Is freezing of gait in Parkinson's disease a result of multiple gait impairments? Implications for treatment

Soft robotic apparel to avert freezing of gait in Parkinson's disease

Freezing of gait (FoG) is a profoundly disruptive gait disturbance in Parkinson's disease, causing unintended stops while walking. Therapies for FoG reveal modest and transient effects, resulting in a lack of effective treatments. Here we show proof of concept that FoG can be averted using soft robotic apparel that augments hip flexion. The wearable garment uses cable-driven actuators and sensors, generating assistive moments in concert with biological muscles. In this n-of-1 trial with five repeated measurements spanning 6 months, a 73-year-old male with Parkinson's disease and substantial FoG demonstrated a robust response to robotic apparel. With assistance, FoG was instantaneously eliminated during indoor walking (0% versus 39 ± 16% time spent freezing when unassisted), accompanied by 49 ± 11 m (+55%) farther walking compared to unassisted walking, faster speeds (+0.18 m s-1) and improved gait quality (-25% in gait variability). FoG-targeting effects were repeatable across multiple days, provoking conditions and environment contexts, demonstrating potential for community use. This study demonstrated that FoG was averted using soft robotic apparel in an individual with Parkinson's disease, serving as an impetus for technological advancements in response to this serious yet unmet need.

Digital measures of freezing of gait across the spectrum of normal, non-freezers, possible freezers and definite freezers

Over the course of the disease, freezing of gait (FoG) will gradually impact over 80% of people with Parkinson's disease (PD). Clinical decision-making and research design are often based on classification of patients as 'freezers' or 'non-freezers'. We derived an objective measure of FoG severity from inertial sensors on the legs to examine the continuum of FoG from absent to possible and severe in people with PD and in healthy controls. One hundred and forty-seven people with PD (Off-medication) and 83 healthy control subjects turned 360° in-place for 1 minute while wearing three wearable sensors used to calculate a novel Freezing Index. People with PD were classified as: 'definite freezers', new FoG questionnaire (NFOGQ) score > 0 and clinically observed FoG; 'non-freezers', NFOGQ = 0 and no clinically observed FoG; and 'possible freezers', either NFOGQ > 0 but no FoG observed or NFOGQ = 0 but FoG observed. Linear mixed models were used to investigate differences in participant characteristics among groups. The Freezing Index significantly increased from healthy controls to non-freezers to possible freezers and to definite freezers and showed, in average, excellent test-retest reliability (ICC = 0.89). Unlike the Freezing Index, sway, gait and turning impairments were similar across non-freezers, possible and definite freezers. The Freezing Index was significantly related to NFOG-Q, disease duration, severity, balance confidence, and the SCOPA-Cog (p < 0.01). An increase in the Freezing Index, objectively assessed with wearable sensors during a turning- in-place test, may help identify prodromal FoG in people with PD prior to clinically-observable or patient-perceived freezing. Future work should follow objective measures of FoG longitudinally.

Freezing of gait in Chinese patients with multiple system atrophy: prevalence and risk factors

Objective

Freezing of gait (FOG) is common in neurodegenerative forms of atypical parkinsonism, but few studies have examined FOG in multiple system atrophy (MSA). In this study, we examined the prevalence of freezing of gait and its relationship to clinical features in a large cohort of Chinese MSA patients.

Methods

This exploratory study included 202 Chinese patients with probable MSA. FOG was defined as a score ≥ 1 on item 14 of the Unified Parkinson's Disease Rating Scale. Patients with or without FOG were compared in terms of the Unified MSA Rating Scale (UMSARS) as well as cognitive and neuropsychiatric assessments.

Results

The frequency of FOG was 48.0, 52.1, and 38.7% in MSA, MSA with predominant parkinsonism (MSA-P), and MSA with predominant cerebellar ataxia (MSA-C), respectively. FOG was associated with worse subscores on parts I, II and IV of the UMSARS as well as worse total UMSARS score; greater likelihood of speech difficulties, falls, gait impairment and balance disorder; more severe symptoms of anxiety and depression; and lower activities of daily living. The binary logistic regression model indicated that higher total UMSARS scores were associated with FOG in MSA, MSA-P, and MSA-C patients.

Conclusion

Freezing of gait may be common among Chinese MSA patients, FOG may correlate with severe motor symptoms, anxiety, depression and activities of daily living. Total UMSARS score may be an independent risk factor for FOG.

Alpha Synuclein Modulates Mitochondrial Ca 2+ Uptake from ER During Cell Stimulation and Under Stress Conditions

Alpha synuclein (a-syn) is an intrinsically disordered protein prevalent in neurons, and aggregated forms are associated with synucleinopathies including Parkinson' disease (PD). Despite the biomedical importance and extensive studies, the physiological role of a-syn and its participation in etiology of PD remain uncertain. We showed previously in model RBL cells that a-syn colocalizes with mitochondrial membranes, depending on formation of N-terminal helices and increasing with mitochondrial stress. 1 We have now characterized this colocalization and functional correlates in RBL, HEK293, and N2a cells. We find that expression of a-syn enhances stimulated mitochondrial uptake of Ca 2+ from the ER, depending on formation of its N-terminal helices but not on its disordered C-terminal tail. Our results are consistent with a-syn acting as a tether between mitochondria and ER, and we show increased contacts between these two organelles using structured illumination microscopy. We tested mitochondrial stress caused by toxins related to PD, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP/MPP+) and carbonyl cyanide m-chlorophenyl hydrazone (CCCP), and found that a-syn prevents recovery of stimulated mitochondrial Ca 2+ uptake. The C-terminal tail, and not N-terminal helices, is involved in this inhibitory activity, which is abrogated when phosphorylation site serine-129 is mutated (S129A). Correspondingly, we find that MPTP/MPP+ and CCCP stress is accompanied by both phosphorylation (pS129) and aggregation of a-syn. Overall, our results indicate that a-syn can participate as a tethering protein to modulate Ca 2+ flux between ER and mitochondria, with potential physiological significance. A-syn can also prevent cellular recovery from toxin-induced mitochondrial dysfunction, which may represent a pathological role of a-syn in the etiology of PD.

White matter hyperintensities burden in the frontal regions is positively correlated to the freezing of gait in Parkinson's disease

Objective

Previous studies have reported that white matter hyperintensities (WMHs) are associated with freezing of gait (FOG), but it is not clear whether their distribution areas have correlations with FOG in Parkinson's disease (PD) and the potential influencing factors about WMHs.

Methods

Two hundred and forty-six patients with PD who underwent brain MRI were included. Participants were divided into PD with FOG (n = 111) and PD without FOG (n = 135) groups. Scheltens score was used to assess the WMHs burden in the areas of deep white matter hyperintensities (DWMHs), periventricular hyperintensities (PVHs), basal ganglia hyperintensities (BGHs), and infratentorial foci of hyperintensities (ITF). Whole brain WMHs volume was evaluated by automatic segmentation. Binary logistic regression was used to evaluate relationships between WMHs and FOG. The common cerebrovascular risk factors that may affect WMHs were evaluated by mediation analysis.

Results

There were no statistical differences between PD with and without FOG groups in whole brain WMHs volume, total Scheltens score, BGHs, and ITF. Binary logistic regression showed that the total scores of DWMHs (OR = 1.094; 95% CI, 1.001, 1.195; p = 0.047), sum scores of PVHs and DWMHs (OR = 1.080; 95% CI, 1.003, 1.164; p = 0.042), especially the DWMHs in frontal (OR = 1.263; 95% CI, 1.060, 1.505 p = 0.009), and PVHs in frontal caps (OR = 2.699; 95% CI, 1.337, 5.450; p = 0.006) were associated with FOG. Age, hypertension, and serum alkaline phosphatase (ALP) are positively correlated with scores of DWMHs in frontal and PVHs in frontal caps.

Conclusion

These results indicate that WMHs distribution areas especially in the frontal of DWMHs and PVHs play a role in PD patients with FOG.

Single-textured insole for the less affected leg in freezing of gait: A hypothesis

Freezing of gait (FoG) is one of the most widely distributed and disabling gait phenomena in people with Parkinson's disease (PD). The current therapeutic interventions show suboptimal efficacy in FoG. Lower extremity proprioception impairments, especially in the most affected leg, gait initiation hesitation, and gait asymmetry are FoG factors, and there is a need to accurately consider them in terms of therapeutic approaches. Accordingly, we hypothesize that using a single-textured insole for the less affected leg may improve FoG by providing proprioceptive stimulation that enhances sensory processing and reduces gait hesitation and asymmetry. Proprioceptive sensory stimulation for the less affected limb could be more effective than for the double legs that are currently used in rehabilitation settings due to the sensory processing in the less affected basal ganglia being better.

Effect of music-based movement therapy on the freezing of gait in patients with Parkinson’s disease: A randomized controlled trial

Background

Progression of freezing of gait (FOG), a common pathological gait in Parkinson’s disease (PD), has been shown to be an important risk factor for falls, loss of independent living ability, and reduced quality of life. However, previous evidence indicated poor efficacy of medicine and surgery in treating FOG in patients with PD. Music-based movement therapy (MMT), which entails listening to music while exercising, has been proposed as a treatment to improve patients’ motor function, emotions, and physiological activity. In recent years, MMT has been widely used to treat movement disorders in neurological diseases with promising results. Results from our earlier pilot study revealed that MMT could relieve FOG and improve the quality of life for patients with PD.

Objective

To explore the effect of MMT on FOG in patients with PD.

Materials and methods

This was a prospective, evaluator-blinded, randomized controlled study. A total of 81 participants were randomly divided into music-based movement therapy group (MMT, n = 27), exercise therapy group (ET, n = 27), and control group (n = 27). Participants in the MMT group were treated with MMT five times (1 h at a time) every week for 4 weeks. Subjects in the ET group were intervened in the same way as the MMT group, but without music. Routine rehabilitation treatment was performed on participants in all groups. The primary outcome was the change of FOG in patients with PD. Secondary evaluation indicators included FOG-Questionnaire (FOG-Q) and the comprehensive motor function.

Results

After 4 weeks of intervention, the double support time, the cadence, the max flexion of knee in stance, the max hip extension, the flexion moment of knee in stance, the comprehensive motor function (UPDRS Part III gait-related items total score, arising from chair, freezing of gait, postural stability, posture, MDS-UPDRS Part II gait-related items total score, getting out of bed/a car/deep chair, walking and balance, freezing), and the FOG-Q in the MMT group were lower than that in the control group and ET group (p < 0.05). The gait velocity, the max ankle dorsiflexion in stance, ankle range of motion (ROM) during push-off, ankle ROM over gait cycle, the knee ROM over gait cycle, and the max extensor moment in stance (ankle, knee) in the MMT group were higher than that in the control group and ET group (p < 0.05). However, no significant difference was reported between the control group and ET group (p > 0.05). The stride length and hip ROM over gait cycle in the MMT group were higher than that in the control group (p < 0.05), and the max knee extension in stance in the MMT group was lower than that in the control group (p < 0.05). Nevertheless, there was no significant difference between the ET group and MMT group (p > 0.05) or control group (p > 0.05).

Conclusion

MMT improved gait disorders in PD patients with FOG, thereby improving their comprehensive motor function.

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.

The Grey Area of Freezing of Gait Annotation: a Guideline and Open‐source Practical Tool

Background

Freezing of gait, a disabling episodic symptom, is difficult to assess as the exact begin‐ and endpoint of an episode is not easy to specify. This hampers scientific and clinical progress. The current golden standard is video annotation by two independent raters. However, the comparison of the two ratings gives rise to non‐overlapping, gray areas.

Objective

To provide a guideline for dealing with these gray areas.

Methods/Results

We propose a standardized procedure for handling the gray areas based on two parameters, the tolerance and correction parameter. Furthermore, we recommend the use of positive agreement, negative agreement, and prevalence index to report interrater agreement instead of the commonly used intraclass correlation coefficient or Cohen's kappa. This theoretical guideline was implemented in an open‐source practical tool, FOGtool (https://github.com/helenacockx/FOGtool).

Conclusion

This paper aims to contribute to the standardization of freezing of gait assessment, thereby improving data sharing procedures and replicability of study results.

Constructing Prediction Models for Freezing of Gait by Nomogram and Machine Learning: A Longitudinal Study

Objectives: Although risk factors for freezing of gait (FOG) have been reported, there are still few prediction models based on cohorts that predict FOG. This 1-year longitudinal study was aimed to identify the clinical measurements closely linked with FOG in Chinese patients with Parkinson's disease (PD) and construct prediction models based on those clinical measurements using Cox regression and machine learning. Methods: The study enrolled 967 PD patients without FOG in the Hoehn and Yahr (H&Y) stage 1-3 at baseline. The development of FOG during follow-up was the end-point. Neurologists trained in movement disorders collected information from the patients on a PD medication regimen and their clinical characteristics. The cohort was assessed on the same clinical scales, and the baseline characteristics were recorded and compared. After the patients were divided into the training set and test set by the stratified random sampling method, prediction models were constructed using Cox regression and random forests (RF). Results: At the end of the study, 26.4% (255/967) of the patients suffered from FOG. Patients with FOG had significantly longer disease duration, greater age at baseline and H&Y stage, lower proportion in Tremor Dominant (TD) subtype, a higher proportion in wearing-off, levodopa equivalent daily dosage (LEDD), usage of L-Dopa and catechol-O-methyltransferase (COMT) inhibitors, a higher score in scales of Unified Parkinson's Disease Rate Scale (UPDRS), 39-item Parkinson's Disease Questionnaire (PDQ-39), Non-Motor Symptoms Scale (NMSS), Hamilton Depression Rating Scale (HDRS)-17, Parkinson's Fatigue Scale (PFS), rapid eye movement sleep behavior disorder questionnaire-Hong Kong (RBDQ-HK), Epworth Sleepiness Scale (ESS), and a lower score in scales of Parkinson's Disease Sleep Scale (PDSS) (P < 0.05). The risk factors associated with FOG included PD onset not being under the age of 50 years, a lower degree of tremor symptom, impaired activities of daily living (ADL), UPDRS item 30 posture instability, unexplained weight loss, and a higher degree of fatigue. The concordance index (C-index) was 0.68 for the training set (for internal validation) and 0.71 for the test set (for external validation) of the nomogram prediction model, which showed a good predictive ability for patients in different survival times. The RF model also performed well, the C-index was 0.74 for the test set, and the AUC was 0.74. Conclusions: The study found some new risk factors associated with the FOG including a lower degree of tremor symptom, unexplained weight loss, and a higher degree of fatigue through a longitudinal study, and constructed relatively acceptable prediction models.

Application of Wavelet in Quantitative Evaluation of Gait Events of Parkinson's Disease

RESULTS

Systems detected FOG and other gait postures and showed time-frequency range by examining differentiated decomposed signals by DWT. Energy distribution and PSD graph proved the accuracy of the system. Validation is done by the LOSO method which shows 90% accuracy for the proposed method.

CONCLUSION

Observations of the clinical trials validate the proposed technique. In comparison to the previous techniques reported in literature, it is seen that the proposed method shows improvement in time and frequency resolution as well as processing time.

Modelling and identification of characteristic kinematic features preceding freezing of gait with convolutional neural networks and layer-wise relevance propagation

BACKGROUND

Although deep neural networks (DNNs) are showing state of the art performance in clinical gait analysis, they are considered to be black-box algorithms. In other words, there is a lack of direct understanding of a DNN's ability to identify relevant features, hindering clinical acceptance. Interpretability methods have been developed to ameliorate this concern by providing a way to explain DNN predictions.

METHODS

This paper proposes the use of an interpretability method to explain DNN decisions for classifying the movement that precedes freezing of gait (FOG), one of the most debilitating symptoms of Parkinson's disease (PD). The proposed two-stage pipeline consists of (1) a convolutional neural network (CNN) to model the reduction of movement present before a FOG episode, and (2) layer-wise relevance propagation (LRP) to visualize the underlying features that the CNN perceives as important to model the pathology. The CNN was trained with the sagittal plane kinematics from a motion capture dataset of fourteen PD patients with FOG. The robustness of the model predictions and learned features was further assessed on fourteen PD patients without FOG and fourteen age-matched healthy controls.

RESULTS

The CNN proved highly accurate in modelling the movement that precedes FOG, with 86.8% of the strides being correctly identified. However, the CNN model was unable to model the movement for one of the seven patients that froze during the protocol. The LRP interpretability case study shows that (1) the kinematic features perceived as most relevant by the CNN are the reduced peak knee flexion and the fixed ankle dorsiflexion during the swing phase, (2) very little relevance for FOG is observed in the PD patients without FOG and the healthy control subjects, and (3) the poor predictive performance of one subject is attributed to the patient's unique and severely flexed gait signature.

CONCLUSIONS

The proposed pipeline can aid clinicians in explaining DNN decisions in clinical gait analysis and aid machine learning practitioners in assessing the generalization of their models by ensuring that the predictions are based on meaningful kinematic features.

Current Perspectives on the Assessment and Management of Gait Disorders in Parkinson's Disease

Gait dysfunction is a key defining feature of Parkinson's disease (PD), and is associated with symptoms of freezing and an increased risk of falls. In this narrative review, we cover the putative mechanisms of gait dysfunction in PD, the assessment of gait abnormalities, and the management of symptoms caused by the inherent difficulty in walking. Our understanding of the causes of gait problems in PD has progressed in recent times, moving from neurocognitive theory to correlates of affected neuronal pathways. In particular, this can be shown to correspond with abnormalities in responses to dual-task paradigms and dysfunction in cholinergic signaling. Great progress has been made in the sophistication and precision of gait assessment; however, it has firmly remained in the research domain. There is significant momentum behind wearable technologies that can be used by patients in their own environment, acting as digital biomarkers that can not only reflect progression but also independently discriminate PD from non-PD individuals. The treatment of gait dysfunction has historically relied on physical therapies and training combined with a view to mitigating the impact of such consequences as falls. Pharmacological therapies that are the mainstay of treatment in PD have tended to address symptoms like bradykinesia; however, optimization of dopaminergic therapies likely has a positive effect on quality of gait. Other targets have been assessed with the goal of improving gait, of which medications that improve cholinergic signaling appear most promising. Neuromodulation techniques are increasingly used in the form of deep-brain stimulation; however, standard targets, such as the globus pallidus interna, have a modest effect on gait. Considerable benefit has been seen through targeting the pedunculopontine nucleus, and a dual-target approach may be warranted. Stimulation of the spinal cord and brain through direct or magnetic approaches has been assessed, but requires further evidence.

Key gait findings for diagnosing three syndromic categories of dynamic instability in patients with balance disorders

With the emergence of affordable, clinical-orientated gait analysis techniques, clinicians may benefit from a general understanding of quantitative gait analysis procedures and their clinical applications. This article provides an overview of the potential of a quantitative gait analysis for decision support in three clinically relevant scenarios of early stage gait disorders: scenario I: gait ataxia and unsteadiness; scenario II: hypokinesia and slow gait; scenario III: apparently normal gait with a specific fall tendency in complex mobility situations. In a first part, we justify the advantages of standardized data collection and analysis procedures including data normalization and dimensionality reduction techniques that facilitate clinical interpretability of instrument-based gait profiles. We then outline typical patterns of pathological gait and their modulation during different walking conditions (variation of speed, sensory perturbation, and dual tasking) and highlight key aspects that are particularly helpful to support and guide clinical decision-making.

Freezing of gait in Parkinson's disease: pathophysiology, risk factors and treatments

Background

Freezing of gait (FOG) is a common, disabling symptom of Parkinson's disease (PD), but the mechanisms and treatments of FOG remain great challenges for clinicians and researchers. The main focus of this review is to summarize the possible mechanisms underlying FOG, the risk factors for screening and predicting the onset of FOG, and the clinical trials involving various therapeutic strategies. In addition, the limitations and recommendations for future research design are also discussed.

Main body

In the mechanism section, we briefly introduced the physiological process of gait control and hypotheses about the mechanism of FOG. In the risk factor section, gait disorders, PIGD phenotype, lower striatal DAT uptake were found to be independent risk factors of FOG with consistent evidence. In the treatment section, we summarized the clinical trials of pharmacological and non-pharmacological treatments. Despite the limited effectiveness of current medications for FOG, especially levodopa resistant FOG, there were some drugs that showed promise such as istradefylline and rasagiline. Non-pharmacological treatments encompass invasive brain and spinal cord stimulation, noninvasive repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) and vagus nerve stimulation (VNS), and physiotherapeutic approaches including cues and other training strategies. Several novel therapeutic strategies seem to be effective, such as rTMS over supplementary motor area (SMA), dual-site DBS, spinal cord stimulation (SCS) and VNS. Of physiotherapy, wearable cueing devices seem to be generally effective and promising.

Conclusion

FOG model hypotheses are helpful for better understanding and characterizing FOG and they provide clues for further research exploration. Several risk factors of FOG have been identified, but need combinatorial optimization for predicting FOG more precisely. Although firm conclusions cannot be drawn on therapeutic efficacy, the literature suggested that some therapeutic strategies showed promise.

The pedunculopontine nucleus: From posture and locomotion to neuroepigenetics

In this review, we discuss first an example of one of the symptoms of PD, freezing of gait (FOG), then we will turn to the use of deep brain stimulation (DBS) of the pedunculopontine nucleus (PPN) to treat PD, and the original studies that led to identification of the PPN as one source of locomotor control and why stimulation frequency is critical, and then describe the intrinsic properties of PPN neurons that require beta/gamma stimulation in order to fully activate all types of PPN neurons. Finally, we will describe recent findings on the proteomic and molecular consequences of gamma band activity in PPN neurons, with emphasis on the potential neuroepigenetic sequelae. These considerations will provide essential information for the appropriate refining and testing of PPN DBS as a potential therapy for PD, as well as alternative options.

Exercise for Parkinson's disease

Parkinson's disease is the second most common neurodegenerative disease with a prevalence rate of 1-2 per 1000 of the population worldwide. Pharmacological management is the mainstay of treatment. Despite optimal medication, motor impairment particularly balance and gait impairment persist leading to various degree of disability and reduced quality-of-life. The present review describes motor impairment including postural impairment, gait dysfunction, reduced muscle strength and aerobic capacity and falls. Physical therapy and complementary exercises have been proven to improve motor performance and functional mobility. Evidence on the efficacy of physical therapy and complementary exercises is presented in this review. These exercises include gait training with cues, gait training with treadmill, Nordic walking, brisk walking, balance training, virtual reality interventions, Tai Chi and dance. All these treatment interventions produce short-term beneficial effects and some interventions demonstrate long-term benefit. Gait training with treadmill enhance walking performance and the effects sustain for 3-6 months. Balance training improves balance, function and reduces fall rate, and these effects carry over to at least 12 months after training ended. Sustained Tai Chi for 6 months, dance therapy for 12 months, progressive resistive training for 24 months alleviates the PD motor symptoms, suggesting that they could slow down PD progression. Based on this evidence, individuals with PD are encouraged to sustain their training in order to improve/maintain their physical ability and to combat the progression of PD.

Split-belt treadmill walking in patients with Parkinson's disease: A systematic review

BACKGROUND

Walking on a split-belt treadmill (SBT) can help to modulate an asymmetric gait, particularly for people with neurological conditions, such as Parkinson's disease (PD), where asymmetry plays a role due to the laterality of the disease.

RESEARCH QUESTION

This systematic review critically evaluates the literature on SBT in PD. First, different SBT paradigms and methodological approaches were evaluated. Second, the review explored how people with PD adapt their gait to different SBT conditions compared to healthy controls (HC).

METHODS

We conducted a systematic search of the PubMED, PsychINFO, and Web of Knowledge databases. Original research articles, published in English and investigating SBT walking in people with PD, were included.

RESULTS

From the 925 studies originally identified, seven met the inclusion criteria and were selected for evaluation (n = 118 individuals with PD of whom 44 had freezing of gait (FOG)). The SBT paradigms varied across studies regarding the SBT settings, definitions of gait variables, and criteria for determining dominance of body side. Gait variability and bilateral coordination were found to adapt to the SBT condition similarly in people with PD and healthy controls (HC). Inconsistent results were found with respect to the adaptation of gait asymmetry, for the differences between PD and HC participants. The subgroup of people with PD and FOG showed reduced accuracy in detecting belt speed differences and slower adaptation to SBT conditions.

CONCLUSION

Individuals with mild to moderately severe PD adapted similarly to HCs to SBT walking for gait variability and bilateral gait coordination. However, those with FOG had impaired perception of belt speed differences and did not adapt their gait so readily. Although SBT can be useful for modulating gait asymmetry in some people with PD, it was not beneficial for all. We recommend standardization of SBT protocols for clinical practice in future studies.

Increasing Robustness in the Detection of Freezing of Gait in Parkinson’s Disease

This paper focuses on detecting freezing of gait in Parkinson’s patients using body-worn accelerometers. In this study, we analyzed the robustness of four feature sets, two of which are new features adapted from speech processing: mel frequency cepstral coefficients and quality assessment metrics. For classification based on these features, we compared random forest, multilayer perceptron, hidden Markov models, and deep neural networks. These algorithms were evaluated using a leave-one-subject-out (LOSO) cross validation to match the situation where a system is being constructed for patients for whom there is no training data. This evaluation was performed using the Daphnet dataset, which includes recordings from ten patients using three accelerometers situated on the ankle, knee, and lower back. We obtained a reduction from 17.3% to 12.5% of the equal error rate compared to the previous best results using this dataset and LOSO testing. For high levels of sensitivity (such as 0.95), the specificity increased from 0.63 to 0.75. The biggest improvement across all of the feature sets and algorithms tested in this study was obtained by integrating information from longer periods of time in a deep neural network with convolutional layers.

Moderate Frequency Resistance and Balance Training Do Not Improve Freezing of Gait in Parkinson's Disease: A Pilot Study

Background and Aim: Individuals with Parkinson's disease (PD) and Freezing of Gait (FOG) have impaired postural control, which relate to the severity of FOG. The aim of this study was to analyze whether a moderate frequency resistance (RT) and balance training (BT), respectively, are effective to diminish FOG.

Methods: This post-hoc sub-analysis of a randomized controlled training intervention study of PD patients with and without FOG reports about results from FOG patients. Twelve FOG patients performed RT and 8 BT (training 2x/week, 7 weeks). Testing was performed prior and post intervention. FOG was assessed with the FOG Questionnaire (FOGQ) and with the FOG score of a FOG provoking walking course. Balance performance was evaluated with the Fullerton Advanced Balance (FAB) scale. Tests were conducted by raters blinded to group allocation and assessment time point (only FOG score and FAB scale).

Results: For the FOGQ and FOG score, no significant differences were found within and between the two training groups (p > 0.05) and effect sizes for the improvements were small (r < 0.1). Groups did not significantly improve in the FAB scale. FOG score changes and FAB scale changes within the RT group showed a trend toward significant negative correlation (Rho = −0.553, p = 0.098).

Conclusions: Moderate frequency RT and BT was not effective in reducing FOG in this pilot study. The trend toward negative correlation between changes in FOG score and FAB scale suggests an interaction between balance (improvement) and FOG (improvement). Future studies should include larger samples and high frequency interventions to investigate the role of training balance performance to reduce the severity of FOG.

Efficacy of intensive multidisciplinary rehabilitation in Parkinson's disease: a randomised controlled study

OBJECTIVE

To evaluate whether a 4-week multidisciplinary, aerobic, motor-cognitive and intensive rehabilitation treatment (MIRT) improves the quality of life (QoL) of patients with Parkinson's disease (PD), in the short-term and long-term period.

METHODS

This is a prospective, parallel-group, single-centre, single-blind, randomised clinical trial (ClinicalTrials.gov NCT02756676). 186 patients with PD, assigned to experimental group, underwent MIRT; conversely, 48 patients, assigned to control group, did not receive rehabilitation. Parkinson's Disease Questionnaire-39 was assessed 2 (T0), 10 (T1) and 18 (T2, only experimental group) weeks after the enrolment. We compared T1 versus T0 scores within subjects and delta scores (T1-T0) between subjects. To investigate the long-term effects, we compared T2 and T0 scores in the experimental group.

RESULTS

At T0, no between-group differences in the Global Index Score (GBI) were observed (experimental group: 43.6±21.4, controls: 41.6±22.9, P=0.50). At T1, we did not find significant changes in controls (delta score: 1.2±9.9, P=0.23), and we found an improvement in GBI in the experimental group (delta score: -8.3±18.0, P<0.0001), significant also between subjects (P<0.0001). Comparing T2 versus T0 in the experimental group, the GBI maintained a significant improvement (delta score: -4.8±17.5, P<0.0001).

CONCLUSIONS

A rehabilitation treatment such as MIRT could improve QoL in patients with PD in the short-term and long-term period. Even though the single-blind design and the possible role of the placebo effect on the conclusive results must be considered as limitations of this study, the improvement in outcome measure, also maintained after a 3-month follow-up period, suggests the effectiveness of MIRT on the QoL.

CLINICAL TRIAL REGISTRATION

NCT02756676: Pre-results.

Exercise for people with Parkinson's: a practical approach

Exercise is key to a healthy and productive life. For people with Parkinson's, exercise has reported benefits for controlling motor and non-motor symptoms alongside the use of pharmacological intervention. For example, exercise prolongs independent mobility and improves sleep, mood, memory and quality of life, all further enhanced through socialisation and multidisciplinary team support. Recent research suggests that optimally prescribed exercise programmes following diagnosis may alter neurophysiological processes, possibly slowing symptom progression.Given its benefits, professionals should encourage and motivate people with Parkinson's to exercise regularly from the time of diagnosis and provide guidance on what exercise to do. We provide examples of how the growing body of evidence on exercise for people with Parkinson's is revolutionising the services they are provided. We also highlight new resources available to help the wider support network (people such as volunteers, partners and friends of people with Parkinson's) with an interest in exercise promote a consistent message on the benefits of exercise.

Increased foot strike variability in Parkinson's disease patients with freezing of gait

INTRODUCTION

Freezing of gait (FOG) is a debilitating, late motor complication of Parkinson's disease (PD) that occurs in 50-80% of patients. Gait freezing significantly worsens quality of life by decreasing mobility and increasing falls. Studies have shown that patients with episodic freezing episodes also have deficits in continuous gait. We evaluated whether there was an objective gait correlate to the increased stumbling reported by many patients with gait freezing.

METHODS

PD subjects and healthy controls (HC) were enrolled after IRB approval. Subjects with more than 1 fall/day or a Montreal Cognitive Assessment score <10 were excluded. Subjects walked at their normal pace, 8 lengths of a 20 × 4 foot pressure-sensor mat. Data was collected and analyzed using PKMAS software (Protokinetics) and statistical analysis performed using SPSS 22 (IBM).

RESULTS

72 age matched subjects (22 PD FOG, 27 PD no-FOG, and 23 HC) were enrolled. Disease duration and Hoehn & Yahr scores were not significantly different between the PD groups. Mean dimensions of foot strike were not significantly different between groups, but PD FOG subjects had increased step-to-step variability in foot strike as measured by the percent coefficient of variation (%CV) in foot strike length compared to PD no-FOG and HC, independent of stride velocity. In PD no-FOG subjects, fallers also had higher variability in foot strike length compared to non-fallers.

CONCLUSION

PD subjects with FOG had increased variability in foot strike suggesting that in addition to stride length variability, foot strike variability could contribute to imbalance leading to falls.

Alterations in white matter network topology contribute to freezing of gait in Parkinson's disease

Freezing of gait (FOG) is a common symptom in advanced Parkinson's disease (PD). Despite current advances, the neural mechanisms underpinning this disturbance remain poorly understood. To this end, we investigated the structural organisation of the white matter connectome in PD freezers and PD non-freezers. We hypothesized that freezers would show an altered network architecture, which could hinder the effective information processing that characterizes the disorder. Twenty-six freezers and twenty-four well-matched non-freezers were included in this study. Using diffusion tensor imaging, we investigated the modularity and integration of the regional connectome by calculating the module degree z score and the participation coefficient, respectively. Compared to non-freezers, freezers demonstrated lower participation coefficients in the right caudate, thalamus, and hippocampus, as well as within superior frontal and parietal cortical regions. Importantly, several of these nodes were found within the brain's 'rich club'. Furthermore, group differences in module degree z scores within cortical frontal and sensory processing areas were found. Together, our results suggest that changes in the structural network topology contribute to the manifestation of FOG in PD, specifically due to a lack of structural integration between key information processing hubs of the brain.

Identification of Characteristic Motor Patterns Preceding Freezing of Gait in Parkinson's Disease Using Wearable Sensors

Freezing of gait (FOG) is a disabling symptom that is common among patients with advanced Parkinson’s disease (PD). External cues such as rhythmic auditory stimulation can help PD patients experiencing freezing to resume walking. Wearable systems for automatic freezing detection have been recently developed. However, these systems detect a FOG episode after it has happened. Instead, in this study, a new approach for the prediction of FOG (before it actually happens) is presented. Prediction of FOG might enable preventive cueing, reducing the likelihood that FOG will occur. Moreover, understanding the causes and circumstances of FOG is still an open research problem. Hence, a quantitative characterization of movement patterns just before FOG (the pre-FOG phase) is of great importance. In this study, wearable inertial sensors were used to identify and quantify the characteristics of gait during the pre-FOG phase and compare them with the characteristics of gait that do not precede FOG. The hypothesis of this study is based on the threshold-based model of FOG, which suggests that before FOG occurs, there is a degradation of the gait pattern. Eleven PD subjects were analyzed. Six features extracted from movement signals recorded by inertial sensors showed significant differences between gait and pre-FOG. A classification algorithm was developed in order to test if it is feasible to predict FOG (i.e., detect it before it happens). The aim of the classification procedure was to identify the pre-FOG phase. Results confirm that there is a degradation of gait occurring before freezing. Results also provide preliminary evidence on the feasibility of creating an automatic algorithm to predict FOG. Although some limitations are present, this study shows promising findings for characterizing and identifying pre-FOG patterns, another step toward a better understanding, prediction, and prevention of this disabling symptom.

l-DOPA and Freezing of Gait in Parkinson's Disease: Objective Assessment through a Wearable Wireless System

Freezing of gait (FOG) is a leading cause of falls and fractures in Parkinson’s disease (PD). The episodic and rather unpredictable occurrence of FOG, coupled with the variable response to l-DOPA of this gait disorder, makes the objective evaluation of FOG severity a major clinical challenge in the therapeutic management of patients with PD. The aim of this study was to examine and compare gait, clinically and objectively, in patients with PD, with and without FOG, by means of a new wearable system. We also assessed the effect of l-DOPA on FOG severity and specific spatiotemporal gait parameters in patients with and without FOG. To this purpose, we recruited 28 patients with FOG, 16 patients without FOG, and 16 healthy subjects. In all participants, gait was evaluated clinically by video recordings and objectively by means of the wearable wireless system, during a modified 3-m Timed Up and Go (TUG) test. All patients performed the modified TUG test under and not under dopaminergic therapy (ON and OFF therapy). By comparing instrumental data with the clinical identification of FOG based on offline video-recordings, we also assessed the performance of the wearable system to detect FOG automatically in terms of sensitivity, specificity, positive and negative predictive values, and finally accuracy. TUG duration was longer in patients than in controls, and the amount of gait abnormalities was prominent in patients with FOG compared with those without FOG. l-DOPA improved gait significantly in patients with PD and particularly in patients with FOG mainly by reducing FOG duration and increasing specific spatiotemporal gait parameters. Finally, the overall wireless system performance in automatic FOG detection was characterized by excellent sensitivity (93.41%), specificity (98.51%), positive predictive value (89.55%), negative predictive value (97.31%), and finally accuracy (98.51%). Our study overall provides new information on the beneficial effect of l-DOPA on FOG severity and specific spatiotemporal gait parameters as objectively measured by a wearable sensory system. The algorithm here reported potentially opens to objective long-time sensing of FOG episodes in patients with PD.

Cerebellar theta burst stimulation does not improve freezing of gait in patients with Parkinson's disease

Freezing of gait (FOG) in Parkinson’s disease (PD) likely results from dysfunction within a complex neural gait circuitry involving multiple brain regions. Herein, cerebellar activity is increased in patients compared to healthy subjects. This cerebellar involvement has been proposed to be compensatory. We hypothesized that patients with FOG would have a reduced ability to recruit the cerebellum to compensate for dysfunction in other brain areas. In this study cerebellar activity was modified unilaterally by either excitatory or inhibitory theta burst stimulation (TBS), applied during two separate sessions. The ipsilateral cerebellar hemisphere, corresponding to the body side most affected by PD, was stimulated. Seventeen patients with PD showing ‘off’ state FOG participated. The presence of FOG was verified objectively upon inclusion. We monitored gait and bimanual rhythmic upper limb movements before and directly after TBS. Gait was evaluated with a FOG-provoking protocol, including rapid 360° turns and a 10-m walking test with small fast steps. Upper limb movement performance was evaluated with a repetitive finger flexion–extension task. TBS did not affect the amount of freezing during walking or finger tapping. However, TBS did increase gait speed when walking with small steps, and decreased gait speed when walking as fast as possible with a normal step size. The changes in gait speed were not accompanied by changes in corticospinal excitability of M1. Unilateral cerebellar TBS did not improve FOG. However, changes in gait speed were found which suggests a role of the cerebellum in PD.

Freezing of Gait in Parkinson's Disease: Its Pathophysiology and Pragmatic Approaches to Management

Background

Freezing of gait (FOG) in Parkinson's disease (PD) is poorly understood; however, with the established understanding of basal ganglia function, its manifestations should be more easily interpretable. This review examines freezing of gait (FOG) from such a perspective.

Methods

A search of the MEDLINE and EMBASE databases from the year 2000 onward for review articles, focused on the pathophysiology of FOG, was used to determine current concepts. A previously established model of basal ganglia function was used to determine the concepts' validities. At the core of the model are deficits in motor set maintenance and timing cue production for automatic movement. It includes the shift between attention and automation to the predominant attention control of gait in PD.

Results

The difficulties of the found concepts to explain FOG stem from failure to characterize different FOG components, from the assumption that all components share a similar pathophysiology, from a failure to separate basic deficits from compensatory mechanisms, and from the assumption that cognitive deficits are the cause of FOG rather than representing an inadequate compensation to FOG. Pragmatic approaches to management use the attention shift, with the provision of visual information about correct amplitude of step to correct initiation deficits, and motor blocks during gait. It also emphasizes the need to prevent step length reduction on turns, environmental situations, and cognitive overload.

Conclusion

The concept of automatic deficits in set maintenance and cue production best describe FOG manifestations in PD and, with the use of attention, the concept also provides pragmatic strategies for management.

Cognitive Contributions to Freezing of Gait in Parkinson Disease: Implications for Physical Rehabilitation

People with Parkinson disease (PD) who show freezing of gait also have dysfunction in cognitive domains that interact with mobility. Specifically, freezing of gait is associated with executive dysfunction involving response inhibition, divided attention or switching attention, and visuospatial function. The neural control impairments leading to freezing of gait have recently been attributed to higher-level, executive and attentional cortical processes involved in coordinating posture and gait rather than to lower-level, sensorimotor impairments. To date, rehabilitation for freezing of gait primarily has focused on compensatory mobility training to overcome freezing events, such as sensory cueing and voluntary step planning. Recently, a few interventions have focused on restitutive, rather than compensatory, therapy. Given the documented impairments in executive function specific to patients with PD who freeze and increasing evidence of overlap between cognitive and motor function, incorporating cognitive challenges with mobility training may have important benefits for patients with freezing of gait. Thus, a novel theoretical framework is proposed for exercise interventions that jointly address both the specific cognitive and mobility challenges of people with PD who freeze.

Impaired Retention of Motor Learning of Writing Skills in Patients with Parkinson's Disease with Freezing of Gait

Background

Patients with Parkinson’s disease (PD) and freezing of gait (FOG) suffer from more impaired motor and cognitive functioning than their non-freezing counterparts. This underlies an even higher need for targeted rehabilitation programs in this group. However, so far it is unclear whether FOG affects the ability for consolidation and generalization of motor learning and thus the efficacy of rehabilitation.

Objective

To investigate the hallmarks of motor learning in people with FOG compared to those without by comparing the effects of an intensive motor learning program to improve handwriting.

Methods

Thirty five patients with PD, including 19 without and 16 with FOG received six weeks of handwriting training consisting of exercises provided on paper and on a touch-sensitive writing tablet. Writing training was based on single- and dual-task writing and was supported by means of visual target zones. To investigate automatization, generalization and retention of learning, writing performance was assessed before and after training in the presence and absence of cues and dual tasking and after a six-week retention period. Writing amplitude was measured as primary outcome measure and variability of writing and dual-task accuracy as secondary outcomes.

Results

Significant learning effects were present on all outcome measures in both groups, both for writing under single- and dual-task conditions. However, the gains in writing amplitude were not retained after a retention period of six weeks without training in the patient group without FOG. Furthermore, patients with FOG were highly dependent on the visual target zones, reflecting reduced generalization of learning in this group.

Conclusions

Although short-term learning effects were present in both groups, generalization and retention of motor learning were specifically impaired in patients with PD and FOG. The results of this study underscore the importance of individualized rehabilitation protocols.

Freezing of Swallowing

Background

Swallowing deficits and freezing phenomena represent severe parkinsonian features. Freezing as a symptom occurring during swallowing has not been reported on yet.

Methods

We report on 3 patients with probable PSP-parkinsonism (PSP-P) who manifested freezing of swallowing (FOS).

Results

All 3 patients experienced severe weight loss in recent months. At examination, 1 patient had freezing of gait. Video fluoroscopy showed nonfunctional trembling movements of the tongue and palate during chewing and volitional swallowing, with a 6- to 8-Hz frequency that is typical for freezing episodes during walking and finger tapping. These freezing episodes were accompanied by impaired oral bolus transportation. The pharyngeal phase was not relevantly affected.

Conclusions

FOS represents a novel disease feature of PSP-P. The feature may have fundamental, but potentially treatable, consequences for patients' health and quality of life and may be considered in patients with degenerative parkinsonism who experience severe and unexplained weight loss.

Modeling falls in Parkinson's disease: Slow gait, freezing episodes and falls in rats with extensive striatal dopamine loss

Falls in patients with Parkinson's disease (PD) are a major and levodopa-unresponsive source of morbidity. We previously described an animal model of falls resulting from impairments in attentional-motor interactions. Reproducing the multisystem dopaminergic-cholinergic cell loss in patients with a history for falls, partial loss of striatal dopamine innervation interacted with loss of forebrain cholinergic neurons to generate falls that was hypothesized to reflect impairments in the attentional control of gait and balance and the sequencing of complex movements [1]. As clinical evidence also indicates that basal ganglia dopamine (DA) loss per se is associated with severe discoordination and thus a greater risk for falls, here we demonstrate that relatively extensive striatal DA loss, in contrast to the lack of effects of smaller, dorsal striatal DA losses and sham lesions, increased falls and slips and caused slowing while traversing dynamic surfaces. Falls in large DA rats were associated specifically with spontaneous or slip-triggered stoppages of forward movement. Collectively, the evidence suggests that low motivation or vigor for movement in general, and for initiating corrective movements in particular, are major sources for falls in rats with large DA losses. Falls are a result of complex cognitive-motor interactions, and rats with large DA losses model the impact of a propensity for freezing of gait when traversing dynamic surfaces.

Does anxiety cause freezing of gait in Parkinson's disease?

Individuals with Parkinson's disease (PD) commonly experience freezing of gait under time constraints, in narrow spaces, and in the dark. One commonality between these different situations is that they may all provoke anxiety, yet anxiety has never been directly examined as a cause of FOG. In this study, virtual reality was used to induce anxiety and evaluate whether it directly causes FOG. Fourteen patients with PD and freezing of gait (Freezers) and 17 PD without freezing of gait (Non-Freezers) were instructed to walk in two virtual environments: (i) across a plank that was located on the ground (LOW), (ii) across a plank above a deep pit (HIGH). Multiple synchronized motion capture cameras updated participants' movement through the virtual environment in real-time, while their gait was recorded. Anxiety levels were evaluated after each trial using self-assessment manikins. Freezers performed the experiment on two separate occasions (in their ON and OFF state). Freezers reported higher levels of anxiety compared to Non-Freezers (p < 0.001) and all patients reported greater levels of anxiety when walking across the HIGH plank compared to the LOW (p < 0.001). Freezers experienced significantly more freezing of gait episodes (p = 0.013) and spent a significantly greater percentage of each trial frozen (p = 0.005) when crossing the HIGH plank. This finding was even more pronounced when comparing Freezers in their OFF state. Freezers also had greater step length variability in the HIGH compared to the LOW condition, while the step length variability in Non-Freezers did not change. In conclusion, this was the first study to directly compare freezing of gait in anxious and non-anxious situations. These results present strong evidence that anxiety is an important mechanism underlying freezing of gait and supports the notion that the limbic system may have a profound contribution to freezing in PD.

Classification of gait disturbances: distinguishing between continuous and episodic changes

The increased awareness of the importance of gait and postural control to quality of life and functional independence has led many research groups to study the pathophysiology, epidemiology, clinical, and therapeutic aspects of these motor functions. In recognition of the increased awareness of the significance of this topic, the Movement Disorders journal is devoting this entire issue to gait and postural control. Leading research groups provide critical reviews of the current knowledge and propose future directions for this evolving field. The intensive work in this area throughout the world has created an urgent need for a unified language. Because gait and postural disturbances are so common, the clinical classification should be clear, straightforward, and simple to use. As an introduction to this special issue, we propose a new clinically based classification scheme that is organized according to the dominant observed disturbance, while taking into account the results of a basic neurological exam. The proposed classification differentiates between continuous and episodic gait disturbances because this subdivision has important ramifications from the functional, prognostic, and mechanistic perspectives. We anticipate that research into gait and postural control will continue to flourish over the next decade as the search for new ways of promoting mobility and independence aims to keep up with the exponentially growing population of aging older adults. Hopefully, this new classification scheme and the articles focusing on gait and postural control in this special issue of the Movement Disorders journal will help to facilitate future investigations in this exciting, rapidly growing area.

Sequence and onset of whole-body coordination when turning in response to a visual trigger: comparing people with Parkinson's disease and healthy adults

Turning round is a routine everyday activity that can often lead to instability. The purpose of this study was to investigate abnormalities of turning among people with Parkinson's disease (PwPD) through the measurement of sequence of body segments and latency response. Participants were asked to turn 180° and whole-body movements were recorded using CODAmotion and Visio Fast eye tracking equipment. Thirty-one independently mobile PwPD and 15 age-matched healthy controls participated in the study. We found that contrary to common belief, the head preceded movement of all other body segments (eyes, shoulders, pelvis, first and second foot). We also found interaction between group and body segment (P=0.005), indicating that overall, PwPD took longer to move from head to second foot than age-matched healthy controls. For PwPD only, interactions were found between disease severity and body segment (P<0.0001), between age group and body segment (P<0.0001) and between gender and body segments (P<0.0001). For each interaction, longer time periods were noted between moving the first foot after the pelvis, and moving the second foot after the first, and this was noted for PwPD in Hoehn and Yahr stage III-IV (in comparison to Hoehn and Yahr stage I-II); for PwPD who were under 70 years (in comparison with 70 years or over); and for ladies (in comparison with men). Our results indicate that in PwPD and healthy elderly, turning-on-the-spot might not follow the top-to-bottom approach we know from previous research.

Modeling fall propensity in Parkinson's disease: deficits in the attentional control of complex movements in rats with cortical-cholinergic and striatal-dopaminergic deafferentation

Cognitive symptoms, complex movement deficits, and increased propensity for falls are interrelated and levodopa-unresponsive symptoms in patients with Parkinson's disease (PD). We developed a test system for the assessment of fall propensity in rats and tested the hypothesis that interactions between loss of cortical cholinergic and striatal dopaminergic afferents increase fall propensity. Rats were trained to traverse stationary and rotating rods, placed horizontally or at inclines, and while exposed to distractors. Rats also performed an operant Sustained Attention Task (SAT). Partial cortical cholinergic and/or caudate dopaminergic deafferentation were produced by bilateral infusions of 192 IgG-saporin (SAP) into the basal forebrain and/or 6-hydroxydopamine (6-OHDA) into the caudate nucleus, respectively, modeling the lesions seen in early PD. Rats with dual cholinergic-dopaminergic lesions (DL) fell more frequently than SAP or 6-OHDA rats. Falls in DL rats were associated with incomplete rebalancing after slips and low traversal speed. Ladder rung walking and pasta handling performance did not indicate sensorimotor deficits. SAT performance was impaired in DL and SAP rats; however, SAT performance and falls were correlated only in DL rats. Furthermore, in DL rats, but not in rats with only dopaminergic lesions, the placement and size of dopaminergic lesion correlated significantly with fall rates. The results support the hypothesis that after dual cholinergic-dopaminergic lesions, attentional resources can no longer be recruited to compensate for diminished striatal control of complex movement, thereby "unmasking" impaired striatal control of complex movements and yielding falls.

Upper extremity freezing and dyscoordination in Parkinson's disease: effects of amplitude and cadence manipulations

Purpose. Motor freezing, the inability to produce effective movement, is associated with decreasing amplitude, hastening of movement, and poor coordination. We investigated how manipulations of movement amplitude and cadence affect upper extremity (UE) coordination as measured by the phase coordination index (PCI)-only previously measured in gait-and freezing of the upper extremity (FO-UE) in people with Parkinson's disease (PD) who experience freezing of gait (PD + FOG), do not experience FOG (PD-FOG), and healthy controls. Methods. Twenty-seven participants with PD and 18 healthy older adults made alternating bimanual movements between targets under four conditions: Baseline; Fast; Small; SmallFast. Kinematic data were recorded and analyzed for PCI and FO-UE events. PCI and FO-UE were compared across groups and conditions. Correlations between UE PCI, gait PCI, FO-UE, and Freezing of Gait Questionnaire (FOG-Q) were determined. Results. PD + FOG had poorer coordination than healthy old during SmallFast. UE coordination correlated with number of FO-UE episodes in two conditions and FOG-Q score in one. No differences existed between PD-/+FOG in coordination or number of FO-UE episodes. Conclusions. Dyscoordination and FO-UE can be elicited by manipulating cadence and amplitude of an alternating bimanual task. It remains unclear whether FO-UE and FOG share common mechanisms.

The neural correlates of upper limb motor blocks in Parkinson's disease and their relation to freezing of gait

Due to basal ganglia dysfunction, bimanual motor performance in Parkinson patients reportedly relies on compensatory brain activation in premotor-parietal-cerebellar circuitries. A subgroup of Parkinson's disease (PD) patients with freezing of gait (FOG) may exhibit greater bimanual impairments up to the point that motor blocks occur. This study investigated the neural mechanisms of upper limb motor blocks and explored their relation with FOG. Brain activation was measured using functional magnetic resonance imaging during bilateral finger movements in 16 PD with FOG, 16 without FOG (PD + FOG and PD - FOG), and 16 controls. During successful movement, PD + FOG showed decreased activation in right dorsolateral prefrontal cortex (PFC), left dorsal premotor cortex (PMd), as well as left M1 and bilaterally increased activation in dorsal putamen, pallidum, as well as subthalamic nucleus compared with PD - FOG and controls. On the contrary, upper limb motor blocks were associated with increased activation in right M1, PMd, supplementary motor area, and left PFC compared with successful movement, whereas bilateral pallidum and putamen activity was decreased. Complex striatofrontal activation changes may be involved in the difficulties of PD + FOG to perform bimanual movements, or sequential movements in general. These novel results suggest that, whatever the exact underlying cause, PD + FOG seem to have reached a saturation point of normal neural compensation and respond belatedly to actual movement breakdown.

Gait coordination in Parkinson disease: effects of step length and cadence manipulations

BACKGROUND

Gait impairments are well documented in those with PD. Prior studies suggest that gait impairments may be worse and ongoing in those with PD who demonstrate FOG compared to those with PD who do not.

PURPOSE

Our aim was to determine the effects of manipulating step length and cadence individually, and together, on gait coordination in those with PD who experience FOG, those with PD who do not experience FOG, healthy older adults, and healthy young adults.

METHODS

Eleven participants with PD and FOG, 16 with PD and no FOG, 18 healthy older, and 19 healthy young adults walked across a GAITRite walkway under four conditions: Natural, Fast (+50% of preferred cadence), Small (-50% of preferred step length), and SmallFast (+50% cadence and -50% step length). Coordination (i.e. phase coordination index) was measured for each participant during each condition and analyzed using mixed model repeated measure ANOVAs.

RESULTS

FOG was not elicited. Decreasing step length alone or decreasing step length and increasing cadence together affected coordination. Small steps combined with fast cadence resulted in poorer coordination in both groups with PD compared to healthy young adults and in those with PD and FOG compared to healthy older adults.

CONCLUSIONS

Coordination deficits can be identified in those with PD by having them walk with small steps combined with fast cadence. Short steps produced at high rate elicit worse coordination than short steps or fast steps alone.

Asymmetry and freezing of gait in parkinsonian patients

It has been hypothesized that freezing of gait (FOG) in parkinsonian patients (PD) might be triggered by a breakdown in the normal symmetry of gait. In this study, we evaluated the relationship between asymmetry of gait and FOG and the effects of intensive treadmill treatment on asymmetry. We studied 30 patients with (FOG+) and 30 without (FOG-) freezing in "on" stage. Patients underwent a 4-week rehabilitation treatment using a treadmill with auditory and visual cues and were evaluated at enrollment and at the end of rehabilitation. Outcome measures were gait speed, stride length, asymmetry of gait, Six-minute walking test (6MWT), Unified Parkinson's Disease Rating Scale (UPDRS) II-III, Berg Balance Scale, Timed Up and Go Test, comfortable-fast gait speeds, freezing of gait questionnaire (FOGQ). At enrollment, no differences in gait parameters were observed between the two groups, which differed only in UPDRS_II and BBS. Both FOG+ and FOG- patients spent more time on the left foot (time on left/time on right foot 1.37, p = 0.002, 1.18, p = 0.016, respectively). Rehabilitation determined a homogeneous improvement in both groups of patients for all variables except UPDRS_II and balance, for which a better improvement was observed in FOG+ patients. The improvement in FOGQ in FOG+ patients was significantly correlated to the improvement in asymmetry of gait (Spearman R = 0.46, p = 0.013). Our data support a direct involvement of the asymmetry of gait in the development of FOG in PD. Treadmill training is effective in improving gait and balance in PD FOG+ patients and this might be related to a reduction of asymmetric gait.