Pathophysiology of Focal Hand Dystonia

Objective: detailed evaluation of pathophysiology of Focal Hand Dystonia (FHD) with focus on the involvement of the parietal area, and to investigate differences in cortical mapping in the sensory and motor cortices between FHD and healthy volunteers. Study population: The study will enroll patients with FHD and Healthy Volunteers (HVs). Design: Prospective study using MRI and Physiology experiments using EMG and TMS based protocols to evaluate the differences between the groups. Outcome measures: The evaluation using fMRI will be performed under 3 conditions; 1. Rest 2. Voluntary activity 3. Motor imagery task. Outcome measures (fMRI based): We will explore the differences in BOLD signal in the parietal lobe, in FHD compared to HVs, in the different conditions. We will look for changes in the BOLD signal in the parietal sensorimotor integration area. We will use vascular occupancy imaging (VASO) to explore differences of detailed cortical mapping of neural structures between FHD and healthy volunteers. The Physiology experiments aim to explore abnormalities and differences in the baseline motor cortical excitability between the groups and evaluate the influence of continuous Theta Burst Stimulation (cTBS) on these measures. We will study the influence of cTBS on the phenomenon Cortical Silent Period (cSP) in FHD. We will also be studying the baseline Spatial and Temporal Discrimination (SDTs and TDTs), which are measures of sensory surround inhibition and have been noted to be endophenotypic of dystonia. Physiology outcomes: Baseline differential influences of PMv and IPL on motor cortical excitability and changes after cTBS of dIPL. Baseline cortical Silent Period (cSP) in the involved and uninvolved limb in FHD and the influence of cTBS on cSP in the involved limb. The TDTs/ SDTs in both the involved and uninvolved limbs in FHD compared to HVs.