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Objective: To fulfill the potential of nonpharmacological interventions for people with Parkinson disease (PD), individually tailored treatment is needed. Multimodal balance training supported by rhythmic auditory stimuli (RAS) can improve balance and gait in people with PD. The purpose of this study was to determine whether both freezers and nonfreezers benefit., Methods: A secondary analysis was conducted on a large randomized controlled trial that included 154 patients with PD (Hoehn & Yahr Stages 1-3 while ON-medication) who were assigned randomly to 3 groups: (1) multimodal balance training with RAS delivered by a metronome (RAS-supported multimodal balance training); (2) regular multimodal balance training without rhythmic auditory cues; and (3) a control intervention (involving an educational program). Training was performed for 5 weeks, twice per week. The primary outcome was the Mini-BESTest score directly after the training period. Assessments were performed by a single, masked assessor at baseline, directly postintervention, and after 1-month and 6-month follow-up. Outcomes were analyzed in 1 analysis, and the results were presented separately for freezers and nonfreezers with a linear mixed model, adjusted for baseline Mini-BESTest scores, Unified Parkinson's Disease Rating Scale scores, and levodopa equivalent dose., Results: In both freezers and nonfreezers, both RAS-supported multimodal training and regular training significantly improved the Mini-BESTest scores compared with baseline scores and with the control group scores. The improvement was larger for RAS-supported training compared with regular training, for both freezers and nonfreezers. Only the RAS-supported training group retained the improvements compared with baseline measurements at 6-month follow-up, and this was true for both freezers and nonfreezers., Conclusions: RAS-supported multimodal training is effective in improving balance performance in both freezers and nonfreezers., Impact: Until this study, it was unknown whether both freezers and nonfreezers could benefit from multimodal balance training. With this information, clinicians who work with people with PD will be better able to apply personalized gait rehabilitation., Lay Summary: Adding rhythmic auditory stimuli (RAS) to balance training is beneficial for both freezers and nonfreezers, at least in persons with mild to moderate disease stages. This RAS-supported multimodal training has good potential for a wider clinical implementation with good long-term effects., (© The Author(s) 2020. Published by Oxford University Press on behalf of the American Physical Therapy Association.)

Background . People with Parkinson's disease and freezing of gait (FOG+) have more falls, postural instability and cognitive impairment compared with FOG-. Objective . To conduct a secondary analysis of the V-TIME study, a randomized, controlled investigation showing a greater reduction of falls after virtual reality treadmill training (TT + VR) compared with usual treadmill walking (TT) in a mixed population of fallers. We addressed whether these treadmill interventions led to similar gains in FOG+ as in FOG-. Methods . A total of 77 FOG+ and 44 FOG- were assigned randomly to TT + VR or TT. Participants were assessed pre- and posttraining and at 6 months' follow-up. Main outcome was postural stability assessed by the Mini Balance Evaluation System Test (Mini-BEST) test. Falls were documented using diaries. Other outcomes included the New Freezing of Gait Questionnaire (NFOG-Q) and the Trail Making Test (TMT-B). Results . Mini-BEST scores and the TMT-B improved in both groups after training ( P = .001), irrespective of study arm and FOG subgroup. However, gains were not retained at 6 months. Both FOG+ and FOG- had a greater reduction of falls after TT + VR compared with TT ( P = .008). NFOG-Q scores did not change after both training modes in the FOG+ group. Conclusions . Treadmill walking (with or without VR) improved postural instability in both FOG+ and FOG-, while controlling for disease severity differences. As found previously, TT + VR reduced falls more than TT alone, even among those with FOG. Interestingly, FOG itself was not helped by training, suggesting that although postural instability, falls and FOG are related, they may be controlled by different mechanisms.

Background: Balance impairment in Parkinson's disease (PD) improves only partially with dopaminergic medication. Therefore, non-pharmacological interventions such as physiotherapy are important elements in clinical management. External cues are often applied to improve gait, but their effects on balance control are unclear., Objective/methods: We performed a prospective, single-blind, randomized clinical trial to study the effectiveness of balance training with and without rhythmical auditory cues. We screened 201 volunteers by telephone; 154 were assigned randomly into three groups: (1) multimodal balance training supported by rhythmical auditory stimuli (n = 56) (RAS-supported multimodal balance training); (2) regular multimodal balance training without rhythmical auditory stimuli (n = 50); and (3) control intervention involving a general education program (n = 48). Training was performed for 5 weeks, two times/week. Linear mixed models were used for all outcomes. Primary outcome was the Mini-BESTest (MBEST) score immediately after the training period. Assessments were performed by a single, blinded assessor at baseline, immediately post intervention, and after one and 6-months follow-up., Results: Immediately post intervention, RAS-supported multimodal balance training was more effective than regular multimodal balance training on MBEST (difference 3.5 (95% Confidence Interval (CI) 2.2; 4.8)), p < 0.001). Patients allocated to both active interventions improved compared to controls (MBEST estimated mean difference versus controls 6.6 (CI 5.2; 8.0), p < 0.001 for RAS-supported multimodal balance training; and 3.0 (CI 2.7; 5.3), p < 0.001 for regular multimodal balance training). Improvements were retained at one-month follow-up for both active interventions, but only the RAS-supported multimodal balance training group maintained its improvement at 6 months., Conclusion: Both RAS-supported multimodal balance training and regular multimodal balance training improve balance, but RAS-supported multimodal balance training-adding rhythmical auditory cues to regular multimodal balance training-has greater and more sustained effects.

Introduction: Falling is among the most serious clinical problems in Parkinson's disease (PD). We used body-worn sensors (falls detector worn as a necklace) to quantify the hazard ratio of falls in PD patients in real life., Methods: We matched all 2063 elderly individuals with self-reported PD to 2063 elderly individuals without PD based on age, gender, comorbidity, and living conditions. We analyzed fall events collected at home via a wearable sensor. Fall events were collected either automatically using the wearable falls detector or were registered by a button push on the same device. We extracted fall events from a 2.5-year window, with an average follow-up of 1.1 years. All falls included were confirmed immediately by a subsequent telephone call. The outcomes evaluated were (1) incidence rate of any fall, (2) incidence rate of a new fall after enrollment (ie, hazard ratio), and (3) 1-year cumulative incidence of falling., Results: The incidence rate of any fall was higher among self-reported PD patients than controls (2.1 vs. 0.7 falls/person, respectively; P < .0001). The incidence rate of a new fall after enrollment (ie, hazard ratio) was 1.8 times higher for self-reported PD patients than controls (95% confidence interval, 1.6-2.0)., Conclusion: Having PD nearly doubles the incidence of falling in real life. These findings highlight PD as a prime "falling disease." The results also point to the feasibility of using body-worn sensors to monitor falls in daily life. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society., (© 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.)

Gait festination is one of the most characteristic gait disturbances in patients with Parkinson's disease or atypical parkinsonism. Although festination is common and disabling, it has received little attention in the literature, and different definitions exist. Here, we argue that there are actually two phenotypes of festination. The first phenotype entails a primary locomotion disturbance, due to the so-called sequence effect: a progressive shortening of step length, accompanied by a compensatory increase in cadence. This phenotype strongly relates to freezing of gait with alternating trembling of the leg. The second phenotype results from a postural control problem (forward leaning of the trunk) combined with a balance control deficit (inappropriately small balance-correcting steps). In this viewpoint, we elaborate on the possible pathophysiological substrate of these two phenotypes of festination and discuss their management in daily clinical practice.

Objective: Differentiating Parkinson's disease (PD) from atypical parkinsonian disorders (APD) such as Multiple System Atrophy, parkinsonian type (MSA-p) or Progressive Supranuclear Palsy (PSP-RS) can be challenging. Early signs of postural Instability and gait disability (PIGD) are considered clues that may signal presence of APD. However, it remains unknown which PIGD test - or combination of tests - can best distinguish PD from APD. We evaluated the discriminative value of several widely-used PIGD tests, and aimed to develop a short PIGD evaluation that can discriminate parkinsonian disorders., Methods: In this multicentre cohort study patients were recruited by 11 European MSA Study sites. Patients were diagnosed using standardized criteria. Postural instability and gait disability was evaluated using interviews and several clinical tests., Results: Nineteen PD, 21 MSA-p and 25 PSP-RS patients were recruited. PIGD was more common in APD compared to PD. There was no significant difference in axial symptoms between PSP-RS and MSA-p, except for self-reported falls (more frequent in PSP-RS patients). The test with the greatest discriminative power to distinguish APD from PD was the ability to perform tandem gait (AUC 0.83; 95% CI 71-94; p < 0.001), followed by the retropulsion test (AUC 0.8; 95% CI 0.69-0.91; p < 0.001) and timed-up-and-go test (TUG) (AUC 0.77; 95% CI 0.64-0.9; p = 0.001). The combination of these three tests yielded highest diagnostic accuracy (AUC 0.96; 95% CI 0.92-1.0; p < 0.001)., Conclusions: Our study suggests that simple "bedside" PIGD tests - particularly the combination of tandem gait performance, TUG and retropulsion test - can discriminate APD from PD., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Neurological disorders of gait, balance and posture are both debilitating and common. Adequate recognition of these so-called disorders of axial mobility is important as they can offer useful clues to the underlying pathology in patients with an uncertain clinical diagnosis, such as those early in the course of neurological disorders. Medical teaching programmes typically take classic clinical presentations as the starting point and present students with a representative constellation of features that jointly characterize a particular axial motor syndrome. However, patients rarely present in this way to a physician in clinical practice. Particularly in the early stages of a disease, patients might display just one (or at best only a few) abnormal signs of gait, balance or posture. Importantly, these individual signs are never pathognomonic for any specific disorder but rather come with an associated differential diagnosis. In this Perspective, we offer a new diagnostic approach in which the presenting signs are taken as the starting point for a focused differential diagnosis and a tailored search into the underlying neurological syndrome.

Background: Postural instability and freezing of gait (FOG) are major problems in patients with Parkinson's disease (PD), and both contribute to falls. However, the interrelationship between these 2 deficits is still unclear., Objective: This study investigated whether dual-tasking influenced postural control differently in freezers (FOG+) and nonfreezers (FOG-)., Methods: Thirty-three patients with PD (19 FOG+, 14 FOG-, well-matched) and 28 healthy controls underwent 4 postural control tasks, consisting of standing on either stable or unstable surfaces with eyes open or closed. Each condition was performed with and without a cognitive dual-task (DT). Center of pressure and center of mass variables and cognitive DT performance outcomes were investigated., Results: Postural stability decreased to a larger extent in FOG+ under DT conditions compared with the other groups, although overall most differences were found between FOG+ and controls. FOG+ exhibited worse postural control compared with FOG- under stable surface DT conditions, shown by higher medial-lateral sway measures (group × surface × task, P < .05). Also, postural DT cost (%) was higher in FOG+ than in FOG- in unstable surface conditions without vision. Controls performed better on the cognitive DT when balancing compared with sitting, whereas this improvement was absent in both PD subgroups and more so in FOG+., Conclusions: Postural stability in FOG+ deteriorated more than in FOG- and controls upon cognitive load. Our results extend earlier findings on gait that the compensatory mechanisms to cope with DT stance are insufficient in FOG+. The findings highlight the need for adapted rehabilitation programs for this subgroup, comprising motor-cognitive balance training.

The evidence for physiotherapy is growing, showing a positive impact on functional activities involving gait, transfers and balance. Specific recommendations for physiotherapists, physicians and people with Parkinson's disease were published in the European Physiotherapy Guideline for Parkinson's disease. Here, we summarize the referral criteria, highlight the importance of accurate referral to specialized physiotherapists, and emphasize the potential benefits of expert care. As such, this paper offers very practical guidance for clinicians working with Parkinson's disease patients and who consider physiotherapy treatments for their patients.

Background: Disorders of posture, gait, and balance in Parkinson's disease (PD) are common and debilitating. This MDS-commissioned task force assessed clinimetric properties of existing rating scales, questionnaires, and timed tests that assess these features in PD., Methods: A literature review was conducted. Identified instruments were evaluated systematically and classified as "recommended," "suggested," or "listed." Inclusion of rating scales was restricted to those that could be used readily in clinical research and practice., Results: One rating scale was classified as "recommended" (UPDRS-derived Postural Instability and Gait Difficulty score) and 2 as "suggested" (Tinetti Balance Scale, Rating Scale for Gait Evaluation). Three scales requiring equipment (Berg Balance Scale, Mini-BESTest, Dynamic Gait Index) also fulfilled criteria for "recommended" and 2 for "suggested" (FOG score, Gait and Balance Scale). Four questionnaires were "recommended" (Freezing of Gait Questionnaire, Activities-specific Balance Confidence Scale, Falls Efficacy Scale, Survey of Activities, and Fear of Falling in the Elderly-Modified). Four tests were classified as "recommended" (6-minute and 10-m walk tests, Timed Up-and-Go, Functional Reach)., Conclusion: We identified several questionnaires that adequately assess freezing of gait and balance confidence in PD and a number of useful clinical tests. However, most clinical rating scales for gait, balance, and posture perform suboptimally or have been evaluated insufficiently. No instrument comprehensively and separately evaluates all relevant PD-specific gait characteristics with good clinimetric properties, and none provides separate balance and gait scores with adequate content validity for PD. We therefore recommend the development of such a PD-specific, easily administered, comprehensive gait and balance scale that separately assesses all relevant constructs. © 2016 International Parkinson and Movement Disorder Society., (© 2016 International Parkinson and Movement Disorder Society.)

Introduction: The pathophysiology underlying postural instability in Parkinson's disease is poorly understood. The frequent co-existence with freezing of gait raises the possibility of shared pathophysiology. There is evidence that dysfunction of brainstem structures contribute to freezing of gait. Here, we evaluated whether dysfunction of these structures contributes to postural instability as well. Brainstem function was assessed by studying the StartReact effect (acceleration of latencies by a startling acoustic stimulus (SAS))., Methods: We included 25 patients, divided in two different ways: 1) those with postural instability (HY = 3, n = 11) versus those without (HY<3, n = 14); and 2) those with freezing (n = 11) versus those without freezing (n = 14). We also tested 15 matched healthy controls. We tested postural responses by translating a balance platform in the forward direction, resulting in backward balance perturbations. In 25% of trials, the start of the balance perturbation was accompanied by a SAS., Results: The amplitude of automatic postural responses and length of the first balance correcting step were smaller in patients with postural instability compared to patients without postural instability, but did not differ between freezers and non-freezers. In contrast, the StartReact effect was intact in patients with postural instability but was attenuated in freezers., Discussion: We suggest that the mechanisms underlying freezing of gait and postural instability in Parkinson's disease are at least partly different. Underscaling of automatic postural responses and balance-correcting steps both contribute to postural instability. The attenuated StartReact effect was seen only in freezers and likely reflects inadequate representation of motor programs at upper brainstem level.

Postural instability is a disabling feature of Parkinson's disease (PD), contributing to recurrent falls and fall-related injuries. The retropulsion test is widely regarded as the gold standard to evaluate postural instability, and is therefore a key component of the neurological examination in PD. Many variants exist, which confuses both clinical practice and research. Here, we evaluate the merits of this test by discussing three common variants: (1) the pull test as described in the MDS-UPDRS scale; (2) using an unexpected shoulder pull, without prior warning; and (3) the push-and-release test. All variants are a quick method to index the degree of postural instability, but the outcome can vary considerably due to variability in test execution and -interpretation. This partially explains why the retropulsion test fails to predict future falls in PD. Another explanation is that falling results from the complex interplay between gait, balance, cognitive decline and environmental factors, and the retropulsion test captures only part of that. We conclude with several recommendations for current clinical practice.

In this study, we investigated the effect of dopaminergic medication on reactive stepping responses to forward and backward balance perturbations in patients with moderately severe Parkinson's disease (PD). Twelve PD patients, Hoehn and Yahr stage ranging from 2 to 3, and 15 healthy controls were exposed to multidirectional translational stance perturbations on a moveable platform. Perturbations were unpredictable in terms of amplitude, timing and direction. Patients were tested in the medication ON and OFF (at least 12 h of dopaminergic medication withdrawal) state on two separate days. Forward and backward stepping responses were quantified in terms of (1) presence, onset and amplitude of anticipatory postural adjustments (APAs); (2) spatiotemporal step variables (step onset, length and velocity); and (3) leg inclination angle at first stepping-foot contact. When perturbed forward, patients performed worse than controls in terms of step length (0.32 ± 0.07 vs. 0.38 ± 0.05 m, p = 0.01) and step velocity (1.21 ± 0.16 vs. 1.37 ± 0.13 m/s, p = 0.01), while step onset was not different. The number of steps with an APA was larger in patients in the OFF state than in controls which was, however, only significant after forward perturbations (43 vs. 20%, p = 0.01). Following backward perturbations, leg angles at foot contact were smaller in patients compared to controls (-2.71° ± 4.29° vs. 0.26° ± 2.80°, p = 0.04) reflecting a poorer mechanical efficiency of the step. Dopaminergic medication had no significant effect on any of these outcomes. In conclusion, dopaminergic medication does not improve underscaling of stepping responses in PD. Therefore, other interventions are needed to improve these important defense postural reactions.

Balance control (the ability to maintain an upright posture) is asymmetrically controlled in a proportion of patients with Parkinson's disease. Gait asymmetries have been linked to the pathophysiology of freezing of gait. We speculate that asymmetries in balance could contribute to freezing by a) hampering the unloading of the stepping leg and/or b) leading to a preferred stance leg during gait, which then results in asymmetric gait. To investigate this, we examined the relationship between balance control and weight-bearing asymmetries and freezing. We included 20 human patients with Parkinson (tested OFF medication; nine freezers) and nine healthy controls. Balance was perturbed in the sagittal plane, using continuous multi-sine perturbations, applied by a motion platform and by a force at the sacrum. Applying closed-loop system identification techniques, relating the body sway angle to the joint torques of each leg separately, determined the relative contribution of each ankle and hip joint to the total amount of joint torque. We also calculated weight-bearing asymmetries. We determined the 99-percent confidence interval of weight-bearing and balance-control asymmetry using the responses of the healthy controls. Freezers did not have larger asymmetries in weight bearing (p = 0.85) nor more asymmetrical balance control compared to non-freezers (p = 0.25). The healthy linear one-to-one relationship between weight bearing and balance control was significantly different for freezers and non-freezers (p = 0.01). Specifically, non-freezers had a significant relationship between weight bearing and balance control (p = 0.02), whereas this relation was not significant for freezers (p = 0.15). Balance control is asymmetrical in most patients (about 75 percent) with Parkinson's disease, but this asymmetry is not related to freezing. The relationship between weight bearing and balance control seems to be less pronounced in freezers, compared to healthy controls and non-freezers. However, this relationship should be investigated further in larger groups of patients.

Parkinson's disease (PD) impairs the ability to shape postural responses to contextual factors. It is unknown whether such inflexibility pertains to compensatory steps to overcome balance perturbations. Participants were instructed to recover balance in response to a platform translation. A step was necessary to recover balance when the translation was large, whereas a feet-in-place (FiP) response was sufficient when the translation was small (i.e. no step). We compared step trials that required a switch away from the current postural set (switch trials: step trials that were preceded by FiP trials) with non-switch trials (i.e. step trials were preceded by identical step trials). 51 PD patients (59 ± 7 years) were compared with 22 healthy controls (60 ± 6 years). In a second analysis, we compared a subgroup of 14 freezers (PD-FOG) with a subgroup of 14 non-freezers (PD-noFOG; matched for age, gender and disease severity). Compared to non-switch trials, switch trials resulted in poorer step execution and more steps needed to recover balance. These switching effects were similar in PD patients and controls, and in PD-FOG and PD-noFOG patients. Overall, PD patients demonstrated poorer stepping performance than controls. PD-FOG had a worse performance than PD-noFOG. Moreover, PD patients, and particularly PD-FOG patients, were less able to improve step performance with repetitive step trials, in contrast to controls. Thus, there was no PD-related deficit to switch to an alternative response strategy, neither in patients with FOG nor in patients without FOG. Difficulty to adapt the step trial-by-trial might have contributed to the absence of switch deficits in PD., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Underlying somatosensory processing deficits of joint rotation velocities may cause patients with Parkinson's disease (PD) to be more unstable for fast rather than slow balance perturbations. Such deficits could lead to reduced proprioceptive amplitude feedback triggered by perturbations, and thereby to smaller or delayed stabilizing postural responses. For this reason, we investigated whether support surface perturbation velocity affects balance reactions in PD patients. We examined postural responses of seven PD patients (OFF medication) and eight age-matched controls following backward rotations of a support-surface platform. Rotations occurred at three different speeds: fast (60 deg/s), medium (30 deg/s) or slow (3.8 deg/s), presented in random order. Each subject completed the protocol under eyes open and closed conditions. Full body kinematics, ankle torques and the number of near-falls were recorded. Patients were significantly more unstable than controls following fast perturbations (26% larger displacements of the body's centre of mass; P<0.01), but not following slow perturbations. Also, more near-falls occurred in patients for fast rotations. Balance correcting ankle torques were weaker for patients than controls on the most affected side, but were stronger than controls for the least affected side. These differences were present both with eyes open and eyes closed (P<0.01). Fast support surface rotations caused greater instability and discriminated Parkinson patients better from controls than slow rotations. Although ankle torques on the most affected side were weaker, patients partially compensated for this by generating larger than normal stabilizing torques about the ankle joint on the least affected side. Without this compensation, instability may have been greater.

In early disease stages, it can be difficult to differentiate clinically between Parkinson's disease and the various forms of atypical parkinsonism, like multiple system atrophy or progressive supranuclear palsy. Balance impairment in the medio-lateral plane (i.e. sideways) is often seen in patients with a form of atypical parkinsonism, but not in patients with Parkinson's disease. This is reflected by the distance between the feet during gait, which is typically normal (or even narrow) in Parkinson's disease, but widened in atypical parkinsonism. Estimating this stance width depends on subjective judgement, and is difficult to quantify in clinical practice. Here, we emphasize that this medio-lateral balance impairment can also be revealed using two simple tests: (1) inability to perform tandem gait (taking one or more side steps being abnormal); and (2) self-report by patients who have lost the ability to ride a bicycle. Both tests have a good diagnostic yield in differentiating between Parkinson's disease and atypical parkinsonism, even early in the course of the disease.

Postural instability, one of the cardinal symptoms of Parkinson's disease (PD), has devastating consequences for affected patients. Better strategies to prevent falls are needed, but this calls for an improved understanding of the complex mechanisms underlying postural instability. We must also improve our ability to timely identify patients at risk of falling. Dynamic posturography is a promising avenue to achieve these goals. The latest moveable platforms can deliver 'real-life' balance perturbations, permitting study of everyday fall circumstances. Dynamic posturography studies have shown that PD patients have fundamental problems in scaling their postural responses in accordance with the need of the actual balance task at hand. On-going studies evaluate the predictive ability of impaired posturography performance for daily life falls. We also review recent work aimed at exploring balance correcting steps in PD, and the presumed interaction between startle pathways and postural responses.

Therapeutic management of gait and balance impairment during aging and neurodegeneration has long been a neglected topic. This has changed considerably during recent years, for several reasons: (1) an increasing recognition that gait and balance deficits are among the most relevant determinants of an impaired quality of life and increased mortality for affected individuals; (2) the arrival of new technology, which has allowed for new insights into the anatomy and functional (dis)integrity of gait and balance circuits; and (3) based in part on these improved insights, the development of new, more specific treatment strategies in the field of pharmacotherapy, deep brain surgery, and physiotherapy. The initial experience with these emerging treatments is encouraging, although much work remains to be done. The objective of this narrative review is to discuss several promising developments in the field of gait and balance treatment. We also address several pitfalls that can potentially hinder a fast and efficient continuation of this vital progress. Important issues that should be considered in future research include a clear differentiation between gait and balance as two distinctive targets for treatment and recognition of compensatory mechanisms as a separate target for therapeutic intervention., (© 2013 Movement Disorder Society.)

Perturbation of whole-body stability often evokes rapid arm reactions. It has been suggested that the earliest arm activation is a generic (e.g. startle-like) response to which a later stabilizing (e.g. counterweight or reach-to-grasp) or impact-protection component can be appended. To examine whether the initial part of the reaction is generic, we examined arm reactions evoked by small balance perturbations in 12 healthy young adults while varying perturbation direction (rightward or forward platform translation) and environmental conditions (handrail present or absent). The perturbation magnitude was selected to be sufficiently small to obviate the need to use the arms for stabilization. To avoid adaptation or habituation, analysis focused on each subject's very first exposure to the perturbation. Most subjects exhibited active movement of both arms in reaction to the perturbation, but there was large (non-stereotypical) inter-subject variation in muscle-onset latency and arm kinematics. Furthermore, the velocity and direction of the initial arm movement were affected by perturbation direction, in a manner consistent with functional strategies (counterweight strategy in backward falls, hybrid counterweight/protective strategy in leftward falls). Although subjects never contacted the handrail, responses were slower when it was present. These results are not consistent with a generic stereotyped response, but suggest instead that even the earliest component of first-trial arm reactions was functionally modulated., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Postural instability and gait disorders (PIGD) in Parkinson's disease (PD) seem to be associated with executive dysfunction. We investigated which specific executive functions are associated with functional mobility in mildly affected PD patients. Functional mobility (Timed Up&Go Test, TUG), PIGD score, (spatial) working memory, set shifting, response inhibition and response generation were assessed in a large cohort of 232 non-demented PD patients. Both performance on the TUG and PIGD score were weakly associated with working memory and response generation (semantic and phonemic fluency). TUG also correlated with semantic fluency when corrected for disease severity and age. These results indicate that response generation and working memory are associated with (and possibly also causally related to) gait and balance deficits. In order to fully interpret gait and postural stability of PD patients in everyday situations, the role of impairments in working memory and response generation should be taken into account., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Gait, balance, and falls have become increasingly common topics of published articles in the Movement Disorders journal since its launch in 1986. This growth represents an increasing awareness of the importance of mobility to patients' quality of life. New methods have become available that allow for accurate measurement of many aspects for gait and balance. This has led to new concepts of understanding gait and balance disorders. Neuroimaging has begun to reveal the neural circuitry underlying gait and balance. The physiology and pathophysiology of balance and gait are beginning to tease out the many processes involved in mobility and how they may be disrupted by disease processes. With these advances, the old therapeutic nihilism that characterized the clinician's approach to falls and gait disorders is disappearing, as innovative physiotherapy, exercise, drugs, and deep brain stimulation are being employed for gait and balance disorders., (Copyright © 2011 Movement Disorder Society.)

Unexpected support-surface movements delivered during stance elicit "first trial" postural reactions, which are larger and cause greater instability compared with habituated responses. The nature of this first trial reaction remains unknown. We hypothesized that first trial postural reactions consist of a generalized startle reaction, with a similar muscle synergy as the acoustic startle response, combined with an automatic postural reaction. Therefore we compared acoustic startle responses to first trial postural reactions. Eight healthy subjects stood on a support surface that unexpectedly rotated backwards 10 times, followed by 10 startling acoustic stimuli, or vice versa. Outcome measures included full body kinematics and surface EMG from muscles involved in startle reactions or postural control. Postural perturbations and startling acoustic stimuli both elicited a clear first trial reaction, as reflected by larger kinematic and EMG responses. The ensuing habituation rate to repeated identical stimuli was comparable for neck and trunk muscles in both conditions. Onset latencies in neck muscles occurred significantly later for first trial perturbations compared with startle responses, but earlier in trunk muscles. Our results show that platform tilting initially induces reactions larger than needed to maintain equilibrium. For neck and trunk muscles, these first trial postural reactions resembled acoustic startle reflexes. First trial postural reactions may be triggered by interaction of afferent volleys formed by somatosensory and vestibular inputs. Acoustic startle reactions may also be partially triggered by vestibular inputs. Similar muscle activation driven by vestibular inputs may be the common element of first trial postural responses and acoustic startle reactions.

Support-surface movements are commonly used to examine balance control. Subjects typically receive a series of identical or randomly interspersed multidirectional balance perturbations and the atypical "first trial reaction" (evoked by the first perturbation) is often excluded from further analysis. However, this procedure may obscure vital information about neurophysiological mechanisms associated with the first perturbation and, by analogy, fully unexpected falls. We studied first trial reactions, aiming to clarify their directional impact on postural control and to characterize the underlying neurophysiological substrate. We instructed 36 subjects to maintain balance following support-surface rotations in six different directions. Perturbations in each direction were delivered in blocks, consisting of 10 serial stimuli. Full body kinematics, surface reactive forces, and electromyographic (EMG) responses were recorded. Regardless of direction, for the very first rotation, displacement of the center of mass was 15% larger compared with the ensuing nine identical rotations (P < 0.0001). This first trial reaction immediately reemerged whenever a new perturbation direction was introduced. First trial reactions (and near-falls) were greatest for backward-directed rotations and smallest for laterally directed rotations. This directional dependence coincided with early changes in vertical head accelerations. First trial reactions in EMG responses involved larger amplitudes in general and earlier muscle response onsets in upper body muscles. These findings show that first trial reactions are associated with significantly increased postural instability, mainly due to increased response amplitudes. Although rapid habituation occurs following presentation of identical stimuli, subjects immediately become unstable again when the perturbation direction suddenly changes. Excessive responses due to a failure to combine proprioceptive and vestibular cues effectively may explain this instability seen with first trials, particularly when falling backward.

Parkinson's disease (PD) is traditionally viewed as a mainly hypodopaminergic syndrome, with symptoms resulting predominantly from loss of dopamine-producing neurons in the substantia nigra. However, while most of the cardinal motor features of PD respond well to dopaminergic therapy, many other features of the disease do not. Balance impairment and the associated risk of falling represent one of the most prominent and potentially disabling features that are typically refractory to dopaminergic treatment. Therefore, it is possible that lesions in nondopaminergic systems contribute to the pathophysiology of postural instability in PD. Such nondopaminergic lesions are well recognized, certainly in advanced stages of PD where postural instability and falls dominate the clinical presentation. However, it remains unclear which of the identified nondopaminergic lesions is specifically responsible for postural instability and balance impairment. In this review, we argue that cell loss in the locus coeruleus and a resultant central norepinephrine deficit are intimately involved in the pathophysiology of postural instability in PD. If proven to be correct, this link between defective noradrenergic neurotransmission and postural instability could have important implications for the future development of new symptomatic treatments aimed to correct postural instability and preventing falls. Studies in the next 5 years could test this hypothesis, using a battery of complementary research techniques, including advanced neuroimaging (structural, functional imaging and nuclear), neurochemical studies of cerebrospinal fluid, post-mortem clinicopathological analyses and detailed clinical balance evaluations supplemented by posturography studies.

Background: Cognition influences gait and balance in elderly people. Executive functions seem to play a key role in this mechanism. Previous studies used only a single test to probe executive functions, and outcome measures were restricted to gait variables. We extend this prior work by examining the association between two different executive functions and measures of both gait and balance, with and without two different cognitive dual tasks., Methods: This is a cross-sectional study with randomly selected community-living elderly people. Executive functions were tested with the Trail Making Test Parts A and B and the Stroop Color Word Test; memory with Cambridge Neuropsychological Test Automated Battery (CANTAB) subtests. Patients walked without and with two dual tasks (subtracting serial sevens and animal naming). Main outcomes focused on gait (velocity, stride length, and stride time variability), measured on an electronic walkway, and balance, measured as trunk movements during walking. Associations were assessed with multiple regression models., Results: One hundred elderly people, with a mean age 80.6 years (range 75-93 years) participated. Both dual tasks decreased gait velocity and increased variability and trunk sway. Executive functions were associated with only stride length variability and mediolateral trunk sway during performance of animal naming as the dual task. Memory was not associated with the gait and balance variables., Conclusions: In community-living elderly people, executive functions are associated with gait and balance impairment during a challenging dual-task condition that also depends on executive integrity. Next steps will be to explore the value of executive functions in defining fall-risk profiles and in fall-prevention interventions for frail patients.

Postural instability and falls are common and devastating features of ageing and many neurological, visual, vestibular or orthopedic disorders. Current management of these problems is hampered by the subjective and variable nature of the available clinical balance measures. In this narrative review, we discuss the clinical utility of posturography as a more objective and quantitative measure of balance and postural instability, focusing on several areas where clinicians presently experience the greatest difficulties in managing their patients: (a) to make an appropriate differential diagnosis in patients presenting with falls or balance impairment; (b) to reliably identify those subjects who are at risk of falling; (c) to objectively and quantitatively document the outcome of therapeutic interventions; and (d) to gain a better pathophysiological understanding of postural instability and falls, as a basis for the development of improved treatment strategies to prevent falling. In each of these fields, posturography offers several theoretical advantages and, when applied correctly, provides a useful tool to gain a better understanding of pathophysiological mechanisms in patients with balance disorders, at the group level. However, based on the available evidence, none of the existing techniques is currently able to significantly influence the clinical decision making in individual patients. We critically review the shortcomings of posturography as it is presently used, and conclude with several recommendations for future research.

Muscle strength is a potentially important factor contributing to postural control. In this article, we consider the influence of muscle weakness on postural instability and falling. We searched the literature for research evaluating muscle weakness as a risk factor for falls in community-dwelling elderly individuals, for evidence that strength training reduces falls, and for pathophysiological evidence from patients with neuromuscular disease that supports the link between muscle weakness and falls. In virtually all studies that included strength testing, muscle weakness was a consistent risk factor for falls in the elderly. Studies that evaluated the merits of muscle strength training often showed a reduction in fall rates, particularly when strength training was a component of a multifactorial intervention, although it was unclear whether strength training alone led to a fall reduction. Surprisingly few studies addressed the pathophysiological relationship between muscle strength and balance control. We conclude that muscle weakness is an important risk factor for falls that is potentially amenable to therapeutic intervention, and that future studies should further clarify the role of muscle weakness in balance control and the pathophysiology of falls.

Purpose of Review: Gait disorders and balance impairments are one of the most incapacitating symptoms of Parkinson's disease. Here, we discuss the latest findings regarding epidemiology, assessment, pathophysiology and treatment of gait and balance impairments in Parkinson's disease., Recent Findings: Recent studies have confirmed the high rate and high risk of falls of patients with Parkinson's disease. Therefore, it is crucial to detect patients who are at risk of falling and how to prevent falls. Several studies have shown that multiple balance tests improve the prediction of falls in Parkinson's disease. Difficulty turning may be caused by axial rigidity, affected interlimb coordination and asymmetries. Turning difficulties are easily assessed by timed performance and the number of steps during a turn. Impaired sensorimotor integration, inability of switching between sensory modalities and lack of compensatory stepping may all contribute to the high incidence of falls in patients with Parkinson's disease. Similarly, various studies highlighted that pharmacotherapy, neurosurgery and physiotherapy may adversely affect balance and gait in Parkinson's disease., Summary: Insights into the pathophysiology of Parkinson's disease continue to grow. At the same time, it is becoming clear that some patients may in fact deteriorate with treatment. Future research should focus on the development and evaluation of multifactorial fall prevention strategies.

We examined the effect of bilateral subthalamic nucleus stimulation on levodopa-resistant balance impairment in 14 patients with Parkinson's disease and 18 matched controls. Instability was quantitatively assessed using standardized multidirectional dynamic posturography. Patients were tested after taking a suprathreshold dose of levodopa, both with stimulators turned on and off. Patients with stimulators turned off were more unstable than controls following backward directed perturbations. Overall, patients' instability did not improve with STN stimulation, and considerable inter-individual variability was noted. Of note, marked levodopa- resistant axial motor symptoms before surgery correlated with an adverse treatment effect. We conclude that STN stimulation does not alleviate levodopa-resistant postural instability in Parkinson's disease.

Knee movements play a critical role in most balance corrections. Loss of knee flexibility may cause postural instability. Conversely, trained voluntary knee flexions executed during balance corrections might help to overcome balance deficits. We examined whether bilateral knee flexion could be added to automatic balance corrections generated by sudden balance perturbations. We investigated how this could be achieved and whether it improved or worsened balance control. Twenty-four healthy subjects participated in three different test conditions, in which they had to flex their knees following an auditory cue (VOLUNTARY condition), had to restore their balance in response to multidirectional rotations of a support surface (REACTIVE condition), or the combination of these two (COMBINED condition). A new variable set (PREDICTED), calculated as the mathematical sum of VOLUNTARY and REACTIVE, was compared with the COMBINED variable set. COMBINED responses following forward rotations were close to PREDICTED, or greater, suggesting adequate integration of knee flexion into the automatic balance reactions. For backward rotations, the COMBINED condition resulted in several near-falls, and this was generally associated with smaller knee flexion and smaller EMG responses. Subjects compensated by using greater trunk flexion and arm movements. Activity in several muscles displayed earlier onsets for the COMBINED condition following backward rotations. We conclude that healthy adults can incorporate voluntary knee flexion into their automatic balance corrections and that this depends on the direction of the postural perturbation. These findings highlight the flexibility of the human balance repertoire and underscore both the advantages and limitations of using trained voluntary movements to aid balance corrections in man.

Previous studies of patients with focal cerebellar damage underscored the importance of the cerebellum for balance control. These studies were restricted to postural control in the pitch plane, and focused mainly on leg muscle responses. Here, we examined the effect of degenerative cerebellar lesions on postural control in multiple directions, and studied how such lesions affect intersegmental coordination of the legs, trunk and arms. We formulated two main questions. (a) Do patients with cerebellar ataxia predominantly have balance problems in the sagittal or frontal planes? (b) Is instability in cerebellar ataxia associated with increased joint motion or with reduced joint motion? We selected nine patients with autosomal dominant spinocerebellar ataxia (SCA)--three with pure ataxia and six with mild extra-cerebellar features--and 12 matched controls. Upright standing subjects received support surface rotations (7.5 degrees at 60 degrees /s) that were randomly delivered in eight different directions of pitch or roll. We used full body kinematics to determine displacements of the center of mass (COM) and of individual body segments. We also collected surface EMG from 10 leg, trunk and arm muscles. Primary variables of interest were COM displacement and trunk control (angles and muscle responses). Secondary analyses focused on angles and muscle responses of the legs and arms. COM analysis demonstrated that SCA patients had greatest instability following backward and laterally directed perturbations. Major factors in causing this instability were, first, a marked reduction of stimulus-induced knee flexion and, second, excessive "hypermetric" motion of the pelvis (in roll) and trunk (in pitch). Muscle responses of SCA patients were characterized by increased late balance correcting activity. Responses of patients with pure ataxia were comparable to those of patients with mild extra-cerebellar features. A main underlying cause of postural instability in SCA patients appears to be "locking" of the knees, which may reflect compensation (by reducing interaction between body links) or reduced vestibulocerebellar control over leg muscles. The observed pathophysiology is very different from that seen in other patient populations.

Falls are common in Parkinson's disease. It remains difficult to predict these falls, presumably because clinical balance tests assess single components of postural control, whereas everyday fall mechanisms are typically more complicated. A substantial proportion of everyday falls appears to occur while Parkinson patients attempt to perform multiple tasks at the same time. Furthermore, little attention is generally paid to the possible contribution of cognitive impairments to falls. The importance of mental dysfunction is supported by the fact that cognitive loading while walking or balancing can lead to marked deteriorations in postural performance, and there is some evidence to suggest that such "dual tasking" is particularly difficult for elderly persons with dementia or depression. We examined what strategies Parkinson patients used when a basic walking task became increasingly challenging by adding additional tasks (both motor and cognitive). Most patients could perform a simple "dual task" test: simultaneously walking and answering simple questions. However, as the walking task became more complex, patients' performance began to deteriorate. Interestingly, this was reflected not only by failure to answer questions, but also by an increasing number of blocks in motor performance (walking and balancing). This behaviour was different from that of both young and elderly controls, who appeared to sacrifice performance on the cognitive task in order to optimise their gait and balance ("posture first" strategy). Preliminary evidence suggest that impaired multiple task performance is associated with a two-fold increased risk of sustaining falls in daily life. We conclude that Parkinson patients are less inclined than healthy persons to maintain a safe gait. Instead, Parkinson patients use a "posture second" strategy and treat all elements of a complex task with equal priority, which in daily life may go at the expense of maintaining balance and lead to falls.

During stroke recovery, restoration of the paretic ankle and compensation in the non-paretic ankle may contribute to improved balance maintenance. We examine a new approach to disentangle these recovery mechanisms by objectively quantifying the contribution of each ankle to balance maintenance. Eight chronic hemiparetic patients were included. Balance responses were elicited by continuous random platform movements. We measured body sway and ground reaction forces below each foot to calculate corrective ankle torques in each leg. These measurements yielded the Frequency Response Function (FRF) of the stabilizing mechanisms, which expresses the amount and timing of the generated corrective torque in response to sway at the specified frequencies. The FRFs were used to calculate the relative contribution of the paretic and non-paretic ankle to the total amount of generated corrective torque to correct sway. All patients showed a clear asymmetry in the balance contribution in favor of the non-paretic ankle. Paretic balance contribution was significantly smaller than the contribution of the paretic leg to weight bearing, and did not show a clear relation with the contribution to weight bearing. In contrast, a group of healthy subjects instructed to distribute their weight asymmetrically showed a one-on-one relation between the contribution to weight bearing and to balance. We conclude that the presented approach objectively quantifies the contribution of each ankle to balance maintenance. Application of this method in longitudinal surveys of balance rehabilitation makes it possible to disentangle the different recovery mechanisms. Such insights will be critical for the development and evaluation of rehabilitation strategies.

We investigated whether quantified measurements of trunk sway during stance and gait tests in patients with autosomal dominant spinocerebellar ataxia (SCA) could be a useful approach to assess ataxia, which is highly relevant for adequate follow-up and future intervention studies. Examined were 11 SCA patients and 11 age-matched, healthy controls. Postural and balance control were quantified using peak-to-peak measurements of trunk angle and angular velocity, in the roll (lateral) and pitch (anterior-posterior) directions, during a battery of stance and gait tasks. In all stance tasks, trunk angle displacement and angular velocity in both the pitch and roll planes were significantly larger in the SCA group compared with the control group. Among the ataxia patients instability was more increased in the pitch than in the roll direction for two-legged stance tasks, especially when standing on foam, with pronounced oscillations in the pitch plane at 1.4 and 2.5 Hz. A similar dominance of pitch over roll instability was also observed in most gait tasks, especially for tandem gait and while walking with simultaneous head rotations. Trunk sway measurements were effective in detecting and quantifying the gait and balance abnormalities in SCA patients, suggesting that this method might be used for follow-up studies of SCA patients. Furthermore, the method might help to identify early symptomatic individuals and those patients at risk of falling. The postural instability in SCA was found to be multidirectional, although there is generally more pitch than roll instability corresponding with predominant involvement of the spinocerebellum., (Copyright 2005 Movement Disorder Society)

In this review paper, we summarize the important contributions of the basal ganglia to the regulation of postural control. After a brief overview of basal ganglia circuitries, the emphasis is on clinical observations in patients with focal lesions in parts of the basal ganglia, as the impairments seen here can serve to highlight the normal functions of the basal ganglia nuclei in postural control. Two particularly relevant functions are discussed in detail: first, the contribution of the basal ganglia to flexibility and to gaining control of balance-correcting responses, including the ability to lend priority to the elements of a postural task; and second, processing afferent information by the basal ganglia, which is increasingly recognized as being highly relevant for postural control.

Purpose of Review: To summarize the latest insights into the clinical significance, assessment, pathophysiology and treatment of falls in Parkinson's disease., Recent Findings: Recent studies have shown that falls are common in Parkinson's disease, even when compared with other fall-prone populations. The clinical impact of falls is considerable, often leading to an incapacitating fear of renewed falls. The associated costs for society are substantial. Clinical assessment often includes the retropulsion test, and recent studies have offered practical recommendations regarding the execution and scoring of this test. Insights into the pathophysiology underlying falls are growing and point to an important role for the loss of inter-segmental flexibility ('stiffness'), which predisposes patients to falls in a backward or medial-lateral direction. New evidence has clarified why Parkinson's disease patients commonly fall during transfers and under 'dual tasking' circumstances. The absence of adequately directed arm movements may explain the relatively high proportion of hip fractures in Parkinson's disease. The importance of freezing of gait as a cause of falls is recognized, and we are beginning to understand the different manifestations of gait freezing. Recent work has defined the contributions of pharmacotherapy, stereotactic neurosurgery, physiotherapy and multidisciplinary interventions in the treatment of postural instability to prevent falls in Parkinson's disease., Summary: No dramatic breakthroughs have occurred during the review period, but new information in various areas may be useful for practising clinicians. Interesting new questions have been raised that should fuel studies of pathophysiological mechanisms, which could help in the development of improved treatment strategies to reduce falls in Parkinson's disease.

Objective: To determine which test for postural instability in Parkinson's disease (PD) is reliable, valid, and easy to perform in a clinical setting., Design: Cross-sectional reliability and validity study., Setting: Academic center for movement disorders., Participants: Forty-two patients with PD and 15 controls. Based on the results of a structured interview, the patients were divided in PD-unstable (n=22) and PD-stable (n=20) groups., Interventions: Not applicable., Main Outcome Measures: Several variants of the retropulsion test with differences in execution and scoring. Responses were scored on 5 different rating scales (ratings of Nutt, Bloem, Pastor; the Unified Parkinson's Disease Rating Scale [UPDRS]; the Short Parkinson Evaluation Scale). These tests were compared with steady-stance positions., Results: The interrater reliability was high for most ratings, with weighted kappa ranging from.63 for the UPDRS to.98 for both the Pastor rating and steady-stance positions. Most ratings distinguished between the groups. However, the Nutt rating had the highest overall predictive accuracy, with a sensitivity of.63 and a specificity of.88., Conclusions: The most valid test for postural stability in PD was an unexpected shoulder pull, executed once, with taking more than 2 steps backward considered abnormal. This retropulsion test is easy to use in a clinical setting.

Objective: To examine whether trunk sway and walking speed differ between elderly "stoppers" and "nonstoppers" during a shorter version of the stops walking while talking (SWWT) test-an observational assessment of impaired dual-task performance-and during a normal walking trial., Design: The original SWWT test was administered on the way to the test room (over a distance of 150m). Then, subjects were asked to walk 2 trials of 8m while wearing a trunk sway measuring device strapped firmly to their lower back. For the first 8-m trial, no questions were asked (control trial). During the second 8-m trial, subjects were asked an easy question (What is your age?) after walking 2m., Setting: Long-stay geriatric care unit in Switzerland., Participants: Seventeen institutionalized elderly (16 women, 1 man; mean age, 86.3y; range, 79-93y). Subjects had to be able to walk at least 150m and to understand simple questions., Interventions: Not applicable., Main Outcome Measures: The amplitude of trunk sway angle and angular velocity in the forward-backward (pitch) and side-to-side (roll) directions and the duration of each trial were compared between the two 8-m walking trials with and without a question among subjects who did and did not come to a complete stop., Results: In the original SWWT test, 4 persons stopped walking while talking, compared with 8 persons who stopped in the short (8-m) walking trial when a question was asked. Persons who stopped during the 8-m trial when a question was asked had significantly longer walking durations (by 19s) and larger trunk roll angular displacements (by 5.5 degrees ) during trials, both with and without a question. For both stoppers and nonstoppers, duration was longer during the trial when a question was asked., Conclusion: A fixed and brief walking distance, coupled with a single sudden question, provided an effective method of identifying subjects who stop walking while talking. These subjects are those who have slower walking speeds and more unstable trunk control in the roll plane even under normal walking conditions. Our findings support the predictive capabilities of a brief SWWT test for the unstable and fall-prone elderly, as well as the usefulness of objective trunk sway measures to identify gait instabilities.

Purpose of Review: Falls among elderly persons create immense social problems because of their association with physical decline, serious psychosocial consequences, negative impact on the quality of life, and markedly reduced survival. In addition, falls pose high costs to the public health service. For these reasons, falls remain a popular topic for research. Here, we review several interesting developments that have been published during the past year., Recent Findings: Considerable attention has been focused on early identification of fallers and prevention strategies for falls or injuries. A remaining challenge is to implement such strategies into daily clinical practice, at acceptable costs and with good acceptance. New evidence has been generated to suggest the importance of high-level processing for postural control, but it remains difficult to predict falls based upon a simple dual tasking test. Neuroimaging studies are now beginning to provide new insights into the role of cortical structures in balance regulation, and how cortical dysfunction might contribute to falls. Posturography studies using multidirectional moving platforms or computer models of balance have provided new insights into falling mechanisms, in particular the role of abnormal protective responses (stepping or grasping) and the negative effects of stiffening. Other studies have shown how a fear of falling, a common sequel to falls, may lead to secondary degeneration of postural control, thus completing a vicious loop., Summary: While these examples illustrate that falls research is very much ongoing, one cannot speak of true progress until the scientific evidence can be implemented into real life, with falls being prevented effectively in individual cases.

We highlight a specific and hitherto poorly characterised phenotype of functional gait impairments: functional freezing of gait. Unique to the presented case is the use of compensation strategies, many of which at first sight might appear to hint towards the presence of freezing of gait typical of Parkinson's disease or another form of Parkinsonism. Importantly, however, this patient's compensation strategies involved various inconsistent and incongruent elements, supporting the diagnosis of a functional neurological disorder. Recognising the features of functional freezing also helps to appreciate better the classical manifestations of freezing of gait in Parkinson's disease. [ABSTRACT FROM AUTHOR]

Background: Previous research on concepts that are important to people living with early-stage Parkinson's indicated that 'functional' slowness, fine motor skills, and subtle gait abnormalities are cardinal concepts that are not comprehensively captured by existing patient-reported outcome (PRO) instruments that are used in clinical practice and research to assess symptoms and daily functioning within this patient population. We sought to develop novel PRO instruments to address this unmet need. Methods: PRO instrument development was led by a multidisciplinary research group, including people living with Parkinson's (termed 'patient experts'), as well as patient engagement and involvement, regulatory science, clinical, and outcome measurement experts. A first set of PRO instruments, termed Early Parkinson's Function Slowness (42 items) and Early Parkinson's Mobility (26 items), were drafted to capture 'functional' slowness, fine motor skills, and subtle gait abnormalities. These PRO instruments were used in cognitive debriefing interviews with people living with early-stage Parkinson's (who were not involved with the multidisciplinary research group) to identify issues with relevance, clarity, ease of completion, conceptual overlap, or missing concepts. Results: Sixty people living with early-stage Parkinson's were interviewed, which led to refining the items to 45 for the Early Parkinson's Functional Slowness and 23 for the Early Parkinson's Mobility PRO instruments. Refinement included rewording items to address clarity issues, merging or splitting items to address overlap issues, and adding new items to address missing concepts. The Early Parkinson's Function Slowness PRO instrument resulted in a multidimensional instrument covering upper limb, complex/whole body, general activity, and cognitive functional slowness. The Early Parkinson's Mobility PRO instrument resulted in comprehensive coverage of everyday mobility tasks, with a focus on gait concepts, plus complex/whole body, balance, and lower limb mobility. Conclusions: The Early Parkinson's Function Slowness and Early Parkinson's Mobility PRO instruments aim to address gaps in existing PRO instruments to measure meaningful symptoms and daily functioning in people living with early-stage Parkinson's. Utilizing a meticulous study design led by a multidisciplinary research group that included patient experts helped to ensure that the PRO instruments were patient-centric, content valid, and meaningful from a clinical and measurement perspective. Plain English Summary: Clinical outcome assessment tools can be used to show how a disease impacts a person's daily life. These outcomes are assessed with tools like surveys or questionnaires. In Parkinson's, most of the tools currently available do not reflect the things that are important to people living with early-stage Parkinson's. Instead, these tools were designed to assess people in later stages of the disease. In this study, the research team created two new tools to assess daily functioning in early-stage Parkinson's. People with early-stage Parkinson's were interviewed to test the new tools. The language and questions in the tools were changed based on feedback from the interviews. The tools were reviewed by a large team, including patient experts and healthcare professionals involved in Parkinson's care. Experts in outcome measures and clinical trials also reviewed the tools. The review step ensured that the tools are easy to understand and appropriate for people living with early-stage Parkinson's. The new tools focus on the symptoms and experiences that are most important to people living with early-stage Parkinson's. We hope that the tools will more clearly show the impact of early-stage Parkinson's and how it progresses. Further testing of these new tools is needed. The aim is to use them in future clinical trials to measure the experience of early-stage Parkinson's more accurately. [ABSTRACT FROM AUTHOR]

Postural instability, recurrent falls and fear of falling are common in advanced Parkinson's disease (PD). We examined the impact of fall frequency, fear of falling, balance confidence and objectively measured balance impairment (using Tinetti's Mobility Index) on health-related quality of life (HrQoL) in PD. In 74 subjects HrQoL was assessed using the 39-item Parkinson's disease Quality of Life Questionnaire [PDQ-39]. Patients were interviewed using a validated falls questionnaire, addressing fall history, consequences of falls and fear of falling. Neurological examination included Hoehn and Yahr scale, the Unified Parkinson's disease Rating Scale and Tinetti's Mobility Index. Disease severity, age and gender explained 43% of the differences in HrQoL across patients (R2 = 0.43). The combination of these factors and each of the factors fear of falling, balance confidence and fall frequency lead to 55%, 50% and 45% of explained variation, respectively. The standardised regression coefficients of these risk factors were 0.34 (fear of falling), 0.28 (balance confidence) and 0.13 (fall frequency). This suggests that fear of falling is a more important determinant of HrQoL than actual falling. These results emphasise the importance of addressing fear of falling in the clinical management of PD, and the need for development of strategies to reduce fear of falling in intervention programs. [ABSTRACT FROM AUTHOR]