Yael Hacohen1, Angela Vincent2. 1. Department of Paediatric Neurology, Great Ormond Street Hospital for Children, London, UK; Department of Neuroinflammation, Queen Square MS Centre, UCL Institute of Neurology, London, UK. Electronic address: y.hacohen@ucl.ac.uk. 2. Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford, UK.