Detection of postural sway abnormalities by wireless inertial sensors in minimally disabled patients with multiple sclerosis: a case-control study.
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.
Department of Neurological Sciences, University of Vermont College of Medicine, University Health Center - Arnold 2, 1 South Prospect Street, Burlington, VT, 05401, USA. Andrew.Solomon@uvm.edu.
Andrew J
AJ
Solomon
Department of Rehabilitation and Movement Science, University of Vermont, Burlington, VT, USA.
Jesse V
JV
Jacobs
School of Health Sciences, Central Michigan University, Mt Pleasant, MI, USA.
Karen V
KV
Lomond
Department of Rehabilitation and Movement Science, University of Vermont, Burlington, VT, USA.
Sharon M
SM
Henry
D000054:Acceleration; D000328:Adult; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D004185:Disability Evaluation; D006233:Persons with Disabilities / Q000534:rehabilitation; D056228:Feedback, Sensory; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D009038:Motion; D009103:Multiple Sclerosis / Q000534:rehabilitation*; D004856:Postural Balance; D011788:Quality of Life; D016138:Walking; D059015:Wireless Technology