Walking With Horizontal Head Turns Is Impaired in Persons With Early-Stage Multiple Sclerosis Showing Normal Locomotion

BackgroundTurning the head while walking (an action often required during daily living) is particularly challenging to maintain balance. It can therefore potentially reveal subtle impairments in early-stage people with multiple sclerosis who still show normal locomotion (NW-PwMS). This would help in identifying those subjects who can benefit from early preventive exercise aimed at slowing the MS-related functional decline. ObjectivesTo analyze if the assessment of walking with horizontal head turns (WHHT) through inertial sensors can discriminate between healthy subjects (HS) and NW-PwMS and between NW-PwMS subgroups. To assess if the discriminant ability of the instrumented WHHT is higher compared to clinical scores. To assess the concurrent validity of the sensor-based metrics. MethodsIn this multicenter study, 40 HS and 59 NW-PwMS [Expanded Disability Status Scale (EDSS) <= 2.5, disease duration <= 5 years] were tested. Participants executed Item-6 of the Fullerton Advanced Balance scale-short (FAB-s) wearing three inertial sensors on the trunk and ankles. The item required to horizontally turn the head at a beat of the metronome (100 bpm) while walking. Signals of the sensors were processed to compute spatiotemporal, regularity, symmetry, dynamic stability, and trunk sway metrics descriptive of WHHT. ResultsMediolateral regularity, anteroposterior symmetry, and mediolateral stability were reduced in NW-PwMS vs. HS (p <= 0.001), and showed moderate discriminant ability (area under the receiver operator characteristic curve [AUC]: 0.71-0.73). AP symmetry and ML stability were reduced (p <= 0.026) in EDSS: 2-2.5 vs. EDSS: 0-1.5 subgroup (AUC: 0.69-0.70). The number of NW-PwMS showing at least one abnormal instrumented metric (68%) was larger (p <= 0.002) than the number of participants showing abnormal FAB-s-Item6 (32%) and FAB-s clinical scores (39%). EDSS: 2-2.5 subgroup included more individuals showing abnormal instrumented metrics (86%) compared to EDSS: 0-1.5 subgroup (57%). The instrumented metrics significantly correlated with FAB-s-Item6 and FAB-s scores (|Spearman's r(s)| >= 0.37, p < 0.001), thus demonstrating their concurrent validity. ConclusionThe instrumented assessment of WHHT provided valid objective metrics that discriminated, with higher sensitivity than clinical scores, between HS and NW-PwMS and between EDSS subgroups. The method is a promising tool to complement clinical evaluation, and reveal subclinical impairments in persons who can benefit from early preventive rehabilitative interventions.