Distal motor deficit contributions to postural instability and gait disorder in Parkinson's disease

Wearable sensor-based quantitative gait analysis in Parkinson's disease patients with different motor subtypes

Gait impairments are among the most common and disabling symptoms of Parkinson's disease and worsen as the disease progresses. Early detection and diagnosis of subtype-specific gait deficits, as well as progression monitoring, can help to implement effective and preventive personalized treatment for PD patients. Yet, the gait features have not been fully studied in PD and its motor subtypes. To characterize comprehensive and objective gait alterations and to identify the potential gait biomarkers for early diagnosis, subtype differentiation, and disease severity monitoring. We analyzed gait parameters related to upper/lower limbs, trunk and lumbar, and postural transitions from 24 tremor-dominant (TD) and 20 postural instability gait difficulty (PIGD) dominant PD patients who were in early stage and 39 matched healthy controls (HC) during the Timed Up and Go test using wearable sensors. Results show: (1) Both TD and PIGD groups showed restricted backswing range in bilateral lower extremities and more affected side (MAS) arm, reduced trunk and lumbar rotation range in the coronal plane, and low turning efficiency. The receiver operating characteristic (ROC) analysis revealed these objective gait features had high discriminative value in distinguishing both PD subtypes from the HC with the area under the curve (AUC) values of 0.7~0.9 (p < 0.01). (2) Subtle but measurable gait differences existed between TD and PIGD patients before the onset of clinically apparent gait impairment. (3) Specific gait parameters were significantly associated with disease severity in TD and PIGD subtypes. Objective gait biomarkers based on wearable sensors may facilitate timely and personalized gait treatments in PD subtypes through early diagnosis, subtype differentiation, and disease severity monitoring.

Onset of Postural Instability in Parkinson's Disease Depends on Age rather than Disease Duration

Background

Postural instability and falls are considered a major factor of impaired quality of life in patients with advanced Parkinson's disease (PD). The knowledge of the time at which postural instability occurs will help to provide the evidence required to introduce fall-prevention strategies at the right time in PD.

Objective

To investigate whether postural instability of patients with different age at disease onset is associated with age or with disease duration of PD.

Methods

Patients diagnosed with sporadic PD between 1991 and 2017 and postural instability (according to the International Parkinson and Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part III, item 3.12 postural instability) were included, with strict inclusion criteria including regular follow-ups, agreement on data use, and exclusion of comorbidities affecting the free stand.

Results

Applying these strict inclusion criteria, we included 106 patients. Those younger than 50 years at PD onset took significantly longer to develop postural instability (n = 23 patients, median: 18.4 years) compared with patients with later onset of PD (50-70 years, n = 66, median: 14.2 years, p < 0.001; and >70 years, n = 17, median: 5.7 years, p < 0.001, Kruskal-Wallis test followed by Dunn's multiple comparisons test). There was no association between total MDS-UPDRS III (as a measure of motor symptom severity) at onset of postural instability.

Conclusions

In PD, postural instability is primarily associated with the age of the patient and not with disease duration.

Efficacy of C-Mill gait training for improving walking adaptability in early and middle stages of Parkinson's disease

BACKGROUND

Walking adaptability is an obvious manifestation of Parkinson's disease (PD). Augmented reality technologies such as interactive walkways may improve walking adaptability in patients with Parkinson's Disease (PWP).

RESEARCH QUESTION

How effective is C-Mill gait adaptability training in the early and middle stages of PD for improving walking adaptability in motor subtypes of the disease?

METHODS

Fifty-two patients with early- or middle-stage PD were divided into two groups according to motor subtype (postural instability/gait disorder [PIGD] and non-PIGD) and received 7 days of training (0.5 h every day, 2 h after medication) on an augmented reality treadmill with built-in visual targets and obstacles. Functional assessments were performed before and after intervention, including posture control and walking, C-gait assessment, and participant experience. The Parkinson Disease Quality of Life questionnaire was administered at 3-month follow-up.

RESULTS

Both the PIGD (n = 29) and non-PIGD (n = 23) groups showed improved tandem walking, obstacle avoidance, and overall score in C-gait assessment and Timed Up and Go test after C-Mill training. However, there were no differences between the two groups. The PIGD group showed improvement in visually guided stepping and Speed adaptations, whereas the non-PIGD group did not improve. The non-PIGD group reported they could complete the training with less exertion after the intervention and at the 3-month follow-up, these patients reported improvement in quality of life.

SIGNIFICANCE

C-Mill gait adaptation training in the early and middle stages of PD improves walking adaptability in both motor subtypes. Cue strategies are the probable mechanism and may decrease fall risk after training. There was no difference between the groups in the improvements of perceived exertion and quality of life at follow-up. Although PIGD patients showed statistic improvements in visually guided stepping compared with non-PIGD patients, but the difference was not likely to be clinically meaningful. Specific effects of C-mill training for different types of PD were not observed in our study.

Plant Polyphenols as Neuroprotective Agents in Parkinson's Disease Targeting Oxidative Stress

Parkinson's disease (PD) is the second most prevalent progressive neurodegenerative disorder characterized by the degeneration of dopaminergic neurons in the human midbrain. Various ongoing research studies are competing to understand the pathology of PD and elucidate the mechanisms underlying neurodegeneration. Current pharmacological treatments primarily focused on improving dopamine metabolism in PD patients, despite the side effects of long-term usage. In recent years, it is recognized that oxidative stress-mediated pathways lead to neurodegeneration in the brain, which is associated with the pathophysiology of PD. The importance of oxidative stress is often less emphasized when developing potential therapeutic approaches. Natural plant antioxidants have been shown to mediate the oxidative stress-induced effects in PD, which has gained considerable attention in both in vitro and in vivo studies. Yet, clinical trials on natural polyphenol compounds are limited, restricting the potential use of these compounds as an alternative treatment for PD. Therefore, this review provides an understanding of the oxidative stress-induced effects in PD by elucidating the underlying events contributing to oxidative stress and explore the potential use of polyphenols in improving the oxidative status in PD. Preclinical findings have supported the potential of polyphenols in providing neuroprotection against oxidative stress-induced toxicity in PD. However, limiting factors, such as safety and bioavailability of polyphenols, warrant further investigations so as to make them the potential target for clinical applications in the treatment and management of PD.

Efficacy of short-term multidisciplinary intensive rehabilitation in patients with different Parkinson's disease motor subtypes: a prospective pilot study with 3-month follow-up

Parkinson's disease (PD) can be classified into three motor-based subtypes: postural instability/gait difficulty (PIGD), tremor dominant (TD), and indeterminate. The neuropathophysiological mechanisms of the three motor subtypes are different, which may lead to different responses to therapy. Sixty-nine patients with idiopathic Parkinson's disease (Hoehn-Yahr stage ≤ 3) were screened from 436 patients with Parkinsonism recruited through outpatient services and the internet. According to the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) TD/PIGD ratio, the patients were divided into PIGD (TD/PIGD ≤ 0.09; n = 36), TD (TD/PIGD ≥1.15; n = 19), and indeterminate (TD/PIGD = 0.90-1.15; n = 14) groups. All patients received 2 weeks of multidisciplinary intensive rehabilitation treatment (MIRT) during hospitalization, as well as a remote home rehabilitation health education class. Compared with the scores at admission, all patients showed significant improvements in their MDS-UPDRS III score, walking ability, balance, and posture control at discharge. Moreover, the MDS-UPDRS III score improvement was greater in the PIGD group than in the TD group. The follow-up data, collected for 3 months after discharge, showed that overall symptom improvement in each group was maintained for 1-3 months. Furthermore, there were no significant differences in the duration or grade effects of symptom improvement among the three groups. These findings suggest that 2 weeks of MIRT is effective for improving motor performance in all three motor subtypes. Patients in the PIGD group had a better response after hospitalization than those in the TD group. This study was approved by the Institutional Ethics Committee of Beijing Rehabilitation Hospital of Capital Medical University of China (approval No. 2018bkky022) on May 7, 2018 and registered with the Chinese Clinical Trial Registry (registration No. ChiCTR1900020771) on January 19, 2019.

Clinical and laboratory measures of balance and comparison of balance performances according to postural instability and gait disorders in individuals with Parkinson's disease

PURPOSE/AIM

Primary aim was to investigate the association between laboratory measures of balance and clinical balance tests in individuals with Parkinson's disease (PD). The secondary aim was to compare the balance performances according to postural instability and gait disorders (PIGD).

MATERIALS AND METHODS

Sixty-four individuals with PD were included in the study. Clinical data were investigated using modified Hoehn and Yahr Scale and Unified Parkinson's Disease Rating Scale (UPDRS). Berg Balance Scale (BBS), Timed Up&Go Test (TUG), Five Times Sit-to-Stand Test (FTSST) were used for clinical measures of balance. Laboratory measures of balance were evaluated by Balance Master System including the modified Clinical Test of Sensory Interaction of Balance (mCTSIB), Limits of Stability Test (LOS), Sit to Stand Test (STS), and Tandem Walk Test (TW). The relationship between clinical and laboratory measures of balance was determined. After participants were divided into two groups based on UPDRS: patients with and without PIGD, their balance performance was compared.

RESULTS

There were significant correlations between BBS and mCTSIB, LOS-Movement Velocity, and LOS-Endpoint Excursion. FTSST was correlated with STS-Weight Transfer and STS-Rising Index, and TUG was correlated with TW-Speed. Patients with PIGD had worse scores of balance assessments including FTSST, LOS-Movement Velocity, STS-Rising Index.

CONCLUSION

Laboratory measures are associated with clinical balance tests and they may reflect clinical balance outcome measures. Furthermore, PIGD may negatively affect balance performance in patients with PD.

Effects of the use of mobile phone on postural and locomotor tasks: a scoping review

BACKGROUND

Using a mobile phone while performing a postural and locomotor tasks is a common, daily situation. Conversing or sending messages (SMS) while walking account for a significant share of accidental injuries. Therefore, understanding the consequences of using a mobile phone on balance and walking is important, all the more so when these postural and locomotor tasks are aggravated by a disease.

RESEARCH QUESTION

Our objective was to conduct a scoping review on the influence of a dual-task situation - generated by the use of mobile phone - on users' postural and/or locomotor tasks.

METHODS

The literature search was conducted in English on PubMed/Medline and CINHAL databases, using keywords associated with postural and locomotor tasks and with the use of mobile phone. Study location, population, number of subjects, experimental design, types of phone use, evaluated postural-locomotor tasks and expected effects were then analyzed.

RESULTS AND SIGNIFICANCE

46 studies were included in this work, 24 of which came from North America. All studies compared postural and locomotor tasks with and without the use of a smartphone. Ten studies also compared at least 2 groups with different characteristics. Only 4 studies included pathological subjects. Various modalities were tested, and most studies focused on walking. Results show that the use of smartphones slows down movement and induces a systematic imbalance, except when listening to music. The dual task of "using the smartphone during a postural or locomotor tasks" induces systematic disturbances of balance and movement, which must be taken into account in the rehabilitation approach. Future studies will have to extend the knowledge regarding pathological situations.

Is Cortical Activation During Walking Different Between Parkinson’s Disease Motor Subtypes?

Parkinson’s disease (PD) is often classified into tremor dominant (TD) and postural instability gait disorder (PIGD) subtypes. Degeneration of subcortical/cortical pathways is different between PD subtypes, which leads to differences in motor behavior. However, the influence of PD subtype on cortical activity during walking remains poorly understood. Therefore, we aimed to investigate the influence of PD motor subtypes on cortical activity during unobstructed walking and obstacle avoidance. Seventeen PIGD and 19 TD patients performed unobstructed walking and obstacle avoidance conditions. Brain activity was measured using a mobile functional near-infrared spectroscopy–electroencephalography (EEG) systems, and gait parameters were analyzed using an electronic carpet. Concentrations of oxygenated hemoglobin (HbO2) of the prefrontal cortex (PFC) and EEG absolute power from alpha, beta, and gamma bands in FCz, Cz, CPz, and Oz channels were calculated. These EEG channels correspond to supplementary motor area, primary motor cortex, posterior parietal cortex, and visual cortex, respectively. Postural instability gait disorder patients presented higher PFC activity than TD patients, regardless of the walking condition. Tremor dominant patients presented reduced beta power in the Cz channel during obstacle avoidance compared to unobstructed walking. Both TD and PIGD patients decreased alpha and beta power in the FCz and CPz channels. In conclusion, PIGD patients need to recruit additional cognitive resources from the PFC for walking. Both TD and PIGD patients presented changes in the activation of brain areas related to motor/sensorimotor areas in order to maintain balance control during obstacle avoidance, being that TD patients presented further changes in the motor area (Cz channel) to avoid obstacles.

Choreographing life-experiences of balance control in people with Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a devastating neurodegenerative disorder. Reduced balance is one of the cardinal symptoms of PD, predisposing people living with PD to experience difficulties with the execution of tasks and activities, as well as hindering their involvement in meaningful life areas. The overarching aim of this study was to explore how deficits in balance control manifest in everyday life and how it is managed by people with PD (PwPD).

METHODS

Qualitative description was used as methodology, and in-depth interviews were conducted with 18 participants, between the ages of 46 to 83 years, with mild to severe PD. Interview transcripts were analyzed using qualitative content analysis, following an inductive approach.

RESULTS

One theme emerged from the analysis: Increased planning-choreographing life. Within this overarching theme, two categories were identified, namely Limitations in mobility and New restricted functioning in everyday life, each with 3-4 sub-categories. The categories described how PwPD handled decreased balance control in their everyday life by using motor and cognitive strategies as a consequence of not trusting their body's capacity to control balance. Activities in everyday life, as well as the ability to partake in leisure and social activities were profoundly affected.

CONCLUSION

People with mild to severe PD used strategies to handle decreased balance and they choreographed their lives around their individual current state of mobility and balance. The knowledge gained from this study can be used to develop targeted interventions addressing the nuances of balance deficits in everyday life.

Can Quantitative Gait Analysis Be Used to Guide Treatment of Patients with Different Subtypes of Parkinson's Disease?

PURPOSE

Gait impairment is a common clinical symptom of patients with Parkinson's disease (PD). Detecting specific gait parameters' changes in order to guide clinical intervention is at present lacking. The present study aimed to (1) quantify gait impairments in different PD subtypes and (2) explore whether the results of quantitative gait analysis are beneficial to clinical treatment.

PATIENTS AND METHODS

We enrolled 86 patients with PD (48 men, and 38 women) from the Department of Geriatrics of the Affiliated Brain Hospital of Nanjing Medical University. Unified Parkinson's Disease Rating Scale (UPDRS) and Hoehn-Yahr Scale were used to evaluate the motor symptoms of PD. All patients stopped anti-Parkinsonian medication for 24 hours (72 hours for controlled release medicine). The patients were divided into two subtypes, namely, postural instability gait difficulty (PIGD; n=56) and tremor dominant (TD; n=30) subtypes according to UPDRS. All patients completed the instrumented stand and walk test, and a set of JiBuEn gait analysis system was used in gait data collection.

RESULTS

We observed a shorter stride length (p=0.021), a longer stride time (p=0.036), a faster cadence (p=0.036), and a more variable stride length (p=0.012) in the PIGD group compared with the TD group. In addition, compared with the TD group, we found that the toe-off angle (p=0.005) and the range of motion of ankle joint (p=0.009) decreased in the PIGD group.

CONCLUSION

Our study demonstrated that the gait performance of patients with PIGD is worse than those with TD from the perspective of quantitative gait analysis. We extended previous research and found the PIGD group exhibited severe gait impairments in some specific spatiotemporal and kinematic gait parameters. The different manifestations of these gait impairments may guide in choosing appropriate treatment of patients with different PD subtypes.

IMU-Based Classification of Parkinson's Disease From Gait: A Sensitivity Analysis on Sensor Location and Feature Selection

Inertial measurement units (IMUs) have a long-lasting popularity in a variety of industrial applications from navigation systems to guidance and robotics. Their use in clinical practice is now becoming more common, thanks to miniaturization and the ability to integrate on-board computational and decision-support features. IMU-based gait analysis is a paradigm of this evolving process, and in this study its use for the assessment of Parkinson's disease (PD) is comprehensively analyzed. Data coming from 25 individuals with different levels of PD symptoms severity and an equal number of age-matched healthy individuals were included into a set of 6 different machine learning (ML) techniques, processing 18 different configurations of gait parameters taken from 8 IMU sensors. Classification accuracy was calculated for each configuration and ML technique, adding two meta-classifiers based on the results obtained from all individual techniques through majority of voting, with two different weighting schemes. Average classification accuracy ranged between 63% and 80% among classifiers and increased up to 96% for one meta-classifier configuration. Configurations based on a statistical preselection process showed the highest average classification accuracy. When reducing the number of sensors, features based on the joint range of motion were more accurate than those based on spatio-temporal parameters. In particular, best results were obtained with the knee range of motion, calculated with four IMUs, placed bilaterally. The obtained findings provide data-driven evidence on which combination of sensor configurations and classification methods to be used during IMU-based gait analysis to grade the severity level of PD.

Head and trunk stability during gait before and after levodopa intake in Parkinson's disease subtypes

INTRODUCTION

People with Parkinson's disease (PD) can be classified into tremor dominant (TD) and postural instability and gait difficulty (PIGD) subtypes; the latter group having more impaired gait and increased fall risk. While there is some evidence that anti-parkinsonian medication, levodopa, might not improve balance and gait control or reduce fall risk in the PIGD subtype, it is unclear whether the levodopa dosage intake affects gait stability. To address these issues, this study used accelerometry to compare gait stability: (i) during before and after levodopa intake between non-PIGD and PIGD subtypes; (ii) between individuals who took less or >750 mg of levodopa/day.

METHODS

In 15 non-PIGD (Combination of 13 TD patients and 2 classified as indeterminate subtype) and 23 PIGD participants of similar mean (SD) age ((63.0 (7.6) versus 62.6 (10.0) years, respectively)) and disease-duration (8.9 (8.9) versus 11.3 (4.6) years, respectively), head and trunk stability during gait was examined using anteroposterior, vertical and mediolateral acceleration harmonic ratios (HRs). Participants were assessed before and after a levodopa dose, during typical "off" and "on" periods, respectively.

RESULTS

Two-way analyses of variance (group × medication status) revealed that compared to the non-PIGD subgroup, the PIGD subgroup showed significantly worse head stability (lower anteroposterior HR) in the "off" state, and significantly worse pelvis stability (significantly lower mediolateral and vertical HRs) in the "on" state (p < 0.05 for both). Levodopa was effective in treating most of the disease-related impairments (not bradykinesia) in both groups, (p < 0.05) but improved gait stability (lowered pelvis mediolateral and vertical HRs) only in people with the non-PIGD subtype (p < 0.05) and those taking <750 mg of levodopa/day (p < 0.05).

CONCLUSIONS

People with the PD PIGD subtype exhibit impaired gait stability that is not improved and frequently worsened by levodopa. New non-pharmaceutical approaches, technological (e.g. cueing) or exercise-based (e.g. balance training) are required to improve or compensate for mediolateral gait instability in this subtype and ultimately prevent falls.

Objective measures of unobstructed walking and obstacle avoidance in Parkinson's disease subtypes

BACKGROUND

Objective measures of gait in Parkinson's disease (PD) patients according to motor subtypes are not yet fully understood. Although recent advances have been made for unobstructed walking, further work is required on locomotor tasks challenging postural stability, such as obstacle avoidance.

RESEARCH QUESTION

This study aimed to investigate the influence of PD motor subtypes on objective measures of locomotion during unobstructed walking and obstacle avoidance.

METHODS

Thirty-five PD patients classified as postural instability and gait disorder (PIGD) and 30 as tremor dominant (TD), as well as 45 healthy controls (CG) walked along an 8-m pathway under two conditions: (a) unobstructed walking and (b) obstacle avoidance. Outcome measures included spatiotemporal parameters recorded by an optoelectronic tridimensional system.

RESULTS

During unobstructed walking, the PIGD group exhibited shorter stride length, slower velocity, and longer double support phase compared to the TD and CG groups. The TD group also presented slower stride velocity compared to the CG. The PIGD and TD groups presented shorter stride duration than the CG. Regarding obstacle avoidance, the PIGD group exhibited shorter distances for leading foot placement before obstacle, trailing foot placement after obstacle and trailing crossing step length compared to the TD and CG groups. The PIGD group exhibited wider leading crossing step width, lower trailing toe clearance, and slower leading and trailing velocity during obstacle avoidance compared to the CG.

SIGNIFICANCE

PIGD subtype patients showed worse modifications in objective measures of unobstructed walking and obstacle avoidance. The observed modifications may contribute to increased fall occurrence in PIGD patients.

Curved Walking Rehabilitation with a Rotating Treadmill in Patients with Parkinson's Disease: A Proof of Concept

Training subjects to step-in-place eyes open on a rotating platform while maintaining a fixed body orientation in space [podokinetic stimulation (PKS)] produces a posteffect consisting in inadvertent turning around while stepping-in-place eyes closed [podokinetic after-rotation (PKAR)]. Since the rationale for rehabilitation of curved walking in Parkinson's disease is not fully known, we tested the hypothesis that repeated PKS favors the production of curved walking in these patients, who are uneasy with turning, even when straight walking is little affected. Fifteen patients participated in 10 training sessions distributed in 3 weeks. Both counterclockwise and clockwise PKS were randomly administered in each session. PKS velocity and duration were gradually increased over sessions. The velocity and duration of the following PKAR were assessed. All patients showed PKAR, which increased progressively in peak velocity and duration. In addition, before and at the end of the treatment, all patients walked overground along linear and circular trajectories. Post-training, the velocity of walking bouts increased, more so for the circular than the linear trajectory. Cadence was not affected. This study has shown that parkinsonian patients learn to produce turning while stepping when faced with appropriate training and that this capacity translates into improved overground curved walking.

Virtual reality for rehabilitation in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder that is best managed by a combination of medication and regular physiotherapy. In this context, virtual reality (VR) technology is proposed as a new rehabilitation tool with a possible added value over traditional physiotherapy approaches. It potentially optimises motor learning in a safe environment, and by replicating real-life scenarios could help improve functional activities of daily living.

OBJECTIVES

The objective of this review was to summarise the current best evidence for the effectiveness of VR interventions for the rehabilitation of people with PD in comparison with 1) active interventions, and 2) passive interventions. Our primary goal was to determine the effect of VR training on gait and balance. Secondary goals included examining the effects of VR on global motor function, activities of daily living, quality of life, cognitive function, exercise adherence, and the occurrence of adverse events.

SEARCH METHODS

We identified relevant articles through electronic searches of the Cochrane Movement Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library), MEDLINE, Embase, CINAHL, the Physiotherapy Evidence Database (PEDro), online trials registers, and by handsearching reference lists. We carried out all searches up until 26 November 2016.

SELECTION CRITERIA

We searched for randomised and quasi-randomised controlled trials of VR exercise interventions in people with PD. We included only trials where motor rehabilitation was the primary goal.

DATA COLLECTION AND ANALYSIS

Two review authors independently searched for trials that corresponded to the predefined inclusion criteria. We independently extracted and assessed all data for methodological quality. A third review author was responsible for conflict resolution when required.

MAIN RESULTS

We included 8 trials involving 263 people with PD in the review. Risk of bias was unclear or high for all but one of the included studies. Study sample sizes were small, and there was a large amount of heterogeneity between trials with regard to study design and the outcome measures used. As a result, we graded the quality of the evidence as low or very low. Most of the studies intended to improve motor function using commercially available devices, which were compared with physiotherapy. The interventions lasted for between 4 and 12 weeks.In comparison to physiotherapy, VR may lead to a moderate improvement in step and stride length (standardised mean difference (SMD) 0.69, 95% confidence interval (CI) 0.30 to 1.08; 3 studies; 106 participants; low-quality evidence). VR and physiotherapy interventions may have similar effects on gait (SMD 0.20, 95% CI -0.14 to 0.55; 4 studies; 129 participants; low-quality evidence), balance (SMD 0.34, 95% CI -0.04 to 0.71; 5 studies; 155 participants; low-quality evidence), and quality of life (mean difference 3.73 units, 95% CI -2.16 to 9.61; 4 studies; 106 participants). VR interventions did not lead to any reported adverse events, and exercise adherence did not differ between VR and other intervention arms.The evidence available comparing VR exercise with a passive control was more limited. The evidence for the main outcomes of interest was of very low quality due to the very small sample sizes of the two studies available for this comparison.

AUTHORS' CONCLUSIONS

We found low-quality evidence of a positive effect of short-term VR exercise on step and stride length. VR and physiotherapy may have similar effects on gait, balance, and quality of life. The evidence available comparing VR with passive control interventions was more limited. Additional high-quality, large-scale studies are needed to confirm these findings.

Conflicting and non-conflicting visual cues lead to error in gait initiation and gait inhibition in individuals with freezing of gait

INTRODUCTION

We asked whether conflicting visual cues influences gait initiation, gait inhibition and postural control in Parkinson's disease (PD) between freezers, non-freezers and healthy older adults.

METHODS

Twenty-five PD participants on dopaminergic medication and 17 healthy older adults were asked to initiate or refrain gait depending on visual cues: green GO (GG), green STOP (GS), red GO (RG), red STOP (RS). Center of pressure (CoP) displacement, variability and mean velocity (VCoP) in the anterior-posterior (AP) and medial-lateral (ML) directions and movement time (MT) were measured.

RESULTS

Gait initiation: Both freezers and non-freezers were different from controls in GG and GS. In GS, freezers had smaller CoP displacement and velocity in both directions (p<0.01), while non-freezers had smaller VCoP in AP and ML (p<0.01). AP CoP displacement in GS was smaller in freezers compared to non-freezers (p<0.05). Freezers had longer MT compared to controls in GG and compared to both groups in GS (p<0.01). Gait inhibition: Controls and freezers had larger CoP displacement variability (p<0.05) and velocity (p<0.01) in both directions in RG compared to RS. No differences were seen in non-freezers. Three freezers initiated walking during the RG or RS conditions.

CONCLUSION

Freezers were in general slower at initiating gait, displayed a more restrictive postural strategy and were more affected by the conflicting conditions compared to both controls and non-freezers. In freezers, the conflicting visual cues may have increased the cognitive load enough to provoke delays in processing the visual information and implementing the appropriate motor program.

Structural Brain Alterations in Motor Subtypes of Parkinson's Disease: Evidence from Probabilistic Tractography and Shape Analysis

BACKGROUND AND OBJECTIVES

The postural instability and gait disorder (PIGD) and tremor dominant (TD) subtypes of Parkinson's disease (PD) show different patterns of alterations in functional connectivity (FC) between specific brain regions. This study aimed to investigate the relation between symptomatic heterogeneity in PD and structural alterations underlying these FC changes.

METHODS

68 PD patients classified as PIGD (n = 41) or TD (n = 19) and 19 age-matched controls underwent Magnetic Resonance Imaging (MRI). Diffusion-weighted images were used to assess fractional anisotropy (FA) and mean diffusivity (MD) at the whole-brain level using tract-based spatial statistics (TBSS). In addition, structural connectivity was assessed between regions that previously showed altered FC using probabilistic tractography. Anatomical images were used to determine shape and volume of the putamen, caudate and pallidum.

RESULTS

TBSS revealed widespread FA reductions in PIGD compared to controls involving the superior longitudinal fasciculi and corpus callosum. No such differences were found in TD. Both PD subgroups had increased MD compared to controls in tracts connecting the left caudate with the bilateral ventral putamen. TD patients additionally showed increased MD compared to PIGD and controls in tracts connecting the right inferior parietal lobule with the right premotor and primary motor cortex, which previously showed altered FC. We also found grey matter atrophy in the rostrodorsal head of the caudate in PIGD compared to controls.

CONCLUSION

Microstructural changes in white matter tracts, particularly in those connecting striatal sub-areas, partly underlie FC alterations in PD subtypes. Caudate shape alterations further implicate the striatum in PIGD pathophysiology.

Handwriting Impairments in People With Parkinson's Disease and Freezing of Gait

BACKGROUND

Recent studies show that patients with Parkinson's disease (PD) and freezing of gait (FOG) experience motor problems outside their gait freezing episodes. Because handwriting is also a sequential movement, it may be affected in PD patients with FOG relative to those without.

OBJECTIVE

The current study aimed to assess the quality of writing in PD patients with and without FOG in comparison to healthy controls (CTs) during various writing tasks.

METHODS

Handwriting was assessed by the writing of cursive loops on a touch-sensitive writing tablet and by means of the Systematic Screening of Handwriting Difficulties (SOS) test in 30 PD patients with and without freezing and 15 healthy age-matched CTs. The tablet tests were performed at 2 different sizes, either continuously or alternatingly, as indicated by visual target lines.

RESULTS

Patients with freezing showed decreased writing amplitudes and increased variability compared with CTs and patients without freezing on the writing tablet tests. Writing problems were present during both tests but were more pronounced during writing at alternating compared with writing at continuous size. Patients with freezing also had a higher total score on the SOS test than patients without freezing and CTs, reflecting more extensive handwriting problems, particularly with writing fluency.

CONCLUSIONS

Writing is more severely affected in PD patients with FOG than in those without FOG. These results indicate that deficient movement sequencing and adaptation is a generic problem in patients with FOG.

Functional connectivity alterations in the motor and fronto-parietal network relate to behavioral heterogeneity in Parkinson's disease

BACKGROUND

Insight into the neural mechanisms of postural instability and gait disorder (PIGD) and tremor dominant (TD) subtypes in Parkinson's disease (PD) is indispensable for generating pathophysiology hypotheses underlying this phenotyping. This cross-sectional study aimed to gain insight in specific and brain-wide functional connectivity (FC) and its correlation with motor deterioration and preservation in PD subtypes.

METHODS

68 PD patients classified as PIGD (n = 41), TD (n = 19) or indeterminate (n = 8) and 19 age-matched controls underwent resting-state fMRI while 'off' medication to assess FC between regions of interest (ROIs) in the motor and fronto-parietal network and on a whole-brain level using a parcellated template. FC alterations were correlated with quantitative behavioral measures.

RESULTS

ROI-analyses showed decreased FC between the caudate and putamen in PIGD compared to TD. This hypo-connectivity was correlated with behavioral impairment. In contrast, TD-specific hyper-connectivity between motor cortical areas and the inferior parietal lobule correlated with less behavioral impairment, suggesting compensatory mechanisms. Both subgroups showed hyper-connectivity between the left supplementary motor area and pedunculopontine nucleus, whereas PIGD-specific right lateralized hyper-connectivity was shown between this nucleus and the premotor cortex. Whole-brain analyses revealed 65% hypo-connectivity and 35% hyper-connectivity in PIGD compared to TD. TD also revealed primarily hypo-connectivity compared to controls, but had more pronounced hyper-connectivity involving temporo-occipital areas.

CONCLUSION

This multilevel analysis showed differential connectivity alterations in large scale neural networks and between motor and cognitive control areas that related to behavioral heterogeneity in PD, underscoring the classic TD-PIGD phenotypical classification.