1. From the Departments of Neurology (A.K., W.O.T., S.S.S.-B., A.M.F.) and Radiology (E.H.M.), Mayo Clinic, Jacksonville, FL; Department of Pediatric Neurology (P.J.), Norton Children's Hospital, Louisville, KY; and Department of Neurosurgery (S.S.S.-B.), Mayo Clinic, Jacksonville, FL.