Detection of postural sway abnormalities by wireless inertial sensors in minimally disabled patients with multiple scler

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JNER

RESEARCH

JOURNAL OF NEUROENGINEERING AND REHABILITATION

Open Access

Detection of postural sway abnormalities by wireless inertial sensors in minimally disabled patients with multiple sclerosis: a case–control study Andrew J. Solomon1*, Jesse V. Jacobs2, Karen V. Lomond3 and Sharon M. Henry2

Abstract Background: Common clinical neurological exams can be insensitive to balance and mobility impairment at the early stages of multiple sclerosis (MS) and may not correspond with patient reports. Instrumented measurement of standing postural sway with inertial motion sensors may provide sensitive measures of balance impairment and better correspond with patient reports. Methods: While wearing wireless inertial sensors, 20 subjects with MS – Expanded Disability Status Scale of less than 3.0 and a Timed 25 Foot Walk of 5 sec or less – and 20 age- and sex-matched control subjects stood with eyes open and eyes closed on a foam surface. Forty-six outcome measures of postural sway were derived. A stepwise logistic regression model determined which measures of instrumented sway provide independent predictors of group status. Subjects with MS also completed the Activities-Specific Balance Confidence (ABC) scale and the 12-Item MS Walking Scale (MSWS-12) as measures of subject-reported balance and mobility impairment. Results: The regression model identified medio-lateral sway path length and medio-lateral range of sway acceleration amplitude, each in the eyes-open condition, as the only two significant independent predictors to differentiate subjects with MS from those without MS (model chi-squared = 34.55, p < 0.0001): accuracy = 87.5 %, positive likelihood ratio = 6 (2.09–17.21), negative likelihood ratio = 0.12 (0.03–0.44). Range of sway acceleration amplitude significantly correlated with both ABC (Spearman’s r = −0.567, p = 0.009) and MSWS-12 scores (Spearman’s r = −0.590, p = 0.006). Conclusions: Postural sway abnormalities in subjects with MS who are minimally disabled were detected using wireless inertial sensors and may signify a superior sensitivity to identify balance impairment prior to developing clinically evident disability or impaired gait speed. Further study is needed to confirm the clinical significance and predictive value of these objectively identified balance impairments.

Background Balance impairment is common in people with multiple sclerosis (MS) and frequently impacts quality of life by decreasing mobility and increasing the risk for falls [1, 2]. The causes of balance dysfunction in MS are not well understood. More sensitive measures of

* Correspondence: [email protected] 1 Department of Neurological Sciences, University of Vermont College of Medicine, University Health Center - Arnold 2, 1 South Prospect Street, Burlington, VT 05401, USA Full list of author information is available at the end of the article

balance impairment are needed to better understand mechanisms of postural control affected by MS. A number of clinical and self-reported measures have been utilized to evaluate bal