Intact organization of tactile space in isolated focal dystonia

Background: Systematic perceptual distortions of tactile space have been documented in healthy adults. In isolated focal dystonia (IFD) impaired spatial somatosensory processing is suggested to be a central pathophysiological finding, but the structure of tactile space for different body parts has not been previously explored. Objectives: To assess tactile space organization with a novel behavioral paradigm of tactile distance perception in IFD and controls. Methods: Three groups of IFD patients (cervical dystonia, blepharospasm/Meige syndrome, focal hand dystonia) and controls estimated perceived distances between two touches across eight orientations on the dorsum of both hands and forehead. Results: Stimulus size judgments differed significantly across orientations in all groups replicating distortions of tactile space known for healthy individuals. There were no differences between groups in the behavioral parameters we assessed on the hands and forehead. Conclusions: Tactile space organization is comparable between IFD and healthy controls in dystonic and unaffected body parts.