A practical guide to diagnostic transcranial magnetic stimulation: report of an IFCN committee

Height-dependent variation in corticospinal excitability modulation after active but not sham intermittent theta burst stimulation

Poor reproducibility and high inter-individual variability in responses to intermittent theta burst stimulation (iTBS) of the human motor cortex (M1) are matters of concern. Here we recruited 17 healthy young adults in a randomized, sham-controlled, crossover study. Transcranial magnetic stimulation (TMS)-elicited motor evoked potentials (MEPs) were measured pre-iTBS (T0) and post-iTBS at 4-7 (T1), 9-12 (T2), 17-20 (T3), and 27-30 minutes (T4) from the right first dorsal interosseous muscle. MEP grand average (MEPGA) was defined as the mean of the normalized-to-baseline MEPs at all timepoints post-iTBS. As secondary objectives, we measured blood pressure, heart rate, and capillary blood glucose pre-iTBS, and at 0 and 30 minutes post-iTBS. The TMSens_Q structured questionnaire was filled out at the end of each session. Two-way repeated ANOVA did not show a significant TIME×INTERVENTION interaction effect on MEP amplitude, MEP latency, blood pressure, heart rate, and blood glucose (p > 0.05). Sleepiness was the most reported TMSens_Q sensation (82.3 %) in both groups. Surprisingly, the subjects' height negatively correlated with the normalized MEP amplitudes at T3 (r = -0.65, p = 0.005), T4 (r = -0.66, p = 0.004), and MEPGA (r = -0.68, p = 0.003), with a trend correlation at T1 (r = -0.46, p = 0.062) and T2 (r = -0.46, p = 0.065) in the active but not sham group. In view of this, we urge future studies to delve deeper into the influence of height on neuroplasticity induction of the M1 representation of peripheral muscles. In the end, we highlight unique methodological considerations in our study protocol and future recommendations for M1-iTBS studies.

Effects of dual-target repetitive transcranial magnetic stimulation in patients with minimally conscious state: A preliminary study

Repetitive transcranial magnetic stimulation (rTMS) is a promising neuromodulation therapy that facilitates recovery in patients with prolonged disorders of consciousness (pDOC). This study aimed to evaluate the efficacy of dual-target rTMS in treating patients with minimally conscious state (MCS). A total of 20 MCS patients were recruited and randomly assigned to either the real or sham stimulation group. Participants received 10 Hz rTMS targeting the left prefrontal and parietal cortices for 10 consecutive days. The Coma Recovery Scale-Revised (CRS-R) and resting-state EEG were recorded, with relative power spectral density and coherence subsequently computed. Additionally, behavioral assessments were conducted over a six-month follow-up period. Our findings indicate that 10 Hz dual-target rTMS enhances brain oscillatory activity in the frontal, central, and parietal lobes. Specifically, the treatment resulted in a reduction in delta-band activity and an increase in alpha-band activity in the frontal lobes, as well as an elevation in alpha-band power in the central and parietal region. In contrast, no significant changes were observed in the sham stimulation group. Meanwhile, in the real stimulation group, long-distance coherence (F3-P4) exhibited increased in alpha-band. These findings suggest that enhanced oscillatory activity and EEG functional connectivity may underlie the modulatory effects of dual-target rTMS. Additionally, a combined prefrontal and parietal cortex approach is another viable option in rTMS protocols for patients with pDOC.

No Evidence of Hysteresis in Quadriceps or Hamstring Active Motor Evoked Potentials

BackgroundThe excitability of the corticospinal tract (i.e., corticospinal excitability) is a valuable tool for assessing neurophysiology and the effectiveness of interventions in individuals with and without neurological and/or orthopaedic injuries. Corticospinal excitability is often measured with an input-output recruitment curve, which is produced by stimulating the motor cortex via transcranial magnetic stimulation (TMS) at several intensities and measuring the changes in the evoked responses. However, it is currently unclear if hysteresis in motor evoked potentials (MEPs) (i.e., changes in MEP amplitude due to the order of stimulus intensities) affects the resulting measure of excitability, particularly in lower extremity muscles.ObjectiveTo evaluate whether the order of stimulus intensity (ascending, descending, randomized) affects input-output recruitment curves measured in the lower extremity muscles.MethodsRecruitment curves were produced in neurologically intact individuals by stimulating the primary motor cortex at 70% to 140% of active motor threshold in 10% increments. We examined three stimulus intensity ordering paradigms: ascending (70→ 140), descending (140→ 70), and randomized. We measured MEPs of the quadriceps and the antagonistic hamstring muscles using surface electromyography in addition to quadriceps motor evoked torque. We computed the area under the recruitment curve (AUC) of the raw and normalized motor evoked responses and used classical and Bayesian inference methods to comprehensively evaluate hysteresis in MEPs.ResultsClassical hypothesis testing revealed no significant main effects of stimulus order. Bayesian analyses also confirmed that the null model was more favored than the main effects model.ConclusionsCorticospinal excitability of the quadriceps and antagonistic hamstring muscles were not influenced by stimulus intensity order. Any of the three approaches (ascending, descending, randomized) may be used when measuring recruitment curves for the quadriceps and hamstring muscles.

Preliminary observations in cortical excitability changes using transcranial magnetic stimulation (TMS), it's correlation with diffusion tensor imaging (DTI) in subjects with neuromyelitis optica spectrum disorder (NMOSD)

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing central nervous system disease most commonly associated with aquaporin-4 antibodies (AQP4-Ab) and Myelin oligodendrocyte glycoprotein (MOG) antibodies. These demyelinating disorders influence cortical excitability, which has been studied using advanced imaging techniques and transcranial magnetic stimulation (TMS) in our study.

METHODS

This is a prospective study of 30 subjects. Ten subjects, each of AQP4, MOGAD, and dual seronegative (SN)-NMOSD, were recruited and compared to 30 healthy controls. All the subjects underwent TMS and MRI with diffusion tensor imaging (DTI). Resting motor threshold (RMT), central motor conduction time (CMCT), ipsilateral (ISP) and contralateral silent period (cSP), short interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were the TMS parameters assessed. Fractional anisotropy (FA) and axial diffusivity (AD) were the DTI parameters studied. DTI findings were correlated with the TMS parameters.

RESULTS

The study cohort had a male-to-female ratio of (M: F) = 13:17. RMT was highest in the AQP4-Ab subgroup (40.2 ± 11.9%) compared to SN NMOSD (36.2 ± 4.6%) and MOGAD (34.5 ± 6.7%). CMCT was maximum prolonged in subjects with MOGAD (9.6 ± 1.9 msec). The cSP was reduced in MOGAD (79.9 ± 36.3msec). SICI was lowest in the AQP4-Ab subgroup (1.27 ± 1.12) and was preserved in the MOGAD subgroup (0.88 ± 0.55). The DTI data demonstrated statistically significant, reduced FA and AD in AQP4-Ab and SN NMOSD subjects.

CONCLUSION

This is the first study that looked at the cortical excitability changes in the three subgroups of NMOSD. It has been observed that AQP4 NMOSD and SN NMOSD had a severe form of demyelinating disease compared to MOGAD.

Relating cortical morphology, corticospinal excitability, corticomotor representation, and quadriceps strength after anterior cruciate ligament injury

The current study investigated the relationship between sensorimotor cortical thickness, corticospinal excitability, corticomotor topography, and quadriceps strength after ACL reconstruction (ACLR). Ten women with a history of unilateral ACLR and 10 controls (CON) received single-pulse transcranial magnetic stimulation during unilateral, submaximal isometric knee extensions. Pulses were delivered to each vastus medialis oblique (VMO) hotspot with concurrent biceps femoris (BF) monitoring. Corticospinal excitability was assessed by delivering 40 pulses at various intensities to each hotspot. Motor-evoked potentials (MEPs) were averaged at each intensity and fitted to a Boltzmann sigmoidal curve using nonlinear regression to derive v50, slope, and MEPMAX. A motor mapping procedure included 120 pulses delivered in a 6 × 6 cm grid placed around each hotspot. Ultrasonography was used to measure VMO muscle thickness. Structural MRIs were acquired to derive paracentral lobule (PCL) cortical thickness. ACLR group's previously injured leg was weaker than the healthy leg, with no between-leg differences in CON. Regardless of group, v50 was asymmetrical between legs. Slope, MEPMAX, VMO map measures, and VMO thickness were similar between legs and groups. ACLR tended to have asymmetrical PCL thickness with BF map measures larger in the hemisphere of the previously injured leg than healthy leg, whereas CON had symmetrical PCL thickness and BF map measures. Results indicate that even years after ACLR corticomotor structure plasticity is homotopic with persistent asymmetrical knee extension strength but no differences in corticospinal excitability. Overall, the hemispheric asymmetry in leg-specific brain structure may contribute to the knee extensor strength deficits common after ACLR.

Individualized time windows enhance TMS-EEG signal characterization and improve assessment of cortical function in schizophrenia

Transcranial magnetic stimulation and electroencephalography (TMS-EEG) recordings are crucial to directly assess cortical excitability and inhibition in a non-invasive and task-free manner. TMS-EEG signals are characterized by TMS-evoked potentials (TEPs), which are employed to evaluate cortical function. Nonetheless, different time windows (TW) have been used to compute them over the years. Moreover, these TWs tend to be the same for all participants omitting the intersubject variability. Therefore, the objective of this study is to assess the effect of using different TWs to compute the TEPs, moving from a common fixed TW to more adaptive individualized TWs. Twenty-nine healthy (HC) controls and twenty schizophrenia patients (SCZ) underwent single-pulse (SP) TMS-EEG protocol. Firstly, only the HC were considered to evaluate the TEPs for three different TWs in terms of amplitude and topographical distribution. Secondly, the SCZ patients were included to determine which TW is better to characterize the brain alterations of SCZ. The results indicate that a more individualized TW provides a better characterization of the SP TMS-EEG signals, although all of them show the same tendency. Regarding the comparison between groups, the individualized TW is the one that provides a better differentiation between populations. They also provide further support to the possible imbalance of cortical excitability/inhibition in the SCZ population due to its reduced activity in the N45 TEP and greater amplitude values in the N100. Results also suggest that the SCZ brain has a baseline hyperactive state since the TEPs of the SCZ appear earlier than those of the HC.

Investigating brain network dynamics in state-dependent stimulation: A concurrent electroencephalography and transcranial magnetic stimulation study using hidden Markov models

BACKGROUND

Systems neuroscience studies have shown that baseline brain activity can be categorized into large-scale networks (resting-state-networks, RNSs), with influence on cognitive abilities and clinical symptoms. These insights have guided millimeter-precise selection of brain stimulation targets based on RSNs. Concurrently, Transcranial Magnetic Stimulation (TMS) studies revealed that baseline brain states, measured by EEG signal power or phase, affect stimulation outcomes. However, EEG dynamics in these studies are mostly limited to single regions or channels, lacking the spatial resolution needed for accurate network-level characterization.

OBJECTIVE

We aim at mapping brain networks with high spatial and temporal precision and to assess whether the occurrence of specific network-level-states impact TMS outcome. To this end, we will identify large-scale brain networks and explore how their dynamics relates to corticospinal excitability.

METHODS

This study leverages Hidden Markov Models to identify large-scale brain states from pre-stimulus source space high-density-EEG data collected during TMS targeting the left primary motor cortex in twenty healthy subjects. The association between states and fMRI-defined RSNs was explored using the Yeo atlas, and the trial-by-trial relation between states and corticospinal excitability was examined.

RESULTS

We extracted fast-dynamic large-scale brain states with unique spatiotemporal and spectral features resembling major RSNs. The engagement of different networks significantly influences corticospinal excitability, with larger motor evoked potentials when baseline activity was dominated by the sensorimotor network.

CONCLUSIONS

These findings represent a step forward towards characterizing brain network in EEG-TMS with both high spatial and temporal resolution and underscore the importance of incorporating large-scale network dynamics into TMS experiments.

Stimulation Parameters Recruit Distinct Cortico-Cortical Pathways: Insights from Microstate Analysis on TMS-Evoked Potentials

Transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) represent an innovative measure for examining brain connectivity and developing biomarkers of psychiatric conditions. Minimizing TEP variability across studies and participants, which may stem from methodological choices, is therefore vital. By combining classic peak analysis and microstate investigation, we tested how TMS pulse waveform and current direction may affect cortico-cortical circuit engagement when targeting the primary motor cortex (M1). We aim to disentangle whether changing these parameters affects the degree of activation of the same neural circuitry or may lead to changes in the pathways through which the induced activation spreads. Thirty-two healthy participants underwent a TMS-EEG experiment in which the pulse waveform (monophasic, biphasic) and current direction (posterior-anterior, anterior-posterior, latero-medial) were manipulated. We assessed the latency and amplitude of M1-TEP components and employed microstate analyses to test differences in topographies. Results revealed that TMS parameters strongly influenced M1-TEP components' amplitude but had a weaker role over their latencies. Microstate analysis showed that the current direction in monophasic stimulations changed the pattern of evoked microstates at the early TEP latencies, as well as their duration and global field power. This study shows that the current direction of monophasic pulses may modulate cortical sources contributing to TEP signals, activating neural populations and cortico-cortical paths more selectively. Biphasic stimulation reduces the variability associated with current direction and may be better suited when TMS targeting is blind to anatomical information.

Protocol to assess changes in brain network resistance to perturbation during offline processing using TMS-EEG

Transcranial magnetic stimulation (TMS) perturbs specific brain regions and, combined with electroencephalography (EEG), enables the assessment of activity within their connected networks. We present a resting-state TMS-EEG protocol, combined with a controlled experimental design, to assess changes in brain network activity during offline processing, following a behavioral task. We describe steps for experimental design planning, setup preparation, data collection, and analysis. This approach minimizes biases inherent to TMS-EEG, ensuring an accurate assessment of changes within the network. For complete details of the use and execution of this protocol, please refer to Bracco et al.1.

Force overestimation during vascular occlusion is triggered by motor system inhibition

Low-intensity resistance exercise with vascular occlusion enhances human muscular strength by elevating neural drive to muscles, which is accompanied by the additional activation of fast-twitch fibers because of muscle fatigue. However, few previous studies have investigated the underlying neuromotor mechanisms from a perspective other than muscle fatigue. Notably, participants require more voluntary effort to exert muscular force to lift a weight immediately after vascular occlusion, indicating its acute effect on the force perception system without muscle fatigue. However, the major cause of force overestimation under these conditions remains unclear. We sought to elucidate the neural mechanism of force exertion combined with tourniquet-induced vascular occlusion, with special reference to exerted force perception, using motor evoked potentials in response to transcranial magnetic stimulation applied over the contralateral primary motor cortex as well as upper extremity H-reflex measurements. Rapid force overestimation was accompanied by the instantaneous inhibition of spinal motoneuron and corticospinal tract excitability. Thus, force overestimation may be caused by motor-related cortical areas functioning as the source of excitatory input to the corticospinal tract; participants would be unable to exert the same handgrip force as with normal blood flow without a compensatory input to the corticospinal tract from motor-related cortical areas.

Homeostatic plasticity in patients with disorders of consciousness detected by combined stimulation: a study protocol

Background

Non-invasive neuromodulation (NIN) techniques have been widely utilized in treating patients with disorders of consciousness (DoC), but their therapeutic effects have been inconsistent. Given the reliance of NIN techniques on synaptic plasticity, and the potential impairment of synaptic plasticity (particularly homeostatic plasticity) resulting from severe brain injury, it is possible that the variation in therapeutic effects is due to alterations in homeostatic plasticity in patients with DoC. Therefore, this study will use preconditioning TMS to examine the retention of homeostatic plasticity in patients with DoC.

Methods

We will enroll 30 patients with DoC and 15 healthy controls and randomize the order of their sessions. According to the priming protocol, the trial was divided into three different sessions with a 2-day break between each session. The session will involve a 10-min duration of transcranial direct current stimulation (tDCS) priming, followed by a 192-s period of transcranial magnetic stimulation (TMS) test. Transcranial stimulation will be specifically targeted toward the left primary motor cortex. Measurements of motor evoked potentials will be taken at several time points: baseline, after tDCS, and after TMS. Coma Recovery Scale-Revised will be conducted both baseline and after TMS.

Discussion

Studying whether homeostatic plasticity is preserved in patients with DoC is beneficial for gaining a better understanding of their brain condition. If the homeostatic plasticity of patients with DoC is impaired, then NIN, which are based on altering synaptic plasticity in healthy individuals to achieve stimulating effects, may not be directly translatable to the therapeutic interventions for patients with DoC. Instead, the homeostatic plasticity of patients should be restored before implementing the intervention.

Accelerated Theta-Burst Stimulation for Treatment-Resistant Depression: A Randomized Clinical Trial

Importance

Intermittent theta-burst stimulation (iTBS) is an established treatment for treatment-resistant depression (TRD). Sessions conducted more than once daily (ie, accelerated TBS [aTBS]) may enhance antidepressant effects. However, evidence is limited to small trials, and protocols are time-consuming and can require neuroimaging-based targeting.

Objective

To evaluate the efficacy and safety of a pragmatic aTBS protocol for TRD.

Design, Setting, and Participants

This triple-blinded, sham-controlled randomized clinical trial was conducted at a single center in São Paulo, Brazil, from July 2022 to June 2024, with a subsequent open-label phase. Patients aged 18 to 65 years with major depression, experiencing a TRD episode, and with a Hamilton Depression Rating Scale, 17-item (HDRS-17) score of 17 or higher were eligible for inclusion. Exclusion criteria were other psychiatric disorders (except anxiety), neurological conditions, and TBS contraindications.

Interventions

Participants received 45 active or sham stimulation sessions over 15 weekdays, with 3 iTBS sessions (1200 pulses each) per day, spaced 30 minutes apart and targeting the left dorsolateral prefrontal cortex using a craniometric approach. In the open-label phase, additional aTBS sessions were offered to achieve a response (≥50% HDRS-17 score improvement) if needed.

Main Outcomes and Measures

The primary outcome was change in HDRS-17 score at week 5.

Results

Of 431 volunteers screened, 100 participants were enrolled and randomized to either sham or active aTBS. Mean (SD) participant age was 41.7 (8.8) years, and 84 participants (84%) were female. A total of 89 patients completed the study. In the intention-to-treat analysis, the mean change in HDRS-17 scores from baseline to the study end point was 5.57 (95% CI, 3.99-7.16) in the sham group and 9.68 (95% CI, 8.11-11.25) in the active group, corresponding to 31.87% and 54.7% score reductions, respectively, and a medium-to-large effect size (Cohen d, 0.65; 95% CI, 0.29-1.00; P < .001). Response and remission rates were also higher in the active group. Both interventions were well tolerated, but scalp pain was more frequent in the active group than the sham group (17.4% vs 4.4%). During the open-label phase, approximately 75% of patients received additional sessions.

Conclusions and Relevance

In this triple-blinded, sham-controlled randomized clinical trial, a pragmatic aTBS protocol using only 3 iTBS sessions per day and a nonexpensive, non-neuronavigated approach was found to be safe and effective for TRD.

Trial Registration

ClinicalTrials.gov Identifier: NCT05388539.

Number of conditioning trials, but not stimulus intensity, influences operant conditioning of brain responses after total knee arthroplasty

PURPOSE

The primary purpose of this randomized, cross-sectional study was to determine whether operant conditioning of motor evoked torque (MEPTORQUE) in individuals with total knee arthroplasty (TKA) increases quadriceps MEPTORQUE responses within a single session and induces acute corticospinal adaptations by producing sustained increases in MEPTORQUE after training. A secondary purpose was to determine if these changes were affected by the stimulus intensity and number of training trials.

METHODS

Thirty participants were block-randomized into one of three groups based on the participant's active motor threshold (100%, 120%, and 140%) to evaluate the effect of stimulus intensity. Participants received three blocks of conditioning trials (COND), where they trained to increase their MEPTORQUE. Control (CTRL) transcranial magnetic stimulation pulses were provided before and after each COND block to establish baseline corticospinal excitability and to evaluate the effect of the number of training trials. Two MEPTORQUE recruitment curves were collected to evaluate the effect of up-conditioning on acute corticospinal adaptations.

RESULTS

TKA participants were able to successfully increase their MEPTORQUE in a single session (F3,81 = 10.719, p < 0.001) and induce acute corticospinal adaptations (F1,27 = 20.029, p < 0.001), indicating sustained increases in quadriceps corticospinal excitability due to operant conditioning. While the stimulus intensity used during training did not affect the ability to increase MEPTORQUE (F2,26 = 0.021, n.s.) or its associated acute adaptations (F2,27 = 0.935, n.s.), the number of training trials significantly influenced these outcomes (F3,81 = 10.719, p < 0.001; F3,81 = 4.379, p = 0.007, respectively).

CONCLUSION

Operant conditioning is a feasible approach for improving quadriceps corticospinal excitability following TKA. While any of the three stimulus intensities evaluated in this study may be used in future operant conditioning interventions, using a low or moderate stimulus intensity and 150 training trials are recommended to improve treatment efficiency and patient adherence.

LEVEL OF EVIDENCE

Level II.

A novel TMS framework for assessing neurophysiological recovery at the subacute stage after stroke

OBJECTIVE

To use peri-threshold transcranial magnetic stimulation (TMS) intensities to elicit motor evoked potentials (MEPs) during the subacute stage after stroke and assess their association with upper limb motor recovery.

METHODS

Twenty-five MEP+ patients participated in three sessions at 1, 3, and 6 months post-stroke. Single-pulse TMS across a range of stimulation intensities was used to elicit MEPs in four muscles of the paretic and non-paretic upper limb. At each timepoint, threshold matrices were constructed based on MEP amplitude and persistence. A matrix element was suprathreshold if five out of ten stimulations elicited MEPs ≥ 50 μV. A subthreshold element produced MEPs below this criterion. Dexterity was assessed using the nine hole peg test.

RESULTS

There were fewer suprathreshold, and more subthreshold elements on the paretic compared to the non-paretic side. The number of suprathreshold elements on the paretic side increased between 1 and 6 months post-stroke. Neither sub- nor supra-threshold elements were associated with dexterity recovery.

CONCLUSION

The proportion of sub- and supra-threshold elements reflect neurophysiological recovery during the subacute stage after stroke. A threshold matrix framework can identify patients with stable versus dynamic neurophysiology post-stroke.

SIGNIFICANCE

A compositional analysis framework can quantify neurophysiological recovery after stroke.

Bridging the gap to clinical use: A systematic review on TMS-EEG test-retest reliability

BACKGROUND

Transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG) can provide insight on cortical excitability and brain circuits. TMS-evoked potentials (TEPs) are phase-locked waveforms reflecting neural activity, with potential applications in psychiatry and neurology. However, the reliability of TEPs remains underexplored, hindering clinical standardization. This systematic review evaluates TEP reliability, focusing on commonly used measures and assessments.

METHODS

A systematic review was conducted on PubMed for studies from 2002 to October 10, 2024, using keywords combining TMS, EEG, and reliability terms. Systematic reviews and non-English articles were excluded.

RESULTS

Eighteen studies met inclusion criteria, mostly assessing young, healthy populations. Late TEP components demonstrated high relative reliability, while early components exhibited lower reliability and variability across sessions. Analytical methods like the intraclass and concordance correlation coefficients, and Pearson's correlations consistently favored late TEPs.

DISCUSSION

Late TEPs exhibit higher reliability, while early components require further research. TMS artifacts complicate interpretation, in both late and early responses. Formal reliability assessments, standardized protocols, and diverse populations are essential for advancing TEP reliability for clinical application.

CONCLUSIONS

A more comprehensive reliability assessments is needed before the implementation of clinical applications.

Test-retest reliability of TMS motor evoked responses and silent periods during explosive voluntary isometric contractions

PURPOSE

This study assessed the test-retest reliability of TMS motor evoked potentials (MEPs) and silent periods at early, middle, and late phases of the rising time-torque curve during explosive voluntary contractions. We also investigated how the number of consecutively averaged measurements influenced reliability.

METHODS

On two separate occasions 3-7 days apart, 14 adults performed several isometric explosive (1-s) contractions of the knee extensors, some of which were superimposed with TMS to elicit MEPs in the superficial quadriceps. Of those with TMS, stimulation was timed to elicit MEPs at either 45 (early), 115 (middle), or 190 ms (late) following contraction onset (16 with-TMS contractions per time condition). TMS was also superimposed at the plateau of 15 separate MVCs. Test-retest intraclass correlation coefficient (ICC) and coefficient of variation (CV) were calculated for MEPs and silent periods consecutively averaged over 3 to 15 separate contractions.

RESULTS

No one condition/phase was more reliable than another. For MEP amplitude, in all conditions except the explosive late phase, ICCs generally increased, and CV decreased, with an increase in the number of averaged contractions, and were > 0.50 ICC and < 15% CV within seven contractions. For silent period, ICCs and CVs were unaffected by the number of consecutively averaged contractions and remained > 0.50 ICC and < 10% CV.

CONCLUSION

Test-retest reliability of TMS responses is comparable between phases of explosive contraction and at the plateau of MVC. To maximise reliability of MEPs during explosive contractions or MVCs, we recommend future studies average data across more than the 3-5 contractions typically reported in the literature investigating MEPs at MVC plateau.

Operant Upconditioning of the Quadriceps Motor Evoked Torque as a Means to Improve Quadriceps Function After ACL Reconstruction

BACKGROUND

Diminished corticospinal excitability is theorized to contribute to poor quadriceps function after anterior cruciate ligament (ACL) reconstruction. Operant conditioning of the motor evoked torque (MEPTORQUE) is a promising approach capable of improving corticospinal excitability. However, it is unknown whether increasing corticospinal excitability can improve quadriceps function after a short-term operant conditioning intervention in patients with reconstructed ACL.

HYPOTHESIS

After ACL reconstruction, patients would demonstrate increases in quadriceps strength, voluntary activation, and corticospinal excitability after a 2-week operant conditioning intervention.

STUDY DESIGN

Randomized controlled clinical trial.

LEVEL OF EVIDENCE

Level 1.

METHODS

A total of 22 patients with reconstructed ACL were randomized into 1 of 2 groups: group 1 received 2 weeks of operant conditioning training on the reconstructed leg to improve their transcranial magnetic stimulation (TMS)-elicited MEPTORQUE responses (COND); group 2 received 2 weeks of TMS only (SHAM-COND). Quadriceps strength, voluntary activation, and corticospinal excitability on the reconstructed leg were evaluated before and after the 2-week intervention. Within-session changes in corticospinal excitability were also evaluated during the training sessions.

RESULTS

The COND group demonstrated a significantly higher within-session percent increase in MEPTORQUE during training compared with the SHAM-COND group, paralleled by a significant increase in corticospinal excitability after the 2-week intervention. In addition, quadriceps strength and voluntary activation improved on the reconstructed leg after the 2-week intervention, regardless of group.

CONCLUSION

Operant conditioning training can elicit improvements in corticospinal excitability after ACL reconstruction; however, improvements in quadriceps strength and voluntary activation seem not to be attributed solely to operant upconditioning training.

CLINICAL RELEVANCE

Operant conditioning is a promising approach to improve corticospinal excitability after ACL reconstruction. However, optimizing the delivery of operant conditioning protocols by potentially increasing the dosage of operant conditioning and intervening earlier after surgery may be needed to translate these changes to improvements in quadriceps function.

Frequency-dependent corticospinal facilitation following tibialis anterior neuromuscular electrical stimulation

The optimal stimulation frequency for inducing neuromodulatory effects remains unclear. The purpose of our study was to investigate the effect of neuromuscular electrical stimulation (NMES) with different frequencies on cortical and spinal excitability. Thirteen able-bodied individuals participated in the experiment involving NMES: (i) low-frequency at 25 Hz, (ii) high-frequency at 100 Hz, and (iii) mixed-frequency at 25 and 100 Hz switched every one second. All interventions were applied on the tibialis anterior muscle using a 10 sec ON / 10 sec OFF duty cycle for 10 min, using motor-level NMES at 120 % of the individual motor threshold for each stimulating frequency. Assessments were performed at baseline, immediately after, and 30 min after the interventions. Corticospinal excitability and intracortical inhibition were examined using transcranial magnetic stimulation by assessing the motor evoked potentials and cortical silent period, respectively. Spinal motoneuron excitability and neuromuscular propagation were assessed using peripheral nerve stimulation by evaluating F-wave and maximum motor (Mmax) responses, respectively. Maximal voluntary contraction (MVC) was evaluated during isometric dorsiflexion force exertion. Motor performance was also evaluated during the ankle dorsiflexion force-matching task. Our results showed that mixed frequency was most effective in modulating corticospinal excitability, although motor performance was not affected by any intervention. The cortical silent period was prolonged and Mmax was inhibited by all frequencies, while the F-wave and MVC were unaffected. Mixed-frequency stimulation could recruit a more diverse range of motor units, which are recruited in a stimulus frequency-specific manner, than single-frequency stimulation, and thus may have affected corticospinal facilitation.

Effects of Pattern-Reversal Visual Stimulation on Brain Activity in Migraineurs and General Population

BackgroundA better understanding of migraine pathophysiology through standardized methods could facilitate the development of more effective therapeutic approaches for migraine sufferers. However, neurophysiological studies with migraine sufferers present larger variability, as most contain only a single measurement.ObjectiveThis observational study aimed to compare the cortical and visual excitability of migraine sufferers, individuals with other types of headaches, and healthy participants in response to pattern-reversal visual stimulation.MethodsFifty-nine individuals were classified by a neurologist into the following groups: (i) migraineurs (n = 25); (ii) other types of headaches (n = 23); (iii) healthy (n = 11). Habituation during pattern-reversal visual stimulation was assessed by visual evoked potentials. Visual and motor cortex excitability were evaluated before and after pattern-reversal visual stimulation.ResultsWe found no intergroup differences in motor and visual excitability measures after pattern-reversal visual stimulation. Compared to the healthy group, migraineurs and individuals with other types of headaches displayed a reduction in phosphene threshold after pattern-reversal visual stimulation. Additionally, an increase in visual cortical excitability in these groups was also observed. Lastly, the habituation in individuals with migraines and other types of headaches was lower compared to healthy individuals. Therefore, the lack of habituation may not be exclusively associated with the pathophysiological mechanisms of migraine.ConclusionIndividuals who experience headaches, including migraineurs, have an increased visual cortical excitability in response to visual stimuli. This finding is promising for guiding future neurophysiological research to identify cortical biomarkers in migraineurs and in other types of headaches.

Non-invasive brain stimulation in cognitive sciences and Alzheimer's disease

Over the last four decades, non-invasive brain stimulation techniques (NIBS) have significantly gained interest in the fields of cognitive sciences and dementia care, including neurorehabilitation, for its emerging potential in increasing the insights over brain functions and in boosting residual cognitive functions. In the present paper, basic physiological and technical mechanisms and different applications of NIBS were reviewed and discussed to highlight the importance of NIBS in multidisciplinary and translational approaches in clinical and research settings of cognitive sciences and neurodegenerative diseases, especially in Alzheimer's disease. Indeed, NIBS strategies may represent a promising opportunity to increase the potential of neuromodulation as efficacious interventions for individualized patients care.

Involvement of muscarinic acetylcholine receptor-mediated cholinergic neurotransmission in TMS-EEG responses

The combination of transcranial magnetic stimulation and electroencephalography (TMS-EEG) is emerging as a valuable tool for investigating brain functions in health and disease. However, the detailed neural mechanisms underlying TMS-EEG responses, including TMS-evoked EEG potentials (TEPs) and TMS-induced EEG oscillations (TIOs), remain largely unknown. Combining TMS-EEG with pharmacological interventions provides a unique opportunity to elucidate the roles of specific receptor-mediated neurotransmissions in these responses. Here, we investigated the involvement of muscarinic acetylcholine receptor (mAChR)-mediated cholinergic neurotransmission in TMS-EEG responses by evaluating the effects of mAChR antagonists on TEPs and TIOs in twenty-four healthy participants using a randomized, placebo-controlled crossover design. TEPs and TIOs were measured before and after administering a single oral dose of scopolamine (a non-selective mAChR antagonist), biperiden (an M1 mAChR antagonist), or placebo, with TMS targeting the left medial prefrontal cortex (mPFC), angular gyrus (AG), and supplementary motor area (SMA). The results indicated that mAChR-mediated cholinergic neurotransmission played a role in TEPs, but not TIOs, in a target-specific manner. Specifically, scopolamine significantly increased the amplitude of a local TEP component between approximately 40 and 63 ms post-stimulus when TMS was applied to the SMA, but not the mPFC or AG. Biperiden produced a similar but less pronounced effect. Importantly, the effects of these mAChR antagonists on TEPs were independent of those on sensory-evoked EEG potentials caused by TMS-associated sensory stimulation. These findings expand our understanding of TMS-EEG physiology, providing insights for its application in physiological and clinical research.

Preoperative mapping techniques for brain tumor surgery: a systematic review

Accurate preoperative mapping is crucial for maximizing tumor removal while minimizing damage to critical brain functions during brain tumor surgery. Navigated transcranial magnetic stimulation (nTMS), magnetoencephalography (MEG), and functional magnetic resonance imaging (fMRI) are established methods for assessing motor and language function. Following PRISMA guidelines, this systematic review analyzes the reliability, clinical utility, and accessibility of these techniques. A total of 128 studies (48 nTMS, 56 fMRI, 24 MEG) were identified from various databases. The analysis finds nTMS to be a safe, standardized method with high accuracy compared to direct cortical stimulation for preoperative motor mapping. Combining nTMS with tractography allows for preoperative assessment of short-term and long-term motor deficits, which may not be possible with fMRI. fMRI data interpretation requires careful consideration of co-activated, non-essential areas (potentially leading to false positives) and situations where neural activity and blood flow are uncoupled (potentially leading to false negatives). These limitations restrict fMRI's role in preoperative planning for both motor and language functions. While MEG offers high accuracy in motor mapping, its high cost and technical complexity contribute to the limited number of available studies. Studies comparing preoperative language mapping techniques with direct cortical stimulation show significant variability across all methods, highlighting the need for larger, multicenter studies for validation. Repetitive nTMS speech mapping offers valuable negative predictive value, allowing clinicians to evaluate whether a patient should undergo awake or asleep surgery. Language function monitoring heavily relies on the specific expertise and experience available at each center, making it challenging to establish general recommendations.

Does Cathodal Preconditioning Enhance the Effects of Subsequent Anodal Transcranial Direct Current Stimulation on Corticospinal Excitability and Grip Strength?

ABSTRACT

Lewis, A, Rattray, B, and Flood, A. Does cathodal preconditioning enhance the effects of subsequent anodal transcranial direct current stimulation on corticospinal excitability and grip strength? J Strength Cond Res 39(1): e1-e12, 2025-Inconsistent effects of transcranial direct current stimulation (tDCS) on corticospinal excitability (CSE) and exercise performance are commonly reported. Cathodal preconditioning, involving cathodal tDCS delivered before anodal tDCS over the same region, may enhance changes in CSE and exercise beyond that resulting from anodal tDCS alone. This study aimed to investigate whether the effects of anodal tDCS on CSE and isometric grip strength can be enhanced by cathodal preconditioning. Thirty-five healthy subjects aged 19-37 years completed a familiarization session followed by 4 stimulation conditions presented in a randomized cross-over design across 4 separate sessions. tDCS doses were applied at 2 mA over the primary motor cortex for 10 minutes. Corticospinal excitability was assessed using 120% of resting motor threshold and an input/output curve of motor evoked potentials of the first dorsal interosseous. Grip strength was evaluated as time to exhaustion (TTE) in a sustained isometric contraction. Relative to conventional sham stimulation, TTE was significantly increased by 15% after conventional anodal tDCS. Corticospinal excitability increased in response to tDCS, but this effect did not differ across conditions. Cathodal preconditioning before anodal stimulation did not increase CSE or grip strength beyond that seen in the other stimulation conditions. Our findings did not reveal any significant impact of stimulation type on CSE. Notably, anodal tDCS led to a significant improvement in grip strength endurance. However, cathodal preconditioning did not seem to increase the effect of subsequent anodal stimulation on CSE nor grip strength.

The Effects of Transcranial Direct Current Stimulation and Exercise on Salivary S100B Protein Indicated Blood-Brain Barrier Permeability: A Pilot Study

OBJECTIVE

This study aimed to assess the effect of transcranial direct current stimulation (tDCS) and exercise on blood-brain barrier (BBB) permeability in humans as assessed through the quantification of the salivary protein biomarker S100B. It was hypothesized that active tDCS would induce a significant increase in salivary S100B concentration when compared with sham stimulation and no stimulation. It also was hypothesized that the increase in salivary S100B concentration would be greater after active tDCS and exercise than after tDCS or exercise alone.

MATERIALS AND METHODS

A total of 13 healthy adults (five male, eight female), ranging in age from 21 to 32 years, underwent three experimental conditions (active tDCS, sham tDCS, inactive control). To assess exercise- and tDCS-induced changes in BBB permeability, S100B in saliva was measured. Saliva samples were taken before tDCS, after tDCS, and immediately after a ramped cycling time-to-exhaustion (TTE) task. Active tDCS involved the application of anodal stimulation over the primary motor cortex for 20 minutes at 2 mA.

RESULTS

S100B concentrations in the control condition did not differ significantly from the active condition (estimate = 0.10, SE = 0.36, t = 0.27, p = 0.79) or the sham condition (estimate = 0.33, SE = 0.36, t = 0.89, p = 0.38). Similarly, S100B concentrations at baseline did not differ significantly from post-intervention (estimate = -0.35, SE = 0.34, t = -1.03, p = 0.31) or post-TTE (estimate = 0.66, SE = 0.34, t = 1.93, p = 0.06).

CONCLUSIONS

This research provides novel insight into the effect of tDCS and exercise on S100B-indicated BBB permeability in humans. Although the effects of tDCS were not significant, increases in salivary S100B after a fatiguing cycling task may indicate exercise-induced changes in BBB permeability.

Corticospinal and Clinical Effects of Muscle Tendon Vibration in Neurologically Impaired Individuals. A Scoping Review

This review verified the extent, variety, quality and main findings of studies that have tested the neurophysiological and clinical effects of muscle tendon vibration (VIB) in individuals with sensorimotor impairments. The search was conducted on PubMed, CINAHL, and SportDiscuss up to April 2024. Studies were selected if they included humans with neurological impairments, applied VIB and used at least one measure of corticospinal excitability using transcranial magnetic stimulation (TMS). Two investigators assessed the studies' quality using critical appraisal checklists and extracted relevant data. The 10 articles included were diverse in populations and methods, generally rated as 'average' to 'good' quality. All studies reported an increased corticospinal excitability in the vibrated muscle, but the effects of VIB on non-vibrated muscles remain unclear. Positive clinical changes in response to VIB were reported in a few studies, such as a decreased spasticity and improved sensorimotor function. These changes were sometimes correlated with corticospinal effects, suggesting a link between VIB-induced plasticity and clinical improvements. Despite the limited and heterogeneous literature, this review supports the facilitatory influence of VIB on motor outputs controlling vibrated muscles, even with altered sensorimotor functions. It highlights knowledge gaps and suggests future research directions on VIB mechanisms and clinical implications.

Efficacy of Transcranial Direct Current Stimulation (tDCS) on Neuropsychiatric Symptoms in Multiple Sclerosis (MS)-A Review and Insight into Possible Mechanisms of Action

Introduction: Neuropsychiatric symptoms such as depression and anxiety are a significant burden on patients with multiple sclerosis (MS). Their pathophysiology is complex and yet to be fully understood. There is an urgent need for non-invasive treatments that directly target the brain and help patients with MS. One such possible treatment is transcranial direct current stimulation (tDCS), a popular and effective non-invasive brain stimulation technique. Methods: This mechanistic review explores the efficacy of tDCS in treating depression and anxiety in MS while focusing on the underlying mechanisms of action. Understanding these mechanisms is crucial, as neuropsychiatric symptoms in MS arise from complex neuroinflammatory and neurodegenerative processes. This review offers insights that may direct more focused and efficient therapeutic approaches by investigating the ways in which tDCS affects inflammation, brain plasticity, and neural connections. Searches were conducted using the PubMed/Medline, ResearchGate, Cochrane, and Google Scholar databases. Results: The literature search yielded 11 studies to be included in this review, with a total of 175 patients participating in the included studies. In most studies, tDCS did not significantly reduce depression or anxiety scores as the studied patients did not have elevated scores indicating depression and anxiety. In the few studies where the patients had scores indicating mild/moderate dysfunction, tDCS was more effective. The risk of bias in the included studies was assessed as moderate. Despite the null or near-null results, tDCS may still prove to be an effective treatment option for depression and anxiety in MS, because tDCS produces a neurobiological effect on the brain and nervous system. To facilitate further work, several possible mechanisms of action of tDCS have been reported, such as the modulation of the frontal-midline theta, reductions in neuroinflammation, the modulation of the HPA axis, and cerebral blood flow regulation. Conclusions: Although tDCS did not overall demonstrate positive effects in reducing depression and anxiety in the studied MS patients, the role of tDCS in this area should not be underestimated. Evidence from other studies indicates the effectiveness of tDCS in reducing depression and anxiety, but the studies included in this review did not include patients with sufficient depression or anxiety. Future studies are needed to confirm the effectiveness of tDCS in neuropsychiatric dysfunctions in MS.

The relationship between corticospinal excitability and structural integrity in stroke patients

BACKGROUND

Evaluation of the structural integrity and functional excitability of the corticospinal tract (CST) is likely to be important in predicting motor recovery after stroke. Previous reports are inconsistent regarding a possible link between CST structure and CST function in this setting. This study aims to investigate the structure‒function relationship of the CST at the acute phase of stroke (<7 days).

METHODS

We enrolled 70 patients who had an acute ischaemic stroke with unilateral upper extremity (UE) weakness. They underwent a multimodal assessment including clinical severity (UE Fugl Meyer at day 7 and 3 months), MRI to evaluate the CST lesion load and transcranial magnetic stimulation to measure the maximum amplitude of motor evoked potential (MEP).

RESULTS

A cross-sectional lesion load above 87% predicted the absence of MEPs with an accuracy of 80.4%. In MEP-positive patients, the CST structure/function relationship was bimodal with a switch from a linear relationship (rho=-0.600, 95% CI -0.873; -0.039, p<0.03) for small MEP amplitudes (<0.703 mV) to a non-linear relationship for higher MEP amplitudes (p=0.72). In MEP-positive patients, recovery correlated with initial severity. In patients with a positive MEP <0.703 mV but not in patients with an MEP ≥0.703 mV, MEP amplitude was an additional independent predictor of recovery. In MEP-negative patients, we failed to identify any factor predicting recovery.

CONCLUSION

This large multimodal study on the structure/function of the CST and stroke recovery proposes a paradigm change for the MEP-positive patients phenotypes and refines the nature of the link between structural integrity and neurophysiological function, with implications for study design and prognostic information.

Adaptive Compensatory Neurophysiological Biomarkers of Motor Recovery Post-Stroke: Electroencephalography and Transcranial Magnetic Stimulation Insights from the DEFINE Cohort Study

OBJECTIVE

This study aimed to explore longitudinal relationships between neurophysiological biomarkers and upper limb motor function recovery in stroke patients, focusing on electroencephalography (EEG) and transcranial magnetic stimulation (TMS) metrics.

METHODS

This longitudinal cohort study analyzed neurophysiological, clinical, and demographic data from 102 stroke patients enrolled in the DEFINE cohort. We investigated the associations between baseline and post-intervention changes in the EEG theta/alpha ratio (TAR) and TMS metrics with upper limb motor functionality, assessed using the outcomes of five tests: the Fugl-Meyer Assessment (FMA), Handgrip Strength Test (HST), Pinch Strength Test (PST), Finger Tapping Test (FTT), and Nine-Hole Peg Test (9HPT).

RESULTS

Our multivariate models identified that a higher baseline TAR in the lesioned hemisphere was consistently associated with poorer motor outcomes across all five assessments. Conversely, a higher improvement in the TAR was positively associated with improvements in FMA and 9HPT. Additionally, an increased TMS motor-evoked potential (MEP) amplitude in the non-lesioned hemisphere correlated with greater FMA-diff, while a lower TMS Short Intracortical Inhibition (SICI) in the non-lesioned hemisphere was linked to better PST improvements. These findings suggest the potential of the TAR and TMS metrics as biomarkers for predicting motor recovery in stroke patients.

CONCLUSION

Our findings highlight the significance of the TAR in the lesioned hemisphere as a predictor of motor function recovery post-stroke and also a potential signature for compensatory oscillations. The observed relationships between the TAR and motor improvements, as well as the associations with TMS metrics, underscore the potential of these neurophysiological measures in guiding personalized rehabilitation strategies for stroke patients.

Accurate determination of motor evoked potential amplitude in TMS: The impact of personal and experimental factors

OBJECTIVE

Corticospinal excitability can be quantified using motor-evoked potentials (MEP) following transcranial magnetic stimulation (TMS). However, the inherent variability of MEPs poses significant challenges. We establish a framework using personal and experimental factors to select the optimal number of trials (nopt) required for reliable MEP estimates.

METHODS

47 healthy younger underwent single-pulse TMS over the left primary motor cortex (M1). Per participant, 550 MEPs were collected at intensities ranging from 110 % to 150 % of the resting motor threshold (rMT), in 10 % increments. Per intensity, we calculated nopt. We analyzed which personal and experimental factors affected nopt.

RESULTS

nopt decreased with increasing TMS intensity, lower rMT baseline values, and exclusion of single-trial outliers. Sex had no significant effect.

CONCLUSIONS

Our study indicates that even when TMS is used as an outcome measure, custom-tailoring its protocol to study-related circumstances is key, as TMS intensity, outliers, baseline rMT, and the desired precision level affect the number of TMS trials needed to obtain a reliable MEP. Thus, we underscore the absence of a universal rule-of-thumb rule, although our predictive equations and online tool provide future TMS experimenters with the means to estimate the required number of TMS trials based on individual characteristics and specific experimental conditions.

SIGNIFICANCE

Our predictive equations offer a tailored approach for selecting nopt, enhancing the reliability of TMS-derived corticospinal excitability measurements.

The test-retest reliability of non-navigated transcranial magnetic stimulation (TMS) measures of corticospinal pathway excitability early after stroke

PURPOSE

Motor evoked potential (MEP) characteristics are potential biomarkers of whether rehabilitation interventions drive motor recovery after stroke. The test-retest reliability of Transcranial Magnetic Stimulation (TMS) measurements in sub-acute stroke remains unclear. This study aims to determine the test-retest reliability of upper limb MEP measures elicited by non-neuronavigated transcranial magnetic stimulation in sub-acute-stroke.

METHODS

In two identical data collection sessions, 1-3 days apart, TMS measures assessed: motor threshold (MT), amplitude, latency (MEP-L), silent period (SP), recruitment curve slope in the biceps brachii (BB), extensor carpi radialis (ECR), and abductor pollicis brevis (APB) muscles of paretic and non-paretic upper limbs. Test-retest reliability was calculated using the intra-class correlation coefficient (ICC) and 95% confidence intervals (CI). Acceptable reliability was set at a lower 95% CI of 0.70 or above. The limits of agreement (LOA) and smallest detectable change (SDC) were calculated.

RESULTS

30 participants with sub-acute stroke were included (av 36 days post stroke) reliability was variable between poor to good for the different MEP characteristics. The SDC values differed across muscles and MEP characteristics in both paretic and less paretic limbs.

CONCLUSIONS

The present findings indicate there is limited evidence for acceptable test-retest reliability of non-navigated TMS outcomes when using the appropriate 95% CI for ICC, SDC and LOA values.

CLINICAL TRIAL REGISTRATION

Current Controlled Trials: ISCRT 19090862, http://www.controlled-trials.com.

Upper extremity neuromuscular function can distinguish between individuals with and without glenohumeral labral repair

The purpose of this study was to determine whether common measures of neuromuscular function could distinguish injury status indicated by group membership (glenohumeral labral repair, uninjured controls). 16 individuals with glenohumeral labral repair (24.1 ± 5.0 years, 36.7 ± 33.3 months after surgery) and 14 uninjured controls (23.8 ± 2.7 years) volunteered. We measured mass-normalized shoulder abduction and wrist flexion maximal voluntary isometric contraction torque (Nm/kg), motoneuron pool excitability of the flexor carpi radialis (Hoffmann reflex), corticospinal excitability of the upper trapezius, middle deltoid, and flexor carpi radialis (active motor threshold [%]) bilaterally. Receiver operator characteristic curve analyses were performed to determine if each outcome could distinguish injury status along with their outcome thresholds. Binary logistic regression was used to determine the accuracy of classification for each outcome. Our results suggest shoulder abduction torque symmetry (≤95.5 %) and corticospinal excitability for the upper trapezius (≥41.0 %) demonstrated excellent diagnostic utility. Shoulder abduction torque (≤0.71 Nm/kg) and motoneuron pool excitability (≤0.23) demonstrated acceptable diagnostic utility. Shoulder abduction torque symmetry alone was the strongest indicator, and classified injury status with 90.0 % accuracy (p < 0.01). Overall, symmetric shoulder abduction strength most accurately distinguished individuals' injury status, suggesting the utility of bilateral assessment in this population.

Corticospinal excitability and voluntary activation of the quadriceps muscle is not affected by a single session of anodal transcutaneous spinal direct current stimulation in healthy, young adults

The aim of the present study was to determine if anodal transcutaneous spinal direct current stimulation (tsDCS) affects corticospinal excitability (CSE) and voluntary activation (VA) of the quadriceps femoris muscle (QM). This was a double-blind, randomized study in which spine-shoulder anodal tsDCS (active electrode centered over T11-12, 2.5 mA, 20 min) was applied in a seated position. Transcranial magnetic stimulation (TMS) was used to measure motor evoked potentials (MEP) and construct stimulus-response curves in healthy participants (eight females and five males, Experiment 1). VA was measured via the interpolated twitch technique, whereby muscle twitches were evoked using electrical femoral nerve stimulation and TMS (seven females and six males, Experiment 2). Measurements were carried out before, directly, and 30 min after sham and anodal tsDCS (with ≥4 days between sessions). There was no interaction between stimulation × time on stimulus-response curve expressed by slope, stimulus intensity corresponding to 50% of the maximal MEP, and peak-to-peak amplitude of the maximal MEP. Maximal voluntary isometric contraction (MVIC) torque did not change and VA was not affected regardless of the QM torque level (25, 50, or 100% of MVIC). A single, twenty-minute session of spine-shoulder anodal tsDCS did not increase CSE and VA of QM during submaximal and maximal contraction. This suggests that neither excitability to a known input nor responsiveness of motoneurons to submaximal and maximal cortical drive were affected by anodal tsDCS.

Impact of a mandibular advancement device on corticomotor plasticity in patients with obstructive sleep apnea

BACKGROUND

Neuroplasticity induced by mandibular advancement appliance (MAD) in patients with obstructive sleep apnoea (OSA) is poorly documented.

OBJECTIVE

This randomised placebo-controlled crossover mechanistic study assessed the effects of short-term use of a MAD on corticomotor excitability of the masseter and tongue in patients with OSA.

METHODS

Adults (n = 28) with mild or moderate OSA were randomly allocated to sleep with a MAD for 2-weeks with 40% of the maximal protrusion (MAD active position) and without any jaw protrusion (MAD placebo position). The outcomes were assessed at baseline, and after 2 and 6 weeks, with a 2-week washout period. The primary outcome was the amplitude of motor evoked potential (MEP) assessed on the right masseter, right side of tongue and right first dorsal interosseous with transcranial magnetic stimulation. Corticomotor map volume of the same muscles was also assessed. Repeated-measures ANOVAs followed by Tukey test were applied to the data (p < .050).

RESULTS

There was a significant increase in the MEP amplitude of the masseter and tongue following the MAD active position compared with the baseline and MAD placebo (Tukey: p < .001). There were no significant MEP amplitude differences between the baseline and placebo positions (p > .050). Moreover, there was a significant increase in corticomotor map volume for the masseter and tongue muscles following the MAD active position compared with baseline and MAD placebo (Tukey: p < .003).

CONCLUSION

Excitability of the masseter and tongue motor pathways is, at least transiently, increased in patients with OSA following a short-term use of MAD. This novel finding of MAD-induced neuroplasticity in corticomotor pathways may contribute to a further understanding of the mechanisms of oral appliances for treating OSA.

Topographically selective motor inhibition under threat of pain

ABSTRACT

Pain-related motor adaptations may be enacted predictively at the mere threat of pain, before pain occurrence. Yet, in humans, the neurophysiological mechanisms underlying motor adaptations in anticipation of pain remain poorly understood. We tracked the evolution of changes in corticospinal excitability (CSE) as healthy adults learned to anticipate the occurrence of lateralized, muscle-specific pain to the upper limb. Using a Pavlovian threat conditioning task, different visual stimuli predicted pain to the right or left forearm (experiment 1) or hand (experiment 2). During stimuli presentation before pain occurrence, single-pulse transcranial magnetic stimulation was applied over the left primary motor cortex to probe CSE and elicit motor evoked potentials from target right forearm and hand muscles. The correlation between participants' trait anxiety and CSE was also assessed. Results showed that threat of pain triggered corticospinal inhibition specifically in the limb where pain was expected. In addition, corticospinal inhibition was modulated relative to the threatened muscle, with threat of pain to the forearm inhibiting the forearm and hand muscles, whereas threat of pain to the hand inhibited the hand muscle only. Finally, stronger corticospinal inhibition correlated with greater trait anxiety. These results advance the mechanistic understanding of pain processes showing that pain-related motor adaptations are enacted at the mere threat of pain, as sets of anticipatory, topographically organized motor changes that are associated with the expected pain and are shaped by individual anxiety levels. Including such anticipatory motor changes into models of pain may lead to new treatments for pain-related disorders.

Cortical intermittent theta burst stimulation on gait pathomechanics and urinary tract dysfunction in incomplete spinal cord injury patients: Protocol for a randomized controlled trial

Gait impairment and neurogenic bladder are co-existing common findings in incomplete spinal cord injury (iSCI). Repetitive transcranial magnetic stimulation (rTMS), evident to be a promising strategy adjunct to physical rehabilitation to regain normal ambulation in SCI. However, there is a need to evaluate the role of Intermittent theta burst stimulation (iTBS), a type of patterned rTMS in restoring gait and neurogenic bladder in SCI patients. The aim of the present study is to quantify the effect of iTBS on spatiotemporal, kinetic, and kinematic parameters of gait and neurogenic bladder dyssynergia in iSCI. After maturing all exclusion and inclusion criteria, thirty iSCI patients will be randomly divided into three groups: Group-A (sham), Group-B (active rTMS) and Group-C (active iTBS). Each group will receive stimulation adjunct to physical rehabilitation for 2 weeks. All patients will undergo gait analysis, as well assessment of bladder, electrophysiological, neurological, functional, and psychosocial parameters. All parameters will be assessed at baseline and 6th week (1st follow-up). Parameters except urodynamics and gait analysis will also be assessed after the end of the 2 weeks of the intervention (post-intervention) and at 12th week (2nd follow-up). Appropriate statistical analysis will be done using various parametric and non-parametric tests based on results.

The effectiveness of theta burst stimulation for motor recovery after stroke: a systematic review

BACKGROUND

Stroke is the second leading cause of death and the third leading cause of disability worldwide. Motor dysfunction is a common sequela, which seriously affects the lives of patients. Theta burst stimulation (TBS) is a new transcranial magnetic therapy for improving motor dysfunction after stroke. However, there remains a lack of studies on the mechanism, theoretical model, and effectiveness of TBS in improving motor dysfunction following stroke.

OBJECTIVE

This paper provides a comprehensive overview and assessment of the current impact of TBS on motor rehabilitation following stroke and analyzes potential factors contributing to treatment effect disparities. The aim is to offer recommendations for further refining the TBS treatment approach in subsequent clinical studies while also furnishing evidence for devising tailored rehabilitation plans for stroke patients.

METHODS

This study was conducted following PRISMA guidelines. PubMed, Embase, Web of Science, and the Cochrane Library were searched systematically from the establishment of the database to February 2024. Relevant studies using TBS to treat patients with motor dysfunction after stroke will be included. Data on study characteristics, interventions, outcome measures, and primary outcomes were extracted. The Modified Downs and Black Checklist was used to assess the potential bias of the included studies, and a narrative synthesis of the key findings was finally conducted.

RESULTS

The specific mechanism of TBS in improving motor dysfunction after stroke has not been fully elucidated, but it is generally believed that TBS can improve the functional prognosis of patients by regulating motor cortical excitability, inducing neural network reorganization, and regulating cerebral circulation metabolism. Currently, most relevant clinical studies are based on the interhemispheric inhibition model (IHI), the vicariation model, and the bimodal balance-recovery model. Many studies have verified the effectiveness of TBS in improving the motor function of stroke patients, but the therapeutic effect of some studies is controversial.

CONCLUSION

Our results show that TBS has a good effect on improving motor function in stroke patients, but more large-scale, high-quality, multicenter studies are still necessary in the future to further clarify the mechanism of TBS and explore the optimal TBS treatment.

Shaping tomorrow: how the STEP training course pioneered noninvasive brain stimulation training for psychiatry in France

Over the past three decades, non-invasive brain stimulation (NIBS) techniques have gained worldwide attention and demonstrated therapeutic potential in various medical fields, particularly psychiatry. The emergence of these novel techniques has led to an increased need for robust training programs to provide practitioners, whether clinicians or scientists, with the necessary skills and knowledge. In response, a comprehensive training curriculum for NIBS in psychiatry has been developed in France. This curriculum was developed by a group of researchers and psychiatrists interested in the clinical application of NIBS in psychiatry, called STEP - Stimulation Transcranienne en Psychiatrie, under the auspices of the French Association of Biological Psychiatry. This perspective outlines the development and implementation of this course, tracing its inception, the evolution of the program, and the challenges encountered along the way. The position of the course in the national and international environment and its future prospects are also discussed. Through this perspective, we aim to summarize the collaborative efforts to promote NIBS teaching and research in French psychiatry.

Central motor conduction time predicts new pyramidal MRI lesion and stroke-in-evolution in acute ischemic stroke

Stroke is one of the leading causes of disability worldwide. Stroke-in-evolution is an essential issue as it is often associated with a worse outcome. Central motor conduction time (CMCT) is the time required for neural impulses to travel through the central nervous system to the target muscles. CMCT prolongation indicates dysfunction of the corticospinal tract. This study aims to investigate the impact of CMCT on clinical features and MRI characteristics in patients with acute ischemic stroke. A total of 94 patients with suspected acute ischemic stroke, with an average age of 67.13 ± 10.73 years old and 69.15 % being male, were enrolled in this study. All patients underwent evaluation for stroke risk factors, medical record review, CMCT examination (with CMCT (+) indicating CMCT prolongation), cranial MRI examinations, and data analysis. Compared to CMCT (-), the number of CMCT (+) subjects was significantly higher in all groups except the "Ever Stroke" group. The CMCT (+) group exhibited significantly higher values of "NIHSS" and "mRS" compared to the CMCT (-) group. After ANCOVA adjustment, the number of CMCT (+) subjects remained significantly higher only in the radiologically classified "New Pyramidal Lesion on MRI" and clinically classified "Stroke-In-Evolution" groups. In conclusion, CMCT serves as both a diagnostic indicator of acute ischemic stroke with weakness accompanied by new pyramidal lesions on brain MRI, rather than weakness associated with old lesions on brain MRI, and as a predictive marker for stroke progression during hospitalization.

Unconscious goal pursuit strengthens voluntary force during sustained maximal effort via enhanced motor system state

Maximal voluntary force is known to be enhanced by shouting during sustained maximal voluntary contraction (MVC) via the enhancement of motor cortical excitability. However, whether excitatory input to the primary motor cortex from areas other than the motor-related cortical area induces muscular force-enhancing effects on the exertion of sustained maximal force remains unclear. Therefore, by examining motor evoked potentials to transcranial magnetic stimulation during sustained MVC and assessing handgrip force, the present study aimed to investigate the effects of subliminal goal-priming with motivational rewards on the state of the motor system. The findings revealed that when combined with rewards in the form of a consciously visible positive stimulus, barely visible priming of an action concept increased the maximal voluntary force and reduced the silent period (i.e., reduced motor cortical inhibition). To our knowledge, this is the first study to report a link between the muscular force of subliminal reward-goal priming during MVC and the enhancement of motor system activity through subliminal reward-goal priming operating on the motor system, possibly through the potentiation of activity of the reward-linked dopaminergic system.

Functional motor network abnormalities associated with levodopa-induced dyskinesia in Parkinson's disease: A systematic review

Parkinson's disease (PD) can be effectively treated with levodopa and dopamine agonists but leads to levodopa-induced dyskinesia (LID) in most patients in the long run. Various functional brain mapping techniques are used to explore alterations in motor networks associated with LID. This pre-registered review (PROSPERO: CRD42022320830) summarizes the motor network abnormalities reported in functional brain mapping studies of patients with LID. We included studies using functional MRI, EEG, PET, SPECT, or TMS and included at least 10 LID patients. For completeness, we included studies of 5-9 patients with LID in a table. Some of these were also incorporated into the review if other studies used the same method. Thirty studies met our pre-defined criteria. Patients with LID showed stronger motor-related activation and functional connectivity of motor and premotor cortical areas and the putamen after levodopa intake relative to PD patients without LID. Decreased activation was found in the right inferior frontal cortex. TMS studies showed increased cortical excitability and blunted cortical plasticity in patients with LID, while "inhibitory" repetitive TMS of prefrontal motor control areas and cerebellum produced transient anti-dyskinetic effects. Overall, sample sizes were small, the number of studies per mapping modality was limited, and most studies lacked independent replication. The alterations associated with LID encompass changes in functional activity, connectivity, cortical excitability, and plasticity in motor execution and motor control networks. A comprehensive understanding of how LID manifests at the motor network level will guide the future development of stimulation-based network therapies for LID.

Cerebellar repetitive transcranial magnetic stimulation has no effect on contraction-induced facilitation of corticospinal excitability

This study aimed to investigate whether the cerebellum contributes to contraction-induced facilitation (CIF) of contralateral corticospinal excitability. To this end, repetitive cerebellar transcranial magnetic stimulation (TMS) was used to test whether it modulates CIF. Overall, 20 healthy young individuals participated in the study. Single-pulse TMS was applied to the left primary motor cortex to induce motor-evoked potentials (MEP) on electromyography of the right first dorsal interosseous (FDI) muscle to test corticospinal excitability. This measurement was conducted during contraction (10% maximum voluntary contraction [MVC]) and rest (0% MVC) of the FDI muscle. CIF, cerebellar brain inhibition (CBI), cortical silent period (cSP), and resting motor threshold (rMT) were measured before and after low-frequency repetitive TMS (crTMS) of the right cerebellum to downregulate cerebellar output. The CIF (contraction/rest of the MEP), CBI (conditioned/unconditioned MEP) during contraction, cSP, and rMT were not affected by crTMS. At rest, CBI was decreased. These findings indicated that the primary motor cortex function for the increase in corticospinal excitability was not affected by crTMS. This study contributes to our understanding of the role of the cerebellum in motor control. Additionally, it may inform decision-making for the site of cerebellar ataxia treatment using non-invasive brain stimulation.

Knee joint pathology and efferent pathway dysfunction: Mapping muscle inhibition from motor cortex to muscle force

BACKGROUND

Dysfunction in efferent pathways after knee pathology is tied to long-term impairments in quadriceps and hamstrings muscle performance, daily function, and health-related quality of life. Understanding the underlying etiology is crucial for effective treatment and prevention of poor outcomes, such as post-traumatic osteoarthritis or joint replacement.

OBJECTIVES

To synthesize recent evidence of efferent pathway dysfunction (i.e., motor cortex, motor units) among individuals with knee pathology.

DESIGN

Commentary.

METHOD

We summarize the current literature investigating the motor cortex, corticospinal tract, and motoneuron pool in individuals with three common knee pathologies: anterior cruciate ligament (ACL) injury, anterior knee pain (AKP), and knee osteoarthritis (OA). To offer a complete perspective, we draw from studies applying a range of neuroimaging and neurophysiologic techniques.

RESULTS

Adaptations within the motor cortices, corticospinal tract, and motoneuron pool are present in those with knee pathology and underline impairments in quadriceps and hamstrings muscle function. Each pathology has evidence of altered motor system excitability and reduced volitional muscle activation and force-generating capacity, but few impairments were common across ACL injury, AKP, and OA studies. These findings underscore the central role of the motor cortex and motor unit behavior in the long-term outcomes of individuals with knee pathology.

CONCLUSIONS

Adaptations in the efferent pathways underlie persistent muscle dysfunction across three common knee pathologies. This review provides an overview of these changes and summarizes key findings from neurophysiology and neuroimaging studies, offering direction for future research and clinical application in the rehabilitation of joint injuries.

A comparison of techniques to determine active motor threshold for transcranial magnetic stimulation research

The determination of active motor threshold (AMT) is a critical step in transcranial magnetic stimulation (TMS) research. As AMT is frequently determined using an absolute electromyographic (EMG) threshold (e.g., 200 µV peak-to-peak amplitude), wide variation in EMG recordings across participants has given reason to consider relative thresholds (e.g., = 2 × background sEMG) for AMT determination. However, these approaches have not been systemically compared. Our purpose was to compare AMT estimations derived from absolute and relative criteria commonly used in the quadriceps, and assess the test-retest reliability of each approach. We used a repeated measures design to assess AMT estimations in the vastus lateralis (VL) from eighteen young adults (9 males and 9 females; mean ± SD age = 23 ± 2 years) across two laboratory visits. AMT was determined for each criterion, at each lab visit. A paired samples t-test was used to compare mean differences in AMT estimations during the second laboratory visit. Paired samples t-tests and intraclass correlation coefficients (ICC2,1) were calculated to assess test-retest reliability of each criterion. Differences between the criteria were small and not statistically significant (p = 0.309). The absolute criterion demonstrated moderate to excellent reliability (ICC2,1 = 0.866 [0.648-0.950]), but higher AMTs were observed in the second visit (p = 0.043). The relative criteria demonstrated good-to-excellent test-retest reliability (ICC2,1 = 0.894 [0.746-0.959]) and AMTs were not different between visits (p = 0.420). TMS researchers aiming to track corticospinal characteristics across visits should consider implementing relative criterion approaches during their AMT determination protocol.

Modulation of electroencephalogram brain activity dynamics by 10 Hz parietal repetitive transcranial magnetic stimulation: Implications for recovery of the minimally conscious state

BACKGROUND AND OBJECTIVES

Despite the fact that the parietal cortex is associated with consciousness, the underlying mechanisms of parietal repetitive transcranial magnetic stimulation (rTMS) have not yet been specifically investigated. The present study aims to examine the effects of parietal rTMS on patients with disorders of consciousness (DoC) and identify a novel potential target.

METHODS

Twenty minimally conscious state (MCS) patients were stochastically assigned to a real or sham rTMS group in a controlled trial. The real rTMS group was administered over the parietal cortex, with a frequency of 10 Hz and a rest motor threshold of 90 %. The sham rTMS group was identical to the real rTMS group without magnetic stimulation over the cortex. Pre- and post-treatment resting-state electrophysiological (EEG) data and coma recovery scale-revised (CRS-R) score were gathered. Microstate analyses were calculated to evaluate the brain activity dynamics.

RESULTS

The real rTMS treatment improved the CRS-R scores. There were notable alterations in the mean microstate duration (MMD) of microstate B in the real rTMS group. The sham rTMS group did not exhibit such changes in CRS-R score or EEG results, which were not statistically significant. Furthermore, the MMD and RTC of microstate E were found to be negatively correlated with baseline CRS-R scores.

CONCLUSION

Parietal rTMS can induce behavioral improvement and brain activity dynamics in patients with MCS. EEG microstates can be used as a valuable method to study neurophysiological mechanisms behind MCS. And the parietal cortex represents an alternative for rTMS therapy protocols.

Brain metabolic response to repetitive transcranial magnetic stimulation to lesion network in cervical dystonia

BACKGROUND

A previous study identified a brain network underlying cervical dystonia (CD) based on causal brain lesions. This network was shown to be abnormal in idiopathic CD and aligned with connections mediating treatment response to deep brain stimulation, suggesting generalizability across etiologies and relevance for treatment. The main nodes of this network were located in the deep cerebellar structures and somatosensory cortex (S1), the latter of which can be easily reached via non-invasive brain stimulation. To date, there are no studies testing brain stimulation to networks identified using lesion network mapping.

OBJECTIVES

To assess target engagement by stimulating the S1 and testing the brain's acute metabolic response to repetitive transcranial magnetic stimulation in CD patients and healthy controls.

METHODS

Thirteen CD patients and 14 controls received a single session of continuous theta burst (cTBS) and sham to the right S1. Changes in regional brain glucose metabolism were measured using [18F]FDG-PET.

RESULTS

cTBS increased metabolism at the stimulation site in CD (P = 0.03) but not in controls (P = 0.15; group difference P = 0.01). In subcortical regions, cTBS increased metabolism in the brainstem in CD only (PFDR = 0.04). The remote activation was positively associated with dystonia severity and efficacy of sensory trick phenomenon in CD patients.

CONCLUSIONS

Our results provide further evidence of abnormal sensory system function in CD and show that a single session of S1 cTBS is sufficient to induce measurable changes in brain glucose metabolism. These findings support target engagement, motivating therapeutic trials of cTBS to the S1 in CD.

Repetitive transcranial magnetic stimulation alleviates motor impairment in Parkinson's disease: association with peripheral inflammatory regulatory T-cells and SYT6

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) has been used to treat various neurological disorders. However, the molecular mechanism underlying the therapeutic effect of rTMS on Parkinson's disease (PD) has not been fully elucidated. Neuroinflammation like regulatory T-cells (Tregs) appears to be a key modulator of disease progression in PD. If rTMS affects the peripheral Tregs in PD remains unknown.

METHODS

Here, we conducted a prospective clinical study (Chinese ClinicalTrials. gov: ChiCTR 2100051140) involving 54 PD patients who received 10-day rTMS (10 Hz) stimulation on the primary motor cortex (M1) region or sham treatment. Clinical and function assessment as well as flow cytology study were undertaken in 54 PD patients who were consecutively recruited from the department of neurology at Zhujiang hospital between September 2021 and January 2022. Subsequently, we implemented flow cytometry analysis to examine the Tregs population in spleen of MPTP-induced PD mice that received rTMS or sham treatment, along with quantitative proteomic approach reveal novel molecular targets for Parkinson's disease, and finally, the RNA interference method verifies the role of these new molecular targets in the treatment of PD.

RESULTS

We demonstrated that a 10-day rTMS treatment on the M1 motor cortex significantly improved motor dysfunction in PD patients. The beneficial effects persisted for up to 40 days, and were associated with an increase in peripheral Tregs. There was a positive correlation between Tregs and motor improvements in PD cases. Similarly, a 10-day rTMS treatment on the brains of MPTP-induced PD mice significantly ameliorated motor symptoms. rTMS reversed the downregulation of circulating Tregs and tyrosine hydroxylase neurons in these mice. It also increased anti-inflammatory mediators, deactivated microglia, and decreased inflammatory cytokines. These effects were blocked by administration of a Treg inhibitor anti-CD25 antibody in MPTP-induced PD mice. Quantitative proteomic analysis identified TLR4, TH, Slc6a3 and especially Syt6 as the hub node proteins related to Tregs and rTMS therapy. Lastly, we validated the role of Treg and rTMS-related protein syt6 in MPTP mice using the virus interference method.

CONCLUSIONS

Our clinical and experimental studies suggest that rTMS improves motor function by modulating the function of Tregs and suppressing toxic neuroinflammation. Hub node proteins (especially Syt6) may be potential therapeutic targets.

TRIAL REGISTRATION

Chinese ClinicalTrials, ChiCTR2100051140. Registered 15 December 2021, https://www.chictr.org.cn/bin/project/edit?pid=133691.

Dosing overground robotic gait training after spinal cord injury: a randomized clinical trial protocol

BACKGROUND

Robotic exoskeletons have changed rehabilitation care available to people after spinal cord injury (SCI). Yet, the current evidence base is insufficient to identify the optimal dose and neurophysiological mechanism of robotic exoskeleton gait training (RGT) as an effective rehabilitation approach. This study will (1) examine whether the frequency of RGT after motor incomplete SCI impacts function and health outcomes, (2) analyze the neuroplastic effects of RGT dose, and (3) evaluate the safety, tolerability, and feasibility of delivering RGT.

METHODS

We will enroll 144 participants with motor incomplete SCI admitted to inpatient rehabilitation within 6 months of SCI. Participants will be randomized based on injury severity and level into one of 3 RGT frequency groups (high, moderate, low) or none/usual care only. Participants will complete 24 RGT sessions and be assessed at admission and discharge to inpatient rehabilitation, post-RGT intervention, 1-month post-RGT, and 9-month post-SCI. Outcomes include Walking Index for Spinal Cord Injury-II, health outcomes (gait speed, Spinal Cord Independence Measure, pain, fatigue, spasticity, general health, quality of life, physical activity), and motor evoked potential amplitudes obtained using transcranial magnetic stimulation.

DISCUSSION

Successful completion of this study will provide an evidence-based intervention, specifically tailored to meet the unique needs of people with SCI, which supports walking recovery; maximizing health, function, and ultimately participation. The intervention will further support widespread clinical implementation of exoskeleton use during acute rehabilitation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05218447. Registered on June 23, 2022.

A 12-week in-phase bilateral upper limb exercise protocol promoted neuroplastic and clinical changes in people with relapsing remitting multiple sclerosis: A registered report randomized single-case concurrent multiple baseline study

INTRODUCTION

Relapsing-Remitting Multiple Sclerosis manifests various motor symptoms including impairments in corticospinal tract integrity, whose symptoms can be assessed using transcranial magnetic stimulation. Several factors, such as exercise and interlimb coordination, can influence the plastic changes in corticospinal tract. Previous work in healthy and chronic stroke survivors showed that the greatest improvement in corticospinal plasticity occurred during in-phase bilateral exercises of the upper limbs. Altered corticospinal plasticity due to bilateral lesions in the central nervous system is common after Multiple Sclerosis, yet the effect of in-phase bilateral exercise on the bilateral corticospinal plasticity in this cohort remains unclear. Our aim was to investigate the effects of in-phase bilateral exercises on central motor conduction time, motor evoked potential amplitude and latency, motor threshold and clinical measures in people with Relapsing-Remitting Multiple Sclerosis.

METHODS

Five people were randomized and recruited in this single case concurrent multiple baseline design study. The intervention protocol lasted for 12 consecutive weeks (30-60 minutes /session x 3 sessions / week) and included in-phase bilateral upper limb movements, adapted to different sports activities and to functional motor training. To define the functional relation between the intervention and the results, we conducted a visual analysis. If a potential sizeable effect was observed, we subsequently performed a statistical analysis.

RESULTS

Results demonstrated bilateral reduction of the motor threshold alongside with improvement of all clinical measures, but not in any other corticospinal plasticity measures.

CONCLUSION

Our preliminary findings suggest that in-phase bilateral exercise affects motor threshold in people with Relapsing-Remitting Multiple Sclerosis. Therefore, this measure could potentially serve as a proxy for detecting corticospinal plasticity in this cohort. However, future studies with larger sample sizes should validate and potentially establish the effect of in-phase bilateral exercise on the corticospinal plasticity and clinical measures in this cohort.

TRIAL REGISTRATION

Clinical trial registration: ClinicalTrials.gov NCT05367947.