Sensitivity of the NeuroFlexor method to measure change in spasticity after treatment with botulinum toxin A in wrist and finger muscles.

OBJECTIVE The NeuroFlexor objectively quantifies the neural, elastic and viscous components of passive movement resistance in wrist and finger flexor muscles. In this study we investigated the sensitivity of the NeuroFlexor to changes in spasticity induced by treatment with botulinum toxin type A (BoNT-A). DESIGN Prospective observational design. SUBJECTS A convenience sample of 22 adults with post-stroke upper limb spasticity scheduled for botulinum toxin treatment. METHODS BoNT-A was given according to individual treatment plans. NeuroFlexor assessments were made before treatment and 4 and 12 weeks after. RESULTS At group level, spasticity decreased significantly at 4 weeks (expected time of maximum effect) (p = 0.04). At 12 weeks, spasticity had rebounded and no longer differed significantly from baseline (p = 0.64), i.e. in line with the pharmacodynamics of BoNT-A. At the individual level, 7 participants showed a reduction in spasticity greater than the measurement error. The reduction was dose-dependent (r(20) = 0.66, p < 0.001), and largest in participants with the highest dose. CONCLUSION At the group level, the sensitivity of NeuroFlexor is good enough to detect reduction in spasticity after treatment with BoNT-A. Further work is needed to establish the sensitivity of NeuroFlexor on an individual level.