Long term at-home treatment with transcranial direct current stimulation (tDCS) improves symptoms of cerebellar ataxia: a case report

Clinical neurophysiology in the treatment of movement disorders: IFCN handbook chapter

In this review, different aspects of the use of clinical neurophysiology techniques for the treatment of movement disorders are addressed. First of all, these techniques can be used to guide neuromodulation techniques or to perform therapeutic neuromodulation as such. Neuromodulation includes invasive techniques based on the surgical implantation of electrodes and a pulse generator, such as deep brain stimulation (DBS) or spinal cord stimulation (SCS) on the one hand, and non-invasive techniques aimed at modulating or even lesioning neural structures by transcranial application. Movement disorders are one of the main areas of indication for the various neuromodulation techniques. This review focuses on the following techniques: DBS, repetitive transcranial magnetic stimulation (rTMS), low-intensity transcranial electrical stimulation, including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), and focused ultrasound (FUS), including high-intensity magnetic resonance-guided FUS (MRgFUS), and pulsed mode low-intensity transcranial FUS stimulation (TUS). The main clinical conditions in which neuromodulation has proven its efficacy are Parkinson's disease, dystonia, and essential tremor, mainly using DBS or MRgFUS. There is also some evidence for Tourette syndrome (DBS), Huntington's disease (DBS), cerebellar ataxia (tDCS), and axial signs (SCS) and depression (rTMS) in PD. The development of non-invasive transcranial neuromodulation techniques is limited by the short-term clinical impact of these techniques, especially rTMS, in the context of very chronic diseases. However, at-home use (tDCS) or current advances in the design of closed-loop stimulation (tACS) may open new perspectives for the application of these techniques in patients, favored by their easier use and lower rate of adverse effects compared to invasive or lesioning methods. Finally, this review summarizes the evidence for keeping the use of electromyography to optimize the identification of muscles to be treated with botulinum toxin injection, which is indicated and widely performed for the treatment of various movement disorders.

Posture enhancement with cerebellum transcranial electrical stimulation: a systematic review of current methods and findings

Recently, transcranial electrical stimulation (tES) has gained increasing popularity among researchers, especially for recovery and improvement, but interpretation of these results is difficult due to variations in study methods and outcome measurements. The main goal of this study was to better understand the postural and balance indicators affected by cerebellar tES, as the cerebellum is the main brain region responsible for controlling balance. For this systematic literature review, three databases were searched for articles where the cerebellum was stimulated by any type of tES in either healthy participants or those with neurologic disorders. Postural, dynamic, and/or static stability measurements were recorded, and risk of bias was assessed on the PEDro scale. A total of 21 studies were included in the analysis. 17 studies reported improvements after application of tES. 14 studies stimulated the cerebellum unilaterally and 15 used this modality for 20 min. Moreover, all studies exclusively used transcranial direct current as the type of stimulation. Evaluation of PEDro results showed that studies included in the analysis utilized good methodology. Although there were some inconsistencies in study results, overall, it was demonstrated that tES can improve balance and postural index under both healthy and neurological conditions. Further research of bilateral cerebellar stimulation or the use of transcranial alternating current stimulation, transcranial random noise stimulation, and transcranial pulsed current stimulation is needed for a more comprehensive assessment of the potential positive effects of cerebellar tES on the balance system.

Neurorestorative effects of cerebellar transcranial direct current stimulation on social prediction of adolescents and young adults with congenital cerebellar malformations

BACKGROUND

Converging evidence points to impairments of the predictive function exerted by the cerebellum as one of the causes of the social cognition deficits observed in patients with cerebellar disorders.

OBJECTIVE

We tested the neurorestorative effects of cerebellar transcranial direct current stimulation (ctDCS) on the use of contextual expectations to interpret actions occurring in ambiguous sensory sceneries in a sample of adolescents and young adults with congenital, non-progressive cerebellar malformation (CM).

METHODS

We administered an action prediction task in which, in an implicit-learning phase, the probability of co-occurrence between actions and contextual elements was manipulated to form either strongly or moderately informative expectations. Subsequently, in a testing phase, we probed the use of these contextual expectations for predicting ambiguous (i.e., temporally occluded) actions. In a sham-controlled, within-subject design, participants received anodic or sham ctDCS during the task.

RESULTS

Anodic ctDCS, compared to sham, improved patients' ability to use contextual expectations to predict the unfolding of actions embedded in moderately, but not strongly, informative contexts.

CONCLUSIONS

These findings corroborate the role of the cerebellum in using previously learned contextual associations to predict social events and document the efficacy of ctDCS to boost social prediction in patients with congenital cerebellar malformation. The study encourages the further exploration of ctDCS as a neurorestorative tool for the neurorehabilitation of social cognition abilities in neurological, neuropsychiatric, and neurodevelopmental disorders featured by macro- or micro-structural alterations of the cerebellum.

Non-invasive brain stimulation for patients and healthy subjects: Current challenges and future perspectives

Non-invasive brain stimulation (NIBS) techniques have a rich historical background, yet their utilization has witnessed significant growth only recently. These techniques encompass transcranial electrical stimulation and transcranial magnetic stimulation, which were initially employed in neuroscience to explore the intricate relationship between the brain and behaviour. However, they are increasingly finding application in research contexts as a means to address various neurological, psychiatric, and neurodegenerative disorders. This article aims to fulfill two primary objectives. Firstly, it seeks to showcase the current state of the art in the clinical application of NIBS, highlighting how it can improve and complement existing treatments. Secondly, it provides a comprehensive overview of the utilization of NIBS in augmenting the brain function of healthy individuals, thereby enhancing their performance. Furthermore, the article delves into the points of convergence and divergence between these two techniques. It also addresses the existing challenges and future prospects associated with NIBS from ethical and research standpoints.

Transcranial direct current stimulation as treatment for major depression in a home treatment setting (HomeDC trial): study protocol and methodology of a double-blind, placebo-controlled pilot study

INTRODUCTION

Transcranial direct current stimulation (tDCS) of prefrontal cortex regions has been reported to exert therapeutic effects in patients with major depressive disorder (MDD). Due to its beneficial safety profile, its easy mode of application, and its cost-effectiveness, tDCS has recently been proposed for treatment at home. This would offer new chances for regionally widespread and long-term application. However, tDCS at home must meet the new methodological challenges of handling and adherence. At the same time, data from randomized controlled trials (RCT) investigating this mode of application are still lacking. In this pilot RCT, we therefore investigate the feasibility, safety, and effectiveness of a new antidepressant tDCS application set-up.

METHODS AND ANALYSIS

The HomeDC trial will be conducted as a double-blind, placebo-controlled, parallel-group design trial. Thirty-two study participants with MDD will be randomly assigned to active or sham tDCS groups. Participants will self-administer prefrontal tDCS for 6 weeks. Active tDCS will be conducted with anode over F3, cathode over F4, for 5 sessions/week, with a duration of 30 min/day, and 2 mA stimulation intensity. Sham tDCS, conversely, follows an identical protocol in regard to electrode montage and timing, but with no electric stimulation between the ramp-in and ramp-out periods. Both conditions will be administered either as a monotherapy or an adjunctive treatment to a stable dose of antidepressant medication. Adjunctive magnetic resonance imaging (MRI) and electric field (E-field) modelling will be conducted at baseline. Primary outcome is feasibility based on successfully completed stimulations and drop-out rates. The intervention is considered feasible when 20 out of 30 sessions have been fully conducted by at least 75% of the participants. Effectiveness and safety will be assessed as secondary outcomes.

DISCUSSION

In the HomeDC trial, the technical requirements for a placebo-controlled tDCS study in a home-based treatment setting have been established. The trial addresses the crucial points of the home-based tDCS treatment approach: uniform electrode positioning, frequent monitoring of stimulation parameters, adherence, and ensuring an appropriate home treatment environment. This study will further identify constraints and drawbacks of this novel mode of treatment.

TRIAL REGISTRATION

www.

CLINICALTRIALS

gov .

TRIAL REGISTRATION NUMBER

NCT05172505. Registration date: 12/13/2021.

Assessment and tailored physical rehabilitation approaches in persons with cerebellar impairments targeting mobility and walking according to the International Classification of Functioning: a systematic review of case-reports and case-series

PURPOSE

Cerebellar impairment (CI) manifests from different etiologies resulting in a heterogenic clinical presentation affecting walking and mobility. Case-reports were reviewed to provide an analytical clinical picture of persons with CI (PwCI) to differentiate cerebellar and non-cerebellar impairments and to identify interventions and assessments used to quantify impact on walking and mobility according to the International Classification of Functioning, Disability and Health (ICF).

MATERIALS AND METHODS

Literature was searched in PubMed, Web Of Science and Scopus. Case-reports conducting physical rehabilitation and reporting at least one outcome measure of ataxia, gait pattern, walking or mobility were included.

RESULTS

28 articles with a total of 38 different patients were included. Etiologies were clustered to: spinocerebellar degenerations, traumatic brain injuries, cerebellar tumors, stroke and miscellaneous. The interventions applied were activity-based, including gait and balance training. Participation based activities such as tai chi, climbing and dance-based therapy had positive outcomes on mobility. Outcomes on body function such as ataxia and gait pattern were only reported in 22% of the patients.

CONCLUSIONS

A comprehensive test battery to encompass the key features of a PwCI on different levels of the ICF is needed to manage heterogeneity. Measures on body function level should be included in interventions.

The Therapeutic Potential of Non-Invasive and Invasive Cerebellar Stimulation Techniques in Hereditary Ataxias

The degenerative ataxias comprise a heterogeneous group of inherited and acquired disorders that are characterized by a progressive cerebellar syndrome, frequently in combination with one or more extracerebellar signs. Specific disease-modifying interventions are currently not available for many of these rare conditions, which underscores the necessity of finding effective symptomatic therapies. During the past five to ten years, an increasing number of randomized controlled trials have been conducted examining the potential of different non-invasive brain stimulation techniques to induce symptomatic improvement. In addition, a few smaller studies have explored deep brain stimulation (DBS) of the dentate nucleus as an invasive means to directly modulate cerebellar output, thereby aiming to alleviate ataxia severity. In this paper, we comprehensively review the clinical and neurophysiological effects of transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), and dentate nucleus DBS in patients with hereditary ataxias, as well as the presumed underlying mechanisms at the cellular and network level and perspectives for future research.

Personalized, Multisession, Multichannel Transcranial Direct Current Stimulation in Medication-Refractory Focal Epilepsy: An Open-Label Study

PURPOSE

Animal and proof-of-principle human studies suggest that cathodal transcranial direct current stimulation may suppress seizures in drug-resistant focal epilepsy. The present study tests the safety, tolerability, and effect size of repeated daily cathodal transcranial direct current stimulation in epilepsy have not been established, limiting development of clinically meaningful interventions.

METHODS

We conducted a 2-center, open-label study on 20 participants with medically refractory, focal epilepsy, aged 9 to 56 years (11 women and 9 children younger than18 years). Each participant underwent 10 sessions of 20 minutes of cathodal transcranial direct current stimulation over 2 weeks. Multielectrode montages were designed using a realistic head model-driven approach to conduct an inhibitory electric field to the target cortical seizure foci and surrounding cortex to suppress excitability and reduce seizure rates. Patients recorded daily seizures using a seizure diary 8 weeks prior, 2 weeks during, and 8 to 12 weeks after the stimulation period.

RESULTS

The median seizure reduction was 44% relative to baseline and did not differ between adult and pediatric patients. Three patients experienced an increase in seizure frequency of >50% during the stimulation period; in one, a 36% increase in seizure frequency persisted through 12 weeks of follow-up. Otherwise, participants experienced only minor adverse events-the most common being scalp discomfort during transcranial direct current stimulation.

CONCLUSIONS

This pilot study supports the safety and efficacy of multifocal, personalized, multichannel, cathodal transcranial direct current stimulation for adult and pediatric patients with medication-refractory focal epilepsy, although identifies a possibility of seizure exacerbation in some. The data also provide insight into the effect size to inform the design of a randomized, sham-stimulation controlled trial.

Transcranial direct current stimulation for balance rehabilitation in neurological disorders: A systematic review and meta-analysis

Postural instability is common in neurological diseases. Although transcranial direct current stimulation (tDCS) seems to be a promising complementary therapy, emerging evidence indicates mixed results and protocols' characteristics. We conducted a systematic review and meta-analysis on PubMed, EMBASE, Scopus, and Web of Science to synthesize key findings of the effectiveness of single and multiple sessions of tDCS alone and combined with other interventions on balance in adults with neurological disorders. Thirty-seven studies were included in the systematic review and 33 in the meta-analysis. The reviewed studies did not personalize the stimulation protocol to individual needs/characteristics. A random-effects meta-analysis indicated that tDCS alone (SMD = -0.44; 95%CI = -0.69/-0.19; p < 0.001) and combined with another intervention (SMD = -0.31; 95%CI = -0.51/-0.11; p = 0.002) improved balance in adults with neurological disorders (small to moderate effect sizes). Balance improvements were evidenced regardless of the number of sessions and targeted area. In summary, tDCS is a promising therapy for balance rehabilitation in adults with neurological disorders. However, further clinical trials should identify factors that influence responsiveness to tDCS for a more tailored approach, which may optimize the clinical use of tDCS.

Repeated long sessions of transcranial direct current stimulation reduces seizure frequency in patients with refractory focal epilepsy: An open-label extension study

OBJECTIVE

Although clinical trials have demonstrated that cathodal transcranial direct current stimulation (tDCS) is effective for seizure reduction, its long-term efficacy is unknown. This study aimed to determine the long-term effects of repeated cathodal long tDCS sessions on seizure suppression in patients with refractory epilepsy.

METHODS

Patients were recruited to participate in an extended phase of a previous randomized, double-blind, sham-controlled, three-arm, parallel, multicenter study on tDCS. The patients were divided into an active tDCS group (20 min of tDCS per day) and an intensified tDCS group (2 × 20 min of tDCS per day). Each tDCS session lasted 2 weeks and the patients underwent repeated sessions at intervals of 2 to 6 months. The cathode was placed over the epileptogenic focus with the current intensity set as 2 mA. Seizure frequency reduction from baseline was analyzed using the Wilcoxon signed-rank test for two related samples. A generalized estimating equation model was used to estimate group, time, and interaction effects.

RESULTS

Among the 19 patients who participated in the extended phase, 11 were in the active tDCS group and underwent 2-16 active tDCS sessions, and eight were in the intensified tDCS group and underwent 3-11 intensified tDCS sessions. Seizure reduction was significant from the first to the seventh follow-up, with a median seizure frequency reduction of 41.7%-83.3% (p < 0.05). Compared to the regular tDCS protocol, each intensified tDCS session substantially decreased seizure frequency by 0.3680 (p < 0.05). One patient experienced an increase of 8.5%-232.8% in the total number of seizures during three treatment sessions and follow-ups.

CONCLUSION

Repeated long cathodal tDCS sessions yielded significant and progressive long-term seizure reductions in patients with refractory focal epilepsy.

Potential of Transcranial Direct Current Stimulation in Alzheimer's Disease: Optimizing Trials Toward Clinical Use

Transcranial direct current stimulation (tDCS) is a safe and well-tolerated noninvasive method for stimulating the brain that is rapidly developing into a treatment method for various neurological and psychiatric conditions. In particular, there is growing evidence of a therapeutic role for tDCS in ameliorating or delaying the cognitive decline in Alzheimer's disease (AD). We provide a brief overview of the current development and application status of tDCS as a nonpharmacological therapeutic method for AD and mild cognitive impairment (MCI), summarize the levels of evidence, and identify the improvements needed for clinical applications. We also suggest future directions for large-scale controlled clinical trials of tDCS in AD and MCI, and emphasize the necessity of identifying the mechanistic targets to facilitate clinical applications.

Cerebellar transcranial direct current stimulation modulates timing but not acquisition of conditioned eyeblink responses in SCA3 patients

BACKGROUND

Delay eyeblink conditioning is an extensively studied motor learning paradigm that critically depends on the integrity of the cerebellum. In healthy individuals, modulation of cerebellar excitability using transcranial direct current stimulation (tDCS) has been reported to alter the acquisition and/or timing of conditioned eyeblink responses (CRs). It remains unknown whether such effects can also be elicited in patients with cerebellar disorders.

OBJECTIVE

To investigate if repeated sessions of cerebellar tDCS modify acquisition and/or timing of CRs in patients with spinocerebellar ataxia type 3 (SCA3) and to evaluate possible associations between disease severity measures and eyeblink conditioning parameters.

METHODS

Delay eyeblink conditioning was examined in 20 mildly to moderately affected individuals with SCA3 and 31 healthy controls. After the baseline session, patients were randomly assigned to receive ten sessions of cerebellar anodal tDCS or sham tDCS (i.e., five days per week for two consecutive weeks). Patients and investigators were blinded to treatment allocation. The same eyeblink conditioning protocol was administered directly after the last tDCS session. The Scale for the Assessment and Rating of Ataxia (SARA), cerebellar cognitive affective syndrome scale (CCAS-S), and disease duration were used as clinical measures of disease severity.

RESULTS

At baseline, SCA3 patients exhibited significantly fewer CRs than healthy controls. Acquisition was inversely associated with the number of failed CCAS-S test items but not with SARA score. Onset and peak latencies of CRs were longer in SCA3 patients and correlated with disease duration. Repeated sessions of cerebellar anodal tDCS did not affect CR acquisition, but had a significant treatment effect on both timing parameters. While a shift of CRs toward the conditioned stimulus was observed in the sham group (i.e., timing became more similar to that of healthy controls, presumably reflecting the effect of a second eyeblink conditioning session), anodal tDCS induced a shift of CRs in the opposite direction (i.e., toward the unconditioned stimulus).

CONCLUSION

Our findings provide the first evidence that cerebellar tDCS is capable of modifying cerebellar function in SCA3 patients. Future studies should assess whether this intervention similarly modulates temporal processing in other degenerative ataxias.

Transcranial Direct Current Stimulation (tDCS) as a Useful Rehabilitation Strategy to Improve Cognition in Patients With Alzheimer's Disease and Parkinson's Disease: An Updated Systematic Review of Randomized Controlled Trials

Alzheimer's disease (AD) and Parkinson's disease (PD) are neurodegenerative disorders characterized by cognitive impairment and functional decline increasing with disease progression. Within non-pharmacological interventions, transcranial direct current stimulation (tDCS) might represent a cost-effective rehabilitation strategy to implement cognitive abilities with positive implications for functional autonomy and quality-of-life of patients. Our systematic review aimed at evaluating the effects of tDCS upon cognition in people suffering from AD and PD. We searched for randomized controlled trials (RCTs) into PubMed, Web of Science, and Cochrane Library. Three review authors extracted data of interest, with neuropsychological tests or experimental cognitive tasks scores as outcome measures. A total of 17 RCTs (10 trials for AD and 7 trials for PD) were included. Compared with sham stimulation, tDCS may improve global cognition and recognition memory in patients with AD and also some executive functions (i.e., divided attention, verbal fluency, and reduction of sensitivity to interference) in patients with PD. Criticism remains about benefits for the other investigated cognitive domains. Despite preliminary emerging evidences, larger RCTs with common neuropsychological measures and long-term follow-ups establishing longevity of the observed effects are necessary for future research in applied psychology field, alongside improved clinical guidelines on the neurodegenerative disorders pertaining electrodes montage, sessions number, duration and intensity of the stimulation, and cognitive battery to be used.

Cerebellar tDCS as Therapy for Cerebellar Ataxias

In recent years, a growing body of literature has investigated the use of non-invasive brain stimulation (NIBS) techniques to influence cerebellar activity and the effects of cerebellar stimulation on other brain regions through its multiple complex projections. From the early 1990s, with the discovery of the so-called cerebellar inhibition (CBI), several studies have focused their attention on the use of cerebellar NIBS as treatment for different motor disorders. Cerebellar ataxias (CAs) represent the prototypical clinical manifestation of cerebellar alterations, but other movement disorders, such as Parkinson's disease, essential tremor, and dystonia have also been associated with alterations of networks which include the cerebellum, or of the cerebellum itself. Cerebellar transcranial direct current stimulation (ctDCS) could indeed represent an economical, non-invasive therapeutic tool with minimal side effects, thus improving the clinical management of patients and their quality of life. Studies show that ctDCS is effective as a therapeutic option for motor symptoms in patients with CAs, and especially in those with less severe forms, suggesting that ctDCS efficacy could result from augmented neuronal compensation, which itself relies on preserved cerebellar volume. Evidence for the efficacy of ctDCS is less conclusive for the other aforementioned motor disorders, although preliminary results are promising. Future studies should adopt more rigorous methods (e.g., larger sample sizes, double blinding, better characterization of the sample, reliable biomarkers), in order to allow the scientific community to derive higher-quality evidence on the efficacy of ctDCS as a therapeutic option for motor disorders.

Consensus Paper: Novel Directions and Next Steps of Non-invasive Brain Stimulation of the Cerebellum in Health and Disease

The cerebellum is involved in multiple closed-loops circuitry which connect the cerebellar modules with the motor cortex, prefrontal, temporal, and parietal cortical areas, and contribute to motor control, cognitive processes, emotional processing, and behavior. Among them, the cerebello-thalamo-cortical pathway represents the anatomical substratum of cerebellum-motor cortex inhibition (CBI). However, the cerebellum is also connected with basal ganglia by disynaptic pathways, and cerebellar involvement in disorders commonly associated with basal ganglia dysfunction (e.g., Parkinson's disease and dystonia) has been suggested. Lately, cerebellar activity has been targeted by non-invasive brain stimulation (NIBS) techniques including transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) to indirectly affect and tune dysfunctional circuitry in the brain. Although the results are promising, several questions remain still unsolved. Here, a panel of experts from different specialties (neurophysiology, neurology, neurosurgery, neuropsychology) reviews the current results on cerebellar NIBS with the aim to derive the future steps and directions needed. We discuss the effects of TMS in the field of cerebellar neurophysiology, the potentials of cerebellar tDCS, the role of animal models in cerebellar NIBS applications, and the possible application of cerebellar NIBS in motor learning, stroke recovery, speech and language functions, neuropsychiatric and movement disorders.

Effects of Anodal Cerebellar Transcranial Direct Current Stimulation on Movements in Patients with Cerebellar Ataxias: A Systematic Review

Cerebellar transcranial direct current stimulation (cerebellar tDCS) is a promising therapy for cerebellar ataxias and has attracted increasing attention from researchers and clinicians. A timely systematic review focusing on randomized sham-controlled trials and repeated measures studies is warranted. This study was to systematically review existing evidence regarding effects of anodal cerebellar tDCS on movements in patients with cerebellar ataxias. The searched databases included Web of Science, MEDLINE, PsycINFO, CINAHL, EMBASE, Cochrane Library, and EBSCOhost. Methodological quality of the selected studies was assessed using the Physiotherapy Evidence Database scale. Five studies with 86 patients were identified. Among these, four studies showed positive effects of anodal cerebellar tDCS. Specifically, anodal cerebellar tDCS decreased disease severity and improved finger dexterity and quality of life in patients, but showed incongruent effects on gait control and balance, which may be due to heterogeneity of research participants and choices of measures. The protocols of anodal cerebellar tDCS that improved movements in patients commonly placed the anode over the whole cerebellum and provided ten 2-mA 20-min stimulation sessions. The results may show preliminary evidence that anodal cerebellar tDCS is beneficial to reducing disease severity and improving finger dexterity and quality of life in patients, which lays the groundwork for future studies further examining responses in the cerebello-thalamo-cortical pathway. An increase in sample size, the use of homogeneous patient groups, exploration of the optimal stimulation protocol, and investigation of detailed neural mechanisms are clearly needed in future studies.

A Novel Highly Durable Carbon/Silver/Silver Chloride Composite Electrode for High-Definition Transcranial Direct Current Stimulation

High-definition transcranial direct current stimulation (HD-tDCS) is a promising non-invasive neuromodulation technique, which has been widely used in the clinical intervention and treatment of neurological or psychiatric disorders. Sintered Ag/AgCl electrode has become a preferred candidate for HD-tDCS, but its service life is very short, especially for long-term anodal stimulation. To address this issue, a novel highly durable conductive carbon/silver/silver chloride composite (C/Ag/AgCl) electrode was fabricated by a facile cold rolling method. The important parameters were systematically optimized, including the conductive enhancer, the particle size of Ag powder, the C:Ag:PTFE ratio, the saline concentration, and the active substance loading. The CNT/Ag/AgCl-721 electrode demonstrated excellent specific capacity and cycling performance. Both constant current anodal polarization and simulated tDCS measurement demonstrated that the service life of the CNT/Ag/AgCl-721 electrodes was 15-16 times of that of sintered Ag/AgCl electrodes. The much longer service life can be attributed to the formation of the three-dimensional interpenetrating conductive network with CNT doping, which can maintain a good conductivity and cycling performance even if excessive non-conductive AgCl is accumulated on the surface during long-term anodal stimulation. Considering their low cost, long service life, and good skin tolerance, the proposed CNT/Ag/AgCl electrodes have shown promising application prospects in HD-tDCS, especially for daily life scenarios.

Cerebellar Transcranial Direct Current Stimulation in Children with Developmental Coordination Disorder: A Randomized, Double-Blind, Sham-Controlled Pilot Study

Evidence-based therapeutic options for children with developmental coordination disorder (DCD) are scarce. This work explored the effects of cerebellar anodal transcranial direct current stimulation (atDCS) on three 48 h-apart motor sequence learning and upper limb coordination sessions in children with DCD. The results revealed that, as compared to a Sham intervention (n = 10), cerebellar atDCS (n = 10) did not meaningfully improve execution speed but tended to reduce the number of execution errors during motor sequence learning. However, cerebellar atDCS did neither meaningfully influence offline learning nor upper limb coordination, suggesting that atDCS’ effects are circumscribed to its application duration. These results suggest that cerebellar atDCS could have beneficial effects as a complementary therapeutic tool for children with DCD.

A narrative review on non-invasive stimulation of the cerebellum in neurological diseases

IMPORTANCE

The cerebellum plays an important role in motor, cognitive, and affective functions owing to its dense interconnections with basal ganglia and cerebral cortex. This review aimed at summarizing the non-invasive cerebellar stimulation (NICS) approaches used to modulate cerebellar output and treat cerebellar dysfunction in the motor domain.

OBSERVATION

The utility of NICS in the treatment of cerebellar and non-cerebellar neurological diseases (including Parkinson's disease, dementia, cerebellar ataxia, and stroke) is discussed. NICS induces meaningful clinical effects from repeated sessions alone in both cerebellar and non-cerebellar diseases. However, there are no conclusive data on this issue and several concerns need to be still addressed before NICS could be considered a valuable, standard therapeutic tool.

CONCLUSIONS AND RELEVANCE

Even though some challenges must be overcome to adopt NICS in a wider clinical setting, this tool might become a useful strategy to help patients with lesions in the cerebellum and cerebral areas that are connected with the cerebellum whether one could enhance cerebellar activity with the intention of facilitating the cerebellum and the entire, related network, rather than attempting to facilitate a partially damaged cortical region or inhibiting the homologs' contralateral area. The different outcome of each approach would depend on the residual functional reserve of the cerebellum, which is confirmed as a critical element to be probed preliminary in order to define the best patient-tailored NICS.

Effects of Transcranial Direct Current Stimulation Treatment for Anorexia Nervosa

Background: Anorexia nervosa (AN) is a life-threatening illness with poor treatment outcomes. Although transcranial direct current stimulation (tDCS) is a promising non-invasive brain stimulation method, its effect in patients with AN remains unclear. Objective: This study investigated changes in maladaptive eating behavior, body mass index (BMI), and depression after 10 sessions of anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC). Methods: In this double-blind, randomized controlled trial, 43 inpatients with AN were divided to receive either active (n = 22) or sham (n = 21) tDCS over the left DLPFC (anode F3/cathode Fp2, 2 mA for 30 min). All patients filled the Eating Disorder Examination Questionnaire (EDE-Q) and Zung Self-Rating Depression Scale (ZUNG), and their BMI was measured. These values were obtained repeatedly in four stages: (1) before tDCS treatment, (2) after tDCS treatment, (3) in the follow-up after 2 weeks, and (4) in the follow-up after 4 weeks. Results: Primary outcomes (EDE-Q) based on the ANOVA results do not show any between-group differences either after the active part of the study or in the follow-up. Secondary analysis reveals a reduction in some items of EDE-Q. Compared with sham tDCS, active tDCS significantly improved self-evaluation based on body shape (p < 0.05) and significantly decreased the need of excessive control over calorie intake (p < 0.05) in the 4-week follow-up. However, the results do not survive multiple comparison correction. In both sham and active groups, the BMI values improved, albeit not significantly. Conclusion: We did not observe a significant effect of tDCS over the left DLPFC on complex psychopathology and weight recovery in patients with AN. tDCS reduced the need to follow specific dietary rules and improved body image evaluation in patients with AN. Tests with a larger sample and different positions of electrodes are needed. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03273205.

Transcranial direct current stimulation: A review of electrode characteristics and materials

Electrode characteristics are crucial in transcranial direct current stimulation (tDCS) since electrode design and placement determine the cortical area being modulated, current density and spatial resolution of stimulation. Early research on tDCS sought to determine optimal parameters for stimulation by specifying maximum current, duration and sizes of electrodes. Further research focused on determining efficient ways to deliver stimulation to targeted regions on the cortex with minimal discomfort to the user by altering electrode size, placement, shape and material. This review aims to give an insight on the main characteristics of electrodes used in tDCS and on the variability found in electrode parameters and placements from tDCS to high definition tDCS (HD-tDCS) applications and beyond.

Guidelines for TMS/tES clinical services and research through the COVID-19 pandemic

BACKGROUND

The COVID-19 pandemic has broadly disrupted biomedical treatment and research including non-invasive brain stimulation (NIBS). Moreover, the rapid onset of societal disruption and evolving regulatory restrictions may not have allowed for systematic planning of how clinical and research work may continue throughout the pandemic or be restarted as restrictions are abated. The urgency to provide and develop NIBS as an intervention for diverse neurological and mental health indications, and as a catalyst of fundamental brain research, is not dampened by the parallel efforts to address the most life-threatening aspects of COVID-19; rather in many cases the need for NIBS is heightened including the potential to mitigate mental health consequences related to COVID-19.

OBJECTIVE

To facilitate the re-establishment of access to NIBS clinical services and research operations during the current COVID-19 pandemic and possible future outbreaks, we develop and discuss a framework for balancing the importance of NIBS operations with safety considerations, while addressing the needs of all stakeholders. We focus on Transcranial Magnetic Stimulation (TMS) and low intensity transcranial Electrical Stimulation (tES) - including transcranial Direct Current Stimulation (tDCS) and transcranial Alternating Current Stimulation (tACS).

METHODS

The present consensus paper provides guidelines and good practices for managing and reopening NIBS clinics and laboratories through the immediate and ongoing stages of COVID-19. The document reflects the analysis of experts with domain-relevant expertise spanning NIBS technology, clinical services, and basic and clinical research - with an international perspective. We outline regulatory aspects, human resources, NIBS optimization, as well as accommodations for specific demographics.

RESULTS

A model based on three phases (early COVID-19 impact, current practices, and future preparation) with an 11-step checklist (spanning removing or streamlining in-person protocols, incorporating telemedicine, and addressing COVID-19-associated adverse events) is proposed. Recommendations on implementing social distancing and sterilization of NIBS related equipment, specific considerations of COVID-19 positive populations including mental health comorbidities, as well as considerations regarding regulatory and human resource in the era of COVID-19 are outlined. We discuss COVID-19 considerations specifically for clinical (sub-)populations including pediatric, stroke, addiction, and the elderly. Numerous case-examples across the world are described.

CONCLUSION

There is an evident, and in cases urgent, need to maintain NIBS operations through the COVID-19 pandemic, including anticipating future pandemic waves and addressing effects of COVID-19 on brain and mind. The proposed robust and structured strategy aims to address the current and anticipated future challenges while maintaining scientific rigor and managing risk.

Non-invasive Transcranial Electrical Stimulation in Movement Disorders

Dysfunction within large-scale brain networks as the basis for movement disorders is an accepted hypothesis. The treatment options for restoring network function are limited. Non-invasive brain stimulation techniques such as repetitive transcranial magnetic stimulation are now being studied to modify the network. Transcranial electrical stimulation (tES) is also a portable, cost-effective, and non-invasive way of network modulation. Transcranial direct current stimulation and transcranial alternating current stimulation have been studied in Parkinson’s disease, dystonia, tremor, and ataxia. Transcranial pulsed current stimulation and transcranial random noise stimulation are not yet studied enough. The literature in the use of these techniques is intriguing, yet many unanswered questions remain. In this review, we highlight the studies using these four potential tES techniques and their electrophysiological basis and consider the therapeutic implication in the field of movement disorders. The objectives are to consolidate the current literature, demonstrate that these methods are feasible, and encourage the application of such techniques in the near future.

Gait and Functional Mobility in Multiple Sclerosis: Immediate Effects of Transcranial Direct Current Stimulation (tDCS) Paired With Aerobic Exercise

Walking impairments are a debilitating feature of multiple sclerosis (MS) because of the direct interference with daily activity. The management of motor symptoms in those with MS remains a therapeutic challenge. Transcranial direct current stimulation (tDCS) is a type of non-invasive brain stimulation that is emerging as a promising rehabilitative tool but requires further characterization to determine its optimal therapeutic use. In this randomized, sham-controlled proof-of-concept study, we tested the immediate effects of a single tDCS session on walking and functional mobility in those with MS. Seventeen participants with MS completed one 20-min session of aerobic exercise, randomly assigned to be paired with either active (2.5 mA, n = 9) or sham (n = 8) tDCS over the primary motor cortex (M1). The groups (active vs. sham) were matched according to gender (50% vs. 60% F), age (52.1 ± 12.85 vs. 54.2 ± 8.5 years), and level of neurological disability (median Expanded Disability Status Scale score 5.5 vs. 5). Gait speed on the 10-m walk test and the Timed Up and Go (TUG) time were measured by a wearable inertial sensor immediately before and following the 20-min session, with changes compared between conditions and time. There were no significant differences in gait speed or TUG time changes following the session in the full sample or between the active vs. sham groups. These findings suggest that a single session of anodal tDCS over M1 is not sufficient to affect walking and functional mobility in those with MS. Instead, behavioral motor response of tDCS is likely to be cumulative, and the effects of multiple tDCS sessions require further study.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT03658668.

Non-Invasive Cerebellar Stimulation in Neurodegenerative Ataxia: A Literature Review

Cerebellar ataxias are a heterogenous group of degenerative disorders for which we currently lack effective and disease-modifying interventions. The field of non-invasive brain stimulation has made much progress in the development of specific stimulation protocols to modulate cerebellar excitability and try to restore the physiological activity of the cerebellum in patients with ataxia. In light of limited evidence-based pharmacologic and non-pharmacologic treatment options for patients with ataxia, several different non-invasive brain stimulation protocols have emerged, particularly employing repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) techniques. In this review, we summarize the most relevant rTMS and tDCS therapeutic trials and discuss their implications in the care of patients with degenerative ataxias.

Cerebellar Transcranial Direct Current Stimulation in People with Parkinson's Disease: A Pilot Study

People with Parkinson’s disease (PwPD) often experience gait and balance problems that substantially impact their quality of life. Pharmacological, surgical, and rehabilitative treatments have limited effectiveness and many PwPD continue to experience gait and balance impairment. Transcranial direct current stimulation (tDCS) may represent a viable therapeutic adjunct. The effects of lower intensity tDCS (2 mA) over frontal brain areas, in unilateral and bilateral montages, has previously been explored; however, the effects of lower and higher intensity cerebellar tDCS (2 mA and 4 mA, respectively) on gait and balance has not been investigated. Seven PwPD underwent five cerebellar tDCS conditions (sham, unilateral 2 mA, bilateral 2 mA, unilateral 4 mA, and bilateral 4 mA) for 20 min. After a 10 min rest, gait and balance were tested. The results indicated that the bilateral 4 mA cerebellar tDCS condition had a significantly higher Berg Balance Scale score compared to sham. This study provides preliminary evidence that a single session of tDCS over the cerebellum, using a bilateral configuration at a higher intensity (4 mA), significantly improved balance performance. This intensity and cerebellar configuration warrants future investigation in larger samples and over repeated sessions.

Supervised transcranial direct current stimulation (tDCS) at home: A guide for clinical research and practice

BACKGROUND

Transcranial direct current stimulation (tDCS) is a method of noninvasive neuromodulation and potential therapeutic tool to improve functioning and relieve symptoms across a range of central and peripheral nervous system conditions. Evidence suggests that the effects of tDCS are cumulative with consecutive daily applications needed to achieve clinically meaningful effects. Therefore, there is growing interest in delivering tDCS away from the clinic or research facility, usually at home.

OBJECTIVE

To provide a comprehensive guide to operationalize safe and responsible use of tDCS in home settings for both investigative and clinical use.

METHODS

Providing treatment at home can improve access and compliance by decreasing the burden of time and travel for patients and their caregivers, as well as to reach those in remote locations and/or living with more advanced disabilities.

RESULTS

To date, methodological approaches for at-home tDCS delivery have varied. After implementing the first basic guidelines for at-home tDCS in clinical trials, this work describes a comprehensive guide for facilitating safe and responsible use of tDCS in home settings enabling access for repeated administration over time.

CONCLUSION

These guidelines provide a reference and standard for practice when employing the use of tDCS outside of the clinic setting.

The role of the cerebellum in degenerative ataxias and essential tremor: Insights from noninvasive modulation of cerebellar activity

Over the last three decades, measuring and modulating cerebellar activity and its connectivity with other brain regions has become an emerging research topic in clinical neuroscience. The most important connection is the cerebellothalamocortical pathway, which can be functionally interrogated using a paired‐pulse transcranial magnetic stimulation paradigm. Cerebellar brain inhibition reflects the magnitude of suppression of motor cortex excitability after stimulating the contralateral cerebellar hemisphere and therefore represents a neurophysiological marker of the integrity of the efferent cerebellar tract. Observations that cerebellar noninvasive stimulation techniques enhanced performance of certain motor and cognitive tasks in healthy individuals have inspired attempts to modulate cerebellar activity and connectivity in patients with cerebellar diseases in order to achieve clinical benefit. We here comprehensively explore the therapeutic potential of these techniques in two movement disorders characterized by prominent cerebellar involvement, namely the degenerative ataxias and essential tremor. The article aims to illustrate the (patho)physiological insights obtained from these studies and how these translate into clinical practice, where possible by addressing the association with cerebellar brain inhibition. Finally, possible explanations for some discordant interstudy findings, shortcomings in our current understanding, and recommendations for future research will be provided. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Adaptive current tDCS up to 4 mA

BACKGROUND

Higher tDCS current may putatively enhance efficacy, with tolerability the perceived limiting factor.

OBJECTIVE

We designed and validated electrodes and an adaptive controller to provide tDCS up to 4 mA, while managing tolerability. The adaptive 4 mA controller included incremental ramp up, impedance-based current limits, and a Relax-mode where current is transiently decreased. Relax-mode was automatically activated by self-report VAS-pain score >5 and in some conditions by a Relax-button available to participants.

METHODS

In a parallel-group participant-blind design with 50 healthy subjects, we used specialized electrodes to administer 3 daily session of tDCS for 11 min, with a lexical decision task as a distractor, in 5 study conditions: adaptive 4 mA, adaptive 4 mA with Relax-button, adaptive 4 mA with historical-Relax-button, 2 mA, and sham. A tablet-based stimulator with a participant interface regularly queried VAS pain score and also limited current based on impedance and tolerability. An Abort-button provided in all conditions stopped stimulation. In the adaptive 4 mA with Relax-button and adaptive 4 mA with historical-Relax-button conditions, participants could trigger a Relax-mode ad libitum, in the latter case with incrementally longer current reductions. Primary outcome was the average current delivered during each session, VAS pain score, and adverse event questionnaires. Current delivered was analyzed either excluding or including dropouts who activated Abort (scored as 0 current).

RESULTS

There were two dropouts each in the adaptive 4 mA and sham conditions. Resistance based current attenuation was rarely activated, with few automatic VAS pain score triggered relax-modes. In conditions with Relax-button option, there were significant activations often irrespective of VAS pain score. Including dropouts, current across conditions were significantly different from each other with maximum current delivered during adaptive 4 mA with Relax-button. Excluding dropouts, maximum current was delivered with adaptive 4 mA. VAS pain score and adverse events for the sham was only significantly lower than the adaptive 4 mA with Relax-button and adaptive 4 mA with historical-Relax-button. There was no difference in VAS pain score or adverse events between 2 mA and adaptive 4 mA.

CONCLUSIONS

Provided specific electrodes and controllers, adaptive 4 mA tDCS is tolerated and effectively blinded, with acceptability likely higher in a clinical population and absence of regular querying. Indeed, presenting participants with overt controls increases rumination on sensation.

Telerehabilitation benefits patients with multiple sclerosis in an urban setting

INTRODUCTION

People living with multiple sclerosis (MS) often require rehabilitation to manage their symptoms. Telerehabilitation offers improved access to treatment options by reducing travel time and cost. Our telerehabilitation program pairs training exercises simultaneously with transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique. In the current study, we characterized the benefits of our remotely supervised tDCS (RS-tDCS) at-home telerehabilitation protocol in an urban sample of MS participants.

METHODS

Participants with MS were recruited to complete a telerehabilitation trial using tDCS paired with cognitive rehabilitation at-home using remote supervision (RS-tDCS). Participant time and travel costs for study visits to our clinic in midtown New York City were calculated.

RESULTS

Forty-four patients with MS (aged 18 to 71) with mild to severe neurologic disability (Expanded Disability Status Scale score median = 3.5, range: 0.0 to 8.0) completed the survey. Round-trip clinic attendance required 2.3 ± 2.3 h and US $27.04 ± 38.13 for out-of-pocket expenses. Participants rated difficulty of clinic attendance as moderately to significantly difficult (2.5 ± 1.3). Severity of neurologic disability accounted for the greatest variance in difficulty attending clinic (30%, p < 0.001). RS-tDCS had 95% treatment compliance and 93% of participants reported satisfaction with the at-home treatment.

DISCUSSION

Attending clinic is associated with significant costs for patients with neurologic disorders, even in urban settings. Rehabilitation can be delivered at home and supervised in real-time via videoconference.

Cerebellar transcranial direct current stimulation in spinocerebellar ataxia type 3 (SCA3-tDCS): rationale and protocol of a randomized, double-blind, sham-controlled study

BACKGROUND

Spinocerebellar ataxia type 3 (SCA3) is the most common subtype among the autosomal dominant cerebellar ataxias, a group of neurodegenerative disorders for which currently no disease-specific therapy is available. Evidence-based options for symptomatic treatment of ataxia are also limited. Recent investigations in a heterogeneous group of hereditary and acquired ataxias showed promising, prolonged effects of a two-week course with daily sessions of cerebellar anodal transcranial direct current stimulation (tDCS) on ataxia severity, gait speed, and upper limb dexterity. The aim of the SCA3-tDCS study is to further examine whether tDCS improves ataxia severity and various (cerebellar) non-motor symptoms in a homogeneous cohort of SCA3 patients and to explore the time course of these effects.

METHODS/DESIGN

An investigator-initiated, double-blind, randomized, sham-controlled, single-center trial will be conducted. Twenty mildly to moderately affected SCA3 patients (Scale for the Assessment and Rating of Ataxia score between 3 and 20) will be included and randomly assigned in a 1:1 ratio to either cerebellar anodal tDCS or sham cerebellar tDCS. Patients, investigators, and outcome assessors are unaware of treatment allocation. Cerebellar tDCS (20 min, 2 mA, ramp-up and down periods of 30 s each) will be delivered over ten sessions, distributed in two groups of five consecutive days with a two-day break in between. Outcomes are assessed after a single session of tDCS, after the tenth stimulation (T1), and after three, six, and twelve months. The primary outcome measure is the absolute change of the SARA score between baseline and T1. In addition, effects on a variety of other motor and neuropsychological functions in which the cerebellum is known to be involved will be evaluated using quantitative motor tests, static posturography, neurophysiological measurements, cognitive assessment, and questionnaires.

DISCUSSION

The results of this study will inform us whether repeated sessions of cerebellar anodal tDCS benefit SCA3 patients and whether this form of non-invasive stimulation might be a novel therapeutic approach to consider in a neurorehabilitation setting. Combined with two earlier controlled trials, a positive effect of the SCA3-tDCS study will encourage implementation of this intervention and stimulate further research in other SCAs and heredodegenerative ataxias.

TRIAL REGISTRATION

NL7321 , registered October 8, 2018.