Measurement of post-stroke spasticity based on tonic stretch reflex threshold: implications of stretch velocity for clinical practice

Abstract

Purpose: The most commonly used method for the clinical evaluation of spasticity is the modified Ashworth scale (MAS), which is subjective. In this regard, the spasticity assessment through the tonic stretch reflex threshold, which is an objective method, has emerged as an alternative. It is based on the value of the dynamic stretch reflex threshold, which is measured at different stretch velocities. However, by this definition, it is not possible to define the speed at which passive stretches should be performed during evaluation.Objective: This study aimed to evaluate whether the speed-variation sequence used to acquire the dynamic stretch reflex threshold influences the tonic stretch reflex threshold (TSRT) and, consequently, the estimation of spasticity by this method.Methods: Three forms of stretching-variation speed were adopted, i.e., increasing, decreasing, and randomised. The study was performed using 10 post-stroke patients.Results and Conclusions: The results showed that the stretch protocols were not all the same and that the method of increasing was most suitable for performing manual passive stretches to evaluate TSRT in these patients. Another analysis was the correlation between MAS and tonic stretch reflex threshold; a weak correlation was observed between the increasing and decreasing methods, and moderate correlation was observed between the random methods.Implications for RehabilitationWe demonstrated that the protocol of execution of passive stretches influences in the measurement of the tonic stretch reflex threshold (TSRT). We recommend the method of increasing velocity for performing manual passive stretches.We also build software with a reliable biological data acquisition system, which makes acquisition and processing of data in real time. In this way, the TSRT is a promising quantitative measure to assess post-stroke spasticity, calculated automatically.We also we provided the use of portable instruments to facilitate the assessment of spasticity in clinical practice.