Department of Neurology and Neurosurgery (S.P., L.G., M.A.M.-R., L.T.T., K.G., L.D., M. Srour, K.P., G.B.), McGill University; Child Health and Human Development Program (S.P., M.A.M.-R., L.T.T., K.G., L.D., M. Srour, G.B.), Research Institute of the McGill University Health Centre; Department of Pediatrics (L.G., L.T.T., K.G., L.D., M. Srour, G.B.), McGill University, Montreal, Quebec, Canada; Division of Clinical and Metabolic Genetics (L.G.), Division of Neurology, the Hospital for Sick Children, University of Toronto, Ontario, Canada; Department of Pathology (C.F.-B.), CHU Sainte-Justine, Université de Montreal, Quebec, Canada; Division of Pathology and Laboratory Medicine (M.K.D.), Phoenix Children's Hospital, AZ; Department of Human Genetics (L.T.T., K.G., L.D., G.B.), McGill University, Montreal, Quebec, Canada; McGill University (K.P.), Brain Tumour Research Center Montreal Neurological Institute and Hospital, Quebec, Canada; Department of Neurology (D.L.R.), Department of Clinical Genomics, Department of Pediatrics, Mayo Clinic, Rochester, MN; Department of Pediatrics (M. Saito), University of California Riverside School of Medicine, Riverside Medical Clinic, CA; Department of Pediatrics (S.C.), Beaver Medical Group, Redlands, CA; Division of Pediatric Neurology (S.L.), Department of Pediatrics, Klinikum Dritter Orden, Munich, Germany; Institute of Human Genetics (B.A., T.B.H.), Technische Universität München, Munich, Germany; Institute of Medical Genetics and Applied Genomics (T.B.H.), University of Tübingen, Germany; Department of Neurology (I.T.-M., F.I.M., N.R.-E.), Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Canary Islands, Spain; Department of Neurology (D.P.), Children's Hospital of Eastern Ontario, University of Ottawa, Ontario, Canada; Department of Pediatrics (S.N.) and Department of Neurology (A.G.), Wake Forest School of Medicine, Winston-Salem, NC; Adult and Paediatric National Metabolic Service (E.G.), Starship Children's Hospital, Auckland, New Zealand; and Division of Medical Genetics (G.B.), Department of Specialized Medicine, Montreal Children's Hospital and McGill University Health Centre, Quebec, Canada.