1. From the National Institute of Neurological Disorders and Stroke (H.C.), National Institutes of Health; Department of Neurology (J.M.), University of Maryland Medical Center; Department of Neurology (A.B.S.), Georgetown University Hospital; Department of Neurosurgery (I.P.S.), Georgetown University School of Medicine; and Department of Neurology (M.T.F.), Vanderbilt University Medical Center.