From the UCL Queen Square Institute of Neurology (S.Z., S.K., L.H.-H., H.M.C., S.M.S.), London; Chalfont Centre for Epilepsy (S.Z., S.K., H.M.C., S.M.S.), Buckinghamshire; Department of Neurology (D.S., A.V., J.H.C., M.A.K.), Great Ormond Street Hospital; Clinical Neurosciences (A.V., J.H.C.), and Neurogenetics Group (D.S., M.A.K.), Developmental Neurosciences NIHR BRC UCL Great Ormond Street Institute of Child Health, London; School of Life Sciences (S.K.), Faculty of Science and Engineering, Anglia Ruskin University, Cambridge, UK; Department of Neurology and Clinical Neurophysiology (K.M.G., M.D.K., B.J.L.), Children's Health Ireland at Temple Street, Dublin 1; School of Medicine and Medical Sciences (K.M.G., M.D.K.), University College Dublin, Dublin 4, Ireland; Danish Epilepsy Centre (R.S.M., T.B.H.), Dianalund; Department of Regional Health Research (R.S.M.), University of Southern Denmark, Odense; Department of Paediatric Neurology (R.S., A.A.M., A.M.), Bristol Royal Hospital for Children, UK; Pediatric Neurology (W.F.), Department of Pediatrics, Faculty of Medicine and University Hospital Cologne, University of Cologne; Institute of Human Genetics (T.B.), University of Leipzig Medical Center, Germany; Departement de Neuropediatrie (D.D.), Centre de Référence Neurogénetique Mouvements Anormaux, Hôpital Armand Trousseau, and Department of Genetics (B.K., C.M.), La Pitié-Salpêtrière Hospital, APHP, Sorbonne University, Paris; Centre de Référence Déficiences Intellectuelles de Causes Rares (C.M.); Departement de Pediatrie (N.B.), American Memorial Hospital, CHU Reims; CReSTIC (N.B.), University of Reims Champagne-Ardennes, France; University of Bristol (A.A.M.); Department of Haematology (A.S.-J.) and Cambridge Institute for Medical Research (F.L.R.), University of Cambridge; NIHR BioResource (A.S.-J., F.L.R.), Cambridge University Hospitals NHS Foundation Trust; Paediatric Neurology (A.B.), Great North Childrens Hospital, Newcastle upon Tyne; Population Health Sciences Institute (A.B.), Newcastle University, UK; Applied & Translational Genomics Group (H.S., S.W.), VIB-Center for Molecular Neurology, University of Antwerp; and Department of Neurology (H.S., S.W.), University Hospital Antwerp, Belgium.