Resting Motor Threshold, MEP and TEP Variability During Daytime

Transcranial application of magnetic pulses for improving brain drug delivery efficiency via intranasal injection of magnetic nanoparticles

As the blood-brain barrier (BBB) hinders efficient drug delivery to the brain, drug delivery via the intranasal pathway, bypassing the BBB, has received considerable attention. However, intranasal administration still has anatomical and physiological limitations, necessitating further solutions to enhance effectiveness. In this study, we used transcranial magnetic stimulation (TMS) on fluorescent magnetic nanoparticles (MNPs) of different sizes (50, 100, and 300 nm) to facilitate MNP's transportation and delivery to the brain parenchyma. To validate this concept, anesthetized rats were intranasally injected with the MNPs, and TMS was applied to the center of the head. As the result, a two-fold increase in brain MNP delivery was achieved using TMS compared with passive intranasal administration. In addition, histological analysis that was performed to investigate the safety revealed no gross or microscopic damages to major organs caused by the nanoparticles. While future studies should establish the delivery conditions in humans, we expect an easy clinical translation in terms of device safety, similar to the use of conventional TMS. The strategy reported herein is the first critical step towards effective drug transportation to the brain.

A protocol for a multicenter randomized and personalized controlled trial using rTMS in patients with disorders of consciousness

Background

Improving the functional recovery of patients with DoC remains one of the greatest challenges of the field. Different theories exist about the role of the anterior (prefrontal areas) versus posterior (parietal areas) parts of the brain as hotspots for the recovery of consciousness. Repetitive transcranial magnetic stimulation (rTMS) is a powerful non-invasive brain stimulation technique for the treatment of DoC. However, a direct comparison of the effect of TMS treatment on the front versus the back of the brain has yet to be performed. In this study, we aim to assess the short- and long-term effects of frontal and parietal rTMS on DoC recovery and characterize responders phenotypically.

Methods/design

Ninety patients with subacute and prolonged DoC will be included in a two-part multicenter prospective study. In the first phase (randomized controlled trial, RCT), patients will undergo four rTMS sessions in a crossover design over 10 days, targeting (i) the left dorsolateral prefrontal cortex (DLPFC) and (ii) the left angular gyrus (AG), as well as (iii & iv) their sham alternatives. In the second phase (longitudinal personalized trial), patients will receive personalized stimulations for 20 working days targeting the brain area that showed the best results in the RCT and will be randomly assigned to either active or sham intervention. The effects of rTMS on neurobehavioral and neurophysiological functioning in patients with DoC will be evaluated using clinical biomarkers of responsiveness (i.e., the Coma Recovery Scale-Revised; CRS-R), and electrophysiological biomarkers (e.g., power spectra, functional and effective connectivity, perturbational complexity index before and after intervention). Functional long-term outcomes will be assessed at 3 and 6 months post-intervention. Adverse events will be recorded during the treatment phase.

Discussion

This study seeks to identify which brain region (front or back) is best to stimulate for the treatment of patients with DoC using rTMS, and to characterize the neural correlates of its action regarding recovery of consciousness and functional outcome. In addition, we will define the responders' profile based on patients' characteristics and functional impairments; and develop biomarkers of responsiveness using EEG analysis according to the clinical responsiveness to the treatment.

Clinical Trial Registration

https://clinicaltrials.gov/ct2/show/NCT04401319, Clinicaltrials.gov, n° NCT04401319.

Motor potentials evoked by transcranial magnetic stimulation: interpreting a simple measure of a complex system

Transcranial magnetic stimulation (TMS) is a non-invasive technique that is increasingly used to study the human brain. One of the principal outcome measures is the motor-evoked potential (MEP) elicited in a muscle following TMS over the primary motor cortex (M1), where it is used to estimate changes in corticospinal excitability. However, multiple elements play a role in MEP generation, so even apparently simple measures such as peak-to-peak amplitude have a complex interpretation. Here, we summarize what is currently known regarding the neural pathways and circuits that contribute to the MEP and discuss the factors that should be considered when interpreting MEP amplitude measured at rest in the context of motor processing and patients with neurological conditions. In the last part of this work, we also discuss how emerging technological approaches can be combined with TMS to improve our understanding of neural substrates that can influence MEPs. Overall, this review aims to highlight the capabilities and limitations of TMS that are important to recognize when attempting to disentangle sources that contribute to the physiological state-related changes in corticomotor excitability.

Physiological symmetry of transcranial magnetic stimulation-evoked EEG spectral features

Transcranial magnetic stimulation (TMS)-evoked EEG potentials (TEPs) have been used to study the excitability of different cortical areas (CAs) in humans. Characterising the interhemispheric symmetry of TMS-EEG may provide further understanding of structure-function association in physiological and pathological conditions. We hypothesise that, in keeping with the underlying cytoarchitectonics, TEPs in contralateral homologous CAs share similar, symmetric spectral features, whilst ipsilateral TEPs from different CAs diverge in their waveshape and frequency content. We performed single-pulse (<1 Hz) navigated monophasic TMS, combined with high-density EEG with active electrodes, in 10 healthy participants. We targeted two bilateral CAs: premotor and motor. We compared frequency power bands, computed Pearson correlation coefficient (R) and Correlated Component Analysis (CorrCA) to detect divergences, as well as common components across TEPs. The main frequency of TEPs was faster in premotor than in motor CAs (p < .05) across all participants. Frequencies were not different between contralateral homologous CAs, whilst, despite closer proximity, there was a significant difference between ipsilateral premotor and motor CAs (p > .5), with frequency decreasing from anterior to posterior CAs. Correlation was high between contralateral homologous CAs and low between ipsilateral CAs. When applying CorrCA, specific components were shared by contralateral homologous TEPs. We show physiological symmetry of TEP spectral features between contralateral homologous CAs, whilst ipsilateral premotor and motor TEPs differ despite lower geometrical distance. Our findings support the role of TEPs as biomarker of local cortical properties and provide a first reference dataset for TMS-EEG studies in asymmetric brain disorders.

Anesthesia inhibited corticospinal excitability and attenuated the modulation of repetitive transcranial magnetic stimulation

BACKGROUND

Lots of studies have measured motor evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) in anesthetized animals. However, in awake animals, the measurement of TMS-induced MEP is scarce as lack of sufficient restraint. So far, the explicit study of anesthesia effects on corticospinal excitability and repetitive TMS (rTMS) induced modulation is still lacking. This study aimed to: (1) measure TMS-induced MEP in both awake restrained and anesthetized rats, (2) investigate the effect of anesthesia on corticospinal excitability, and (3) on rTMS-induced modulation.

METHODS

MEP of eighteen rats were measured under both wakefulness and anesthesia using flexible binding and surface electrodes. Peak-to-peak MEP amplitudes, resting motor threshold (RMT) and the slope of stimulus response (SR) were extracted to investigate anesthesia effects on corticospinal excitability. Thereafter, 5 or 10 Hz rTMS was applied with 600 pulses, and the increase in MEP amplitude and the decrease in RMT were used to quantify rTMS-induced modulation.

RESULTS

The RMT in the awake condition was 44.6 ± 1.2% maximum output (MO), the peak-to-peak MEP amplitude was 404.6 ± 48.8 μV at 60% MO. Under anesthesia, higher RMT (55.6 ± 2.9% MO), lower peak-to-peak MEP amplitudes (258.6 ± 32.7 μV) and lower slope of SR indicated that the corticospinal excitability was suppressed. Moreover, under anesthesia, high-frequency rTMS still showed significant modulation of corticospinal excitability, but the modulation of MEP peak-to-peak amplitudes was weaker than that under wakefulness.

CONCLUSIONS

This study measured TMS-induced MEP in both awake and anesthetized rats, and provided explicit evidence for the inhibitory effects of anesthesia on corticospinal excitability and on high-frequency rTMS-induced modulation of MEP.

Fast acquisition of resting motor threshold with a stimulus-response curve - Possibility or hazard for transcranial magnetic stimulation applications?

Objective

Previous research has suggested that transcranial magnetic stimulation (TMS) related cortical excitability measures could be estimated quickly using stimulus-response curves with short interstimulus intervals (ISIs). Here we evaluated the resting motor threshold (rMT) estimated with these curves.

Methods

Stimulus-response curves were measured with three ISIs: 1.2-2 s, 2-3 s, and 3-4 s. Each curve was formed with 108 stimuli using stimulation intensities ranging from 0.75 to 1.25 times the rMT_guess, which was estimated based on motor evoked potential (MEP) amplitudes of three scout responses.

Results

The ISI did not affect the rMT estimated from the curves (F = 0.235, p = 0.683) or single-trial MEP amplitudes at the group level (F = 0.90, p = 0.405), but a significant subject by ISI interaction (F = 3.64; p < 0.001) was detected in MEP amplitudes. No trend was observed which ISI was most excitable, as it varied between subjects.

Conclusions

At the group level, the stimulus-response curves are unaffected by the short ISI. At the individual level, these curves are highly affected by the ISI.

Significance

Estimating rMT using stimulus-response curves with short ISIs impacts the rMT estimate and should be avoided in clinical and research TMS applications.

Impact of operator experience on transcranial magnetic stimulation

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Response variability to transcranial magnetic stimulation (TMS) is a crucial issue.

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An operator’s experience in TMS may affect the result of resting motor threshold measurement.

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A beginner may have higher consistency in 1 mV motor evoked potential with practice.

Objective

To determine the impact of an operator’s experience on transcranial magnetic stimulation (TMS) measurement.

Methods

Operator B (beginner), operator E (expert), and 30 healthy participants joined the study consisting of two experiments. In each experiment, each operator performed a TMS protocol on each participant in a random order.

Results

Compared with operator E, operator B exhibited higher resting motor threshold (RMT) in experiment I (60.1 ± 13.0 vs. 57.4 ± 10.9% maximal stimulation output, p = 0.017) and the difference disappeared in experiment II (p = 0.816). In 1-mV motor evoked potential (MEP) measurement, operator B exhibited higher standard deviation indicating lower consistency in experiment I compared with experiment II (1.05 ± 0.40 vs. 1.05 ± 0.16 mV with unequal variances, p = 0.001) and had poor intrarater reliability between the experiments (intraclass correlation coefficient = −0.130). There was no difference in the results of active motor threshold, silent period, paired-pulse stimulation, or continuous theta burst stimulation between the operators.

Conclusions

An operator’s experience in TMS may affect the results of RMT measurement. With practice, a beginner may choose a more precise stimulation location and have higher consistency in 1-mV MEP measurement.

Significance

We recommend that a beginner needs to practice for precise stimulation locations before conducting a trial or clinical practice.

One century of healing currents into the brain from the scalp: From electroconvulsive therapy to repetitive transcranial magnetic stimulation for neuropsychiatric disorders

Electroconvulsive therapy (ECT) was applied for the first time in humans in 1938: after 80 years, it remains conceptually similar today except for modifications of the original protocol aimed to reduce adverse effects (as persistent memory deficits) without losing clinical efficacy. We illustrate the stages of development as well as ups and downs of ECT use in the last eighty years, and the impact that it still maintains for treatment of certain psychiatric conditions. Targeted, individualized and safe noninvasive neuromodulatory interventions are now possible for many neuropsychiatric disorders thanks to repetitive transcranial magnetic stimulation (rTMS) that injects currents in the brain through electromagnetic induction, powerful enough to depolarize cortical neurons and related networks. Although ECT and rTMS differ in basic concepts, mechanisms, tolerability, side effects and acceptability, and beyond their conceptual remoteness (ECT) or proximity (rTMS) to "precision medicine" approaches, the two brain stimulation techniques may be considered as complementary rather than competing in the current treatment of certain neuropsychiatric disorders.

The effect of intermittent theta burst stimulation on corticomotor excitability of the biceps brachii in nonimpaired individuals

Intermittent theta burst stimulation (iTBS) is a form of repetitive transcranial magnetic stimulation (TMS) that can increase corticomotor excitability in distal upper limb muscles, but the effect on the more proximal biceps is unknown. The study objective was to determine the effect of iTBS on corticomotor excitability of the biceps brachii in non-impaired individuals. Ten individuals completed three sessions, and an additional ten individuals completed one session in a secondary study; each session included sham and active iTBS. Resting and active motor thresholds (RMT, AMT) were determined prior to sham and active iTBS. Motor evoked potentials (MEPs) in response to single pulse TMS served as our measure of corticomotor excitability. In our primary cohort, MEPs were recorded with biphasic stimulation to accurately capture the same neurons affected by biphasic iTBS. MEPs were recorded at an intensity of 120% of RMT, or for instances of high RMTs, 100% of the maximum stimulator output (MSO), at baseline, and 10, 20, and 30 minutes after iTBS. MEPs were normalized by the maximum voluntary isometric muscle activity. In the secondary, MEPs were recorded with monophasic stimulation, which increased our ability to record MEPs at 120% of RMT. Linear mixed effects models were used to determine the effect of iTBS on normalized MEPs (nMEPs), with analyses to evaluate the interaction of the biceps AMT:RMT ratio as a measure of corticomotor conductance. Change in nMEPs from baseline did not differ for the active and sham conditions (p = 0.915 ) when MEPs were assessed with biphasic stimulation. With MEPs assessed by monophasic stimulation, there was an increase in biceps nMEPs after active iTBS, and no change in nMEPs after sham. Our results suggest that when RMTs are expected to be high when measured with biphasic stimulation, monophasic stimulation can better capture changes in MEPs induced by iTBS, and biphasic stimulation appears limited in its ability to capture changes in biceps MEPs in nonimpaired individuals. In both cohorts, increased corticomotor excitability after iTBS occurred when the biceps AMT:RMT ratio was high. Thus, the AMT:RMT ratio may be a predictive measure to evaluate the potential for iTBS to increase biceps corticomotor excitability.

Test-Retest Reliability of Short-Interval Intracortical Inhibition Assessed by Threshold-Tracking and Automated Conventional Techniques

Two novel short-interval intracortical inhibition (SICI) protocols, assessing SICI across a range of interstimulus intervals (ISIs) using either parallel threshold-tracking transcranial magnetic stimulation (TT-TMS) or automated conventional TMS (cTMS), were recently introduced. However, the test-retest reliability of these protocols has not been investigated, which is important if they are to be introduced in the clinic. SICI was recorded in 18 healthy subjects using TT-TMS (T-SICI) and cTMS (A-SICI). All subjects were examined at four identical sessions, i.e., morning and afternoon sessions on 2 d, 5-7 d apart. Both SICI protocols were performed twice at each session by the same observer. In one of the sessions, another observer performed additional examinations. Neither intraobserver nor interobserver measures of SICI differed significantly between examinations, except for T-SICI at ISI 3 ms (p = 0.00035) and A-SICI at ISI 2.5 ms (p = 0.0103). Intraday reliability was poor-to-good for A-SICI and moderate-to-good for T-SICI. Interday and interobserver reliabilities of T-SICI and A-SICI were moderate-to-good. Although between-subject variation constituted most of the total variation, SICI repeatability in an individual subject was poor. The two SICI protocols showed no considerable systematic bias across sessions and had a comparable test-retest reliability profile. Findings from the present study suggest that both SICI protocols may be reliably and reproducibly employed in research studies, but should be used with caution for individual decision-making in clinical settings. Studies exploring reliability in patient cohorts are warranted to investigate the clinical utility of these two SICI protocols.

Effect of stimulus orientation and intensity on short-interval intracortical inhibition (SICI) and facilitation (SICF): A multi-channel transcranial magnetic stimulation study

Besides stimulus intensities and interstimulus intervals (ISI), the electric field (E-field) orientation is known to affect both short-interval intracortical inhibition (SICI) and facilitation (SICF) in paired-pulse transcranial magnetic stimulation (TMS). However, it has yet to be established how distinct orientations of the conditioning (CS) and test stimuli (TS) affect the SICI and SICF generation. With the use of a multi-channel TMS transducer that provides electronic control of the stimulus orientation and intensity, we aimed to investigate how changes in the CS and TS orientation affect the strength of SICI and SICF. We hypothesized that the CS orientation would play a major role for SICF than for SICI, whereas the CS intensity would be more critical for SICI than for SICF. In eight healthy subjects, we tested two ISIs (1.5 and 2.7 ms), two CS and TS orientations (anteromedial (AM) and posteromedial (PM)), and four CS intensities (50, 70, 90, and 110% of the resting motor threshold (RMT)). The TS intensity was fixed at 110% RMT. The intensities were adjusted to the corresponding RMT in the AM and PM orientations. SICI and SICF were observed in all tested CS and TS orientations. SICI depended on the CS intensity in a U-shaped manner in any combination of the CS and TS orientations. With 70% and 90% RMT CS intensities, stronger PM-oriented CS induced stronger inhibition than weaker AM-oriented CS. Similar SICF was observed for any CS orientation. Neither SICI nor SICF depended on the TS orientation. We demonstrated that SICI and SICF could be elicited by the CS perpendicular to the TS, which indicates that these stimuli affected either overlapping or strongly connected neuronal populations. We concluded that SICI is primarily sensitive to the CS intensity and that CS intensity adjustment resulted in similar SICF for different CS orientations.

A Case Report: Effect of Robotic Exoskeleton Based Therapy on Neurological and Functional Recovery of a Patient With Chronic Stroke

Background: In this study, a novel electromechanical robotic exoskeleton was developed for the rehabilitation of distal joints. The objective was to explore the functional MRI and the neurophysiological changes in cortical-excitability in response to exoskeleton training for a 9-year chronic stroke patient. Case-Report: The study involved a 52-year old female patient with a 9-year chronic stroke of the right hemisphere, who underwent 20 therapy sessions of 45 min each. Cortical-excitability and clinical-scales: Fugl-Mayer (FM), Modified Ashworth Scale (MAS), Brunnstrom-Stage (BS), Barthel-Index (BI), Range of Motion (ROM), were assessed pre-and post-therapy to quantitatively assess the motor recovery. Clinical Rehabilitation Impact: Increase in FM wrist/hand by 6, BI by 10, and decrease in MAS by 1 were reported. Ipsilesional Motor Evoked Potential (MEP) (obtained using Transcranial Magnetic Stimulation) was increased by 98 μV with a decrease in RMT by 6% and contralesional MEP was increased by 43 μV with a decrease in RMT by 4%. Laterality Index of Sensorimotor Cortex (SMC) reduced in precentral- gyrus (from 0.152 to -0.707) and in postcentral-gyrus (from 0.203 to -0.632). Conclusion: The novel exoskeleton-based training showed improved motor outcomes, cortical excitability, and neuronal activation. The research encourages the further investigation of the potential of exoskeleton training.

Altered Motor Excitability in Patients With Diffuse Gliomas Involving Motor Eloquent Areas: The Impact of Tumor Grading

BACKGROUND

Diffuse gliomas have an increased biological aggressiveness across the World Health Organization (WHO) grading system. The implications of glioma grading on the primary motor cortex (M1)-corticospinal tract (CST) excitability is unknown.

OBJECTIVE

To assess the excitability of the motor pathway with navigated transcranial magnetic stimulation (nTMS).

METHODS

Retrospective cohort study of patients admitted for surgery with diffuse gliomas within motor eloquent areas. Demographic, clinical, and nTMS-related variables were collected. The Cortical Excitability Score (CES 0 to 2 according to the number of abnormal interhemispheric resting motor threshold (RMT) ratios) was calculated for patients where bilateral upper and lower limb mapping was performed.

RESULTS

A total of 45 patients were included: 9 patients had a low-grade glioma and 36 patients had a high-grade glioma. The unadjusted analysis revealed an increase in the latency of the motor evoked potential of the lower limb with an increase of the WHO grade (P = .038). The adjusted analysis confirmed this finding (P = .013) and showed a relation between the increase in the WHO and a decreased RMT (P = .037) of the motor evoked responses in the lower limb. When CES was calculated, an increase in the score was related with an increase in the WHO grade (unadjusted analysis-P = .0001; adjusted analysis-P = .001) and in isocitrate dehydrogenase (IDH) wild-type tumors (unadjusted analysis-P = .020).

CONCLUSION

An increase in the WHO grading system and IDH wild-type tumors are associated with an abnormal excitability of the motor eloquent areas in patients with diffuse gliomas.

Spatiotemporal Dynamics of Single and Paired Pulse TMS-EEG Responses

For physiological brain function a particular balance between excitation and inhibition is essential. Paired pulse transcranial magnetic stimulation (TMS) can estimate cortical excitability and the relative contribution of inhibitory and excitatory networks. Combining TMS with electroencephalography (EEG) enables additional assessment of the spatiotemporal dynamics of neuronal responses in the stimulated brain. This study aims to evaluate the spatiotemporal dynamics and stability of single and paired pulse TMS-EEG responses, and assess long intracortical inhibition (LICI) at the cortical level. Twenty-five healthy subjects were studied twice, approximately one week apart. Manual coil positioning was applied in sixteen subjects and robot-guided positioning in nine. Both motor cortices were stimulated with 50 single pulses and 50 paired pulses at each of the five interstimulus intervals (ISIs): 100, 150, 200, 250 and 300 ms. To assess stability and LICI, the intraclass correlation coefficient and cluster-based permutation analysis were used. We found great resemblance in the topographical distribution of the characteristic TMS-EEG components for single and paired pulse TMS. Stimulation of the dominant and non-dominant hemisphere resulted in a mirrored spatiotemporal dynamics. No significant effect on the TMS-EEG responses was found for either stimulated hemisphere, time or coil positioning method, indicating the stability of both single and paired pulse TMS-EEG responses. For all ISIs, LICI was characterized by significant suppression of the late N100 and P180 components in the central areas, without affecting the early P30, N45 and P60 components. These observations in healthy subjects can serve as reference values for future neuropsychiatric and pharmacological studies.

Toward the establishment of neurophysiological indicators for neuropsychiatric disorders using transcranial magnetic stimulation-evoked potentials: A systematic review

Transcranial magnetic stimulation (TMS) can depolarize the neurons directly under the coil when applied to the cerebral cortex, and modulate the neural circuit associated with the stimulation site, which makes it possible to measure the neurophysiological index to evaluate excitability and inhibitory functions. Concurrent TMS and electroencephalography (TMS-EEG) has been developed to assess the neurophysiological characteristics of cortical regions other than the motor cortical region noninvasively. The aim of this review is to comprehensively discuss TMS-EEG research in the healthy brain focused on excitability, inhibition, and plasticity following neuromodulatory TMS paradigms from a neurophysiological perspective. A search was conducted in PubMed to identify articles that examined humans and that were written in English and published by September 2018. The search terms were as follows: (TMS OR 'transcranial magnetic stimulation') AND (EEG OR electroencephalog*) NOT (rTMS OR 'repetitive transcranial magnetic stimulation' OR TBS OR 'theta burst stimulation') AND (healthy). The study presents an overview of TMS-EEG methodology and neurophysiological indices and reviews previous findings from TMS-EEG in healthy individuals. Furthermore, this review discusses the potential application of TMS-EEG neurophysiology in the clinical setting to study healthy and diseased brain conditions in the future. Combined TMS-EEG is a powerful tool to probe and map neural circuits in the human brain noninvasively and represents a promising approach for determining the underlying pathophysiology of neuropsychiatric disorders.

Effect of different pulse numbers of transcranial magnetic stimulation on motor cortex excitability: Single-blind, randomized cross-over design

AIMS

We aimed to investigate the effect of different pulse numbers of high-frequency repetitive transcranial magnetic stimulation (rTMS) over the motor cortex on cortical excitability in healthy participants.

METHODS

Fifteen healthy participants received 600 and 1200 pulses of 5-Hz rTMS on separate days in a random order. Stimulation (duration, 2 seconds and interval, 1 seconds) was delivered over the left primary motor cortex for the hand, at 90% of resting motor threshold (rMT). The rMT and motor evoked potential (MEP) were measured before stimulation, and at 0 and 30 minutes after rTMS.

RESULTS

No significant differences were observed between the two conditions for MEP (P = .919) or rMT (P = .266). Compared with baseline, MEP was increased significantly at 0 (P < .001) and 30 minutes (P < .001) after stimulation. After stimulation, rMT was decreased at 0 minute for the 600 and 1200 pulse conditions (P < .001), but had recovered by 30 minutes (P = .073).

CONCLUSION

Subthreshold 5-Hz rTMS increased motor cortex excitability in healthy humans. However, the number of pulses may exhibit a ceiling effect in that beyond a certain point, that is, increasing the number of pulses may exhibit no further increase in cortical excitability.

Effect of electro-acupuncture on lateralization of the human swallowing motor cortex excitability in healthy subjects: study protocol for a single-blind, randomized controlled trial

BACKGROUND

Numerous randomized controlled trials on the effects of electro-acupuncture have been conducted to treat dysphagia as a sequela of stroke. However, the normal physiological mechanisms of swallowing and the pathological mechanisms of dysphagia are not fully understood. The purpose of this study is to investigate whether lateralization of the human swallowing motor cortex excitability in healthy subjects will be influenced by electro-acupuncture to Lianquan (CV 23) and Fengfu (GV 16), which may provide insight into the pathological mechanisms of dysphagia after stroke.

METHODS

We designed a single-blind, randomized, sham-controlled trial in which 40 healthy subjects will be recruited. Subjects will be randomized 1:1 into two groups: the electro-acupuncture group and the sham-control electro-acupuncture group. The swallowing motor cortex will be located in both groups using a neuroimaging navigation system. Then left and right cortical stimulation will be measured by transcranial magnetic stimulation (TMS) before and after electro-acupuncture or sham electro-acupuncture. The electro-acupuncture or sham electro-acupuncture interventions will last for 15 min. The primary outcome measure will be percent change in the resting motor threshold (RMT) of the mylohyoid. The secondary outcome measures will be the amplitude (μV) and latency (ms) of the motor evoked potential (MEP) of the mylohyoid as a proxy for the TMS evoked potential. All outcomes will be measured at baseline and after the electro-acupuncture or sham electro-acupuncture treatment.

DISCUSSION

The aim of this trial is to explore whether lateralization of the human swallowing motor cortex excitability in healthy subjects is present, and to determine if electro-acupuncture to acupuncture points Lianquan (CV 23) and Fengfu (GV 16) will exert an effect on it under normal physiological conditions.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR-IOR-17011359 . Registered on 11 May 2017.