1 Queen Square MS Centre, UCL Queen Square Institute of Neurology, Faculty of Brain Sciences, University College London, London, UK/Department of Neurology, Great Ormond Street Hospital NHS Trust, London, UK.
2 Queen Square MS Centre, UCL Queen Square Institute of Neurology, Faculty of Brain Sciences, University College London, London, UK/NIHR University College London Hospitals Biomedical Research Centre, London, UK.