Posts Tagged MEP

[Abstract] Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials

Background. After stroke, recovery of movement in proximal and distal upper extremity (UE) muscles appears to follow different time courses, suggesting differences in their neural substrates.

Objective. We sought to determine if presence or absence of motor evoked potentials (MEPs) differentially influences recovery of volitional contraction and strength in an arm muscle versus an intrinsic hand muscle. We also related MEP status to recovery of proximal and distal interjoint coordination and movement fractionation, as measured by the Fugl-Meyer Assessment (FMA).

Methods. In 45 subjects in the year following ischemic stroke, we tracked the relationship between corticospinal tract (CST) integrity and behavioral recovery in the biceps (BIC) and first dorsal interosseous (FDI) muscle. We used transcranial magnetic stimulation to probe CST integrity, indicated by MEPs, in BIC and FDI. We used electromyography, dynamometry, and UE FMA subscores to assess muscle-specific contraction, strength, and inter-joint coordination, respectively.

Results. Presence of MEPs resulted in higher likelihood of muscle contraction, greater strength, and higher FMA scores. Without MEPs, BICs could more often volitionally contract, were less weak, and had steeper strength recovery curves than FDIs; in contrast, FMA recovery curves plateaued below normal levels for both the arm and hand.

Conclusions. There are shared and separate substrates for paretic UE recovery. CST integrity is necessary for interjoint coordination in both segments and for overall recovery. In its absence, alternative pathways may assist recovery of volitional contraction and strength, particularly in BIC. These findings suggest that more targeted approaches might be needed to optimize UE recovery.


via Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials – Heidi M. Schambra, Jing Xu, Meret Branscheidt, Martin Lindquist, Jasim Uddin, Levke Steiner, Benjamin Hertler, Nathan Kim, Jessica Berard, Michelle D. Harran, Juan C. Cortes, Tomoko Kitago, Andreas Luft, John W. Krakauer, Pablo A. Celnik, 2019

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[Abstract] Long-lasting effects of transcranial static magnetic field stimulation on motor cortex excitability



Transcranial static magnetic field stimulation (tSMS) was recently added to the family of inhibitory non-invasive brain stimulation techniques. However, the application of tSMS for 10–20 min over the motor cortex (M1) induces only short-lasting effects that revert within few minutes.


We examined whether increasing the duration of tSMS to 30 min leads to long-lasting changes in cortical excitability, which is critical for translating tSMS toward clinical applications.


The study comprised 5 experiments in 45 healthy subjects. We assessed the impact of 30-min-tSMS over M1 on corticospinal excitability, as measured by the amplitude of motor evoked potentials (MEPs) and resting motor thresholds (RMTs) to single-pulse transcranial magnetic stimulation (TMS) (experiments 1–2). We then assessed the impact of 30-min-tSMS on intracortical excitability, as measured by short-interval intracortical facilitation (SICF) and short-interval intracortical inhibition (SICI) using paired-pulse TMS protocols (experiments 2–4). We finally assessed the impact of 10-min-tSMS on SICF and SICI.


30-min-tSMS decreased MEP amplitude compared to sham for at least 30 min after the end of the stimulation. This long-lasting effect was associated with increased SICF and reduced SICI. 10-min-tSMS –previously reported to induce a short-lasting decrease in MEP amplitude– produced the opposite changes in intracortical excitability, decreasing SICF while increasing SICI.


These results suggest a dissociation of intracortical changes in the consolidation from short-lasting to long-lasting decrease of corticospinal excitability induced by tSMS. The long-lasting effects of 30-min-tSMS open the way to the translation of this simple, portable and low-cost technique toward clinical trials.

via Long-lasting effects of transcranial static magnetic field stimulation on motor cortex excitability – Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation

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[Abstract] Efficacy of modified constraint-induced movement therapy in acute stroke

BACKGROUND: Modified constraint induced movement therapy (m-CIMT) discourages the use of the unaffected extremity and encourages the active use of the hemiplegic arm in order to restore the motor function. AIM: The aim was to assess the efficacy of m-CIMT on functional recovery of upper extremity (UE) in acute stroke patients, as compared to conventional rehabilitation therapy.

DESIGN: This is a prospective comparative study.

SETTING: This study included sixty patients with acute stroke recruited from neurology department.

METHODS: This study included sixty acute stroke patients. Inclusion criteria were: patients within two weeks from the onset of stroke, persistent hemiparesis leading to impaired upper extremity function, evidence of preserved cognitive function, and a minimum of 10 degrees of active finger extension and 20 degrees of active wrist extension. Exclusion criteria were: intra-cerebral hemorrhage, previous stroke on the same side, presence of neglect or a degree of aphasia impeding understanding of instructions, and conditions that limit the use of the upper limb before the stroke. Patients were assessed by Fugl-Meyer motor assessment (FMA), action research arm test (ARAT) and motor evoked potentials (MEPs), recorded from the abductor pollicis brevis (APB) of the affected hand. The clinical and neurophysiological tests were performed pre and postrehabilitation. The patients were divided into two groups: conventional rehabilitation program group (CRP) included 30 patients who were given a conventional rehabilitation program for two weeks. CIMT group included 30 patients who were subjected to modified CIMT for two consecutive weeks. Total treatment time was the same in both groups.

RESULTS: CRP group showed a non-significant improvement in FMA and ARAT. CIMT group showed a significant improvement in clinical scores on all tests (p < 0.05). When comparing both groups using FMA and ARAT tests pre- and post- therapy, a significant difference (p < 0.05) was found between both groups with CIMT group showing greater improvement. When comparing MEPs in CRP group, pre and postrehabilitation, a non-significant improvement was found for resting motor threshold (RMT), central motor conduction time (CMCT) and amplitude of MEPs. In contrast, each of the MEP parameters exhibited a significant improvement in CIMT group (p < 0.05).

CONCLUSION: In contrast to conventional rehabilitation therapy, modified CIMT revealed a significant functional and MEP improvement in acute stroke patients indicating that m-CIMT might be a more efficient treatment strategy.

CLINICAL REHABILITATION IMPACT: It is advised to use modified constraint movement therapy in rehabilitation of cerebrovascular stroke during acute stage.

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[Poster] Navigated Transcranial Magnetic Stimulation: A Biologically-Based Assay of Lower Extremity Impairment and Gait Velocity? – Archives of Physical Medicine and Rehabilitation

Source: Navigated Transcranial Magnetic Stimulation: A Biologically-Based Assay of Lower Extremity Impairment and Gait Velocity? – Archives of Physical Medicine and Rehabilitation

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[ARTICLE] Comparing the Effects of Functional Electrical Stimulation Versus Somatosensory Stimulation on Increasing Corticospinal Excitability for a Muscle of the Hand – Full Text PDF


The electrically-evoked afferent volley generated during NeuroMuscular Electrical Stimulation (NMES) can increase the excitability of CorticoSpinal (CS) pathways. Over time, NMES can strengthen damaged CS pathways and result in enduring improvements in function for persons with central nervous system injury or disease. NMES-induced increases in CS excitability have been studied using a variety of NMES parameters, yet the influence of these stimulation parameters on increasing CS excitability is not well understood.

NMES is commonly delivered at intensities sufficient to generate repeated functional contractions for relatively short durations (30-40 min) or at low intensities, near motor threshold, for long durations (2 h).

For the purpose of this study, these different stimulation protocols are termed Functional Electrical Stimulation (FES) and Somatosensory Stimulation (SS), respectively. A direct comparison of increases in CS excitability induced by such protocols has not been conducted. Thus, the present experiments were designed to compare changes in CS excitability for Abductor Pollicis Brevis (APB) in the hand following FES and SS of the median nerve.

We hypothesized that due to the generation of a larger afferent volley, the FES would increase CS excitability more than the SS. Ten Motor Evoked Potentials (MEPs) were evoked in APB using transcranial magnetic stimulation before and after each type of NMES. MEP amplitude increased significantly following both the FES (by 66 ± 7%, mean ± standard error) and SS (49 ± 6%), but the amplitude of these increases was not significantly different.

These results suggest that just 40 min of FES can increase CS excitability, and potentially provide rehabilitative benefits, to the same extent as 2 h of SS.

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[ARTICLE] An investigation of cortical neuroplasticity following stroke in adults: is there evidence for a critical window for rehabilitation? – Full Text HTML



Evidence in animal stroke models suggests that neuroplasticity takes place maximally in a specific time window after an ischaemic lesion, which may coincide with the optimal time to intervene with rehabilitation. The aim of this study is to investigate neurophysiological evidence for a “critical window” of enhanced neuroplasticity in patients following ischaemic stroke, and establish its duration. We will also investigate changes in cortical inhibition following stroke, and the influence this has on functional recovery.


We will recruit participants recently admitted to the Stroke Unit of major metropolitan hospitals who have had a stroke and can provide informed consent. Participants will be excluded if they have any contraindications to Transcranial Magnetic Stimulation. We will compare neurophysiological outcomes in an age-matched healthy control group. We conservatively hypothesise a 5 % increase in neuroplasticity at the optimal timing following stroke, compared to control participants, and require 43 patients following stroke to detect a significant difference with 80 % power. The primary outcome is the change in the motor evoked potential (MEP) amplitude in a hand muscle, after the administration of a plasticity-inducing paradigm to the affected hemisphere. Secondary outcomes include measures of cortical excitability, intracortical inhibition and arm function.


The data from this trial will clarify whether there is a critical window for neuroplastic change in the brain following stroke. If so, intensive rehabilitation during this period could be more effective, reducing long-term disability and the cost burden of stroke.

Continue —> BMC Neurology | Full text | An investigation of cortical neuroplasticity following stroke in adults: is there evidence for a critical window for rehabilitation?.

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[WEB SITE] Factors Associated With Upper Extremity Motor Recovery After Repetitive Transcranial Magnetic Stimulation in Stroke Patients – Full Text HTML



To determine factors associated with motor recovery of the upper extremity after repetitive transcranial magnetic stimulation (rTMS) treatment in stroke patients.


Twenty-nine patients with subacute stroke participated in this study. rTMS was applied to the hand motor cortex for 10 minutes at a 110% resting motor threshold and 10 Hz frequency for two weeks. We evaluated the biographical, neurological, clinical, and functional variables, in addition to the motor-evoked potential (MEP) response. The Manual Function Test (MFT) was performed before, immediately after, and two weeks after, the treatment. Patients were divided into a responder and non-responder group according to their respective improvements on the MFT. Data were compared between the two groups.


Patients with exclusively subcortical stroke, absence of aphasia, the presence of a MEP response, high scores on the Mini-Mental Status Examination, Motricity Index arm score, Functional Independence Measure, and Functional Ambulatory Classification; and a shorter period from stroke onset to rTMS were found to be significantly associated with a response to rTMS.


The results of this study suggest that rTMS may have a greater effect on upper extremity motor recovery in stroke patients who have a MEP response, suffer an exclusively subcortical stroke, mild paresis, and have good functional status. Applying rTMS early would have additional positive effects in the patients with the identified characteristics.

Continue —> KoreaMed Synapse.

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[ARTICLE] Effect of Repetitive Transcranial Magnetic Stimulation on Cortico Motor-Excitability Motor Function of the affected Hand in Subjects with Stroke


Objectives: To Test the hypothesis that 10 days of high frequency (10HZ) repetitive transcranial magnetic stimulation (rTMS) with hand therapy elicit more improvement on motor recovery and motor function in the paretic hand than sham stimulation in patients with stroke and to examine the correlation between corticomotor excitability and motor function of the hand in stroke subjects at various time points of recovery.

Method: Forty normal control subjects were recruited to record MEP variables of APB muscle of both sides and compare it with 60 acute stroke subjects.60 stroke subjects were randomly assigned to one of the two treatment methods. The rTMS group received high frequency (10Hz) rTMS to the affected hemisphere plus hand therapy for the hemi paretic hand and in sham rTMS group, patients received sham stimulation to the affected hemisphere and hand therapy to the hemi paretic hand. Corticomotor excitability was assessed by the central motor conduction time(CMCT) and motor threshold at baseline, after 5 days and 10 days following intervention. Motor function of the hand was assessed by the Jebsen hand function test(JHFT) at baseline, after 5 days and 10 days of intervention.

Results: Normative values of APB was analyzed with ROC curve and compared with stroke subjects.. Patients with rTMS group receiving 10 Hz rTMS plus hand therapy lead to a greater improvement in corticomotor excitability. Corticomotor excitability decreased and motor function of the hand improved following intervention (P=0.001). There was a significant correlation between the Corticomotor excitability and motor function of the hand in the affected hemisphere at various time points of recovery.

Conculsions: Focal stimulation of high frequency (10 Hz) rTMS to the affected motor cortex and 30 min of motor training twice a day for 10 consecutive days would enhance the Corticomotor excitability and improved motor function of the affected hand in stroke subjects.

via Indian Journals.

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[ARTICLE] Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans – Full Text HTML


Transcranial direct current stimulation (tDCS) of the human motor cortex at an intensity of 1 mA with an electrode size of 35 cm2 has been shown to induce shifts of cortical excitability during and after stimulation. These shifts are polarity-specific with cathodal tDCS resulting in a decrease and anodal stimulation in an increase of cortical excitability. In clinical and cognitive studies, stronger stimulation intensities are used frequently, but their physiological effects on cortical excitability have not yet been explored.

Therefore, here we aimed to explore the effects of 2 mA tDCS on cortical excitability. We applied 2 mA anodal or cathodal tDCS for 20 min on the left primary motor cortex of 14 healthy subjects. Cathodal tDCS at 1 mA and sham tDCS for 20 min was administered as control session in nine and eight healthy subjects, respectively. Motor cortical excitability was monitored by transcranial magnetic stimulation (TMS)-elicited motor-evoked potentials (MEPs) from the right first dorsal interosseous muscle. Global corticospinal excitability was explored via single TMS pulse-elicited MEP amplitudes, and motor thresholds. Intracortical effects of stimulation were obtained by cortical silent period (CSP), short latency intracortical inhibition (SICI) and facilitation (ICF), and I wave facilitation. The above-mentioned protocols were recorded both before and immediately after tDCS in randomized order.

Additionally, single-pulse MEPs, motor thresholds, SICI and ICF were recorded every 30 min up to 2 h after stimulation end, evening of the same day, next morning, next noon and next evening. Anodal as well as cathodal tDCS at 2 mA resulted in a significant increase of MEP amplitudes, whereas 1 mA cathodal tDCS decreased corticospinal excitability. A significant shift of SICI and ICF towards excitability enhancement after both 2 mA cathodal and anodal tDCS was observed. At 1 mA, cathodal tDCS reduced single-pulse TMS-elicited MEP amplitudes and shifted SICI and ICF towards inhibition. No significant changes were observed in the other protocols. Sham tDCS did not induce significant MEP alterations.

These results suggest that an enhancement of tDCS intensity does not necessarily increase efficacy of stimulation, but might also shift the direction of excitability alterations. This should be taken into account for applications of the stimulation technique using different intensities and durations in order to achieve stronger or longer lasting after-effects.

Full Text HTML –>  Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans.

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[ARTICLE] Safety and Feasibility of Transcranial Direct Current Stimulation in Pediatric Hemiparesis: A Randomized Controlled Pilot Study


Background: Transcranial Direct Current Stimulation (tDCS) is a form of non-invasive brain stimulation with improved adult stroke outcomes. Applying tDCS in children with congenital Transcranial Direct Current Stimulation has not yet been explored.

Objective/Design: Primary objective was to explore the safety and feasibility of single-session tDCS through an adverse events profile and symptom assessment within a double-blind, randomized placebo-controlled pilot study in children with congenital hemiparesis. A secondary objective assessed stability of hand and cognitive function.

Participants: Thirteen children, ages 7-18 years, with congenital hemiparesis.

Intervention: Random assignment to a tDCS intervention or tDCScontrol group, with safety and functional assessments on pretest, posttest on the same day and a one-week follow up session. An intervention of 10 minutes of 0.7 mA tDCS was applied to bilateral primary motor cortices. The tDCS intervention was considered safe, if there was no individual decline of 25% or group decline of 2 standard deviations (2 SD) for motor evoked potentials (MEPs), behavioral data, and report of adverse events.

Results: No major adverse events were found, including seizure. Two participants did not complete the study due to lack of MEP and discomfort. For the remaining 11 completed participants, group differences in MEPs and behavioral data did not exceed 2 SD.

Study completed without need for stopping per medical monitor and biostatisticial analysis.

Limitations: Small sample size with data available for 11 participants.

Conclusions: Based on our study, tDCS appears to be safe and feasible and well tolerated in most children with hemiparesis. Future investigation of serial sessions of tDCS in conjunction with rehabilitation in pediatric hemiparesis are indicated to explore the benefit of a synergistic approach to improving hand function.

via Safety and Feasibility of Transcranial Direct Current Stimulation in Pediatric Hemiparesis: A Randomized Controlled Pilot Study.

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