Activation of the geste antagoniste improves speed of finger tapping in organic and functional dystonia.

Abstract

Objectives The geste antagoniste is a typical feature of dystonia's motor phenomenology. Gestes may also occur in functional dystonia. We investigated how gestes affect the kinematics of voluntary movement. Design Cross-sectional study. Subjects Twenty-three patients with organic dystonia and three with functional dystonia were studied. Methods Finger tapping was assessed while subjects wore electromagnetic sensors secured to index finger and thumb. Subjects were instructed to tap 'as fast and as big as possible' for 15 s, first with and then without activation of their geste. Precise position and orientation data, in six degrees of freedom, were recorded. Separable motor components were derived from a comparison of the x, y and z coordinates of each sensor. The product of amplitude and frequency, giving the sensor excursion per unit time, was used as a measure of average speed. A repeated measures ANOVA was conducted, with the factors CONDITION (with vs without geste), HAND (dominant vs non-dominant) and GROUP (organic vs functional). Results For average speed, there was a significant effect of CONDITION'patients with both organic and functional dystonia performed better with geste (F1,24=13.5; p=0.001). There was no main effect of HAND or GROUP. Conclusions Geste antagonistes enhance motor performance in organic and functional dystonia. These selective voluntary movements may have a general effect on the execution of motor plans in dystonia. Sample numbers were too small to allow meaningful analysis of GROUP effects.