Center for Translational Neuroscience Distinguished Speaker Series

1. Center for Translational Neuroscience Distinguished Speaker Series Rayford Auditorium, Biomed II Bldg. Tuesday, November 27, 12 noon Pathophysiology of Focal Dystonia and Implications for Treatment Mark Hallett, M.D. CHIEF, HUMAN MOTOR CONTROL SECTION, National Institute for neurological Disorders, National Institutes of Health, Bethesda, MD

2. Dystonia is characterized by involuntary muscle spasms and abnormal postures. There are many different types of dystonia, and most physiological studies have been done on adult onset focal dystonia particularly focal hand dystonia. Epidemiological data suggest that the focal dystonias are related to each other, and that there is a genetic substrate that can predispose to developing the disorder. There are three main physiological abnormalities that have been found in patients, all of which may represent the effect of the genetic abnormality. The first abnormal finding in focal dystonia is loss of inhibition. Loss of inhibition can be demonstrated for motor cortical function using transcranial magnetic stimulation techniques. From a functional point of view, a failure of “surround inhibition” may be particularly important since overflow movement is a principal abnormality. A second abnormality in focal dystonia is increased plasticity of the motor cortex. This abnormality may be an important link in demonstrating how environmental influences can trigger dystonia. Increased plasticity may arise from decreased inhibition so the inhibitory problem may well be more fundamental. The third abnormality is deranged sensory function. Although there is no apparent sensory loss, detailed testing of spatial and temporal discrimination reveals subtle impairments. Each of these abnormalities has suggested possible therapeutic approaches.