Differential activation in the primary motor cortex during individual digit movement in focal hand dystonia vs. healthy

Purpose: The pathophysiology of focal hand dystonia (FHD) is not clearly understood. Previous studies have reported increased and decreased cortical activity associated with motor tasks. The aim of this study was to investigate blood oxygen level dependent (BOLD) signal changes in functional magnetic resonance imaging within the hand area of primary motor cortex during cued movement of individual digits. Methods: Eight healthy individuals and five individuals with right hand FHD participated. Beta weight contrasts were examined within the hand area of the motor cortex. Results: In both groups, BOLD signal changes in the hemisphere contralateral to the moving hand were greater in the left hemisphere than the right. Between groups, no difference was found during control of the left hand, but a significant difference was seen during right hand movement; specifically, individuals with dystonia showed increased contralateral and decreased ipsilateral cortical response associated with the affected hand as compared to healthy individuals. This suggests a similar, albeit exaggerated pattern of activation in individuals with FHD on the affected side. Conclusions: These results suggest different levels of ipsilateral and contralateral activation between healthy and dystonic individuals but also show a relative difference between symptomatic and asymptomatic control within the patient population.