Single Photon Emission Computed Tomography (SPECT) to Study Paroxysmal Hyperkinetic Movement Disorders

This study will use single photon emission computed tomography (SPECT) to determine what areas of the brain are responsible for paroxysmal hyperkinetic movement disorders. Patients with these disorders have sudden, brief attacks of movement, similar to epileptic seizures, but without loss of consciousness. SPECT is a nuclear medicine test that produces three-dimensional images of the brain, showing blood flow and function in different brain regions. This test, which can detect the focus of epileptic seizures, will be used in this study to scan patients while they are experiencing a hyperkinetic movement attack, while they are not having and attack, and while they are simulating an attack. Patients 18 years of age and older who have paroxysmal movement attacks that can be easily induced by a specific trigger, such as a sudden movement or prolonged exercise, may be eligible for this study. Candidates will be screened with a medical history and review of their medical records, physical examination, videotape of attacks, and, for women, a pregnancy test. Participants will have three SPECT scans, separated from each other by at least 48 hours. Before each scan, the subject will perform an activity that ordinarily precipitates a movement attack, such as standing up from a chair, assuming a certain posture, or doing something strenuous. Each scan will try to record one of the following conditions: * The subject performs the trigger activity, but does not have an attack; * The subject performs the trigger activity and has an involuntary attack as a result; * The subject performs the trigger activity and does not have an attack, but then mimics an attack voluntarily. After the condition is recorded, the subject will be given an injection of a radioactive agent called 99m Technetium and will then relax quietly for 40 to 60 minutes before the SPECT scan. For the scan, the subject lies on an examination table and the SPECT camera is moved near and around the head to image t