University of Southampton, University of Southampton, University of Southampton, NHS Foundation Trust - Aintree University Hospital, University of Liverpool, University of Liverpool - Liverpool Clinical Trials Centre, University of Southampton - University Hospital Southampton NHS Foundation Trust, The University of Manchester, King’s College London - Institute of Psychiatry, Psychology and Neuroscience, King’s College London, Government of the United Kingdom - Chelsea and Westminster Hospital NHS Foundation Trust, University College London, Encephalitis International, University of Liverpool, University College London, University of Cambridge, University of Cambridge - Division of Anaesthesiology, University of Southampton, University of Southampton, University of Liverpool - Institute of Infection and Global Health, Newcastle University, King’s College London - Institute of Psychiatry, Psychology & Neuroscience (IoPPN), UCL Institute of Neurology - Centre for Neuromuscular Disease, University College London - MRC Center for Neuromuscular Diseases, NHS Foundation Trust - Poole, North Middlesex University Hospital, Imperial College Healthcare NHS Trust - Department of Neuroradiology, Southmead Hospital - Department of Neurology, University Hospital Southampton NHS Foundation Trust - Wessex Neurological Centre - Department of Neurology, University of Edinburgh, University of Edinburgh, University College London, University of Oxford, University College London, University of Liverpool - Institute of Infection, Veterinary and Ecological Sciences, Alder Hey Children's NHS Foundation Trust - Department of Neurology, University College London - MRC Clinical Trials Unit, Newcastle University, University of Liverpool - Institute of Infection and Global Health and Clinical Neurosciences, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, UK