Assessment of Postural Sway in Individuals with Multiple Sclerosis Using a Novel Wearable Inertial Sensor

Abstract

Balance impairment is common in individuals with multiple sclerosis (MS). However, objective assessment of balance usually requires clinical expertise and/or the use of expensive and obtrusive measuring equipment. These barriers to the objective assessment of balance may be overcome with the development of a lightweight inertial sensor system. In this study, we examined the concurrent validity of a novel wireless, skin-mounted inertial sensor system (BioStamp®, MC10 Inc.) to measure postural sway in individuals with MS by comparing measurement agreement between this novel sensor and gold standard measurement tools (force plate and externally validated inertial sensor). A total of 39 individuals with MS and 15 healthy controls participated in the study. Participants with MS were divided into groups based on the amount of impairment (MS_Mild: EDSS 2–4, n = 19; MS_Severe: EDSS ≥6, n = 20). The balance assessment consisted of two 30-s quiet standing trials in each of three conditions: eyes open/firm surface, eyes closed/firm surface, and eyes open/foam surface. For each trial, postural sway was recorded with a force plate (Bertec) and simultaneously using two accelerometers (BioStamp and Xsens) mounted on the participant’s posterior trunk at L5. Sway metrics (sway area, sway path length, root mean square amplitude, mean velocity, JERK, and total power) were derived to compare the measurement agreement among the measurement devices. Excellent agreement (intraclass correlation coefficients >0.9) between sway metrics derived from the BioStamp and the MTx sensors were observed across all conditions and groups. Good to excellent correlations (r >0.7) between devices were observed in all sway metrics and conditions. Additionally, the acceleration sway metrics were nearly as effective as the force plate sway metrics in differentiating individuals with poor balance from healthy controls. Overall, the BioStamp sensor is a valid and objective measurement tool for postural sway assessment. This novel, lightweight and portable sensor may offer unique advantages in tracking patient’s postural performance.

A Pivotal Study to Validate the Performance of a Novel Wearable Sensor and System for Biometric Monitoring in Clinical and Remote Environments

“…Earlier generations (BioStamp RC TM and investigational prototypes) of the technology have been used in academic research, including motor assessments in Parkinson disease [28], gait assessment in multiple sclerosis [13], posture classification in Huntington disease [12], postural sway in multiple sclerosis [29], and periodic leg movements in sleep (unpublished data). Additional independent research with BioStamp technology has looked at ambulatory vectorcardiography [30], spasticity [31], and more granular activities of daily living (unpublished data).…”

Fall Risk Prediction in Multiple Sclerosis Using Postural Sway Measures: A Machine Learning Approach

“…This study is secondary analysis of previously published and unpublished data focusing on mobility in MS [23-28]. All data were sampled from baseline assessments prior to any interventions.…”

A Survey of Assistive Technologies for Assessment and Rehabilitation of Motor Impairments in Multiple Sclerosis

“…In a study by Sun et al [49], static balance assessment is done by measuring the postural sway by using lightweight inertial sensors and accurately measuring sway metrics like sway area, sway path length, root mean square (RMS) sway amplitude along the anterior-posterior and medial-lateral axis, mean velocity and jerk (an indicator of the smoothness of postural sway). Postural sway refers to the horizontal movement around the center of gravity of the human body.…”

“…Based on the studies presented above, it is evident that an inertial sensor-based setup is most commonly used in several studies [24,26,27,49,50,52] and measurements from these sensors have also been proven to be reliable to categorize patients to a specific disease state and differentiate an MS patient from a healthy subject [52]. An inertial sensor like the BioStamp sensor or the Xsens sensor usually consists of a 3-dimensional gyroscope and tri-axial accelerometer sensors.…”

“…Positions of these sensors usually vary based on the kind of tests performed. For example, for timed walking tests like the Timed Up-and-Go test and the Timed 25-Foot Walk test, sensors can be mounted on each shank [27] while for a balance test like the Quiet Standing task, the sensors could be placed on the posterior trunk at L5 vertebrae [49]. The sensor placement also differed based on the kind of parameters to be measured.…”