Wearable sensors detect mild gait disturbances in early multiple sclerosis

Wearable inertial sensors can detect gait disturbances with high sensitivity even during the early stages of multiple sclerosis (MS), where established clinical global scales may miss slight deviations in gait, according to a recent study.

“Wearable inertial sensors are sensitive to differentiate patients in the early stages of MS,” the researchers said, pointing out that “the linear trend measured using inertial sensors could serve as a surrogate parameter of motor fatigue.”

The researchers enrolled 88 MS patients and 31 healthy controls who were made to wear the wearable sensors as they performed a 6-minute 25-feet walk test. Gait parameters measured included walking speed, minimal toe-to-floor distance, stride length and duration, and the duration of the stance and swing phases. Self-reported subjective fatigue was likewise assessed.

MS patients were further divided into three groups according to their Expanded Disability Status Scale (EDSS) scores: MS group 1 (EDSS 0.0–1.0; n=27), MS group 2 (EDSS 1.5–2.0; n=29), and MS group 3 (EDSS 2.5–5.0; n=32). Across all MS groups and in the control group, all gait parameters were normally distributed, except for stance phase time in the MS group 2. [BMC Neurol 2021;21:337]

Compared to controls, walking speed was significantly slower in MS groups 2 and 3 (1.47±0.19 and 1.30±0.25 vs 1.67±0.18 m/s, respectively; p<0.05 for both). Stride length (1.47±0.13 and 1.33±0.20 vs 1.61±0.16 m; p<0.05 for both) was likewise shorter in MS groups 2 and 3, while stance phase duration was significantly prolonged (0.55±0.05 and 0.58±0.07 vs 0.51±0.03 s; p<0.05 for both).

Two-way repeated-measures analysis of variance was then performed to assess linear trends in gait parameters, which further confirmed that gait was altered over time in MS patients. In particular, walking speed, stride length, and minimum toe-to-floor distance all significantly and linearly decreased with time, while stride time and stance and swing phase times increased (p=0.000 for all). No such effect was observed for controls.

Self-reported fatigue data were available for 70 patients. Those in MS groups 2 and 3 reported significantly higher fatigue scores than controls (9.6±7.1 and 17.7±8.3 vs 2.2±4.0 points; p<0.05 for both).

“We suggest that these mean gait parameters, measured with wearable inertial sensors, are suitable for separating MS patients, even in the early stages of MS, in which the EDSS may not provide information about deviations in gait behaviour,” the researchers said.

In contrast, while linear trend data reveal a temporal dimension of such gait disturbances, they seem to not differ across disease stages and may thus be insufficiently sensitive to very mild alterations, they continued.

“If it can be shown in future studies that these parameters obtained by means of wearable inertial sensors show sufficient test-retest reliability in MS, we recommend that classic timed walking tests in routine clinical practice should be replaced by readily and automatically applicable gait assessments,” the researchers said.