Progression of postural control and gait deficits in Parkinson's disease and freezing of gait: A longitudinal study

Dynamic balance and gait impairments in Parkinson's disease: novel cholinergic patterns

The cholinergic system has been implicated in postural deficits, in particular falls, in Parkinson's disease (PD). Falls and freezing of gait typically occur during dynamic and challenging balance and gait conditions, such as when initiating gait, experiencing postural perturbations, or making turns. However, the precise cholinergic neural substrate underlying dynamic postural and gait changes remains poorly understood. The aim of this study was to investigate whether brain vesicular acetylcholine transporter binding, as measured with [18F]-fluoroethoxybenzovesamicol binding PET, correlates with dynamic gait and balance impairments in 125 patients with PD (mean age 66.89 ± 7.71 years) using the abbreviated balance evaluation systems test total and its four functional domain sub-scores (anticipatory postural control, reactive postural control, dynamic gait, and sensory integration). Whole brain false discovery-corrected (P < 0.05) correlations for total abbreviated balance evaluation systems test scores included the following bilateral or asymmetric hemispheric regions: gyrus rectus, orbitofrontal cortex, anterior part of the dorsomedial prefrontal cortex, dorsolateral prefrontal cortex, cingulum, frontotemporal opercula, insula, fimbria, right temporal pole, mesiotemporal, parietal and visual cortices, caudate nucleus, lateral and medial geniculate bodies, thalamus, lingual gyrus, cerebellar hemisphere lobule VI, left cerebellar crus I, superior cerebellar peduncles, flocculus, and nodulus. No significant correlations were found for the putamen or anteroventral putamen. The four domain-specific sub-scores demonstrated overlapping cholinergic topography in the metathalamus, fimbria, thalamus proper, and prefrontal cortices but also showed distinct topographic variations. For example, reactive postural control functions involved the right flocculus but not the upper brainstem regions. The anterior cingulum associated with reactive postural control whereas the posterior cingulum correlated with anticipatory control. The spatial extent of associated cholinergic system changes were least for dynamic gait and sensory orientation functional domains compared to the anticipatory and reactive postural control functions. We conclude that specific aspects of dynamic balance and gait deficits in PD associate with overlapping but also distinct patterns of cerebral cholinergic system changes in numerous brain regions. Our study also presents novel evidence of cholinergic topography involved in dynamic balance and gait in PD that have not been typically associated with mobility disturbances, such as the right anterior temporal pole, right anterior part of the dorsomedial prefrontal cortex, gyrus rectus, fimbria, lingual gyrus, flocculus, nodulus, and right cerebellar hemisphere lobules VI and left crus I.

Trans-Spinal Theta Burst Magnetic Stimulation in Parkinson's Disease and Gait Disorders

BACKGROUND

Gait disorders in patients with Parkinson's disease (PD) can become disabling with disease progression without effective treatment.

OBJECTIVES

To investigate the efficacy of intermittent θ burst trans-spinal magnetic stimulation (TsMS) in PD patients with gait and balance disorders.

METHODS

This was a randomized, parallel, double-blind, controlled trial. Active or sham TsMS was applied at third thoracic vertebra with 100% of the trans-spinal motor threshold, during 5 consecutive days. Participants were evaluated at baseline, immediately after last session, 1 and 4 weeks after last session. Primary outcome was Total Timed Up and Go (TUG) values comparing active versus sham phases 1 week after intervention. The secondary outcome measurements consisted of motor, gait and balance scales, and questionnaires for quality of life and cognition.

RESULTS

Thirty-three patients were included, average age 68.5 (6.4) years in active group and 70.3 (6.3) years in sham group. In active group, Total TUG mean baseline was 107.18 (95% CI, 52.1-116.1), and 1 week after stimulation was 93.0 (95% CI, 50.7-135.3); sham group, Total TUG mean baseline was 101.2 (95% CI, 47.1-155.3) and 1 week after stimulation 75.2 (95% CI 34.0-116.4), P = 0.54. Similarly, intervention had no significant effects on secondary outcome measurements. During stimulation period, five patients presented with mild side effects (three in active group and two in sham group).

DISCUSSION

TsMS did not significantly improve gait or balance analysis in patients with PD and gait disorders. The protocol was safe and well tolerated. © 2024 International Parkinson and Movement Disorder Society.

Distinguishing features of Parkinson's disease fallers based on wireless insole plantar pressure monitoring

Postural instability is one of the most disabling motor signs of Parkinson's disease (PD) and often underlies an increased likelihood of falling and loss of independence. Current clinical assessments of PD-related postural instability are based on a retropulsion test, which introduces human error and only evaluates reactive balance. There is an unmet need for objective, multi-dimensional assessments of postural instability that directly reflect activities of daily living in which individuals may experience postural instability. In this study, we trained machine-learning models on insole plantar pressure data from 111 participants (44 with PD and 67 controls) as they performed simulated static and active postural tasks of activities that often occur during daily living. Models accurately classified PD from young controls (area under the curve (AUC) 0.99+/- 0.00), PD from age-matched controls (AUC 0.99+/- 0.01), and PD fallers from PD non-fallers (AUC 0.91+/- 0.08). Utilizing features from both static and active postural tasks significantly improved classification performances, and all tasks were useful for separating PD from controls; however, tasks with higher postural threats were preferred for separating PD fallers from PD non-fallers.

Freezing of Gait Is Associated with Daily Activity Limitations among Individuals with Parkinson's Disease and Mild Cognitive Impairment

This study investigated the relationship between freezing of gait and daily activities among individuals with mild cognitive impairment due to Parkinson's disease by determining differences in caregiver-reported daily activity performance between individuals with and without freezing of gait. Cross-sectional baseline data from a longitudinal cohort study were used with 24 participants. Caregivers completed the Activities of Daily Living Questionnaire (ADLQ). Using a Mann-Whitney U test, findings indicated that participants with freezing of gait reported overall higher functional impairment levels on the ADLQ (p=.001), including the household, travel, self-care, employment and recreation, and communication subscores, indicating more perceived impairment. Findings show freezing of gait is associated with daily activity limitations in the home and the community among individuals with mild cognitive impairment due to Parkinson's disease. Clinicians should consider assessing freezing of gait, as early detection can inform the selection of interventions and strategies to minimize its impact on the performance of daily activities.

Use of a Home-Based, Commercial Exercise Platform to Remotely Monitor Aerobic Exercise Adherence and Intensity in People With Parkinson Disease

OBJECTIVE

Physical therapists are well-positioned to prescribe exercise outside of a clinical setting to promote positive health behaviors in people with Parkinson disease (PD). Traditionally, a barrier to precise exercise prescription has been reliance on participant self-reported exercise adherence and intensity. Home-based, commercially available exercise platforms offer an opportunity to remotely monitor exercise behavior and facilitate adherence based on objective performance metrics. The primary aim of this project was to characterize the feasibility and processes of remote aerobic exercise data monitoring from a home-based, commercially available platform in individuals participating in the 12-month Cyclical Lower Extremity Exercise for PD II (CYCLE-II) randomized clinical trial. Secondary aims focused on using exercise behavior to classify the cohort into exercise archetypes and describing a shared decision-making process to facilitate exercise adherence.

METHODS

Data from each exercise session were extracted, visualized, and filtered to ensure ride integrity. Weekly exercise frequency was used to determine exercise archetypes: Adherent (2-4 exercise sessions per week), Over-adherent (>4 exercise sessions per week), and Under-adherent (<2 exercise sessions per week).

RESULTS

A total of 123 people with PD completed 22,000+ exercise sessions. Analysis of exercise frequency indicated that 79% of participants were adherent; 8% were over-adherent; and 13% were under-adherent. Three case reports illustrate how shared decision-making with the use of exercise performance data points guided exercise prescription.

CONCLUSIONS

The number of exercise sessions and completeness of the data indicate that people with PD were able to utilize a commercial, home-based exercise platform to successfully engage in long-term aerobic exercise. Physical therapists can use objective data as a part of a shared decision-making process to facilitate exercise adherence.

IMPACT

Commercially available exercise platforms offer a unique approach for physical therapists to monitor exercise behavior outside of a clinical setting. The methods used in this project can serve as a roadmap to utilizing data from consumer-based platforms.

Assessing balance in people with bilateral vestibulopathy using the Mini-Balance Evaluation Systems Test (Mini-BESTest): feasibility and comparison with healthy control data

OBJECTIVES

Bilateral vestibulopathy (BVP) leads to unsteadiness when walking, which worsens in darkness or on uneven ground, as well as falls. Since simple balance tests struggle to distinguish between BVP and healthy participants, we aimed (1) to test if the Mini-BESTest is feasible in BVP, (2) how people with BVP perform on the Mini-BESTest and (3) to compare these scores with healthy reference data.

METHODS

Fifty participants with BVP completed the Mini-BESTest. 12-month falls incidence was obtained by questionnaire. To compare the overall and sub-scores between our participants with BVP and those of healthy participants from the literature (n = 327; obtained via PubMed searches), Mann-Whitney U tests were used. Sub scores within the BVP group were also compared. Spearman correlations were used to investigate the relationships between Mini-BESTest score and age.

RESULTS

No floor or ceiling effects were observed. Participants with BVP had significantly lower Mini-BESTest total scores than the healthy group. Anticipatory, reactive postural control and sensory orientation sub scores of the Mini-BESTest were significantly lower in BVP, while dynamic gait sub scores were not significantly different. A stronger negative correlation between age and Mini-BESTest total score was found in BVP than in the healthy group. Scores did not differ between patients with different falls history.

CONCLUSION

The Mini-BESTest is feasible in BVP. Our results confirm the commonly reported balance deficits in BVP. The stronger negative association between age and balance in BVP might reflect the age-related decline in the remaining sensory systems with which people with BVP compensate.

Validation of a Parkinson's disease questionnaire-39-based functional mobility composite score (FMCS) in people with Parkinson's disease

INTRODUCTION

Functional mobility is an important outcome for people with Parkinson's disease (PwP). Despite this, there is no established patient-reported outcome measure that serves as a gold standard for assessing patient-reported functional mobility in PwP. We aimed to validate the algorithm calculating the Parkinson's Disease Questionnaire-39 (PDQ-39) based Functional Mobility Composite Score (FMCS).

METHODS

We designed a count-based algorithm to measure patient-reported functional mobility in PwP from items of the PDQ-39 subscales mobility and activities of daily living. Convergent validity of the algorithm calculating the PDQ-39-based FMCS was assessed using the objective Timed Up and Go (n = 253) and discriminative validity was assessed by comparing the FMCS with patient-reported (MDS-UPDRS II) and clinician-assessed (MDS-UPDRS III) motor symptoms as well as between disease stages (H&Y) and PIGD phenotypes (n = 736). Participants were between 22 and 92 years old, with a disease duration from 0 to 32 years and 64.9% in a H&Y 1-2 ranging from 1 to 5.

RESULTS

Spearman correlation coefficients (r_s) ranging from -0.45 to -0.77 (p < 0.001) indicated convergent validity. Hence, a t-test suggested sufficient ability of the FMCS to discriminate (p < 0.001) between patient-reported and clinician-assessed motor symptoms. More specifically, FMCS was more strongly associated with patient-reported MDS-UPDRS II (r_s = -0.77) than clinician-reported MDS-UPDRS III (r_s = -0.45) and can discriminate between disease stages as between PIGD phenotypes (p < 0.001).

CONCLUSION

The FMCS is a valid composite score to assess functional mobility through patient reports in PwP for studying functional mobility in studies using the PDQ-39.

Gait Declines Differentially in, and Improves Prediction of, People with Parkinson's Disease Converting to a Freezing of Gait Phenotype

BACKGROUND

Freezing of gait (FOG) is a debilitating, variably expressed motor symptom in people with Parkinson's disease (PwPD) with limited treatments.

OBJECTIVE

To determine if the rate of progression in spatiotemporal gait parameters in people converting from a noFOG to a FOG phenotype (FOGConv) was faster than non-convertors, and determine if gait parameters can help predict this conversion.

METHODS

PwPD were objectively monitored longitudinally, approximately every 6 months. Non-motor assessments were performed at the initial visit. Steady-state gait in the levodopa ON-state was collected using a gait mat (Protokinetics) at each visit. The rate of progression in 8 spatiotemporal gait parameters was calculated. FOG convertors (FOGConv) were classified if they did not have FOG at initial visit and developed FOG at a subsequent visit.

RESULTS

Thirty freezers (FOG) and 30 non-freezers were monitored an average of 3.5 years, with 10 non-freezers developing FOG (FOGConv). FOGConv and FOG had faster decline in mean stride-length, swing-phase-percent, and increase in mean total-double-support percent, coefficient of variability (CV) foot-strike-length and CV swing-phase-percent than the remaining non-freezers (noFOG). On univariate modeling, progression rates of mean stride-length, stride-velocity, swing-phase-percent, total-double-support-percent and of CV swing-phase-percent had high discriminative power (AUC > 0.83) for classification of the FOGConv and noFOG groups.

CONCLUSION

FOGConv had a faster temporal decline in objectively quantified gait than noFOG, and progression rates of spatiotemporal gait parameters were more predictive of FOG phenotype conversion than initial (static) parameters Objectively monitoring gait in disease prediction models may help define FOG prone groups for testing putative treatments.

Postural control of Parkinson's disease: A visualized analysis based on Citespace knowledge graph

Postural control impairment is one of the primary motor symptoms in patients with Parkinson's disease, leading to an increased risk of falling. Several studies have been conducted on postural control disorders in Parkinson's disease patients, but no relevant bibliometric analysis has been found. In this paper, the Web of Science Core Collection database was searched for 1,295 relevant papers on postural control in Parkinson's disease patients from December 2011 to December 2021. Based on the Citespace knowledge graph, these relevant papers over the last decade were analyzed from the perspectives of annual publication volume, countries and institutes cooperation, authors cooperation, dual-map overlay of journals, co-citation literature, and keywords. The purpose of this study was to explore the current research status, research hotspots, and frontiers in this field, and to provide a reference for further promoting the research on postural control in Parkinson's disease patients.

Action observation and motor imagery have no effect on balance and freezing of gait in Parkinson's disease: a randomized controlled trial

BACKGROUND

Combining action observation (AO) and motor imagery (MI) training may induce greater brain activity in areas usually involved in Parkinson's disease (PD) and lead to greater behavioral and neurophysiological effects than when used separately.

AIM

To determine the effects of combining AO, MI, and gait training on balance and freezing of gait in individuals with PD.

DESIGN

This is a single-blinded, randomized controlled clinical trial.

SETTING

Laboratory of Intervention and Analysis of Movement (LIAM) from the Department of Physical Therapy of a Brazilian University.

POPULATION

Study sample consisted of individuals diagnosed with idiopathic PD by a neurologist specialized in movement disorders.

METHODS

39 individuals with PD were divided into experimental (EG=21) and control groups (CG=18). EG performed 12 sessions of AO, MI, and gait training, whereas CG watched PD-related educational videos and performed 12 sessions of gait training. Balance (measured using the Mini Balance Evaluation Systems Test [MiniBESTest]) and freezing of gait (measured using the Freezing of Gait Questionnaire) were reassessed one day after the end of the intervention.

RESULTS

We did not observe significant intra- and intergroup differences in freezing of gait. For the EG, we observed a significant intragroup difference in the total score of MiniBESTest (F=5.2; P=0.02), and sensory orientation (F=4.5; P=0.04) and dynamic gait (F=3.6; P=0.03) domains. MiniBESTest domains were not different between groups.

CONCLUSIONS

Combining AO, MI, and gait training was not more effective than isolated gait training for balance and freezing of gait in individuals with PD.

CLINICAL REHABILITATION IMPACT

MI training can moderate AO effects and enhance motor learning when both therapies are combined. Therefore, this approach may still have the potential to be included in the treatment of PD. New studies should investigate whether the factors that influence these results are related to the protocol's sensitivity in changing the evaluated parameters or to the time and intensity of AO and MI training.

Life-space mobility, balance and self-efficacy in Parkinson's disease: a cross-sectional study

OBJECTIVE

Life-space mobility (LSM) is a mobility measure that assesses the physical and social environments through which people move during their daily lives. To characterize LSM among individuals with Parkinson's disease and explore the relationship between LSM, self-efficacy, and balance.

DESIGN

A cross-sectional study.

SETTINGS

Movement disorder clinic at a teaching hospital.

PARTICIPANTS

Eighty-eight participants with Parkinson's disease.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The dependent variable (LSM) was assessed using the Life-Space Assessment (LSA) instrument. Balance evaluation and balance self-efficacy were assessed using the Mini Balance Evaluation Systems Test (Mini-BESTest) and the Activities-Specific Balance Confidence Scale, respectively. Other variables, such as age, disease staging (Hoehn-Yahr staging system), cognition (Montreal Cognitive Assessment), and depressive symptoms (Beck Depression Inventory-II), were also measured.

RESULTS

The mean LSA score was 65.22 (SD [SD]: 22.75) and mean age was 66.99 years (SD: 9.35 years). Among the 88 patients, 35 (39.7%) were classified as restricted SM. Age (P = 0.03), disease severity (P = 0.02), cognition (P = 0.02), and motor subtype (P = 0.006) were associated with more restricted LSM among participants. A multiple linear regression model demonstrated that LSM can be predicted by balance performance (R²  = 0.377; P < 0.001).

CONCLUSIONS

Age, disease severity, cognition, motor subtype, balance self-efficacy, and balance performance are associated with LSM. Understanding and improving balance and self-efficacy in people with Parkinson's disease could facilitate community mobility and promote functional independence and health maintenance. This article is protected by copyright. All rights reserved.

Automated freezing of gait assessment with marker-based motion capture and multi-stage spatial-temporal graph convolutional neural networks

BACKGROUND

Freezing of gait (FOG) is a common and debilitating gait impairment in Parkinson's disease. Further insight into this phenomenon is hampered by the difficulty to objectively assess FOG. To meet this clinical need, this paper proposes an automated motion-capture-based FOG assessment method driven by a novel deep neural network.

METHODS

Automated FOG assessment can be formulated as an action segmentation problem, where temporal models are tasked to recognize and temporally localize the FOG segments in untrimmed motion capture trials. This paper takes a closer look at the performance of state-of-the-art action segmentation models when tasked to automatically assess FOG. Furthermore, a novel deep neural network architecture is proposed that aims to better capture the spatial and temporal dependencies than the state-of-the-art baselines. The proposed network, termed multi-stage spatial-temporal graph convolutional network (MS-GCN), combines the spatial-temporal graph convolutional network (ST-GCN) and the multi-stage temporal convolutional network (MS-TCN). The ST-GCN captures the hierarchical spatial-temporal motion among the joints inherent to motion capture, while the multi-stage component reduces over-segmentation errors by refining the predictions over multiple stages. The proposed model was validated on a dataset of fourteen freezers, fourteen non-freezers, and fourteen healthy control subjects.

RESULTS

The experiments indicate that the proposed model outperforms four state-of-the-art baselines. Moreover, FOG outcomes derived from MS-GCN predictions had an excellent (r = 0.93 [0.87, 0.97]) and moderately strong (r = 0.75 [0.55, 0.87]) linear relationship with FOG outcomes derived from manual annotations.

CONCLUSIONS

The proposed MS-GCN may provide an automated and objective alternative to labor-intensive clinician-based FOG assessment. Future work is now possible that aims to assess the generalization of MS-GCN to a larger and more varied verification cohort.

Stepping up to meet the challenge of freezing of gait in Parkinson's disease

There has been a growing appreciation for freezing of gait as a disabling symptom that causes a significant burden in Parkinson’s disease. Previous research has highlighted some of the key components that underlie the phenomenon, but these reductionist approaches have yet to lead to a paradigm shift resulting in the development of novel treatment strategies. Addressing this issue will require greater integration of multi-modal data with complex computational modeling, but there are a number of critical aspects that need to be considered before embarking on such an approach. This paper highlights where the field needs to address current gaps and shortcomings including the standardization of definitions and measurement, phenomenology and pathophysiology, as well as considering what available data exist and how future studies should be constructed to achieve the greatest potential to better understand and treat this devastating symptom.

Quantitative Gait Analysis Using a Pose-Estimation Algorithm with a Single 2D-Video of Parkinson's Disease Patients

BACKGROUND

Clinician-based rating scales or questionnaires for gait in Parkinson's disease (PD) are subjective and sensor-based analysis is limited in accessibility.

OBJECTIVE

To develop an easily accessible and objective tool to evaluate gait in PD patients, we analyzed gait from a single 2-dimensional (2D) video.

METHODS

We prospectively recorded 2D videos of PD patients (n = 16) and healthy controls (n = 15) performing the timed up and go test (TUG). The gait was simultaneously evaluated with a pressure-sensor (GAITRite). We estimated the 3D position of toes and heels with a deep-learning based pose-estimation algorithm and calculated gait parameters including step length, step length variability, gait velocity and step cadence which was validated with the result from the GAITRite. We further calculated the time and steps required for turning. Then, we applied the algorithm to previously recorded and archived videos of PD patients (n = 32) performing the TUG.

RESULTS

From the validation experiment, gait parameters derived from video tracking were in excellent agreement with the parameters obtained with the GAITRite. (Intraclass correlation coefficient > 0.9). From the analysis with the archived videos, step length, gait velocity, number of steps, and the time required for turning were significantly correlated (Absolute R > 0.4, p < 0.005) with the Freezing of gait questionnaire, Unified PD Rating scale part III total score, HY stage and postural instability. Furthermore, the video-based tracking objectively measured significant improvement of step length, gait velocity, steps and the time required for turning with antiparkinsonian medication.

CONCLUSION

2D video-based tracking could objectively evaluate gait in PD patients.

Gaps and roadmap of novel neuromodulation targets for treatment of gait in Parkinson's disease

Gait issues in Parkinson's disease (PD) are common and can be highly disabling. Although levodopa and deep brain stimulation (DBS) of the subthalamic nucleus and the globus pallidus internus have been established therapies for addressing the motor symptoms of PD, their effects on gait are less predictable and not well sustained with disease progression. Given the high prevalence of gait impairment in PD and the limitations in currently approved therapies, there has been considerable interest in alternative neuromodulation targets and techniques. These have included DBS of pedunculopontine nucleus and substantia nigra pars reticulata, spinal cord stimulation, non-invasive modulation of cortical regions and, more recently, vagus nerve stimulation. However, successes and failures have also emerged with these approaches. Current gaps and controversies are related to patient selection, optimal electrode placement within the target, placebo effects and the optimal programming parameters. Additionally, recent advances in pathophysiology of oscillation dynamics have driven new models of closed-loop DBS systems that may or may not be applicable to gait issues. Our aim is to describe approaches, especially neuromodulation procedures, and emerging challenges to address PD gait issues beyond subthalamic nucleus and the globus pallidus internus stimulation.

Imaging the neural underpinnings of freezing of gait in Parkinson’s disease

•

Review of recent (after 2012) imaging studies on Parkinsonian freezing of gait.

•

Virtual reality studies report functional decoupling of cortico-striatal circuits.

•

Motor imagery studies reveal increased recruitment of parieto-occipital regions.

•

fNIRS studies converge on reporting higher activity within prefrontal regions.

•

Imaging findings support pathophysiological models of freezing of gait.

Freezing of gait (FoG) is a paroxysmal and sporadic gait impairment that severely affects PD patients’ quality of life. This review summarizes current neuroimaging investigations that characterize the neural underpinnings of FoG in PD. The review presents and discusses the latest advances across multiple methodological domains that shed light on structural correlates, connectivity changes, and activation patterns associated with the different pathophysiological models of FoG in PD. Resting-state fMRI studies mainly report cortico-striatal decoupling and disruptions in connectivity along the dorsal stream of visuomotor processing, thus supporting the ‘interference’ and the ‘perceptual dysfunction’ models of FoG. Task-based MRI studies employing virtual reality and motor imagery paradigms reveal a disruption in functional connectivity between cortical and subcortical regions and an increased recruitment of parieto-occipital regions, thus corroborating the ‘interference’ and ‘perceptual dysfunction’ models of FoG. The main findings of fNIRS studies of actual gait primarily reveal increased recruitment of frontal areas during gait, supporting the ‘executive dysfunction’ model of FoG. Finally, we discuss how identifying the neural substrates of FoG may open new avenues to develop efficient treatment strategies.

Mediolateral Postural Control during Gait in Parkinson’s Disease

Objectives:

Balance in the mediolateral direction is usually maintained in patients with early-stage Parkinson’s disease (PD), but not in moderate-stage PD as revealed by the Tandem Gait Test. Although mediolateral postural control in PD patients remains controversial, previous studies have shown that the Tandem Gait Test may predict the risk of future falls in patients with PD. This study aimed to clarify postural control differences among PD patients with and without mediolateral balance impairments (MLBI: mediolateral balance impairments, nMLBI: non-mediolateral balance impairments, respectively) and healthy controls (HCs).

Methods:

We recruited 40 PD patients and 20 HCs. According to the Tandem Gait Test score, PD patients were divided into MLBI and nMLBI groups. Primary outcome measures were the ambulatory movement trajectory amplitude of the center of mass and its coefficient of variation (CV) during gait.

Results:

Mediolateral movement trajectory amplitudes and CV were not significantly different between the nMLBI group and HCs, whereas the mediolateral movement trajectory amplitude in the MLBI group was significantly higher than that in the nMLBI group. Moreover, the CV of the mediolateral movement trajectory amplitude in the MLBI group was significantly lower than that in the nMLBI group. The mediolateral movement trajectory amplitude was significantly correlated with the fall score.

Conclusions:

The current results suggest that PD patients with mediolateral balance impairments showed mediolateral postural sway during gait compared with PD patients without mediolateral balance impairments. It is necessary to focus on the instabilities in the mediolateral direction to avoid falls in PD patients.

Effectiveness of a Long-Term, Home-Based Aerobic Exercise Intervention on Slowing the Progression of Parkinson Disease: Design of the Cyclical Lower Extremity Exercise for Parkinson Disease II (CYCLE-II) Study

OBJECTIVE

Previous short duration studies have demonstrated that high-intensity aerobic exercise improves aspects of motor and non-motor function in people with Parkinson disease (PwPD); however, the effectiveness of a long-term exercise intervention on slowing disease progression is unknown. The primary aim of this study is to determine the disease-altering effects of high-intensity aerobic exercise, administered on an upright stationary cycle, on the progression of PD. A secondary aim is to develop a prognostic model for 12-month changes in the Movement Disorder Society Unified Parkinson's Disease Rating Scale III (MDS-UPDRS III) of PwPD undergoing an aerobic exercise intervention.

METHODS

This pragmatic, multisite, single-rater blinded, randomized controlled trial will recruit PwPD from 2 large, urban, academic medical centers. Participants (N = 250 PwPD) will be randomized to (1) home-based aerobic exercise or (2) usual and customary care. Those in the aerobic exercise arm will be asked to complete in-home aerobic exercise sessions at 60% to 80% of heart rate reserve 3 times per week for 12 months utilizing a commercially available upright exercise cycle. The usual and customary care group will continue normal activity levels. Daily activity will be monitored for both groups throughout the 12-month study period. The primary outcome, both to assess disease-modifying response to aerobic exercise and for prognostic modeling in the aerobic exercise arm, is 12-month rate of change in the MDS-UPDRS III. Clinical and biomechanical measures will also be used to assess upper and lower extremity motor function as well as non-motor functions.

IMPACT

Should long-term aerobic exercise demonstrate disease-modifying capability, this study will provide evidence that "Exercise is Medicine" for PwPD. Further, the derived prognostic model will inform a patient-specific exercise prescription for PwPD and expected effects on PD progression.

Walking on common ground: a cross-disciplinary scoping review on the clinical utility of digital mobility outcomes

Physical mobility is essential to health, and patients often rate it as a high-priority clinical outcome. Digital mobility outcomes (DMOs), such as real-world gait speed or step count, show promise as clinical measures in many medical conditions. However, current research is nascent and fragmented by discipline. This scoping review maps existing evidence on the clinical utility of DMOs, identifying commonalities across traditional disciplinary divides. In November 2019, 11 databases were searched for records investigating the validity and responsiveness of 34 DMOs in four diverse medical conditions (Parkinson's disease, multiple sclerosis, chronic obstructive pulmonary disease, hip fracture). Searches yielded 19,672 unique records. After screening, 855 records representing 775 studies were included and charted in systematic maps. Studies frequently investigated gait speed (70.4% of studies), step length (30.7%), cadence (21.4%), and daily step count (20.7%). They studied differences between healthy and pathological gait (36.4%), associations between DMOs and clinical measures (48.8%) or outcomes (4.3%), and responsiveness to interventions (26.8%). Gait speed, step length, cadence, step time and step count exhibited consistent evidence of validity and responsiveness in multiple conditions, although the evidence was inconsistent or lacking for other DMOs. If DMOs are to be adopted as mainstream tools, further work is needed to establish their predictive validity, responsiveness, and ecological validity. Cross-disciplinary efforts to align methodology and validate DMOs may facilitate their adoption into clinical practice.

Insights Into the Mini-BESTest Scoring System: Comparison of 6 Different Structural Models

OBJECTIVE

The Mini-Balance Evaluation Systems Test (Mini-BESTest) is a balance scale common to clinical practice, but different scoring has been proposed, that is, total score and/or subsections. This study aimed to investigate Mini-BESTest validity by comparing 6 structural models and to establish the best model for discriminating fallers from nonfallers, that is, those who did or did not report at least 2 falls in the 6 months before evaluation.

METHODS

In this cross-sectional validation study, data from 709 individuals with idiopathic Parkinson disease (Hoehn and Yahr stages 1-3) were analyzed. Individuals were evaluated with the Mini-BESTest, and fall history was recorded. Construct, convergent, and discriminant validity and reliability of the 6 models were analyzed. The ability of the models to adequately identify individuals with or without a history of falls was tested with receiving operating characteristic curves.

RESULTS

Confirmatory factor analysis showed that the unidimensional models and the 4-factor solutions showed the best fit indexes. Conversely, second-order models, which allowed reporting of both total and subsections, did not converge. Most models and factors showed a low convergent validity (average variance extracted values <0.5). Correlations among the anticipatory postural adjustments factor with both the sensory orientation and the dynamic gait factors of multidimensional models were high (r ≥ 0.85). Unidimensional model reliability was good, whereas low values were found in one-half of the subsections. Finally, both unidimensional models showed a large area under the receiving operating characteristic curve (0.81).

CONCLUSION

The original unidimensional Mini-BESTest model-with a total score of 28-showed the highest validity and reliability and was best at discriminating fallers from nonfallers. Conversely, its 4 subsections should not be reported separately, because they were highly correlated and had low reliability; therefore, they are not actually capable of measuring different aspects of balance.

IMPACT

This study shows that the Mini-BESTest should be used only with the original unidimensional scoring system in people with Parkinson disease.

Local field potentials in Parkinson's disease: A frequency-based review

Deep brain stimulation (DBS) surgery offers a unique opportunity to record local field potentials (LFPs), the electrophysiological population activity of neurons surrounding the depth electrode in the target area. With direct access to the subcortical activity, LFP research has provided valuable insight into disease mechanisms and cognitive processes and inspired the advent of adaptive DBS for Parkinson's disease (PD). A frequency-based framework is usually employed to interpret the implications of LFP signatures in LFP studies on PD. This approach standardizes the methodology, simplifies the interpretation of LFP patterns, and makes the results comparable across studies. Importantly, previous works have found that activity patterns do not represent disease-specific activity but rather symptom-specific or task-specific neuronal signatures that relate to the current motor, cognitive or emotional state of the patient and the underlying disease. In the present review, we aim to highlight distinguishing features of frequency-specific activities, mainly within the motor domain, recorded from DBS electrodes in patients with PD. Associations of the commonly reported frequency bands (delta, theta, alpha, beta, gamma, and high-frequency oscillations) to motor signs are discussed with respect to band-related phenomena such as individual tremor and high/low beta frequency activity, as well as dynamic transients of beta bursts. We provide an overview on how electrophysiology research in DBS patients has revealed and will continuously reveal new information about pathophysiology, symptoms, and behavior, e.g., when combining deep LFP and surface electrocorticography recordings.

Freezing of Gait in Parkinson's Disease: Risk Factors, Their Interactions, and Associated Nonmotor Symptoms

Background

Freezing of gait (FOG) is a debilitating and incompletely understood symptom in Parkinson's disease (PD).

Objective

To determine the principal clinical factors predisposing to FOG in PD, their interactions, and associated nonmotor symptoms.

Methods

164 PD subjects were assessed in a cross-sectional retrospective study, using the MDS-UPDRS scale, MMSE, and Clinical Dementia Rating Scale. Clinical factors associated with FOG were determined using univariate analysis and nominal logistic regression. Receiver operating characteristic curves were computed, to obtain measures of sensitivity and specificity of predictors of FOG. Subgroups of patients with FOG were compared with those without FOG, based on defining aspects of their clinical phenotype.

Results

Relative to non-FOG patients, those with FOG had a longer disease duration, higher PIGD and balance-gait score, higher LED, and more motor complications (p < 0.0001) and were more likely to exhibit urinary dysfunction (p < 0.0003), cognitive impairment, hallucinations, and psychosis (p=0.003). The balance-gait score and motor complications, at their optimum cutoff values, together predicted FOG with 86% accuracy. Interactions were noted between cognitive dysfunction and both the Bal-Gait score and motor complication status, cognitive impairment or dementia increasing the likelihood of FOG in subjects without motor complications (p=0.0009), but not in those with motor complications.

Conclusions

Both disease and treatment-related factors, notably LED, influence the risk of FOG in PD, with a selective influence of cognitive dysfunction in patients with balance-gait disorder but not in those with motor fluctuations. These findings may help to inform clinical management and highlight distinct subgroups of patients with PD-FOG, which are likely to differ in their network pathophysiology.

Balance alterations and reduction of pedunculopontine cholinergic neurons in early stages of parkinsonism in middle-aged rats

The purpose of the present study was to investigate balance alterations and the possible role of the cholinergic neurons in the pedunculopontine nucleus (PPN) in the early stages of a progressive animal model of Parkinson's disease (PD). Twenty-eight middle-aged (8-9 months) male Wistar rats received 4 or 10 subcutaneous vehicle (control, CTL) or reserpine (RES) injections (0.1 mg/kg). The animals were submitted to different behavioral tests. Forty-eight hours after the 4th injection, half of the animals of each group (n = 7) were perfused and submitted to immunohistochemical analysis for tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT). The remaining animals (n = 7 per group) were killed 48 h after the 10th injection. RES group presented motor deficits in the catalepsy and open field tests starting at days 12 and 20 of treatment, respectively (only for the animals that received 10 injections). On the other hand, dynamic and static balance changes were observed at earlier stages of RES treatment, starting at days 6 and 4, respectively. At this point of the treatment, there was no decrease in the number of TH immunoreactivity neurons in the substantia nigra pars compacta (SNpc), ventral tegmental area (VTA) and dorsal striatum (DS). However, a decrease was observed in SNpc and dorsal striatum of animals that received 10 injections. In contrast, there was a decrease in the number of ChAT immunoreactive cells in PPN concomitantly to the balance alterations at the early stages of treatment (after 4 RES injections). Thus, by mimicking the progressiveness of PD, the reserpine model made it possible to identify static and dynamic balance impairments prior to the motor alterations in the catalepsy and open field tests. In addition, changes in balance were accompanied by a reduction in the number of ChAT immunoreactive cells in NPP in the early stages of treatment.

Prolonged Standing Task Affects Adaptability of Postural Control in People With Parkinson's Disease

BACKGROUND

Studies on short-term upright quiet standing tasks have presented contradictory findings about postural control in people with Parkinson's disease (pwPD). Prolonged trial durations might better depict body sway and discriminate pwPD and controls.

OBJECTIVE

The aim of this study was to investigate postural control in pwPD during a prolonged standing task.

METHODS

A total of 26 pwPD and 25 neurologically healthy individuals performed 3 quiet standing trials (60 s) before completing a constrained prolonged standing task for 15 minutes. Motion capture was used to record body sway (Vicon, 100 Hz). To investigate the body sway behavior during the 15 minutes of standing, the analysis was divided into three 5-minute-long phases: early, middle, and late. The following body sway parameters were calculated for the anterior-posterior (AP) and medial-lateral (ML) directions: velocity, root-mean-square, and detrended fluctuations analysis (DFA). The body sway area was also calculated. Two-way ANOVAs (group and phases) and 1-way ANOVA (group) were used to compare these parameters for the prolonged standing and quiet standing, respectively.

RESULTS

pwPD presented smaller sway area (P < .001), less complexity (DFA; AP: P < .009; ML: P < .01), and faster velocity (AP: P < .002; ML: P < .001) of body sway compared with the control group during the prolonged standing task. Although the groups swayed similarly (no difference for sway area) during quiet standing, they presented differences in sway area during the prolonged standing task (P < .001).

CONCLUSIONS

Prolonged standing task reduced adaptability of the postural control system in pwPD. In addition, the prolonged standing task may better analyze the adaptability of the postural control system in pwPD.

The prevalence of freezing of gait in Parkinson's disease and in patients with different disease durations and severities

Background

The prevalence rates of freezing of gait (FOG) in Parkinson’s disease (PD) vary widely, ranging from 14.0 to 55.1%. Our aim is to calculate the overall prevalence of FOG in all PD patients with different disease durations and severities.

Methods

Using Medline/PubMed/Embase, we carried out a systematic literature search for studies reporting the PD and clinically relevant FOG.

Results

After primary screening, a total of 35 studies were identified and further analyzed for inclusion into the analysis, and 29 studies fulfilled the quality criteria and included in this meta-analysis. The overall prevalence of FOG in PD was 39.9% (95% CI 35.3-44.5%). The FOG identified by the freezing of gait questionnaire item 3 may be more prevalent (43.8%, 95% CI 38.5-49.1%) than the FOG identified by the Unified Parkinson’s Disease Rating Scale item 14 (36.0%, 95% CI 29.0-43.1%). Disease duration and severity are both the clinical features associated with the FOG. The highest FOG prevalence rate in PD patients was seen in patients with disease durations ≥ 10 years, at 70.8%, followed that of PD patients with disease durations ≥ 5 years (53.3%), and PD patients with disease durations < 5 years (22.4%). FOG presented in 28.4% of PD patients with Hoehn and Yahr staging (H&Y) score ≤ 2.5, and in 68.4% of PD patients with H&Y score ≥ 2.5.

Conclusion

This meta-analysis confirms that the prevalence of FOG in PD is considerable, and highlights the need for accurate identification of FOG in PD.

Mechanical Plantar Foot Stimulation in Parkinson's Disease: A Scoping Review

Background: Parkinson′s disease (PD) is the second most prevalent neurodegenerative disease in older individuals. Neurorehabilitation-based interventions such as those improving gait are crucial for a holistic approach and to limit falls. Several studies have recently shown that mechanical plantar foot stimulation is a beneficial intervention for improving gait impairment in PD patients. The objective of this scoping review is to evaluate the beneficial effects of this stimulation on gait parameters, and to analyse protocols of foot stimulation and other effects in non-motor symptoms. Relevant articles were searched in the Medline database using Pubmed and Scopus, using the primary search terms ‘foot stimulation’ OR ‘plantar stimulation’ AND ‘Parkinson’s disease*’. Several protocols have been used for mechanical plantar foot stimulation (ranging from medical devices to textured insoles). The gait parameters that have been shown to be improved are stride length and walking speed. The beneficial effects are achieved after both acute and repeated plantar foot stimulation. Beneficial effects are observed in other organs and systems, such as muscle activation, brain connectivity, cardiovascular control in the central nervous system, and the release of brain-derived neurotrophic factor and cortisol in blood added evidence about this intervention’s impact on brain function. Mechanical plantar foot stimulation is a safe and effective add-on treatment able for improving gait impairments in PD patients during the L-dopa off state. Randomized and controlled clinical trials to study its eventual potentiating effect with different pharmacotherapy regimens are warranted.

Repetitive Motor Control Deficits Most Consistent Predictors of Conversion to Freezing of Gait in Parkinson's Disease: A Prospective Cohort Study

BACKGROUND

The onset of freezing of gait (FOG) represents a turning point in the lives of patients with Parkinson's disease (PD). FOG increases fall risk and is associated with worse physical and mental health related quality of life, thus increasing disease burden. Moreover, therapeutic studies aiming to ameliorate freezing have had limited success. In a step towards pre-emptive therapy to delay or prevent the onset of FOG, this prospective cohort study set out to uncover clinical markers of conversion to FOG.

OBJECTIVE

Investigate clinical markers of conversion to FOG.

METHODS

Sixty PD patients without FOG were followed up for two years and underwent extensive clinical testing each year. FOG classification was made with the New Freezing of Gait Questionnaire. Clinical predictors of conversion to FOG were investigated using univariate analysis and through building a multivariable model using all measured components.

RESULTS

Twelve patients developed FOG during the study (Incidence: 11.5% per year). Due to the large number of predictors, univariate analyses did not survive multiple comparison correction, precluding strong inference on any one predictor. Overall, the effect sizes suggested that motor deficits including difficulties with repetitive movement scaling (AUC: 0.71), coordination (AUC: 0.73) and consistency (AUC: 0.76) as well as gait asymmetry (AUC: 0.79) and variability (AUC: 0.71) were most predictive of conversion. Further, converters reported more subjective cognitive difficulty (AUC: 0.74), although their measured performance was similar to non-converters. Multivariable analyses further showed that the two components most consistently selected in the predictive model were: 1) an MDS-UPDRS component with worse axial motor, hand use and non-motor symptoms; and 2) finger tapping abnormalities.

CONCLUSION

Conversion to FOG was predicted mainly by objective and clinical measures of motor dyscontrol, as non-motor disturbances were surfacing. Although based on a small cohort with limited converters, this novel finding informs future studies aimed at FOG prevention.

Differential Gait Decline in Parkinson's Disease Enhances Discrimination of Gait Freezers from Non-Freezers

BACKGROUND

Freezing of gait (FOG) is a debilitating feature of Parkinson's disease (PD) for which treatments are limited. To develop neuroprotective strategies, determining whether disease progression is different in phenotypic variants of PD is essential.

OBJECTIVE

To determine if freezers have a faster decline in spatiotemporal gait parameters.

METHODS

Subjects were enrolled in a longitudinal study and assessed every 3- 6 months. Continuous gait in the levodopa ON-state was collected using a gait mat (Protokinetics). The slope of change/year in spatiotemporal gait parameters was calculated.

RESULTS

26 freezers, 31 non-freezers, and 25 controls completed an average of 6 visits over 28 months. Freezers had a faster decline in mean stride-length, stride-velocity, swing-%, single-support-%, and variability in single-support-% compared to non-freezers (p < 0.05). Gait decline was not correlated with initial levodopa dose, duration of levodopa therapy, change in levodopa dose or change in Montreal Cognitive Assessment scores (p > 0.25). Gait progression parameters were required to obtain 95% accuracy in categorizing freezers and non-freezers groups in a forward step-wise binary regression model. Change in mean stride-length, mean stride-width, and swing-% variability along with initial foot-length variability, mean swing-% and apathy scores were significant variables in the model.

CONCLUSION

Freezers had a faster temporal decline in objectively quantified gait, and inclusion of longitudinal gait changes in a binary regression model greatly increased categorization accuracy. Levodopa dosing, cognitive decline and disease severity were not significant in our model. Early detection of this differential decline may help define freezing prone groups for testing putative treatments.

Neuromodulation targets pathological not physiological beta bursts during gait in Parkinson's disease

Freezing of gait (FOG) is a devastating axial motor symptom in Parkinson's disease (PD) leading to falls, institutionalization, and even death. The response of FOG to dopaminergic medication and deep brain stimulation (DBS) is complex, variable, and yet to be optimized. Fundamental gaps in the knowledge of the underlying neurobiomechanical mechanisms of FOG render this symptom one of the unsolved challenges in the treatment of PD. Subcortical neural mechanisms of gait impairment and FOG in PD are largely unknown due to the challenge of accessing deep brain circuitry and measuring neural signals in real time in freely-moving subjects. Additionally, there is a lack of gait tasks that reliably elicit FOG. Since FOG is episodic, we hypothesized that dynamic features of subthalamic (STN) beta oscillations, or beta bursts, may contribute to the Freezer phenotype in PD during gait tasks that elicit FOG. We also investigated whether STN DBS at 60 Hz or 140 Hz affected beta burst dynamics and gait impairment differently in Freezers and Non-Freezers. Synchronized STN local field potentials, from an implanted, sensing neurostimulator (Activa® PC + S, Medtronic, Inc.), and gait kinematics were recorded in 12 PD subjects, off-medication during forward walking and stepping-in-place tasks under the following randomly presented conditions: NO, 60 Hz, and 140 Hz DBS. Prolonged movement band beta burst durations differentiated Freezers from Non-Freezers, were a pathological neural feature of FOG and were shortened during DBS which improved gait. Normal gait parameters, accompanied by shorter bursts in Non-Freezers, were unchanged during DBS. The difference between the mean burst duration between hemispheres (STNs) of all individuals strongly correlated with the difference in stride time between their legs but there was no correlation between mean burst duration of each STN and stride time of the contralateral leg, suggesting an interaction between hemispheres influences gait. These results suggest that prolonged STN beta burst durations measured during gait is an important biomarker for FOG and that STN DBS modulated long not short burst durations, thereby acting to restore physiological sensorimotor information processing, while improving gait.

Balancing between the two: Are freezing of gait and postural instability in Parkinson's disease connected?

Postural instability and freezing of gait (FoG) are key features of Parkinson's disease (PD) closely related to falls. Growing evidence suggests that co-existing postural deficits could influence the occurrence and severity of FoG. To date, the exact nature of this interrelationship remains largely unknown. We analyzed the complex interaction between postural instability and gait disturbance by comparing the findings available in the posturographic literature between patients with and without FoG. Results showed that FoG and postural instability are intertwined, can influence each other behaviorally and may coincide neurologically. The most common FoG-related postural deficits included weight-shifting impairments, and inadequate scaling and timing of postural responses most apparent at forthcoming postural changes under time constraints. Most likely, a negative cycle of combined and more severe postural deficits in people with FoG will enhance postural stability breakdown. As such, the wide brain network deficiencies involved in FoG may also concurrently influence postural stability. Future work needs to examine whether training interventions targeting both symptoms will have extra clinical benefits on fall frequency.

Low to moderate relationships between gait and postural responses in Parkinson disease

OBJECTIVE

To evaluate the relationship between spatiotemporal parameters of forward and backward gait and quality of compensatory stepping responses in forward and backward directions in people with Parkinson's disease with and without freezing of gait.

DESIGN

Cross-sectional analysis.

SUBJECTS

A total of 111 individuals with mild to moderate Parkinson's disease.

METHODS

Forward and backward gait velocity and step length were evaluated using a GAITRite walkway. Forward and backward postural responses were evaluated using items from the Mini Balance Evaluation Systems Test and the Movement Disorders Society Unified Parkinson Disease Rating Scale motor subsection. Relationships between gait and postural responses were examined for the full sample and for sub-groups with and without freezing of gait.

RESULTS

There were significant (p < 0.05) low to moderate correlations between postural responses and gait overall. Correlations were similar in the freezer and non-freezer sub-groups. Freezers performed worse than non-freezers on all gait parameters and backward postural response items (p < 0.05).

CONCLUSION

Low to moderate relationships between gait and postural responses indicate the complexity of postural control and the potential involvement of different neural circuitry across these tasks. Better understanding of the relationships between gait and postural deficits in Parkinson's disease may inform the future development of targeted interventions to address these impairments.

Predicting the onset of freezing of gait: A longitudinal study

BACKGROUND

Freezing of gait is a disabling symptom of Parkinson's disease that ultimately affects approximately 80% of patients, yet very little research has focused on predicting the onset of freezing of gait and tracking the longitudinal progression of symptoms prior to its onset. The objective of the current study was to examine longitudinal data spanning the transition period when patients with PD developed freezing of gait to identify symptoms that may precede freezing and create a prediction model that identifies those "at risk" for developing freezing of gait in the year to follow.

METHODS

Two hundred and twenty-one patients with PD were divided into 3 groups (88 nonfreezers, 41 transitional freezers, and 92 continuing freezers) based on their responses to the validated Freezing of Gait-Questionnaire item 3 at baseline and follow-up. Critical measures across motor, cognitive, mood, and sleep domains were assessed at 2 times approximately 1 year apart.

RESULTS

A logistic regression model that included age, disease duration, gait symptoms, motor phenotype, attentional set-shifting, and mood measures could predict with 70% and 90% accuracy those patients who would and would not develop, respectively, freezing of gait over the next year. Notably, the Freezing of Gait-Questionnaire total and the anxiety section of the Hospital Anxiety and Depression Scale were the strongest predictors and alone could significantly predict if one might develop freezing of gait in the next 15 months with 82% accuracy.

CONCLUSIONS

Our results suggest that it is possible to identify the majority of patients who will develop freezing of gait in the following year, potentially allowing targeted interventions to delay or possibly even prevent the onset of freezing. © 2017 International Parkinson and Movement Disorder Society.

Bicycling suppresses abnormal beta synchrony in the Parkinsonian basal ganglia

OBJECTIVE

Freezing of gait is a poorly understood symptom of Parkinson disease, and can severely disrupt the locomotion of affected patients. However, bicycling ability remains surprisingly unaffected in most patients suffering from freezing, suggesting functional differences in the motor network. The purpose of this study was to characterize and contrast the oscillatory dynamics underlying bicycling and walking in the basal ganglia.

METHODS

We present the first local field potential recordings directly comparing bicycling and walking in Parkinson disease patients with electrodes implanted in the subthalamic nuclei for deep brain stimulation. Low (13-22Hz) and high (23-35Hz) beta power changes were analyzed in 22 subthalamic nuclei from 13 Parkinson disease patients (57.5 ± 5.9 years old, 4 female). The study group consisted of 5 patients with and 8 patients without freezing of gait.

RESULTS

In patients without freezing of gait, both bicycling and walking led to a suppression of subthalamic beta power (13-35Hz), and this suppression was stronger for bicycling. Freezers showed a similar pattern in general. Superimposed on this pattern, however, we observed a movement-induced, narrowband power increase around 18Hz, which was evident even in the absence of freezing.

INTERPRETATION

These results indicate that bicycling facilitates overall suppression of beta power. Furthermore, movement leads to exaggerated synchronization in the low beta band specifically within the basal ganglia of patients susceptible to freezing. Abnormal ∼18Hz oscillations are implicated in the pathophysiology of freezing of gait, and suppressing them may form a key strategy in developing potential therapies. Ann Neurol 2017;82:592-601.

Clinical balance scales indicate worse postural control in people with Parkinson's disease who exhibit freezing of gait compared to those who do not: A meta-analysis

Postural instability and freezing of gait (FOG) are key features of Parkinson's disease (PD) that are closely related to falls. Uncovering the postural control differences between individuals with and without FOG contributes to our understanding of the relationship between these phenomena. The objective of this meta-analysis was to investigate whether postural control deficits, as detected by clinical balance scales, were more apparent in FOG+ compared to FOG-. Furthermore, we aimed to identify whether different scales were equally sensitive to detect postural control deficits and whether medication affected postural control differentially in each subgroup. Relevant articles were identified via five electronic databases. We performed a meta-analysis on nine studies which reported clinical balance scale scores in 249 freezers and 321 non-freezers. Methodological analysis showed that in 5/9 studies disease duration differed between subgroups. Despite this drawback, postural control was found to be significantly worse in FOG+ compared to FOG-. All included clinical balance scales were found to be sufficiently sensitive to detect the postural control differences. Levodopa did not differentially affect postural control (p=0.21), as in both medication states FOG+ had worse postural stability than FOG-. However, this finding warrants a cautious interpretation given the limitations of the studies included. From subscore analysis, we found that reactive and dynamic postural control were the most affected postural control systems in FOG+. We conclude that our findings provide important evidence for pronounced postural instability in individuals with FOG, which can be easily picked up with clinical evaluation tools. Posturographic measures in well-matched subgroups are needed to highlight the exact nature of these deficits.

Pharmacological treatment in Parkinson's disease: Effects on gait

Gait impairments are a hallmark of Parkinson's disease (PD), both as early symptom and an important cause of disability later in the disease course. Although levodopa has been shown to improve gait speed and step length, the effect of dopamine replacement therapy on other aspects of gait is less well understood. In fact, falls are not reduced and some aspects of postural instability during gait are unresponsive to dopaminergic treatment. Moreover, many medications other than dopaminergic agents, can benefit or impair gait in people with PD. We review the effects of pharmacological interventions used in PD on gait, discriminating, whenever possible, among effects on four components of everyday mobility: straight walking, gait initiation, turning, gait adaptability. Additionally, we summarize the effects on freezing of gait. There is substantial evidence for improvement of spatial characteristics of simple, straight-ahead gait with levodopa and levodopa-enhancing drugs. Recent work suggests that drugs aiming to enhance the acetylcholine system might improve gait stability measures. There is a lack of well-designed studies to evaluate effects on more complex, but highly relevant walking abilities such as turning and making flexible adjustments to gait. Finally, paucity in the literature exists on detrimental effects of drugs used in PD that are known to worsen gait and postural stability in the elderly population.