1 From the Departments of Neuroradiology (A.M., A.V., M.G.) and Neurology (S.S.), University of Cincinnati Medical Center, 234 Goodman St, Cincinnati, OH 45267; Department of Neuroradiology, Azienda Ospedaliero Universitaria di Cagliari, Monserrato (Cagliari), Italy (L.S.); Departments of Neuroradiology (R.G., M.L.) and Neurology (A. Padovani, E.P.), Spedali Civili, University of Brescia, Brescia, Italy; Department of Pediatric Neuroradiology, G. Gaslini Children's Research Hospital Genoa, Italy (A.R.); Department of Epidemiology and Biostatistics (B.Z.) and Department of Pediatrics (S.B.), Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Department of Neuroradiology, A.O.U. "Maggiore d.c." University of Eastern Piedmont, Novara, Italy (A.C., A. Paschè); and Department of Neuroradiology, Azienda Ospedaliero Universitaria di Sassari, Sassari, Italy (P.C.).