Brain Plasticity Effects of Neuromodulation Against Multiple Sclerosis Fatigue

Transcranial direct current stimulation (tDCS) in the treatment of neuropsychiatric symptoms of long COVID

The study aimed to assess the efficacy of transcranial direct current stimulation (tDCS) in the treatment of neuropsychiatric (NP) symptoms of the post-acute sequelae of SARS-CoV-2 infection (PASC), known as the long COVID. A double-blind, randomized, sham-controlled study compared the efficacy and safety of prefrontal cortex active tDCS to sham-tDCS in treating NP-PASC. Patients diagnosed with NP-PASC, with a Fatigue Impact Scale (FIS) score ≥ 40, were eligible for the study. Twenty tDCS sessions were administered within four weeks, with continuous, end-of-treatment, and follow-up measurements. The primary outcome was a change in the FIS at the end-of-treatment, analyzed in the intention-to-treat population. Data from 33 patients assigned to active (n = 16) or sham-tDCS (n = 17) were analyzed. After the treatment, a decrease in the FIS score was more pronounced in the sham than in the active group, yet the intergroup difference was insignificant (11.7 [95% CI -11.1 to 34.5], p = 0.6). Furthermore, no significant intergroup differences were observed regarding anxiety, depression, quality of life, and cognitive performance. The small cohort sample, differences in baseline FIS scores between groups (non-stratified randomization), or chosen stimulation parameters may have influenced our findings. However, it might also be possible that the expected mechanism of action of tDCS is insufficient to treat these conditions.

Transcranial direct current stimulation for fatigue in neurological conditions: A systematic scoping review

BACKGROUND AND PURPOSE

Fatigue following neurological conditions negatively impacts daily activities, reducing overall quality of life. Transcranial direct current stimulation (tDCS) for fatigue management is still underexplored. This scoping review explores its use in managing fatigue among various neurological conditions.

METHODS

A thorough literature search was carried out using PubMed, Scopus, CINAHL, Web of Science, Embase, ProQuest, and the Cochrane Library. Google Scholar and clinicaltrials.gov were manually searched for gray literature and ongoing trials, respectively. Regardless of the study design, all studies utilizing tDCS for the management of fatigue in various neurological conditions were considered. Two reviewers independently screened all the studies, following which the data were retrieved.

RESULTS

Studies employing tDCS for fatigue management across neurological conditions is as follows: Multiple sclerosis (MS) (n = 28, 66%), stroke (n = 5, 12%), Parkinson's disease (PD) (n = 4, 10%), post-polio syndrome (PPS) (n = 2, 5%), traumatic brain injury (TBI) (n = 2, 5%), and amyotrophic lateral sclerosis (n = 1, 2%). All the studies used anodal stimulation, with the common stimulation site being the left dorsolateral prefrontal cortex for MS, stroke, and PD. A stimulation intensity of 1.0-4.0 mA with a duration ranging from 15 to 30 min in 1 to 24 sessions were commonly reported. The Fatigue Severity Scale (n = 21) and Modified Fatigue Impact Scale (n = 17) were frequently implemented outcome measures. Regardless of the study design, 36/42 (85.7%) studies reported an improvement in fatigue scores in the tDCS group. The common adverse events noted were tingling (n = 8, 35%), headache (n = 6, 26%), and itching (n = 6, 26%).

DISCUSSION

Application of tDCS for fatigue was explored in individuals with stroke, PD, PPS, and TBI after MS. Even though a wide range of treatment parameters and outcome measures were adopted to assess and target fatigue, tDCS proves to have a promising role in alleviating this symptom.

Mechanisms of Post-Stroke Fatigue: A Follow-Up From the Third Stroke Recovery and Rehabilitation Roundtable

BACKGROUND

Post-stroke fatigue (PSF) is a significant and highly prevalent symptom, whose mechanisms are poorly understood. The third Stroke Recovery and Rehabilitation Roundtable paper on PSF focussed primarily on defining and measuring PSF while mechanisms were briefly discussed. This companion paper to the main paper is aimed at elaborating possible mechanisms of PSF.

METHODS

This paper reviews the available evidence that potentially explains the pathophysiology of PSF and draws parallels from fatigue literature in other conditions. We start by proposing a case for phenotyping PSF based on structural, functional, and behavioral characteristics of PSF. This is followed by discussion of a potentially significant role of early inflammation in the development of fatigue, specifically the impact of low-grade inflammation and its long-term systemic effects resulting in PSF. Of the many neurotransmitter systems in the brain, the dopaminergic systems have the most evidence for a role in PSF, along with a role in sensorimotor processing. Sensorimotor neural network dynamics are compromised as highlighted by evidence from both neurostimulation and neuromodulation studies. The double-edged sword effect of exercise on PSF provides further insight into how PSF might emerge and the importance of carefully titrating interventional paradigms.

CONCLUSION

The paper concludes by synthesizing the presented evidence into a unifying model of fatigue which distinguishes between factors that pre-dispose, precipitate, and perpetuate PSF. This framework will help guide new research into the biological mechanisms of PSF which is a necessary prerequisite for developing treatments to mitigate the debilitating effects of post-stroke fatigue.

Non-invasive brain stimulation on clinical symptoms in multiple sclerosis patients: A systematic review and meta-analysis

BACKGROUND

Non-invasive brain stimulation (NIBS) has demonstrated mixed effects on the clinical symptoms of multiple sclerosis. This systematic review and meta-analysis aimed to evaluate the effects of NIBS techniques on the most common symptoms of MS.

METHODS

A literature search was performed until October 2022 which included randomized controlled trials and quasi-experimental studies that used sham-controlled NIBS in patients with MS. We calculated the Hedge's effect sizes of each domain of interest and their 95% confidence intervals (95% CIs) and performed random effects meta-analyses.

RESULTS

A total of 49 studies were included in the systematic review (944 participants). Forty-four eligible studies were included for quantitative analysis, of which 33 applied transcranial direct current stimulation (tDCS), 9 transcranial magnetic stimulation (TMS), and 2 transcranial random noise stimulation (tRNS). We found a significant decrease in fatigue (ES:  - 0.86, 95% CI:  - 1.22 to - 0.51, p < 0.0001), pain (ES: - 1.91, 95% CI, - 3.64 to - 0.19, p=  0.03) and psychiatric symptoms (ES: - 1.44, 95% CI - 2.56 to - 0.32, p = 0.01) in favor of tDCS compared with the sham. On the other hand, there was no strong evidence showing tDCS effectiveness on motor performance and cognition (ES: - 0.03, 95% CI - 0.35 to 0.28, p = 0.83 and ES: 0.71, 95% CI, - 0.09 to 1.52, p = 0.08, respectively). Regarding TMS, we found a significant decrease in fatigue (ES: - 0.45, 95% CI: - 0.84 to -0.07, p = 0.02) and spasticity levels (ES: - 1.11, 95% CI: - 1.48 to - 0.75, p < 0.00001) compared to the sham. However, there was no strong evidence of the effectiveness of TMS on motor performance (ES: - 0.39, 95% CI - 0.95 to 0.16, p = 0.16). Finally, there was no significant evidence showing the effectiveness of tRNS on fatigue levels (ES: - 0.28, 95% CI: - 1.02 to 0.47, p = 0.46) and cognitive improvement (ES: - 0.04, 95% CI: - 0.6, 0.52, p = 0.88) compared with the sham.

CONCLUSIONS

Overall, most studies have investigated the effects of tDCS on MS symptoms, particularly fatigue. The symptom that most benefited from NIBS was fatigue, while the least to benefit was motor performance. In addition, we found that disability score was associated with fatigue improvement. Thus, these findings support the idea that NIBS could have some promising effects on specific MS symptoms. It is also important to underscore that studies are very heterogeneous regarding the parameters of stimulation, and this may also have influenced the effects on some specific behavioral domains.

Effects of repetitive twice-weekly transcranial direct current stimulations on fatigue and fatigability in people with multiple sclerosis

Fatigue is associated with a dramatically decreased quality of life in people with multiple sclerosis (pwMS). It refers to a constant subjective feeling of exhaustion and performance decline, known as fatigability. However, inconsistency and heterogeneity in defining and assessing fatigue have led to limited advances in understanding and treating MS-associated fatigue. Transcranial direct current stimulation (tDCS) has emerged as a promising, non-pharmaceutical treatment strategy for subjective fatigue. However, whether repetitive tDCS also have long-term effects on time-on-task performance has not yet been investigated. This pseudorandomized, single-blinded, and sham-controlled study investigated tDCS effects on behavioral and electrophysiological parameters. 18 pwMS received eight twice-weekly 30 min stimulations over the left dorsolateral prefrontal cortex. Fatigability was operationalized as time-on-task-related changes in reaction time variability and P300 amplitude. Additionally, subjective trait and state fatigue ratings were assessed. The results revealed an overall decrease in subjective trait fatigue ratings that lasted at least four weeks after the stimulations. However, the ratings declined after both anodal and sham tDCS. No effects were found on subjective state fatigue and objective fatigability parameters. Linear Mixed Models and Bayesian Regression models likewise favored the absence of a tDCS effect on fatigability parameters. The results confirm the complex relationship between MS-associated fatigue and fatigability. Reliable and clinically relevant parameters need to be established to extend the potential of tDCS for treating fatigability. Furthermore, our results indicate that consecutive stimulations rather than twice-weekly stimulations should be the preferred stimulation scheme in future studies.

The therapeutic potential of non-invasive brain stimulation for the treatment of Long-COVID-related cognitive fatigue

Following an acute COVID-19 infection, a large number of patients experience persisting symptoms for more than four weeks, a condition now classified as Long-COVID syndrome. Interestingly, the likelihood and severity of Long-COVID symptoms do not appear to be related to the severity of the acute COVID-19 infection. Fatigue is amongst the most common and debilitating symptoms of Long-COVID. Other symptomes include dyspnoea, chest pain, olfactory disturbances, and brain fog. Fatigue is also frequently reported in many other neurological diseases, affecting a broad range of everyday activities. However, despite its clinical significance, limited progress has been made in understanding its causes and developing effective treatment options. Non-invasive brain stimulation (NIBS) methods offer the unique opportunity to modulate fatigue-related maladaptive neuronal activity. Recent data show promising results of NIBS applications over frontoparietal regions to reduce fatigue symptoms. In this current paper, we review recent data on Long-COVID and Long-COVID-related fatigue (LCOF), with a special focus on cognitive fatigue. We further present widely used NIBS methods, such as transcranial direct current stimulation, transcranial alternating current stimulation, and transcutaneous vagus nerve stimulation and propose their use as possible therapeutic strategies to alleviate individual pathomechanisms of LCOF. Since NIBS methods are safe and well-tolerated, they have the potential to enhance the quality of life in a broad group of patients.

Non-invasive brain stimulation therapy on neurological symptoms in patients with multiple sclerosis: A network meta analysis

OBJECTIVE

The aim of the study was to evaluate non-invasive brain stimulation (NIBS) [including transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES)] on neurological symptoms in patients with multiple sclerosis (PwMS).

METHOD

We searched PubMed, Embase, Cochrane Library, Web of Science and Ovid MEDLINE until February 2022. And we evaluated the included studies for methodological quality by the Cochrane bias risk assessment tool and assessed the studies' certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. We performed network meta analysis (NMA) by using Stata 15 and ranked the results of the NMA by using the surface under the cumulative ranking curve (SUCRA) ranking chart.

RESULT

Twenty seven clinical trials were finally included (N = 596, 66.4% women). For the immediate effects, rTMS over M1 yielded the most optimal scheme for fatigue reduction among all the interventions compared to the sham stimulation groups [MD = -0.85, 95% CI (-1.57, -0.14)] (SUCRA = 82.6%). iTBS over M1 yielded the most signifcant reduced pain level than the sham groups did [MD = -1.26, 95% CI (-2.40, -0.11)] (SUCRA = 98.4%). tDCS over F3 was the best protocol of NIBS to improve quality of life (QOL) [MD = 1.41, 95% CI = (0.45,2.36)] (SUCRA = 76.7%), and iTBS over M1 may significantly reduce spasticity compared to sham stimulation [MD = -1.20, 95% CI = (-1.99, -0.41)] (SUCRA = 90.3%). Furthermore, rTMS, tRNS, and tDCS on certain areas may improve PwMS accuracy, response time, manual dexterity, pain relief and QOL, but does not show statistically significant differences. The evidence assessed using GRADE is very low.

CONCLUSION

Based on the NMA and SUCRA ranking, we can conclude that symptoms including fatigue, pain, spasticity, and QOL can be improved by following NIBS protocol after treatment. Nonetheless, most of the included studies lack a good methodology, and more high-quality randomized clinical trials are needed.

Fatigue in Multiple Sclerosis: A Review of the Exploratory and Therapeutic Potential of Non-Invasive Brain Stimulation

Fatigue is the most commonly reported symptom in patients with multiple sclerosis (MS). It is a worrisome, frequent, and debilitating manifestation that could occur at any time during the course of MS and in all its subtypes. It could engender professional, familial, and socioeconomic consequences and could severely compromise the patients' quality of life. Clinically, the symptom exhibits motor, cognitive, and psychosocial facets. It is also important to differentiate between perceived or subjective self-reported fatigue and fatigability which is an objective measure of decrement in the performance of cognitive or motor tasks. The pathophysiology of MS fatigue is complex, and its management remains a challenge, despite the existing body of literature on this matter. Hence, unraveling its neural mechanisms and developing treatment options that target the latter might constitute a promising field to explore. A PubMed/Medline/Scopus search was conducted to perform this review which aims (a) to reappraise the available electrophysiological studies that explored fatigue in patients with MS with a particular focus on corticospinal excitability measures obtained using transcranial magnetic stimulation and (b) to assess the potential utility of employing neuromodulation (i.e., non-invasive brain stimulation techniques) in this context. A special focus will be put on the role of transcranial direct current stimulation and transcranial magnetic stimulation. We have provided some suggestions that will help overcome the current limitations in upcoming research.

Effects of non-invasive brain stimulation in multiple sclerosis: systematic review and meta-analysis

Objective:

The objective of this meta-analysis was to summarize evidence on the therapeutic effects of non-invasive brain stimulation (NIBS) on core symptoms of multiple sclerosis (MS). Specifically, findings from studies deploying transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) protocols were summarized in this review.

Methods:

We systematically searched articles published in four databases, until 31 May 2021, which compared the effects of active tDCS or rTMS with sham intervention in MS patients. We used a random-effects model for this meta-analysis. Meta-regression and subgroup meta-analysis were used to examine the effects of stimulation dose and different stimulation protocols, respectively.

Results:

Twenty-five randomized controlled trials (RCTs) were included in this review, consisting of 19 tDCS and 6 rTMS studies. tDCS led to a significant and immediate reduction of fatigue with a large effect size (Hedges’s g = −0.870, 95% confidence intervals (CI) = [−1.225 to −0.458], number needed to treat (NNT) = 2). Particularly, a subgroup analysis showed that applying tDCS over the left DLPFC and bilateral S1 led to fatigue reductions compared to sham stimulation. Furthermore, tDCS had favorable effects on fatigue in MS patients with low physical disability but not those with high physical disability, and additionally improved cognitive function. Finally, whereas rTMS was observed to reduce muscle spasticity, these NIBS protocols showed no further effect on MS-associated pain and mood symptoms.

Conclusion:

tDCS in MS alleviates fatigue and improves cognitive function whereas rTMS reduces muscle spasticity. More high-quality studies are needed to substantiate the therapeutic effects of different NIBS protocols in MS.

Multiple sclerosis: Inflammation, autoimmunity and plasticity

In recent years, experimental studies have clarified that immune system influences the functioning of the central nervous system (CNS) in both physiologic and pathologic conditions. The neuro-immune crosstalk plays a crucial role in neuronal development and may be critically involved in mediating CNS response to neuronal damage. Multiple sclerosis (MS) represents a good model to investigate how the immune system regulates neuronal activity. Accordingly, a growing body of evidence has demonstrated that increased levels of pro-inflammatory mediators may significantly impact synaptic mechanisms, influencing overall neuronal excitability and synaptic plasticity expression. In this chapter, we provide an overview of preclinical data and clinical studies exploring synaptic functioning noninvasively with transcranial magnetic stimulation (TMS) in patients with MS. Moreover, we examine how inflammation-driven synaptic dysfunction could affect synaptic plasticity expression, negatively influencing the MS course. Contrasting CSF inflammation together with pharmacologic enhancement of synaptic plasticity and application of noninvasive brain stimulation, alone or in combination with rehabilitative treatments, could improve the clinical compensation and prevent the accumulating deterioration in MS.

Efficacy of transcranial direct current stimulation in people with multiple sclerosis: a review

BACKGROUND AND PURPOSE

Multiple sclerosis (MS) is a chronic inflammatory disease causing a wide range of symptoms including motor and cognitive impairment, fatigue and pain. Over the last two decades, non-invasive brain stimulation, especially transcranial direct current stimulation (tDCS), has increasingly been used to modulate brain function in various physiological and pathological conditions. However, its experimental applications for people with MS were noted only as recently as 2010 and have been growing since then. The efficacy for use in people with MS remains questionable with the results of existing studies being largely conflicting. Hence, the aim of this review is to paint a picture of the current state of tDCS in MS research grounded on studies applying tDCS that have been done to date.

METHODS

A keyword search was performed to retrieve articles from the earliest article identified until 14 February 2021 using a combination of the groups (1) 'multiple sclerosis', 'MS' and 'encephalomyelitis' and (2) 'tDCS' and 'transcranial direct current stimulation'.

RESULTS

The analysis of the 30 articles included in this review underlined inconsistent effects of tDCS on the motor symptoms of MS based on small sample sizes. However, tDCS showed promising benefits in ameliorating fatigue, pain and cognitive symptoms.

CONCLUSION

Transcranial direct current stimulation is attractive as a non-drug approach in ameliorating MS symptoms, where other treatment options remain limited. The development of protocols tailored to the individual's own neuroanatomy using high definition tDCS and the introduction of network mapping in the experimental designs might help to overcome the variability between studies.

A randomized controlled trial to explore the efficacy and safety of transcranial direct current stimulation on patients with post-stroke fatigue

BACKGROUND

Post-stroke fatigue seriously affects the quality of life for stroke patients. There is no effective treatment at present. transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation which may have therapeutic effect on post-stroke fatigue. This study will explore about this.

METHOD

A total of 60 patients with post-stroke fatigue were randomly divided into the control group and the treatment group with 30 patients each by minimization randomization. Both groups received basic treatment and conventional rehabilitation. In the treatment group, patients were treated with active tDCS, while in the control group, sham tDCS. Both active and sham tDCS were administered 6 times a week for 4 weeks. Before and after the trial, the Fatigue Severity Scale (FSS), Fugl-Meyer Assessment (FMA) and Modified Barthel Index (MBI) were evaluated and analyzed. And comparisons were made among groups. And there were an 8-week follow-up after the intervention.

RESULT

Before the intervention, there were no significant differences in baseline data and assessment scores between the groups (P > 0.05). After 4 weeks of intervention, FSS scores in the treatment group were significantly lower than those in the control group (P = 0.012), and FMA and BMI scores were significantly higher than those in the control group (P < 0.05). There was no significant change in FSS scores after 8 months of follow-up (P > 0.05).

DISCUSSION

TDCS is a safe treatment that can effectively reduce the degree of fatigue after stroke, improve the motor function and daily activity ability of patients after stroke, and the efficacy is better than only routine rehabilitation training.

TRIAL REGISTRATION NUMBER

Chinese Clinical Trial Registry, ChiCTR2000031120. Registered on March 22, 2020.

tDCS randomized controlled trials in no-structural diseases: a quantitative review

The increasing number and quality of randomized controlled trials (RCTs) employing transcranial direct current stimulation (tDCS) denote the rising awareness of neuroscientific community about its electroceutical potential and opening to include these treatments in the framework of medical therapies under the indications of the international authorities. The purpose of this quantitative review is to estimate the recommendation strength applying the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) criteria and PICO (population, intervention, comparison, outcome) model values for effective tDCS treatments on no-structural diseases, and to provide an estimate of Sham effect for future RCTs. Applying GRADE evaluation pathway, we searched in literature the tDCS-based RCTs in psychophysical diseases displaying a major involvement of brain electrical activity imbalances. Three independent authors agreed on Class 1 RCTs (18 studies) and meta-analyses were carried out using a random-effects model for pathologies sub-selected based on PICO and systemic involvement criteria. The meta-analysis integrated with extensive evidence of negligible side effects and low-cost, easy-to-use procedures, indicated that tDCS treatments for depression and fatigue in Multiple Sclerosis ranked between moderately and highly recommendable. For these interventions we reported the PICO variables, with left vs. right dorsolateral prefrontal target for 30 min/10 days against depression and bilateral somatosensory vs occipital target for 15 min/5 days against MS fatigue. An across-diseases meta-analysis devoted to the Sham effect provided references for power analysis in future tDCS RCTs on these clinical conditions. High-quality indications support tDCS as a promising tool to build electroceutical treatments against diseases involving neurodynamics alterations.

Effects of Transcranial Direct Current Stimulation on Cognition, Mood, Pain, and Fatigue in Multiple Sclerosis: A Systematic Review and Meta-Analysis

Background: The study aimed to evaluate the effects of transcranial direct current stimulation (tDCS) on cognition, mood disturbance, pain, and fatigue in people with multiple sclerosis (PwMS).

Methods: A literature search was performed on articles published between January 1990 and May 2020 in Pubmed, Medline, and Web of Science using the following keywords and their abbreviation in combinations: multiple sclerosis and transcranial direct current stimulation. Mean effect size (ES) and 95% confidence interval were calculated for each domain of interest.

Results: Seventeen articles with a total of 383 PwMS were included in this analysis. For cognition, a strong effect size was found for the trial administering the Symbol Digit Modalities Test (ES: 1.15), whereas trials applying the Attention Network Test showed a negative effect size of −0.49. Moderate to strong effect sizes were observed for mood disturbance (mean ES: 0.92), pain (mean ES: 0.59), and fatigue (mean ES: 0.60). Further subgroup analyses for MS-related fatigue showed that both high and low intensities of stimulation lead to nearly the same degree of favorable effects. More pronounced effects were observed in studies administering the Fatigue Severity Scale compared with studies using other fatigue measures such as the Modified Fatigue Impact Scale.

Conclusion: These results provide preliminary evidence that tDCS has a favorable effect on cognitive processing speed, mood disturbance, pain, and fatigue in MS. However, the effects on cognition and fatigue vary based on the specific assessment used.

Effect of transcranial direct current stimulation on post-stroke fatigue

Background

Fatigue is one of the most commonly reported symptoms post-stroke, which has a severe impact on the quality of life. Post-stroke fatigue is associated with reduced motor cortical excitability, specifically of the affected hemisphere.

Objective

The aim of this exploratory study was to assess whether fatigue symptoms can be reduced by increasing cortical excitability using anodal transcranial direct current stimulation (tDCS).

Methods

In this sham-controlled, double-blind intervention study, tDCS was applied bilaterally over the primary motor cortex in a single session in thirty stroke survivors with high severity of fatigue. A questionnaire-based measure of trait fatigue (primary outcome) was obtained before, after a week and 5 weeks post stimulation. Secondary outcome measures of state fatigue, motor cortex neurophysiology and perceived effort were also assessed pre, immediately post, a week and 5 weeks post stimulation.

Results

Anodal tDCS significantly improved fatigue symptoms a week after real stimulation when compared to sham stimulation. There was also a significant change in motor cortex neurophysiology of the affected hemisphere and perceived effort, a week after stimulation. The degree of improvement in fatigue was associated with baseline anxiety levels.

Conclusion

A single session of anodal tDCS improves fatigue symptoms with the effect lasting up to a week post stimulation. tDCS may therefore be a useful tool for managing fatigue symptoms post-stroke.

Trial registration

NCT04634864

Date of registration

17/11/2020–“retrospectively registered”.

The Neurobiology of Pathological Fatigue: New Models, New Questions

The last decade has seen the emergence of new theoretical frameworks to explain pathological fatigue, a much neglected, yet highly significant symptom across a wide range of diseases. While the new models of fatigue provide new hypotheses to test, they also raise a number of questions. The primary purpose of this essay is to examine the predictions of three recently proposed models of fatigue, the overlap and differences between them, and the evidence from diseases that may lend support to the models of fatigue. I also present expansions for the sensory attenuation model of fatigue. Further questions examined here are the following: What are the neural substrates of fatigue? How can sensory attenuation, which underpins agency also explain fatigue? Are fatigue and agency related?

Delivering Transcranial Direct Current Stimulation Away From Clinic: Remotely Supervised tDCS

INTRODUCTION

To demonstrate the broad utility of the remotely supervised transcranial direct current stimulation (RS-tDCS) protocol developed to deliver at-home rehabilitation for individuals with multiple sclerosis (MS).

METHODS

Stimulation delivered with the RS-tDCS protocol and paired with adaptive cognitive training was delivered to three different study groups of MS patients to determine the feasibility and tolerability of the protocol. The three studies each used consecutively increasing amounts of stimulation amperage (1.5, 2.0, and 2.5 mA, respectively) and session numbers (10, 20, and 40 sessions, respectively).

RESULTS

High feasibility and tolerability of the stimulation were observed for n = 99 participants across three tDCS pilot studies.

CONCLUSIONS

RS-tDCS is feasible and tolerable for MS participants. The RS-tDCS protocol can be used to reach those in locations without clinic access and be paired with training or rehabilitation in locations away from the clinic. This protocol could be used to deliver tDCS paired with training or rehabilitation activities remotely to service members and veterans.

Impact of Repetitive Transcranial Magnetic Stimulation on Neurocognition and Oxidative Stress in Relapsing-Remitting Multiple Sclerosis: A Case Report

Multiple sclerosis (MS) is a neurodegenerative condition whose manifestation and clinical evolution can present themselves in very different ways. Analogously, its treatment has to be personalized and the patient's response may be idiosyncratic. At this moment there is no cure for it, in addition to its clinical course sometimes being torpid, with a poor response to any treatment. However, Transcranial Magnetic Stimulation (TMS) has demonstrated its usefulness as a non-invasive therapeutic tool for the treatment of some psychiatric and neurodegenerative diseases. Some studies show that the application of rTMS implies improvement in patients with MS at various levels, but the effects at the psychometric level and the redox profile in blood have never been studied before, despite the fact that both aspects have been related to the severity of MS and its evolution. Here we present the case of a woman diagnosed with relapsing-remitting multiple sclerosis (RRMS) at the age of 33, with a rapid progression of her illness and a poor response to different treatments previously prescribed for 9 years. In view of the patient's clinical course, a compassionate treatment with rTMS for 1 year was proposed. Starting from the fourth month of treatment, when reviewing the status of her disease, the patient denoted a clear improvement at different levels. There followed out psychometric evaluations and blood analyses, that showed both an improvement in her neuropsychological functions and a reduction in oxidative stress in plasma, in correspondence with therTMS treatment.

The effect of tDCS on the fatigue in patients with multiple sclerosis: A systematic review of randomized controlled clinical trials

INTRODUCTION

Fatigue is one of the most common disabling symptoms in patients with multiple sclerosis (MS) which is present in 75% of these patients and is usually associated with functional disabilities. According to the literature, there is no general agreement on the effectiveness of the existing treatments for fatigue in patients with MS. As transcranial direct current stimulation (tDCS) is a relatively new method in the treatment of fatigue symptoms in patients with MS, the purpose of this study was to systematically review published evidence conducted to assess the effects of tDCS on fatigue in patients with MS.

MATERIAL & METHODS

A thorough literature search of published articles was conducted from 1996 to 2019 in different databases including PubMed, Science Direct, OVID, Google Scholar, Cochrane Library, Scopus, Embase, ProQuest and web of science with keywords of "tDCS", "multiple Sclerosis" and "Fatigue". Results yielded 1017 studies, which after excluding articles based on duplication and title and abstract, 8 of them were selected for review in this study.

RESULTS

The results from the literature revealed that six studies indicated positive effects of tDCS stimulation on fatigue reduction. In four studies stimulation was over the right dorsolateral prefrontal cortex (DLPFC); in three studies stimulation placed over the whole body's primary somatosensory cortex (S1); and in one study stimulation applied over the posterior parietal cortex. In most studies, no serious side effects were reported.

CONCLUSION

Most studies revealed that tDCS can reduce the adverse effects of MS-related fatigue in particular cognitive type. As follow-ups were either absent or short period, as well as the application of treatment protocols and measurement instruments were different, it was very difficult to draw strong conclusion on the effects of tDCS in patients with MS. However, further large scale studies with long term follow-up are still recommended.

The Potential Role of Neurophysiology in the Management of Multiple Sclerosis-Related Fatigue

Fatigue is a very common symptom among people with multiple sclerosis (MS), but its management in clinical practice is limited by the lack of clear evidence about the pathogenic mechanisms, objective tools for diagnosis, and effective pharmacological treatments. In this scenario, neurophysiology could play a decisive role, thanks to its ability to provide objective measures and to explore the peripheral and the central structures of the nervous system. We hereby review and discuss current evidence about the potential role of neurophysiology in the management of MS-related fatigue. In the first part, we describe the use of neurophysiological techniques for exploring the pathogenic mechanisms of fatigue. In the second part, we review the potential application of neurophysiology for monitoring the response to pharmacological therapies. Finally, we show data about the therapeutic implications of neurophysiological techniques based on non-invasive brain stimulation.

The Tolerability and Efficacy of 4 mA Transcranial Direct Current Stimulation on Leg Muscle Fatigability

Transcranial direct current stimulation (tDCS) modulates cortical excitability and affects a variety of outcomes. tDCS at intensities ≤2 mA is well-tolerated, but the tolerability and efficacy of tDCS at intensities >2 mA merits systematic investigation. The study objective was to determine the tolerability and effects of 4 mA tDCS on leg muscle fatigability. Thirty-one young, healthy adults underwent two randomly ordered tDCS conditions (sham, 4 mA) applied before and during an isokinetic fatigue test of the knee extensors and flexors. Subjects reported the severity of the sensations felt from tDCS. Primary outcomes were sensation tolerability and the fatigue index of the knee extensors and flexors. A repeated-measures ANOVA determined statistical significance (p < 0.05). Sensation severity at 4 mA tDCS was not substantially different than sham. However, two subjects reported a moderate–severe headache, which dissipated soon after the stimulation ended. The left knee flexors had significantly greater fatigability with 4 mA tDCS compared with sham (p = 0.018). tDCS at 4 mA was well-tolerated by young, healthy subjects and increased left knee flexor fatigability. Exploration of higher intensity tDCS (>2 mA) to determine the potential benefits of increasing intensity, especially in clinical populations with decreased brain activity/excitability, is warranted.

Cognitive Fatigability Interventions in Neurological Conditions: A Systematic Review

INTRODUCTION

Although fatigue is a well-studied concept in neurological disease, cognitive fatigability (CF) is less understood. While most studies measure fatigue using subjective self-report, fewer have measured CF objectively. Given the negative impact of CF on quality-of-life, there is a need for targeted interventions. The objective of this review was to determine which procedural, behavioural and pharmacological treatments for objectively measured CF are available to people living with neurological conditions.

METHODS

In accordance with the PRISMA guidelines, systematic searches for randomized control trials (RCTs), case-controlled studies and case reports/series were conducted across the Ovid Medline, PsycInfo, EMBASE and Cochrane Library databases. English-language articles published between 1980 and February 2019 were considered for eligibility. Included were those that objectively measured CF in individuals with neurological disease/disorder/dysfunction between the ages of 18 and 65 years. Studies were reviewed using a modified Cochrane Data Extraction Template. Risk of bias was assessed using the Cochrane Risk of Bias tool. The review process was facilitated using Covidence software (www.covidence.org). Two authors reviewed articles independently, with a third resolving conflicts regarding article inclusion.

RESULTS

The search identified 450 records. After duplicates were removed and remaining titles/abstracts were screened for eligibility, 28 full-text articles were assessed, and two studies were included in the qualitative synthesis. Studies were a priori divided into those with pharmacological, procedural or behavioural interventions. Two studies met eligibility criteria; both of these included participants with multiple sclerosis. One study utilized a procedural intervention (i.e. transcranial direct current stimulation), while the other utilized a pharmacological intervention (i.e. fampridine-SR). Studies were evaluated for risk of bias, and evidence from both eligible studies was discussed.

CONCLUSION

Despite the positive results of the procedural intervention, the paucity of eligible studies and the nascent nature of the field suggests that more studies are required before firm conclusions can be drawn regarding the amenability of CF to treatment.

TRIAL REGISTRATION

The review was registered with PROSPERO (CRD42019118706).

Transcranial Direct Current Stimulation (tDCS) to Improve Gait in Multiple Sclerosis: A Timing Window Comparison

Unilateral weakness of the lower limb is a hallmark of multiple sclerosis (MS) and a significant contributor to the progressive worsening of walking ability. There are currently no effective rehabilitation strategies targeting strength asymmetries and/or gait impairments in people with MS (PwMS). Transcranial direct current stimulation (tDCS) has improved motor outcomes in various populations, but the effect of tDCS on gait in PwMS and the ideal timing window of tDCS application are still unknown. This study investigated the effects of tDCS, either before or during a 6 min walk test (6MWT), on the distance walked and gait characteristics in PwMS. Twelve participants were recruited and randomly assigned into BEFORE or DURING groups (both n = 6). The BEFORE group received stimulation before performing a 6MWT (sham/2 mA, 13 min). The DURING group received stimulation only during a 6MWT (sham/2 mA, 6 min). Stimulation was over the more MS-affected primary motor cortex (M1). Distance walked and gait characteristics of the walk were the primary and secondary outcomes. The results indicated a significant decrease in distance walked in the DURING group (p = 0.026) and a significant increase in gait velocity in the BEFORE group (p = 0.04). These changes were accompanied by trends (p < 0.1) in distance walked, gait velocity, and stride length. Overall, the results of this study suggest that tDCS performed before a 6MWT might be more effective than tDCS during a 6MWT and that a single session of tDCS may not be sufficient to influence gait. Clinical Trial Registration: www.ClinicalTrials.gov, identifier #NCT03757819.

Beyond the target area: an integrative view of tDCS-induced motor cortex modulation in patients and athletes

Transcranial Direct Current Stimulation (tDCS) is a non-invasive technique used to modulate neural tissue. Neuromodulation apparently improves cognitive functions in several neurologic diseases treatment and sports performance. In this study, we present a comprehensive, integrative review of tDCS for motor rehabilitation and motor learning in healthy individuals, athletes and multiple neurologic and neuropsychiatric conditions. We also report on neuromodulation mechanisms, main applications, current knowledge including areas such as language, embodied cognition, functional and social aspects, and future directions. We present the use and perspectives of new developments in tDCS technology, namely high-definition tDCS (HD-tDCS) which promises to overcome one of the main tDCS limitation (i.e., low focality) and its application for neurological disease, pain relief, and motor learning/rehabilitation. Finally, we provided information regarding the Transcutaneous Spinal Direct Current Stimulation (tsDCS) in clinical applications, Cerebellar tDCS (ctDCS) and its influence on motor learning, and TMS combined with electroencephalography (EEG) as a tool to evaluate tDCS effects on brain function.

Beyond rehabilitation in MS: Insights from non-invasive brain stimulation

Although the number of disease-modifying treatments for people with multiple sclerosis (pwMS) has meaningfully increased in the past years, targeting repair or compensation for central nervous system damage associated with the disease process remains an important clinical goal. With this aim, neurorehabilitation is a powerful approach targeting central nervous system plasticity. Another driver of brain plasticity is non-invasive brain stimulation (NIBS), receiving recent attention in neurology, particularly for its potential synergy with neurorehabilitation and as add-on treatment for several neurological conditions, from pain to fatigue to sensorimotor and cognitive deficits. In this review, we will resume the evidence exploring the neurobiological basis of NIBS and its applications to MS-related conditions.

Non-invasive brain stimulation for fatigue in multiple sclerosis patients: A systematic review and meta-analysis

BACKGROUND

To investigate the efficacy and safety of non-invasive brain stimulation for fatigue in multiple sclerosis patients.

METHODS

We searched MEDLINE, Embase, Web of Science, Cochrane Library, Chinese National Knowledge Infrastructure, and Wanfang databases up to October 25, 2018 (PROSPERO registration number: CRD42018112823). Randomized or pseudo-randomized, sham-controlled clinical trials evaluating the effect of non-invasive brain stimulation (NIBS) such as transcranial direct current stimulation (tDCS), transcranial magnetic stimulation (TMS), transcranial random noise stimulation (tRNS), transcranial alternating current stimulation (tACS), cranial electrotherapy stimulation, and reduced impedance non-invasive cortical electrostimulation were included. Two authors independently performed data extraction and risk of bias assessment according to Cochrane Handbook for Systematic Reviews of Interventions Version 5.0.1. The primary outcome was fatigue scores before and after stimulation and the secondary outcome was adverse events.

RESULTS

Data from cross-over and parallel group studies were pooled using a generic inverse-variance approach. A total of 14 studies (11 for tDCS, 2 for TMS, and 1 for tRNS) recruiting 207 patients were included in the systematic review and meta-analysis. No eligible tACS, cranial electrotherapy stimulation or reduced impedance non-invasive cortical electrostimulation studies were found. Short-term and long-term treatment effects were significant for tDCS, whereas TMS and tRNS were not superior to sham stimulation. The available evidence supported the effectiveness of the 1.5 mA subgroup and bilateral S1 subgroup of tDCS. Adverse events were minor and transient but comparable between real and sham stimulation.

CONCLUSIONS

tDCS is a safe and effective treatment for fatigue in MS patients. However, further studies are required to confirm our results in a large-scale population and to investigate the effectiveness of other NIBS subtypes.

Cognitive Fatigue in Multiple Sclerosis: An Objective Approach to Diagnosis and Treatment by Transcranial Electrical Stimulation

Cognitive fatigue is one of the most frequent symptoms in multiple sclerosis (MS), associated with significant impairment in daily functioning and quality of life. Despite its clinical significance, progress in understanding and treating fatigue is still limited. This limitation is already caused by an inconsistent and heterogeneous terminology and assessment of fatigue. In this review, we integrate previous literature on fatigue and propose a unified schema aiming to clarify the fatigue taxonomy. With special focus on cognitive fatigue, we survey the significance of objective behavioral and electrophysiological fatigue parameters and discuss the controversial literature on the relationship between subjective and objective fatigue assessment. As MS-related cognitive fatigue drastically affects quality of life, the development of efficient therapeutic approaches for overcoming cognitive fatigue is of high clinical relevance. In this regard, the reliable and valid assessment of the individual fatigue level by objective parameters is essential for systematic treatment evaluation and optimization. Transcranial electrical stimulation (tES) may offer a unique opportunity to manipulate maladaptive neural activity underlying MS fatigue. Therefore, we discuss evidence for the therapeutic potential of tES on cognitive fatigue in people with MS.

The place of transcranial direct current stimulation in the management of multiple sclerosis-related symptoms

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, characterized by chronic inflammation, demyelination, synaptopathy and neurodegeneration. Patients may exhibit sensory, motor, cognitive, emotional and behavioral symptoms throughout their disease process. Nowadays, the challenge is to find optimal treatment for MS symptoms, especially that available pharmacological interventions are faced by modest therapeutic outcomes and numerous side effects. Thus, finding alternative strategies might be of help in this context. The aim of this report is to visit the effects of transcranial direct current stimulation - a noninvasive brain stimulation technique - in the context of MS symptoms, namely fatigue, cognitive deficits, psychiatric complaints, neuropathic pain and some sensorimotor manifestations.

Transcranial direct current stimulation: A glimmer of hope for multiple sclerosis fatigue?

Multiple sclerosis (MS) is a neurological disease of the central nervous system characterized by inflammation, demyelination and neurodegeneration. Throughout the disease process, patients may complain of a panel of sensory, motor, cognitive and behavioral symptoms. Fatigue is a debilitating manifestation of central nervous system diseases with physical, cognitive and psychosocial dimensions. In MS, fatigue could be very frequent concerning up to 90% of patients and may have a drastic impact on their quality of life. Based on neuroimaging studies, a 'cortico-striato-thalamo-cortical' loop seems to underlie this symptom. Despite the availability of pharmacological molecules, the majority of them fail to bring satisfactory outcomes mainly because of the numerous related side-effects. Therefore, finding a safe, easy to implement, and effective alternative therapy is highly needed. These properties appear to match those of noninvasive brain stimulation techniques such as transcranial direct current stimulation (tDCS). tDCS consists of placing two electrodes over cortical sites, such as those that take part in MS fatigue loop. Here, tDCS protocols targeting MS fatigue are revisited. Their short and long-term effects are discussed. The majority of the available protocols have applied 5 consecutive daily 20-min sessions of anodal tDCS over specific cortical sites and yielded beneficial effects on MS fatigue. Finally, the recent emergence of remotely supervised tDCS protocols are also tackled in this work aiming to address the future possibility of translating the current research data into routine clinical practice. This may lead to optimize patients' care and improve their quality of life.

The therapeutic use of non-invasive brain stimulation in multiple sclerosis - a review

BACKGROUND

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system and a leading cause of disability in young adults. Many disabling symptoms in MS, such as spasticity, pain, depression and cognitive deficits are not fully controlled by drug treatment. Non-invasive brain stimulation (NIBS) techniques can be used as tools for modulating altered cortical excitability and plasticity MS patients, providing an improvement in disabling symptoms affecting such patients.

OBJECTIVE

This review reported and summarized some of the most interesting and promising recent achievements regarding the therapeutic use of NIBS in MS patients.

METHODS

We reviewed the clinical application of transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS), emphasizing their effect on clinical symptoms and signs that are commonly involved in MS patients. In addition, we shortly described new NIBS protocols, such as transcranial alternating current stimulation and transcranial focused ultrasound stimulation as potential and innovative therapeutic options to be applied in future studies in MS patients.

RESULTS

We reviewed twenty-one studies covering six main clinical domains. Most of such studies focused on fatigues (33.3%), motor performance (19%) and spasticity (19%), sparse results were about pain (9.5%), cognitive abilities (9.5%), sensory deficit (4.8%) and bladder function (4.8%). The most promising results have been published for the improvement of motor (i.e. hand dexterity) and cognitive performances (i.e. attention and working memory) by applying rTMS or tDCS alone or in association with motor/cognitive training, for pain's treatment by using tDCS.

CONCLUSION

There are still no official recommendations for the therapeutic use of tDCS or rTMS in MS. The huge inter-individual variability of NIBS efficacy is still a big challenge which needs to be solved. However, well-designed studies, deeper knowledge about pathomechanisms underlying MS, and the combination of such techniques with motor and cognitive rehabilitation might results in higher effectiveness of NIBS.

MRI-Guided Regional Personalized Electrical Stimulation in Multisession and Home Treatments

The shape and position of the electrodes is a key factor for the efficacy of transcranial electrical stimulations (tES). We have recently introduced the Regional Personalized Electrode (RePE), a tES electrode fitting the personal cortical folding, that has been able to differentiate the stimulation of close by regions, in particular the primary sensory (S1) and motor (M1) cortices, and to personalize tES onto such an extended cortical district. However, neuronavigation on individual brain was compulsory for the correct montage. Here, we aimed at developing and testing a neuronavigation-free procedure for easy and quick positioning RePE, enabling multisession RePE-tES at home. We used off-line individual MRI to shape RePE via an ad-hoc computerized procedure, while an ad-hoc developed Adjustable Helmet Frame (AHF) was used to properly position it in multisession treatments, even at home. We used neuronavigation to test the RePE shape and position obtained by the new computerized procedure and the re-positioning obtained via the AHF. Using Finite Element Method (FEM) model, we also estimated the intra-cerebral current distribution induced by transcranial direct current stimulation (tDCS) comparing RePE vs. non-RePE with fixed reference. Additionally, we tested, using FEM, various shapes, and positions of the reference electrode taking into account possible small displacements of RePE, to test feasibility of RePE-tES sessions at home. The new RePE neuronavigation-free positioning relies on brain MRI space distances, and produced a mean displacement of 3.5 ± 0.8 mm, and the re-positioning of 4.8 ± 1.1 mm. Higher electric field in S1 than in M1 was best obtained with the occipital reference electrode, a montage that proved to feature low sensitivity to typical RePE millimetric displacements. Additionally, a new tES accessory was developed to enable repositioning the electrodes over the scalp also at home, with a precision which is acceptable according to the modeling-estimated intracerebral currents. Altogether, we provide here a procedure to simplify and make easily applicable RePE-tDCS, which enables efficacious personalized treatments.

Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS)

A group of European experts was commissioned by the European Chapter of the International Federation of Clinical Neurophysiology to gather knowledge about the state of the art of the therapeutic use of transcranial direct current stimulation (tDCS) from studies published up until September 2016, regarding pain, Parkinson's disease, other movement disorders, motor stroke, poststroke aphasia, multiple sclerosis, epilepsy, consciousness disorders, Alzheimer's disease, tinnitus, depression, schizophrenia, and craving/addiction. The evidence-based analysis included only studies based on repeated tDCS sessions with sham tDCS control procedure; 25 patients or more having received active treatment was required for Class I, while a lower number of 10-24 patients was accepted for Class II studies. Current evidence does not allow making any recommendation of Level A (definite efficacy) for any indication. Level B recommendation (probable efficacy) is proposed for: (i) anodal tDCS of the left primary motor cortex (M1) (with right orbitofrontal cathode) in fibromyalgia; (ii) anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC) (with right orbitofrontal cathode) in major depressive episode without drug resistance; (iii) anodal tDCS of the right DLPFC (with left DLPFC cathode) in addiction/craving. Level C recommendation (possible efficacy) is proposed for anodal tDCS of the left M1 (or contralateral to pain side, with right orbitofrontal cathode) in chronic lower limb neuropathic pain secondary to spinal cord lesion. Conversely, Level B recommendation (probable inefficacy) is conferred on the absence of clinical effects of: (i) anodal tDCS of the left temporal cortex (with right orbitofrontal cathode) in tinnitus; (ii) anodal tDCS of the left DLPFC (with right orbitofrontal cathode) in drug-resistant major depressive episode. It remains to be clarified whether the probable or possible therapeutic effects of tDCS are clinically meaningful and how to optimally perform tDCS in a therapeutic setting. In addition, the easy management and low cost of tDCS devices allow at home use by the patient, but this might raise ethical and legal concerns with regard to potential misuse or overuse. We must be careful to avoid inappropriate applications of this technique by ensuring rigorous training of the professionals and education of the patients.

A simple method for EEG guided transcranial electrical stimulation without models

OBJECTIVE

There is longstanding interest in using EEG measurements to inform transcranial Electrical Stimulation (tES) but adoption is lacking because users need a simple and adaptable recipe. The conventional approach is to use anatomical head-models for both source localization (the EEG inverse problem) and current flow modeling (the tES forward model), but this approach is computationally demanding, requires an anatomical MRI, and strict assumptions about the target brain regions. We evaluate techniques whereby tES dose is derived from EEG without the need for an anatomical head model, target assumptions, difficult case-by-case conjecture, or many stimulation electrodes.

APPROACH

We developed a simple two-step approach to EEG-guided tES that based on the topography of the EEG: (1) selects locations to be used for stimulation; (2) determines current applied to each electrode. Each step is performed based solely on the EEG with no need for head models or source localization. Cortical dipoles represent idealized brain targets. EEG-guided tES strategies are verified using a finite element method simulation of the EEG generated by a dipole, oriented either tangential or radial to the scalp surface, and then simulating the tES-generated electric field produced by each model-free technique. These model-free approaches are compared to a 'gold standard' numerically optimized dose of tES that assumes perfect understanding of the dipole location and head anatomy. We vary the number of electrodes from a few to over three hundred, with focality or intensity as optimization criterion.

MAIN RESULTS

Model-free approaches evaluated include (1) voltage-to-voltage, (2) voltage-to-current; (3) Laplacian; and two Ad-Hoc techniques (4) dipole sink-to-sink; and (5) sink to concentric. Our results demonstrate that simple ad hoc approaches can achieve reasonable targeting for the case of a cortical dipole, remarkably with only 2-8 electrodes and no need for a model of the head.

SIGNIFICANCE

Our approach is verified directly only for a theoretically localized source, but may be potentially applied to an arbitrary EEG topography. For its simplicity and linearity, our recipe for model-free EEG guided tES lends itself to broad adoption and can be applied to static (tDCS), time-variant (e.g., tACS, tRNS, tPCS), or closed-loop tES.