Non-invasive brain stimulation for Parkinson's disease: a systematic review and meta-analysis of the literature

Randomized trial of transcranial direct current stimulation for poststroke dysphagia

OBJECTIVE

We evaluated whether transcranial direct current stimulation (tDCS) is able to enhance dysphagia rehabilitation following stroke. Besides relating clinical effects with neuroplastic changes in cortical swallowing processing, we aimed to identify factors influencing treatment success.

METHODS

In this double-blind, randomized study, 60 acute dysphagic stroke patients received contralesional anodal (1mA, 20 minutes) or sham tDCS on 4 consecutive days. Swallowing function was thoroughly assessed before and after the intervention using the validated Fiberoptic Endoscopic Dysphagia Severity Scale (FEDSS) and clinical assessment. In 10 patients, swallowing-related brain activation was recorded applying magnetoencephalography before and after the intervention. Voxel-based statistical lesion pattern analysis was also performed.

RESULTS

Study groups did not differ according to demographic data, stroke characteristics, or baseline dysphagia severity. Patients treated with tDCS showed greater improvement in FEDSS than the sham group (1.3 vs 0.4 points, mean difference = 0.9, 95% confidence interval [CI] = 0.4-1.4, p < 0.0005). Functional recovery was accompanied by a significant increase of activation (p < 0.05) in the contralesional swallowing network after real but not sham tDCS. Regarding predictors of treatment success, for every hour earlier that treatment was initiated, there was greater improvement on the FEDSS (adjusted odds ratio = 0.99, 95% CI = 0.98-1.00, p < 0.05) in multivariate analysis. Stroke location in the right insula and operculum was indicative of worse response to tDCS (p < 0.05).

INTERPRETATION

Application of tDCS over the contralesional swallowing motor cortex supports swallowing network reorganization, thereby leading to faster rehabilitation of acute poststroke dysphagia. Early treatment initiation seems beneficial. tDCS may be less effective in right-hemispheric insulo-opercular stroke. Ann Neurol 2018;83:328-340.

Cortical neuromodulation for neuropathic pain and Parkinson disease: Where are we?

Cortex neuromodulation is promising approach for treatment of some neurological conditions, especially neuropathic pain and Parkinson's disease. Effects of non-invasive cortical stimulation are short lived; transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) may be useful to assess the suitability for invasive cortical stimulation. Direct cortical stimulation (DCS) is the method able to provide long-lasting effects in treatment of neuropathic pain and some symptoms of Parkinson's disease through the use of totally implantable systems that ensure a chronic stimulation.

Does non-invasive brain stimulation modify hand dexterity? Protocol for a systematic review and meta-analysis

INTRODUCTION

Dexterity is described as coordinated hand and finger movement for precision tasks. It is essential for day-to-day activities like computer use, writing or buttoning a shirt. Integrity of brain motor networks is crucial to properly execute these fine hand tasks. When these networks are damaged, interventions to enhance recovery are frequently accompanied by unwanted side effects or limited in their effect. Non-invasive brain stimulation (NIBS) are postulated to target affected motor areas and improve hand motor function with few side effects. However, the results across studies vary, and the current literature does not allow us to draw clear conclusions on the use of NIBS to promote hand function recovery. Therefore, we developed a protocol for a systematic review and meta-analysis on the effects of different NIBS technologies on dexterity in diverse populations. This study will potentially help future evidence-based research and guidelines that use these NIBS technologies for recovering hand dexterity.

METHODS AND ANALYSIS

This protocol will compare the effects of active versus sham NIBS on precise hand activity. Records will be obtained by searching relevant databases. Included articles will be randomised clinical trials in adults, testing the therapeutic effects of NIBS on continuous dexterity data. Records will be studied for risk of bias. Narrative and quantitative synthesis will be done.

ETHICS AND DISSEMINATION

No private health information is included; the study is not interventional. Ethical approval is not required. The results will be reported in a peer-review journal.

REGISTRATION DETAILS

PROSPERO International prospective register of systematic reviews registration number: CRD42016043809.

Noninvasive Brain Stimulation and Personal Identity: Ethical Considerations

As noninvasive brain stimulation (NIBS) technology advances, these methods may become increasingly capable of influencing complex networks of mental functioning. We suggest that these might include cognitive and affective processes underlying personality and belief systems, which would raise important questions concerning personal identity and autonomy. We give particular attention to the relationship between personal identity and belief, emphasizing the importance of respecting users' personal values. We posit that research participants and patients should be encouraged to take an active approach to considering the personal implications of altering their own cognition, particularly in cases of neurocognitive "enhancement." We suggest that efforts to encourage careful consideration through the informed consent process would contribute usefully to studies and treatments that use NIBS.

Comparison of the induced fields using different coil configurations during deep transcranial magnetic stimulation

Stimulation of deeper brain structures by transcranial magnetic stimulation (TMS) plays a role in the study of reward and motivation mechanisms, which may be beneficial in the treatment of several neurological and psychiatric disorders. However, electric field distributions induced in the brain by deep transcranial magnetic stimulation (dTMS) are still unknown. In this paper, the double cone coil, H-coil and Halo-circular assembly (HCA) coil which have been proposed for dTMS have been numerically designed. The distributions of magnetic flux density, induced electric field in an anatomically based realistic head model by applying the dTMS coils were numerically calculated by the impedance method. Results were compared with that of standard figure-of-eight (Fo8) coil. Simulation results show that double cone, H- and HCA coils have significantly deep field penetration compared to the conventional Fo8 coil, at the expense of induced higher and wider spread electrical fields in superficial cortical regions. Double cone and HCA coils have better ability to stimulate deep brain subregions compared to that of the H-coil. In the mean time, both double cone and HCA coils increase risk for optical nerve excitation. Our results suggest although the dTMS coils offer new tool with potential for both research and clinical applications for psychiatric and neurological disorders associated with dysfunctions of deep brain regions, the selection of the most suitable coil settings for a specific clinical application should be based on a balanced evaluation between stimulation depth and focality.

Motor learning in animal models of Parkinson's disease: Aberrant synaptic plasticity in the motor cortex

In Parkinson's disease (PD), dopamine depletion causes major changes in the brain, resulting in the typical cardinal motor features of the disease. PD neuropathology has been restricted to postmortem examinations, which are limited to only a single time of PD progression. Models of PD in which dopamine tone in the brain is chemically or physically disrupted are valuable tools in understanding the mechanisms of the disease. The basal ganglia have been well studied in the context of PD, and circuit changes in response to dopamine loss have been linked to the motor dysfunctions in PD. However, the etiology of the cognitive dysfunctions that are comorbid in PD patients has remained unclear until now. In this article, we review recent studies exploring how dopamine depletion affects the motor cortex at the synaptic level. In particular, we highlight our recent findings on abnormal spine dynamics in the motor cortex of PD mouse models through in vivo time-lapse imaging and motor skill behavior assays. In combination with previous studies, a role of the motor cortex in skill learning and the impairment of this ability with the loss of dopamine are becoming more apparent. Taken together, we conclude with a discussion on the potential role for the motor cortex in PD, with the possibility of targeting the motor cortex for future PD therapeutics. © 2017 International Parkinson and Movement Disorder Society.

Transcranial direct current stimulation associated with gait training in Parkinson's disease: A pilot randomized clinical trial

OBJECTIVE

The aim of this study is to investigate the effects of transcranial direct current stimulation (tDCS) combined with cueing gait training (CGT) on functional mobility in patients with Parkinson´s disease (PD).

METHODS

A pilot double-blind controlled, randomized clinical trial was conducted with 22 patients with PD assigned to the experimental (anodal tDCS plus CGT) and control group (sham tDCS plus CGT). The primary outcome (functional mobility) was assessed by 10-m walk test, cadence, stride length, and Timed Up and Go test. Motor impairment, bradykinesia, balance, and quality of life were analyzed as secondary outcomes. Minimal clinically important differences (MCIDs) were observed when assessing outcome data.

RESULTS

Both groups demonstrated similar gains in all outcome measures, except for the stride length. The number of participants who showed MCID was similar between groups.

CONCLUSION

The CGT provided many benefits to functional mobility, motor impairment, bradykinesia, balance, and quality of life. However, these effect magnitudes were not influenced by stimulation, but tDCS seems to prolong the effects of cueing therapy on functional mobility.

Safety of Transcranial Magnetic Stimulation in Children: A Systematic Review of the Literature

BACKGROUND

Data and best practice recommendations for transcranial magnetic stimulation (TMS) use in adults are largely available. Although there are fewer data in pediatric populations and no published guidelines, its practice in children continues to grow.

METHODS

We performed a literature search through PubMed to review all TMS studies from 1985 to 2016 involving children and documented any adverse events. Crude risks were calculated per session.

RESULTS

Following data screening we identified 42 single-pulse and/or paired-pulse TMS studies involving 639 healthy children, 482 children with central nervous system disorders, and 84 children with epilepsy. Adverse events occurred at rates of 3.42%, 5.97%, and 4.55% respective to population and number of sessions. We also report 23 repetitive TMS studies involving 230 central nervous system and 24 children with epilepsy with adverse event rates of 3.78% and 0.0%, respectively. We finally identified three theta-burst stimulation studies involving 90 healthy children, 40 children with central nervous system disorder, and no epileptic children, with adverse event rates of 9.78% and 10.11%, respectively. Three seizures were found to have occurred in central nervous system disorder individuals during repetitive TMS, with a risk of 0.14% per session. There was no significant difference in frequency of adverse events by group (P = 0.988) or modality (P = 0.928).

CONCLUSIONS

Available data suggest that risk from TMS/theta-burst stimulation in children is similar to adults. We recommend that TMS users in this population follow the most recent adult safety guidelines until sufficient data are available for pediatric specific guidelines. We also encourage continued surveillance through surveys and assessments on a session basis.

Multifocal repetitive TMS for motor and mood symptoms of Parkinson disease: A randomized trial

OBJECTIVE

To assess whether multifocal, high-frequency repetitive transcranial magnetic stimulation (rTMS) of motor and prefrontal cortex benefits motor and mood symptoms in patients with Parkinson disease (PD).

METHODS

Patients with PD and depression were enrolled in this multicenter, double-blind, sham-controlled, parallel-group study of real or realistic (electric) sham rTMS. Patients were randomized to 1 of 4 groups: bilateral M1 ( + sham dorsolateral prefrontal cortex [DLPFC]), DLPFC ( + sham M1), M1 + DLPFC, or double sham. The TMS course consisted of 10 daily sessions of 2,000 stimuli for the left DLPFC and 1,000 stimuli for each M1 (50 × 4-second trains of 40 stimuli at 10 Hz). Patients were evaluated at baseline, at 1 week, and at 1, 3, and 6 months after treatment. Primary endpoints were changes in motor function assessed with the Unified Parkinson's Disease Rating Scale-III and in mood with the Hamilton Depression Rating Scale at 1 month.

RESULTS

Of the 160 patients planned for recruitment, 85 were screened, 61 were randomized, and 50 completed all study visits. Real M1 rTMS resulted in greater improvement in motor function than sham at the primary endpoint (p < 0.05). There was no improvement in mood in the DLPFC group compared to the double-sham group, as well as no benefit to combining M1 and DLPFC stimulation for either motor or mood symptoms.

CONCLUSIONS

In patients with PD with depression, M1 rTMS is an effective treatment of motor symptoms, while mood benefit after 2 weeks of DLPFC rTMS is not better than sham. Targeting both M1 and DLPFC in each rTMS session showed no evidence of synergistic effects.

CLINICALTRIALSGOV IDENTIFIER

NCT01080794.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that in patients with PD with depression, M1 rTMS leads to improvement in motor function while DLPFC rTMS does not lead to improvement in depression compared to sham rTMS.

The Role of Primary Motor Cortex (M1) Glutamate and GABA Signaling in l-DOPA-Induced Dyskinesia in Parkinsonian Rats

Long-term treatment of Parkinson's disease with l-DOPA almost always leads to the development of involuntary movements termed l-DOPA-induced dyskinesia. Whereas hyperdopaminergic signaling in the basal ganglia is thought to cause dyskinesia, alterations in primary motor cortex (M1) activity are also prominent during dyskinesia, suggesting that the cortex may represent a therapeutic target. The present study used the rat unilateral 6-hydroxydopamine lesion model of Parkinson's disease to characterize in vivo changes in GABA and glutamate neurotransmission within M1 and determine their contribution to behavioral output. 6-Hydroxydopamine lesion led to parkinsonian motor impairment that was partially reversed by l-DOPA. Among sham-lesioned rats, l-DOPA did not change glutamate or GABA efflux. Likewise, 6-hydroxydopamine lesion did not impact GABA or glutamate among rats chronically treated with saline. However, we observed an interaction of lesion and treatment whereby, among lesioned rats, l-DOPA given acutely (1 d) or chronically (14-16 d) reduced glutamate efflux and enhanced GABA efflux. Site-specific microinjections into M1 demonstrated that l-DOPA-induced dyskinesia was reduced by M1 infusion of a D1 antagonist, an AMPA antagonist, or a GABAA agonist. Overall, the present study demonstrates that l-DOPA-induced dyskinesia is associated with increased M1 inhibition and that exogenously enhancing M1 inhibition may attenuate dyskinesia, findings that are in agreement with functional imaging and transcranial magnetic stimulation studies in human Parkinson's disease patients. Together, our study suggests that increasing M1 inhibitory tone is an endogenous compensatory response designed to limit dyskinesia severity and that potentiating this response is a viable therapeutic strategy.

SIGNIFICANCE STATEMENT

Most Parkinson's disease patients will receive l-DOPA and eventually develop hyperkinetic involuntary movements termed dyskinesia. Such symptoms can be as debilitating as the disease itself. Although dyskinesia is associated with dynamic changes in primary motor cortex physiology, to date, there are no published studies investigating in vivo neurotransmitter release in M1 during dyskinesia. In parkinsonian rats, l-DOPA administration reduced M1 glutamate efflux and enhanced GABA efflux, coincident with the emergence of dyskinetic behaviors. Dyskinesia could be reduced by local M1 modulation of D1, AMPA, and GABAA receptors, providing preclinical support for the notion that exogenously blunting M1 signaling (pharmacologically or with cortical stimulation) is a therapeutic approach to the treatment of debilitating dyskinesias.

Freezing of gait in Parkinson's disease: from pathophysiology to emerging therapies

Freezing of gait (FOG) is 'an episodic inability to generate effective stepping in the absence of any known cause other than parkinsonism or high level gait disorders'. FOG is one of the most disabling symptoms in Parkinson's disease, especially in its more advanced stages. Early recognition is important as FOG is related to higher fall risk and poorer prognosis. Although specific treatments are still elusive, there have been recent advances in the development of new therapeutic approaches. The aim of this review is to present the latest knowledge regarding the phenomenology, pathogenesis, diagnostic assessment and conventional treatment of FOG in Parkinson's disease. A review of the evidence supporting noninvasive brain stimulation will follow to highlight the potential of these strategies.

Efficacy of cumulative high-frequency rTMS on freezing of gait in Parkinson's disease

Purpose: Freezing of gait (FOG) affects mobility and balance seriously. Few reports have investigated the effects of repetitive transcranial magnetic stimulation (rTMS) on FOG in Parkinson’s disease (PD). We investigated the efficacy of high-frequency rTMS for the treatment of FOG in PD.

Methods: Seventeen patients diagnosed with PD were recruited in a randomized, double-blinded, cross-over study. We applied high frequency rTMS (90% of resting motor threshold, 10 Hz, 1,000 pulses) over the lower leg primary motor cortex of the dominant hemisphere (M1-LL) for five sessions in a week. We also administered alternative sham stimulation with a two-week wash out period. The primary outcomes were measured before, immediately after, and one week after the intervention using the Standing Start 180° Turn Test (SS-180) with video analysis and the Freezing of Gait Questionnaire (FOG-Q). The secondary outcome measurements consisted of Timed Up and Go (TUG) tasks and the Unified Parkinson’s Disease Rating Scale part III (UPDRS-III). Motor cortical excitability was also evaluated.

Results: There were significant improvements in the step required to complete the SS-180 and FOG-Q in the rTMS condition compared to the sham condition, and the effects continued for a week. The TUG and UPDRS-III also showed significant ameliorations over time in the rTMS condition. The MEP amplitude at 120% resting motor threshold and intracortical facilitation also increased after real rTMS condition.

Conclusions: High frequency rTMS over the M1-LL may serve as an add-on therapy for improving FOG in PD.

Functional Magnetic Resonance Imaging Neurofeedback-guided Motor Imagery Training and Motor Training for Parkinson's Disease: Randomized Trial

OBJECTIVE

Real-time functional magnetic resonance imaging (rt-fMRI) neurofeedback (NF) uses feedback of the patient's own brain activity to self-regulate brain networks which in turn could lead to a change in behavior and clinical symptoms. The objective was to determine the effect of NF and motor training (MOT) alone on motor and non-motor functions in Parkinson's Disease (PD) in a 10-week small Phase I randomized controlled trial.

METHODS

Thirty patients with Parkinson's disease (PD; Hoehn and Yahr I-III) and no significant comorbidity took part in the trial with random allocation to two groups. Group 1 (NF: 15 patients) received rt-fMRI-NF with MOT. Group 2 (MOT: 15 patients) received MOT alone. The primary outcome measure was the Movement Disorder Society-Unified PD Rating Scale-Motor scale (MDS-UPDRS-MS), administered pre- and post-intervention "off-medication". The secondary outcome measures were the "on-medication" MDS-UPDRS, the PD Questionnaire-39, and quantitative motor assessments after 4 and 10 weeks.

RESULTS

Patients in the NF group were able to upregulate activity in the supplementary motor area (SMA) by using motor imagery. They improved by an average of 4.5 points on the MDS-UPDRS-MS in the "off-medication" state (95% confidence interval: -2.5 to -6.6), whereas the MOT group improved only by 1.9 points (95% confidence interval +3.2 to -6.8). The improvement in the intervention group meets the minimal clinically important difference which is also on par with other non-invasive therapies such as repetitive Transcranial Magnetic Stimulation (rTMS). However, the improvement did not differ significantly between the groups. No adverse events were reported in either group.

INTERPRETATION

This Phase I study suggests that NF combined with MOT is safe and improves motor symptoms immediately after treatment, but larger trials are needed to explore its superiority over active control conditions.

Optimization of focality and direction in dense electrode array transcranial direct current stimulation (tDCS)

OBJECTIVE

Transcranial direct current stimulation (tDCS) aims to alter brain function non-invasively via electrodes placed on the scalp. Conventional tDCS uses two relatively large patch electrodes to deliver electrical current to the brain region of interest (ROI). Recent studies have shown that using dense arrays containing up to 512 smaller electrodes may increase the precision of targeting ROIs. However, this creates a need for methods to determine effective and safe stimulus patterns as the number of degrees of freedom is much higher with such arrays. Several approaches to this problem have appeared in the literature. In this paper, we describe a new method for calculating optimal electrode stimulus patterns for targeted and directional modulation in dense array tDCS which differs in some important aspects with methods reported to date.

APPROACH

We optimize stimulus pattern of dense arrays with fixed electrode placement to maximize the current density in a particular direction in the ROI. We impose a flexible set of safety constraints on the current power in the brain, individual electrode currents, and total injected current, to protect subject safety. The proposed optimization problem is convex and thus efficiently solved using existing optimization software to find unique and globally optimal electrode stimulus patterns.

MAIN RESULTS

Solutions for four anatomical ROIs based on a realistic head model are shown as exemplary results. To illustrate the differences between our approach and previously introduced methods, we compare our method with two of the other leading methods in the literature. We also report on extensive simulations that show the effect of the values chosen for each proposed safety constraint bound on the optimized stimulus patterns.

SIGNIFICANCE

The proposed optimization approach employs volume based ROIs, easily adapts to different sets of safety constraints, and takes negligible time to compute. An in-depth comparison study gives insight into the relationship between different objective criteria and optimized stimulus patterns. In addition, the analysis of the interaction between optimized stimulus patterns and safety constraint bounds suggests that more precise current localization in the ROI, with improved safety criterion, may be achieved by careful selection of the constraint bounds.

Electroconvulsive therapy for depression in Parkinson's disease: systematic review of evidence and recommendations

AIM

We performed a systematic review of evidence regarding treatment of depression in Parkinson's disease (PD) utilizing electroconvulsive therapy.

METHODS

The search led to the inclusion of 43 articles, mainly case reports or case series, with the largest number of patients totaling 19.

RESULTS

The analysis included 116 patients with depression and PD; depression improved in 93.1%. Where motor symptoms' severity was reported, 83% of patients improved. Cognition did not worsen in the majority (94%). Many patients experienced delirium or transient confusion, sometimes necessitating discontinuation of electroconvulsive therapy (ECT). Little is known about maintenance ECT in this population.

CONCLUSION

ECT can benefit patients suffering from PD and depression. We recommend an algorithm for treatment of depression in PD, utilizing ECT sooner rather than later.

Regional Interplay for Temporal Processing in Parkinson's Disease: Possibilities and Challenges

Parkinson's disease (PD) is primarily associated with two dominant features: cardinal motor symptoms and the loss of cells in the substantia nigra pars compacta of the basal ganglia. Consequently, these aspects are major foci in PD-related research. However, PD is a neurodegenerative disease, which progressively affects multiple brain regions outside the basal ganglia and leads to symptoms outside the motor domain. Much less is known about the individual contribution of these secondary regions, their interplay and interaction with the basal ganglia, and the respective network dynamics in the overall manifestation of PD. These regions include classical motor structures such as the cerebellum and the supplementary motor area (SMA). However, just as the basal ganglia, these regions display a fine-grained microarchitecture, which supports sensory and sensorimotor functions. One such function is temporal processing, which has been ascribed to a network comprising all of these regions. On the one hand, pathological changes in this temporal processing network may be part and parcel of motor and non-motor symptoms in PD. On the other hand, a better understanding of the role of each network node may offer a novel perspective on compensatory mechanisms, therapeutic interventions, as well as the heterogeneity and individual differences associated with PD. We unfold this perspective by relating the neural foundations and functional implications of temporal processing to pathophysiological and neurofunctional changes characteristic of PD.

Computational Models Describing Possible Mechanisms for Generation of Excessive Beta Oscillations in Parkinson's Disease

In Parkinson's disease, an increase in beta oscillations within the basal ganglia nuclei has been shown to be associated with difficulty in movement initiation. An important role in the generation of these oscillations is thought to be played by the motor cortex and by a network composed of the subthalamic nucleus (STN) and the external segment of globus pallidus (GPe). Several alternative models have been proposed to describe the mechanisms for generation of the Parkinsonian beta oscillations. However, a recent experimental study of Tachibana and colleagues yielded results which are challenging for all published computational models of beta generation. That study investigated how the presence of beta oscillations in a primate model of Parkinson's disease is affected by blocking different connections of the STN-GPe circuit. Due to a large number of experimental conditions, the study provides strong constraints that any mechanistic model of beta generation should satisfy. In this paper we present two models consistent with the data of Tachibana et al. The first model assumes that Parkinsonian beta oscillation are generated in the cortex and the STN-GPe circuits resonates at this frequency. The second model additionally assumes that the feedback from STN-GPe circuit to cortex is important for maintaining the oscillations in the network. Predictions are made about experimental evidence that is required to differentiate between the two models, both of which are able to reproduce firing rates, oscillation frequency and effects of lesions carried out by Tachibana and colleagues. Furthermore, an analysis of the models reveals how the amplitude and frequency of the generated oscillations depend on parameters.

Clinical efficacy of istradefylline versus rTMS on Parkinson's disease in a randomized clinical trial

OBJECTIVE

To compare the efficacy of istradefylline (20 mg/day, 40 mg/day) and repetitive transcranial magnetic stimulation (rTMS) (1 Hz, 10 Hz) as an adjunct therapy to levodopa in the treatment of Parkinson's disease (PD).

METHODS

A total of 132 PD patients from China were randomly assigned to receive 20 mg/day istradefylline plus sham-rTMS (Group I), 40 mg/day istradefylline plus sham-rTMS (Group II), placebo plus 1 Hz rTMS (Group III) and placebo plus 10 Hz rTMS (Group IV) for 12 weeks. Unified Parkinson's Disease Rating Scale (UPDRS) part III score was the primary outcome. Clinical Global Impression-Global Improvement (CGI-I) was the secondary outcome. The change in daily off time in Groups I and II was also recorded.

RESULTS

After 12 weeks of treatment, the changes in UPDRS part III score were -6.05, -6.39, -5.91 and -6.46 for Groups I, II, III and IV, respectively, and the difference was not significant. The difference in CGI-I among the four groups was not significant. The daily off time was reduced by -1.43 hours in Group I and -1.62 hours in Group II. No severe adverse events occurred among the four groups.

CONCLUSION

These results indicate that, as augmentation agents to levodopa in the treatment of PD, istradefylline and rTMS had comparable efficacy and tolerability.

Retrospective Evaluation of Deep Transcranial Magnetic Stimulation as Add-On Treatment for Parkinson's Disease

Objective

To evaluate the safety and assess the different symptom improvements found after a combined low-frequency primary motor cortex and high-frequency prefrontal cortex (PFC) stimulation using the deep TMS (dTMS) H-coil, as an add-on treatment for Parkinson’s disease (PD).

Methods

Forty-five PD patients underwent 14 dTMS sessions; each consisting of 1 Hz stimulation of the primary motor cortex for 15 min, followed by 10 Hz stimulation of the PFC for 15 min. Clinical assessments were performed, BEFORE, at the MIDDLE, and END of therapy as well as at FOLLOW-UP after 30 days, using Movement Disorder Society-Unified Parkinson’s Disease Rating Scale, TINETTI, UP&GO, SCOPA, HDRS₂₁, Beck Depression Inventory, and self-applied daily motor assessment scales.

Results

Treatment was well-tolerated, without serious adverse effects. dTMS-induced significant PD symptom improvements at END and at FOLLOW-UP, in all subscales of the UPDRS, gait speed, depressive symptoms, balance, autonomic symptoms, and a 73% increase in daily ON time.

Conclusion

In the cohort of PD patients treated, dTMS was well-tolerated with only minor adverse effects. The dTMS-induced significant improvements in motor, postural, and motivational symptoms of PD patients and may potentiate concurrent levodopa treatment.

Significance

The present study demonstrates that dTMS may have a much wider spectrum of beneficial effects than previously reported for TMS, including enhancement of levodopa effects, suggesting that future clinical trials with dTMS should include a broader range of symptom measurements.

Alterations in primary motor cortex neurotransmission and gene expression in hemi-parkinsonian rats with drug-induced dyskinesia

Treatment of Parkinson's disease (PD) with dopamine replacement relieves symptoms of poverty of movement, but often causes drug-induced dyskinesias. Accumulating clinical and pre-clinical evidence suggests that the primary motor cortex (M1) is involved in the pathophysiology of PD and that modulating cortical activity may be a therapeutic target in PD and dyskinesia. However, surprisingly little is known about how M1 neurotransmitter tone or gene expression is altered in PD, dyskinesia or associated animal models. The present study utilized the rat unilateral 6-hydroxydopamine (6-OHDA) model of PD/dyskinesia to characterize structural and functional changes taking place in M1 monoamine innervation and gene expression. 6-OHDA caused dopamine pathology in M1, although the lesion was less severe than in the striatum. Rats with 6-OHDA lesions showed a PD motor impairment and developed dyskinesia when given L-DOPA or the D1 receptor agonist, SKF81297. M1 expression of two immediate-early genes (c-Fos and ARC) was strongly enhanced by either L-DOPA or SKF81297. At the same time, expression of genes specifically involved in glutamate and GABA signaling were either modestly affected or unchanged by lesion and/or treatment. We conclude that M1 neurotransmission and signal transduction in the rat 6-OHDA model of PD/dyskinesia mirror features of human PD, supporting the utility of the model to study M1 dysfunction in PD and the elucidation of novel pathophysiological mechanisms and therapeutic targets.

Mechanisms and therapeutic applications of electromagnetic therapy in Parkinson's disease

Electromagnetic therapy is a non-invasive and safe approach for the management of several pathological conditions including neurodegenerative diseases. Parkinson's disease is a neurodegenerative pathology caused by abnormal degeneration of dopaminergic neurons in the ventral tegmental area and substantia nigra pars compacta in the midbrain resulting in damage to the basal ganglia. Electromagnetic therapy has been extensively used in the clinical setting in the form of transcranial magnetic stimulation, repetitive transcranial magnetic stimulation, high-frequency transcranial magnetic stimulation and pulsed electromagnetic field therapy which can also be used in the domestic setting. In this review, we discuss the mechanisms and therapeutic applications of electromagnetic therapy to alleviate motor and non-motor deficits that characterize Parkinson's disease.

Electroconvulsive Therapy Intervention for Parkinson's Disease

BACKGROUND

Electroconvulsive therapy is an established means to improve function in a variety of psychiatric and neurologic conditions, particularly for patients who remain treatment-refractory. Parkinson's disease is a neurodegenerative disorder that sometimes does not respond well to conventional pharmacotherapies. Reports have indicated that electroconvulsive therapy may be an effective and safe treatment for those patients with Parkinson's disease who are not optimally responding to first-line treatments. Despite these reports, however, electroconvulsive therapy is not often used by clinicians in patients with treatment-resistant Parkinson's disease, perhaps due to stigma, lack of knowledge regarding its safety and efficacy, and/or inability to predict the duration of therapeutic benefit.

OBJECTIVE

Our objective was to determine if the available literature on ECT supports it as a safe and effective treatment option in patients with treatment-refractory Parkinson's disease.

CONCLUSION

Motoric improvement induced by electroconvulsive therapy has been documented for decades in persons with Parkinson's disease. Efficacy and safety are reported following electroconvulsive therapy in people with Parkinson's disease who have sub-optimal response to medicines or experience the "on/off" phenomenon to L-dopa. Electroconvulsive therapy is an effective option for acute and maintenance treatment of Parkinson's disease in select patients. Inability to predict how long the beneficial effects of ECT therapy will last in patients with Parkinson's disease may be a reason why this treatment is underutilized by clinicians. More research is warranted to clarify parameters for application and duration of therapeutic benefit in individuals with difficult-to-treat Parkinson's disease.

Repetitive Transcranial Magnetic Stimulation (rTMS) Therapy in Parkinson Disease: A Meta-Analysis

OBJECTIVE

Several studies have reported repetitive transcranial magnetic stimulation (rTMS) therapy as an effective treatment for the control of motor symptoms in Parkinson disease. The objective of the study is to quantify the overall efficacy of this treatment.

TYPES

Systematic review and meta-analysis.

LITERATURE SURVEY

We reviewed the literature on clinical rTMS trials in Parkinson disease since the technique was introduced in 1980. We used the following databases: MEDLINE, Web of Science, Cochrane, and CINAHL.

METHODOLOGY

PATIENTS AND SETTING

Patients with Parkinson disease who were participating in prospective clinical trials that included an active arm and a control arm and change in motor scores on Unified Parkinson's Disease Rating Scale as the primary outcome. We pooled data from 21 studies that met these criteria. We then analyzed separately the effects of low- and high-frequency rTMS on clinical motor improvements.

SYNTHESIS

The overall pooled mean difference between treatment and control groups in the Unified Parkinson's Disease Rating Scale motor score was significant (4.0 points, 95% confidence interval, 1.5, 6.7; P = .005). rTMS therapy was effective when low-frequency stimulation (≤ 1 Hz) was used with a pooled mean difference of 3.3 points (95% confidence interval 1.6, 5.0; P = .005). There was a trend for significance when high-frequency stimulation (≥ 5 Hz) studies were evaluated with a pooled mean difference of 3.9 points (95% confidence interval, -0.7, 8.5; P = .08). rTMS therapy demonstrated benefits at short-term follow-up (immediately after a treatment protocol) with a pooled mean difference of 3.4 points (95% confidence interval, 0.3, 6.6; P = .03) as well as at long-term follow-up (average follow-up 6 weeks) with mean difference of 4.1 points (95% confidence interval, -0.15, 8.4; P = .05). There were insufficient data to statistically analyze the effects of rTMS when we specifically examined bradykinesia, gait, and levodopa-induced dyskinesia using quantitative methods.

CONCLUSION

rTMS therapy in patients with Parkinson disease results in mild-to-moderate motor improvements and has the potential to be used as an adjunct therapy for the treatment of Parkinson disease. Future large, sample studies should be designed to isolate the specific clinical features of Parkinson disease that respond well to rTMS therapy.

The temporary and accumulated effects of transcranial direct current stimulation for the treatment of advanced Parkinson's disease monkeys

Transcranial direct current stimulation (tDCS) is a useful noninvasive technique of cortical brain stimulation for the treatment of neurological disorders. Clinical research has demonstrated tDCS with anodal stimulation of primary motor cortex (M1) in Parkinson’s disease (PD) patients significantly improved their motor function. However, few studies have been focused on the optimization of parameters which contributed significantly to the treatment effects of tDCS and exploration of the underline neuronal mechanisms. Here, we used different stimulation parameters of anodal tDCS on M1 for the treatment of aged advanced PD monkeys induced with 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) administration, and then analyzed the temporary and accumulated effects of tDCS treatment. The results indicated anodal tDCS on M1 very significantly improved motor ability temporarily; importantly, the treatment effects of anodal tDCS on M1 were quantitatively correlated to the accumulated stimulation instead of the stimuli intensity or duration respectively. In addition, c-fos staining showed tDCS treatment effects activated the neurons both in M1 and substantia nigra (SN). Therefore, we propose that long time and continue anodal tDCS on M1 is a better strategy to improve the motor symptoms of PD than individual manipulation of stimuli intensity or duration.

Effects of repetitive transcranial magnetic stimulation on motor symptoms in Parkinson disease: a systematic review and meta-analysis

IMPORTANCE

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive neuromodulation technique that has been closely examined as a possible treatment for Parkinson disease (PD). However, results evaluating the effectiveness of rTMS in PD are mixed, mostly owing to low statistical power or variety in individual rTMS protocols.

OBJECTIVES

To determine the rTMS effects on motor dysfunction in patients with PD and to examine potential factors that modulate the rTMS effects.

DATA SOURCES

Databases searched included PubMed, EMBASE, Web of Knowledge, Scopus, and the Cochrane Library from inception to June 30, 2014.

STUDY SELECTION

Eligible studies included sham-controlled, randomized clinical trials of rTMS intervention for motor dysfunction in patients with PD.

DATA EXTRACTION AND SYNTHESIS

Relevant measures were extracted independently by 2 investigators. Standardized mean differences (SMDs) were calculated with random-effects models.

MAIN OUTCOMES AND MEASURES

Motor examination of the Unified Parkinson's Disease Rating Scale.

RESULTS

Twenty studies with a total of 470 patients were included. Random-effects analysis revealed a pooled SMD of 0.46 (95% CI, 0.29-0.64), indicating an overall medium effect size favoring active rTMS over sham rTMS in the reduction of motor symptoms (P<.001). Subgroup analysis showed that the effect sizes estimated from high-frequency rTMS targeting the primary motor cortex (SMD, 0.77; 95% CI, 0.46-1.08; P<.001) and low-frequency rTMS applied over other frontal regions (SMD, 0.50; 95% CI, 0.13-0.87; P=.008) were significant. The effect sizes obtained from the other 2 combinations of rTMS frequency and rTMS site (ie, high-frequency rTMS at other frontal regions: SMD, 0.23; 95% CI, -0.02 to 0.48, and low primary motor cortex: SMD, 0.28; 95% CI, -0.23 to 0.78) were not significant. Meta-regression revealed that a greater number of pulses per session or across sessions is associated with larger rTMS effects. Using the Grading of Recommendations, Assessment, Development, and Evaluation criteria, we characterized the quality of evidence presented in this meta-analysis as moderate quality.

CONCLUSIONS AND RELEVANCE

The pooled evidence suggests that rTMS improves motor symptoms for patients with PD. Combinations of rTMS site and frequency as well as the number of rTMS pulses are key modulators of rTMS effects. The findings of our meta-analysis may guide treatment decisions and inform future research.

Subject-Specific Multiscale Modeling to Investigate Effects of Transcranial Magnetic Stimulation

OBJECTIVE

Transcranial magnetic stimulation (TMS) is an effective intervention in noninvasive neuromodulation used to treat a number of neurophysiological disorders. Predicting the spatial extent to which neural tissue is affected by TMS remains a challenge. The goal of this study was to develop a computational model to predict specific locations of neural tissue that are activated during TMS. Using this approach, we assessed the effects of changing TMS coil orientation and waveform.

MATERIALS AND METHODS

We integrated novel techniques to develop a subject-specific computational model, which contains three main components: 1) a figure-8 coil (Magstim, Magstim Company Limited, Carmarthenshire, UK); 2) an electromagnetic, time-dependent, nonhomogeneous, finite element model of the whole head; and 3) an adaptation of a previously published pyramidal cell neuron model. We then used our modeling approach to quantify the spatial extent of affected neural tissue for changes in TMS coil rotation and waveform.

RESULTS

We found that our model shows more detailed predictions than previously published models, which underestimate the spatial extent of neural activation. Our results suggest that fortuitous sites of neural activation occur for all tested coil orientations. Additionally, our model predictions show that excitability of individual neural elements changes with a coil rotation of ±15°.

CONCLUSIONS

Our results indicate that the extent of neuromodulation is more widespread than previous published models suggest. Additionally, both specific locations in cortex and the extent of stimulation in cortex depend on coil orientation to within ±15° at a minimum. Lastly, through computational means, we are able to provide insight into the effects of TMS at a cellular level, which is currently unachievable by imaging modalities.

Effective electric fields along realistic DTI-based neural trajectories for modelling the stimulation mechanisms of TMS

In transcranial magnetic stimulation (TMS), an applied alternating magnetic field induces an electric field in the brain that can interact with the neural system. It is generally assumed that this induced electric field is the crucial effect exciting a certain region of the brain. More specifically, it is the component of this field parallel to the neuron's local orientation, the so-called effective electric field, that can initiate neuronal stimulation. Deeper insights on the stimulation mechanisms can be acquired through extensive TMS modelling. Most models study simple representations of neurons with assumed geometries, whereas we embed realistic neural trajectories computed using tractography based on diffusion tensor images. This way of modelling ensures a more accurate spatial distribution of the effective electric field that is in addition patient and case specific. The case study of this paper focuses on the single pulse stimulation of the left primary motor cortex with a standard figure-of-eight coil. Including realistic neural geometry in the model demonstrates the strong and localized variations of the effective electric field between the tracts themselves and along them due to the interplay of factors such as the tract's position and orientation in relation to the TMS coil, the neural trajectory and its course along the white and grey matter interface. Furthermore, the influence of changes in the coil orientation is studied. Investigating the impact of tissue anisotropy confirms that its contribution is not negligible. Moreover, assuming isotropic tissues lead to errors of the same size as rotating or tilting the coil with 10 degrees. In contrast, the model proves to be less sensitive towards the not well-known tissue conductivity values.

Use of cortical stimulation in neuropathic pain, tinnitus, depression, and movement disorders

Medical treatment must strike a balance between benefit and risk. As the field of neuromodulation develops, decreased invasiveness, in combination with maintenance of efficacy, has become a goal. We provide a review of the history of cortical stimulation from its origins to the current state. The first part discusses neuropathic pain and the nonpharmacological treatment options used. The second part covers transitions to tinnitus, believed by many to be another deafferentation disorder, its classification, and treatment. The third part focuses on major depression. The fourth section concludes with the discussion of the use of cortical stimulation in movement disorders. Each part discusses the development of the field, describes the current care protocols, and suggests future avenues for research needed to advance neuromodulation.

Closed-loop brain-machine-body interfaces for noninvasive rehabilitation of movement disorders

Traditional approaches for neurological rehabilitation of patients affected with movement disorders, such as Parkinson's disease (PD), dystonia, and essential tremor (ET) consist mainly of oral medication, physical therapy, and botulinum toxin injections. Recently, the more invasive method of deep brain stimulation (DBS) showed significant improvement of the physical symptoms associated with these disorders. In the past several years, the adoption of feedback control theory helped DBS protocols to take into account the progressive and dynamic nature of these neurological movement disorders that had largely been ignored so far. As a result, a more efficient and effective management of PD cardinal symptoms has emerged. In this paper, we review closed-loop systems for rehabilitation of movement disorders, focusing on PD, for which several invasive and noninvasive methods have been developed during the last decade, reducing the complications and side effects associated with traditional rehabilitation approaches and paving the way for tailored individual therapeutics. We then present a novel, transformative, noninvasive closed-loop framework based on force neurofeedback and discuss several future developments of closed-loop systems that might bring us closer to individualized solutions for neurological rehabilitation of movement disorders.

Quantitative evaluation of electroconvulsive therapy for Parkinson's disease with refractory psychiatric symptoms

Patients with advanced-stage Parkinson's disease (PD) occasionally experience refractory depression or catatonic stupor. Electroconvulsive therapy (ECT) has been reported as a successful procedure for both severe psychosis and motor symptoms in patients with PD. Four patients with PD who were receiving ECT were quantitatively evaluated using the Unified PD Rating scale part III, Hoehn and Yahr scale, Barthel index, Neuropsychiatric Inventory, mini-mental state examination, Revised Hasegawa's Dementia scale, Beck's Depression Inventory, and Hamilton Rating Scale for Depression-17. We adopted the "half-age" method, which is an age-based stimulus-dosing method. The patients showed improvement in symptoms of psychosis and motor symptoms without any adverse effects. The interval of improvement after ECT varied among patients. Of note, a decrease in psychiatric symptoms successfully alleviated the burden of caregivers. ECT may be useful to treat parkinsonism with refractory psychosis, major depression, or catatonic stupor, within the limitations of the patients enrolled.

Are there really "epileptogenic" mechanisms or only corruptions of "normal" plasticity?

Plasticity in the nervous system, whether for establishing connections and networks during development, repairing networks after injury, or modifying connections based on experience, relies primarily on highly coordinated patterns of neural activity. Rhythmic, synchronized bursting of neuronal ensembles is a fundamental component of the activity-dependent plasticity responsible for the wiring and rewiring of neural circuits in the CNS. It is therefore not surprising that the architecture of the CNS supports the generation of highly synchronized bursts of neuronal activity in non-pathological conditions, even though the activity resembles the ictal and interictal events that are the hallmark symptoms of epilepsy. To prevent such natural epileptiform events from becoming pathological, multiple layers of homeostatic control operate on cellular and network levels. Many data on plastic changes that occur in different brain structures during the processes by which the epileptogenic aggregate is constituted have been accumulated but their role in counteracting or promoting such processes is still controversial. In this chapter we will review experimental and clinical evidence on the role of neural plasticity in the development of epilepsy. We will address questions such as: is epilepsy a progressive disorder? What do we know about mechanism(s) accounting for progression? Have we reliable biomarkers of epilepsy-related plastic processes? Do seizure-associated plastic changes protect against injury and aid in recovery? As a necessary premise we will consider the value of seizure-like activity in the context of normal neural development.

The role of electroconvulsive and neuromodulation therapies in the treatment of geriatric depression

Geriatric depression is associated with increased mortality because of suicide and decreases in functional and physical health. Many elders' depression is resistant to psychotherapy and medication and can become chronic. Electroconvulsive therapy (ECT) is increasingly used in the treatment of medication-resistant or life-threatening geriatric depression. Neuromodulation therapies (subconvulsive, focal, or subconvulsive and focal) are alternatives for the management of treatment-resistant depression in the elderly. Therapies that combine both strategies could be safer but may not be as effective as ECT. This review covers the evidence on the safety and efficacy of ECT and the neuromodulation therapies in geriatric depression.