The 'geste antagonistique' induces transient modulation of the blink reflex in human patients with blepharospasm

The mechanism of action of the 'geste antagonistique', or sensory trick, used by patients with dystonic blepharospasm (BSP) to transiently diminish their symptoms is presently unknown. In this paper we examined the effects induced by a sensory trick consisting of finger contact with the face on the electrically induced blink reflex and the blink reflex excitability recovery curve to paired stimuli. The results were compared with those obtained in a group of six healthy volunteers who mimicked the manoeuvre used by the patients as a sensory trick. In all subjects, the area of R2 was significantly reduced, and the amplitude of R1 was significantly enhanced, during a mean of 10 min after the onset of finger-face contact in comparison to rest. However, there were no changes in the blink reflex excitability recovery curve. The contact-induced effect on the magnitude of the R2 component of the blink reflex is probably caused by sensory gating on trigeminal afferents. Such a reduction in the gain of trigemino-facial reflexes may partly underly the transient benefit experienced by patients with BSP with the use of sensory tricks. (C) 1998 Published by Elsevier Science Ireland Ltd. All rights reserved.