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Abstract
Objectives With disease-modifying drugs on the horizon for degenerative ataxias, ecologically valid motor biomarkers are highly warranted. In this observational study, we aimed to unravel and validate markers of ataxic gait in real life by using wearable sensors.
Methods We assessed gait characteristics of 43 patients with degenerative cerebellar disease (Scale for the Assessment and Rating of Ataxia [SARA] 9.4 ± 3.9) compared with 35 controls by 3 body-worn inertial sensors in 3 conditions: (1) laboratory-based walking; (2) supervised free walking; (3) real-life walking during everyday living (subgroup n = 21). Movement analysis focused on measures of spatiotemporal step variability and movement smoothness.
Results A set of gait variability measures was identified that allowed us to consistently identify ataxic gait changes in all 3 conditions. Lateral step deviation and a compound measure of spatial step variability categorized patients vs controls with a discrimination accuracy of 0.86 in real life. Both were highly correlated with clinical ataxia severity (effect size ρ = 0.76). These measures allowed detecting group differences even for patients who differed only 1 point in the clinical SARAposture&gait subscore, with highest effect sizes for real-life walking (d = 0.67).
Conclusions We identified measures of ataxic gait that allowed us not only to capture the gait variability inherent in ataxic gait in real life, but also to demonstrate high sensitivity to small differences in disease severity, with the highest effect sizes in real-life walking. They thus represent promising candidates for motor markers for natural history and treatment trials in ecologically valid contexts.
Classification of evidence This study provides Class I evidence that a set of gait variability measures, even if accessed in real life, correlated with the clinical severity of ataxia in patients with degenerative cerebellar disease.
Glossary
- AP=
- anterior-posterior;
- CA=
- cerebellar ataxia;
- CAMild=
- mild cerebellar ataxia;
- CAMod=
- moderate cerebellar ataxia;
- CASev=
- severe cerebellar ataxia;
- CI=
- confidence interval;
- CV=
- coefficient of variation;
- DCA=
- degenerative cerebellar ataxia;
- HC=
- healthy control;
- INAS=
- Inventory of Non-Ataxia Signs;
- LatStepDev=
- lateral step deviation;
- LBW=
- laboratory-based walking;
- RLW=
- real-life walking;
- ROC=
- receiver operating characteristic;
- SARA=
- Scale for the Assessment and Rating of Ataxia;
- SARAp&g=
- Scale for the Assessment and Rating of Ataxia posture & gait subscore;
- SFW=
- supervised free walking;
- SPcmp=
- spatial step variability compound measure;
- StrideLCV=
- stride length coefficient of variation;
- StrideTCV=
- stride time coefficient of variation
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Class of Evidence: NPub.org/coe
- Received October 30, 2019.
- Accepted in final form March 2, 2020.
- © 2020 American Academy of Neurology
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