University of Cincinnati - Department of Neuroradiology, Universita di Cagliari -Department of Neuroradiology, University of Cincinnati - Department of Neuroradiology, University of Brescia -Department of Neuroradiology, Istituto G. Gaslini Children Hospital Scientific Institute - Department of Pediatric Neuroradiology, University of Cincinnati - Department of Neuroradiology, University of Cincinnati - Department of Neurology, Cincinnati Children's Hospital Medical Center - Department of Epidemiology and Biostatistics, University of Eastern Piedmont - Department of Neuroradiology, Cincinnati Children's Hospital Medical Center - Department of Pediatrics, Università degli Studi di Sassari - Department of Neuroradiology, University of Brescia - Department of Neurology, University of Brescia - Department of Neurology, University of Brescia - Neurology Unit and University of Brescia -Department of Neuroradiology