Elizabeth L. Stegemöller

Spatiotemporal variability during gait initiation in Parkinson's disease

During gait initiation (GI), consistency of foot placement while stepping is important in making successful transitions from a state of stable static posture to an unstable state of dynamic locomotion. In populations characterized by gait dysfunction and postural instability, such as persons with Parkinsons disease (PD), the ability to generate a consistent stepping pattern during GI may be essential in the prevention of falls. However, little is known about GI variability in persons with PD as compared to their healthy elderly peers. Therefore, this study investigated spatiotemporal variability during the first two steps of GI in 46 persons with idiopathic PD and 49 healthy age-matched adults. Stepping characteristics, including the length, width, and time of the first two steps of GI as well as their coefficients of variation (CV) were compared between groups. Persons with PD initiated gait with significantly shorter steps (swing step length=.463 vs. .537 m, stance step length=.970 vs. 1.10 m) and higher variability in step length (swing step CV=8.82 vs. 5.45, stance step CV=6.76 vs. 3.61). Persons with PD also showed significantly higher variability in the time of the swing step (swing step CV=10.0 vs. 7.4). GI variability did not differ significantly between disease stages in persons with PD. Because greater variability in these measures during gait is related to an increased risk of falls, we propose that higher GI variability may play a considerable role in falls frequently observed during transitions from quiet standing in PD.

Using the Timed Up & Go Test in a Clinical Setting to Predict Falling in Parkinson's Disease

OBJECTIVE To investigate the ability of the Timed Up & Go test to identify patients with Parkinsons disease at risk for a fall. DESIGN Cross-sectional cohort study. SETTING Sixteen participating National Parkinsons Foundation Centers of Excellence. PARTICIPANTS A query yielded a total of 2985 records (1828 men and 1157 women). From these, 884 were excluded because of a lack of crucial information (age, diagnosis, presence of deep brain stimulation, disease duration, inability of performing the Timed Up & Go test without assistance) at the time of testing, leaving 2097 patients included in the analysis. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES The primary outcome measure for this study was falls. The chief independent variable was the Timed Up & Go test. RESULTS The initial model examined the prediction of falls from the Timed Up & Go test, adjusting for all study covariates. The estimated models in the imputed data sets represented a significant improvement above chance (χ(2) range [df=17], 531.29-542.39, P<.001), suggesting that 74% of participants were accurately classified as a faller or nonfaller. The secondary model in which the question of whether the effect of Timed Up & Go test was invariant across disease severity demonstrated 75% of participants were accurately classified as a faller or nonfaller. Additional analysis revealed a proposed cut score of 11.5 seconds for discrimination of those who did or did not fall. CONCLUSIONS The findings suggest that the Timed Up & Go test may be an accurate assessment tool to identify those at risk for falls.

Postural instability and gait impairment during obstacle crossing in Parkinson's disease.

OBJECTIVE To examine whether Parkinsons disease (PD) affects gait behavior and stability while walking over an obstacle. DESIGN Parallel group comparisons were completed in which participants completed 5 trials of normal walking and 5 trials of obstacle crossing while gait kinematics and kinetics were collected. SETTING University biomechanics laboratory. PARTICIPANTS Individuals with PD (n=10) and age- and sex-matched healthy older adults (n=10). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Gait parameters, obstacle clearance parameters, and center of mass motion were calculated during normal walking and obstacle crossing. RESULTS Results revealed that decrements in gait performance in individuals with PD were amplified during obstacle crossing, suggesting that due to disease-related degradation, individuals with PD chose a more conservative strategy for obstacle crossing. Moreover, an increased duration of single limb support (18% increase), a decrease in anteroposterior range of motion (20% decrease), and an increase in mediolateral range of motion (36% increase, though not significant) coupled with the reduction in the distance between the center of pressure and center of mass (mean of 21% decrease across toe-off and heel strike) and increase in margin of stability (31% increase at toe-off and 71% increase at heel strike) may suggest that deficits in muscle strength and balance may contribute to this impairment. CONCLUSIONS Persons with PD alter their behavior to reduce the mechanical demands and increase dynamic stability during obstacle avoidance tasks.

Quantitative Normative Gait Data in a Large Cohort of Ambulatory Persons with Parkinson's Disease

Background Gait performance is widely evaluated to assess health status in older adult populations. While several investigators have presented normative values for spatiotemporal gait parameters drawn from older adult populations, the literature has been void of large-scale cohort studies, which are needed in order to provide quantitative, normative gait data in persons with Parkinson’s disease. The aim of this investigation was to provide reference values for clinically important gait characteristics in a large sample of ambulatory persons with Parkinson’s disease to aid both clinicians and researchers in their evaluations and treatments of gait impairment. Methodology/Principal Findings Gait performance was collected in 310 individuals with idiopathic Parkinson’s disease as they walked across a pressure sensitive walkway. Fourteen quantitative gait parameters were measured and evaluated with respect to Hoehn and Yahr disease staging and gender. Disease duration and age were controlled for in all analyses. Individuals with the greatest Parkinson’s disability walked significantly slower with shorter steps and stride lengths than the mild and moderately affected groups. Further, the most affected patients spent more time with both feet on the ground, and walked with a wider base of support than the moderately disabled patients. No differences were detected between the mild and moderate disability groups on any of the gait parameters evaluated. Conclusions/Significance Reference values for 14 gait parameters in a large cohort of ambulatory patients with Parkinson’s disease are provided and these may be highly useful for assessing and interpreting an individual’s gait dysfunction. It is important for clinicians and researchers to appreciate the lack of change in quantitative parameters as PD patients move from mild to moderate gait impairment.

Locomotor adaptation and locomotor adaptive learning in Parkinson's disease and normal aging.

OBJECTIVE Locomotor adaptation enables safe, efficient navigation among changing environments. We investigated how healthy young (HYA) and older (HOA) adults and persons with Parkinsons disease (PD) adapt to walking on a split-belt treadmill, retain adapted gait parameters during re-adaptation, and store aftereffects to conventional treadmill walking. METHODS Thirteen PD, fifteen HYA, and fifteen HOA walked on a split-belt treadmill for ten minutes with one leg twice as fast as the other. Participants later re-adapted to the same conditions to assess retention of the split-belt gait pattern. After re-adaptation, we assessed aftereffects of this pattern during conventional treadmill walking. RESULTS Persons with PD exhibited step length asymmetry throughout many adaptation and adaptive learning conditions. Early adaptation was similar across groups, though HYA and HOA continued to adapt into late adaptation while PD did not. Despite pervasive step length asymmetry among conditions which were symmetric in HYA and HOA, persons with PD demonstrated significant step length aftereffects during conventional treadmill walking after split-belt walking. CONCLUSIONS Though they may exhibit a default asymmetry under various walking conditions, persons with PD can adapt and store new walking patterns. SIGNIFICANCE Locomotor adaptation therapy may be effective in ameliorating asymmetric gait deficits in persons with PD.

Defining the clinically meaningful difference in gait speed in persons with Parkinson disease.

Background and Purpose: Gait dysfunction is a common target for pharmacological, behavioral, and surgical interventions in persons with Parkinson disease. However, the responsiveness of gait speed, that is, clinically important difference, is not well described in the literature for this population. The purpose of this study was to determine the magnitude of meaningful difference in gait speed using multiple methods of assessment and utilizing a large sample of participants inclusive of various stages of disease severity. Methods: Gait speed was measured using an instrumented walkway in 324 ambulatory persons with idiopathic Parkinson disease. Cross-sectional analysis of the clinically important difference for gait speed was performed using distribution- and anchor-based approaches: disability (Schwab and England Activities of Daily Living Scale), disease stage (Modified Hoehn and Yahr Scale), and severity (Unified Parkinsons Disease Rating Scale). Results: Using distribution-based analyses and effect size metrics, the small important difference in gait speed was 0.06 m/s, moderate was 0.14 m/s, and large was 0.22 m/s. Applying previously established cut-points for small, moderate, and large change in the motor scale score, the associated changes in gait speed that might be expected are 0.02, 0.06, and 0.10 m/s. Discussion and Conclusions: Our data revealed that the clinically important difference in gait speed among persons with Parkinson disease on medication ranged from 0.05 m/s to 0.22 m/s by distribution-based analysis and ranged from 0.02 m/s to 0.18 m/s per level within the anchor-based metrics. These data will aid in evaluating the effectiveness of interventions to improve gait speed in persons with Parkinson disease. Video Abstract available. See video (Supplemental Digital Content 1, http://links.lww.com/JNPT/A77) for more insights from the authors.

Associations Between Cognitive and Gait Performance During Single- and Dual-Task Walking in People With Parkinson Disease

Background Cognitive impairments in Parkinson disease (PD) manifest as deficits in speed of processing, working memory, and executive function and attention abilities. The gait impairment in PD is well documented to include reduced speed, shortened step lengths, and increased step-to-step variability. However, there is a paucity of research examining the relationship between overground walking and cognitive performance in people with PD. Objective This study sought to examine the relationship between both the mean and variability of gait spatiotemporal parameters and cognitive performance across a broad range of cognitive domains. Design A cross-sectional design was used. Methods Thirty-five participants with no dementia and diagnosed with idiopathic PD completed a battery of 12 cognitive tests that yielded 3 orthogonal factors: processing speed, working memory, and executive function and attention. Participants completed 10 trials of overground walking (single-task walking) and 5 trials of overground walking while counting backward by 3s (dual-task walking). Results All gait measures were impaired by the dual task. Cognitive processing speed correlated with stride length and walking speed. Executive function correlated with step width variability. There were no significant associations with working memory. Regression models relating speed of processing to gait spatiotemporal variables revealed that including dual-task costs in the model significantly improved the fit of the model. Limitations Participants with PD were tested only in the on-medication state. Conclusions Different characteristics of gait are related to distinct types of cognitive processing, which may be differentially affected by dual-task walking due to the pathology of PD.

Interlimb coordination is impaired during walking in persons with Parkinson’s disease

BACKGROUND Coordination between the upper and lower extremities is important to providing dynamic stability during human gait. Though limited, previous research has suggested that interlimb coordination may be impaired in persons with Parkinsons disease. We extend this previous work using continuous analytical techniques to enhance our understanding of interlimb coordination during gait in persons with Parkinsons disease. METHODS Eighteen adults with Parkinsons disease and fifteen healthy older adults walked overground while undergoing three-dimensional motion capture. Ipsilateral and contralateral interlimb coordination between the sagittal shoulder and hip angles was assessed using cross-covariance techniques. Independent samples and paired samples t-tests compared measures of interlimb coordination between groups and between sides within the participants with Parkinsons disease, respectively. Pearsons correlations were applied to investigate associations between interlimb coordination measures and subscores of gait, posture, and bradykinesia on the Unified Parkinsons Disease Rating Scale. FINDINGS Ipsilateral and contralateral interlimb coordination was reduced in persons with Parkinsons disease compared to the healthy older adults. Ipsilateral coordination between the upper and lower extremities more affected by disease was found to be negatively associated with clinical scores of gait and posture. Interlimb coordination was not significantly associated with clinical measures of bradykinesia. INTERPRETATION Persons with Parkinsons disease exhibit reduced interlimb coordination during gait when compared to healthy older adults. These reductions in coordination are related to clinically-meaningful worsening of gait and posture in persons with PD and coordination of arm and leg movements should be considered in future research on gait therapy in this population.

Timed Up and Go, Cognitive, and Quality-of-Life Correlates in Parkinson's Disease

OBJECTIVE To examine the relationship between Timed Up and Go (TUG) performance, verbal executive function (EF) performance, and quality-of-life (QOL) measures in Parkinsons disease (PD). DESIGN Cross-sectional. SETTING Sixteen movement disorder centers from across the United States. PARTICIPANTS Patients with PD (N=1964). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES TUG test, immediate and delayed 5-word recall, verbal fluency, PD QOL Questionnaire. RESULTS TUG performance and verbal EF performance were significantly associated with, and predictors of, QOL measures, having the greatest association and predictability with the mobility domain of the QOL measures. CONCLUSIONS The TUG test and verbal EF tests have QOL correlates, making the combined evaluation of mobility, cognitive, and QOL decline a potential examination tool to evaluate the sequelae of PD.

Selective use of low frequency stimulation in Parkinson's disease based on absence of tremor.

BACKGROUND High frequency stimulation (HFS) of the subthalamic nucleus is one of the most effective treatments for advanced Parkinsons disease (PD). HFS has provided beneficial improvements in the cardinal features of PD, but has not been proven as effective for addressing the axial predominant levodopa resistant symptoms, such as speech disturbances, gait disturbances, and postural instability. Recent studies have suggested that changes in stimulation parameters may influence differing PD symptoms. OBJECTIVE The purpose of this study was to compare the effects of low frequency stimulation (LFS) versus HFS on the Unified Parkinsons Disease Rating Scale (UPDRS), gait, balance, and verbal fluency. METHODS Eight tremor dominant and nine non-tremor dominant participants with bilateral deep brain stimulation of the subthalamic nucleus were tested off stimulation, during LFS, and during HFS. RESULTS Results revealed that HFS significantly reduced UPDRS tremor score in the tremor dominant group; however no differences emerged within the non-tremor dominant group. No differences between groups or stimulation conditions were found for gait, balance, and verbal fluency measures. CONCLUSION These results may suggest that HFS is better than LFS for reducing tremor in tremor dominant patients. However, patients with mild or no tremor show no acute differences in benefit from LFS as compared to HFS.