Researchers analyzing gait in people with multiple sclerosis (MS) using wearable inertial sensors have established two new and highly sensitive observer-independent measures of disability that strongly correlate with fatigue and patient-perceived health status. Their article, titled “Disability and Fatigue Can Be Objectively Measured in Multiple Sclerosis,” was published in the journal PLOS ONE.
Disability assessment is crucial in MS, being both a primary endpoint in disease research and a therapeutic target in clinical practice for disease management. Appropriate outcome measures are essential to accurately determining if an intervention under evaluation is actually modifying the disease, and, in the clinic, for tracking MS progression and the suitability of treatment.
But disability can be difficult to define and measure in patients, and current measures are not sufficiently responsive and sensitive. Moreover, discrepancies exist between a patient’s and a clinician’s perceptions of the impact of fatigue and disability on performance.
The research team investigated the feasibility of inertial sensor-based gait analysis in MS. The study included 80 MS patients, 56 with relapsing-remitting MS (RRMS) and 24 with progressive MS, and 50 healthy controls. Clinical disability was assessed through the Expanded Disability Status Scale (EDSS) and timed 25 Foot Walk (T25FW), which measures the time necessary for a patient to walk 25 feet at maximum speed. Gait analysis was performed by using a commercially available magnetic inertial measurement unit system, seven wireless MIMUs (Xsens MTw, Xsens Technologies, Enschede, The Netherlands) placed on the pelvis, and the thigh, shank, and foot of both legs. Researchers then recorded two measurements in a one-minute walking test, and mean and standard deviation of range of motion (ROM), or mROM and sROM, respectively.
The results indicated two novel independent measures of disability. Hip mROM showed great sensitivity in the measurement of lower limb motor impairment and strongly correlated with muscle strength, being altered in patients without clinically detectable disability. The motor performance E index, defined as the sum of sROMs, was only altered in patients with moderate to severe disability, therefore functioning as a marker according to disability. It also strongly correlated with fatigue and patient-perceived health status.
Researchers concluded: “We established two novel observer-independent measures of disability. E discriminated MS patients according to disability, whereas mROMH was extremely sensitive in measuring motor impairment within patients. If confirmed in larger studies, this sensitivity will be of crucial importance for monitoring disease course and treatment effects in RRMS patients, when changes in the EDSS are small or absent, and in progressive MS patients, when also small and slow changes in the EDSS are the primary outcomes to assess.”