Método para avaliação quantitativa da espasticidade baseado no limiar do reflexo de estiramento tônico

Abstract

Spasticity is a motor disorder characterized as hyperexcitability of the velocitydependent stretch reflex. It is a disability commonly arising after stroke. The measurement of the spasticity is essential for its diagnosis, management of treatment and verification of the effectiveness of therapy intervention applied. In reason of the complexity and of the multifactorial nature of the phenomenon, quantifying the spasticity is a difficult and unresolved problem. There is no consensus regarding the use of a specific measurement since the methods currently employed present limitations. A promising alternative to assessment of spasticity is the indirect measurement of tonic stretch reflex threshold (TSRT). The development and enhancement of systems for its quantification are required. The aim of this study was to develop and validate an efficient method for the assessment of spasticity based on the tonic stretch reflex threshold. The quantification of TSRT was performed by signals processing from electromyographic activity and angular displacement (electrogoniometer). These signals were monitored during manual passive stretches of the affected limb applied at different velocities. The joint angle and its respective velocity value corresponding to the onset of muscle contraction in response to each stretch were identified through the implementation of efficient algorithms for detection of muscle activity and its onset within each zone stretching. The coordinates of the angle and velocity represent the dynamic stretch reflex thresholds. The TSRT was quantified by linear regression on DSRT set as an angular coordinate for zero velocity within the range of biomechanics amplitude of the joint evaluated. The spasticity of biceps brachial muscle from seven patients after stroke was evaluated by clinical application of the Modified Ashworth Scale and by the detection of the TSRT according to the developed method. The set of DSRTs was detected successfully by the techniques of signals processing applied. Therefore, the tonic stretch reflex threshold computed by the developed method may be a viable measure for quantitative evaluation of spasticity after stroke.