Non-invasive brain stimulation for Parkinson's disease: Clinical evidence, latest concepts and future goals: A systematic review

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.

Deep brain stimulation in Parkinson's disease: A scientometric and bibliometric analysis, trends, and research hotspots

Parkinson disease (PD), a prevalent neurodegenerative ailment in the elderly, relies mainly on pharmacotherapy, yet deep brain stimulation (DBS) emerges as a vital remedy for refractory cases. This study performs a bibliometric analysis on DBS in PD, delving into research trends and study impact to offer comprehensive insights for researchers, clinicians, and policymakers, illuminating the current state and evolutionary trajectory of research in this domain. A systematic search on March 13, 2023, in the Scopus database utilized keywords like "Parkinson disease," "PD," "Parkinsonism," "Deep brain stimulation," and "DBS." The top 1000 highly cited publications on DBS in PD underwent scientometric analysis via VOS Viewer and R Studio's Bibliometrix package, covering publication characteristics, co-authorship, keyword co-occurrence, thematic clustering, and trend topics. The bibliometric analysis spanned 1984 to 2021, involving 1000 cited articles from 202 sources. The average number of citations per document were 140.9, with 31,854 references. "Movement Disorders" led in publications (n = 98), followed by "Brain" (n = 78) and "Neurology" (n = 65). The University of Oxford featured prominently. Thematic keyword clustering identified 9 core research areas, such as neuropsychological function and motor circuit electrophysiology. The shift from historical neurosurgical procedures to contemporary focuses like "beta oscillations" and "neuroethics" was evident. The bibliometric analysis emphasizes UK and US dominance, outlining 9 key research areas pivotal for reshaping Parkinson treatment. A discernible shift from invasive neurosurgery to DBS is observed. The call for personalized DBS, integration with NIBS, and exploration of innovative avenues marks the trajectory for future research.

Lead-free dual-frequency ultrasound implants for wireless, biphasic deep brain stimulation

Ultrasound-driven bioelectronics could offer a wireless scheme with sustainable power supply; however, current ultrasound implantable systems present critical challenges in biocompatibility and harvesting performance related to lead/lead-free piezoelectric materials and devices. Here, we report a lead-free dual-frequency ultrasound implants for wireless, biphasic deep brain stimulation, which integrates two developed lead-free sandwich porous 1-3-type piezoelectric composite elements with enhanced harvesting performance in a flexible printed circuit board. The implant is ultrasonically powered through a portable external dual-frequency transducer and generates programmable biphasic stimulus pulses in clinically relevant frequencies. Furthermore, we demonstrate ultrasound-driven implants for long-term biosafety therapy in deep brain stimulation through an epileptic rodent model. With biocompatibility and improved electrical performance, the lead-free materials and devices presented here could provide a promising platform for developing implantable ultrasonic electronics in the future.

Knocking down GRAMD1C expression reduces 6-OHDA-induced apoptosis in PC12 cells

Aim

To explore the differential genes in Parkinson's disease (PD) through a preliminary GEO database, and to investigate the possible mechanisms.

Materials and Methods

The PD differentially expressed genes (DEGs) were analyzed by the microarray method. Then, these DEGs were applied to KEGG and GO analyses to predict the related signaling pathways and molecular functions. Comparison of GRAMD1C expression levels in the putamen of normal and Parkinson's patients by bioinformatic analysis. PC12 cells were cultured to construct a 6-hydroxydopamine (6-OHDA)-induced Parkinson's cell model. RT-qPCR was performed to detect the efficiency of GRAMD1C siRNA. MTT assay was conducted to examine the proliferation of cells. Then, the apoptosis of each group of cells was measured by flow cytometry. Western blot was carried out to determine the expression of apoptosis-related proteins.

Results

Through bioinformatics, GRAMD1C was confirmed to be one of the most significantly upregulated genes in PD. Furthermore, GRAMD1C was notably enhanced in the PD patients and 6-OHDA-induced PC12 cells. Besides, 6-OHDA stimulation significantly reduced PC12 cell proliferation, and it reverted with the GRAMD1C siRNA. Moreover, the flow cytometry results showed that knockdown of GRAMD1C could effectively reduce the high apoptosis rate of PC12 cells induced by 6-OHDA treatment. Similarly, western blot results found that 6-OHDA stimulation markedly increased the expression levels of Bax and Caspase 3Caspase 3 and decreased the Bcl-2 expression in PC12 cells, and GRAMD1C knockdown reversed these changes.

Conclusion

GRAMD1C is upregulated in PD, and may affect the PD process through the apoptotic pathway.

Transcranial alternating current stimulation improves quality of life in Parkinson's disease: study protocol for a randomized, double-blind, controlled trial

BACKGROUND

The neural cells in the brains of patients with Parkinson's disease (PWP) display aberrant synchronized oscillatory activity within the beta frequency range. Additionally, enhanced gamma oscillations may serve as a compensatory mechanism for motor inhibition mediated by beta activity and also reinstate plasticity in the primary motor cortex affected by Parkinson's disease. Transcranial alternating current stimulation (tACS) can synchronize endogenous oscillations with exogenous rhythms, thereby modulating cortical activity. The objective of this study is to investigate whether the addition of tACS to multidisciplinary intensive rehabilitation treatment (MIRT) can improve symptoms of PWP so as to enhance the quality of life in individuals with Parkinson's disease based on the central-peripheral-central theory.

METHODS

The present study was a randomized, double-blind trial that enrolled 60 individuals with Parkinson's disease aged between 45 and 70 years, who had Hoehn-Yahr scale scores ranging from 1 to 3. Participants were randomly assigned in a 1:1 ratio to either the tACS + MIRT group or the sham-tACS + MIRT group. The trial consisted of a two-week double-blind treatment period followed by a 24-week follow-up period, resulting in a total duration of twenty-six weeks. The primary outcome measured the change in PDQ-39 scores from baseline (T0) to 4 weeks (T2), 12 weeks (T3), and 24 weeks (T4) after completion of the intervention. The secondary outcome assessed changes in MDS-UPDRS III scores at T0, the end of intervention (T1), T2, T3, and T4. Additional clinical assessments and mechanistic studies were conducted as tertiary outcomes.

DISCUSSION

The objective of this study is to demonstrate that tACS can enhance overall functionality and improve quality of life in PWP, based on the framework of MIRT. Additionally, it seeks to establish a potential correlation between these therapeutic effects and neuroplasticity alterations in relevant brain regions. The efficacy of tACS will be assessed during the follow-up period in order to optimize neuroplasticity and enhance its potential impact on rehabilitation efficiency for PWP.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2300071969. Registered on 30 May 2023.

Transcranial direct current stimulation improves motor function in rats with 6-hydroxydopamine-induced Parkinsonism

Transcranial direct current stimulation (tDCS) is increasingly being used for Parkinson's disease (PD); however, the evaluation of its clinical impact remains complex owing to the heterogeneity of patients and treatments. Therefore, we used a unilateral 6-hydroxydopamine-induced PD rat model to investigate whether anodal tDCS of the primary motor cortex (M1) alleviates PD motor deficits. Before tDCS treatment, unilateral PD rats preferentially used the forelimb ipsilateral to the lesion in the exploratory cylinder test and showed reduced locomotor activity in the open field test. In addition, PD-related clumsy forelimb movements during treadmill walking were detected using deep learning-based video analysis (DeepLabCut). When the 5-day tDCS treatment began, the forelimb-use asymmetry was ameliorated gradually, and locomotor activity increased to pre-lesion levels. tDCS treatment also normalized unnatural forelimb movement during walking and restored a balanced gait. However, these therapeutic effects were rapidly lost or gradually disappeared when the tDCS treatment was terminated. Histological analysis at the end of the experiment revealed that the animals had moderately advanced PD, with 40-50% of dopamine neurons and fibers preserved on the injured side compared with those on the intact side. Although it remains a challenge to elucidate the neural mechanisms of the transient improvement in motor function induced by tDCS, the results of this study provide evidence that tDCS of the M1 produces positive behavioral outcomes in PD animals and provides the basis for further clinical research examining the application of tDCS in patients with PD.

Novel ultrasound neuromodulation therapy with transcranial pulse stimulation (TPS) in Parkinson's disease: a first retrospective analysis

BACKGROUND

Transcranial Pulse Stimulation (TPS) has been recently introduced as a novel ultrasound neuromodulation therapy with the potential to stimulate the human brain in a focal and targeted manner. Here, we present a first retrospective analysis of TPS as an add-on therapy for Parkinson's disease (PD), focusing on feasibility, safety, and clinical effects. We also discuss the placebo response in non-invasive brain stimulation studies as an important context.

METHODS

This retrospective clinical data analysis included 20 PD patients who received ten sessions of TPS intervention focused on the individual motor network. Safety evaluations were conducted throughout the intervention period. We analyzed changes in motor symptoms before and after TPS treatment using Unified Parkinson's Disease Rating Scale part III (UPDRS-III).

RESULTS

We found significant improvement in UPDRS-III scores after treatment compared to baseline (pre-TPS: 16.70 ± 8.85, post-TPS: 12.95 ± 8.55; p < 0.001; Cohen's d = 1.38). Adverse events monitoring revealed no major side effects.

CONCLUSION

These preliminary findings suggest that TPS can further improve motor symptoms in PD patients already on optimized standard therapy. Findings have to be evaluated in context with the current literature on placebo effects.

Slowing gait during turning: how volition of modifying walking speed affects the gait pattern in healthy adults

Background

Turning during walking and volitionally modulating walking speed introduces complexity to gait and has been minimally explored.

Research question

How do the spatiotemporal parameters vary between young adults walking at a normal speed and a slower speed while making 90°, 180°, and 360° turns?

Methods

In a laboratory setting, the spatiotemporal parameters of 10 young adults were documented as they made turns at 90°, 180°, and 360°. A generalized linear model was utilized to determine the effect of both walking speed and turning amplitude.

Results

Young adults volitionally reducing their walking speed while turning at different turning amplitudes significantly decreased their cadence and spatial parameters while increasing their temporal parameters. In conditions of slower movement, the variability of certain spatial parameters decreased, while the variability of some temporal parameters increased.

Significance

This research broadens the understanding of turning biomechanics in relation to volitionally reducing walking speed. Cadence might be a pace gait constant synchronizing the rhythmic integration of several inputs to coordinate an ordered gait pattern output. Volition might up-regulate or down-regulate this pace gait constant (i.e., cadence) which creates the feeling of modulating walking speed.

Effects of transcranial direct current stimulation alone and in combination with rehabilitation therapies on gait and balance among individuals with Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

Parkinson's disease (PD) is a neurogenerative disorder implicated in dysfunctions of motor functions, particularly gait and balance. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation offered as a potential adjuvant therapy for PD. This systematic review and meta-analysis were conducted to identify whether tDCS alone and combined with additional rehabilitation therapies improve gait and balance among individuals with PD.

METHODS

We searched PubMed, Embase, Web of Science, and relevant databases for eligible studies from inception to December 2022. Studies with a comparative design investigating the effects of tDCS on motor functions, including gait and balance among individuals with PD, were included. A meta-analysis was performed for each outcome using a random effects model for subgroup analysis and pooling of overall effect sizes.

RESULTS

A total of 23 studies were included in the meta-analysis. The pooled results revealed that tDCS has moderate overall effects on gait, measured by gait speed (standardized mean deviation [SMD] = 0.238; 95% confidence interval [CI]  - 0.026 to 0.502); stride length (SMD = 0.318; 95% CI - 0.015 to 0.652); cadence (SMD =  - 0.632; 95% CI - 0.932 to - 0.333); freezing of gait questionnaire scores (SMD =  - 0.360; 95% CI - 0.692 to - 0.027); step length (SMD = 0.459; 95% CI - 0.031 to 0.949); walking time (SMD =  - 0.253; 95% CI - 0.758 to 0.252); stride time (SMD =  - 0.785; 95% CI: - 1.680 to 0.111); double support time (SMD = 1.139; 95% CI - 0.244 to 0.523); and balance, measured by timed up and go (TUG) test (SMD =  - 0.294; 95% CI - 0.516 to - 0.073), Berg balance scale (BBS) scores (SMD = 0.406; 95% CI - 0.059 to 0.87), and dynamic gait index (SMD = 0.275; 95% CI - 0.349 to 0.898). For the subgroup analysis, gait and balance demonstrated moderate effect sizes. However, only cadence, stride time, and TUG indicated a significant difference between real and sham tDCS (P = 0.027, P = 0.002, and P = 0.023, respectively), whereas cadence and BBS (P < 0.01 and P = 0.045, respectively) significantly differed after real tDCS plus other therapies rather than after sham tDCS plus other therapies.

CONCLUSIONS

Our results indicated that tDCS is significantly associated with gait and balance improvements among individuals with PD. The findings of this study provide more proof supporting the effectiveness of tDCS, encouraging tDCS to be utilized alone or in combination with other therapies in clinical practice for PD rehabilitation.

Insights from a model based study on optimizing non invasive brain electrical stimulation for Parkinson's disease

Parkinson's Disease (PD) is a disorder in the central nervous system which includes symptoms such as tremor, rigidity, and Bradykinesia. Deep brain stimulation (DBS) is the most effective method to treat PD motor symptoms especially when the patient is not responsive to other treatments. However, its invasiveness and high risk, involving electrode implantation in the Basal Ganglia (BG), prompt recent research to emphasize non-invasive Transcranial Electrical Stimulation (TES). TES proves to be effective in treating some PD symptoms with inherent safety and no associated risks. This study explores the potential of using TES, to modify the firing pattern of cells in BG that are responsible for motor symptoms in PD. The research employs a mathematical model of the BG to examine the impact of applying TES to the brain. This is conducted using a realistic head model incorporating the Finite Element Method (FEM). According to our findings, the firing pattern associated with Parkinson's disease shifted towards a healthier firing pattern through the use of tACS. Employing an adaptive algorithm that continually monitored the behavior of BG cells (specifically, Globus Pallidus Pars externa (GPe)), we determined the optimal electrode number and placement to concentrate the current within the intended region. This resulted in a peak induced electric field of 1.9 v/m at the BG area. Our mathematical modeling together with precise finite element simulation of the brain and BG suggests that proposed method effectively mitigates Parkinsonian behavior in the BG cells. Furthermore, this approach ensures an improvement in the condition while adhering to all safety constraints associated with the current injection into the brain.

Long-term repetitive transcranial direct current stimulation in patients with disorders of consciousness: a preliminary study

OBJECTIVES

To investigate the effects of long-term repetitive transcranial direct current stimulation on patients with DOC in the subacute phase.

METHODS

In a randomized, double-blind, controlled study, 33 patients were randomly assigned to the active or sham group, and 28 patients completed the study. Patients in the active group received anodal stimulation over the DLPFC, while patients in the sham group received placebo stimulation (20 min/day, 5 days/week, for 4 weeks). The level of consciousness among patients was assessed with the Coma Recovery Scale-Revised (CRS-R) at baseline and at the end of every week from the first to the fourth week.

RESULTS

The CRS-R scores of both the active and sham groups showed a consistent increasing trend over time; however, the treatment effect of the active group was better than that of the sham group. In addition, there was a statistically significant difference in the total CRS-R score between the two groups at weeks 1, 2, 3 and 4. Moreover, 10 patients (71.4%) in the active group and 3 patients (21.4%) in the sham group were regarded as responders.

CONCLUSION

Long-term tDCS could improve the level of consciousness of patients with DOC in the subacute stage.

Wireless Deep Brain Stimulation by Ultrasound-Responsive Molecular Piezoelectric Nanogenerators

Implantable neural stimulation devices are becoming prevalent in bioelectronic medicine for the precise treatment of various clinical diseases. Nevertheless, the limited lifespan and buckling size of the implanted devices remain significant obstacles for chronic clinical application. In this study, we developed an ultrasound-driven battery-free neurostimulator based on a high-performance mini-sized nanogenerator and demonstrated its successful application for the deep-brain-stimulation (DBS) therapy of Parkinson's disease in a rat model. This soft piezoelectric-triboelectric hybrid nanogenerators (PTNG) are made of porous thin-films of molecular piezoelectric materials, which have great advantages of facile, scalable, low-temperature, and flexible processing. Without any bucky accessory control circuits, the subcutaneously implanted soft PTNG can function as a wirelessly powered neurostimulator, allowing for the adjustment of stimulation parameters through external programmable ultrasound pulses. This DBS electroceutical application of energy-harvesting thin-film devices based on molecular piezoelectric materials provides valuable insight into the development of a soft high-performance bioelectronic device.

Transcranial burst electrical stimulation contributes to neuromodulatory effects in the rat motor cortex

Background and objective

Transcranial Burst Electrical Stimulation (tBES) is an innovative non-invasive brain stimulation technique that combines direct current (DC) and theta burst stimulation (TBS) for brain neuromodulation. It has been suggested that the tBES protocol may efficiently induce neuroplasticity. However, few studies have systematically tested neuromodulatory effects and underlying neurophysiological mechanisms by manipulating the polarity of DC and TBS patterns. This study aimed to develop the platform and assess neuromodulatory effects and neuronal activity changes following tBES.

Methods

Five groups of rats were exposed to anodal DC combined with intermittent TBS (tBES+), cathodal DC combined with continuous TBS (tBES-), anodal and cathodal transcranial direct current stimulation (tDCS+ and tDCS-), and sham groups. The neuromodulatory effects of each stimulation on motor cortical excitability were analyzed by motor-evoked potentials (MEPs) changes. We also investigated the effects of tBES on both excitatory and inhibitory neural biomarkers. We specifically examined c-Fos and glutamic acid decarboxylase (GAD-65) using immunohistochemistry staining techniques. Additionally, we evaluated the safety of tBES by analyzing glial fibrillary acidic protein (GFAP) expression.

Results

Our findings demonstrated significant impacts of tBES on motor cortical excitability up to 30 min post-stimulation. Specifically, MEPs significantly increased after tBES (+) compared to pre-stimulation (p = 0.026) and sham condition (p = 0.025). Conversely, tBES (-) led to a notable decrease in MEPs relative to baseline (p = 0.04) and sham condition (p = 0.048). Although tBES showed a more favorable neuromodulatory effect than tDCS, statistical analysis revealed no significant differences between these two groups (p > 0.05). Additionally, tBES (+) exhibited a significant activation of excitatory neurons, indicated by increased c-Fos expression (p < 0.05), and a reduction in GAD-65 density (p < 0.05). tBES (-) promoted GAD-65 expression (p < 0.05) while inhibiting c-Fos activation (p < 0.05), suggesting the involvement of cortical inhibition with tBES (-). The expression of GFAP showed no significant difference between tBES and sham conditions (p > 0.05), indicating that tBES did not induce neural injury in the stimulated regions.

Conclusion

Our study indicates that tBES effectively modulates motor cortical excitability. This research significantly contributes to a better understanding of the neuromodulatory effects of tBES, and could provide valuable evidence for its potential clinical applications in treating neurological disorders.

Band-Specific Altered Cortical Connectivity in Early Parkinson's Disease and its Clinical Correlates

BACKGROUND

Functional connectivity (FC) has shown promising results in assessing the pathophysiology and identifying early biomarkers of neurodegenerative disorders, such as Parkinson's disease (PD).

OBJECTIVES

In this study, we aimed to assess possible resting-state FC abnormalities in early-stage PD patients using high-density electroencephalography (EEG) and to detect their clinical relationship with motor and non-motor PD symptoms.

METHODS

We enrolled 26 early-stage levodopa naïve PD patients and a group of 20 healthy controls (HC). Data were recorded with 64-channels EEG system and a source-reconstruction method was used to identify brain-region activity. FC was calculated using the weighted phase-lag index in θ, α, and β bands. Additionally, we quantified the unbalancing between β and lower frequencies through a novel index (β-functional ratio [FR]). Statistical analysis was conducted using a network-based statistical approach.

RESULTS

PD patients showed hypoconnected networks in θ and α band, involving prefrontal-limbic-temporal and frontoparietal areas, respectively, and a hyperconnected network in the β frequency band, involving sensorimotor-frontal areas. The θ FC network was negatively related to Non-Motor Symptoms Scale scores and α FC to the Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale part III gait subscore, whereas β FC and β-FR network were positively linked to the bradykinesia subscore. Changes in θ FC and β-FR showed substantial reliability and high accuracy, precision, sensitivity, and specificity in discriminating PD and HC.

CONCLUSIONS

Frequency-specific FC changes in PD likely reflect the dysfunction of distinct cortical networks, which occur from the early stage of the disease. These abnormalities are involved in the pathophysiology of specific motor and non-motor PD symptoms, including gait, bradykinesia, mood, and cognition. © 2023 International Parkinson and Movement Disorder Society.

Astrocyte Responses Influence Local Effects of Whole-Brain Magnetic Stimulation in Parkinsonian Rats

BACKGROUND

Excessive glutamatergic transmission in the striatum is implicated in Parkinson's disease (PD) progression. Astrocytes maintain glutamate homeostasis, protecting from excitotoxicity through the glutamate-aspartate transporter (GLAST), whose alterations have been reported in PD. Noninvasive brain stimulation using intermittent theta-burst stimulation (iTBS) acts on striatal neurons and glia, inducing neuromodulatory effects and functional recovery in experimental parkinsonism.

OBJECTIVE

Because PD is associated with altered astrocyte function, we hypothesized that acute iTBS, known to rescue striatal glutamatergic transmission, exerts regional- and cell-specific effects through modulation of glial functions.

METHODS

6-Hydroxydopamine-lesioned rats were exposed to acute iTBS, and the areas predicted to be more responsive by a biophysical, hyper-realistic computational model that faithfully reconstructs the experimental setting were analyzed. The effects of iTBS on glial cells and motor behavior were evaluated by molecular and morphological analyses, and CatWalk and Stepping test, respectively.

RESULTS

As predicted by the model, the hippocampus, cerebellum, and striatum displayed a marked c-FOS activation after iTBS, with the striatum showing specific morphological and molecular changes in the astrocytes, decreased phospho-CREB levels, and recovery of GLAST. Striatal-dependent motor performances were also significantly improved.

CONCLUSION

These data uncover an unknown iTBS effect on astrocytes, advancing the understanding of the complex mechanisms involved in TMS-mediated functional recovery. Data on numerical dosimetry, obtained with a degree of anatomical details never before considered and validated by the biological findings, provide a framework to predict the electric-field induced in different specific brain areas and associate it with functional and molecular changes. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Effect of Physiotherapy Interventions on Motor Symptoms in People With Parkinson's Disease: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the effectiveness of different types of physiotherapy interventions in people with Parkinson's disease (PD).

DESIGN

Systematic review and meta-analysis of randomized controlled trials (RCTs).

METHODS

Five databases (PubMed, Embase, Cochrane Library, CINAHL and Web of Science Core Collection) were searched for relevant RCTs published from database inception to July 14, 2022. Reviewers independently screened the literature, extracted data, and assessed the literature quality according to the Cochrane Collaboration Risk of Bias Tool and PEDro Scale. This meta-analysis was conducted using RevMan 5.4.1 and reported in compliance with the PRISMA statement.

RESULTS

Forty-two RCTs with 2,530 participants were included. Across all types of physiotherapy, strength training, mind-body exercise, aerobic exercise, and non-invasive brain stimulation (NiBS) were effective in improving motor symptoms as measured by the (Movement Disorders Society-) Unified PD Scale, whereas balance and gait training (BGT) and acupuncture were not. The pooled results showed that the change in mind-body exercise (MD = -5.36, 95% CI [-7.97 to -2.74], p < .01, I2 = 68%) and NiBS (MD = -4.59, 95% CI [-8.59 to -0.59], p = .02, I2 = 78%) reached clinical threshold, indicating clinically meaningful improvements. Considering the effectiveness of the interventions on motor symptoms, balance, gait and functional mobility, mind-body exercise was recommended the most.

CONCLUSIONS

Exercise appears to be a better form of physiotherapy than NiBS and acupuncture for improving motor function. Mind-body exercise showed beneficial effects on motor symptoms, balance, gait and functional mobility in people with PD, and is worthy of being promoted.

Comparative motor effectiveness of non-invasive brain stimulation techniques in patients with Parkinson's disease: A network meta-analysis

BACKGROUND

Although noninvasive brain stimulation (NIBS) techniques are an effective alternative treatment option, their relative effects in patients with Parkinson's disease (PD) remain undefined. Here, we aimed to compare motor efficacy of the NIBS techniques in PD.

METHODS

We carried out an electronic search in PubMed, Embase, Cochrane Library, CINAHL, PEDro and PsycINFO (accessed via Ovid) for articles published until August 2022. The treatment efficacy of motor function was quantified by the Unified Parkinson's disease rating scale part III.

RESULTS

28 randomized controlled trials with parallel group were included in the analysis, enrolling 1057 patients. In the "on" state, high-frequency repetitive transcranial magnetic stimulation (HFrTMS) conferred better short-term and long-term efficacy compared to transcranial direct current stimulation. Surface under the cumulative ranking curve rank showed that HFrTMS combined with transcranial direct current stimulation and low-frequency TMS ranked first among PD in improving motor function. In the "off" state, there were no significant differences in most of the treatments, but surface under the cumulative ranking curve rank showed that continuous theta burst stimulation and low-frequency TMS had the highest short- and long-term effect in improving motor function.

CONCLUSION

HFrTMS is an effective intervention in improving motor function. Besides, its combination with another NIBS technique produces better therapeutic effects in the "on" state.

Trial protocol: Feasibility of neuromodulation with connectivity-guided intermittent theta-burst stimulation for improving cognition in multiple sclerosis

Cognitive impairment in multiple sclerosis (MS) can adversely impact participation in employment, activities of daily living, and wider society. It affects 40-70% of people living with MS (pwMS). There are few effective treatments for cognitive impairment in people with MS. Neuromodulation with intermittent theta-burst stimulation (iTBS) has potential for treating cognitive impairment in pwMS. This single-centre mixed-methods feasibility randomised controlled trial (NCT04931953) will assess feasibility, acceptability, and tolerability of procedures used for applying iTBS for improving cognitive performance in pwMS. Participants will be randomised into three intervention groups with varying lengths of iTBS treatment (from 1 to 4 weeks) and a sham-control group. Quantitative data will be collected at three time points (baseline, end of intervention, and 8-week follow-up). End of the intervention semi-structured interviews will explore the views and experiences of the participants receiving the intervention, analysed using framework analysis. Quantitative and qualitative data will be synthesised to explore the impact of the iTBS intervention. Ethical approval has been received from the Health Research Authority (21/LO/0506) and recruitment started in June 2022. The results will inform the design of an RCT of the efficacy of iTBS as a therapeutic intervention for cognitive impairment in pwMS.

Transcranial direct current stimulation suggests not improving postural control during adapted tandem position in people with Parkinson's disease: A pilot study

BACKGROUND

Balance impairments in people with Parkinson's disease (PD) demonstrated mainly in challenging postural tasks, such as increased body oscillation may be attributed to the deficits in the brain structures functionality involved in postural control (e.g., motor cortex, midbrain, and brainstem). Although promising results, the effect of transcranial direct current stimulation (tDCS) on postural control in people with PD is unclear, especially in objective measures such as the center of pressure (CoP) parameters. Thus, we analyzed the effects of a single session of tDCS on the CoP parameters during the adapted tandem position in people with PD.

METHODS

Nineteen people with PD participated in this crossover, randomized, and double-blind study. Anodal tDCS was applied over the primary motor cortex in two conditions of stimulation (2 mA/active and sham) on two different days for 20 min immediately before the postural control evaluation. Participants remained standing in an adapted tandem position for the postural control assessment for 30 s (three trials). CoP parameters were acquired by a force plate.

RESULTS

No significant differences were demonstrated between stimulation conditions (p-value range = 0.15-0.89).

CONCLUSIONS

Our results suggested that a single session of tDCS with 2 mA does not improve the postural control of people with PD during adapted tandem.

Spatiotemporal parameters during turning gait maneuvers of different amplitudes in young and elderly healthy adults: A descriptive and comparative study

BACKGROUND

Turning during walking adds complexity to gait and has been little investigated until now. Research question What are the differences in spatiotemporal parameters between young and elderly healthy adults performing quarter-turns (90°), half-turns (180°) and full-turns (360°)?

METHODS

The spatiotemporal parameters of 10 young and 10 elderly adults were recorded in a laboratory while turning at 90°, 180° and 360°. Two-way mixed ANOVA were performed to determine the effect of age and turning amplitude.

RESULTS

Elderly were slower and needed more steps and time to perform turns of larger amplitude than young adults. Cadence did not differ across age or across turning amplitude. Generally, in the elderly, the spatial parameters were smaller and the temporal parameters enhancing stability (i.e., double-support phase and stance/cycle ratio) were larger, especially for turns of larger amplitudes. In elderly adults, the variability of some spatial parameters was decreased, whereas the variability of some temporal parameters was increased. Stride width of the external leg showed the most substantial difference between groups. Most parameters differed between turning at 90° and turning at larger amplitudes (180°, 360°). Significance This study extends the characterization of turning biomechanics with respect to ageing. It also suggested paying particular attention to the turning amplitude. Finally, the age-related differences may pave the way for new selective rehabilitation protocols in the elderly.

Neuroprotection and Non-Invasive Brain Stimulation: Facts or Fiction?

Non-Invasive Brain Stimulation (NIBS) techniques, such as transcranial Direct Current Stimulation (tDCS) and repetitive Magnetic Transcranial Stimulation (rTMS), are well-known non-pharmacological approaches to improve both motor and non-motor symptoms in patients with neurodegenerative disorders. Their use is of particular interest especially for the treatment of cognitive impairment in Alzheimer's Disease (AD), as well as axial disturbances in Parkinson's (PD), where conventional pharmacological therapies show very mild and short-lasting effects. However, their ability to interfere with disease progression over time is not well understood; recent evidence suggests that NIBS may have a neuroprotective effect, thus slowing disease progression and modulating the aggregation state of pathological proteins. In this narrative review, we gather current knowledge about neuroprotection and NIBS in neurodegenerative diseases (i.e., PD and AD), just mentioning the few results related to stroke. As further matter of debate, we discuss similarities and differences with Deep Brain Stimulation (DBS)-induced neuroprotective effects, and highlight possible future directions for ongoing clinical studies.

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.

Boosting psychological change: Combining non-invasive brain stimulation with psychotherapy

Mental health disorders and substance use disorders are a leading cause of morbidity and mortality worldwide, and one of the most important challenges for public health systems. While evidence-based psychotherapy is generally pursued to address mental health challenges, psychological change is often hampered by non-adherence to treatments, relapses, and practical barriers (e.g., time, cost). In recent decades, Non-invasive brain stimulation (NIBS) techniques have emerged as promising tools to directly target dysfunctional neural circuitry and promote long-lasting plastic changes. While the therapeutic efficacy of NIBS protocols for mental illnesses has been established, neuromodulatory interventions might also be employed to support the processes activated by psychotherapy. Indeed, combining psychotherapy with NIBS might help tailor the treatment to the patient's unique characteristics and therapeutic goal, and would allow more direct control of the neuronal changes induced by therapy. Herein, we overview emerging evidence on the use of NIBS to enhance the psychotherapeutic effect, while highlighting the next steps in advancing clinical and research methods toward personalized intervention approaches.

Tremor in Parkinson's Disease: From Pathophysiology to Advanced Therapies

Background

Tremor is one of the most prevalent symptoms in Parkinson's Disease (PD). The progression and management of tremor in PD can be challenging, as response to dopaminergic agents might be relatively poor, particularly in patients with tremor-dominant PD compared to the akinetic/rigid subtype. In this review, we aim to highlight recent advances in the underlying pathogenesis and treatment modalities for tremor in PD.

Methods

A structured literature search through Embase was conducted using the terms "Parkinson's Disease" AND "tremor" OR "etiology" OR "management" OR "drug resistance" OR "therapy" OR "rehabilitation" OR "surgery." After initial screening, eligible articles were selected with a focus on published literature in the last 10 years.

Discussion

The underlying pathophysiology of tremor in PD remains complex and incompletely understood. Neurodegeneration of dopaminergic neurons in the retrorubral area, in addition to high-power neural oscillations in the cerebello-thalamo-cortical circuit and the basal ganglia, play a major role. Levodopa is the first-line therapeutic option for all motor symptoms, including tremor. The addition of dopamine agonists or anticholinergics can lead to further tremor reduction. Botulinum toxin injection is an effective alternative for patients with pharmacological-resistant tremor who are not seeking advanced therapies. Deep brain stimulation is the most well-established advanced therapy owing to its long-term efficacy, reversibility, and effectiveness in other motor symptoms and fluctuations. Magnetic resonance-guided focused ultrasound is a promising modality, which has the advantage of being incisionless. Cortical and peripheral electrical stimulation are non-invasive innovatory techniques that have demonstrated good efficacy in suppressing intractable tremor.

Taming non-stationary chimera states in locally coupled oscillators

The imperfect traveling chimera (ITC) state is a novel non-stationary chimera pattern in which the incoherent domain of oscillators spreads into the coherent domain. We investigate the ITC state in locally coupled pendulum oscillators with heterogeneous driving forces. We introduce the heterogeneous phase value in the driving forces by two different ways, namely, the random phase from uniform distribution and random phase directions with identical amplitude. We discover two transition mechanisms from ITC to coherent state through traveling chimera-like state by taking the two different phase heterogeneity. The transition phenomena are investigated using cylindrical and polar coordinate phase spaces. In the numerical study, we propose a quantitative measurement named "spatiotemporal consistency" strength for distinguishing the ITC from the traveling one. Our research facilitates the exploration of potential applications of heterogeneous interactions in neuroscience.

Update on Parkinson's Disease Rehabilitation

Parkinson's disease (PD) is the second most common neurodegenerative disorder. Although dopaminergic drugs are the mainstay for improving PD symptoms, there are still few effective disease-modifying therapies. With the increasing prevalence of PD and the rapid transition to an aging society, more emphasis needs to be placed on rehabilitation that could slow the disease progression combined with pharmacological therapy. In this review, we present an update on evidence related to rehabilitation programs for motor function, swallowing difficulty, and speech disorders in PD. Aerobic exercise, music therapy, dance, virtual reality, and non-invasive brain stimulation have been shown to improve motor function, and telerehabilitation could also be feasibly applied in PD. Recent studies have shown the effectiveness of expiratory muscle strengthening exercises and Lee Silverman Voice Treatment for swallowing difficulty and speech disorders, respectively. Although many rehabilitation programs have been tried, the evidence is still limited. Well-designed future randomized controlled trials with large numbers of participants are needed to establish evidence for rehabilitation in PD.

Towards therapeutic non-invasive electrical modulation of brain circuits in Parkinson's disease

This scientific commentary refers to ‘Driving motor cortex oscillations modulates bradykinesia in Parkinson’s disease’ by Guerra et al. (doi: 10.1093/brain/awab257).

Can Transcranial Electrical Stimulation Facilitate Post-stroke Cognitive Rehabilitation? A Systematic Review and Meta-Analysis

Background

Non-invasive brain stimulation methods have been widely utilized in research settings to manipulate and understand the functioning of the human brain. In the last two decades, transcranial electrical stimulation (tES) has opened new doors for treating impairments caused by various neurological disorders. However, tES studies have shown inconsistent results in post-stroke cognitive rehabilitation, and there is no consensus on the effectiveness of tES devices in improving cognitive skills after the onset of stroke.

Objectives

We aim to systematically investigate the efficacy of tES in improving post-stroke global cognition, attention, working memory, executive functions, visual neglect, and verbal fluency. Furthermore, we aim to provide a pathway to an effective use of stimulation paradigms in future studies.

Methods

Preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines were followed. Randomized controlled trials (RCTs) were systematically searched in four different databases, including Medline, Embase, Pubmed, and PsychInfo. Studies utilizing any tES methods published in English were considered for inclusion. Standardized mean difference (SMD) for each cognitive domain was used as the primary outcome measure.

Results

The meta-analysis includes 19 studies assessing at least one of the six cognitive domains. Five RCTs studying global cognition, three assessing visual neglect, five evaluating working memory, three assessing attention, and nine studies focusing on aphasia were included for meta-analysis. As informed by the quantitative analysis of the included studies, the results favor the efficacy of tES in acute improvement in aphasic deficits (SMD = 0.34, CI = 0.02-0.67, p = 0.04) and attention deficits (SMD = 0.59, CI = -0.05-1.22, p = 0.07), however, no improvement was observed in any other cognitive domains.

Conclusion

The results favor the efficacy of tES in an improvement in aphasia and attentive deficits in stroke patients in acute, subacute, and chronic stages. However, the outcome of tES cannot be generalized across cognitive domains. The difference in the stimulation montages and parameters, diverse cognitive batteries, and variable number of training sessions may have contributed to the inconsistency in the outcome. We suggest that in future studies, experimental designs should be further refined, and standardized stimulation protocols should be utilized to better understand the therapeutic effect of stimulation.

Perspectives on Rehabilitation Using Non-invasive Brain Stimulation Based on Second-Person Neuroscience of Teaching-Learning Interactions

Recent advances in second-person neuroscience have allowed the underlying neural mechanisms involved in teaching-learning interactions to be better understood. Teaching is not merely a one-way transfer of information from teacher to student; it is a complex interaction that requires metacognitive and mentalizing skills to understand others’ intentions and integrate information regarding oneself and others. Physiotherapy involving therapists instructing patients on how to improve their motor skills is a clinical field in which teaching-learning interactions play a central role. Accumulating evidence suggests that non-invasive brain stimulation (NIBS) modulates cognitive functions; however, NIBS approaches to teaching-learning interactions are yet to be utilized in rehabilitation. In this review, I evaluate the present research into NIBS and its role in enhancing metacognitive and mentalizing abilities; I then review hyperscanning studies of teaching-learning interactions and explore the potential clinical applications of NIBS in rehabilitation. Dual-brain stimulation using NIBS has been developed based on findings of brain-to-brain synchrony in hyperscanning studies, and it is delivered simultaneously to two individuals to increase inter-brain synchronized oscillations at the stimulated frequency. Artificial induction of brain-to-brain synchrony has the potential to promote instruction-based learning. The brain-to-brain interface, which induces inter-brain synchronization by adjusting the patient’s brain activity, using NIBS, to the therapist’s brain activity, could have a positive effect on both therapist-patient interactions and rehabilitation outcomes. NIBS based on second-person neuroscience has the potential to serve as a useful addition to the current neuroscientific methods used in complementary interventions for rehabilitation.

Noninvasive neuromodulation in Parkinson's disease: Neuroplasticity implication and therapeutic perspectives

Noninvasive brain stimulation techniques can be used to study in vivo the changes of cortical activity and plasticity in subjects with Parkinson's disease (PD). Also, an increasing number of studies have suggested a potential therapeutic effect of these techniques. High-frequency repetitive transcranial magnetic stimulation (rTMS) and anodal transcranial direct current stimulation (tDCS) represent the most used stimulation paradigms to treat motor and nonmotor symptoms of PD. Both techniques can enhance cortical activity, compensating for its reduction related to subcortical dysfunction in PD. However, the use of suboptimal stimulation parameters can lead to therapeutic failure. Clinical studies are warranted to clarify in PD the additional effects of these stimulation techniques on pharmacologic and neurorehabilitation treatments.

The effect and safety of ropinirole in the treatment of Parkinson disease: A systematic review and meta-analysis

BACKGROUND

It is necessary to conduct a meta-analysis of the clinical randomized controlled trials (RCTs) on ropinirole in the treatment of Parkinson disease (PD), to explore the effects and safety of ropinirole, and to provide a theoretical basis for clinically safe and rational drug use.

METHODS

RCTs on the effectiveness and safety of ropinirole in the treatment of PD were searched. We searched Dutch medical literature database, Pubmed, Cochrane Library, China National Knowledge Infrastructure, Wanfang Knowledge Service Platform up to December 15, 2020. The Cochrane risk bias assessment tool was used to evaluate the quality of the included literature, and the RevMan5.3 software was used for meta-analysis.

RESULTS

A total of 12 RCTs with 3341 patients were included. The changes of Parkinson Disease Rating Scale Part II score (mean difference = -2.23, 95% confidence interval [CI] -2.82 to -1.64) and Parkinson Disease Rating Scale Part III scores (mean difference = -4.93, 95%CI -5.25 to -4.61) in the ropinirole group was significantly lower than that in the control group. The incidence of dizziness (odd risk [OR] = 1.85, 95%CI 1.50-2.28), nausea (OR = 2.17, 95%CI 1.81-2.59), vomiting (OR = 2.73, 95%CI 1.47-5.09), and lethargy (OR = 2.19, 95%CI 1.39-3.44) in the ropinirole group was significantly higher than that in the control group (all P < .05), and there were no significant differences in the incidence of headache (OR = 1.14, 95%CI 0.79-1.65) and insomnia (OR = 1.06, 95%CI 0.72-1.55) were found between 2 groups (all P > .05).

CONCLUSIONS

Ropinirole can help improve the ability of daily living and exercise function of PD patients, but it will increase the incidence of related adverse reactions, which needs to be further confirmed by subsequent large-scale, high-quality RCTs.

Motor Learning Based on Oscillatory Brain Activity Using Transcranial Alternating Current Stimulation: A Review

Developing effective tools and strategies to promote motor learning is a high-priority scientific and clinical goal. In particular, motor-related areas have been investigated as potential targets to facilitate motor learning by noninvasive brain stimulation (NIBS). In addition to shedding light on the relationship between motor function and oscillatory brain activity, transcranial alternating current stimulation (tACS), which can noninvasively entrain oscillatory brain activity and modulate oscillatory brain communication, has attracted attention as a possible technique to promote motor learning. This review focuses on the use of tACS to enhance motor learning through the manipulation of oscillatory brain activity and its potential clinical applications. We discuss a potential tACS-based approach to ameliorate motor deficits by correcting abnormal oscillatory brain activity and promoting appropriate oscillatory communication in patients after stroke or with Parkinson's disease. Interpersonal tACS approaches to manipulate intra- and inter-brain communication may result in pro-social effects and could promote the teaching-learning process during rehabilitation sessions with a therapist. The approach of re-establishing oscillatory brain communication through tACS could be effective for motor recovery and might eventually drive the design of new neurorehabilitation approaches based on motor learning.

Potential Non-invasive Brain Stimulation Targets to Alleviate Freezing of Gait in Parkinson's Disease

Freezing of gait (FOG) is a common motor symptom in Parkinson's disease (PD). Although FOG reduces quality of life, affects mobility and increases the risk of falls, there are little to no effective treatments to alleviate FOG. Non-invasive brain stimulation (NIBS) has recently yielded attention as a potential treatment to reduce FOG symptoms however, stimulation parameters and protocols remain inconsistent and require further research. Specifically, targets for stimulation require careful review. Thus, with current neuroimaging and neuro-electrophysiological evidence, we consider potential cortical targets thought to be involved in the pathophysiology of FOG according to the Interference model, and within reach of NIBS. We note that the primary motor cortex, the supplementary motor area and the dorsolateral prefrontal cortex have already drawn attention as NIBS targets for FOG, but based on neuroimaging evidence the premotor cortex, the medial prefrontal cortex, the cerebellum, and more particularly, the posterior parietal cortex should be considered as potential regions for stimulation. We also discuss different methodological considerations, such as stimulation type, medication state, and hemisphere to target, and future perspectives for NIBS protocols in FOG.

Frontal Transcranial Direct Current Stimulation as a Potential Treatment of Parkinson's Disease-Related Fatigue

In contrast to motor symptoms, non-motor symptoms in Parkinson’s disease (PD) are often poorly recognized and inadequately treated. Fatigue is one of the most common non-motor symptoms in PD and affects a broad range of everyday activities, causes disability, and substantially reduces the quality of life. It occurs at every stage of PD, and once present, it often persists and worsens over time. PD patients attending the 2013 World Parkinson Congress voted fatigue as the leading symptom in need of further research. However, despite its clinical significance, little progress has been made in understanding the causes of Parkinson’s disease-related fatigue (PDRF) and developing effective treatment options, which argues strongly for a greater effort. Transcranial direct current stimulation (tDCS) is a technique to non-invasively modulate cortical excitability by delivering low electrical currents to the cerebral cortex. In the past, it has been consistently evidenced that tDCS has the ability to induce neuromodulatory changes in the motor, sensory, and cognitive domains. Importantly, recent data present tDCS over the frontal cortex as an effective therapeutic option to treat fatigue in patients suffering from multiple sclerosis (MS). The current opinion paper reviews recent data on PDRF and the application of tDCS for the treatment of fatigue in neuropsychiatric disorders to further develop an idea of using frontal anodal tDCS as a potential therapeutic strategy to alleviate one of the most common and severe non-motor symptoms of PD.