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Objective: Quantification of lower limb spasticity after stroke and the differentiation of neural from passive muscle resistance remain key clinical challenges. The aim of this study was to validate the novel NeuroFlexor foot module, to assess the intrarater reliability of measurements and to identify normative cut-off values., Methods: Fifteen patients with chronic stroke with clinical history of spasticity and 18 healthy subjects were examined with the NeuroFlexor foot module at controlled velocities. Elastic, viscous and neural components of passive dorsiflexion resistance were quantified (in Newton, N). The neural component, reflecting stretch reflex mediated resistance, was validated against electromyography activity. A test-retest design with a 2-way random effects model permitted study of intra-rater reliability. Finally, data from 73 healthy subjects were used to establish cutoff values according to mean + 3 standard deviations and receiver operating characteristic curve analysis., Results: The neural component was higher in stroke patients, increased with stretch velocity and correlated with electromyography amplitude. Reliability was high for the neural component (intraclass correlation coefficient model 2.1 (ICC2,1) ≥ 0.903) and good for the elastic component (ICC2,1 ≥ 0.898). Cutoff values were identified, and all patients with neural component above the limit presented pathological electromyography amplitude (area under the curve (AUC) = 1.00, sensitivity = 100%, specificity = 100%)., Conclusion: The NeuroFlexor may offer a clinically feasible and non-invasive way to objectively quantify lower limb spasticity.

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.

Objective: To describe the reliability of an instrument (Neuro- Flexor) designed to be used in the clinic for quantification of the relative contribution of spasticity, elasticity and viscosity to resistance during passive wrist movements., Design: A test-retest and inter-rater reliability study., Subjects: A convenience sample of 34 adults with chronic stroke with spasticity in the hand, and a reference group of 10 healthy persons., Methods: Two raters assessed the participants with the NeuroFlexor. Elastic, viscous and neural components of passive movement resistance were quantified at the wrist. Test-retest and inter-rater intraclass correlation coefficient (ICC2.1) were calculated for each component for both raters and two sessions. Degree of measurement error was evaluated using the coefficient of variation and the repeatability coefficient., Results: Reliability was high for the neural component (test-retest: 0.90-0.96; inter-rater: 0.90-0.94), fair to good for the elastic component (test-retest: 0.79-0.88; inter-rater: 0.76-0.76), and fair to high for the viscous component (test-retest: 0.88-0.90; inter-rater: 0.75-0.80). Based on test-retest data, the coefficients of variation for the neural, elastic and viscous components were 25%, 26% and 16%, respectively, and the repeatability coefficients were 1.798, 1.897 and 1.404, respectively., Conclusion: The NeuroFlexor instrument is a reliable measure of spasticity and of muscle elasticity and viscosity in individuals with wrist and finger muscle resistance to passive stretch after stroke.