Turning Toward Monitoring of Gaze Stability Exercises: The Utility of Wearable Sensors

Wearable sensor and smartphone assisted vestibular physical therapy for multiple sclerosis: usability and outcomes

Introduction

Vertigo, dizziness, gaze instability and disequilibrium are highly prevalent in people with MS (PwMS) and head movement induced dizziness is commonly reported. Vestibular physical therapy (VPT) is a specialised, non-invasive and effective therapy for these problems but usually involves travel for the person to a specialist center with both personal and carbon costs. The use of wearable sensors to track head movement and smartphone applications to deliver and track programs has potential to improve VPT in MS.

Methods

This study investigated the usability and effects of a commercially available digital VPT system (wearable head sensor, smartphone app and clinician software) to deliver VPT to PwMS. A pre/post treatment design was employed and the primary outcome was the System Usability Scale (SUS). Other patient reported outcomes were the Service User Acceptability Questionnaire (SUTAQ), the Patient Enablement Instrument (PEI) and the Dizziness Handicap Inventory (DHI). Physical outcomes measurements included Mini-BESTest (MB), Modified Dynamic Gait Index (mDGI), Gait Speed (GS), Dynamic Visual Acuity (DVA) and head kinematics and symptoms during exercise.

Results

Sixteen PwMS (14 female), mean age 44(±14) years were recruited to the study and twelve completed VPT. Mean adherence to exercise, measured digitally was 60% (±18.4). SUS scores were high at 81 (±14) and SUTAQ scores also demonstrated high levels of satisfaction and acceptability of the system. Statistically significant improvements in MB (mean change 2.25; p = 0.004), mDGI (median change 1.00; p = 0.008), DVA (median change -1.00; p = 0.004) were found. Head frequencies significantly improved with concurrent decreased intensity of dizziness during head movements (mean change across 4 gaze stabilization exercises was 23 beats per minute; p < 0.05). Non-significant improvements were seen in DHI (p = 0.07) and GS (p = 0.15). 64.5% of follow up visits were conducted remotely (video or phone), facilitated by the system.

Discussion

This study had two main outcomes and benefits for PwMS. Firstly, we showed that the system used was both acceptable and could be used by PwMS. Secondly, we demonstrated an improvement in a range of dizziness, balance and gait metrics with remotely delivered care. This system has the potential to positively impact on MS physiotherapy service provision with the potential to deliver effective remote care.

Head movement kinematics are altered during gaze stability exercises in vestibular schwannoma patients

Gaze stability is the ability of the eyes to fixate a stable point when the head is moving in space. Because gaze stability is impaired in peripheral vestibular loss patients, gaze stabilization exercises are often prescribed to facilitate compensation. However, both the assessment and prescription of these exercises are subjective. Accordingly, here we quantified head motion kinematics in patients with vestibular loss while they performed the standard of care gaze stability exercises, both before and after surgical deafferentation. We also correlate the head kinematic data with standard clinical outcome measures. Using inertial measurement units, we quantified head movements in patients as they transitioned through these two vestibular states characterized by different levels of peripheral damage. Comparison with age-matched healthy control subjects revealed that the same kinematic measurements were significantly abnormal in patients both pre- and post-surgery. Regardless of direction, patients took a longer time to move their heads during the exercises. Interestingly, these changes in kinematics suggest a strategy that existed preoperatively and remained symmetric after surgery although the patients then had complete unilateral vestibular loss. Further, we found that this kinematic assessment was a good predictor of clinical outcomes, and that pre-surgery clinical measures could predict post-surgery head kinematics. Thus, together, our results provide the first experimental evidence that patients show significant changes in head kinematics during gaze stability exercises, even prior to surgery. This suggests that early changes in head kinematic strategy due to significant but incomplete vestibular loss are already maladaptive as compared to controls.