The role of the prefrontal cortex in freezing of gait in Parkinson’s disease: insights from a deep repetitive transcranial magnetic stimulation exploratory study

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.

Direct Current Stimulation of Prefrontal Cortex Is Not Effective in Progressive Supranuclear Palsy: A Randomized Trial

BACKGROUND

Progressive supranuclear palsy (PSP) is a rare 4R-tauopathy. Transcranial direct current stimulation (tDCS) may improve specific symptoms.

OBJECTIVES

This randomized, double-blinded, sham-controlled trial aimed at verifying the short-, mid-, and long-term effect of multiple sessions of anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC) cortex in PSP.

METHODS

Twenty-five patients were randomly assigned to active or sham stimulation (2 mA for 20 minute) for 5 days/week for 2 weeks. Participants underwent assessments at baseline, after the 2-week stimulation protocol, then after 45 days and 3 months from baseline. Primary outcomes were verbal and semantic fluency. The efficacy was verified with analysis of covariance.

RESULTS

We failed to detect a significant effect of active stimulation on primary outcomes. Stimulation was associated to worsening of specific behavioral complaints.

CONCLUSIONS

A 2-week protocol of anodal left DLPFC tDCS is not effective in PSP. Specific challenges in running symptomatic clinical trials with classic design are highlighted. © 2024 International Parkinson and Movement Disorder Society.

The effects of transcranial magnetic stimulation for freezing of gait in Parkinson's disease: a systematic review and meta-analysis of randomized controlled trials

Background

Freezing of gait (FOG) is one of the most disabling gait disturbances in Parkinson's disease (PD), affecting mobility and balance severely, thereby leading to an increased risk of falls.

Objectives

The purpose of this systematic review and meta-analysis was to investigate the effects of transcranial magnetic stimulation on FOG in PD.

Methods

Based on PRISMA guidelines, we searched the databases of MEDLINE (PubMed), Cochrane Library, PEDro, Embase, and Web of Science. Studies of the English language published up to July 2023 were searched. We retrieved for studies of randomized controlled trials (RCTs) of transcranial magnetic stimulation to treat FOG after PD and screened by inclusion and exclusion criteria. Risk of bias was assessed using the Cochrane Collaboration's tool (Revman5.30). Characteristics of RCTs were extracted. The heterogeneity of the trials was measured by I2 statistic. The effect size was expressed by a standardized mean difference (SMD) with a 95% confidence interval (CI).

Results

A total of 488 articles were screened, after screening sixteen RCTs involved in 408 patients were included in the qualitative analysis, and 15 RCTs were included in meta-analysis. The outcome measures included FOG-Q, walking time, TUG, and UPDRS. Six studies used FOG-Q as outcome measure, six studies used walking time, four studies used TUG, and six studies used UPDRS. Compared with placebo treatment, transcranial magnetic stimulation has positive significant effects in improving gait status with increased walking speed (SMD = -0.41, 95% CI = -0.75 to -0.06, I2 = 7% p = 0.02), FOG-Q scores (SMD = -0.55, 95% CI = -0.89 to -0.21, I2 = 29%, p = 0.002), UPDRS scores (SMD = -1.08, 95% CI = -1.39 to -0.78, I2 = 49%, P < 0.001) and the time of TUG (SMD = -0.56, 95% CI = -0.88 to -0.23, I2 = 25%, p = 0.02) decreased.

Conclusion

Transcranial magnetic stimulation could significantly improving gait conditions in PD patients with FOG.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/#recordDetails, CRD42023434286.

Bilateral deep transcranial magnetic stimulation of motor and prefrontal cortices in Parkinson's disease: a comprehensive review

Parkinson's disease (PD) is a prevalent neurodegenerative disorder characterized by both motor and non-motor symptoms, many of which are resistant to currently available treatments. Since the discovery that non-invasive transcranial magnetic stimulation (TMS) can cause dopamine release in PD patients, there has been growing interest in the use of TMS to fill existing gaps in the treatment continuum for PD. This review evaluates the safety and efficacy of a unique multifocal, bilateral Deep TMS protocol, which has been evaluated as a tool to address motor and non-motor symptoms of PD. Six published clinical trials have delivered a two-stage TMS protocol with an H-Coil targeting both the prefrontal cortex (PFC) and motor cortex (M1) bilaterally (220 PD patients in total; 108 from two randomized, sham-controlled studies; 112 from open label or registry studies). In all studies TMS was delivered to M1 bilaterally (Stage 1) and then to the PFC bilaterally (Stage 2) with approximately 900 pulses per stage. For Stage 1 (M1), two studies delivered 10 Hz at 90% motor threshold (MT) while four studies delivered 1 Hz at 110% MT. For Stage 2 (PFC), all studies delivered 10 Hz at 100% MT. The results suggest that this two-stage Deep TMS protocol is a safe, moderately effective treatment for motor symptoms of PD, and that severely impaired patients have the highest benefits. Deep TMS also improves mood symptoms and cognitive function in these patients. Further research is needed to establish optimal dosing and the long-term durability of treatment effects.

Upregulation of the parietal cortex improves freezing of gait in Parkinson's disease

BACKGROUND The posterior parietal cortex (PPC) is a key brain area for visuospatial processing and locomotion. It has been repetitively shown to be involved in the neural correlates of freezing of gait (FOG), a common symptom of Parkinson's disease (PD). However, current neuroimaging modalities do not allow to precisely determine the role of the PPC during real FOG episodes. OBJECTIVES The purpose of this study was to modulate the PPC cortical excitability using repetitive transcranial magnetic stimulation (rTMS) to determine whether the PPC contributes to FOG or compensates for dysfunctional neural networks to reduce FOG. METHODS Fourteen participants with PD who experience freezing took part in a proof of principle study consisting of three experimental sessions targeting the PPC with inhibitory, excitatory, and sham rTMS. Objective FOG outcomes and cortical excitability measurements were acquired before and after each stimulation protocol. RESULTS Increasing PPC excitability resulted in significantly fewer freezing episodes and percent time frozen during a FOG-provoking task. This reduction in FOG most likely emerged from the trend in PPC inhibiting the lower leg motor cortex excitability. CONCLUSION Our results suggest that the recruitment of the PPC is linked to less FOG, providing support for the beneficial role of the PPC upregulation in preventing FOG. This could potentially be linked to a reduction of the cortical input burden on the basal ganglia prior to FOG. Excitatory rTMS interventions targeting the PPC may have the potential to reduce FOG.

Abnormal functional connectivity density involvement in freezing of gait and its application for subtyping Parkinson's disease

The pathophysiological mechanisms at work in Parkinson's disease (PD) patients with freezing of gait (FOG) remain poorly understood. Functional connectivity density (FCD) could provide an unbiased way to analyse connectivity across the brain. In this study, a total of 23 PD patients with FOG (PD FOG + patients), 26 PD patients without FOG (PD FOG- patients), and 22 healthy controls (HCs) were recruited, and their resting-state functional magnetic resonance imaging (rs-fMRI) images were collected. FCD mapping was first performed to identify differences between groups. Pearson correlation analysis was used to explore relationships between FCD values and the severity of FOG. Then, a machine learning model was employed to classify each pair of groups. PD FOG + patients showed significantly increased short-range FCD in the precuneus, cingulate gyrus, and fusiform gyrus and decreased long-range FCD in the frontal gyrus, temporal gyrus, and cingulate gyrus. Short-range FCD values in the middle temporal gyrus and inferior temporal gyrus were positively correlated with FOG questionnaire (FOGQ) scores, and long-range FCD values in the middle frontal gyrus were negatively correlated with FOGQ scores. Using FCD in abnormal regions as input, a support vector machine (SVM) classifier can achieve classification with good performance. The mean accuracy values were 0.895 (PD FOG + vs. HC), 0.966 (PD FOG- vs. HC), and 0.897 (PD FOG + vs. PD FOG-). This study demonstrates that PD FOG + patients showed altered short- and long-range FCD in several brain regions involved in action planning and control, motion processing, emotion, cognition, and object recognition.

Regional homogeneity and functional connectivity of freezing of gait conversion in Parkinson's disease

Background

Freezing of gait (FOG) is common in the late stage of Parkinson's disease (PD), which can lead to disability and impacts the quality of life. Therefore, early recognition is crucial for therapeutic intervention. We aimed to explore the abnormal regional homogeneity (ReHo) and functional connectivity (FC) in FOG converters and evaluate their diagnostic values.

Methods

The data downloaded from the Parkinson's Disease Progression Markers Project (PPMI) cohort was subdivided into PD-FOG converters (n = 16) and non-converters (n = 17) based on whether FOG appeared during the 3-year follow-up; 16 healthy controls were well-matched. ReHo and FC analyses were used to explore the variations in spontaneous activity and interactions between significant regions among three groups of baseline data. Correlations between clinical variables and the altered ReHo values were assessed in FOG converter group. Last, logistic regression and receiver operating characteristic curve (ROC) were used to predict diagnostic value.

Results

Compared with the non-converters, FOG converters had reduced ReHo in the bilateral medial superior frontal gyrus (SFGmed), which was negatively correlated with the postural instability and gait difficulty (PIGD) score. ReHo within left amygdala/olfactory cortex/putamen (AMYG/OLF/PUT) was decreased, which was correlated with anxiety and autonomic dysfunction. Also, increased ReHo in the left supplementary motor area/paracentral lobule was positively correlated with the rapid eye movement sleep behavior disorder screening questionnaire. FOG converters exhibited diminished FC in the basal ganglia, limbic area, and cognitive control cortex, as compared with non-converters. The prediction model combined ReHo of basal ganglia and limbic area, with PIGD score was the best predictor of FOG conversion.

Conclusion

The current results suggested that abnormal ReHo and FC in the basal ganglia, limbic area, and cognitive control cortex may occur in the early stage of FOG. Basal ganglia and limbic area dysfunction combined with higher PIGD score are useful for the early recognition of FOG conversion.

Repetitive transcranial magnetic stimulation enhances the neuronal excitability of mice by regulating dynamic characteristics of Granule cells' Ion channels

This study aims to explore the effects of acute high-frequency repetitive transcranial magnetic stimulation (hf-rTMS) on neuronal excitability of granule cells in the hippocampal dentate gyrus, as well as the underlying intrinsic mediating mechanisms by which rTMS regulates neuronal excitability. First, high-frequency single TMS was used to measure the motor threshold (MT) of mice. Then, rTMS with different intensities of 0 MT (control), 0.8 MT, and 1.2 MT were applied to acute mice brain slices. Next, patch-clamp technique was used to record the resting membrane potential and evoked nerve discharge of granule cells, as well as the voltage-gated sodium current (I Na) of voltage-gated sodium channels (VGSCs), transient outward potassium current (I A) and delayed rectifier potassium current (I K) of voltage-gated potassium channels (Kv). Results showed that acute hf-rTMS in both 0.8 MT and 1.2 MT groups significantly activated I Na and inhibited I A and I K compared with control group, due to the changes of dynamic characteristics of VGSCs and Kv. Acute hf-rTMS in both 0.8 MT and 1.2 MT groups significantly increased membrane potential and nerve discharge frequency. Therefore, changing dynamic characteristics of VGSCs and Kv, activating I Na and inhibiting I A and I K might be one of the intrinsic mediating mechanisms by which rTMS enhanced the neuronal excitability of granular cells, and this regulatory effect increased with the increase of stimulus intensity.

Comparative efficacy of transcranial magnetic stimulation on different targets in Parkinson's disease: A Bayesian network meta-analysis

Background/Objective

The efficacy of transcranial magnetic stimulation (TMS) on Parkinson's disease (PD) varies across the stimulation targets. This study aims to estimate the effect of different TMS targets on motor symptoms in PD.

Methods

A Bayesian hierarchical model was built to assess the effects across different TMS targets, and the rank probabilities and the surface under the cumulative ranking curve (SUCRA) values were calculated to determine the ranks of each target. The primary outcome was the Unified Parkinson's Disease Rating Scale part-III. Inconsistency between direct and indirect comparisons was assessed using the node-splitting method.

Results

Thirty-six trials with 1,122 subjects were included for analysis. The pair-wise meta-analysis results showed that TMS could significantly improve motor symptoms in PD patients. Network meta-analysis results showed that the high-frequency stimulation over bilateral M1, bilateral DLPFC, and M1+DLPFC could significantly reduce the UPDRS-III scores compared with sham conditions. The high-frequency stimulation over both M1 and DLPFC had a more significant effect when compared with other parameters, and ranked first with the highest SCURA value. There was no significant inconsistency between direct and indirect comparisons.

Conclusion

Considering all settings reported in our research, high-frequency stimulation over bilateral M1 or bilateral DLPFC has a moderate beneficial effect on the improvement of motor symptoms in PD (high confidence rating). High-frequency stimulation over M1+DLPFC has a prominent beneficial effect and appears to be the most effective TMS parameter setting for ameliorating motor symptoms of PD patients (high confidence rating).

Gait control by the frontal lobe

The frontal lobe is crucial and contributes to controlling truncal motion, postural responses, and maintaining equilibrium and locomotion. The rich repertoire of frontal gait disorders gives some indication of this complexity. For human walking, it is necessary to simultaneously achieve at least two tasks, such as maintaining a bipedal upright posture and locomotion. Particularly, postural control plays an extremely significant role in enabling the subject to maintain stable gait behaviors to adapt to the environment. To achieve these requirements, the frontal cortex (1) uses cognitive information from the parietal, temporal, and occipital cortices, (2) creates plans and programs of gait behaviors, and (3) acts on the brainstem and spinal cord, where the core posture-gait mechanisms exist. Moreover, the frontal cortex enables one to achieve a variety of gait patterns in response to environmental changes by switching gait patterns from automatic routine to intentionally controlled and learning the new paradigms of gait strategy via networks with the basal ganglia, cerebellum, and limbic structures. This chapter discusses the role of each area of the frontal cortex in behavioral control and attempts to explain how frontal lobe controls walking with special reference to postural control.

Efficacy of repetitive transcranial magnetic stimulation in Parkinson's disease: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive form of brain stimulation that positively regulates the motor and non-motor symptoms of Parkinson's disease (PD). Although, most reviews and meta-analysis have shown that rTMS intervention is effective in treating motor symptoms and depression, very few have used randomised controlled trials (RCTs) to analyse the efficacy of this intervention in PD. We aimed to review RCTs of rTMS in patients with PD to assess the efficacy of rTMS on motor and non-motor function in patients with PD.

METHODS

In this systematic review and meta-analysis, we searched PubMed, MEDLINE and Web of Science databases for RCTs on rTMS in PD published between January 1, 1988 to January 1, 2022. Eligible studies included sham-controlled RCTs that used rTMS stimulation for motor or non-motor symptoms in PD. RCTs not focusing on the efficacy of rTMS in PD were excluded. Summary data were extracting from those RCTs by two investigators independently. We then calculated standardised mean difference with random-effect models. The main outcome included motor and non-motor examination of scales that were used in PD motor or non-motor assessment. This study was registered with PROSPERO, CRD42022329633.

FINDINGS

Fourteen studies with 469 patients met the criteria for our meta-analysis. Twelve eligible studies with 381 patients were pooled to analyse the efficacy of rTMS on motor function improvement. The effect size on motor scale scores was 0.51 (P < 0.0001) and were not distinctly heterogeneous (I² = 29%). Five eligible studies with 202 patients were collected to evaluate antidepressant-like effects. The effect size on depression scale scores was 0.42 (P = 0.004), and were not distinctly heterogeneous (I² = 25%), indicating a significant anti-depressive effect (P = 0.004). The results suggest that high-frequency of rTMS on primary motor cortex (M1) is effective in improving motor symptoms; while the dorsolateral prefrontal cortex (DLPFC) may be a potentially effective area in alleviating depressive symptom.

INTERPRETATION

The findings suggest that rTMS could be used as a possible adjuvant therapy for PD mainly to improve motor symptoms, but could have potential efficacy on depressive symptoms of PD. However, further investigation is needed.

FUNDING

The National Natural Science Foundation of China (NO: 81873777, 82071414), Initiated Foundation of Zhujiang Hospital (NO: 02020318005), Scientific Research Foundation of Guangzhou (NO: 202206010005), and Science and Technology Program of Guangdong of China (NO: 2020A0505100037).

Detection and assessment of Parkinson's disease based on gait analysis: A survey

Neurological disorders represent one of the leading causes of disability and mortality in the world. Parkinson's Disease (PD), for example, affecting millions of people worldwide is often manifested as impaired posture and gait. These impairments have been used as a clinical sign for the early detection of PD, as well as an objective index for pervasive monitoring of the PD patients in daily life. This review presents the evidence that demonstrates the relationship between human gait and PD, and illustrates the role of different gait analysis systems based on vision or wearable sensors. It also provides a comprehensive overview of the available automatic recognition systems for the detection and management of PD. The intervening measures for improving gait performance are summarized, in which the smart devices for gait intervention are emphasized. Finally, this review highlights some of the new opportunities in detecting, monitoring, and treating of PD based on gait, which could facilitate the development of objective gait-based biomarkers for personalized support and treatment of PD.

Differences in neuroanatomy and functional connectivity between motor subtypes of Parkinson’s disease

Background

The “postural instability/gait difficulty” (PIGD) and “tremor-dominant” (TD) motor subtypes of Parkinson’s disease (PD) differ in their clinical manifestations. The neurological basis of these differences is unclear.

Methods

We performed voxel-based morphometric analysis and measured amplitudes of low-frequency fluctuation (ALFF) on 87 PIGD patients and 51 TD patients. We complemented this neuroanatomical comparison with seed-to-voxel analysis to explore differences in functional connectivity.

Results

The PIGD group showed significantly smaller gray matter volume in the medial frontal gyrus (mainly on the right side) than the TD group. Across all patients, gray matter volume in the medial frontal gyrus correlated negatively with severity of PIGD symptoms after controlling for age (r = −0.250, p = 0.003), but this correlation was not observed in separate analyses of only PIGD or TD patients. The PIGD group showed greater functional connectivity of the right superior frontal gyrus with the left lingual gyrus, right lateral occipital cortex, and right lingual gyrus. ALFF did not differ significantly between the two groups.

Conclusion

Postural instability/gait difficulty may be associated with smaller gray matter volume in medial frontal gyrus than TD, as well as with greater functional connectivity between the right superior frontal gyrus and occipital cortex. These results may help explain the clinical differences between the two motor subtypes of PD.

Structural Brain Network Abnormalities in Parkinson’s Disease With Freezing of Gait

Objective

Diffusion tensor imaging (DTI) studies have investigated white matter (WM) integrity abnormalities in Parkinson’s disease (PD). However, little is known about the topological changes in the brain network. This study aims to reveal these changes by comparing PD without freezing of gait (FOG) (PD FOG–), PD with FOG (PD FOG+), and healthy control (HC).

Methods

21 PD FOG+, 34 PD FOG-, and 23 HC were recruited, and DTI images were acquired. The graph theoretical analysis and network-based statistical method were used to calculate the topological parameters and assess connections.

Results

PD FOG+ showed a decreased normalized clustering coefficient, small-worldness, clustering coefficient, and increased local network efficiency compared with HCs. PD FOG+ showed decreased centrality, degree centrality, and nodal efficiency in the striatum, frontal gyrus, and supplementary motor area (SMA). PD FOG+ showed decreased connections in the frontal gyrus, cingulate gyrus, and caudate nucleus (CAU). The between centrality of the left SMA and left CAU was negatively correlated with FOG questionnaire scores.

Conclusion

This study demonstrates that PD FOG+ exhibits disruption of global and local topological organization in structural brain networks, and the disrupted topological organization can be potential biomarkers in PD FOG+. These new findings may provide increasing insight into the pathophysiological mechanism of PD FOG+.

Non-invasive Brain Stimulation for Central Neuropathic Pain

The research and clinical application of the noninvasive brain stimulation (NIBS) technique in the treatment of neuropathic pain (NP) are increasing. In this review article, we outline the effectiveness and limitations of the NIBS approach in treating common central neuropathic pain (CNP). This article summarizes the research progress of NIBS in the treatment of different CNPs and describes the effects and mechanisms of these methods on different CNPs. Repetitive transcranial magnetic stimulation (rTMS) analgesic research has been relatively mature and applied to a variety of CNP treatments. But the optimal stimulation targets, stimulation intensity, and stimulation time of transcranial direct current stimulation (tDCS) for each type of CNP are still difficult to identify. The analgesic mechanism of rTMS is similar to that of tDCS, both of which change cortical excitability and synaptic plasticity, regulate the release of related neurotransmitters and affect the structural and functional connections of brain regions associated with pain processing and regulation. Some deficiencies are found in current NIBS relevant studies, such as small sample size, difficulty to avoid placebo effect, and insufficient research on analgesia mechanism. Future research should gradually carry out large-scale, multicenter studies to test the stability and reliability of the analgesic effects of NIBS.

Parkinson's disease: Alterations of motor plasticity and motor learning

This chapter reviews the alterations in motor learning and motor cortical plasticity in Parkinson's disease (PD), the most common movement disorder. Impairments in motor learning, which is a hallmark of basal ganglia disorders, influence the performance of motor learning-related behavioral tasks and have clinical implications for the management of disturbance in gait and posture, and for rehabilitative management of PD. Although plasticity is classically induced and assessed in sliced preparation in animal models, in this review we have concentrated on the results from non-invasive brain stimulation techniques such as transcranial magnetic stimulation (TMS), transcranial alternating current stimulation (tACS) and transcranial direct current stimulation (tDCS) in patients with PD, in addition to a few animal electrophysiologic studies. The chapter summarizes the results from different cortical and subcortical plasticity investigations. Plasticity induction protocols reveal deficient plasticity in PD and these plasticity measures are modulated by medications and deep brain stimulation. There is considerable variability in these measures that are related to inter-individual variations, different disease characteristics and methodological considerations. Nevertheless, these pathophysiologic studies expand our knowledge of cortical excitability, plasticity and the effects of different treatments in PD. These tools of modulating plasticity and motor learning improve our understanding of PD pathophysiology and help to develop new treatments for this disabling condition.

Motor imagery and gait control in Parkinson's disease: techniques and new perspectives in neurorehabilitation

INTRODUCTION

Motor imagery (MI), defined as the ability to mentally represent an action without actual movement, has been used to improve motor function in athletes and, more recently, in neurological disorders such as Parkinson's disease (PD). Several studies have investigated the neural correlates of motor imagery, which change also depending on the action imagined.

AREAS COVERED

This review focuses on locomotion, which is a crucial activity in everyday life and is often impaired by neurological conditions. After a general discussion on the neural correlates of motor imagery and locomotion, we review the evidence highlighting the abnormalities in gait control and gait imagery in PD patients. Next, new perspectives and techniques for PD patients' rehabilitation are discussed, namely Brain Computer Interfaces (BCIs), neurofeedback, and virtual reality (VR).

EXPERT OPINION

Despite the few studies, the literature review supports the potential beneficial effects of motor imagery interventions in PD focused on locomotion. The development of new technologies could empower the administration of training based on motor imagery locomotor tasks, and their application could lead to new rehabilitation protocols aimed at improving walking ability in patients with PD.

Discussion of Research Priorities for Gait Disorders in Parkinson's Disease

Gait and balance abnormalities develop commonly in Parkinson's disease and are among the motor symptoms most disabling and refractory to dopaminergic or other treatments, including deep brain stimulation. Efforts to develop effective therapies are challenged by limited understanding of these complex disorders. There is a major need for novel and appropriately targeted research to expedite progress in this area. The Scientific Issues Committee of the International Parkinson and Movement Disorder Society has charged a panel of experts in the field to consider the current knowledge gaps and determine the research routes with highest potential to generate groundbreaking data. © 2021 International Parkinson and Movement Disorder Society.

Factors correlated with therapeutic effects of globus pallidus deep brain stimulation on freezing of gait in advanced Parkinson's disease: A pilot study

INTRODUCTION

Deep brain stimulation (DBS) has showed variable therapeutic effect on freezing of gait (FOG) in Parkinson's disease (PD). It is unclear which factors associated with the effect of DBS on FOG in patients with advanced PD. In this study, we investigated the correlation of pre and postoperative factors with the therapeutic effect of globus pallidus interna (GPi) DBS on FOG in PD patients.

METHODS

We retrospectively analyzed PD patients with FOG (N = 20) who underwent GPi DBS surgery. Postoperatively, video-based analysis for FOG severity was performed at the first DBS programming and patients were categorized into two groups according to DBS effect on FOG (11 FOG responders and 9 FOG non-responders) at medication-off state. We analyzed preoperative clinical characteristics, cognitive function, striatal dopamine transporter availability, postoperative DBS programming parameters, lead locations, and volume of tissue activated in functional subregions of GPi. Bootstrap enhanced Elastic-Net logistic regression was used to select pre and postoperative factors associated with the effect of GPi DBS.

RESULTS

Therapeutic effect of GPi DBS on FOG were correlated with the disease duration of PD before DBS surgery, preoperative improvement in FOG severity by levodopa medication, and the distance from active contact of DBS electrode to the prefrontal region of GPi anatomical site.

CONCLUSIONS

Our study results suggest that the effect of GPi DBS on FOG is correlated with disease duration, levodopa responsiveness on FOG before DBS surgery and DBS electrode location, providing useful information to predict FOG outcome after GPi DBS in PD patients.

Future Therapeutic Strategies for Freezing of Gait in Parkinson's Disease

Freezing of gait (FOG) is a common and challenging clinical symptom in Parkinson’s disease. In this review, we summarise the recent insights into freezing of gait and highlight the strategies that should be considered to improve future treatment. There is a need to develop individualised and on-demand therapies, through improved detection and wearable technologies. Whilst there already exist a number of pharmacological (e.g., dopaminergic and beyond dopamine), non-pharmacological (physiotherapy and cueing, cognitive training, and non-invasive brain stimulation) and surgical approaches to freezing (i.e., dual-site deep brain stimulation, closed-loop programming), an integrated collaborative approach to future research in this complex area will be necessary to systematically investigate new therapeutic avenues. A review of the literature suggests standardising how gait freezing is measured, enriching patient cohorts for preventative studies, and harnessing the power of existing data, could help lead to more effective treatments for freezing of gait and offer relief to many patients.

Influence of inter-electrode distance on subthalamic nucleus local field potential recordings in Parkinson's disease

OBJECTIVES

To evaluate spectra and their correlations with clinical symptoms of local field potentials (LFP) acquired from wide- and close-spaced contacts (i.e. between contacts 0-3 or LFP03, and contacts 1-2 or LFP12 respectively) on the same DBS electrode within the subthalamus (STN) in Parkinson's disease (PD), before and after levodopa administration.

METHODS

LFP12 and LFP03 were recorded from 20 PD patients. We evaluated oscillatory power, local and switched phase-amplitude coupling (l- and Sw-PAC) and correlation with motor symptoms (UPDRSIII).

RESULTS

Before levodopa, both LFP03 and LFP12 power in the α band inversely correlated with UPDRSIII. Differences between contacts were found in the low-frequency bands power. After levodopa, differences in UPDRSIII were associated to changes in LFP03 low-β and LFP12 HFO (high frequency oscillations, 250-350 Hz) power, while a modulation of the low-β power and an increased β-LFO (low frequency oscillations, 15-45 Hz) PAC was found only for LFP12.

CONCLUSION

This study reveals differences in spectral pattern between LFP12 and LFP03 before and after levodopa administration, as well as different correlations with PD motor symptoms.

SIGNIFICANCE

Differences between LFP12 and LFP03 may offer an opportunity for optimizing adaptive deep brain stimulation (aDBS) protocols for PD. LFP12 can be used to detect β-HFO coupling and β power (i.e. bradykinesia), while LFP03 are optimal for low frequency oscillations (dyskinesias).

Freezing of Gait in Parkinson's Disease: Invasive and Noninvasive Neuromodulation

INTRODUCTION

Freezing of gait (FoG) is one of the most disabling yet poorly understood symptoms of Parkinson's disease (PD). FoG is an episodic gait pattern characterized by the inability to step that occurs on initiation or turning while walking, particularly with perception of tight surroundings. This phenomenon impairs balance, increases falls, and reduces the quality of life.

MATERIALS AND METHODS

Clinical-anatomical correlations, electrophysiology, and functional imaging have generated several mechanistic hypotheses, ranging from the most distal (abnormal central pattern generators of the spinal cord) to the most proximal (frontal executive dysfunction). Here, we review the neuroanatomy and pathophysiology of gait initiation in the context of FoG, and we discuss targets of central nervous system neuromodulation and their outcomes so far. The PubMed database was searched using these key words: neuromodulation, freezing of gait, Parkinson's disease, and gait disorders.

CONCLUSION

Despite these investigations, the pathogenesis of this process remains poorly understood. The evidence presented in this review suggests FoG to be a heterogenous phenomenon without a single unifying pathologic target. Future studies rigorously assessing targets as well as multimodal approaches will be essential to define the next generation of therapeutic treatments.

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.

The Role of Repetitive Transcranial Magnetic Stimulation for Enhancing the Quality of Life in Parkinson's Disease: A Systematic Review

Background:

Parkinson's disease (PD) is a neurodegenerative disorder which greatly affects patients' quality of life. Despite an exponential increase in PD cases, not much attention has been paid to enhancing their quality of life (QoL). Thus, this systematic review aims to summarize the available literature for the role of repetitive transcranial magnetic stimulation (rTMS) intervention to improve QoL of PD patients.

Methods:

Literature review was carried out using PubMed, Embase, Web of Science and Scopus databases. The key search words were, “rTMS AND Parkinson AND QoL”, “rTMS AND Parkinson AND Quality of Life”. Cochrane Collaboration software Revman 5.3 was used to assess the quality of studies.

Results:

Over 707 studies were identified out of which 5 studies were included which consisted of 160 subjects, 89 male and 71 female, with mean age of 65.04 years. PD type varied from idiopathic PD, rigid, akinetic, tremor dominant to mixed type. The overall risk of bias across the studies was low and unclear with high risk of bias in incomplete outcome data domain in one study.

Conclusions:

The efficacy of rTMS as an adjunct intervention to enhance QoL of PD patients is uncertain due to dire lack of research in this area. The findings of the present review would help researchers conduct a well-defined, randomized, controlled trial by overcoming the present limitations associated with rTMS intervention to improve QoL of PD patients.

Efficacy of non-invasive brain stimulation on cognitive functioning in brain disorders: a meta-analysis

BACKGROUND

Cognition is commonly affected in brain disorders. Non-invasive brain stimulation (NIBS) may have procognitive effects, with high tolerability. This meta-analysis evaluates the efficacy of transcranial magnetic stimulation (TMS) and transcranial Direct Current Stimulation (tDCS) in improving cognition, in schizophrenia, depression, dementia, Parkinson's disease, stroke, traumatic brain injury, and multiple sclerosis.

METHODS

A PRISMA systematic search was conducted for randomized controlled trials. Hedges' g was used to quantify effect sizes (ES) for changes in cognition after TMS/tDCS v. sham. As different cognitive functions may have unequal susceptibility to TMS/tDCS, we separately evaluated the effects on: attention/vigilance, working memory, executive functioning, processing speed, verbal fluency, verbal learning, and social cognition.

RESULTS

We included 82 studies (n = 2784). For working memory, both TMS (ES = 0.17, p = 0.015) and tDCS (ES = 0.17, p = 0.021) showed small but significant effects. Age positively moderated the effect of TMS. TDCS was superior to sham for attention/vigilance (ES = 0.20, p = 0.020). These significant effects did not differ across the type of brain disorder. Results were not significant for the other five cognitive domains.

CONCLUSIONS

Our results revealed that both TMS and tDCS elicit a small trans-diagnostic effect on working memory, tDCS also improved attention/vigilance across diagnoses. Effects on the other domains were not significant. Observed ES were small, yet even slight cognitive improvements may facilitate daily functioning. While NIBS can be a well-tolerated treatment, its effects appear domain specific and should be applied only for realistic indications (i.e. to induce a small improvement in working memory or attention).

Effect of rTMS on Parkinson's cognitive function: a systematic review and meta-analysis

Background

To evaluate the effects and optimal parameters of repetitive transcranial magnetic stimulation (rTMS) on cognition function of patients with Parkinson’s disease (PD) and to estimate which cognitive function may obtain more benefits from rTMS.

Method

The articles dealing with rTMS on cognitive function of PD patients were retrieved from the databases until April 2019. Outcomes of global cognitive function and different cognitive domains were extracted. The standardized mean differences (SMDs) with 95% confidence interval (CI) of cognitive outcome for different parameters, scales, and cognitive functions were estimated.

Results

Fourteen studies involving 173 subjects were included in this meta-analysis. A significant effect size was observed with the mini-mental state examination (MMSE) for the global cognitive outcome based on the evidence of four published articles. Further subtests for different cognitive domains demonstrated prominent effect for the executive function. The significant effect sizes for executive function were found with multiple sessions of high-frequency rTMS over frontal cortex; especially over dorsolateral prefrontal cortex (DLPFC). All of the other cognitive domains, which included memory, attention, and language ability, did not obtain significant effects.

Conclusions

Multiple sessions of high-frequency rTMS over the DLPFC may have positive effect on executive function in PD patients. Further well designed studies with large sample sizes are needed to verify our results and ascertain the long-term effects of rTMS.

Low-Frequency Repetitive Transcranial Magnetic Stimulation over Right Dorsolateral Prefrontal Cortex in Parkinson's Disease

Background

Repetitive transcranial magnetic stimulation (rTMS) is a promising therapeutic tool for Parkinson's disease (PD), and many stimulation targets have been implicated. We aim to explore whether low-frequency rTMS over the right dorsolateral prefrontal cortex (DLPFC) improves motor and nonmotor symptoms of individuals with PD.

Methods

We conducted a randomized, single-blind, sham-controlled parallel trial to compare the effect of 10 consecutive daily sessions of 1 Hz rTMS over right DLPFC on individuals with idiopathic PD between active and sham rTMS group. Primary outcomes were changes in Unified Parkinson's Disease Rating Scale (UPDRS) part III and Nonmotor Symptom Questionnaire (NMSQ). Secondary outcomes were changes in UPDRS total score, Hamilton Rating Scale for Depression (HRSD), Pittsburgh Sleep Quality Index (PSQI), and Montreal Cognitive Assessment (MoCA). Assessments were completed at baseline, after treatment, and at 1 month, 3 months, and 6 months after treatment.

Results

A total of 33 participants with PD were randomized. All participants completed the study and no severe adverse effect was noticed. Compared to baseline, active rTMS showed significant improvements in UPDRS part III and NMSQ at 1 month. Change of scores on UPDRS part III, HRSD, and PSQI persisted for 3 months after rTMS intervention. The beneficial effect on cognitive performance assessed by MoCA was maintained for at least 6 months in the follow-up. No significant changes were observed in the group with sham rTMS.

Conclusions

Low-frequency rTMS of right DLPFC could be a potential selection in managing motor and nonmotor symptoms in PD.

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

Parkinson's disease (PD) is becoming a major public-health issue in an aging population. Available approaches to treat advanced PD still have limitations; new therapies are needed. The non-invasive brain stimulation (NIBS) may offer a complementary approach to treat advanced PD by personalized stimulation. Although NIBS is not as effective as the gold-standard levodopa, recent randomized controlled trials show promising outcomes in the treatment of PD symptoms. Nevertheless, only a few NIBS-stimulation paradigms have shown to improve PD's symptoms. Current clinical recommendations based on the level of evidence are reported in Table 1 through Table 3. Furthermore, novel technological advances hold promise and may soon enable the non-invasive stimulation of deeper brain structures for longer periods.

Freezing of gait: understanding the complexity of an enigmatic phenomenon

Diverse but complementary methodologies are required to uncover the complex determinants and pathophysiology of freezing of gait. To develop future therapeutic avenues, we need a deeper understanding of the disseminated functional-anatomic network and its temporally associated dynamic processes. In this targeted review, we will summarize the latest advances across multiple methodological domains including clinical phenomenology, neurogenetics, multimodal neuroimaging, neurophysiology, and neuromodulation. We found that (i) locomotor network vulnerability is established by structural damage, e.g. from neurodegeneration possibly as result from genetic variability, or to variable degree from brain lesions. This leads to an enhanced network susceptibility, where (ii) modulators can both increase or decrease the threshold to express freezing of gait. Consequent to a threshold decrease, (iii) neuronal integration failure of a multilevel brain network will occur and affect one or numerous nodes and projections of the multilevel network. Finally, (iv) an ultimate pathway might encounter failure of effective motor output and give rise to freezing of gait as clinical endpoint. In conclusion, we derive key questions from this review that challenge this pathophysiological view. We suggest that future research on these questions should lead to improved pathophysiological insight and enhanced therapeutic strategies.

Cortical visuomotor interactions in Freezing of Gait: A TMS approach

OBJECTIVES

Altered cortical visuomotor integration has been involved in the pathophysiology of freezing of gait (FoG) in parkinsonism. The aim of this study was to assess the connections between the primary visual (V1) and motor (M1) areas with a paired-pulse, twin-coil transcranial magnetic stimulation (TMS) technique in patients with FoG.

METHODS

Twelve Parkinson's disease (PD) patients suffering from levodopa-responsive-FoG (off-FoG) were compared with 12 PD patients without FoG and 12 healthy subjects of similar age/sex. In the "off" condition, visuomotor connections (VMCs) were assessed bilaterally. A conditioning stimulus over the V1 phosphene hotspot was followed at interstimulus intervals (ISIs) of 18 and 40ms by a test stimulus over M1, to elicit motor evoked potentials (MEPs) in the contralateral first dorsal interosseous muscle.

RESULTS

Significant (P<0.01), bilateral effects due to VMCs were detected in all three groups, consisting of a MEP suppression at ISI 18 and 40ms. However, in PD patients with FoG, the MEP suppression was significantly (P<0.05) enhanced, both at ISI 18-40ms, in comparison with the other two groups. The phenomenon was limited to the right hemisphere.

CONCLUSIONS

PD patients with FoG showed an excessive inhibitory response of the right M1 to inputs travelling from V1 at given ISIs. Right-sided alterations of the cortical visuomotor integration may contribute to the pathophysiology of FoG.

Synergistic Effects of Mesenchymal Stem Cell Transplantation and Repetitive Transcranial Magnetic Stimulation on Promoting Autophagy and Synaptic Plasticity in Vascular Dementia

Repetitive transcranial magnetic stimulation (rTMS) and mesenchymal stem cells (MSCs) transplantation both showed therapeutic effects on cognition impairment in vascular dementia (VD) model rats. However, whether these two therapies have synergistic effects and the molecular mechanisms remain unclear. In our present study, rats were randomly divided into six groups: control group, sham operation group, VD group, MSC group, rTMS group, and MSC+rTMS group. The VD model rats were prepared using a modified 2VO method. rTMS treatment was implemented at a frequency of 5 Hz, the stimulation intensity for 0.5 Tesla, 20 strings every day with 10 pulses per string and six treatment courses. The results of the Morris water maze test showed that the learning and memory abilities of the MSC group, rTMS group, and MSC+rTMS group were better than that of the VD group, and the MSC+rTMS group showed the most significant effect. The protein expression levels of brain-derived neurotrophic factor, NR1, LC3-II, and Beclin-1 were the highest and p62 protein was the lowest in the MSC+rTMS group. Our findings demonstrated that rTMS could further enhance the effect of MSC transplantation on VD rats and provided an important basis for the combined application of MSC transplantation and rTMS to treat VD or other neurological diseases.

Motor-cognitive approach and aerobic training: a synergism for rehabilitative intervention in Parkinson's disease

Parkinson's disease (PD) results in a complex deterioration of motor behavior. Effective pharmacological or surgical treatments addressing the whole spectrum of both motor and cognitive symptoms are lacking. The cumulative functional impairment may have devastating socio-economic consequences on both patients and caregivers. Comprehensive models of care based on multidisciplinary approaches may succeed in better addressing the overall complexity of PD. Neurorehabilitation is a highly promising non-pharmacological intervention for managing PD. The scientific rationale beyond rehabilitation and its practical applicability remain to be established. In the present perspective, we aim to discuss the current evidence supporting integrated motor-cognitive and aerobic rehabilitation approaches for patients with PD while suggesting a practical framework to optimize this intervention in the next future.

Non-pharmacological management of cognitive impairment in Parkinson's disease

We evaluated the therapeutic effects of non-pharmacological interventions (cognitive training, physical activity, and non-invasive brain stimulation) on cognitive symptoms in Parkinson's disease. A comprehensive literature search for non-pharmacological intervention randomized controlled trials was performed and effect sizes were calculated for each suitable study intervention approach and cognitive domain. Despite the heterogeneity of the study results, we report level B evidence for the probable efficacy of cognitive training in improving or maintaining attention/working memory and memory domains. Level C (possible efficacy) evidence was found for specific physical training types with respect to enhancing executive functions. Non-invasive brain stimulation techniques and combinatorial approaches show preliminary but promising results. Prediction markers evaluating distinct treatment responses should be identified that would help to choose the best candidates for specific treatment strategies and cognitive symptoms. Future directions and recommendations are discussed.

Nonpharmacological, nonsurgical treatments for freezing of gait in Parkinson's disease: A systematic review

Freezing of gait is a disabling phenomenon that appears in a substantial number of Parkinson's disease (PD) patients as the disease evolves. It is considered to be one of the most relevant contributing factors to worsening of quality of life. Current pharmacological or surgical treatment options have limited efficacy. Thus, alternative nonpharmacological/nonsurgical approaches have emerged in recent years in an attempt to improve quality of life in PD. This systematic review summarizes studies of such therapies over the past 5 years. Thirty-five studies were evaluated by use of a qualitative evaluation, while the methodological quality was assessed using validated tools. According to our results, there appear to be two broad categories of nonpharmacological therapies: those that seek a long-lasting benefit and those that aim to achieve a transient effect to overcome the freezing of gait episode. Among the former, it is possible to differentiate between "passive" therapies, which include transcranial magnetic stimulation or transcranial direct current stimulation, and "active" therapies, which are based on different cognitive or physical training programs. Finally, "transient effect" therapies use different types of cues, such as visual, auditory, or proprioceptive stimuli, to attempt to shift the patient's habitual motor control to a goal-directed one. In conclusion, a broad spectrum of nonpharmacological/nonsurgical approaches for freezing of gait has emerged in recent years with promising results. © 2019 International Parkinson and Movement Disorder Society.

Falls in Synucleinopathies

Parkinson's disease (PD) and other synucleinopathies, namely dementia with Lewy bodies (DLB) and multiple system atrophy (MSA), are common degenerative neurological disorders that share synuclein pathology. Although certain cardinal features of parkinsonism, including bradykinesia and rigidity, respond well to levodopa, axial features, such as gait and balance impairment, are less reliably responsive to dopaminergic therapy and surgical interventions. Consequently, falls are common in PD and other synucleinopathies and are a major contributor toward injury and loss of independence. This underscores the need for appropriate fall risk assessment and implementation of preventative measures in all patients with parkinsonism. The aim of this review is therefore to explore modifiable and non-modifiable risk factors for falls in synucleinopathies. We next review and evaluate the evidence for pharmacological, nonpharmacological, and surgical approaches for fall prevention, and emphasize individualized and multifaceted approaches.

High-frequency rTMS over the supplementary motor area improves freezing of gait in Parkinson's disease: a randomized controlled trial

INTRODUCTION

Freezing of gait (FOG) contributes to falls in Parkinson's disease (PD), but robust, effective treatments remain elusive. There is evidence indicating that the supplementary motor area (SMA) plays an important role in the pathogenesis of FOG and may therefore be a potential neuromodulation target. The present study explored the clinical efficacy of high-frequency repetitive transcranial magnetic stimulation (rTMS) over the SMA on FOG in PD patients.

METHODS

A group of 30 PD patients with FOG were enrolled in a randomized, double-blind, sham-controlled trial. Patients were randomly allocated 2:1 to receive ten sessions of either real (N = 20) or sham (N = 10) 10 Hz rTMS over SMA. The patients were assessed at baseline (T₀), after the 5th (T₁) and 10th (T₂) sessions, and then 2 weeks (T₃) and 4 weeks (T₄) after the last session. The primary clinical outcome was the Freezing of Gait Questionnaire score (FOGQ), with the Movement Disorder Society-Unified Parkinson's Disease Rating Scale motor scores (MDS-UPDRS III) and Timed Up and Go test as secondary clinical outcomes. All the assessments were carried out at the "ON" state.

RESULTS

With a four week's follow-up, there were significant interaction effects in the FOGQ (effect of group*time, p = 0.04), MDS-UPDRS III (p = 0.02) and several gait variables (total duration, p < 0.01; cadence, p = 0.04; turn duration, p = 0.01; and turn to sit duration, p = 0.02). Post-hoc analyses revealed a significantly decreased FOGQ score at T₂ and T₄, and significant improvements of MDS-UPDRS III and gait variables at T₁, T₂, T₃ and T₄ in the rTMS group. No significant improvements were found in the sham group.

CONCLUSION

High-frequency rTMS over SMA may ultimately serve as an add-on therapy for alleviating FOG in PD patients.

Is the dopaminergic loss associated with gait and postural impairments in subjects with Parkinson's disease at different motor stages?

Gait and postural control deficiencies in Parkinson's disease (PD) involve several specific motor aspects. The aim of this study was to identify and compare the main changes in gait kinematics and postural control with dopaminergic loss in the striatum region. This is a cross-sectional study that included 42 individuals with PD at different motor stages, according to the Hoehn & Yahr scale (H&Y). Motor subsection of the Movement Disorder Society-Unified Parkinson Disease Rating Scale-part III (MDS-UPDRS III) was used to evaluate general motor aspects. Gait kinematics was assessed using a three-dimensional motion capture system. Postural control was assessed by stabilometry using force platforms. Dopamine depletion was verified through 99mTc-TRODAT-1 (SPECT-CT) examination. We included 12, 15 and 15 individuals classified as H&Y I, II and III, respectively. We identified worse values of dopamine transporter uptake, MDS-UPDRS III, gait parameters (velocity, step length and stride length) and center of pressure displacement as the disease progressed. Our results indicate that higher dopaminergic loss and gait and postural control deficits occur between the H&Y levels II and III.

Treatment of patients with geriatric depression with repetitive transcranial magnetic stimulation

Repetitive transcranial magnetic stimulation (rTMS) has become a useful tool to treat different neuropsychiatric conditions such as depression, dementia and extrapyramidal syndromes insufficiently responding to conventional treatment. In this SHAM-controlled exploratory study safety, symptom improvement as well as changes in inflammation markers and neurotransmitter precursor amino acids availability were studied after a prefrontal cortex (PFC) stimulation using rTMS as add-on treatment in 29 patients with geriatric depression. Out of these, ten patients received SHAM treatment. Treatment was well tolerated, no serious adverse effects were observed. A clear improvement in symptoms of depression with a significant decrease in the HAMD-7 (U = 3.306, p = 0.001) was found by rTMS treatment. In parallel, serum phenylalanine dropped significantly (U = 2.340, p < 0.02), and there was a decline of tryptophan and of Phe/Tyr concentrations, both the effects, however, failed to reach the levels of statistical significance. In the patients who underwent SHAM treatment, no significant changes of HAMD-7 or the concentrations of any biomarker in the study could be found. In addition to the significant effect of rTMS on depression scores, these results point to a possible influence of rTMS on the enzyme phenylalanine hydroxylase (PAH), which plays a crucial role in the biosynthesis of neurotransmitter precursors related to geriatric depression.

Land Plus Aquatic Therapy Versus Land-Based Rehabilitation Alone for the Treatment of Freezing of Gait in Parkinson Disease: A Randomized Controlled Trial

BACKGROUND

Freezing of gait (FOG) is one of the most disabling symptoms of Parkinson disease (PD). Different land-based rehabilitation approaches based on motor and cognitive strategies can be effective in treating FOG. Although there are data about the efficacy of aquatic therapy in ameliorating this phenomenon, no study has explored the combined effect of land-based therapies plus aquatic therapy in patients with PD who have FOG.

OBJECTIVE

The objective was to investigate the effectiveness of a multidisciplinary, intensive, motor-cognitive rehabilitation treatment (MIRT) in improving FOG and whether implementation with aquatic therapy (MIRT-AT) adds further benefits.

DESIGN

The design consisted of a single-blind, parallel-group, 1:1 allocation ratio, randomized trial.

SETTING

The Department of Parkinson Disease, Movement Disorders and Brain Injury Rehabilitation at "Moriggia-Pelascini" Hospital (Gravedona ed Uniti, Como, Italy) was used as the setting.

PARTICIPANTS

Sixty hospitalized patients with PD who had FOG in Hoehn and Yahr stage 2 or 5-3 were included.

INTERVENTION

Sixty patients with PD + FOG were randomly assigned to 2 groups: 30 underwent a 4-week MIRT and 30 underwent a 4-week MIRT-AT.

MEASUREMENTS

The primary outcome measure was the Freezing of Gait Questionnaire; secondary outcome measures were total Unified Parkinson Disease Rating Scale (UPDRS), UPDRS II, UPDRS III, Berg Balance Scale, Timed Up and Go Test, and 6-Minute Walk Test. These measures were assessed both at admission and discharge.

RESULTS

Participants in the 2 groups had similar age, sex distribution, Hoehn and Yahr stage, and most-affected side. At baseline, no difference in outcome measures was observed between the 2 groups. After treatment, a significant time effect was observed for all variables in both groups. No significant time × group interaction was observed. A between-group analysis showed nonsignificant differences between values at T1 and values at T0 for all variables.

LIMITATIONS

The limitations were the lack of a control group and follow-up.

CONCLUSIONS

We showed that a multidisciplinary, intensive, and goal-based rehabilitation treatment, such as MIRT, improves FOG in patients with PD. Although aquatic therapy could be considered a useful approach for treating FOG, it does not add further benefits to this kind of motor-cognitive rehabilitation.

Effects of non-invasive brain stimulation on freezing of gait in parkinsonism: A systematic review with meta-analysis

INTRODUCTION

To investigate the effect of non-invasive brain stimulation (NIBS), including repetitive transcranial magnetic stimulation and transcranial direct current stimulation, on freezing of gait (FOG) in parkinsonism.

METHODS

The PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and Physiotherapy Evidence Database (PEDro) databases were searched up to October 2018 for articles published in English or Korean. Quality assessment was performed using the PEDro scale. Studies with random allocation and pre-intervention and post-intervention assessments for FOG were included, and the standardized mean differences for each outcome were calculated.

RESULTS

Seven studies including 102 participants were included in the final analysis. The meta-analysis showed a significant improvement in freezing of gait questionnaire (FOG-Q) scores (SMD = 0.28; 95% CI, 0.01 to 0.55) and turning time (SMD = 0.30; 95% CI, 0.02 to 0.58). When analyzing only participants with Parkinson's disease, the effect size according to the FOG-Q score was greater (SMD = 0.57; 95% CI, 0.15 to 0.98) and the United Parkinson's disease rating scale-III score was significantly improved after NIBS (SMD = 0.43; 95% CI, 0.01 to 0.86). Both motor and frontal cortex stimulation didn't reveal significant improvement for FOG, but, the effect size of motor cortex stimulation (SMD = 0.35; 95% CI, -0.06 to 0.76) was almost double compared with that of frontal cortex stimulation (SMD = 0.19; 95% CI, -0.26 to 0.63).

CONCLUSION

NIBS showed a beneficial effect on FOG in parkinsonism, and the effects were more prominent in Parkinson's disease. Further studies are needed to determine the optimal protocol and elucidate effects according to the intervention and disease type.

Brain imaging of locomotion in neurological conditions

Impaired locomotion is a frequent and major source of disability in patients with neurological conditions. Different neuroimaging methods have been used to understand the brain substrates of locomotion in various neurological diseases (mainly in Parkinson's disease) during actual walking, and while resting (using mental imagery of gait, or brain-behavior correlation analyses). These studies, using structural (i.e., MRI) or functional (i.e., functional MRI or functional near infra-red spectroscopy) brain imaging, electrophysiology (i.e., EEG), non-invasive brain stimulation (i.e., transcranial magnetic stimulation, or transcranial direct current stimulation) or molecular imaging methods (i.e., PET, or SPECT) reveal extended brain networks involving both grey and white matters in key cortical (i.e., prefrontal cortex) and subcortical (basal ganglia and cerebellum) regions associated with locomotion. However, the specific roles of the various pathophysiological mechanisms encountered in each neurological condition on the phenotype of gait disorders still remains unclear. After reviewing the results of individual brain imaging techniques across the common neurological conditions, such as Parkinson's disease, dementia, stroke, or multiple sclerosis, we will discuss how the development of new imaging techniques and computational analyses that integrate multivariate correlations in "large enough datasets" might help to understand how individual pathophysiological mechanisms express clinically as an abnormal gait. Finally, we will explore how these new analytic methods could drive our rehabilitative strategies.

Repetitive transcranial magnetic stimulation in patients with late life depression influences phenylalanine metabolism

Repetitive transcranial magnetic stimulation (rTMS) is used to treat different neuropsychiatric conditions like Parkinson’s disease, essential tremor, stroke, cognitive decline, dementia and depression. rTMS may exert its therapeutic effects by influencing the biochemistry of neurotransmitters. In this exploratory study, safety symptom improvement and changes in the availability of neurotransmitter precursor amino acids were studied following prefrontal cortex (PFC) stimulation using repetitive transcranial stimulation with TheraCell apparatus R (Guth Meditec, Salach, Germany) as an additional treatment in ten patients with late life depression. Treatment was well tolerated with no serious adverse effects being observed. rTMS induced a significant improvement in the symptoms of depression and a significant decrease in the HAMD-7 (p <0.03). At the same time, the serum phenylalanine to tyrosine ratio declined significantly (p <0.04). No significant influence of rTMS on tryptophan breakdown and serum neopterin concentrations was observed. These preliminary findings indicate that rTMS may influence the activity of the enzyme phenylalanine hydroxylase (PAH) which plays a key role in the biosynthesis of neurotransmitter precursors related to neuropsychiatric symptoms in late life depression. However, results were obtained from only 10 patients. Larger studies are therefore required to support these conclusions

Freezing of gait: Promising avenues for future treatment

Freezing of gait is a devastating symptom of Parkinson's disease and other forms of parkinsonism. It poses a major burden on both patients and their families, as freezing often leads to falls, fall-related injuries and a loss of independence. Treating freezing of gait is difficult for a variety of reasons: it has a paroxysmal and unpredictable nature; a multifaceted pathophysiology, with an interplay between motor elements (disturbed stepping mechanisms) and non-motor elements (cognitive decline, anxiety); and a complex (and likely heterogeneous) underlying neural substrate, involving multiple failing neural networks. In recent years, advances in translational neuroscience have offered new insights into the pathophysiology underlying freezing. Furthermore, the mechanisms behind the effectiveness of available treatments (or lack thereof) are better understood. Driven by these concepts, researchers and clinicians have begun to improve currently available treatment options, and develop new and better treatment methods. Here, we evaluate the range of pharmacological (i.e. closed-looped approaches), surgical (i.e. multi-target and adaptive deep brain and spinal cord stimulation) and behavioural (i.e. biofeedback and cueing on demand) treatment options that are under development, and propose novel avenues that are likely to play a crucial role in the clinical management of freezing of gait in the near future. The outcomes of this review suggest that the successful future management of freezing of gait will require individualized treatments that can be implemented in an on-demand manner in response to imminent freezing. With this review we hope to guide much-needed advances in treating this devastating symptom of Parkinson's disease.

Multitarget transcranial direct current stimulation for freezing of gait in Parkinson's disease

BACKGROUND

Recent findings suggest that transcranial direct current stimulation of the primary motor cortex may ameliorate freezing of gait. However, the effects of multitarget simultaneous stimulation of motor and cognitive networks are mostly unknown. The objective of this study was to evaluate the effects of multitarget transcranial direct current stimulation of the primary motor cortex and left dorsolateral prefrontal cortex on freezing of gait and related outcomes.

METHODS

Twenty patients with Parkinson's disease and freezing of gait received 20 minutes of transcranial direct current stimulation on 3 separate visits. Transcranial direct current stimulation targeted the primary motor cortex and left dorsolateral prefrontal cortex simultaneously, primary motor cortex only, or sham stimulation (order randomized and double-blinded assessments). Participants completed a freezing of gait-provoking test, the Timed Up and Go, and the Stroop test before and after each transcranial direct current stimulation session.

RESULTS

Performance on the freezing of gait-provoking test (P = 0.010), Timed Up and Go (P = 0.006), and the Stroop test (P = 0.016) improved after simultaneous stimulation of the primary motor cortex and left dorsolateral prefrontal cortex, but not after primary motor cortex only or sham stimulation.

CONCLUSIONS

Transcranial direct current stimulation designed to simultaneously target motor and cognitive regions apparently induces immediate aftereffects in the brain that translate into reduced freezing of gait and improvements in executive function and mobility. © 2018 International Parkinson and Movement Disorder Society.

Subthalamic neural entropy is a feature of freezing of gait in freely moving people with Parkinson's disease

The goal of this study was to investigate subthalamic (STN) neural features of Freezers and Non-Freezers with Parkinson's disease (PD), while freely walking without freezing of gait (FOG) and during periods of FOG, which were better elicited during a novel turning and barrier gait task than during forward walking.

METHODS

Synchronous STN local field potentials (LFPs), shank angular velocities, and ground reaction forces were measured in fourteen PD subjects (eight Freezers) off medication, OFF deep brain stimulation (DBS), using an investigative, implanted, sensing neurostimulator (Activa® PC+S, Medtronic, Inc.). Tasks included standing still, instrumented forward walking, stepping in place on dual forceplates, and instrumented walking through a turning and barrier course.

RESULTS

During locomotion without FOG, Freezers showed lower beta (13-30Hz) power (P=0.036) and greater beta Sample Entropy (P=0.032), than Non-Freezers, as well as greater gait asymmetry and arrhythmicity (P<0.05 for both). No differences in alpha/beta power and/or entropy were evident at rest. During periods of FOG, Freezers showed greater alpha (8-12Hz) Sample Entropy (P<0.001) than during walking without FOG.

CONCLUSIONS

A novel turning and barrier course was superior to FW in eliciting FOG. Greater unpredictability in subthalamic beta rhythms was evident during stepping without freezing episodes in Freezers compared to Non-Freezers, whereas greater unpredictability in alpha rhythms was evident in Freezers during FOG. Non-linear analysis of dynamic neural signals during gait in freely moving people with PD may yield greater insight into the pathophysiology of FOG; whether the increases in STN entropy are causative or compensatory remains to be determined. Some beta LFP power may be useful for rhythmic, symmetric gait and DBS parameters, which completely attenuate STN beta power may worsen rather than improve FOG.