 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. 