1 Blizard Institute, Faculty of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom. Electronic address: g.giovannoni@qmul.ac.uk.
2 Blizard Institute, Faculty of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom.
3 The University of Newcastle, Australia.
4 Massachusetts General Hospital and Harvard Medical School, MA, United States.
5 Department of Paediatrics (Neurology), Hospital for Sick Children, Division of Neuroscience and Mental Health, The Hospital for Sick Children Research Institute University of Toronto, Canada.