ReviewPsychometric properties of outcome measures evaluating decline in gait in cerebellar ataxia: A systematic review
Introduction
The cerebellum plays a critical role in balance and postural control, coordination of lower limb movements, and feedforward control required during gait [1,2]. Therefore, it is not surprising that gait disturbance is a major symptom of cerebellar pathology [3]. Cerebellar pathology can originate from a wide spectrum of neurological disorders, including genetic and acquired etiologies such as spinocerebellar ataxia (SCA), stroke, multiple sclerosis, traumatic brain injury and multiple system atrophy-cerebellar type (MSA-c). This heterogeneity results in static, degenerative or reversible disease progression. Furthermore, functional compartmentalization of the cerebellum results in different gait deficits corresponding to the specific location of the lesion within the cerebellum [4]. Irrespective of the rate of progression or site of lesion, the consequences of impaired gait are often falls [5], a substantial loss of independence in activities of daily living and a range of secondary impairments related to decline in physical activity.
Given the devastating impact on quality of life [5], remarkably there is no gold standard of gait evaluation in cerebellar ataxia. Studies typically use clinical rating scales, e.g. the Scale for the Assessment and Rating of Ataxia (SARA) [6] or the International Cooperative Ataxia Rating Scale (ICARS) [7], to measure overall impairment. Each of these scales comprise a component of gait evaluation, however total scores are reflective of multiple components of ataxia and rely primarily on subjective assessment. Comparatively, when gait has been specifically measured in therapeutic trials, many and varied outcome measures have been utilised [8]. The uncertainty over a preferred outcome is compounded by the many methods that can be used to evaluate gait. Instrumented gait analysis, clinical assessment and step activity outputs have the potential to provide a multitude of outputs related to gait dysfunction. Moreover, given the diversity of gait deficits evident in individuals with cerebellar ataxia, there may not be one measure that is appropriate for all pathologies. Discerning valid, reliable and responsive measures of gait dysfunction in cerebellar ataxia is crucial for guiding the selection of gait outcomes for future clinical trials and ensuring valid measurements of the efficacy of treatments targeting gait dysfunction. Moreover, sensitive measures will assist with precise diagnosis and monitoring of natural progression of gait impairment in cerebellar ataxia.
This review aimed to assess the reliability, validity and responsiveness of gait outcomes that measure walking decline in individuals with cerebellar ataxia. Gait pattern changes and functional gait assessment were both evaluated to include the World Health Organisation classification of body structure and function, and activity and participation domains [9] related to gait.
Section snippets
Search strategy
A comprehensive search of MEDLINE, CINAHL and Embase was conducted to identify relevant publications from date of inception to 22nd March 2017. Additionally, the authors’ personal libraries were manually searched for further publications. The following index terms and keywords or their synonyms were used: “ataxia” OR “cerebellar ataxia” OR “spinocerebellar ataxias” OR “Friedreich ataxia” OR “Machado-Joseph disease” OR “ataxia telangiectasia” OR “gait ataxia” AND “gait” OR “locomotion” OR
Results
The literature search yielded 2302 unduplicated publications. Title and abstract screening excluded 2058 publications with the remaining 244 reviewed in full text. Fifty-three studies met the criteria for inclusion. Characteristics of the included studies are listed in Table 1. There were 17 publications evaluating clinical measures of ambulatory assessment [4,19,[24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39]], including the Timed 25 Foot Walk
Discussion
The purpose of this review was to provide an overview of the psychometric properties of gait assessment and analysis in cerebellar ataxia. This information will inform selection of robust ambulation and gait outcomes for the evaluation of pharmacological and therapeutic interventions in cerebellar ataxia; and will guide future psychometric testing of gait outcomes. Fifty-three studies were identified, assessing 356 variables related to walking. Most studies aimed to explore gait dysfunction and
Conclusion
Given the early stage of gait evaluation and clinical trials in cerebellar ataxia, this review has provided an overview of potential gait outcomes and identified the significant gaps in knowledge of the psychometric properties of gait outcomes. The lack of high-quality psychometric evaluation of gait outcomes in cerebellar ataxia makes it difficult to determine valid, responsive and reliable measures of gait for clinical trials. This review indicates double support, single support and swing
Funding
This study was supported by the Bruce Lefroy Centre (Murdoch Children’s Research Institute), Friedreich Ataxia Association of Victoria, Friedreich Ataxia Research Association (Australasia) and the Friedreich Ataxia Research Alliance (United States of America). SM receives a National Health and Medical Research Council of Australia Postgraduate Scholarship (APP1093259). EY receives a National Health and Medical Research Council of Australia Early Career Fellowship (APP1073323). The supporting
Conflict of interest statement
SM receives a National Health and Medical Research Council of Australia Postgraduate Scholarship (APP1093259). EY receives a National Health and Medical Research Council of Australia Early Career Fellowship (APP1073323). AM, MD, NG-K, and LC report no disclosures.
Acknowledgements
This study was supported by the Bruce Lefroy Centre, Friedreich Ataxia Association of Victoria, Friedreich Ataxia Research Association (Australasia) and the Friedreich Ataxia Research Alliance (United States of America). SM receives a National Health and Medical Research Council of Australia Postgraduate Scholarship (APP1093259). EY receives a National Health and Medical Research Council of Australia Early Career Fellowship (APP1073323).
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