worsening of mMEPs, recovered to their preoperative functional status or a better status at follow-up and there was no significant difference in long-term functional outcome between patients with and without intraoperative mMEP changes. [ABSTRACT FROM AUTHOR]

In clinics, physical injuries to the spinal cord cause a temporary motor areflexia below lesion, known as spinal shock. This topic is still underexplored due to the lack of preclinical spinal cord injury (SCI) models that do not use anesthesia, which would affect spinal excitability. Our innovative design considered a custom-made micro impactor that provides localized and calibrated strikes to the ventral surface of the thoracic spinal cord of the entire CNS isolated from neonatal rats. Before and after injury, multiple ventral root (VR) recordings continuously traced respiratory rhythm, baseline spontaneous activities, and electrically induced reflex responses. As early as 200 ms after the lowering of the impactor, an immediate transient depolarization spread from the injury site to the whole spinal cord with distinct segmental velocities. Stronger strikes induced higher potentials causing, close by the site of injury, a transient drop in spinal cord oxygenation (SCO2) and a massive cell death with a complete functional disconnection of input along the cord. Below the impact site, expiratory rhythm and spontaneous lumbar activity were suppressed. On lumbar VRs, reflex responses transiently halted but later recovered to control values, while electrically induced fictive locomotion remained perturbed. Moreover, low-ion modified Krebs solutions differently influenced impact-induced depolarizations, the magnitude of which amplified in low Cl−. Overall, our novel ex vivo platform traces the immediate functional consequences of impacts to the spinal cord during development. This basic study provides insights on the SCI pathophysiology, unveiling an immediate chloride dysregulation. In a neonatal rodent preparation of ex vivo CNS, a physical trauma to the cord is followed by an immediate depolarization spreading both caudally and rostrally. A massive impact-induced depolarization temporarily abolishes spontaneous motor discharges and electrically induced reflex responses below the level of injury. Transient areflexia mimics the spinal shock reported in clinics after SCI. [ABSTRACT FROM AUTHOR]

Several computational models make predictions about the activation states of individual elements of an action sequence during planning and execution; however, the neural mechanisms of action planning are still poorly understood. Simple chaining models predict that only the first response in an action sequence should be active during planning. Conversely, some parallel activation models suggest that during planning, a serial inhibition process places the individual elements of the action into a serial order across a winner-takes-all competitive choice gradient in which earlier responses are more active, and hence likely to be selected for execution compared with later responses. We triggered transcranial magnetic stimulation pulses at 200 or 400 ms after the onset of a five-letter word, in which all but one response was planned and typed with the left hand, except for a single letter which required a right index finger response exclusively at one of five serial positions. We measured the resulting motor-evoked potentials at the right index finger as a marker for the activation state of that planned response. We observed no difference in motor-evoked potential amplitude across any serial position when a right index finger response was planned at 200 ms after the onset of the word; however, we observed a graded pattern of activation at 400 ms, with earlier positions that required a right index finger response showing greater motor-evoked potentials amplitude compared with later positions. These findings provide empirical support for competitive queuing computational models of action planning. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the sensitivity and specificity of these monitoring parameters in predicting postoperative neurological dysfunction.

Purpose: Attention to motor evoked potential (MEP) stimulation intensity is necessary to avoid false negative MEP results during intracranial procedures. Observing ipsilateral (crossover) MEP responses has been hypothesized to indicate inappropriately strong stimulation intensity. We describe a case where persistent crossover MEP responses falsely suggested that stimulus intensity was too high and describe an alternative method to guide the selection of MEP stimulation intensity. Methods: A patient undergoing a suboccipital craniotomy for tumor resection had bilateral transcranial electrical MEP monitoring under total intravenous anesthesia. MEP results were obtained from left and right hand using C4-Cz and C3-Cz stimulation montages respectively. Selection of an appropriately superficial stimulus intensity was guided using MEP onset latencies. Results: MEP acquisition proceeded normally for contralateral left hand (C4-Cz montage). However, using the C3-Cz montage, persistent crossover responses were noted at stimulation intensities as low as threshold for contralateral right hand MEP (94 V/166 mA). Appropriate MEP stimulus intensity for subsequent monitoring (approximately 96 V/172 mA) was determined utilizing onset latency measurements from contralateral hand MEP responses. The stimulus intensity chosen was predicated on onset latency being ≥ 2 ms longer than latency at maximal stimulus level (shortest latency). A stimulus intensity-latency plot was generated offline to illustrate this important relationship for intracranial MEP use. MEP acquisition proceeded without incident and gross total resection was achieved without postoperative motor deficits. Conclusion: Despite crossover appearance contralateral hand MEP were quantitatively validated for intraoperative application using onset latency guidance. [ABSTRACT FROM AUTHOR]

• In high-cervical intramedullary spinal cord tumor surgery, unimpaired D-wave reliably predicts preserved gross-motor function for all covered spinal levels. • D-wave fails to predict the occurrence of mild permanent postoperative deficits affecting the fine-motor and compex hand function. • Only the combination of D-wave, mMEPs, EMG and SSEPs is able to provide a viable power for monitoring the complex hand function. 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. 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. 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%). 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. Our study underlines the importance of multimodal IONM for fine-motor/complex hand function. [ABSTRACT FROM AUTHOR]

Background: Stroke survivors exhibit persistent abnormal gait patterns, particularly in diminished walking ability and stability, limiting mobility and increasing the risk of falling. The purpose of the study was to determine the effects of repetitive transcranial magnetic stimulation (rTMS) coupled with cycling exercise on walking ability and stability in patients with stroke and explore the potential mechanisms underlying motor cortex recovery. Methods: In this double‐blinded randomized pilot trial, 32 stroke patients were randomly separated into the real‐rTMS group (RG, receiving rTMS during active cycling exercise) and the sham‐rTMS group (SG, receiving sham rTMS during active cycling exercise). Participants completed 10 exercise sessions (5 times per week). Lower extremity function was measured using the Fugl‐Meyer assessment of lower extremity (FMA‐LE), and functional balance ability was measured by the Berg balance scale (BBS). The 2‐min walk test (2MWT) and standing balance test were employed to evaluate walking and balance ability. Motor evoked potentials (MEPs) were measured to evaluate cortical excitability. The above assessments were administered at baseline and after the intervention. Additionally, the cycling exercise performance was recorded after the initial and final exercise sessions to evaluate the motor control during exercise. Results: The RG showed significant improvements in lower extremity function (FMA‐LE) and functional balance ability (BBS) compared to the SG at postintervention. The walking and balance abilities, as well as the motor asymmetry of cycling exercise, significantly improved in RG. Additionally, participants in RG exhibited a higher elicitation rate of ipsilesional MEPs than that in SG. The improvements in motor asymmetry of cycling exercise in RG were significantly associated with increases in FMA‐LE scores and walking ability. Conclusion: The combination of rTMS and cycling exercise effectively improves walking ability and walking stability in patients with stroke, which may be related to the excitability modulation of the motor cortex induced by rTMS. Trial Registration: Clinical Trial Registry identifier: ChiCTR2400079360. [ABSTRACT FROM AUTHOR]

ObjectiveThis study investigates the effects of temporal interference stimulation (TI) with different envelope frequencies on the cortical excitability of the primary motor cortex (M1).MethodsIn this randomized, double-blind, crossover study, 26 participants completed four separate study visits. During these visits, they received 20 min of three types of TI (10, 20, and 40 Hz envelope frequency) and sham stimulation applied over M1 in a randomized order. Transcranial magnetic stimulation (TMS) was employed to assess motor-evoked potentials (MEP) and resting motor threshold (RMT) over the left M1 (ipsilateral area) and right M1 (contralateral area) before, immediately after, and 30 and 60 min after stimulation.ResultsThe blinding efficacy was excellent, and no severe side effects were reported. TI stimulation with varying envelope frequencies affected MEP differently; 20 Hz TI stimulation enhanced the MEP of the ipsilateral M1 with after-effects appearing at 60 min, and no significant differences were observed between the 10 or 20 Hz TI stimulation with sham groups. However, no significant changes in RMT were observed under any of the TI conditions.Conclusion20 Hz TI stimulation increased the cortical excitability of the ipsilateral M1, highlighting that frequency is an important factor in the modulatory effect of TI.

Background: During epilepsy surgery, it is equally important to record electrocorticography (ECoG) for detecting epileptogenic activity and guiding brain resection, and to evaluate neuromonitoring data, particularly motor evoked potentials (MEP), for avoidance of postoperative neurological complications. However, sevoflurane, which is commonly used during recording of ECoG, may attenuate the MEP response. It enforces anesthesiologists and neurosurgeons to select one anesthetic agent over another, facilitating either ECoG or MEP monitoring. Case presentation: In the presented case of a 20-year-old man, who underwent surgery for temporal lobe epilepsy, a novel technique of neuroanesthesia was introduced, integrating initial induction of the total intravenous anesthesia (TIVA) with propofol (effect-site concentration, 2.3–3.0 μg/ml), its subsequent switching to sevoflurane (end-tidal concentration, 2.5%) for ECoG recording, and further change back to TIVA for MEP monitoring during brain resection. Conclusions: Intraoperative switch of anesthetic agents according to specific intraoperative requirements may be useful for cases of brain surgery requiring both ECoG recordings and MEP monitoring. [ABSTRACT FROM AUTHOR]

Transcranial Motor Evoked Potentials (TcMEPs) can improve intraoperative detection of femoral plexus and nerve root injury during lumbosacral spine surgery. However, even under ideal conditions, TcMEPs are not completely free of false-positive alerts due to the immobilizing effect of general anesthetics, especially in the proximal musculature. The application of transcutaneous stimulation to activate ventral nerve roots directly at the level of the conus medularis (bypassing the brain and spinal cord) has emerged as a method to potentially monitor the motor component of the femoral plexus and lumbosacral nerves free from the blunting effects of general anesthesia. To evaluate the reliability and efficacy of transabdominal motor evoked potentials (TaMEPs) compared to TcMEPs during lumbosacral spine procedures. We present the findings of a single-center 12-month retrospective experience of all lumbosacral spine surgeries utilizing multimodality intraoperative neuromonitoring (IONM) consisting of TcMEPs, TaMEPs, somatosensory evoked potentials (SSEPs), electromyography (EMG), and electroencephalography. Two hundred and twenty patients having one, or a combination of lumbosacral spine procedures, including anterior lumbar interbody fusion (ALIF), lateral lumbar interbody fusion (LLIF), posterior spinal fusion (PSF), and/or transforaminal lumbar interbody fusion (TLIF). Intraoperative neuromonitoring data was correlated to immediate postoperative neurologic examinations and chart review. Baseline reliability, false positive rate, true positive rate, false negative rate, area under the curve at baseline and at alerts, and detection of preoperative deficits of TcMEPs and TaMEPs were compared and analyzed for statistical significance. The relationship between transcutaneous stimulation voltage level and patient BMI was also examined. TaMEPs were significantly more reliable than TcMEPs in all muscles except abductor hallucis. Of the 27 false positive alerts, 24 were TcMEPs alone, and 3 were TaMEPs alone. Of the 19 true positives, none were detected by TcMEPs alone, 3 were detected by TaMEPs alone (TcMEPs were not present), and the remaining 16 true positives involved TaMEPs and TcMEPs. TaMEPs had a significantly larger area under the curve (AUC) at baseline than TcMEPs in all muscles except abductor hallucis. The percent decrease in TcMEP and TaMEP AUC during LLIF alerts was not significantly different. Both TcMEPs and TaMEPs reflected three preexisting motor deficits. Patient BMI and TaMEP stimulation intensity were found to be moderately positively correlated. These findings demonstrate the high reliability and predictability of TaMEPs and the potential added value when TaMEPs are incorporated into multimodality IONM during lumbosacral spine surgery. [ABSTRACT FROM AUTHOR]

• Combined somatosensory evoked potential (SSEP) and transcranial motor evoked potential (MEP) loss was associated with a delayed clinical recovery postoperatively. • Bilateral SSEP loss, bilateral SSEP and MEP loss, and delayed neurologic recovery were all significantly associated with having unmonitorable IONM signals at repeat surgery. • Two weeks after aborted surgery, over 70% of patients had monitorable IONM signals upon return to the operating room. Intraoperative neurophysiological monitoring (IONM) is used to reduce the risk of spinal cord injury during pediatric spinal deformity surgery. Significant reduction and/or loss of IONM signals without immediate recovery may lead the surgeon to acutely abort the case. The timing of when monitorable signals return remains largely unknown. The goal of this study was to investigate the correlation between IONM signal loss, clinical examination, and subsequent normalization of IONM signals after aborted pediatric spinal deformity surgery to help determine when it is safe to return to the operating room. This is a multicenter, multidisciplinary, retrospective study of pediatric patients (<18 years old) undergoing spinal deformity surgery whose surgery was aborted due to a significant reduction or loss of IONM potentials. Sixty-six patients less than 18 years old who underwent spinal deformity surgery that was aborted due to IONM signal loss were enrolled into the study. IONM data, operative reports, and clinical examinations were investigated to determine the relationship between IONM loss, clinical examination, recovery of IONM signals, and clinical outcome. Information regarding patient demographics, deformity type, clinical history, neurologic and ambulation status, operative details, IONM information (eg, quality of loss [SSEPs, MEPs], laterality, any recovery of signals, etc.), intraoperative wake-up test, postoperative neurologic exam, postoperative imaging, and time to return to the operating were all collected. All factors were analyzed and compared with univariate and multivariate analysis using appropriate statistical analysis. Sixty-six patients were enrolled with a median age of 13 years [IQR 11-14], and the most common sex was female (42/66, 63.6%). Most patients had idiopathic scoliosis (33/66, 50%). The most common causes of IONM loss were screw placement (27/66, 40.9%) followed by rod correction (19/66, 28.8%). All patients had either complete bilateral (39/66, 59.0%), partial bilateral (10/66, 15.2%) or unilateral (17/66, 25.8%) MEP loss leading to termination of the case. Overall, when patients were returned to the operating room 2 weeks postoperatively, nearly 75% (40/55) had monitorable IONM signals. Univariate analysis demonstrated that bilateral SSEP loss (p=.019), bilateral SSEP and MEP loss (p=.022) and delayed clinical neurologic recovery (p=.008) were significantly associated with having unmonitorable IONM signals at repeat surgery. Multivariate regression analysis demonstrated that delayed clinical neurologic recovery (> 72 hours) was significantly associated with unmonitorable IONM signals when returned to the operating room (p=.006). All patients ultimately made a full neurologic recovery. In children whose spinal deformity surgery was aborted due to intraoperative IONM loss, there was a strong correlation between combined intraoperative SSEP/MEP loss, the magnitude of IONM loss, the timing of clinical recovery, and the time of electrophysiological IONM recovery. The highest likelihood of having a prolonged postoperative neurological deficit and undetectable IONM signals upon return to the OR occurs with bilateral complete loss of SSEPs and MEPs. [ABSTRACT FROM AUTHOR]

D-waves (also called direct waves) result from the direct activation of fast-conducting, thickly myelinated corticospinal tract (CST) fibres after a single electrical stimulus. During intraoperative neurophysiological monitoring, D-waves are used to assess the long-term motor outcomes of patients undergoing surgery for intramedullary spinal cord tumours, selected cases of intradural extramedullary tumours and surgery for syringomyelia. In the present manuscript, we discuss D-wave monitoring and its role as a tool for monitoring the CST during spinal cord surgery. We describe the neurophysiological background and provide some recommendations for recording and stimulation, as well as possible future perspectives. Further, we introduce the concept of anti D-wave and present an illustrative case with successful recordings. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effects of temporal interference electrical fields (TI) on motor cortical excitability and motor learning abilities in healthy adults, in order to provide evidence for the application of TI stimulation in human. Method: A randomized crossover double-blind design was used with healthy adults participants. Experiment 1: twenty subjects completed transcranial magnetic stimulation (TMS) testing to assess changes in cortical excitability indicators before and after stimulation, including motor evoked potentials (MEP), resting motor threshold (RMT), short- interval intracortical inhibition (SICI), and intracortical facilitation (ICF). Experiment 2: sixteen subjects completed the random reaction time task (RRTT) and the serial reaction time task (SRTT), with performance indicators including average reaction time (RT), first implicit learning (FIL), and second implicit learning (SIL). The effects of TI stimulation on cortical excitability and motor learning abilities were evaluated using a two-factor repeated measures analysis of variance. Result: Experiment 1: there were significant interactions between stimulation condition and time on MEP (F= 28.787, P<0.001, ηP²=0.602) and RMT (F=23.524, P<0.001, ηP²=0.580), while SICI and ICF showed no significant interaction effects. Experiment 2: compared to sham stimulation, FIL in SRTT was significantly improved after TI stimulation (F=4.601, P=0.049, ηP²=0.235), while there was no significant interaction effect in the RRTT task. Conclusion: Variable frequency TI stimulation can significantly increase cortical excitability in the primary motor cortex, and this regulatory effect may contribute to enhancing motor learning performance in healthy adults. [ABSTRACT FROM AUTHOR]

Introduction: Impaired motor function is a major cause of disability in multiple sclerosis (MS), involving various neuroplasticity processes typically assessed by neuroimaging. This study aimed to determine whether navigated transcranial magnetic stimulation (nTMS) could also provide biomarkers of motor cortex plasticity in patients with MS (pwMS). Methods: nTMS motor mapping was performed for hand and leg muscles bilaterally. nTMS variables included the amplitude and latency of motor evoked potentials (MEPs), corticospinal excitability measures, and the size of cortical motor maps (CMMs). Clinical assessment included disability (Expanded Disability Status Scale, EDSS), strength (MRC scale, pinch and grip), and dexterity (9-hole Pegboard Test). Results: nTMS motor mapping was performed in 68 pwMS. PwMS with high disability (EDSS ≥ 3) had enlarged CMMs with less dense distribution of MEPs and various MEP parameter changes compared to pwMS with low disability (EDSS < 3). Patients with progressive MS had also various MEP parameter changes compared to pwMS with relapsing remitting form. MRC score correlated positively with MEP amplitude and negatively with MEP latency, pinch strength correlated negatively with CMM volume and dexterity with MEP latency. Conclusions: This is the first study to perform 4-limb cortical motor mapping in pwMS using a dedicated nTMS procedure. By quantifying the cortical surface representation of a given muscle and the variability of MEP within this representation, nTMS can provide new biomarkers of motor function impairment in pwMS. Our study opens perspectives for the use of nTMS as an objective method for assessing pwMS disability in clinical practice. [ABSTRACT FROM AUTHOR]

IntroductionThe influence of various levels of sedation depth on motor evoked potentials (MEP) reproducibility in youth is still unclear because of a lack of data. We tested the hypothesis that a deeper level of total intravenous anesthesia (TIVA) [bispectral index (BIS) 40 ± 5 compared to 60 ± 5] can affect surgeon-directed MEP and their interpretation in youths.MethodsAll patients received TIVA combined with propofol and remifentanil. TIVA was initially maintained at a BIS level of 60 ± 5. The sedation anesthesia was deepened to BIS level 40 ± 5 before the skin incision. MEP were recorded and interpreted at both BIS levels. The primary endpoint was to evaluate the effect of the depth of sedation on the MEP reproducibility directed and interpreted by the surgical team in each patient separately. The secondary endpoint was to compare the relativized MEP parameters (amplitude and latency) in percentage at various levels of sedation in each patient separately. We planned to enroll 150 patients. Due to the COVID-19 pandemic, we decided to analyze the results of the first 50 patients.ResultsThe surgical team successfully recorded and interpreted MEP in all 50 enrolled patients in both levels of sedation depth without any clinical doubts. The MEP parameters at BIS level 40 ± 5, proportionally compared with the baseline, were latency 104% (97–110%) and the MEP amplitudes 84.5% (51–109%).ConclusionPreliminary data predict that deeper sedation (BIS 40 ± 5) does not affect the surgical team’s interpretation of MEP in youth patients. These results support that surgeon-directed MEP may be an alternative when neurophysiologists are unavailable.

Volitional movement requires descending input from the motor cortex and sensory feedback through the spinal cord. We previously developed a paired brain and spinal electrical stimulation approach in rats that relies on convergence of the descending motor and spinal sensory stimuli in the cervical cord. This approach strengthened sensorimotor circuits and improved volitional movement through associative plasticity. In humans, it is not known whether posterior epidural spinal cord stimulation targeted at the sensorimotor interface or anterior epidural spinal cord stimulation targeted within the motor system is effective at facilitating brain evoked responses. In 59 individuals undergoing elective cervical spine decompression surgery, the motor cortex was stimulated with scalp electrodes and the spinal cord was stimulated with epidural electrodes, with muscle responses being recorded in arm and leg muscles. Spinal electrodes were placed either posteriorly or anteriorly, and the interval between cortex and spinal cord stimulation was varied. Pairing stimulation between the motor cortex and spinal sensory (posterior) but not spinal motor (anterior) stimulation produced motor evoked potentials that were over five times larger than brain stimulation alone. This strong augmentation occurred only when descending motor and spinal afferent stimuli were timed to converge in the spinal cord. Paired stimulation also increased the selectivity of muscle responses relative to unpaired brain or spinal cord stimulation. Finally, clinical signs suggest that facilitation was observed in both injured and uninjured segments of the spinal cord. The large effect size of this paired stimulation makes it a promising candidate for therapeutic neuromodulation. Key points: Pairs of stimuli designed to alter nervous system function typically target the motor system, or one targets the sensory system and the other targets the motor system for convergence in cortex.In humans undergoing clinically indicated surgery, we tested paired brain and spinal cord stimulation that we developed in rats aiming to target sensorimotor convergence in the cervical cord.Arm and hand muscle responses to paired sensorimotor stimulation were more than five times larger than brain or spinal cord stimulation alone when applied to the posterior but not anterior spinal cord.Arm and hand muscle responses to paired stimulation were more selective for targeted muscles than the brain‐ or spinal‐only conditions, especially at latencies that produced the strongest effects of paired stimulation.Measures of clinical evidence of compression were only weakly related to the paired stimulation effect, suggesting that it could be applied as therapy in people affected by disorders of the central nervous system. [ABSTRACT FROM AUTHOR]

• Motor evoked potential amplitudes may be small and difficult to monitor during surgery in some patients. • Tetanic stimulation of peripheral nerves improves motor evoked potential amplitudes. • Tetanic stimulation can also be used in patient with myelopathy and peripheral neuropathy, with some cautions. 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. 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. 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. The p-MEP technique can improve MEP amplitudes, including in patients with myelopathy. In patients with peripheral neuropathy, the results were mixed. Tetanic stimulation can enhance intraoperative MEP amplitudes. [ABSTRACT FROM AUTHOR]

Study Design: Systematic Review and Meta-analysis. Objective: 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. Methods: 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. Results: 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%. Conclusion: 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. [ABSTRACT FROM AUTHOR]

The article provides a consensus document on multimodal intraoperative neurophysiological monitoring in neurosurgical procedures, focusing on basic fundamentals. Topics include guidelines for intraoperative neurophysiological monitoring and the management of patients with aneurysmal subarachnoid hemorrhage, along with the application of evoked potentials in neuroanesthesia.

Objective To compare the sensitivity of surface electromyography (SEMG) based brain motor control protocol and transcranial magnetic stimulation (TMS) based motor evoked potentials in the evaluation of patients with complete spinal cord motor injury. Methods 31 patients diagnosed complete spinal cord motor injury were admitted to the China Rehabilitation Research Center from March 2021 to April 2023 underwent sEMG based motor control detection and TMS based motor evoked potential detection, respectively. Results 27 of 31 patients (87%) had at least one channel ranked 4 or 5, and a total of 248 muscles were tested in 31 patients (8 muscles per patient, rectus femoris, biceps femoris, anterior tibialis and gastrocnemius on the right and left sides), of which 79 (32%) muscles could be measured with a channel ranked 4 or 5. 40 of 62 limbs(64%) had at least one channel rank 4 or 5, and 21 of 31 patients (68%) had the highest rank 5 channel. However, none of the 31 patients were positive in TMS-based motor evoked potential testing. Conclusion SEMG is significantly more sensitive than motor evoked potentials in the evaluation of patients with complete spinal cord motor injury. [ABSTRACT FROM AUTHOR]

Background: An essential factor in the validity of motor evoked potential (MEP)s recorded by transcranial magnetic stimulation (TMS) over multiple times is their test-retest reliability which to a large extent depends on the accuracy and competence of the assessor (intra-rater reliability). However, intra-rater reliability is infrequently reported in TMS studies suggesting that this is rarely done. Objectives: This study was conducted to determine the intra-rater within and between-session reliability of a newly trained TMS assessor prior to a main TMS study and report on the methodology used to encourage similar practice. Methods: Fourteen (10 males, 4 females; mean age: 32 ± 5.8 years) participants took part in the study. Motor evoked potentials were elicited from a relaxed, right first dorsal interosseous (FDI) muscle three times (T1, T2 and T3) across two testing sessions at least 48 hours apart. During the first session, MEPs were recorded twice (T1 and T2) within an interval of 20 minutes to determine the within (intra) session reliability of the assessor. During the second session, a single measurement was carried out (T3) which was compared to T1 to determine the inter-session reliability. Results: Repeated measure analysis of variance (ANOVA) did not reveal significant difference in the amplitude of the MEPs obtained across the three time periods (P = 0.196) demonstrating agreement in the MEPs and hence the reliability of the assessor. Additionally, the intraclass correlation coefficient (ICC) between T1 and T2; and T1 and T3 were 0.952 (P < 0.001) and 0.833 (P = 0.001) respectively further indicating the within and between sessions reliability of the assessor. Conclusions: The agreement between the three measured MEPs amplitude and the significant ICC demonstrates the reliability of the assessor in this study to use TMS for research. We suggest that the intra-rater reliability of new TMS operators should be established using the methodology in this report prior to main TMS studies. [ABSTRACT FROM AUTHOR]

Objective Considering spinal deformity patients with pre‐operative neurological deficit were associated with more intra‐operative iatrogenic neurological complications than those without, intra‐operative neurophysiological monitoring (IONM) has been used for detecting possible iatrogenic injury timely. However, the IONM waveforms are often unreliable. To analyze the performance of intra‐operative neurophysiological monitoring (IONM) including somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) in patients with pre‐operative neurological deficit undergoing posterior spinal correction surgery, and to identify the high‐risk factors for failed IONM. Methods Patients with pre‐operative neurological deficit undergoing posterior spinal correction surgery between October 2017 and January 2022 were retrospectively reviewed. The presence or absence of SEP and MEP of target muscles were separately recorded. The P37/N50 latency and amplitude of SEP, and the MEP amplitude were measured. Any IONM alerts were also recorded. The IONM performance was compared among patients with different etiologies, levels responsible for neurological deficit, and strength of IONM‐target muscles. Patients' demographics were analyzed using the descriptive statistics and were presented with mean ± standard deviation. Comparison analysis was performed using χ2‐test and statistically significant difference was defined as p

Background: Transcutaneous auricular vagus nerve stimulation (taVNS) has emerged as a promising brain stimulation modality in poststroke upper extremity rehabilitation. Although several studies have examined the safety and reliability of taVNS, the mechanisms underlying motor recovery in stroke patients remain unclear. Objectives: This study aimed to investigate the effects of taVNS paired with task-oriented training (TOT) on upper extremity function in patients with subacute stroke and explore the potential underlying mechanisms. Methods: In this double-blinded, randomized, controlled pilot trial, 40 patients with subacute stroke were randomly assigned to two groups: the VNS group (VG), receiving taVNS during TOT, and the Sham group (SG), receiving sham taVNS during TOT. The intervention was delivered 5 days per week for 4 weeks. Upper extremity function was measured using the Fugl-Meyer Assessment-Upper Extremity (FMA-UE), the Action Research Arm Test (ARAT). Activities of daily living were measured by the modified Barthel Index (MBI). Motor-evoked potentials (MEPs) were measured to evaluate cortical excitability. Assessments were administered at baseline and post-intervention. Additionally, the immediate effect of taVNS was detected using functional near-infrared spectroscopy (fNIRS) and heart rate variability (HRV) before intervention. Results: The VG showed significant improvements in upper extremity function (FMA-UE, ARAT) and activities of daily living (MBI) compared to the SG at post-intervention. Furthermore, the VG demonstrated a higher rate of elicited ipsilesional MEPs and a shorter latency of MEPs in the contralesional M1. In the VG, improvements in FMA-UE were significantly associated with reduced latency of contralesional MEPs. Additionally, fNIRS revealed increased activation in the contralesional prefrontal cortex and ipsilesional sensorimotor cortex in the VG in contrast to the SG. However, no significant between-group differences were found in HRV. Conclusion: The combination of taVNS with TOT effectively improves upper extremity function in patients with subacute stroke, potentially through modulating the bilateral cortex excitability to facilitate task-specific functional recovery. [ABSTRACT FROM AUTHOR]

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). 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. 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%. 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. [ABSTRACT FROM AUTHOR]

We report a case where neuromonitoring, using motor evoked potentials (MEP), detected an intraoperative L5 nerve root deficit during a lumbosacral decompression and instrumented fusion procedure. Critically, the MEP changes were not preceded nor accompanied by any significant spontaneous electromyography (sEMG) activity. Presumptive L5 innervated muscles, including tibialis anterior (TA), extensor hallucis longus (EHL) and gluteus maximus, were targets for nerve root surveillance using combined MEP and sEMG techniques. During a high-grade spondylolisthesis correction procedure, attempts to align a left-sided rod resulted in repeated loss and recovery cycles of MEP from the TA and EHL. No accompanying EMG alerts were associated with any of the MEP changes nor were MEP variations seen from muscles innervated above and below L5. After several attempts, the rod alignment was achieved, but significant MEP signal decrement (72% decrease) remained from the EHL. Postoperatively, the patient experienced significant foot drop on the left side that recovered over a period of 3 months. This case contributes to a growing body of evidence that exclusive reliance on sEMG for spinal nerve root scrutiny can be unreliable and MEP may provide more dependable data on nerve root patency. [ABSTRACT FROM AUTHOR]

Background: Lower capacity to generate knee extension maximal voluntary force (MVF) has been observed in individuals affected with patellar tendinopathy (PT) compared to asymptomatic controls. This MVF deficit is hypothesized to emanate from alterations in corticospinal excitability (CSE). The modulation of CSE is intricately linked to the excitability levels at multiple sites, encompassing neurones within the corticospinal tract (CST), intracortical neurones within the primary motor cortex (M1), and the alpha motoneurone. The aim of this investigation was to examine the excitability of intracortical neurones, CST neurones, and the alpha motoneurone, and compare these between volleyball and basketball athletes with PT and matched asymptomatic controls. Method: Nineteen athletes with PT and 18 asymptomatic controls participated in this cross‐sectional study. Transcranial magnetic stimulation was utilized to assess CST excitability, corticospinal inhibition (silent period, and short‐interval cortical inhibition). Peripheral nerve stimulation was used to evaluate lumbar spine and alpha motoneurone excitability, including the evocation of lumbar‐evoked potentials and maximal compound muscle action potential (MMAX), and CSE with central activation ratio (CAR). Knee extension MVF was also assessed. Results: Athletes with PT exhibited longer silent period duration and greater electrical stimulator output for MMAX, as well as lower MVF, compared to asymptomatic controls (p < 0.05). Conclusion: These findings indicate volleyball and basketball athletes with PT exhibit reduced excitability of the alpha motoneurone or the neuromuscular junction, which may be linked to lower MVF. Subtle alterations at specific sites may represent compensatory changes to excitability aiming to maintain efferent drive to the knee extensors. [ABSTRACT FROM AUTHOR]

Multimodal intraoperative neurophysiological monitoring (IONM) is highly valuable in scoliosis surgeries for monitoring spinal cord function, particularly during instrumentation. Accurate timing of baseline recordings of TcMEP and SSEP is crucial, as any changes observed during surgery and instrumentation are compared to these baseline recordings. However, the impact of ultrasound-guided erector spinae block (USG-ESPB) on SSEP and TcMEP is not well-studied in scoliosis surgery. In this report, we present two cases of scoliosis surgery where bilateral two-level USG-ESPB using different concentrations of ropivacaine (0.375% and 0.2%) resulted in a transient and significant deterioration of TcMEP, occurring 3 minutes after the block and lasting for 20 minutes. Remarkably, SSEPs remained unchanged during this period. These findings suggest that USG-ESPB may produce TcMEP changes, highlighting the importance of carefully considering the timing of baseline TcMEP acquisition in scoliosis surgery. [ABSTRACT FROM AUTHOR]

Abstract Background Partial 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. Methods Patients 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. Results A 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. Conclusions Sugammadex 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 registration The study was registered on clinicaltrials.gov.cn on 29/10/2020 (trial registration number: NCT04608682).

D-waves (also called direct waves) result from the direct activation of fast-conducting, thickly myelinated corticospinal tract (CST) fibres after a single electrical stimulus. During intraoperative neurophysiological monitoring, D-waves are used to assess the long-term motor outcomes of patients undergoing surgery for intramedullary spinal cord tumours, selected cases of intradural extramedullary tumours and surgery for syringomyelia. In the present manuscript, we discuss D-wave monitoring and its role as a tool for monitoring the CST during spinal cord surgery. We describe the neurophysiological background and provide some recommendations for recording and stimulation, as well as possible future perspectives. Further, we introduce the concept of anti D-wave and present an illustrative case with successful recordings.

Hahn–Steinthal fractures are rare and often neglected. Their initial management should be early, given the relatively high complication rate. We report eight cases of type I capitellum fractures treated by Herbert screw fixation. Between 2019 and 2022, we selected eight patients (six men and two women) with a mean age of 25 years (18–40 years). The mean follow-up was 2 years (1–3 years). Clinical results were assessed using the Mayo Clinic Elbow Performance Score (MEPS). The mean arc of mobilitý was 135° (105°–150°) for flexion/extension and 161° (150°–175°) for pronosupination. The mean MEPS was 90.6 points, with seven excellent results and one good result. The aim of this study was to highlight the good results of Herbert screw fixation technique in the management of Hahn–Steinthal fractures. [ABSTRACT FROM AUTHOR]

The neurophysiological mechanisms underlying muscle force control for different wrist postures still need to be better understood. To further elucidate these mechanisms, the present study aimed to investigate the effects of wrist posture on the corticospinal excitability by transcranial magnetic stimulation (TMS) of extrinsic (flexor [FCR] and extensor carpi radialis [ECR]) and intrinsic (flexor pollicis brevis (FPB)) muscles at rest and during a submaximal handgrip strength task. Fourteen subjects (24.06 ± 2.28 years) without neurological or motor disorders were included. We assessed how the wrist posture (neutral: 0°; flexed: +45°; extended: −45°) affects maximal handgrip strength (HGSmax) and the motor evoked potentials (MEP) amplitudes during rest and active muscle contractions. HGSmax was higher at 0° (133%) than at −45° (93.6%; p < 0.001) and +45° (73.9%; p < 0.001). MEP amplitudes were higher for the FCR at +45° (83.6%) than at −45° (45.2%; p = 0.019) and at +45° (156%; p < 0.001) and 0° (146%; p = 0.014) than at −45° (106%) at rest and active condition, respectively. Regarding the ECR, the MEP amplitudes were higher at −45° (113%) than at +45° (60.8%; p < 0.001) and 0° (72.6%; p = 0.008), and at −45° (138%) than +45° (96.7%; p = 0.007) also at rest and active conditions, respectively. In contrast, the FPB did not reveal any difference among wrist postures and conditions. Although extrinsic and intrinsic hand muscles exhibit overlapping cortical representations and partially share the same innervation, they can be modulated differently depending on the biomechanical constraints. [ABSTRACT FROM AUTHOR]

Intraoperative neuromonitoring (IONM) during surgical correction of spinal deformity has been shown to reduce iatrogenic injury in pediatric and adult populations. Although motor-evoked potentials (MEP), somatosensory-evoked potentials (SSEP), and electromyography (EMG) have been shown to be highly sensitive and specific in detecting spinal cord and nerve root injuries, their utility in detecting motor and sensory nerve root injury in pediatric high-grade spondylolisthesis (HGS) remains unknown. We aim to assess the diagnostic accuracy and therapeutic impact of unimodal and multimodal IONM in the surgical management of HGS. Retrospective cohort study. Pediatric patients undergoing posterior spinal fusion (PSF) for treatment of HGS. Data on patient demographics, spinopelvic and spondylolisthesis parameters, and the presence of pre-and postoperative neurological deficits were collected. Intraoperative MEP, SSEP, and EMG alerts were recorded. Alert criteria were defined as a change in amplitude of more than 50% for MEP and/or SSEP, with or without change in latency, and more than 10 seconds of sustained EMG activity. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated for each modality and the combination of MEP and SSEP. The 95% confidence intervals (CIs) were calculated using the exact (Clopper-Pearson) method. Fifty-four pediatric patients with HGS undergoing PSF between 2003 and 2021 in a single tertiary center were included. Seventy-two percent (39/54) of patients were female; the average age of patients was 13.7±2.3 years. The sensitivity of MEP in detecting new postoperative neurologic deficit was 92.3% (95% CI [64.0–99.8]), SSEP 77.8% (95% CI [40.0–97.2]), EMG 69.2% (95% CI [38.6–90.9]), and combination MEP and SSEP 100% (95% CI [73.5–100]). The specificity of MEP was 80.0% (95% CI [64.4–91.0]), SSEP 95.1% (95% CI [83.5–99.4]), EMG 65.9% (95% CI [49.4–79.9]), and combination MEP and SSEP 82.9% (95% CI [67.9–92.9]). The accuracy of SSEP was 92.0% (95% CI [80.8%–97.8%]), and the combination of MEP and SSEP was 86.8% (95% CI [74.7%–94.5%]). Twelve (22.2%) patients had a new motor or sensory deficit diagnosed immediately postoperatively. Nine patients made a full recovery, and 3 had some neurologic deficit on final follow-up. Unimodal IONM using SSEP and MEP alone were accurate in diagnosing sensory and motor nerve root injuries, respectively. The diagnostic accuracy in predicting motor and sensory nerve injuries in pediatric HGS improved further with the use of multimodal IONM (combining MEP and SEP). We recommend the utilization of multimodal IONM in all HGS PSF surgeries. [ABSTRACT FROM AUTHOR]

Transcranial magnetic stimulation (TMS) is a flexible, non-invasive technique that involves the production of a brief magnetic field to stimulate the conductive structures of the brain. When TMS is specifically employed as a single- or paired-pulse over the motor cortex, the function and integrity of the descending motor pathways can be assessed through the generation of a motor evoked potential (MEP). Important MEP-derived measures include the motor threshold, MEP amplitude and latency, central motor conduction time, silent period, intracortical inhibition, and intracortical facilitation. These functional measures may have use in individuals with multiple sclerosis (MS), a common chronic autoimmune disorder of the central nervous system, due to their useful diagnostic and prognostic implications. As a representation of excitability and conductivity, TMS measures may have the potential to serve as objective markers of corticospinal tract integrity, which is a major aspect of clinical disability in MS. Additionally, TMS may be employed to help monitor and provide insight on the effects of therapies for patients with MS over a longitudinal timeframe. In this review, we focus on the application of TMS in the context of MS, with an emphasis on the relationship between TMS measures and widely used clinical assessment measures used for patients with MS. [ABSTRACT FROM AUTHOR]

Objective: Considering spinal deformity patients with pre‐operative neurological deficit were associated with more intra‐operative iatrogenic neurological complications than those without, intra‐operative neurophysiological monitoring (IONM) has been used for detecting possible iatrogenic injury timely. However, the IONM waveforms are often unreliable. To analyze the performance of intra‐operative neurophysiological monitoring (IONM) including somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) in patients with pre‐operative neurological deficit undergoing posterior spinal correction surgery, and to identify the high‐risk factors for failed IONM. Methods: Patients with pre‐operative neurological deficit undergoing posterior spinal correction surgery between October 2017 and January 2022 were retrospectively reviewed. The presence or absence of SEP and MEP of target muscles were separately recorded. The P37/N50 latency and amplitude of SEP, and the MEP amplitude were measured. Any IONM alerts were also recorded. The IONM performance was compared among patients with different etiologies, levels responsible for neurological deficit, and strength of IONM‐target muscles. Patients' demographics were analyzed using the descriptive statistics and were presented with mean ± standard deviation. Comparison analysis was performed using χ2‐test and statistically significant difference was defined as p < 0.05. Results: A total of 270 patients (147 males, 123 females) with an average age of 48.4 ± 36.7 years were involved. The SEP records were available in 371 (68.7%) lower extremities while MEP records were available in 418 (77.4%). SEP alerts were reported in 31 lower extremities and MEP alerts in 22, and new neurological deficit at post‐operation was observed in 11. The etiologies of neuromuscular and syndromic indicated relatively lower success rates of IONM, which were 44.1% and 40.5% for SEP, and 58.8% and 59.5% for MEP (p < 0.001). In addition, patients with pre‐operative neurological deficit caused by cervical spine and muscle strength lower than grade 4 suffered from higher risk of failed IONM waveforms (p < 0.001). Conclusion: Patients with pre‐operative neurological deficit suffered from a higher incidence of failed IONM results. The high‐risk for failed IONM waveforms included the neuromuscular and syndromic etiologies, neurological deficit caused by cervical spine, muscle strength lower than grade 4 in patients with pre‐operative neurological deficit undergoing posterior spinal correction surgery. [ABSTRACT FROM AUTHOR]

Chiari malformation type 1 (CM1) includes various congenital anomalies that share ectopia of the cerebellar tonsils lower than the foramen magnum, in some cases associated with syringomyelia or hydrocephalus. CM1 can cause dysfunction of the brainstem, spinal cord, and cranial nerves. This functional alteration of the nervous system can be detected by various modalities of neurophysiological tests, such as brainstem auditory evoked potentials, somatosensory evoked potentials, motor evoked potentials, electromyography and nerve conduction studies of the cranial nerves and spinal roots, as well as brainstem reflexes. The main goal of this study is to review the findings of multimodal neurophysiological examinations in published studies of patients with CM1 and their indication in the diagnosis, treatment, and follow-up of these patients, as well as their utility in intraoperative monitoring. [ABSTRACT FROM AUTHOR]

In light of the development of manned astronautics and the increasing participation of women in space flights, the question of female body adaptation to microgravity conditions becomes relevant. Currently, one of the important directions in this issue is to study the effects of support withdrawal as a factor of weightlessness on the human sensorimotor system. Dry Immersion is one of the well-known ground-based models, which adequately reproduces the main physiological effects of space flight. The aim of this study was to evaluate the changes in motor evoked potentials of the lower leg gravity-dependent muscles in women after a 5-day Dry Immersion. We analyzed evoked responses to transcranial and trans-spinal magnetic stimulation. In this method, areas of interest (the motor cortex and lumbosacral thickening of the spinal cord) are stimulated with an electromagnetic stimulus. The experiment was conducted with the participation of 16 healthy female volunteers with a natural menstrual cycle. The thresholds, amplitudes, and latencies of motor potentials evoked by magnetic stimulation were assessed. We showed that 5-day exposure to support withdrawal leads to a decrease in motor-evoked potential thresholds and central motor conduction time, although changes in motor response amplitudes were ambiguous. The data obtained correspond to the results of previous research on Dry Immersion effects on the sensorimotor system in men. [ABSTRACT FROM AUTHOR]

The relationships between the results of pre- and intraoperative motor evoked potential recordings during neuromonitoring and whether idiopathic scoliosis (IS) surgical correction improves the spinal efferent transmission have not been specified in detail. This study aims to compare the results of surface-recorded electromyography (EMG), electroneurography (ENG, M, and F-waves), and especially motor evoked potential (MEP) recordings from tibialis anterior muscle (TA) bilaterally in 353 girls with right idiopathic scoliosis (types 1–3 according to Lenke classification). It has not yet been documented whether the results of MEP recordings induced by transcranial single magnetic stimulus (TMS, pre- and postoperatively) and trains of electrical stimuli (TES; intraoperatively in T0—before surgery, T1—after pedicle screws implantation, and T2—after scoliosis curvature distraction and derotation following two-rod implantation) can be compared for diagnostic verification of the improvement of spinal cord neural transmission. We attempted to determine whether the constant level of optimal anesthesia during certain surgical steps of scoliosis treatment affects the parameters of MEPs recorded during neuromonitoring procedures. No neurological deficits have been observed postoperatively. The values of amplitudes but not latencies in MEP recordings evoked with TMS in IS patients compared before and after surgery indicated a slight improvement in efferent neural transmission. The results of all neurophysiological studies in IS patients were significantly asymmetrical and recorded worse on the concave side, suggesting greater neurological motor deficits at p = 0.04. The surgeries brought significant improvement (p = 0.04) in the parameters of amplitudes of sEMG recordings; however, the consequences of abnormalities in the activity of TA motor units were still reflected. ENG study results showed the symptoms of the axonal-type injury in peroneal motor fibers improving only on the concave side at p = 0.04, in parallel with F-wave parameters, which suggests that derotation and distraction might result in restoring the proper relations of the lumbar ventral roots in the spinal central canal, resembling their decompression. There were no significant differences detected in the amplitudes or latencies of MEPs induced with TMS or TES when comparing the parameters recorded preoperatively and intraoperatively in T0. The amplitudes of TES-evoked MEPs increased gradually at p = 0.04 in the subsequent periods (T1 and T2) of observation. A reduction in MEP latency at p = 0.05 was observed only at the end of the IS surgery. Studies on the possible connections between the level of anesthesia fluctuations and the required TMS stimulus strength, as well as the MEP amplitude changes measured in T0–T2, revealed a lack of relationships. These might not be the factors influencing the efferent transmission in spinal pathways beside the surgical procedures. Pre- (TMS-evoked) and intraoperative (TES-evoked) recordings are reliable for evaluating the patient's neurological status before and during surgical scoliosis correction procedures. An increase in MEP amplitude parameters recorded on both sides after scoliosis surgery proves the immediate improvement of the total efferent spinal cord transmission. Considering comparative pre- and postoperative sEMG and ENG recordings, it can be concluded that surgeries might directly result in additional lumbar ventral root decompression. We can conclude that MEP parameter changes are determined by the surgery procedures during neuromonitoring, not the anesthesia conditions if they are kept stable, which influences a decrease in the number of false-positive neuromonitoring warnings. [ABSTRACT FROM AUTHOR]