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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]

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]

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]

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]

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

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.

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]

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]

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]

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]

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]

Mirror neuron research has come a long way from their discovery in primates to modern experiments in humans. However, many methodological questions remain regarding the method and timing of stimulus presentation in such studies. What is the optimal way to present motor stimuli? Is it possible to evaluate the temporal dynamics of the mirror neuron effect using transcranial magnetic stimulation at defined time points? The study reported here examined different types of stimulus presentation (photos and videos of hand movements) combined with single-pulse transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) of the dominant hemisphere in different time windows (0, 320, 640 msec). Motor evoked potentials (MEP) were recorded from the first dorsal interosseous (FDI) and the abductor digiti minimi (ADM) muscles using adhesive electrodes placed on the hand muscles in 11 healthy subjects at rest with the hands positioned orthogonally during observation of visual stimuli in three different presentation conditions. The study results showed that video stimuli produced the strongest mirror effect when the TMS stimulus was presented 320 msec after presentation of the movement. This effect was specific to particular muscles. The data obtained here will help to formulate an optimal protocol for studying the mirror neuron system in humans and will contribute to its further clinical use in investigations and rehabilitation. [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).

Introduction: Repetitive transcranial magnetic stimulation (rTMS) is used to induce long-lasting changes (aftereffects) in cortical excitability, which are often measured via single-pulse TMS (spTMS) over the motor cortex eliciting motor-evoked potentials (MEPs). rTMS includes various protocols, such as theta-burst stimulation (TBS), paired associative stimulation (PAS), and continuous rTMS with a fixed frequency. Nevertheless, subsequent aftereffects of rTMS are variable and seem to fail repeatability. We aimed to summarize standard rTMS procedures regarding their test-retest reliability. Hereby, we considered influencing factors such as the methodological quality of experiments and publication bias. Methods: We conducted a literature search via PubMed in March 2023. The inclusion criteria were the application of rTMS, TBS, or PAS at least twice over the motor cortex of healthy subjects with measurements of MEPs via spTMS as a dependent variable. The exclusion criteria were measurements derived from the non-stimulated hemisphere, of non-hand muscles, and by electroencephalography only. We extracted test-retest reliability measures and aftereffects from the eligible studies. With the Rosenthal fail-safe N, funnel plot, and asymmetry test, we examined the publication bias and accounted for influential factors such as the methodological quality of experiments measured with a standardized checklist. Results: A total of 15 studies that investigated test-retest reliability of rTMS protocols in a total of 291 subjects were identified. Reliability measures, i.e., Pearson's r and intraclass correlation coefficient (ICC) applicable from nine studies, were mainly in the small to moderate range with two experiments indicating good reliability of 20 Hz rTMS (r = 0.543) and iTBS (r = 0.55). The aftereffects of rTMS procedures seem to follow the heuristics of respective inhibition or facilitation, depending on the protocols' frequency, and application pattern. There was no indication of publication bias and the influence of methodological quality or other factors on the reliability of rTMS. Conclusion: The reliability of rTMS appears to be in the small to moderate range overall. Due to a limited number of studies reporting test-retest reliability values and heterogeneity of dependent measures, we could not provide generalizable results. We could not identify any protocol as superior to the others. [ABSTRACT FROM AUTHOR]

Aims: Motor evoked potentials (MEP) elicited by transcranial magnetic stimulation (TMS) over the primary motor cortex are used as a neurophysiological marker of cortical excitability in clinical and scientific practice. Though, the reliability of this outcome parameter has not been clarified. Using a systematic approach, this work reviews and critically appraises studies on the reliability of MEP outcome parameters derived from hand muscles of healthy subjects and gives a proposal for most reliable TMS practice. Methods: A systematic literature research was performed in PubMed, according to the PRISMA guidelines. Articles published up to March 2023 that were written in English, conducted repeated measurements from hand muscles of healthy subjects and reliability analysis were included. The risk of publication bias was determined. Two authors conducted the literature search and rated the articles in terms of eligibility and methodological criteria with standardized instruments. Frequencies of the checklist criteria were calculated and inter-rater reliability of the rating procedure was determined. Reliability and stimulation parameters were extracted and summarized in a structured way to conclude best-practice recommendation for reliable measurements. Results: A total of 28 articles were included in the systematic review. Critical appraisal of the studies revealed methodological heterogeneity and partly contradictory results regarding the reliability of outcome parameters. Inter-rater reliability of the rating procedure was almost perfect nor was there indication of publication bias. Identified studies were grouped based on the parameter investigated: number of applied stimuli, stimulation intensity, reliability of input-output curve parameters, target muscle or hemisphere, inter-trial interval, coil type or navigation and waveform. Conclusion: The methodology of studies on TMS is still subject to heterogeneity, which could contribute to the partly contradictory results. According to the current knowledge, reliability of the outcome parameters can be increased by adjusting the experimental setup. Reliability of single pulse MEP measurement could be optimized by using (1) at least five stimuli per session, (2) a minimum of 110% resting motor threshold as stimulation intensity, (3) a minimum of 4 s intertrial interval and increasing the interval up to 20 s, (4) a figure-of-eight coil and (5) a monophasic waveform. MEPs can be reliably operationalized. [ABSTRACT FROM AUTHOR]

Over the past decades, among all the non-invasive brain stimulation (NIBS) techniques, those aiming for neuromodulatory protocols have gained special attention. The traditional neurophysiological outcome to estimate the neuromodulatory effect is the motor evoked potential (MEP), the impact of NIBS techniques is commonly estimated as the change in MEP amplitude. This approach has several limitations: first, the use of MEP limits the evaluation of stimulation to the motor cortex excluding all the other brain areas. Second, MEP is an indirect measure of brain activity and is influenced by several factors. To overcome these limitations several studies have used new outcomes to measure brain changes after neuromodulation techniques with the concurrent use of transcranial magnetic stimulation (TMS) and electroencephalogram (EEG). In the present review, we examine studies that use TMS-EEG before and after a single session of neuromodulatory TMS. Then, we focused our literature research on the description of the different metrics derived from TMS-EEG to measure the effect of neuromodulation. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

Syringomyelia can be associated with multiple etiologies. The treatment of the underlying causes is first-line therapy; however, a direct approach to the syrinx is accepted as rescue treatment. Any direct intervention on the syrinx requires a myelotomy, posing a significant risk of iatrogenic spinal cord (SC) injury. Intraoperative neurophysiological monitoring (IONM) is crucial to detect and prevent surgically induced damage in neural SC pathways. We retrospectively reviewed the perioperative and intraoperative neurophysiological data and perioperative neurological examinations in ten cases of syringomyelia surgery. All the monitored modalities remained stable throughout the surgery in six cases, correlating with no new postoperative neurological deficits. In two patients, significant transitory attenuation, or loss of motor evoked potentials (MEPs), were observed and recovered after a corrective surgical maneuver, with no new postoperative deficits. In two cases, a significant MEP decrement was noted, which lasted until the end of the surgery and was associated with postoperative weakness. A transitory train of neurotonic electromyography (EMG) discharges was reported in one case. The surgical plan was adjusted, and the patient showed no postoperative deficits. The dorsal nerve roots were stimulated and identified in the seven cases where the myelotomy was performed via the dorsal root entry zone. Dorsal column mapping guided the myelotomy entry zone in four of the cases. In conclusion, multimodal IONM is feasible and reliable and may help prevent iatrogenic SC injury during syringomyelia surgery. [ABSTRACT FROM AUTHOR]

Knee osteoarthritis (OA) is a painful condition characterized by joint and bone changes. A growing number of studies suggest that these changes only partially explain the pain experienced by individuals with OA. The purpose of the current study was to evaluate if corticospinal and bulbospinal projection measurements were interrelated in patients with knee OA, and to explore the relationship between these neurophysiological measures and temporal summation (excitatory mechanisms of pain) on one hand, and clinical symptoms on the other. Twenty-eight (28) patients with knee OA were recruited. Corticospinal projections were measured using transcranial magnetic stimulation, while bulbospinal projections were evaluated with a conditioned pain modulation (CPM) protocol using a counter-irritation paradigm. Validated questionnaires were used to document clinical and psychological manifestations. All participants suffered from moderate to severe pain. There was a positive association between corticospinal excitability and the effectiveness of the CPM (rs = 0.67, p = 0.01, n = 13). There was also a positive relationship between pain intensity and corticospinal excitability (rs = 0.45, p = 0.03, n = 23), and between pain intensity and temporal summation (rs = 0.58, p = 0.01, n = 18). The results of this study highlight some of the central nervous system changes that could be involved in knee OA and underline the importance of interindividual variability to better understand and explain the semiology and pathophysiology of knee OA. [ABSTRACT FROM AUTHOR]

The long history of regeneration nerve research indicates many clinical problems with surgical reconstruction to be resolved. One of the promising surgical techniques in specific clinical conditions is end-to-side neurorrhaphy (ETS), described and then repeated with different efficiency in the 1990s of the twentieth century. There are no reliable data on the quality of recipient nerve regeneration, possible donor nerve damage, and epineural window technique necessary to be performed. This research attempts to evaluate the possible regeneration after end-to-side neurorrhaphy, its quality, potential donor nerve damage, and the influence of epineural windows on regeneration efficiency. Forty-five female Wistar rats were divided into three equal groups, and various surgical technics were applied: A—ETS without epineural window, B—ETS with epineural window, and C—free graft reconstruction. The right peroneal nerve was operated on, and the tibial nerve was selected as a donor. After 24 weeks, the regeneration was evaluated by (1) footprint analysis every two weeks with PFI (peroneal nerve function index), TFI (tibial nerve function index), and SFI (sciatic nerve function index) calculations; (2) the amplitude and latency measurements of motor evoked potentials parameters recorded on both sides of the peroneal and tibial nerves when electroneurography with direct sciatic nerve electrical stimulation and indirect magnetic stimulation were applied; (3) histomorphometry with digital conversion of a transverse semithin nerve section, with axon count, fibers diameter, and calculation of axon area with a semiautomated method were performed. There was no statistically significant difference between the groups investigated in all the parameters. The functional indexes stabilized after eight weeks (PFI) and six weeks (TFI and SFI) and were positively time related. The lower amplitude of tibial nerve potential in groups A and B was proven compared to the non-operated side. Neurophysiological parameters of the peroneal nerve did not differ significantly. Histomorphometry revealed significantly lower diameter and area of axons in operated peroneal nerves compared to non-operated nerves. The axon count was at a normal level in every group. Tibial nerve parameters did not differ from non-operated values. Regeneration of the peroneal nerve after ETS was ascertained to be at the same level as in the case of free graft reconstruction. Peroneal nerves after ETS and free graft reconstruction were ascertained to have a lower diameter and area than non-operated ones. The technique of an epineural window does not influence the regeneration result of the peroneal nerve. The tibial nerve motor evoked potentials were characterized by lower amplitudes in ETS groups, which could indicate axonal impairment. [ABSTRACT FROM AUTHOR]

Summary: The influence of general anaesthetic agents on intra‐operative neurophysiological monitoring in neonates and infants has rarely been reported. Propofol‐based anaesthesia is recommended to avoid suppression of neurophysiological monitoring. However, the administration of propofol in children undergoing prolonged procedures, especially those younger than six months, should be carefully controlled due to the potential risk of propofol infusion syndrome. Adding a small dose of inhalational anaesthetic can be an option to reduce propofol requirements. Recent guidelines in Japan suggest limiting inhalational anaesthetics to less than 0.5 minimum alveolar concentrations when co‐administered with low‐dose propofol during intra‐operative neuromonitoring. However, there is still insufficient evidence regarding the impact of sevoflurane on neurophysiological monitoring when co‐administered with propofol in infants. This report describes a case of a three‐month‐old infant undergoing spinal lipoma resection in which there was a dramatic suppression of neurophysiological monitoring with the addition of 0.35–0.45% sevoflurane to propofol‐based anaesthesia. [ABSTRACT FROM AUTHOR]

Keywords: Motor evoked potentials; Midazolam; Remifentanil; Total intravenous anesthesia; Case report EN Motor evoked potentials Midazolam Remifentanil Total intravenous anesthesia Case report 815 817 3 10/04/23 20231001 NES 231001 To the Editor: Although propofol represents a "gold standard" from anesthetic drugs for total intravenous anesthesia (TIVA) with intraoperative neurophysiological monitoring (IONM), the anesthetic team should have an alternative plan in rare cases when the propofol is contraindicated, and remimazolam, a new ultra-short-acting benzodiazepine, is not available [[1]]. Remimazolam-based anesthesia was described during surgery with IONM and in pediatric surgery with MEP monitoring. [Extracted from the article]

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.

IntroductionRepetitive transcranial magnetic stimulation (rTMS) is used to induce long-lasting changes (aftereffects) in cortical excitability, which are often measured via single-pulse TMS (spTMS) over the motor cortex eliciting motor-evoked potentials (MEPs). rTMS includes various protocols, such as theta-burst stimulation (TBS), paired associative stimulation (PAS), and continuous rTMS with a fixed frequency. Nevertheless, subsequent aftereffects of rTMS are variable and seem to fail repeatability. We aimed to summarize standard rTMS procedures regarding their test–retest reliability. Hereby, we considered influencing factors such as the methodological quality of experiments and publication bias.MethodsWe conducted a literature search via PubMed in March 2023. The inclusion criteria were the application of rTMS, TBS, or PAS at least twice over the motor cortex of healthy subjects with measurements of MEPs via spTMS as a dependent variable. The exclusion criteria were measurements derived from the non-stimulated hemisphere, of non-hand muscles, and by electroencephalography only. We extracted test–retest reliability measures and aftereffects from the eligible studies. With the Rosenthal fail-safe N, funnel plot, and asymmetry test, we examined the publication bias and accounted for influential factors such as the methodological quality of experiments measured with a standardized checklist.ResultsA total of 15 studies that investigated test–retest reliability of rTMS protocols in a total of 291 subjects were identified. Reliability measures, i.e., Pearson's r and intraclass correlation coefficient (ICC) applicable from nine studies, were mainly in the small to moderate range with two experiments indicating good reliability of 20 Hz rTMS (r = 0.543) and iTBS (r = 0.55). The aftereffects of rTMS procedures seem to follow the heuristics of respective inhibition or facilitation, depending on the protocols' frequency, and application pattern. There was no indication of publication bias and the influence of methodological quality or other factors on the reliability of rTMS.ConclusionThe reliability of rTMS appears to be in the small to moderate range overall. Due to a limited number of studies reporting test–retest reliability values and heterogeneity of dependent measures, we could not provide generalizable results. We could not identify any protocol as superior to the others.

AimsMotor evoked potentials (MEP) elicited by transcranial magnetic stimulation (TMS) over the primary motor cortex are used as a neurophysiological marker of cortical excitability in clinical and scientific practice. Though, the reliability of this outcome parameter has not been clarified. Using a systematic approach, this work reviews and critically appraises studies on the reliability of MEP outcome parameters derived from hand muscles of healthy subjects and gives a proposal for most reliable TMS practice.MethodsA systematic literature research was performed in PubMed, according to the PRISMA guidelines. Articles published up to March 2023 that were written in English, conducted repeated measurements from hand muscles of healthy subjects and reliability analysis were included. The risk of publication bias was determined. Two authors conducted the literature search and rated the articles in terms of eligibility and methodological criteria with standardized instruments. Frequencies of the checklist criteria were calculated and inter-rater reliability of the rating procedure was determined. Reliability and stimulation parameters were extracted and summarized in a structured way to conclude best-practice recommendation for reliable measurements.ResultsA total of 28 articles were included in the systematic review. Critical appraisal of the studies revealed methodological heterogeneity and partly contradictory results regarding the reliability of outcome parameters. Inter-rater reliability of the rating procedure was almost perfect nor was there indication of publication bias. Identified studies were grouped based on the parameter investigated: number of applied stimuli, stimulation intensity, reliability of input-output curve parameters, target muscle or hemisphere, inter-trial interval, coil type or navigation and waveform.ConclusionThe methodology of studies on TMS is still subject to heterogeneity, which could contribute to the partly contradictory results. According to the current knowledge, reliability of the outcome parameters can be increased by adjusting the experimental setup. Reliability of single pulse MEP measurement could be optimized by using (1) at least five stimuli per session, (2) a minimum of 110% resting motor threshold as stimulation intensity, (3) a minimum of 4 s inter-trial interval and increasing the interval up to 20 s, (4) a figure-of-eight coil and (5) a monophasic waveform. MEPs can be reliably operationalized.

Over the past decades, among all the non-invasive brain stimulation (NIBS) techniques, those aiming for neuromodulatory protocols have gained special attention. The traditional neurophysiological outcome to estimate the neuromodulatory effect is the motor evoked potential (MEP), the impact of NIBS techniques is commonly estimated as the change in MEP amplitude. This approach has several limitations: first, the use of MEP limits the evaluation of stimulation to the motor cortex excluding all the other brain areas. Second, MEP is an indirect measure of brain activity and is influenced by several factors. To overcome these limitations several studies have used new outcomes to measure brain changes after neuromodulation techniques with the concurrent use of transcranial magnetic stimulation (TMS) and electroencephalogram (EEG). In the present review, we examine studies that use TMS-EEG before and after a single session of neuromodulatory TMS. Then, we focused our literature research on the description of the different metrics derived from TMS-EEG to measure the effect of neuromodulation.