Tricks in dystonia: ordering the complexity

Abstract

Sensory tricks are various manoeuvres that can ameliorate dystonia. Common characteristics are well known, but their variety is wide, sensory stimulation is not necessarily the critical feature, and their physiology is unknown. To enumerate the various forms of sensory tricks and describe their nature, research findings and theories that may elucidate their neurophysiologic mechanism, we reviewed the literature pertaining to sensory tricks, including variants like motor tricks, imaginary tricks, forcible tricks and reverse sensory tricks. On the basis of this information, we propose a new classification of sensory tricks to include its variants. We highlight neurophysiologic evidence suggesting that sensory tricks work by decreasing abnormal facilitation. We tie this with established dystonia pathogenesis and postulate that sensory tricks decrease abnormally increased facilitation to inhibition ratios in the dystonic brain. It appears worthwhile for patients to search for possible sensory tricks.

Keywords: Dystonia; Motor Control; Movement Disorders; Neurophysiology, Motor.

Figure 1

Topographic nondermatomal areas of successful tactile stimuli for relief of cervical dystonia. A patient with cervical dystonia demonstrated effective sensory trick of touching areas shaded with marker.

Figure 2

Diagrammatic illustration of the possible mechanism of sensory tricks. (A) In patients with dystonia, there is an abnormally high facilitation to inhibition ratio leading to the excessive movement. (B) With the sensory input of a trick, the facilitation is reduced, normalizing the ratio and improving motor output.