Pathophysiology of Focal Hand Dystonia

Background: Little is known about the problems in brain function in focal hand dystonia (FHD) or complex regional pain syndrome (CRPS) dystonia. It is unclear why some CRPS patients develop dystonia but others do not. Researchers want to learn which area of the brain is involved in CRPS dystonia compared with FHD. Objectives: To understand why people with CRPS develop dystonia, and if these reasons are different in people with FHD. Eligibility: Adults ages 18 - 70 with CRPS dystonia OR with CRPS without dystonia OR with FHD and Healthy volunteers of similar age. Design: Participants will be screened with physical exam, neurological exam, and medical history. They may give a urine sample and will answer questions. Participants can have 4 - 5 outpatient visits or stay at the clinical center for approximately 5-6 days. Participants will have MRI scans. They will lie on a table that slides in and out of a scanner that takes pictures of their brain. They will do small tasks or be asked to imagine things during the scanning. Participants will have transcranial magnetic stimulation (TMS) sessions for a few hours, with breaks. A brief electrical current passing through a well insulated wire coil on the scalp creates a magnetic pulse. This affects brain activity. Participants may do small tasks during TMS. Participants will have the electrical activity of their muscles measured during TMS sessions. Small sticky pads will be attached to their hands and arms. Participants ability to feel 2 separate stimuli as different will be tested by using a weak electrical shock to their fingers. They will also be asked to feel small plastic domes with ridges, that may cause discomfort.