Proprioceptive illusion induced by tendon vibration on the upper limb in stroke patients

Abstract

Muscle vibration leads to agonist muscle contraction and antagonist muscle relaxation, this is the Tonic Vibration Reflex (TVR) [1] . Central nervous system interprets tendon vibration as a lengthening of this one inducing a virtual movement sensation [2] . The objective of this study is to observe this effect after stroke. Thirty-eight subjects have been evaluated: 19 stroke patients (10 men, 60.7 ± 9.8 years old) and 19 healthy subjects (5 men, 56 ± 11 years old). Vibrators (VibraSens VB200, TechnoConcept) were placed on the biceps brachii and wrist flexors tendons. Each subject received a vibration (80 Hz, 40 s) for each upper limb. An accelerometer was placed on the forearm in order to quantify the TVR with the elbow flexion angle. Movement perception of the subject was highlighted through a perception score created for the study. Subjects were seated on a chair, blindfolded, dangling arm. Flexion angle of the elbow (TVR) was identical on the left (32.2 ± 22.9°) and right (35.2 ± 32.2°) healthy subjects upper limb. For stroke patients it was identical on the healthy upper limb (33.1 ± 21.2°) compared to the upper limb of healthy subjects but greatly decreased on the deficient upper limb (9.6 ± 13.7°) of stroke patients compared to their healthy upper limb ( P = 0.0003). Perception score was less important on the hemiplegic side than the healthy side ( P < 0.0001) and was correlated to motor impairment (Fugl-Meyer) ( P < 0.0001, r = 0.687) and spasticity ( P < 0.00001). Anaesthesia was not correlated to a low score of perception, but only 3 subjects were concerned. TVR and usual movement illusion under tendon vibration are affected on the hemiplegic side after stroke. Any relationship or not on the observed deficiencies require confirmation with a larger sample.