Motor Evoked Potentials Latency Research Articles

A bispectral index guided comparative evaluation of dexmedetomidine as an adjuvant to propofol-based total intravenous anaesthesia in spine surgeries done under motor-evoked potential monitoring

BackgroundThe anaesthetic agents can affect the quality of motor-evoked potential intraoperatively as they inhibit synaptic transmission. Intravenous anaesthetics suppress motor-evoked potential lesser than inhalational agents, so total intravenous anaesthesia or a combination of intravenous with minimal inhalational anaesthetic supplementation is used when motor-evoked potential is monitored. Motor-evoked potential can get depressed at high doses of propofol required to maintain surgical depth, hence, adjuvant agents like dexmedetomidine that maintain anaesthetic depth without affecting the motor-evoked potential are often required. This study was a prospective non-randomized and comparative study (quasi-experimental) assigned into two groups of 64 each, labelled as the propofol group (group P) and Propofol + dexmedetomidine group (group PD). The primary objective of our study was to compare the total dose reduction of propofol with the addition of dexmedetomidine and their interference with motor-evoked potential readings. The secondary objective was to assess the hemodynamic changes, changes in amplitude and latency of motor-evoked potential, and complications if any.ResultsThe mean total dose of propofol consumed in our study was 502.81 ± 71.01 mg in group propofol( P) and 392.18 ± 59.00 mg in group propofol + dexmedetomidine (PD). Moreover, the mean total dose of propofol (mg) was significantly less used in group PD. Intraoperative hemodynamic stability, no difference in amplitude and latency for motor-evoked potential, and only significant bradycardia in group propofol + dexmedetomidine (PD).ConclusionsDexmedetomidine can be successfully used in propofol-based total intravenous anaesthesia for motor-evoked potential monitoring in spine surgeries, but it is better to maintain stable hemodynamics with a significant reduction of the mean dose of propofol.

High-definition transcranial direct current stimulation for upper extremity rehabilitation in moderate-to-severe ischemic stroke: a pilot study.

Previous studies found that post-stroke motor impairments are associated with damage to the lesioned corticospinal tract (CST) and hyperexcitability of the contralesional cortico-reticulospinal tract (CRST). This proof-of-concept study aims to develop a non-invasive brain stimulation protocol that facilitates the lesioned CST and inhibits the contralesional CRST to improve upper extremity rehabilitation in individuals with moderate-to-severe motor impairments post-stroke. Fourteen individuals (minimum 3 months post ischemic stroke) consented. Physician decision of the participants baseline assessment qualified eight to continue in a randomized, double-blind cross-over pilot trial (ClinicalTrials.gov Identifier: NCT05174949) with: (1) anodal high-definition transcranial direct stimulation (HD-tDCS) over the ipsilesional primary motor cortex (M1), (2) cathodal HD-tDCS over contralesional dorsal premotor cortex (PMd), (3) sham stimulation, with a two-week washout period in-between. Subject-specific MR images and computer simulation were used to guide HD-tDCS and verified by Transcranial Magnetic Stimulation (TMS) induced Motor Evoked Potential (MEP). The motor behavior outcome was evaluated by an Fugl-Meyer Upper Extremity score (primary outcome measure) and the excitability of the ipslesoinal CST and contralesional CRST was determined by the change of MEP latencies and amplitude (secondary outcome measures). The baseline ipsilesional M1 MEP latency and amplitude were correlated with FM-UE. FM-UE scores were improved post HD-tDCS, in comparison to sham stimulation. Both anodal and cathodal HD-tDCS reduced the latency of the ipsilesional M1 MEP. The contralesional PMd MEP disappeared/delayed after HD-tDCS. These results suggest that HD-tDCS could improve the function of the lesioned corticospinal tract and reduce the excitability of the contralesional cortico-reticulospinal tract, thus, improving motor function of the upper extremity in more severely impaired individuals.

Clinical utility of trans-sacral magnetic stimulation-evoked sphincter potentials and high-density electromyography in pelvic floor assessment: Technical evaluation.

Faecal incontinence is common and of multifactorial aetiologies, yet current diagnostic tools are unable to assess nerve and sphincter function objectively. We developed an anorectal high-density electromyography (HD-EMG) probe to evaluate motor-evoked potentials induced via trans-sacral magnetic stimulation (TSMS). Anorectal probes with an 8 × 8 array of electrodes spaced 1 cm apart were developed for recording HD-EMG of the external anal sphincter. These HD-EMG probes were used to map MEP amplitudes and latencies evoked via TSMS delivered through the Magstim Rapid2 (MagStim Company). Patients undergoing pelvic floor investigations were recruited for this IDEAL Stage 2a pilot study. Eight participants (median age 49 years; five female) were recruited. Methodological viability, safety and diagnostic workflow were established. The test was well tolerated with median discomfort scores ≤2.5/10, median pain scores ≤1/10 and no adverse events. Higher Faecal Incontinence Severity Index scores correlated with longer MEP latencies (r = 0.58, p < 0.001) and lower MEP amplitudes (r = -0.32, p = 0.046), as did St. Mark's Incontinence Scores with both MEP latencies (r = 0.49, p = 0.001) and MEP amplitudes (r = -0.47, p = 0.002). This HD-EMG probe in conjunction with TSMS presents a novel diagnostic tool for anorectal function assessment. Spatiotemporal assessment of magnetically stimulated MEPs correlated well with symptoms and offers a feasible, safe and patient-tolerable method of evaluating pudendal nerve and external anal sphincter function. Further clinical development and evaluation of these techniques is justified.

Shortened Motor Evoked Potential Latency in the Epileptic Hemisphere of Children With Focal Epilepsy.

Motor evoked potential (MEP) amplitude and latency are acquired routinely during neuronavigated transcranial magnetic stimulation, a method of functional mapping of the motor cortex before epilepsy surgery. Although MEP amplitude is routinely used to generate a motor map, MEP latency in patients with focal epilepsy has not been studied systematically. Given that epilepsy may alter myelination, we tested whether intrinsic hand muscle MEPs obtained from the hemisphere containing a seizure focus differ in latency from MEPs collected from the opposite hemisphere. Latencies of abductor pollicis brevis MEPs were obtained during routine motor mapping by neuronavigated transcranial magnetic stimulation in children with intractable, unihemispheric focal epilepsy. The primary motor cortex was stimulated bilaterally in all cases. Only data from patients without a lesion involving the corticospinal tract were included. We tested whether abductor pollicis brevis MEP latency varied as a function of seizure focus lateralization. In the 17 patients who met the inclusion criteria, the mean latency of MEPs with amplitudes in the top and bottom quartiles was shorter in the epileptic hemisphere. Interhemispheric latency difference was greater in patients with lesional epilepsy than in those with nonlesional epilepsy (0.7 ± 0.4 vs. 0.1 ± 0.6 milliseconds, P = 0.02). Motor evoked potential latency was shortened in the epileptic hemisphere of children with focal epilepsy.

Transcutaneous cervical vagus nerve stimulation improved motor cortex excitability in healthy adults: a randomized, single-blind, self-crossover design study.

To investigate the effect of transcutaneous cervical vagus nerve stimulation (tcVNS) on motor cortex excitability in healthy adults. Twenty eight healthy subjects were assigned to receive real and sham tcVNS for 30 min. The interval between the real and sham conditions was more than 24 h, and the sequence was random. The central and peripheral motor-evoked potential (MEP) of the right first dorsal interosseous (FDI) muscle was measured by transcranial magnetic stimulation (TMS) before and after stimulation. MEP latency, MEP amplitude and rest motor threshold (rMT) were analyzed before and after stimulation. MEP amplitude, MEP latency and rMT had significant interaction effect between time points and conditions (p < 0.05). After real stimulation, the MEP amplitude was significantly increased (p < 0.001). MEP latency (p < 0.001) and rMT (p = 0.006) was decreased than that of baseline. The MEP amplitude on real condition was higher than that of sham stimulation after stimulation (p = 0.027). The latency after the real stimulation was significantly shorter than that after sham stimulation (p = 0.005). No significantly difference was found in rMT after stimulation between real and sham conditions (p > 0.05). tcVNS could improve motor cortex excitability in healthy adults.

The Importance of Motor Evoked Potential Findings in Acute-Subacute Odontoid Dislocations

Background:&#x0D; Motor evoked potentials (MEPs) using transcranial magnetic stimulation (TMS) may give a functional assessment of corticospinal conduction. The aim of this study is to confirm the value of MEPs for the assessment of the dysfunction in spinal cord transmission in patients with clinically minimally symptomatic or asymptomatic and acute-subacute odontoid pathologies.&#x0D; Methods:&#x0D; We measured the MEPs of five cases with acute-subacute odontoid dislocations by using TMS. Demografic features, neurological examinations and neuroimaging findings of the patients have also been noted.&#x0D; Results:&#x0D; The CMCTs and MEP latencies after cortical stimulus of all patients with acute-subacute odontoid dislocation prolonged bilaterally. Additionally, MEP amplitudes were observed decreased in all cases.&#x0D; Conclusions:&#x0D; MEP is quite valuable to show involvement in clinically and radiologically silent cases. Our findings in acute-subacute cases without myelopathy showed us that the CMCTs were prolonged especially in the cases who had motor defisits but also in asymptomatic cases.

Comparison of Motor Evoked Potentials Neuromonitoring Following Pre- and Postoperative Transcranial Magnetic Stimulation and Intraoperative Electrical Stimulation in Patients Undergoing Surgical Correction of Idiopathic Scoliosis.

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.

Acute non invasive brain stimulation improves performances in volleyball players

ObjectivesThe ability to redirect one's attention in response to various environmental situations is a crucial aspect of selective attention in team sports. Thus, the aim of this study was to investigate whether repetitive transcranial magnetic stimulation (rTMS) in volleyball players can improve Posner test response and cortical excitability. This study had a double-blinded (participant and evaluator) matched-pair experimental design. MethodsTwenty right-handed female volleyball players were recruited for the study and randomly assigned to either the active rTMS group (n = 10) or the sham stimulation group (n = 10). The stimulation was performed in one session with 10 Hz, 80% of the resting motor threshold (RMT), 5 s of stimulation, and 15 s of rest, for a total of 1,500 pulses. Before and after stimulation, the Posner test and cortical excitability were evaluated. ResultsThe significant finding of this paper was that 10 Hz rTMS to the DLPFC seemed to improve Posner test response, and also resulted in a significantly decreased RMT and MEP latency of the ipsilateral motor cortex. After stimulation, the active group showed a significant decrease in the percentage of errors in the Posner test. Moreover, active group showed faster RT after rTMS, suggesting that HF stimulation could enhance performance. Additionally, significant differences in RMT emerged in the active rTMS group after stimulation, while no differences were observed in MEP latency and MEP amplitude. ConclusionIn conclusion, we believe that these results may be of great interest to the scientific community and could have practical implications in the future.

Transcranial Magnetic Stimulation Measures, Pyramidal Score on Expanded Disability Status Scale and Magnetic Resonance Imaging of Corticospinal Tract in Multiple Sclerosis.

Probing the cortic ospinal tract integrity by transcranial magnetic stimulation (TMS) could help to understand the neurophysiological correlations of multiple sclerosis (MS) symptoms. Therefore, the study objective was, first, to investigate TMS measures (resting motor threshold-RMT, motor evoked potential (MEP) latency, and amplitude) of corticospinal tract integrity in people with relapsing-remitting MS (pwMS). Then, the study examined the conformity of TMS measures with clinical disease-related (Expanded Disability Status Scale-EDSS) and magnetic resonance imaging (MRI) results (lesion count) in pwMS. The e-field navigated TMS, MRI, and EDSS data were collected in 23 pwMS and compared to non-clinical samples. The results show that pwMS differed from non-clinical samples in MEP latency for upper and lower extremity muscles. Also, pwMS with altered MEP latency (prolonged or absent MEP response) had higher EDSS, general and pyramidal, functional scores than pwMS with normal MEP latency finding. Furthermore, the RMT intensity for lower extremity muscles was predictive of EDSS functional pyramidal scores. TMS/MEP latency findings classified pwMS as the same as EDSS functional pyramidal scores in 70-83% of cases and were similar to the MRI results, corresponding to EDSS functional pyramidal scores in 57-65% of cases. PwMS with altered MEP latency differed from pwMS with normal MEP latency in the total number of lesions in the brain corticospinal and cervical corticospinal tract. The study provides preliminary results on the correspondence of MRI and TMS corticospinal tract evaluation results with EDSS functional pyramidal score results in MS.

Variation of corticospinal excitability during kinesthetic illusion induced by musculotendinous vibration.

Despite being studied for more than 50 years, the neurophysiological mechanisms underlying vibration (VIB)-induced kinesthetic illusions are still unclear. The aim of this study was to investigate how corticospinal excitability tested by transcranial magnetic stimulation (TMS) is modulated during VIB-induced illusions. Twenty healthy adults received vibration over wrist flexor muscles (80 Hz, 1 mm, 10 s). TMS was applied over the primary motor cortex representation of wrist extensors at 120% of resting motor threshold in four random conditions (10 trials/condition): baseline (without VIB), 1 s, 5 s, and 10 s after VIB onset. Means of motor-evoked potential (MEP) amplitudes and latencies were calculated. Statistical analysis found a significant effect of conditions (stimulation timings) on MEP amplitudes (P = 0.035). Paired-comparisons demonstrated lower corticospinal excitability during VIB at 1 s compared with 5 s (P = 0.025) and 10 s (P = 0.003), although none of them differed from baseline values. Results suggest a time-specific modulation of corticospinal excitability in muscles antagonistic to those vibrated, i.e., muscles involved in the perceived movement. An early decrease of excitability was observed at 1 s followed by a stabilization of values near baseline at subsequent time points. At 1 s, the illusion is not yet perceived or not strong enough to upregulate corticospinal networks coherent with the proprioceptive input. Spinal mechanisms, such as reciprocal inhibition, could also contribute to lower the corticospinal drive of nonvibrated muscles in short period before the illusion emerges. Our results suggest that neuromodulatory effects of VIB are likely time-dependent, and that future work is needed to further investigate underlying mechanisms.NEW & NOTEWORTHY The modulation of corticospinal excitability when perceiving a vibration (VIB)-induced kinesthetic illusion evolves dynamically over time. This modulation might be linked to the delayed occurrence and progressive increase in strength of the illusory perception in the first seconds after VIB start. Different spinal/cortical mechanisms could be at play during VIB, depending on the tested muscle, presence/absence of an illusion, and the specific timing at which corticospinal drive is tested pre/post VIB.

Nerve excitability test and lead toxicity: a case-control study

BackgroundAlthough conventional electrophysiological parameters have been proposed as clinical indicators for monitoring lead neuropathies, their correlations with blood lead level are weak. In this study, we investigated the applicability of nerve excitability tests (NETs) to evaluate lead intoxication.MethodsFourteen workers who were exposed to lead with an elevated blood level ranging from 17.8 to 64.9 µg/dL and 20 healthy controls with similar ages and body heights were enrolled. Both workers and controls underwent nerve conduction studies (NCSs), motor evoked potentials (MEPs) with transcranial magnetic stimulation (TMS), and NETs.ResultsNCSs showed prolonged distal latencies and decreased motor nerve conduction velocity of median nerves in the workers but without significant correlation to blood lead level (BLL). Significantly prolonged MEP latency was observed in the workers (+ 6 ms). NETs demonstrated hyperpolarized resting membrane potentials in stimulus-response curves and changes in the property of potassium channels under a hyperpolarized current in threshold electrotonus, implying that lead hyperpolarized nerves by interfering with potassium channels. NETs also showed a better correlation with BLL than conventional electrophysiological parameters.ConclusionsAxonal hyperpolarization and central conduction delay are more apparently reflecting elevated BLL than NCS. NET may have the potential for early detection of lead neuropathy.

Effects of transcranial magnetic stimulation (TMS) current direction and pulse waveform on cortico-cortical connectivity: A registered report TMS-EEG study.

Transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) are a promising proxy for measuring effective connectivity, that is, the directed transmission of physiological signals along cortico-cortical tracts, and for developing connectivity-based biomarkers. A crucial point is how stimulation parameters may affect TEPs, as they may contribute to the general variability of findings across studies. Here, we manipulated two TMS parameters (i.e. current direction and pulse waveform) while measuring (a) an early TEP component reflecting contralateral inhibition of motor areas, namely, M1-P15, as an operative model of interhemispheric cortico-cortical connectivity, and (b) motor-evoked potentials (MEP) for the corticospinal pathway. Our results showed that these two TMS parameters are crucial to evoke the M1-P15, influencing its amplitude, latency, and replicability. Specifically, (a) M1-P15 amplitude was strongly affected by current direction in monophasic stimulation; (b) M1-P15 latency was significantly modulated by current direction for monophasic and biphasic pulses. The replicability of M1-P15 was substantial for the same stimulation condition. At the same time, it was poor when stimulation parameters were changed, suggesting that these factors must be controlled to obtain stable single-subject measures. Finally, MEP latency was modulated by current direction, whereas non-statistically significant changes were evident for amplitude. Overall, our study highlights the importance of TMS parameters for early TEP responses recording and suggests controlling their impact in developing connectivity biomarkers from TEPs. Moreover, these results point out that the excitability of the corticospinal tract, which is commonly used as a reference to set TMS intensity, may not correspond to the excitability of cortico-cortical pathways.

Cortico-cortical paired associative stimulation conditioning superficial ventral premotor cortex-primary motor cortex connectivity influences motor cortical activity during precision grip.

The ventral premotor cortex (PMv) and primary motor cortex (M1) represent critical nodes of a parietofrontal network involved in grasping actions, such as power and precision grip. Here, we investigated how the functional PMv-M1 connectivity drives the dissociation between these two actions. We applied a PMv-M1 cortico-cortical paired associative stimulation (cc-PAS) protocol, stimulating M1 in both postero-anterior (PA) and antero-posterior (AP) directions, in order to induce long-term changes in the activity of different neuronal populations within M1. We evaluated the motor-evoked potential (MEP) amplitude, MEP latency and cortical silent period, in both PA and AP, during the isometric execution of precision and power grip, before and after the PMv-M1 cc-PAS. The repeated activation of the PMv-M1 cortico-cortical network with PA orientation over M1 did not change MEP amplitude or cortical silent period duration during both actions. In contrast, the PMv-M1 cc-PAS stimulation of M1 with an AP direction led to a specific modulation of precision grip motor drive. In particular, MEPs tested with AP stimulation showed a selective increase of corticospinal excitability during precision grip. These findings suggest that the more superficial M1 neuronal populations recruited by the PMv input are involved preferentially in the execution of precision grip actions. KEY POINTS: Ventral premotor cortex (PMv)-primary motor cortex (M1) cortico-cortical paired associative stimulation (cc-PAS) with different coil orientation targets dissociable neural populations. PMv-M1 cc-PAS with M1 antero-posterior coil orientation specifically modulates corticospinal excitability during precision grip. Superficial M1 populations are involved preferentially in the execution of precision grip. A plasticity induction protocol targeting the specific PMv-M1subpopulation might have important translational value for the rehabilitation of hand function.

Pathoetiology of Levator Ani Syndrome and Its Treatment With Translumbosacral Neuromodulation Therapy.

The pathoetiology and treatment of levator ani syndrome (LAS) remain unclear. We evaluated pathophysiology using translumbosacral motor-evoked potentials and anorectal manometry in patients with LAS and compared with healthy controls. A cohort underwent translumbosacral neuromodulation therapy (TNT). Lumbar and sacral motor-evoked potential latencies were prolonged in 32 patients with LAS compared with 31 controls ( P < 0.013), with higher prevalence of anal neuropathy ( P = 0.026). TNT improved anorectal pain ( P = 0.003) and neuropathy ( P < 0.02) in 13 patients with LAS. Patients with LAS demonstrate significant lumbosacral neuropathy that may cause anorectal pain. TNT improved anorectal pain and neuropathy, providing a novel therapeutic option.

Whole body vibration accelerates the functional recovery of motor nerve components in sciatic nerve-crush injury model rats.

This study aimed to investigate the effect of whole body vibration (WBV) on the sensory and motor nerve components with sciatic nerve injury model rats. Surgery was performed on 21 female Wister rats (6-8 weeks) under intraperitoneal anesthesia. The nerve-crush injuries for the left sciatic nerve were inflicted using a Sugita aneurysm clip. The sciatic nerve model rats were randomly divided into two groups (n=9; control group, n=12; WBV group). The rats in the WBV group walked in the cage with a vibratory stimulus (frequency 50 Hz, 20 min/day, 5 times/wk), while those in the control group walked in the cage without any vibratory stimulus. We used heat stimulation-induced sensory threshold and lumbar magnetic stimulation-induced motor-evoked potentials (MEPs) to measure the sensory and motor nerve components, respectively. Further, morphological measurements, bilateral hind-limb dimension, bilateral gastrocnemius dimension, and weight were evaluated. Consequently, there were no significant differences in the sensory threshold at the injury side between the control and WBV groups. However, at 4 and 6 weeks postoperatively, MEPs latencies in the WBV group were significantly shorter than those in the control group. Furthermore, both sides of the hind-limb dimension at 6 weeks postoperatively, the left side of the gastrocnemius dimension, and both sides of the gastrocnemius weight significantly increased. In conclusion, WBV especially accelerates the functional recovery of motor nerve components in sciatic nerve-crush injury model rats.

Sex-specific reference values for total, central, and peripheral latency of motor evoked potentials from a large cohort.

Differentiating between physiologic and altered motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) is crucial in clinical practice. Some physical characteristics, such as height and age, introduce sources of variability unrelated to neural dysfunction. We provided new age- and height-adjusted normal values for cortical latency, central motor conduction time (CMCT), and peripheral motor conduction time (PMCT) from a large cohort of healthy subjects. Previously reported data from 587 participants were re-analyzed. Nervous system disorders were ruled out by clinical examination and magnetic resonance imaging. MEP latency was determined as stimulus-to-response latency through stimulation with a circular coil over the "hot spot" of the First Dorsal Interosseous and Tibialis Anterior muscles, during mild tonic contraction. CMCT was estimated as the difference between MEP cortical latency and PMCT by radicular magnetic stimulation. Additionally, right-to-left differences were calculated. For each parameter, multiple linear regression models of increasing complexity were fitted using height, age, and sex as regressors. Motor evoked potential cortical latency, PMCT, and CMCT were shown to be age- and height-dependent, although age had only a small effect on CMCT. Relying on Bayesian information criterion for model selection, MEP cortical latency and PMCT were explained best by linear models indicating a positive correlation with both height and age. Also, CMCT to lower limbs positively correlated with height and age. CMCT to upper limbs positively correlated to height, but slightly inversely correlated to age, as supported by non-parametric bootstrap analysis. Males had longer cortical latencies and CMCT to lower limbs, as well as longer PMCT and cortical latencies to upper limbs, even when accounting for differences in body height. Right-to-left-differences were independent of height, age, and sex. Based on the selected regression models, sex-specific reference values were obtained for all TMS-related latencies and inter-side differences, with adjustments for height and age, where warranted. A significant relationship was observed between height and age and all MEP latency values, in both upper and lower limbs. These set of reference values facilitate the evaluation of MEPs in clinical studies and research settings. Unlike previous reports, we also highlighted the contribution of sex.

DELMEP: a deep learning algorithm for automated annotation of motor evoked potential latencies

The analysis of motor evoked potentials (MEPs) generated by transcranial magnetic stimulation (TMS) is crucial in research and clinical medical practice. MEPs are characterized by their latency and the treatment of a single patient may require the characterization of thousands of MEPs. Given the difficulty of developing reliable and accurate algorithms, currently the assessment of MEPs is performed with visual inspection and manual annotation by a medical expert; making it a time-consuming, inaccurate, and error-prone process. In this study, we developed DELMEP, a deep learning-based algorithm to automate the estimation of MEP latency. Our algorithm resulted in a mean absolute error of about 0.5 ms and an accuracy that was practically independent of the MEP amplitude. The low computational cost of the DELMEP algorithm allows employing it in on-the-fly characterization of MEPs for brain-state-dependent and closed-loop brain stimulation protocols. Moreover, its learning ability makes it a particularly promising option for artificial-intelligence-based personalized clinical applications.

High frequencies (HF) repetitive transcranial magnetic stimulation (rTMS) increase motor coordination performances in volleyball players

IntroductionIt is widely demonstrated that high frequency (HF) repetitive transcranial magnetic stimulation (rTMS) has facilitative effects and is therefore capable to inducing changes in motor responses. One of the most investigated areas is the dorsolateral prefrontal cortex (DLPFC) as it plays a special executive attention role in actively preserving access to stimulus representations and objectives in environments with plenty of distraction such as those of team sports. Volleyball is a team sport in which the attention and coordination components are essential for achieving performance. Thus, the aim of this study was to investigate if HF rTMS at DLPFC in volleyball players can improve homolateral motor coordination and cortical excitability.ResultsThis study was a double-blinded (participant and evaluator) matched-pair experimental design. Twenty right-handed female volleyball players were recruited for the study and were randomly assigned either the active rTMS (n = 10) or the sham stimulation group (n = 10). The stimulation was performed in one session with 10 Hz, 80% of the resting motor threshold (RMT) of the right first dorsal interosseous muscle, 5 s of stimulation, and 15 s of rest, for a total of 1500 pulses. Before and after stimulation, the coordination and the cortical excitability were evaluated. The significant finding of this paper was that HF-rTMS of the DLPFC improved performance in terms of the homolateral interlimb coordination, with a significantly decreased in resting motor threshold and MEP latency of the ipsilateral motor cortex. It seem that HF-rTMS could increase coordination performances when the velocity of the execution is higher (120 bpm and 180 bpm).ConclusionMoreover, in active rTMS group significant differences emerged after stimulation in RMT and in MEP latency, while no differences emerged after stimulation in MEP amplitude. In conclusion we believe that these results may be of great interest to the scientific community and may also have practical implications in the future.

Clinic-Electrophysiologic Correlations in Rehabilitation of Adult Patients with Traumatic Brachial Plexus Lesions

Nerve-transfer surgery is the treatment of choice for traumatic brachial plexus injuries (tBPIs). Combined electromyography (EMG) follow-ups and results obtained by transcranial magnetic stimulation (TMS) may provide useful follow-up of rehabilitation outcomes of elbow flexion in C5-C7 tBPIs. A total of 11 patients with complex tBPIs, operated by the Oberlin surgical technique, were assessed clinically (British Medical Research Council’s score—MRC) and by EMG + TMS after undergoing neuromuscular electrical stimulation and proprioceptive neuromuscular facilitation. Dynamometer quantitative muscle strength (DQMS) was also assessed for overall grip strength evaluation. Six patients continued rehabilitation three times a week, whereas five patients did not follow recommendations for continuous physical therapy (PT). All patients were assessed after 6 months as planned. Following a 6-month PT protocol, clinical improvements correlated with decreases of the Motor Evoked Potential (MEP) latency recorded at the first dorsal interosseous muscle, biceps brachii, and cortical level in the sublot group with continuous PT protocol compliance. We obtained significant amelioration of MEP latency and needle EMG signs of amelioration in these six patients. These cases also correlated to the MRC improvement in elbow flexion, as well as DQMS parameters. TMS parameters also mildly and inconstantly improved in the other five patients who limited themselves just to PT after surgery; however, there was no correlation with the EMG findings or MRC scaling. PT influences the cortical representation within the motor area of the upper limb when performed continuously. The electrical signals within the motor cortex promote the utility adherence to long-term PT protocols.

Temporary Occlusion of Common Carotid Arteries Does Not Evoke Total Inhibition in the Activity of Corticospinal Tract Neurons in Experimental Conditions.

Temporary occlusion of the common cervical artery is the reason for ischemic stroke in 25% of patients. Little data is provided on its effects, especially regarding neurophysiological studies verifying the neural efferent transmission within fibers of the corticospinal tract in experimental conditions. Studies were performed on 42 male Wistar rats. In 10 rats, ischemic stroke was evoked by permanent occlusion of the right carotid artery (group A); in 11 rats, by its permanent bilateral occlusion (B); in 10 rats, by unilateral occlusion and releasing after 5 min (C); and in 11 rats, by bilateral occlusion and releasing after 5 min (D). Efferent transmission of the corticospinal tract was verified by motor evoked potential (MEP) recordings from the sciatic nerve after transcranial magnetic stimulation. MEPs amplitude and latency parameters, oral measurements of temperature, and verification of ischemic effects in brain slides stained with hematoxylin and eosin staining (H + E) were analyzed. In all groups of animals, the results showed that five minutes of uni- or bilateral occlusion of the common carotid artery led to alterations in brain blood circulation and evoked changes in MEP amplitude (by 23.2% on average) and latency parameters (by 0.7 ms on average), reflecting the partial inability of tract fibers to transmit neural impulses. These abnormalities were associated with a significant drop in the body temperature by 1.5 °C on average. Ten minutes occlusion in animals from groups A and B resulted in an MEP amplitude decrease by 41.6%, latency increase by 0.9 ms, and temperature decrease by 2.9 °C of the initial value. In animals from groups C and D, five minutes of recovery of arterial blood flow evoked stabilization of the MEP amplitude by 23.4%, latency by 0.5 ms, and temperature by 0.8 °C of the initial value. In histological studies, the results showed that ischemia was most prominent bilaterally in sensory and motor areas, mainly for the forelimb, rather than the hindlimb, innervation of the cortex, putamen and caudate nuclei, globulus pallidus, and areas adjacent to the fornix of the third ventricle. We found that the MEP amplitude parameter is more sensitive than the latency and temperature variability in monitoring the ischemia effects course following common carotid artery infarction, although all parameters are correlated with each other. Temporary five-minute lasting occlusion of common carotid arteries does not evoke total and permanent inhibition in the activity of corticospinal tract neurons in experimental conditions. The symptoms of rat brain infarction are much more optimistic than those described in patients after stroke, and require further comparison with the clinical observations.