Neurostimulation After Stroke

Neural stimulation technology aids stroke survivors in regaining lost motor functions. This article explores its applications in upper and lower limb stroke rehabilitation. The authors review various methods to target the corticomotor system, including transcranial direct current stimulation, repetitive transcranial magnetic stimulation, and vagus nerve stimulation. In addition, the authors review the use of peripheral neuromuscular electrical stimulation for therapeutic and assistive purposes, including transcutaneous electrical nerve stimulation, neuromuscular electrical stimulation, and functional electrical stimulation. For each, the authors examine the potential benefits, limitations, safety considerations, and FDA status.

Evaluation of Contralateral Limb Cross Education and High-Frequency Repetitive Transcranial Magnetic Stimulation on Functional Indices of the Affected Upper Limb in Subacute Phase of Stroke

Background

Stroke is one of the causes of long-term morbidity. Despite rehabilitation strategies, most survivors live with motor deficits in the upper limbs.

Objectives

The aim of the study was to compare the effect of contralateral cross education (CE) and high-frequency repetitive magnetic stimulation (HF-rTMS) on the function of upper extremity in subacute phase of stroke.

Methods

Forty patients were randomly assigned into 4 groups. Group "A" received physical therapy (PT) for 10 sessions, 3 times per week. Group "B" received PT and HF-rTMS as follows: stimulation of 20 Hz for 5 s, intertrain interval for 50 s, 20 trains, 2000 pulses at 90% resting motor threshold, and conventional PT. Group "C" was treated with CE and PT. In group "D," HF-rTMS, CE, and PT were administered.

Results

Significant differences were found in the Fugl-Meyer scale between "A" and "C" (P = 0.01), "A" and "D" (P = 0.02), and "B" and "C" groups (P = 0.01). In the box-block test, there were significant differences between "A" and "B" (P = 0.01), "A" and "C" (P < 0.001), "B" and "D" (P = 0.001), and "B" and "C" groups (P = 0.01). Statistical differences were observed in grip strength between "A" and "B" (P = 0.01) and "A" and "C" groups (P = 0.02).

Conclusions

It is suggested that clinicians select the therapeutic methods in line with their expected goal. When the goal is to improve upper extremity function, CE+PT could be more effective than HF-rTMS+PT. Also, CE+PT and HF-rTMS+PT were more effective than CE+HF-rTMS+PT at improving grip strength. Therefore, combining several methods would not always lead to better results.

Applications of Repetitive Transcranial Magnetic Stimulation to Improve Upper Limb Motor Performance After Stroke: A Systematic Review

BACKGROUND

Noninvasive brain stimulation (NIBS) is a promising technique for improving upper limb motor performance post-stroke. Its application has been guided by the interhemispheric competition model and typically involves suppression of contralesional motor cortex. However, the bimodal balance recovery model prompts a more tailored application of NIBS based on ipsilesional corticomotor function.

OBJECTIVE

To review and assess the application of repetitive transcranial magnetic stimulation (rTMS) protocols that aimed to improve upper limb motor performance after stroke.

METHODS

A PubMed search was conducted for studies published between 1st January 2005 and 1st November 2022 using rTMS to improve upper limb motor performance of human adults after stroke. Studies were grouped according to whether facilitatory or suppressive rTMS was applied to the contralesional hemisphere.

RESULTS

Of the 492 studies identified, 70 were included in this review. Only 2 studies did not conform to the interhemispheric competition model, and facilitated the contralesional hemisphere. Only 21 out of 70 (30%) studies reported motor evoked potential (MEP) status as a biomarker of ipsilesional corticomotor function. Around half of the studies (37/70, 53%) checked whether rTMS had the expected effect by measuring corticomotor excitability (CME) after application.

CONCLUSION

The interhemispheric competition model dominates the application of rTMS post-stroke. The majority of recent and current studies do not consider bimodal balance recovery model for the application of rTMS. Evaluating CME after the application rTMS could confirm that the intervention had the intended neurophysiological effect. Future studies could select patients and apply rTMS protocols based on ipsilesional MEP status.

The Effect of Cerebellar rTMS on Modulating Motor Dysfunction in Neurological Disorders: a Systematic Review

The effectiveness of cerebellar repetitive transcranial magnetic stimulation (rTMS) on motor dysfunction in patients with neurological disorders has received increasing attention because of its potential for neuromodulation. However, studies on the neuromodulatory effects, parameters, and safety of rTMS implementation in the cerebellum to alleviate motor dysfunction are limited. This systematic review aimed to evaluate the effectiveness and safety of cerebellar rTMS treatment for motor dysfunction caused by neurological disorders and to review popular stimulation parameters. Five electronic databases-Medline, Web of Science, Scopus, Cochrane Library, and Embase-were searched for relevant research published from inception to July 2022. All randomized controlled trials (RCTs) that reported the effects of cerebellar rTMS combined with behavioral rating scales on motor dysfunction were eligible for enrollment. Additionally, reference lists of the enrolled studies were manually checked. Among 1156 articles screened, 21 RCTs with 666 subjects were included. rTMS conducted on the cerebellum showed an improvement in stroke (spasticity, balance, and gait), cervical dystonia, Parkinson's disease (tremor), cerebellar ataxia, and essential tremor but not in multiple sclerosis. The 8-shaped coil with a diameter of 70 mm was determined as the most common therapeutic choice. None of the studies reported severe adverse events except mild side effects in three. Therefore, rTMS appears to be a promising and safe technique for the treatment of motor dysfunction, targeting the cerebellum to induce motor behavioral improvement. Further rigorous RCTs, including more samples and longer follow-up periods, are required to precisely explore the effective stimulation parameters and possible mechanisms.

Investigation of the efficacy of low-frequency repetitive transcranial magnetic stimulation on upper-limb motor recovery in subacute ischemic stroke without cortical involvement: a protocol paper for a multi-center, double-blind randomized controlled trial

Introduction

The incidence of stroke is increasing steadily due to factors such as population aging. Approximately 80% of stroke survivors have motor disorders affecting their daily lives. Repetitive transcranial magnetic stimulation (rTMS) has been reported to maximize functional recovery after stroke along with exercise intervention in upper limb rehabilitation treatment. However, whether rTMS affects the recovery of upper limb function in patients with stroke remains unclear. Therefore, in this trial, we will investigate the efficacy of low-frequency rTMS in patients with subcortical and brainstem ischemic stroke.

Methods

This study has been designed as a multi-center, double-blind, randomized controlled trial to compare the efficacy of low-frequency rTMS over the contralesional M1 with sham stimulation. Overall, 88 participants will be allocated to the intervention or control group in a 1:1 ratio, with stratification according to their initial upper extremity Fugl-Meyer assessment (UE-FMA) score. The participants will receive either 30 min of real rTMS (intervention group) or sham rTMS (control group), followed by 30 min of occupational therapy for 10 consecutive workdays. All the participants will receive the same amount of rehabilitation therapy throughout the intervention period. Evaluations will be performed at baseline (T0), at the end of treatment (T1), and 4 weeks after the end of treatment (T2), including the box and block test (BBT), UE-FMA, Korean version of the Modified Barthel Index, and NIH Stroke Scale scores, Finger tapping test, Brunnstrom stage, modified Ashworth scale, and grip strength. The primary outcome will be the change in the BBT score between T0 and T2.

Conclusion

This study will provide evidence on the efficacy of low-frequency rTMS in motor function recovery of the upper limb in patients with subacute, subcortical, and brainstem ischemic stroke.

Clinical trial registration

ClinicalTrials.gov, identifier [NCT05535504].

Repetitive transcranial magnetic stimulation for stroke rehabilitation: insights into the molecular and cellular mechanisms of neuroinflammation

Stroke is a leading cause of mortality and disability worldwide, with most survivors reporting dysfunctions of motor, sensation, deglutition, cognition, emotion, and speech, etc. Repetitive transcranial magnetic stimulation (rTMS), one of noninvasive brain stimulation (NIBS) techniques, is able to modulate neural excitability of brain regions and has been utilized in neurological and psychiatric diseases. Moreover, a large number of studies have shown that the rTMS presents positive effects on function recovery of stroke patients. In this review, we would like to summarized the clinical benefits of rTMS for stroke rehabilitation, including improvements of motor impairment, dysphagia, depression, cognitive function, and central post-stroke pain. In addition, this review will also discuss the molecular and cellular mechanisms underlying rTMS-mediated stroke rehabilitation, especially immune regulatory mechanisms, such as regulation of immune cells and inflammatory cytokines. Moreover, the neuroimaging technique as an important tool in rTMS-mediated stroke rehabilitation has been discussed, to better understanding the mechanisms underlying the effects of rTMS. Finally, the current challenges and future prospects of rTMS-mediated stroke rehabilitation are also elucidated with the intention to accelerate its widespread clinical application.

Hemispheric Differences of 1 Hz rTMS over Motor and Premotor Cortex in Modulation of Neural Processing and Hand Function

INTRODUCTION

Non-invasive brain stimulation can modulate both neural processing and behavioral performance. Its effects may be influenced by the stimulated area and hemisphere. In this study (EC no. 09083), repetitive transcranial magnetic stimulation (rTMS) was applied to the primary motor cortex (M1) or dorsal premotor cortex (dPMC) of either the right or left hemisphere, while evaluating cortical neurophysiology and hand function.

METHODS

Fifteen healthy subjects participated in this placebo-controlled crossover study. Four sessions of real 1 Hz rTMS (110% of rMT, 900 pulses) over (i) left M1, (ii) right M1, (iii) left dPMC, (iv) right dPMC, and one session of (v) placebo 1 Hz rTMS (0% of rMT, 900 pulses) over the left M1 were applied in randomized order. Motor function of both hands (Jebsen-Taylor Hand Function Test (JTHFT)) and neural processing within both hemispheres (motor evoked potentials (MEPs), cortical silent period (CSP), and ipsilateral silent period (ISP)) were evaluated prior and after each intervention session.

RESULTS

A lengthening of CSP and ISP durations within the right hemisphere was induced by 1 Hz rTMS over both areas and hemispheres. No such intervention-induced neurophysiological changes were detected within the left hemisphere. Regarding JTHFT and MEP, no intervention-induced changes ensued. Changes of hand function correlated with neurophysiological changes within both hemispheres, more often for the left than the right hand.

CONCLUSIONS

Effects of 1 Hz rTMS can be better captured by neurophysiological than behavioral measures. Hemispheric differences need to be considered for this intervention.

Optogenetics stimulates nerve reorganization in the contralesional anterolateral primary motor cortex in a mouse model of ischemic stroke

The anterolateral motor cortex of rodents is an important motor auxiliary area, and its function is similar to that of the premotor area in humans. Activation and inhibition of the contralesional anterolateral motor cortex (cALM) have been shown to have direct effects on motor behavior. However, the significance of cALM activation and inhibition in the treatment of stroke remains unclear. This study investigated the role of optogenetic cALM stimulation in a mouse model of cerebral stroke. The results showed that 21-day optogenetic cALM inhibition, but not activation, improved neurological function. In addition, optogenetic cALM stimulation substantially altered dendritic structural reorganization and dendritic spine plasticity, as optogenetic cALM inhibition resulted in increased dendritic length, number of dendritic spines, and number of perforated synapses, whereas optogenetic activation led to an increase in the number of multiple synapse boutons and the number of dendritic intersections. Furthermore, RNA-seq analysis showed that multiple biological processes regulated by the cALM were upregulated immediately after optogenetic cALM inhibition, and that several immediate-early genes (including cFOS, Erg1, and Sema3f) were expressed at higher levels after optogenetic inhibition than after optogenetic activation. These results were confirmed by quantitative reverse transcription-polymerase chain reaction. Finally, immunofluorescence analysis showed that the c-FOS signal in layer V of the primary motor cortex in the ischemic hemisphere was higher after optogenetic cALM activation than it was after optogenetic cALM inhibition. Taken together, these findings suggest that optogenetic cALM stimulation promotes neural reorganization in the primary motor cortex of the ischemic hemisphere, and that optogenetic cALM inhibition and activation have different effects on neural plasticity. The study was approved by the Experimental Animal Ethics Committee of Fudan University (approval No. 201802173S) on March 3, 2018.

Resting motor threshold in the course of hand motor recovery after stroke: a systematic review

Background

Resting motor threshold is an objective measure of cortical excitability. Numerous studies indicate that the success of motor recovery after stroke is significantly determined by the direction and extent of cortical excitability changes. A better understanding of this topic (particularly with regard to the level of motor impairment and the contribution of either cortical hemisphere) may contribute to the development of effective therapeutical strategies in this cohort.

Objectives

This systematic review collects and analyses the available evidence on resting motor threshold and hand motor recovery in stroke patients.

Methods

PubMed was searched from its inception through to 31/10/2020 on studies investigating resting motor threshold of the affected and/or the non-affected hemisphere and motor function of the affected hand in stroke cohorts.

Results

Overall, 92 appropriate studies (including 1978 stroke patients and 377 healthy controls) were identified. The analysis of the data indicates that severe hand impairment is associated with suppressed cortical excitability within both hemispheres and with great between-hemispheric imbalance of cortical excitability. Favorable motor recovery is associated with an increase of ipsilesional motor cortex excitability and reduction of between-hemispheric imbalance. The direction of change of contralesional motor cortex excitability depends on the amount of hand motor impairment. Severely disabled patients show an increase of contralesional motor cortex excitability during motor recovery. In contrast, recovery of moderate to mild hand motor impairment is associated with a decrease of contralesional motor cortex excitability.

Conclusions

This data encourages a differential use of rehabilitation strategies to modulate cortical excitability. Facilitation of the ipsilesional hemisphere may support recovery in general, whereas facilitation and inhibition of the contralesional hemisphere may enhance recovery in severe and less severely impaired patients, respectively.

Brain Functional Changes in Stroke Following Rehabilitation Using Brain-Computer Interface-Assisted Motor Imagery With and Without tDCS: A Pilot Study

Brain-computer interface-assisted motor imagery (MI-BCI) or transcranial direct current stimulation (tDCS) has been proven effective in post-stroke motor function enhancement, yet whether the combination of MI-BCI and tDCS may further benefit the rehabilitation of motor functions remains unknown. This study investigated brain functional activity and connectivity changes after a 2 week MI-BCI and tDCS combined intervention in 19 chronic subcortical stroke patients. Patients were randomized into MI-BCI with tDCS group and MI-BCI only group who underwent 10 sessions of 20 min real or sham tDCS followed by 1 h MI-BCI training with robotic feedback. We derived amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), and functional connectivity (FC) from resting-state functional magnetic resonance imaging (fMRI) data pre- and post-intervention. At baseline, stroke patients had lower ALFF in the ipsilesional somatomotor network (SMN), lower ReHo in the contralesional insula, and higher ALFF/Reho in the bilateral posterior default mode network (DMN) compared to age-matched healthy controls. After the intervention, the MI-BCI only group showed increased ALFF in contralesional SMN and decreased ALFF/Reho in the posterior DMN. In contrast, no post-intervention changes were detected in the MI-BCI + tDCS group. Furthermore, higher increases in ALFF/ReHo/FC measures were related to better motor function recovery (measured by the Fugl-Meyer Assessment scores) in the MI-BCI group while the opposite association was detected in the MI-BCI + tDCS group. Taken together, our findings suggest that brain functional re-normalization and network-specific compensation were found in the MI-BCI only group but not in the MI-BCI + tDCS group although both groups gained significant motor function improvement post-intervention with no group difference. MI-BCI and tDCS may exert differential or even opposing impact on brain functional reorganization during post-stroke motor rehabilitation; therefore, the integration of the two strategies requires further refinement to improve efficacy and effectiveness.

Ipsilateral Motor Pathways and Transcallosal Inhibition During Lower Limb Movement After Stroke

BACKGROUND

Stroke rehabilitation may be improved with a better understanding of the contribution of ipsilateral motor pathways to the paretic limb and alterations in transcallosal inhibition. Few studies have evaluated these factors during dynamic, bilateral lower limb movements, and it is unclear whether they relate to functional outcomes.

OBJECTIVE

Determine if lower limb ipsilateral excitability and transcallosal inhibition after stroke depend on target limb, task, or number of limbs involved, and whether these factors are related to clinical measures.

METHODS

In 29 individuals with stroke, ipsilateral and contralateral responses to transcranial magnetic stimulation were measured in the paretic and nonparetic tibialis anterior during dynamic (unilateral or bilateral ankle dorsiflexion/plantarflexion) and isometric (unilateral dorsiflexion) conditions. Relative ipsilateral excitability and transcallosal inhibition were assessed. Fugl-Meyer, ankle movement accuracy, and walking characteristics were assessed.

RESULTS

Relative ipsilateral excitability was greater during dynamic than isometric conditions in the paretic limb (P ≤ .02) and greater in the paretic than the nonparetic limb during dynamic conditions (P ≤ .004). Transcallosal inhibition was greater in the ipsilesional than contralesional hemisphere (P = .002) and during dynamic than isometric conditions (P = .03). Greater ipsilesional transcallosal inhibition was correlated with better ankle movement accuracy (R² = 0.18, P = .04). Greater contralateral excitability to the nonparetic limb was correlated with improved walking symmetry (R² = 0.19, P = .03).

CONCLUSIONS

Ipsilateral pathways have increased excitability to the paretic limb, particularly during dynamic tasks. Transcallosal inhibition is greater in the ipsilesional than contralesional hemisphere and during dynamic than isometric tasks. Ipsilateral pathways and transcallosal inhibition may influence walking asymmetry and ankle movement accuracy.

Tongxinluo promotes axonal plasticity and functional recovery after stroke

Background

The aim of this study was to investigate the neural plasticity in contralesional cortex and the effects of tongxinluo (TXL) in cerebral ischemic rats.

Methodology

We used stroke-prone renovascular hypertensive (RHRSP) cerebral ischemia rat models to study the effect of TXL and the underlying mechanisms. We performed foot-fault and beam-walking tests to evaluate the motor function of rats after cortical infarction. Biotinylated dextran amine (BDA) was used to track axonal sprouting and neural connections.

Results

TXL enhanced the recovery of motor function in cerebral infarction rats. TXL increased axonal sprouting in the peri-infarcted area but not in the corpus callosum, indicating in situ origination instead of crossing between cortical hemispheres through the corpus callosum. TXL promoted the sprouting of corticospinal axons into the denervated side of spinal gray matter. The synaptophysin (SYN)-positive intensity in the peri-infarcted area of TXL-treated group was greater than that in the vehicle group. We observed co-localization of SYN with BDA-positive fibers in the denervated spinal cord gray matter in the TXL group, suggesting that axonal remodeling and synaptic connections were promoted by TXL.

Conclusion

TXL may promote the recovery of neurological function by promoting the axonal remodeling and synapse formation of motor neuronal fibers after focal cortical infarction in hypertensive rats.

Individualized Responses to Ipsilesional High-Frequency and Contralesional Low-Frequency rTMS in Chronic Stroke: A Pilot Study to Support the Individualization of Neuromodulation for Rehabilitation

Background: In this pilot study, we examined the effects of ipsilesional high-frequency rTMS (iHF-rTMS) and contralesional low-frequency rTMS (cLF-rTMS) applied via a double-cone coil on neurophysiological and gait variables in patients with chronic stroke.

Objective/Hypothesis: To determine the group and individual level effects of two types of stimulation to better individualize neuromodulation for rehabilitation.

Methods: Using a randomized, within-subject, double-blind, sham-controlled trial with 14 chronic stroke participants iHF-rTMS and cLF-rTMS were applied via a double-cone coil to the tibialis anterior cortical representation. Neurophysiological and gait variables were compared pre-post rTMS.

Results: A small effect of cLF-rTMS indicated increased MEP amplitudes (Cohen’s D; cLF-rTMS, d = −0.30). Group-level analysis via RMANOVA showed no significant group effects of stimulation (P > 0.099). However, secondary analyses of individual data showed a high degree of response variability to rTMS. Individual percent changes in resting motor threshold and normalized MEP latency correlated with changes in gait propulsive forces and walking speed (iHF-rTMS, nLAT:Pp, R = 0.632 P = 0.015; cLF-rTMS, rMT:SSWS, R = −0.557, P = 0.039; rMT:Pp, R = 0.718, P = 0.004).

Conclusions: Changes in propulsive forces and walking speed were seen in some individuals that showed neurophysiological changes in response to rTMS. The neurological consequences of stroke are heterogeneous making a “one type fits all” approach to neuromodulation for rehabilitation unlikely. This pilot study suggests that an individual’s unique response to rTMS should be considered before the application/selection of neuromodulatory therapies. Before neuromodulatory therapies can be incorporated into standard clinical practice, additional work is needed to identify biomarkers of response and how best to prescribe neuromodulation for rehabilitation for post-stroke gait.

Promotion of Poststroke Motor-Function Recovery with Repetitive Transcranial Magnetic Stimulation by Regulating the Interhemispheric Imbalance

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive brain-stimulation technique that transiently modulates cerebral cortex excitability, achieving overall positive results in poststroke motor-function recovery. Excessive inhibition of the ipsilesional-affected hemisphere by the contralesional-unaffected hemisphere has seriously hindered poststroke motor-function recovery. Hence, intracortical disinhibition can be used as an approach to managing poststroke brain injury. This technique promotes neural plasticity for faster motor-function recovery. rTMS relieves unilateral inhibition of the brain function by regulatinga interhemispheric-imbalanced inhibition. This paper summarized 12 studies from 2016 to date, focusing on rTMS on motor function after acute and chronic stroke by regulating the interhemispheric imbalance of inhibitory inputs. Although rTMS studies have shown promising outcomes on recovery of motor functions in stroke patients, different intervention methods may lead to discrepancies in results. A uniform optimal stimulus model cannot routinely be used, mainly due to the stimulus schemes, stroke types and outcome-measuring differences among studies. Thus, the effect of rTMS on poststroke motor-function recovery should be investigated further to standardize the rTMS program for optimal poststroke motor-function recovery. More randomized, placebo-controlled clinical trials with standardized rTMS protocols are needed to ensure the effectiveness of the treatment.

Neurostimulation and Reach-to-Grasp Function Recovery Following Acquired Brain Injury: Insight From Pre-clinical Rodent Models and Human Applications

Reach-to-grasp is an evolutionarily conserved motor function that is adversely impacted following stroke and traumatic brain injury (TBI). Non-invasive brain stimulation (NIBS) methods, such as transcranial magnetic stimulation and transcranial direct current stimulation, are promising tools that could enhance functional recovery of reach-to-grasp post-brain injury. Though the rodent literature provides a causal understanding of post-injury recovery mechanisms, it has had a limited impact on NIBS protocols in human research. The high degree of homology in reach-to-grasp circuitry between humans and rodents further implies that the application of NIBS to brain injury could be better informed by findings from pre-clinical rodent models and neurorehabilitation research. Here, we provide an overview of the advantages and limitations of using rodent models to advance our current understanding of human reach-to-grasp function, cortical circuitry, and reorganization. We propose that a cross-species comparison of reach-to-grasp recovery could provide a mechanistic framework for clinically efficacious NIBS treatments that could elicit better functional outcomes for patients.

High-Frequency rTMS of the Motor Cortex Modulates Cerebellar and Widespread Activity as Revealed by SVM

Functional magnetic resonance imaging (fMRI) studies have shown that the effect of repetitive transcranial magnetic stimulation (rTMS) can induce changes in remote brain regions. In the stimulated regions, low-frequency (≤1 Hz) rTMS induces inhibitory effects, while high-frequency (≥5 Hz) stimulation induces excitatory effects. However, these stereotypical effects arising from low- and high-frequency stimulation are based on measurements of motor evoked potentials (MEPs) induced by pulsed stimulation. To test the effects of rTMS on remote brain regions, the current study recruited 31 young healthy adults who participated in three rTMS sessions (10 Hz high frequency, 1 Hz low frequency, and sham) on three separate days. The stimulation target was based on individual fMRI activation in the motor cortex evoked by a finger movement task. Pre- and post-rTMS resting-state fMRI (RS-fMRI) were acquired. Regional homogeneity (ReHo) and degree centrality (DC) were calculated to measure the local and global connectivity, respectively. Compared with the sham session, high-frequency (10 Hz) rTMS significantly increased ReHo and DC in the right cerebellum, while low-frequency (1 Hz) stimulation did not significantly alter ReHo or DC. Then, using a newly developed PAIR support vector machine (SVM) method, we achieved accuracy of 93.18–97.24% by split-half validation for pairwise comparisons between conditions for ReHo or DC. While the univariate analyses suggest that high-frequency rTMS of the left motor cortex could affect distant brain activity in the right cerebellum, the multivariate SVM results suggest that both high- and low-frequency rTMS significantly modulated widespread brain activity. The current findings are useful for increasing the understanding of the mechanisms of rTMS, as well as guiding precise individualized rTMS treatment of movement disorders.

Brain-Machine Interface Induced Morpho-Functional Remodeling of the Neural Motor System in Severe Chronic Stroke

Brain-machine interfaces (BMI) permit bypass motor system disruption by coupling contingent neuroelectric signals related to motor activity with prosthetic devices that enhance afferent and proprioceptive feedback to the somatosensory cortex. In this study, we investigated neural plasticity in the motor network of severely impaired chronic stroke patients after an EEG-BMI-based treatment reinforcing sensorimotor contingency of ipsilesional motor commands. Our structural connectivity analysis revealed decreased fractional anisotropy in the splenium and body of the corpus callosum, and in the contralesional hemisphere in the posterior limb of the internal capsule, the posterior thalamic radiation, and the superior corona radiata. Functional connectivity analysis showed decreased negative interhemispheric coupling between contralesional and ipsilesional sensorimotor regions, and decreased positive intrahemispheric coupling among contralesional sensorimotor regions. These findings indicate that BMI reinforcing ipsilesional brain activity and enhancing proprioceptive function of the affected hand elicits reorganization of contralesional and ipsilesional somatosensory and motor-assemblies as well as afferent and efferent connection-related motor circuits that support the partial re-establishment of the original neurophysiology of the motor system even in severe chronic stroke.

The differential roles of contralesional frontoparietal areas in cortical reorganization after stroke

BACKGROUND

Studies examining the contribution of contralesional brain regions to motor recovery after stroke have revealed conflicting results comprising both supporting and disturbing influences. Especially the relevance of contralesional brain regions beyond primary motor cortex (M1) has rarely been studied, particularly concerning the temporal dynamics post-stroke.

METHODS

We, therefore, used online transcranial magnetic stimulation (TMS) interference to longitudinally assess the role of contralesional (right) frontoparietal areas for recovery of hand motor function after left hemispheric stroke: contralesional M1, contralesional dorsal premotor cortex (dPMC), and contralesional anterior intraparietal sulcus (IPS). Fourteen stroke patients and sixteen age-matched healthy subjects performed motor tasks of varying complexity with their (paretic) right hand. Motor performance was quantified using three-dimensional kinematic data. All patients were assessed twice, (i) in the first week, and (ii) after more than three months post-stroke.

RESULTS

While we did not observe a significant effect of TMS interference on movement kinematics following the stimulation of contralesional M1 and dPMC in the first week post-stroke, we found improvements of motor performance upon interference with contralesional IPS across motor tasks early after stroke, an effect that persisted into the later phase. By contrast, for dPMC, TMS-induced deterioration of motor performance was only evident three months post-stroke, suggesting that a supportive role of contralesional premotor cortex might evolve with reorganization.

CONCLUSION

We here highlight time-sensitive and region-specific effects of contralesional frontoparietal areas after left hemisphere stroke, which may influence on neuromodulation regimes aiming at supporting recovery of motor function post-stroke.

Timing of Repetitive Transcranial Magnetic Stimulation Onset for Upper Limb Function After Stroke: A Systematic Review and Meta-Analysis

Background: Repetitive transcranial magnetic stimulation (rTMS) is a promising intervention to promote upper limb recovery after stroke. We aimed to identify differences in the efficacy of rTMS treatment on upper limb function depending on the onset time post-stroke.

Methods: We searched PubMed, Embase, and the Cochrane Library to identify relevant RCTs from their inception to February 2018. RCTs on the effects of rTMS on upper limb function in adult patients with stroke were included. Study quality and risk of bias were assessed independently by two authors. Meta-analyses were performed for outcomes on individual upper limb outcome measures (function or activity) and for function and activity measures jointly, categorized by timing of treatment initiation. Timing of treatment initiation post-stroke was categorized as follows: acute to early subacute (<1 month), early subacute (1–3 months), late subacute (3–6 months), and chronic (>6 months).

Results: We included 38 studies involving 1,074 stroke patients. Subgroup analysis demonstrated benefit of rTMS applied within the first month post-stroke [MD = 9.31; 95% confidence interval (6.27–12.34); P < 0.0001], but not in the early subacute phase (1–3 months post-stroke) [MD = 1.14; 95% confidence interval (−5.32 to 7.59), P = 0.73) or chronic phase (>6 months post-stroke) [MD = 1.79; 95% confidence interval (−2.00 to 5.59]; P = 0.35), when assessed with a function test [Fugl-Meyer Arm test (FMA)]. There were no studies within the late subacute phase (3–6 months post-stroke) that used the FMA. Tests at the level of function revealed improved upper limb function after rTMS [SMD = 0.43; 95% confidence interval (0.02–0.75); P = 0.0001], but tests at the level of activity did not, independent of rTMS onset post-stroke [SMD = 0.17; 95% confidence interval (−0.09 to 0.44); P = 0.19]. Heterogeneities in the results of the individual studies included in the main analyses were large, as suggested by funnel plot asymmetry.

Conclusions: Based on the FMA, rTMS seems more beneficial only when started in the first month post-stroke. Tests at the level of function are likely more sensitive to detect beneficial rTMS effects on upper limb function than tests at the level of activity. However, heterogeneities in treatment designs and outcomes are high. Future rTMS trials should include the FMA and work toward a core set of outcome measures.

Effect of Repetitive Transcranial Magnetic Stimulation in Post-stroke Patients with Severe Upper-Limb Motor Impairment

Repetitive transcranial magnetic stimulation (rTMS) has been known to improve the motor function through modulation of excitability in the cerebral cortex. However, most studies with rTMS were limited to post-stroke patients with mild to moderate motor impairments. The effect of rTMS on severe upper-limb motor impairment remains unclear. Therefore, this study investigated the effects of rTMS on the upper extremity function in post-stroke patients with severe upper-limb motor impairment. Subjects were divided into 3 groups, low-, high-frequency rTMS and control group were received stimulation 10 times for 2 weeks. The motor scale of Fugl-Meyer Assessment (FMA) and cortical excitability on the unaffected hemisphere were measured before and after performing 10 rTMS sessions. The motor scale of upper extremity FMA (UE-FMA) and shoulder component of the UE-FMA were significantly improved in both low- and high-frequency rTMS groups. However, no significant improvement was observed in the wrist and hand components. No significant differences were noted in low- and high-frequency rTMS groups. The amplitude of motor evoked potential on the unaffected hemisphere showed a significant decrease in the low- and high-frequency stimulation groups. rTMS may be helpful in improving upper extremity motor function even in post-stroke patients with severe upper-limb motor impairment.

The effect and optimal parameters of repetitive transcranial magnetic stimulation on motor recovery in stroke patients: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

The primary aim of this meta-analysis was to evaluate the effects of repetitive transcranial magnetic stimulation (rTMS) on limb movement recovery post-stroke and cortex excitability, to explore the optimal parameters of rTMS and suitable stroke population. Second, adverse events were also included.

DATA SOURCES

The databases of PubMed, EBSCO, MEDLINE, the Cochrane Central Register of Controlled Trials, EBM Reviews-Cochrane Database, the Chinese National Knowledge Infrastructure, and the Chinese Science and Technology Journals Database were searched for randomized controlled trials exploring the effects of rTMS on limb motor function recovery post-stroke before December 2018.

REVIEW METHODS

The effect sizes of rTMS on limb motor recovery, the effect size of rTMS stimulation parameters, and different stroke population were summarized by calculating the standardized mean difference (SMD) and the 95% confidence interval using fixed/random effect models as appropriate.

RESULTS

For the motor function assessment, 42 eligible studies involving 1168 stroke patients were identified. The summary effect size indicated that rTMS had positive effects on limb motor recovery (SMD = 0.50, P < 0.00001) and activities of daily living (SMD = 0.82, P < 0.00001), and motor-evoked potentials of the stimulated hemisphere differed according to the stimulation frequency, that is, the high-frequency group (SMD = 0.57, P = 0.0006), except the low-frequency group (SMD = -0.27, P = 0.05). No significant differences were observed among the stimulation parameter subgroups except for the sessions subgroup ( P = 0.02). Only 10 included articles reported transient mild discomfort after rTMS.

CONCLUSIONS

rTMS promoted the recovery of limb motor function and changed the cortex excitability. rTMS may be better for early and pure subcortical stroke patients. Regarding different stimulation parameters, the number of stimulation sessions has an impact on the effect of rTMS.

Low-frequency rTMS of the unaffected hemisphere in stroke patients: A systematic review

The aim of this review was to summarize the evidence for the effectiveness of low-frequency (LF) repetitive transcranial magnetic stimulation (rTMS) over the unaffected hemisphere in promoting functional recovery after stroke. We performed a systematic search of the studies using LF-rTMS over the contralesional hemisphere in stroke patients and reviewed the 67 identified articles. The studies have been gathered together according to the time interval that had elapsed between the stroke onset and the beginning of the rTMS treatment. Inhibitory rTMS of the contralesional hemisphere can induce beneficial effects on stroke patients with motor impairment, spasticity, aphasia, hemispatial neglect and dysphagia, but the therapeutic clinical significance is unclear. We observed considerable heterogeneity across studies in the stimulation protocols. The use of different patient populations, regardless of lesion site and stroke aetiology, different stimulation parameters and outcome measures means that the studies are not readily comparable, and estimating real effectiveness or reproducibility is very difficult. It seems that careful experimental design is needed and it should consider patient selection aspects, rTMS parameters and clinical assessment tools. Consecutive sessions of rTMS, as well as the combination with conventional rehabilitation therapy, may increase the magnitude and duration of the beneficial effects. In an increasing number of studies, the patients have been enrolled early after stroke. The prolonged follow-up in these patients suggests that the effects of contralesional LF-rTMS can be long-lasting. However, physiological evidence indicating increased synaptic plasticity, and thus, a more favourable outcome, in the early enrolled patients, is still lacking. Carefully designed clinical trials designed are required to address this question. LF rTMS over unaffected hemisphere may have therapeutic utility, but the evidence is still preliminary and the findings need to be confirmed in further randomized controlled trials.

The Use of Repetitive Transcranial Magnetic Stimulation for Stroke Rehabilitation: A Systematic Review

OBJECTIVES

Stroke is a leading cause of disability. Alternative and more effective techniques for stroke rehabilitation have been sought to overcome limitations of conventional therapies. Repetitive transcranial magnetic stimulation (rTMS) arises as a promising tool in this context. This systematic review aims to provide a state of the art on the application of rTMS in stroke patients and to assess its effectiveness in clinical rehabilitation of motor function.

METHODS

Studies included in this review were identified by searching PubMed and ISI Web of Science. The search terms were (rTMS OR "repetitive transcranial magnetic stimulation") AND (stroke OR "cerebrovascular accident" OR CVA) AND (rehab OR rehabilitation OR recover*). The retrieved records were assessed for eligibility and the most relevant features extracted to a summary table.

RESULTS

Seventy out of 691 records were deemed eligible, according to the selection criteria. The majority of the articles report rTMS showing potential in improving motor function, although some negative reports, all from randomized controlled trials, contradict this claim. Future studies are needed because there is a possibility that a bias for non-publication of negative results may be present.

CONCLUSIONS

rTMS has been shown to be a promising tool for stroke rehabilitation, in spite of the lack of standard operational procedures and harmonization. Efforts should be devoted to provide a greater understanding of the underlying mechanisms and protocol standardization.

Role of the Contralesional vs. Ipsilesional Hemisphere in Stroke Recovery

Following a stroke, the resulting lesion creates contralateral motor impairment and an interhemispheric imbalance involving hyperexcitability of the contralesional hemisphere. Neuronal reorganization may occur on both the ipsilesional and contralesional hemispheres during recovery to regain motor functionality and therefore bilateral activation for the hemiparetic side is often observed. Although ipsilesional hemispheric reorganization is traditionally thought to be most important for successful recovery, definitive conclusions into the role and importance of the contralesional motor cortex remain under debate. Through examining recent research in functional neuroimaging investigating motor cortex changes post-stroke, as well as brain-computer interface (BCI) and transcranial magnetic stimulation (TMS) therapies, this review attempts to clarify the contributions of each hemisphere toward recovery. Several functional magnetic resonance imaging studies suggest that continuation of contralesional hemisphere hyperexcitability correlates with lesser recovery, however a subset of well-recovered patients demonstrate contralesional motor activity and show decreased functional capability when the contralesional hemisphere is inhibited. BCI therapy may beneficially activate either the contralesional or ipsilesional hemisphere, depending on the study design, for chronic stroke patients who are otherwise at a functional plateau. Repetitive TMS used to excite the ipsilesional motor cortex or inhibit the contralesional hemisphere has shown promise in enhancing stroke patients' recovery.

Anatomical Parameters of tDCS to Modulate the Motor System after Stroke: A Review

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation method to modulate the local field potential in neural tissue and consequently, cortical excitability. As tDCS is relatively portable, affordable, and accessible, the applications of tDCS to probe brain-behavior connections have rapidly increased in the last 10 years. One of the most promising applications is the use of tDCS to modulate excitability in the motor cortex after stroke and promote motor recovery. However, the results of clinical studies implementing tDCS to modulate motor excitability have been highly variable, with some studies demonstrating that as many as 50% or more of patients fail to show a response to stimulation. Much effort has therefore been dedicated to understand the sources of variability affecting tDCS efficacy. Possible suspects include the placement of the electrodes, task parameters during stimulation, dosing (current amplitude, duration of stimulation, frequency of stimulation), individual states (e.g., anxiety, motivation, attention), and more. In this review, we first briefly review potential sources of variability specific to stroke motor recovery following tDCS. We then examine how the anatomical variability in tDCS placement [e.g., neural target(s) and montages employed] may alter the neuromodulatory effects that tDCS exerts on the post-stroke motor system.

Cross-Cultural Adaptation and Validation of the Jebsen-Taylor Hand Function Test in an Italian Population

Objective. This paper describes the Italian translation and adaptation to the Italian culture of the original version of the Jebsen-Taylor hand function test and conveys the procedure for testing its validity and reliability. Design. The cultural adaptation process and validation were based on data from a group of people with no clinical evidence of disease or impairment of the upper limbs. The process required a forward and reverse translation in its original language. The scale obtained was reviewed by 8 experts in the field of psychometrics dealing with statistical methods that are useful for the behavioral and social sciences. The Italian adapted version of the JTHFT was then produced and validated. Participants. The test was submitted to 320 people with no clinical evidence of disease in order to test its acceptability and consistency. Results. The total time required to perform each subtest was 80.16 ± 43.13 seconds for the nondominant hand (NDH) and 49.97 ± 27.28 seconds for the dominant hand (DH). The internal consistency (assessed with Pearson's r) and the reliability or the construct validity (assessed with Cronbach's alpha) are significative. Conclusions. This is the first study reporting the result of the translation, cultural adaptation, and validation protocols of the JTHFT in Italian. It provides a new tool for Italian professionals to measure the functionality of the hand in participants with various upper limb pathologies.