1 Children's Neurosciences (S.B., M.L.), Evelina London Children's Hospital, Kings Health Partners Academic Health Science Center, UK; Department of Pediatric Neurology (S.B., M.K.), Children's University Hospital, Temple Street, Dublin, Ireland; Department of Statistics (C.W.), Trinity College, Dublin, Ireland; Nuffield Department of Clinical Neurosciences (Y.H., A.V., M.L.), John Radcliffe University Hospital, Oxford, England; Texas Children's Hospital (E.M., J.J., A.S.), Baylor College of Medicine, Houston, TX; Neuroimmunology Group (R.C.D.), Institute for Neuroscience and Muscle Research, The Kids Research Institute at the Children's Hospital at Westmead, University of Sydney, Australia; and TY Nelson Department of Neurology and Neurosurgery (R.C.D.), Children's Hospital at Westmead, Sydney, Australia.