Biomechanical analysis of spasticity treatment in patients with multiple sclerosis

New metrics for clinical spasticity are needed to assess motor performance, since scales such as the Ashworth and Tardieu are unreliable. Here, we assessed outcomes of baclofen treatment in patients with multiple sclerosis (MS) using biomechanical analysis of voluntary movements.

Patients with MS and symptomatic limb spasticity were recruited for a pre-post baclofen titration study, along with age-matched healthy controls. Oral baclofen was titrated to optimize spasticity symptoms in all MS cases over 4 weeks. Clinical assessments included the Modified Ashworth Scale (MAS), Tardieu Scale (TS); elbow kinematics were measured via the Transient Acceleration Measurement Interface (TAMI); performance was measured as the score at 4 weeks minus the baseline score in all measures. Movement proficiency within TAMI was quantified through a scale-free smoothness measure, according to the regional excursion deviation (RED) from a constant-velocity approximant.

Twelve patients with MS [age: 47.8 ± 9.8 years; women: 4; disease duration: 20 ± 10 years; disease-modifying therapy use: 7; Expanded Disability Status Scale (EDSS): 6.8 ± 1.4] and eight age-matched healthy controls were evaluated concurrently (mean age: 49.5 ± 13.1 years; women = 3). In MS cases, no significant improvement in arm spasticity was observed with main effects: MAS: -41.6 ± 72.6 (p = 0.09); EDSS: -1.6 ± 10.4% (p = 0.49); and TS: -8.3 ± 2.1% (p = 0.32), -24.9 ± 63.6% (p = 0.42), and -30.7 ± 79.9% (p = 0.06), at slow, moderate, and fast speeds, respectively. However, voluntary motion smoothness, as measured by TAMI: RED, decreased significantly: 0.62 ± 0.08 versus 0.54 ± 0.09, p < 0.001, indicating significant increase in movement smoothness post treatment.

A simple biomechanical analysis of voluntary movements revealed a significant reduction of spasticity after 30 days of baclofen therapy in patients with MS that was not detected by clinical assessments.