Transcranial direct current stimulation (tDCS): does it have merit in stroke rehabilitation? A systematic review

Kinematic descriptors of arm reaching movement are sensitive to hemisphere-specific immediate neuromodulatory effects of transcranial direct current stimulation post stroke

Transcranial direct current stimulation (tDCS) exerts beneficial effects on motor recovery after stroke, presumably by enhancement of adaptive neural plasticity. However, patients with extensive damage may experience null or deleterious effects with the predominant application mode of anodal (excitatory) stimulation of the damaged hemisphere. In such cases, excitatory stimulation of the non-damaged hemisphere might be considered. Here we asked whether tDCS exerts a measurable effect on movement quality of the hemiparetic upper limb, following just a single treatment session. Such effect may inform on the hemisphere that should be excited. Using a single-blinded crossover experimental design, stroke patients and healthy control subjects were assessed before and after anodal, cathodal and sham tDCS, each provided during a single session of reaching training (repeated point-to-point hand movement on an electronic tablet). Group comparisons of endpoint kinematics at baseline-number of peaks in the speed profile (NoP; smoothness), hand-path deviations from the straight line (SLD; accuracy) and movement time (MT; speed)-disclosed greater NoP, larger SLD and longer MT in the stroke group. NoP and MT revealed an advantage for anodal compared to sham stimulation of the lesioned hemisphere. NoP and MT improvements under anodal stimulation of the non-lesioned hemisphere correlated positively with the severity of hemiparesis. Damage to specific cortical regions and white-matter tracts was associated with lower kinematic gains from tDCS. The study shows that simple descriptors of movement kinematics of the hemiparetic upper limb are sensitive enough to demonstrate gain from neuromodulation by tDCS, following just a single session of reaching training. Moreover, the results show that tDCS-related gain is affected by the severity of baseline motor impairment, and by lesion topography.

Transcranial direct current stimulation alters cerebrospinal fluid-interstitial fluid exchange in mouse brain

BACKGROUND

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has gained prominence recently. Clinical studies have explored tDCS as an adjunct to neurologic disease rehabilitation, with evidence suggesting its potential in modulating brain clearance mechanisms. The glymphatic system, a proposed brain waste clearance system, posits that cerebrospinal fluid-interstitial fluid (CSF-ISF) exchange aids in efficient metabolic waste removal. While some studies have linked tDCS to astrocytic inositol trisphosphate (IP3)/Ca2+ signaling, the impact of tDCS on CSF-ISF exchange dynamics remains unclear.

HYPOTHESIS

tDCS influences the dynamics of CSF-ISF exchange through astrocytic IP3/Ca2+ signaling.

METHODS

In this study, we administered tDCS (0.1 mA for 10 min) to C57BL/6N mice anesthetized with ketamine-xylazine (KX). The anode was positioned on the cranial bone above the cortex, and the cathode was inserted into the neck. Following tDCS, we directly assessed brain fluid dynamics by injecting biotinylated dextran amine (BDA) as a CSF tracer into the cisterna magna (CM). The brain was then extracted after either 30 or 60 min and fixed. After 24 h, the sectioned brain slices were stained with Alexa 594-conjugated streptavidin (SA) to visualize BDA using immunohistochemistry. We conducted Electroencephalography (EEG) recordings and aquaporin 4 (AQP4)/CD31 immunostaining to investigate the underlying mechanisms of tDCS. Additionally, we monitored the efflux of Evans blue, injected into the cisterna magna, using cervical lymph node imaging. Some experiments were subsequently repeated with inositol trisphosphate receptor type 2 (IP3R2) knockout (KO) mice.

RESULTS

Post-tDCS, we observed an increased CSF tracer influx, indicating a modulation of CSF-ISF exchange by tDCS. Additionally, tDCS appeared to enhance the brain's metabolic waste efflux. EEG recordings showed an increase in delta wave post-tDCS. But no significant change in AQP4 expression was detected 30 min post-tDCS. Besides, we found no alteration in CSF-ISF exchange and delta wave activity in IP3R2 KO mice after tDCS.

CONCLUSION

Our findings suggest that tDCS augments the glymphatic system's influx and efflux. Through astrocytic IP3/Ca2+ signaling, tDCS was found to modify the delta wave, which correlates positively with brain clearance. This study underscores the potential of tDCS in modulating brain metabolic waste clearance.

Clinical Comparison between HD-tDCS and tDCS for Improving Upper Limb Motor Function: A Randomized, Double-Blinded, Sham-Controlled Trial

Background

Stroke is a common and frequently occurring disease among middle-aged and elderly people, with approximately 55%-75% of patients remaining with upper limb dysfunction. How to promote the recovery of motor function at an early stage is crucial to the life of the patient.

Objectives

This study aimed to investigate whether high-definition transcranial direct current stimulation (HD-tDCS) of the primary motor cortex (M1) functional area in poststroke patients in the subacute phase is more effective in improving upper limb function than conventional tDCS.

Methods

This randomized, sham-controlled clinical trial included 69 patients with subcortical stroke. They were randomly divided into the HD-tDCS, anodal tDCS (a-tDCS), and sham groups. Each group received 20 sessions of stimulation. The patients were assessed using the Action Research Arm Test, Fugl-Meyer score for upper extremities, Motor Function Assessment Scale, and modified Barthel index (MBI) pretreatment and posttreatment.

Results

The intragroup comparison scores improved after 4 weeks of treatment. The HD-tDCS group showed a slightly greater, but nonsignificant improvement as compared to a-tDCS group in terms of mean change observed in function of trained items. The MBI score of the HD-tDCS group was maintained up to 8 weeks of follow-up and was higher than that in the a-tDCS group.

Conclusion

Both HD-tDCS and a-tDCS can improve upper limb motor function and daily activities of poststroke patients in the subacute stage. This trial is registered with ChiCTR2000031314.

Noninvasive brain stimulation for spasticity rehabilitation in multiple sclerosis: A systematic review of randomized controlled trials

OBJECTIVE

To investigate the effects of noninvasive brain stimulation (NIBS) on spasticity in people with multiple sclerosis (PwMS).

LITERATURE SURVEY

We searched PubMed, SCOPUS, MEDLINE, REHABDATA, PEDro, CINAHL, AMED, and Web of Science until December 2022.

METHODOLOGY

Studies were selected if they included PwMS, used transcranial direct current stimulation (tDCS) or repetitive transcranial magnetic stimulation (rTMS) as a main intervention, and were randomized controlled trials (RCTs) including at least one outcome measure evaluating spasticity. Two researchers individually screened the selected studies. The study's quality was assessed using the Cochrane Collaborations tool. The researchers decided that the meta-analysis was not possible because the treatment interventions varied among the selected studies.

SYNTHESIS

In total, 147 studies were reviewed. Of them, nine studies met the eligibility criteria and included 193 PwMS (mean age = 43.2 years), 54.4% of whom were female. Eight studies were considered "high" quality and one was considered "moderate" quality. Seven studies that used rTMS demonstrated a significant decrease in spasticity in PwMS after the intervention. The remaining studies that provided tDCS did not show meaningful effects.

CONCLUSIONS

The evidence for the influences of rTMS on spasticity in PwMS is promising. The evidence for the impact of tDCS on spasticity in PwMS was limited. Further RCTs with long-term follow-ups are encouraged.

Simultaneous high-definition transcranial direct current stimulation and robot-assisted gait training in stroke patients

This study investigates whether simultaneous high-definition transcranial direct current stimulation (HD-tDCS) enhances the effects of robot-assisted gait training in stroke patients. Twenty-four participants were randomly allocated to either the robot-assisted gait training with real HD-tDCS group (real HD-tDCS group) or robot-assisted gait training with sham HD-tDCS group (sham HD-tDCS group). Over four weeks, both groups completed 10 sessions. The 10 Meter Walk Test, Timed Up and Go, Functional Ambulation Category, Functional Reach Test, Berg Balance Scale, Dynamic Gait Index, Fugl-Meyer Assessment, and Korean version of the Modified Barthel Index were conducted before, immediately after, and one month after the intervention. The real HD-tDCS group showed significant improvements in the 10 Meter Walk Test, Timed Up and Go, Functional Reach Test, and Berg Balance Scale immediately and one month after the intervention, compared with before the intervention. Significant improvements in the Dynamic Gait Index and Fugl-Meyer Assessment were also observed immediately after the intervention. The sham HD-tDCS group showed no significant improvements in any of the tests. Application of HD-tDCS during robot-assisted gait training has a positive effect on gait and physical function in chronic stroke patients, ensuring long-term training effects. Our results suggest the effectiveness of HD-tDCS as a complementary tool to enhance robotic gait rehabilitation therapy in chronic stroke patients.

Effects of anodal tDCS on resting state eeg power and motor function in acute stroke: a randomized controlled trial

BACKGROUND

Anodal transcranial direct current stimulation (tDCS) is a beneficial adjunctive tool in stroke rehabilitation. However, only a few studies have investigated its effects on acute stroke and recruited only individuals with mild motor deficits. This study investigated the effect of five consecutive sessions of anodal tDCS and conventional physical therapy on brain activity and motor outcomes in individuals with acute stroke, with low and high motor impairments.

METHODS

Thirty participants were recruited and randomly allocated to either the anodal or sham tDCS group. Five consecutive sessions of tDCS (1.5 mA anodal or sham tDCS for 20 min) were administered, followed by conventional physical therapy. Electroencephalography (EEG), Fugl-Meyer Motor Assessment (FMA), and Wolf Motor Function Test (WMFT) were performed at pre-, post-intervention (day 5), and 1-month follow-up. Sub-analyses were performed on participants with low and high motor impairments. The relationship between EEG power and changes in motor functions was assessed.

RESULTS

Linear regression showed a significant positive correlation between beta bands and the FMA score in the anodal group. Elevated high frequency bands (alpha and beta) were observed at post-intervention and follow-up in all areas of both hemispheres in the anodal group, while only in the posterior area of the non-lesioned hemisphere in the sham group; however, such elevation induced by tDCS was not greater than sham. Lower limb function assessed by FMA was improved in the anodal group compared with the sham group at post-intervention and follow-up only in those with low motor impairment. For the upper limb outcomes, no difference between groups was found.

CONCLUSIONS

Five consecutive days of anodal tDCS and physical therapy in acute stroke did not result in a superior improvement of beta bands that commonly related to stroke recovery over sham, but improved lower extremity functions with a post-effect at 1-month follow-up in low motor impairment participants. The increase of beta bands in the lesioned brain in the anodal group was associated with improvement in lower limb function.

TRIAL REGISTRATION

NCT04578080, date of first registration 10/01/2020.

A review of combined neuromodulation and physical therapy interventions for enhanced neurorehabilitation

Rehabilitation approaches for individuals with neurologic conditions have increasingly shifted toward promoting neuroplasticity for enhanced recovery and restoration of function. This review focuses on exercise strategies and non-invasive neuromodulation techniques that target neuroplasticity, including transcranial magnetic stimulation (TMS), vagus nerve stimulation (VNS), and peripheral nerve stimulation (PNS). We have chosen to focus on non-invasive neuromodulation techniques due to their greater potential for integration into routine clinical practice. We explore and discuss the application of these interventional strategies in four neurological conditions that are frequently encountered in rehabilitation settings: Parkinson's Disease (PD), Traumatic Brain Injury (TBI), stroke, and Spinal Cord Injury (SCI). Additionally, we discuss the potential benefits of combining non-invasive neuromodulation with rehabilitation, which has shown promise in accelerating recovery. Our review identifies studies that demonstrate enhanced recovery through combined exercise and non-invasive neuromodulation in the selected patient populations. We primarily focus on the motor aspects of rehabilitation, but also briefly address non-motor impacts of these conditions. Additionally, we identify the gaps in current literature and barriers to implementation of combined approaches into clinical practice. We highlight areas needing further research and suggest avenues for future investigation, aiming to enhance the personalization of the unique neuroplastic responses associated with each condition. This review serves as a resource for rehabilitation professionals and researchers seeking a comprehensive understanding of neuroplastic exercise interventions and non-invasive neuromodulation techniques tailored for specific diseases and diagnoses.

Comparison of bihemispheric and unihemispheric M1 transcranial direct current stimulations during physical therapy in subacute stroke patients: A randomized controlled trial

BACKGROUND

Despite the central origin of stroke affecting the primary motor cortex M1, most physical and occupational rehabilitation programs focus on peripheral treatments rather than addressing the central origin of the problem. This highlights the urgent need for effective protocols to improve neurological rehabilitation and achieve better long-term functional outcomes.

OBJECTIVES

Our hypothesis was that the bihemispheric delivery of transcranial direct current stimulation (tDCS) is superior to unihemispheric in enhancing motor function after stroke, in both the upper and lower extremities.

METHODS

35 sub-acute ischemic stroke survivors were randomly divided into three groups: bihemispheric and unihemispheric treatment groups, or sham groups. Each participant received a 20-minute session of tDCS with an intensity of 2 mA during physical therapy sessions, three days a week, for four weeks. The outcomes were measured using Fugl-Meyer assessment scale, modified Ashworth scale, Berg balance scale, and serum brain-derived neurotrophic factor (BDNF) levels.

RESULTS

One-way ANOVA test indicated a significant effect of both treatment protocols on the upper extremity (p = < 0.001) and lower extremity (p = .034) for motor measures, but there was no difference between the two (p = .939). Kruskal Wallis test for spasticity showed a significant improvement in both treatment groups for elbow (p = .036) and wrist flexors (p = .025), compared to the sham group. However, there was no statistically significant difference in spasticity between uni- and bihemispheric stimulation for elbow (p = .731) or wrist flexors (p = .910).

CONCLUSION

There is no statistically significant difference in efficacy between bihemispheric and unihemispheric tDCS in patients presenting with acute ischemic stroke. .

Patient-tailored transcranial direct current stimulation to improve stroke rehabilitation: study protocol of a randomized sham-controlled trial

BACKGROUND

Many patients do not fully regain motor function after ischemic stroke. Transcranial direct current stimulation (TDCS) targeting the motor cortex may improve motor outcome as an add-on intervention to physical rehabilitation. However, beneficial effects on motor function vary largely among patients within and across TDCS trials. In addition to a large heterogeneity of study designs, this variability may be caused by the fact that TDCS was given as a one-size-fits-all protocol without accounting for anatomical differences between subjects. The efficacy and consistency of TDCS might be improved by a patient-tailored design that ensures precise targeting of a physiologically relevant area with an appropriate current strength.

METHODS

In a randomized, double-blinded, sham-controlled trial, patients with subacute ischemic stroke and residual upper-extremity paresis will receive two times 20 min of focal TDCS of ipsilesional primary motor hand area (M1-HAND) during supervised rehabilitation training three times weekly for 4 weeks. Anticipated 60 patients will be randomly assigned to active or sham TDCS of ipsilesional M1-HAND, using a central anode and four equidistant cathodes. The placement of the electrode grid on the scalp and current strength at each cathode will be personalized based on individual electrical field models to induce an electrical current of 0.2 V/m in the cortical target region resulting in current strengths between 1 and 4 mA. Primary endpoint will be the difference in change of Fugl-Meyer Assessment of Upper Extremity (FMA-UE) score between active TDCS and sham at the end of the intervention. Exploratory endpoints will include UE-FMA at 12 weeks. Effects of TDCS on motor network connectivity and interhemispheric inhibition will be assessed with functional MRI and transcranial magnetic stimulation.

DISCUSSION

The study will show the feasibility and test the efficacy of personalized, multi-electrode anodal TDCS of M1-HAND in patients with subacute stroke patients with upper-extremity paresis. Concurrent multimodal brain mapping will shed light into the mechanisms of action of therapeutic personalized TDCS of M1-HAND. Together, the results from this trial may inform future personalized TDCS studies in patients with focal neurological deficits after stroke.

Transcranial direct current stimulation for upper extremity spasticity rehabilitation in stroke survivors: A systematic review of randomized controlled trials

OBJECTIVES

To examine the effects of transcranial direct current stimulation (tDCS) on upper extremity spasticity after stroke and to define the most effective tDCS parameters.

LITERATURE SURVEY

Systematic review in the following databases: PubMed, SCOPUS, PEDro, CINAHL, MEDLINE, REHABDATA, AMED, and Web of Science databases. Studies up to June 2020 were included.

METHODOLOGY

Studies were included if the sample was composed of individuals with stroke, the intervention followed a tDCS intervention (alone or combined with another intervention), and the study was a randomized controlled trial including at least one measurement assessing upper extremity spasticity. Two authors independently screened the included studies. Conflicting decisions between authors were resolved by discussion with the third author. The methodological quality was assessed using the Cochrane Collaboration's tool. The authors determined that the meta-analysis was not feasible due to the heterogeneity in the protocols among the included studies.

SYNTHESIS

After the screening of 1204 records, a total of seven studies met the specified inclusion criteria and involved 320 participants (mean age = 60.3), 31.1% of whom were females. Patients with ischemic stroke comprised 77.2% of the total patients, and 42.2% were with right hemispheric stroke. Six studies exhibited "high" quality and one exhibited "moderate" quality. Five of the selected studies that combined the tDCS intervention and other traditional interventions showed a significant reduction in upper extremity spasticity after stroke following tDCS intervention. The other two studies that delivered tDCs alone did not show a significant difference.

CONCLUSIONS

The evidence for the effect of tDCS on upper extremity spasticity after stroke was limited. The optimal tDCS treatment dosage remains unclear. Additional studies with large sample sizes and long-term follow-up are strongly warranted.

Transcranial direct current stimulation (tDCS) effects on upper limb motor function in stroke: an overview review of the systematic reviews

BACKGROUND

Stroke is the prime cause of disability in the elderly population. Transcranial direct current stimulation (tDCS) is an emerging noninvasive brain stimulation in rehabilitating upper limb function post-stroke. However, mixed evidence exists in the literature and ambiguous conclusions regarding the effect of tDCS on upper limb function.

OBJECTIVE

This study aimed to assess the current evidence on the effect of (tDCS) on upper limb motor function and activities of daily living in patients after stroke by conducting an overview of systematic reviews.

METHODOLOGY

We performed electronic database searches and gray literature searches for the articles.

RESULTS

Two distinct literature searches gathered a total of 203 studies. Out of them, six systematic reviews and meta-analyses were included for methodological quality assessment and data extraction. All included studies were determined to be of good to high quality based on a methodological appraisal using the Assessment of Multiple Systematic Reviews checklist.

CONCLUSION

Identified evidence suggests that tDCS has superior effects to control interventions in improving functions of the upper limb and activities of daily living in patients who have had a stroke. Moreover, cathodal stimulation over the non-affected brain region was more effective than anodal and dual tDCS stimulation.

Individual electric field predicts functional connectivity changes after anodal transcranial direct-current stimulation in chronic stroke

The neuromodulation effect of anodal tDCS is not thoroughly studied, and the heterogeneous profile of stroke individuals with brain lesions would further complicate the stimulation outcomes. This study aimed to investigate the functional changes in sensorimotor areas induced by anodal tDCS and whether individual electric field could predict the functional outcomes. Twenty-five chronic stroke survivors were recruited and divided into tDCS group (n = 12) and sham group (n = 13). Increased functional connectivity (FC) within the surrounding areas of ipsilesional primary motor cortex (M1) was only observed after anodal tDCS. Averaged FC among the ipsilesional sensorimotor regions was observed to be increased after anodal tDCS (t(11) = 2.57, p = 0.026), but not after sham tDCS (t(12) = 0.69, p = 0.50). Partial least square analysis identified positive correlations between electric field (EF) strength normal to the ipsilesional M1 surface and individual FC changes in tDCS group (r = 0.84, p < 0.001) but not in sham group (r = 0.21, p = 0.5). Our results indicated anodal tDCS facilitates the FC within the ipsilesional sensorimotor network in chronic stroke subjects, and individual electric field predicts the functional outcomes.

Applied strategies of neuroplasticity

Various levels of somatotopic organization are present throughout the human nervous system. However, this organization can change when needed based on environmental demands, a phenomenon known as neuroplasticity. Neuroplasticity can occur when learning a new motor skill, adjusting to life after blindness, or following a stroke. Following an injury, these neuroplastic changes can be adaptive or maladaptive, and often occur regardless of whether rehabilitation occurs or not. But not all movements produce neuroplasticity, nor do all rehabilitation interventions. Here, we focus on research regarding how to maximize adaptive neuroplasticity while also minimizing maladaptive plasticity, known as applied neuroplasticity. Emphasis is placed on research exploring how best to apply neuroplastic principles to training environments and rehabilitation protocols. By studying and applying these principles in research and clinical practice, it is hoped that learning of skills and regaining of function and independence can be optimized.

The influence of a single transcranial direct current stimulation session on physical fitness in healthy subjects: a systematic review

Physical fitness is of indisputable importance for both health, and sports. Currently, the brain is being increasingly recognized as a contributor to physical fitness. Hereby, transcranial direct current stimulation (tDCS), as an ergogenic aid, has gained scientific interest. The current PRISMA-adherent review aimed to examine the effect of tDCS on the three core components of physical fitness: muscle strength, -endurance and cardiopulmonary endurance. Randomized controlled- or cross-over trials evaluating the effect of a single tDCS session (vs. sham) in healthy individuals were included. Hereby, a wide array of tDCS-related factors (e.g., tDCS montage and dose) was taken into account. Thirty-five studies (540 participants) were included. Between-study heterogeneity in factors such as age, activity level, tDCS protocol, and outcome measures was large. The capacity of tDCS to improve physical fitness varied substantially across studies. Nevertheless, muscle endurance was most susceptible to improvements following anodal tDCS (AtDCS), with 69% of studies (n = 11) investigating this core component of physical fitness reporting positive effects. The primary motor cortex and dorsolateral prefrontal cortex were targeted the most, with positive results being reported on muscle and cardiopulmonary endurance. Finally, online tDCS seemed most beneficial, and no clear relationship between tDCS and dose-related parameters seemed present. These findings can contribute to optimizing tDCS interventions during the rehabilitation of patients with a variety of (chronic) diseases such as cardiovascular disease. Therefore, future studies should focus on further unraveling the potential of AtDCS on physical fitness and, more specifically, muscle endurance in both healthy subjects and patients suffering from (chronic) diseases. This study was registered in Prospero with the registration number CRD42021258529. "To enable PROSPERO to focus on COVID-19 registrations during the 2020 pandemic, this registration record was automatically published exactly as submitted. The PROSPERO team has not checked eligibility".

Transcranial direct current stimulation with virtual reality versus virtual reality alone for upper extremity rehabilitation in stroke: A meta-analysis

Background

Stroke is one of the most prevalent diseases. Motor impairment in patients with stroke frequently affects the upper extremities. Several randomized clinical trials (RCTs) have tried to prove whether or not the combination of transcranial direct current stimulation (tDCS) with virtual reality (VR) is superior to VR alone for upper extremity rehabilitation.

Methods

We searched Embase, MEDLINE, the Cochrane Library database, and Clinicaltrials.gov for relevant RCTs published before June 10, 2022. The results were analyzed by using standard mean differences (SMD) and 95% confidence intervals (95% CI).

Results

We pooled 120 patients from 4 RCTs. There were no significant improvements in the Fugl-Meyer Upper Extremity scale (SMD = 0.51; 95% CI, -0.04 to 1.06), the Box and Block Test (SMD = 0.42; 95% CI, -0.02 to 0.86), and the Modified Ashworth Scale after the combined treatment of tDCS and VR. But tDCS combined with VR could enhance the Barthel Index scores in patients with stroke compared to VR alone (SMD = 0.49; 95% CI, 0.04 to 0.94).

Conclusions

The combination of tDCS and VR can improve the quality of daily living in patients with stroke. No more satisfactory efficacy has been demonstrated in terms of upper extremity function. However, we observe a distinct trend toward significance in some outcomes.

Neurocapillary-Modulation

OBJECTIVES

We consider two consequences of brain capillary ultrastructure in neuromodulation. First, blood-brain barrier (BBB) polarization as a consequence of current crossing between interstitial space and the blood. Second, interstitial current flow distortion around capillaries impacting neuronal stimulation.

MATERIALS AND METHODS

We developed computational models of BBB ultrastructure morphologies to first assess electric field amplification at the BBB (principle 1) and neuron polarization amplification by the presence of capillaries (principle 2). We adapt neuron cable theory to develop an analytical solution for maximum BBB polarization sensitivity.

RESULTS

Electrical current crosses between the brain parenchyma (interstitial space) and capillaries, producing BBB electric fields (EBBB) that are >400x of the average parenchyma electric field (ĒBRAIN), which in turn modulates transport across the BBB. Specifically, for a BBB space constant (λBBB) and wall thickness (dth-BBB), the analytical solution for maximal BBB electric field (EABBB) is given as: (ĒBRAIN × λBBB)/dth-BBB. Electrical current in the brain parenchyma is distorted around brain capillaries, amplifying neuronal polarization. Specifically, capillary ultrastructure produces ∼50% modulation of the ĒBRAIN over the ∼40 μm inter-capillary distance. The divergence of EBRAIN (Activating function) is thus ∼100 kV/m2 per unit ĒBRAIN.

CONCLUSIONS

BBB stimulation by principle 1 suggests novel therapeutic strategies such as boosting metabolic capacity or interstitial fluid clearance. Whereas the spatial profile of EBRAIN is traditionally assumed to depend only on macroscopic anatomy, principle 2 suggests a central role for local capillary ultrastructure-which impact forms of neuromodulation including deep brain stimulation (DBS), spinal cord stimulation (SCS), transcranial magnetic stimulation (TMS), electroconvulsive therapy (ECT), and transcranial electrical stimulation (tES)/transcranial direct current stimulation (tDCS).

Changes in somatosensory evoked potentials elicited by lateral cerebellar nucleus deep brain stimulation in the naïve rodent

Deep brain stimulation (DBS) of the deep cerebellar nuclei has been shown to enhance perilesional cortical excitability and promote motor rehabilitation in preclinical models of cortical ischemia and is currently being evaluated in patients with chronic, post-stroke deficits. Understanding the effects of cerebellar DBS on contralateral sensorimotor cortex may be key to developing approaches to optimize stimulation delivery and treatment outcomes. Using the naïve rat model, we characterized the effects of DBS of the lateral cerebellar nucleus (LCN) on somatosensory evoked potentials (SSEPs) and evaluated their potential use as a surrogate index of cortical excitability. SSEPs were recorded concurrently with continuous 30 Hz or 100 Hz LCN DBS and compared to the DBS OFF condition. Ratios of SSEP peak to peak amplitude during 100 Hz LCN DBS to DBS OFF at longer latency peaks were significantly>1, suggesting that cortical excitability was enhanced as a result of LCN DBS. Although changes in SSEP peak to peak amplitudes were observed, they were modest in relation to previously reported effects on motor cortical excitability. Overall, our findings suggest that LCN output influences thalamocortical somatosensory pathways, however further work is need to better understand the potential role of SSEPs in optimizing therapy.

Rehabilitation Interventions Combined with Noninvasive Brain Stimulation on Upper Limb Motor Function in Stroke Patients

(1) Background: This systematic review aimed to focus on the effects of rehabilitation interventions combined with noninvasive brain stimulation on upper limb motor function in stroke patients. (2) Methods: PubMed, MEDLINE, and CINAHL were used for the literature research. Articles were searched using the following terms: "Stroke OR CVA OR cerebrovascular accident" AND "upper limb OR upper extremity" AND "NIBS OR Non-Invasive Brain Stimulation" OR "rTMS" OR "repetitive transcranial magnetic stimulation" OR "tDCS" OR "transcranial direct current stimulation" AND "RCT" OR randomized control trial." In total, 12 studies were included in the final analysis. (3) Results: Analysis using the Physiotherapy Evidence Database scale for qualitative evaluation of the literature rated eight articles as "excellent" and four as "good." Combined rehabilitation interventions included robotic therapy, motor imagery using brain-computer interaction, sensory control, occupational therapy, physiotherapy, task-oriented approach, task-oriented mirror therapy, neuromuscular electrical stimulation, and behavior observation therapy. (4) Conclusions: Although it is difficult to estimate the recovery of upper limb motor function in stroke patients treated with noninvasive brain stimulation alone, a combination of a task-oriented approach, occupational therapy, action observation, wrist robot-assisted rehabilitation, and physical therapy can be effective.

Using non-invasive transcranial direct current stimulation for neglect and associated attentional deficits following stroke

Neglect is a disabling neuropsychological syndrome that is frequently observed following right-hemispheric stroke. Affected individuals often present with multiple attentional deficits, ranging from reduced orienting towards contralesional space to a generalized impairment in maintaining attention over time. Although a degree of spontaneous recovery occurs in most patients, in some individuals this condition can be treatment-resistant with prominent ongoing non-spatial deficits. Further, there is a large inter-individual variability in response to different therapeutic approaches. Given its potential to alter neuronal excitability and affect neuroplasticity, non-invasive brain stimulation is a promising tool that could potentially be utilized to facilitate recovery. However, there are many outstanding questions regarding its implementation in this heterogeneous patient group. Here we provide a critical overview of the available evidence on the use of non-invasive electrical brain stimulation, focussing on transcranial direct current stimulation (tDCS), to improve neglect and associated attentional deficits after right-hemispheric stroke. At present, there is insufficient robust evidence supporting the clinical use of tDCS to alleviate symptoms of neglect. Future research would benefit from careful study design, enhanced precision of electrical montages, multi-modal approaches exploring predictors of response, tailored dose-control applications and increased efforts to evaluate standalone tDCS versus its incorporation into combination therapy.

Combining Robot-Assisted Gait Training and Non-Invasive Brain Stimulation in Chronic Stroke Patients: A Systematic Review

Gait impairment is one of the most common disorders of patients with chronic stroke, which hugely affects the ability to carry out the activities of daily living and the quality of life. Recently, traditional rehabilitation techniques have been associated with non-invasive brain stimulation (NIBS) techniques, which enhance brain plasticity, with the aim of promoting recovery in patients with chronic stroke. NIBS effectiveness in improving gait parameters in patients with chronic stroke has been in several studies evaluated. Robotic devices are emerging as promising tools for the treatment of stroke-related disabilities by performing repetitive, intensive, and task-specific treatments and have been proved to be effective for the enhancement of motor recovery in patients with chronic stroke. To date, several studies have examined the combination of NIBS with robotic-assisted gait training, but the effectiveness of this approach is not yet well established. The main purpose of this systematic review is to clarify whether the combination of NIBS and robot-assisted gait training may improve walking function in patients with chronic stroke. Our systematic review was conducted according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Studies eligible for review were identified through PubMed/MEDLINE, Embase, Scopus, and PEDro from inception to March 15, 2021, and the outcomes considered were gait assessments. Seven studies were included in the qualitative analysis of this systematic review, with a total population of 186 patients with chronic stroke. All studies specified technical characteristics of robotic devices and NIBS used, with high heterogeneity of protocols. Methodological studies have shown a significantly greater improvement in walking capacity recorded with 6MWT. Finally, research studies have highlighted a positive effect on walking recovery by combination of robot-assisted gait training with non-invasive brain stimulation. Furthermore, future studies should identify the best characteristics of the combined therapeutic protocols.

Transcranial direct current stimulation combined with trunk-targeted, proprioceptive neuromuscular facilitation in subacute stroke: a randomized controlled trial

Background

Stroke is the foremost cause of death and disability worldwide. Improving upper extremity function and quality of life are two paramount therapeutic targets during rehabilitation.

Aim of the study

To investigate the effects of transcranial direct current stimulation (tDCS) combined with trunk-targeted proprioceptive neuromuscular facilitation (PNF) on impairments, activity limitations, and participation restrictions of subjects with subacute stroke.

Methodology

Fifty-four subjects with subacute stroke were divided into three groups using block randomization. All three groups received rehabilitation sessions lasting 90 min in duration, four times per week, for 6 weeks. Group 1 (n = 18) received conventional physical therapy (CPT); group 2 (n = 18) received CPT, trunk-targeted PNF, and sham tDCS; and group 3 (n = 18) received CPT, trunk-targeted PNF, and bihemispheric motor cortex stimulation with tDCS. Changes in motor impairment, motor activity, and health-related quality of life assessments were outcome measures.

Results

A two-way linear mixed model analysis revealed interaction effects (group × time) for all outcome measurements (Trunk Impairment Scale, Fugl-Meyer Assessment of Motor Recovery after stroke upper extremity subsection, Wolf Motor Function Test, 10-Meter Walk Test, and the Stroke-Specific Quality of Life scale; all p < 0.01 or lower). Overall, post-pre mean differences demonstrate more substantial improvement in the active tDCS group, followed by sham stimulation associated with the PNF group and the group that received CPT alone.

Conclusion

Trunk-targeted PNF combined with bihemispheric tDCS along with CPT engender larger improvements in upper extremity and trunk impairment, upper limb function, gait speed, and quality of life in the subacute stroke population.

Effectiveness of transcranial direct current stimulation on hand dexterity in stroke patients: a protocol for a systematic review and meta-analysis

INTRODUCTION

Hand dexterity is the ability to execute the skilful movements using the hand and fingers. It is commonly impaired poststroke resulting in a profound deterioration in the quality of life for patients with stroke. Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation, which has gained a popularity as an adjunct therapy in recovering motor dysfunction poststroke. Promising results have been gained from applying tDCS in combination with motor rehabilitation, however, the outcome of tDCS on the upper limb motor function poststroke has been varied. Different results are potentially related to the discrepancy of the area of brain stimulation. Therefore, we aim to enhance the application of tDCS to improve its effectiveness in recovering hand dexterity through testing our hypothesis that stimulating the primary motor cortex could improve fine dexterity more than gross dexterity.

METHODS AND ANALYSIS

This protocol has been reported according to Preferred Reporting Items for Systematic Review and Meta-Analyses Protocols guidelines. CENTRAL, MEDLINE, EMBASE, SCOPUS, Web of Science and CINAHL databases will be searched with no restriction in language and publication date. The selected studies will be randomised controlled trial investigating the effect of tDCS alone or in combination with motor rehabilitation in improving hand dexterity of patients with stroke with upper limb hemiparesis. The outcomes of interest are fine and gross hand dexterity measures. Two independent reviewers will assess the eligibility of the study, extract data and appraise the methodological quality. The data will be pooled in a meta-analysis if applicable or interpreted narratively. Grading of Recommendations, Assessment, Development and Evaluation approach will be used to assess the overall quality of evidence for the fine and gross dexterity measures.

ETHICS AND DISSEMINATION

Ethical approval is not required for this study. The dissemination plan is to publish the results in a peer-review journal and presenting results in a conference.

PROSPERO REGISTRATION NUMBER

CRD42021262186.

Review of tDCS Configurations for Stimulation of the Lower-Limb Area of Motor Cortex and Cerebellum

This article presents an exhaustive analysis of the works present in the literature pertaining to transcranial direct current stimulation(tDCS) applications. The aim of this work is to analyze the specific characteristics of lower-limb stimulation, identifying the strengths and weaknesses of these works and framing them with the current knowledge of tDCS. The ultimate goal of this work is to propose areas of improvement to create more effective stimulation therapies with less variability.

Feasibility of Cerebellar Transcranial Direct Current Stimulation to Facilitate Goal-Directed Weight Shifting in Chronic Post-Stroke Hemiplegics

Neurological disorder such as stroke can adversely affect one's weight-bearing symmetry leading to dysfunctional postural control. Recovery after stroke is facilitated through functionally-relevant neuroplastic modulation. Functionally-relevant cerebellum coordinates voluntary movements. Specifically, the dentate nuclei and lower limb representations (lobules VII-IX) of the cerebellum are involved in error-correction, crucial for postural control. It is postulated that cerebellar transcranial direct current stimulation (ctDCS) of the dentate nuclei and lobules VII-IX can modulate postural control in chronic stroke survivors. The objectives of this work were to (1) present a refined Virtual Reality (VR)-based balance training platform (VBaT) that can measure Center of Pressure (CoP) and (2) carry out a study to understand the implication of ctDCS stimulating the dentate nuclei (Phase_D) and lobules VII-IX (Phase_L) on the postural control of chronic stroke patients when they interacted with VBaT. Also, we investigated whether hemiplegic patients (with intact cerebellum) having Basal Ganglia (BG) infarction had any differential abilities to correct postural sway from those with no BG infarction (while shifting weight to the Affected side). Results of a single-session single-blind crossover study on randomized Phase_D and Phase_L stimulation (with an intermediate resting state bipolar bilateral ctDCS) on 12 chronic hemiplegic patients on separate days indicated differentiated findings (post stimulation) on CoP-related indices. We observed an incremental effect on one's postural control during Phase_D and inhibitory effect on the dentate nuclei during Phase_L. Clustering analysis showed that those with BG infarction demonstrated poor postural control and deficit in error correction ability irrespective of the ctDCS Phase.

Transcranial Direct Current Stimulation (tDCS) for major depression - Interim analysis of cloud supervised technical data from the DepressionDC trial

BACKGROUND

Transcranial direct current stimulation (tDCS) of prefrontal cortex regions has been reported to exert antidepressant effects, though large scale multicenter trials in major depressive disorder (MDD) supporting this notion are still lacking. Application of tDCS in multicenter settings, however, requires measurement, storage and evaluation of technical parameters of tDCS sessions not only for safety reasons but also for quality control. To address this issue, we conducted an interim analysis of supervised technical data across study centers in order to monitor technical quality of tDCS in an ongoing multicenter RCT in MDD (DepressionDC trial).

METHODS

Technical data of 818 active tDCS sessions were recorded, stored in a data cloud, and analysed without violating study blinding. Impedance, voltage and current were monitored continuously with one data point recorded every second of stimulation.

RESULTS

Variability of impedance was considerable (1,42 kΩ, to 8,23 kΩ), inter-individually and even more intra-individually, but did not significantly differ between the study centre in Munich and all other sites.

CONCLUSION

Measurement, centralized data storage via data cloud and remote supervision of technical parameters of tDCS are feasible and proposed for future RCTs on therapeutic tDCS in multiple settings.

The Long-Term Maintenance of Upper Limb Motor Improvements Following Transcranial Direct Current Stimulation Combined with Rehabilitation in People with Stroke: A Systematic Review of Randomized Sham-Controlled Trials

Background: The effectiveness of transcranial direct current stimulation (tDCS) in the upper limb (UL) motor rehabilitation of stroke has been widely studied. However, the long-term maintenance of its improvements has not yet been proven. Methods: A systematic search was conducted in MEDLINE/Pubmed, Web of Science, PEDRo, and Scopus databases from inception to April 2021. Randomized controlled trials were included if they performed a tDCS intervention combined with UL rehabilitation in stroke patients, performed several sessions (five or more), and assessed long-term results (at least three-month follow-up). Risk of bias and methodological quality were evaluated with the Cochrane RoB-2 and the Oxford quality scoring system. Results: Nine studies were included, showing a high methodological quality. Findings regarding UL were categorized into (1) functionality, (2) strength, (3) spasticity. All the studies that showed significant improvements retained them in the long term. Baseline functionality may be a limiting factor in achieving motor improvements, but not in sustaining them over the long term. Conclusion: It seems that the improvements achieved during the application of tDCS combined with UL motor rehabilitation in stroke were preserved until the follow-up time (from 3 months to 1 year). Further studies are needed to clarify the long-term effects of tDCS.

Effectiveness of a combined transcranial direct current stimulation and virtual reality-based intervention on upper limb function in chronic individuals post-stroke with persistent severe hemiparesis: a randomized controlled trial

BACKGROUND

Functional impairments derived from the non-use of severely affected upper limb after stroke have been proposed to be mitigated by action observation and imagination-based techniques, whose effectiveness is enhanced when combined with transcranial direct current stimulation (tDCS). Preliminary studies in mildly impaired individuals in the acute phase post-stroke show intensified effects when action is facilitated by tDCS and mediated by virtual reality (VR) but the effectiveness in cases of severe impairment and chronic stroke is unknown. This study investigated the effectiveness of a combined tDCS and VR-based intervention in the sensorimotor function of chronic individuals post-stroke with persistent severe hemiparesis compared to conventional physical therapy.

METHODS

Twenty-nine participants were randomized into an experimental group, who received 30 minutes of the combined tDCS and VR-based therapy and 30 minutes of conventional physical therapy, or a control group, who exclusively received conventional physical therapy focusing on passive and active assistive range of motion exercises. The sensorimotor function of all participants was assessed before and after 25 one-hour sessions, administered three to five times a week, using the upper extremity subscale of the Fugl-Meyer Assessment, the time and ability subscales of the Wolf Motor Function Test, and the Nottingham Sensory Assessment.

RESULTS

A clinically meaningful improvement of the upper limb motor function was consistently revealed in all motor measures after the experimental intervention, but not after conventional physical therapy. Similar limited effects were detected in the sensory function in both groups.

CONCLUSION

The combined tDCS and VR-based paradigm provided not only greater but also clinically meaningful improvement in the motor function (and similar sensory effects) in comparison to conventional physical therapy.

The effects of transcranial direct current stimulation on upper-limb function post-stroke: A meta-analysis of multiple-session studies

OBJECTIVE

To systematically review how patient characteristics and/or transcranial direct current stimulation (tDCS) parameters influence tDCS effectiveness in respect to upper limb function post-stroke.

METHODS

Three electronic databases were searched for sham-controlled randomised trials using the Fugl-Meyer Assessment for upper extremity as outcome measure. A meta-analysis and nine subgroup-analyses were performed to identify which tDCS parameters yielded the greatest impact on upper limb function recovery in stroke patients.

RESULTS

Eighteen high-quality studies (507 patients) were included. tDCS applied in a chronic stage yields greater results than tDCS applied in a (sub)acute stage. Additionally, patients with low baseline upper limb impairments seem to benefit more from tDCS than those with high baseline impairments. Regarding tDCS configuration, all stimulation types led to a significant improvement, but only tDCS applied during therapy, and not before therapy, yielded significant results. A positive dose-response relationship was identified for current/charge density and stimulation duration, but not for number of sessions.

CONCLUSION

Our results demonstrate that tDCS improves upper limb function post-stroke. However, its effectiveness depends on numerous factors. Especially chronic stroke patients improved, which is promising as they are typically least amenable to recovery.

SIGNIFICANCE

The current work highlights the importance of several patient-related and protocol-related factors regarding tDCS effectiveness.

Motor network connectivity predicts neuroplastic response following theta burst stimulation in healthy adults

A patterned repetitive transcranial magnetic stimulation protocol, known as continuous theta burst stimulation (cTBS), can suppress corticospinal excitability via mechanisms that appear similar to long-term depression synaptic plasticity. Despite much potential, this technique is currently limited by substantial response variability. The purpose of this study was to investigate whether baseline resting state functional connectivity is a determinant of response to cTBS. Eighteen healthy young adults participated in up to three experimental sessions. Single-pulse transcranial magnetic stimulation was used to quantify change in corticospinal excitability following cTBS. Three minutes of resting electroencephalographic activity was recorded, and functional connectivity was estimated using the debiased weighted phase lag index across different frequency bands. Partial least squares regression identified models of connectivity between a seed region (C3) and the whole scalp that maximally accounted for variance in cTBS responses. There was no group-level effect of a single cTBS train or spaced cTBS trains on corticospinal excitability (p = 0.092). A low beta frequency band model of connectivity accounted for the largest proportion of variance in spaced cTBS response (R² = 0.50). Based on the low beta frequency model, a-priori regions of interest were identified and predicted 39% of variance in response to spaced cTBS at a subsequent session. Importantly, weaker connectivity between the seed electrode (C3) and a cluster approximating a frontocentral region was associated with greater spaced cTBS response (p = 0.02). It appears M1-frontocentral networks may have an important role in determining the effects of cTBS on corticospinal excitability.

Evidence-Based Guidelines and Secondary Meta-Analysis for the Use of Transcranial Direct Current Stimulation in Neurological and Psychiatric Disorders

BACKGROUND

Transcranial direct current stimulation has shown promising clinical results, leading to increased demand for an evidence-based review on its clinical effects.

OBJECTIVE

We convened a team of transcranial direct current stimulation experts to conduct a systematic review of clinical trials with more than 1 session of stimulation testing: pain, Parkinson's disease motor function and cognition, stroke motor function and language, epilepsy, major depressive disorder, obsessive compulsive disorder, Tourette syndrome, schizophrenia, and drug addiction.

METHODS

Experts were asked to conduct this systematic review according to the search methodology from PRISMA guidelines. Recommendations on efficacy were categorized into Levels A (definitely effective), B (probably effective), C (possibly effective), or no recommendation. We assessed risk of bias for all included studies to confirm whether results were driven by potentially biased studies.

RESULTS

Although most of the clinical trials have been designed as proof-of-concept trials, some of the indications analyzed in this review can be considered as definitely effective (Level A), such as depression, and probably effective (Level B), such as neuropathic pain, fibromyalgia, migraine, post-operative patient-controlled analgesia and pain, Parkinson's disease (motor and cognition), stroke (motor), epilepsy, schizophrenia, and alcohol addiction. Assessment of bias showed that most of the studies had low risk of biases, and sensitivity analysis for bias did not change these results. Effect sizes vary from 0.01 to 0.70 and were significant in about 8 conditions, with the largest effect size being in postoperative acute pain and smaller in stroke motor recovery (nonsignificant when combined with robotic therapy).

CONCLUSION

All recommendations listed here are based on current published PubMed-indexed data. Despite high levels of evidence in some conditions, it must be underscored that effect sizes and duration of effects are often limited; thus, real clinical impact needs to be further determined with different study designs.

Does Cathodal vs. Sham Transcranial Direct Current Stimulation Over Contralesional Motor Cortex Enhance Upper Limb Motor Recovery Post-stroke? A Systematic Review and Meta-analysis

Background: During recovery from stroke, the contralesional motor cortex (M1) may undergo maladaptive changes that contribute to impaired interhemispheric inhibition (IHI). Transcranial direct current stimulation (tDCS) with the cathode over contralesional M1 may inhibit this maladaptive plasticity, normalize IHI, and enhance motor recovery.

Objective: The objective of this systematic review and meta-analysis was to evaluate available evidence to determine whether cathodal tDCS on contralesional M1 enhances motor re-learning or recovery post-stroke more than sham tDCS.

Methods: We searched OVID Medline, Embase, and the Cochrane Central Register of Controlled Trials for participants with stroke (>1 week post-onset) with motor impairment and who received cathodal or sham tDCS to contralesional M1 for one or more sessions. The outcomes included a change in any clinically validated assessment of physical function, activity, or participation, or a change in a movement performance variable (e.g., time, accuracy). A meta-analysis was performed by pooling five randomized controlled trials (RCTs) and comparing the change in Fugl–Meyer upper extremity scores between cathodal and sham tDCS groups.

Results: Eleven studies met the inclusion criteria. Qualitatively, four out of five cross-over design studies and three out of six RCTs reported a significant effect of cathodal vs. sham tDCS. In the quantitative synthesis, cathodal tDCS (n = 65) did not significantly reduce motor impairment compared to sham tDCS (n = 67; standardized mean difference = 0.33, z = 1.79, p = 0.07) with a little observed heterogeneity (I² = 5%).

Conclusions: The effects of cathodal tDCS to contralesional M1 on motor recovery are small and consistent. There may be sub-populations that may respond to this approach; however, further research with larger cohorts is required.

Effects of Transcranial Direct Current Stimulation Combined with Physiotherapy on Gait Pattern, Balance, and Functionality in Stroke Patients. A Systematic Review

Background: The effectiveness of transcranial direct current stimulation (tDCS) together with conventional physiotherapy in motor rehabilitation after stroke has been widely studied. Despite this, few studies have focused on its application in gait and balance rehabilitation. This review aimed to determine the efficacy of transcranial direct current stimulation combined with conventional physiotherapy on gait, balance, and the functionality of the lower limb after stroke. Methods: This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Four electronic databases were systematically searched for relevant articles. Randomized clinical trials in English or Spanish that evaluated the use of the transcranial direct current stimulation, combined with physiotherapy, to improve gait, balance, and lower limb functionality after stroke were included. Main results: 10 articles were included, with a total of 222 subjects. Data about population, assessment tools, protocols, sessions, and results were extracted. The methodological quality of the included studies ranged between 3 and 5. Conclusion: The use of transcranial direct current stimulation combined with physiotherapy improves gait parameters, static and dynamic balance, and lower limb functionality in stroke patients. Long-term effects have not yet been demonstrated.

Corticospinal excitability enhancement with simultaneous transcranial near-infrared stimulation and anodal direct current stimulation of motor cortex

OBJECTIVES

Non-invasive brain stimulation (NIBS) is beneficial to many neurological and psychiatric disorders by modulating neuroplasticity and cortical excitability. However, recent studies evidence that single type of NIBS such as transcranial direct current stimulation (tDCS) does not have meaningful clinical therapeutic responses due to their small effect size. Transcranial near-infrared stimulation (tNIRS) is a novel form of NIBS. Both tNIRS and tDCS implement its therapeutic effects by modulating cortical excitability but with different mechanisms. We hypothesized that simultaneous tNIRS and tDCS is superior to single stimulation, leading to a greater cortical excitability.

METHODS

Sixteen healthy subjects participated in a double-blind, sham-controlled, cross-over designed study. Motor evoked potentials (MEPs) were used to measure motor cortex excitability. The changes of MEP were calculated and compared in the sham condition, tDCS stimulation condition, tNIRS condition and the simultaneous tNIRS and anodal tDCS condition.

RESULTS

tDCS alone and tNIRS alone both elicited higher MEP after stimulation, while the MEP amplitude in the simultaneous tNIRS and tDCS condition was significantly higher than either tNIRS alone or tDCS alone. The enhancement lasted up to at least 30 minutes after stimulation, indicating simultaneous 820 nm tNIRS with 2 mA anodal tDCS have a synergistic effect on cortical plasticity.

CONCLUSIONS

Simultaneous application of tNIRS with tDCS produces a stronger cortical excitability effect.

SIGNIFICANCE

The simultaneous tNIRS and tDCS is a promising technology with exciting potential as a means of treatment, neuro-enhancement, or neuro-protection.

Reliability, sensitivity, and predictive value of fMRI during multiple object tracking as a marker of cognitive training gain in combination with tDCS in stroke survivors

Computerized cognitive training (CCT) combined with transcranial direct current stimulation (tDCS) has showed some promise in alleviating cognitive impairments in patients with brain disorders, but the robustness and possible mechanisms are unclear. In this prospective double-blind randomized clinical trial, we investigated the feasibility and effectiveness of combining CCT and tDCS, and tested the predictive value of and training-related changes in fMRI-based brain activation during attentive performance (multiple object tracking) obtained at inclusion, before initiating training, and after the three-weeks intervention in chronic stroke patients (>6 months since hospital admission). Patients were randomized to one of two groups, receiving CCT and either (a) tDCS targeting left dorsolateral prefrontal cortex (1 mA), or (b) sham tDCS, with 40s active stimulation (1 mA) before fade out of the current. Of note, 77 patients were enrolled in the study, 54 completed the cognitive training, and 48 completed all training and MRI sessions. We found significant improvement in performance across all trained tasks, but no additional gain of tDCS. fMRI-based brain activation showed high reliability, and higher cognitive performance was associated with increased tracking-related activation in the dorsal attention network and default mode network as well as anterior cingulate after compared to before the intervention. We found no significant associations between cognitive gain and brain activation measured before training or in the difference in activation after intervention. Combined, these results show significant training effects on trained cognitive tasks in stroke survivors, with no clear evidence of additional gain of concurrent tDCS.

Effects of home-based dual-hemispheric transcranial direct current stimulation combined with exercise on upper and lower limb motor performance in patients with chronic stroke

PURPOSE

This study aimed to determine the effects of home-based dual-hemispheric transcranial direct current stimulation (dual-tDCS) combined with exercise on motor performance in patients with chronic stroke.

MATERIALS AND METHODS

We allocated 24 participants to the active or sham group. They completed 1-h home-based exercise after 20-min dual-tDCS at 2-mA, thrice a week for 4 weeks. The patients were assessed using the Fugl-Meyer Assessment (FMA), Wolf Motor Function Test, Timed Up and Go test, Five Times Sit-to-Stand Test, Six-meter Walk Test, and muscle strength assessment.

RESULTS

Compared with the sham group, the active group showed improved FMA scores, which were sustained for at least 1 month. There was no between-group difference in the outcomes of the functional tasks.

CONCLUSION

Home-based dual-tDCS could facilitate motor recovery in patients with chronic stroke with its effect lasting for at least 1 month. However, its effects on functional tasks remain unclear. tDCS is safe and easy for home-based self-administration for patients who can use their paretic arms. This could benefit patients without access to health care centres or in situations requiring physical distancing. This home-based tDCS combined with exercise has the potential to be incorporated into telemedicine in stroke rehabilitation.IMPLICATIONS FOR REHABILITATIONTwelve sessions of home-based dual-tDCS combined with exercises (3 days/week for 4 weeks) facilitated upper and lower limb motor recovery in patients with chronic stroke compared with exercise alone, with a post-effect for at least 1 month.Home-based tDCS could be safe and easily self-administrable by patients who can use their paretic arms.This intervention could be beneficial for patients living in the community without easy access to a health care centre or in situations where physical distancing is required.

From adults to pediatrics: A review noninvasive brain stimulation (NIBS) to facilitate recovery from brain injury

Stroke is a major problem worldwide that impacts over 100 million adults and children annually. Rehabilitation therapy is the current standard of care to restore functional impairments post-stroke, however its effects are limited and many patients suffer persisting functional impairments and life-long disability. Noninvasive Brain Stimulation (NIBS) has emerged as a potential rehabilitation treatment option in both adults and children with brain injury. In the last decade, Transcranial Magnetic Stimulation (TMS), Transcranial Direct Current Stimulation (tDCS) and Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) have been investigated to improve motor recovery in adults post-stroke. These promising adult findings using NIBS, however, have yet to be widely translated to the area of pediatrics. The limited studies exploring NIBS in children have demonstrated safety, feasibility, and utility of stimulation-augmented rehabilitation. This chapter will describe the mechanism of NIBS therapy (cortical excitability, neuroplasticity) that underlies its use in stroke and motor function and how TMS, tDCS, and taVNS are applied in adult stroke treatment paradigms. We will then discuss the current state of NIBS in early pediatric brain injury and will provide insight regarding practical considerations and future applications of NIBS in pediatrics to make this promising treatment option a viable therapy in children.

Electrophysiological signatures of resting state networks predict cognitive deficits in stroke

Localized damage to different brain regions can cause specific cognitive deficits. However, stroke lesions can also induce modifications in the functional connectivity of intrinsic brain networks, which could be responsible for the behavioral impairment. Though resting state networks (RSNs) are typically mapped using fMRI, it has been recently shown that they can also be detected from high-density EEG. We build on a state-of-the-art approach to extract RSNs from 64-channels EEG activity in a group of right stroke patients and to identify neural predictors of their cognitive performance. Fourteen RSNs previously found in fMRI and high-density EEG studies on healthy participants were successfully reconstructed from our patients' EEG recordings. We then correlated EEG-RSNs functional connectivity with neuropsychological scores, first considering a wide frequency band (1-80 Hz) and then specific frequency ranges in order to examine the association between each EEG rhythm and the behavioral impairment. We found that visuo-spatial and motor impairments were primarily associated with the dorsal attention network, with contribution dependent on the specific EEG band. These findings are in line with the hypothesis that there is a core system of brain networks involved in specific cognitive domains. Moreover, our results pave the way for low-cost EEG-based monitoring of intrinsic brain networks' functioning in neurological patients to complement clinical-behavioral measures.

[Transcranial direct current stimulation in neurology and psychiatry]

Transcranial direct current stimulation (tDCS) is a non-invasive method of modulating brain excitability by low intensity direct current. At present, there are numerous studies of tDCS application in various mental and neurological diseases. In this review, the data of tDCS efficiency in the treatment of different disorders are presented and the recommendations on using this method in clinical practice are given.

Feasibility and Safety of Transcranial Direct Current Stimulation in an Outpatient Rehabilitation Setting After Stroke

Transcranial direct current stimulation (tDCS) has strong potential for outpatient clinical use, but feasibility and safety of tDCS has only been evaluated in laboratory and inpatient clinical settings. The objective of this study was to assess feasibility and safety of tDCS for stroke in an outpatient clinical setting. Individuals with stroke in outpatient therapy received tDCS during physical therapy sessions. Feasibility was assessed with screening, enrollment, withdrawal, and adherence numbers, tDCS impressions, and perceived benefits and detriments of tDCS. Acute changes in fatigue and self-reported function and pre-post changes in fatigue were also assessed. Safety was assessed as adverse events and side effects. In total, 85 individuals were screened, and 10 were enrolled. Most exclusions were unrelated to clinical feasibility. In total, 3 participants withdrew, so 7 participants completed 2 sessions/week for 5–6 weeks with 100% adherence. In total, 71% reported positive impressions of tDCS. tDCS setup decreased to 5–7 min at end of study. There was one adverse event unrelated to tDCS. Mild to moderate side effects (tingling, itching, pinching, and fatigue) were experienced. In total, 86% of participants recounted benefits of tDCS. There were acute improvements in function and energy. Results support the feasibility and safety of tDCS in an outpatient clinical setting.

Validation of Numerical Simulation for Transcranial Direct Current Stimulation with Spherical Phantom

Transcranial direct current stimulation (tDCS) is a promising brain modulation technique in clinical application. Computational models of brain current flow have been used to provide better insights into determining the stimulation parameters, but there are only a few studies to validate the numerical simulation model. The purpose of this study is to validate the simulation model of tDCS. A one-/three-layered spherical phantom model was constructed to mimic the human head. The tDCS-induced voltages were measured at different depth in the spherical phantom model with stereotactic-EEG (s-EEG) electrodes. Comparing the measured values with the simulation data from the computational models, we found that the computational and empirically measured electric field distributions on the brain surface is similar and that the deviation between the predicted and measured electric field value becomes larger near the electrode.

Electrical Stimulation of the Motor Cortex or Paretic Muscles Improves Strength Production in Stroke Patients: A Systematic Review and Meta-Analysis

OBJECTIVE

Transcranial direct current stimulation (tDCS) and functional electrical stimulation (FES) are two widely applied methods of electrical stimulation for motor recovery among stroke patients. This systematic review and meta-analysis investigated the efficacy of tDCS and FES for strength production in stroke patients. TYPE: Systematic review.

LITERATURE SURVEY

Studies that explored the effects of tDCS or FES on the strength production of paralyzed muscles in stroke patients were retrieved on a comprehensive set of three databases: (1) Google Scholar, (2) PubMed, and (3) the Cochrane Database of Systematic Reviews until July 2019.

METHODOLOGY

Systematic study retrieval led to the inclusion of 15 studies that reported on strength production effects after tDCS and FES interventions among stoke patients. A sham control group and randomization were used in each study. The 15 studies included 20 comparisons with sham controls, 7 of which involved tDCS and 13 of which involved FES.

SYNTHESIS

Random-effects models showed that strength production was improved after tDCS (effect size [ES] = 0.52, 95% confidence interval [CI] = 0.35-0.69, P < .001, Z = 6.05) and FES (ES = 0.47, 95% CI = 0.16-0.78, P < .003, Z = 2.99). Additionally, tDCS was shown to improve strength production in the acute (ES = 0.52, 95% CI = 0.24-0.80, P < .001, Z = 3.65), subacute (ES = 0.85, 95% CI = 0.37-1.32, P < .001, Z = 3.51), but not chronic (ES = 0.06, 95% CI = -0.47-0.60, P = .82, Z = 0.23) phases of stroke recovery. Out of the 13 studies involving FES, 12 investigated strength production in the chronic phase and one investigated in the acute phase, showing a positive effect in these two stages.

CONCLUSIONS

The results of the meta-analysis showed that tDCS and FES successfully improved strength production in stroke patients.

Does neuromodulation transcranial direct current stimulation (tDCS) associated with peripheral stimulation through exercise to walk have an impact on falls in people with Parkinson's disease?

Parkinson's disease (PD) is one of the most prevalent neurodegenerative diseases in the world, with a high degree of disability. Among the various therapeutic possibilities, brain stimulation appears in a promising approach, with deep brain stimulation (DBS) being the best described and successful, yet it has the limitation of being invasive. In this context we present transcranial direct current stimulation (tDCS), a non-invasive treatment that brings a new perspective when thinking about treatment of neurological diseases. It is easy to handle, low cost, few side effects and good adherence to patients. TDCS presents good evidence for clinical practice, but when it comes to PD the results obtained are inconclusive and some protocols have not yet been tested. In this hypothesis we propose that the use of tDCS applied in the supplemental motor areas, together with a gait training, can facilitate the motor learning and modulate the neurons for better potentiation of the exercises together with patients with walking difficulties due to PD.

Evaluating the effects of tDCS in stroke patients using functional outcomes: a systematic review

Background and purpose: Transcranial direct current stimulation (tDCS) has been extensively studied over the past 20 years to promote functional motor recovery after stroke. However, tDCS clinical relevance still needs to be determined. The present systematic review aims to determine whether tDCS applied to the primary motor cortex (M1) in stroke patients can have a positive effect on functional motor outcomes.Materials and methods: Two databases (Medline & Scopus) were searched for randomized, double-blinded, sham-controlled trials pertaining to the use of M1 tDCS on cerebral stroke patients, and its effects on validated functional motor outcomes. When data were provided, effect sizes were calculated. PROSPERO registration number: CRD42018108157Results: 46 studies (n = 1291 patients) met inclusion criteria. Overall study quality was good (7.69/10 on the PEDro scale). Over half (56.5%) the studies were on chronic stroke patients. There seemed to be a certain pattern of recurring parameters, but tDCS protocols still remain heterogeneous. Overall results were positive (71.7% of studies found that tDCS has positive results on functional motor outcomes). Effect-sizes ranged from 0 to 1.33. No severe adverse events were reported.Conclusion: Despite heterogeneous stimulation parameters, outcomes and patient demographics, tDCS seems to be complementary to classical and novel rehabilitation approaches. With minimal adverse effects (if screening parameters are respected), none of which were serious, and a high potential to improve recovery when using optimal parameters (i.e.: 20 min of stimulation, at 2 mA with 25 or 35cm² electrodes that are regularly humidified), tDCS could potentially be ready for clinical applications.Implications for RehabilitationtDCS could potentially be ready for clinical application.Evidence of very low to very high quality is available on the effectiveness of tDCS to improve motor control following stroke.This should with caution be focused on the primary motor cortex.

Anodal occipital tDCS enhances spontaneous alpha activity

Transcranial direct current stimulation (tDCS) is a form of brain stimulation technique that modulates neuronal excitability changes in targeted cerebral areas through a constant low current. The existing studies mainly concentrated in tDCS effects on motor cortex. The number of tDCS studies targeting visual area is sparse. And parameters of tDCS on the visual cortex are not well optimized yet. Therefore, this study explored the effect of anodal occipital tDCS in eyes-open resting state to disclose possible modulation to spontaneous brain activity by electroencephalography (EEG). Fifteen healthy subjects were involved in this study. Each subject endured sham and anodal tDCS in turn. 2 mA tDCS was applied over 21 min with Oz-Cz montage. Amplitudes of spontaneous brain activities were evaluated for each experimental condition. Compared with pre-stimulation and sham tDCS, anodal tDCS caused an obvious increment in parieto-occipital alpha activity. These results demonstrated electrophysiological changes in EEG oscillations induced by anodal occipital tDCS, and would help to improve the understanding of modulation of tDCS-induced visual cortex excitability changes in humans.

Maximizing the Treatment Benefit of tDCS in Neurodegenerative Anomia

We evaluated whether transcranial direct current stimulation (tDCS) in two different montages could improve picture naming abilities in participants with anomic Alzheimer Disease or Frontotemporal dementia.

Different Therapeutic Effects of Transcranial Direct Current Stimulation on Upper and Lower Limb Recovery of Stroke Patients with Motor Dysfunction: A Meta-Analysis

Objective

To explore the effects of transcranial direct current stimulation (tDCS) on the motor recovery of stroke patients and the effect differences between the upper limb and lower limb.

Methods

Randomized control trials published until January 2019 were searched from PubMed, Embase, ScienceDirect, and Cochrane Library databases. The standardized mean difference (SMD) with 95% confidence interval (CI) was estimated separately for upper and lower limb motor outcomes to understand the mean effect size.

Results

Twenty-nine studies with 664 subjects were included in this meta-analysis. The overall analyses of tDCS demonstrated significant effect size both for the upper limb (SMD = 0.26, P = 0.002) and the lower limb (SMD = 0.47, P = 0.002). Compared with acute and subacute stroke patients, chronic stroke patients obtained significant effects after tDCS (SMD = 0.25, P = 0.03) in upper limb function. Furthermore, both anode and cathode stimulations produced significant effect size for stroke patients after ≤10 sessions of tDCS (anode: SMD = 0.40, P = 0.001; cathode: SMD = 0.79, P < 0.0001) with >0.029 mA/cm² of density (anode: SMD = 0.46, P = 0.002; cathode: SMD = 0.79, P < 0.0001). But for lower limb function, more prominent effects were found in subacute stroke patients (SMD = 0.56, P = 0.001) with bilateral tDCS (SMD = 0.59, p = 0.009).

Conclusion

tDCS is effective for the recovery of stroke patients with motor dysfunction. In addition, upper limb and lower limb functions obtain distinct effects from different therapeutic parameters of tDCS at different stages, respectively.

Transcranial direct current stimulation associated with physical-therapy in acute stroke patients - A randomized, triple blind, sham-controlled study

BACKGROUND

Transcranial Direct Current Stimulation has been increasing in popularity in the last few years. Despite vast amounts of articles on the use of tDCS on stroke patients, very little has been done during the acute phase.

OBJECTIVES

Measure the effects of tDCS on functional and sensory outcomes throughout the first year post onset of stroke.

METHODS

50 acute stroke patients were randomized and placed into either the treatment or sham group. Anodal tDCS was applied (2 mA, 20 min) 5 times a week during the first month post stroke. Patients were evaluated with the Wolf Motor Function Test, the Semmes Weinstein Monofilament Test, the Upper Extremity section (UEFM), the Lower Extremity section (LEFM) and the Somatosensory section of the Fugl Meyer Test, the Tardieu Spasticity Scale, the Stroke Impact Scale (SIS), the Hospital Anxiety and Depression Scale (HADS) and the Barthel Index. Evaluations were held at 48 h post stroke, week 1, 2, 3, 4, 3 months, 6 months and 1 year.

RESULTS

There were statistically and clinically significant improvements after tDCS in all functional motor outcomes, and somatosensory functions. Differences between both groups for the main outcome (WMFT time) were 51% (p = 0.04) at one month, and 57% (p = 0.02) at one year.

CONCLUSION

tDCS seems to be an effective adjuvant to conventional rehabilitation techniques. If applied in the acute stages of stroke, functional recovery is not only accelerated, but improved, and results are maintained up to one-year post stroke.