Vivien Li1, Helen McArdle2, S Anand Trip3,4. 1. National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London, UK. 2. Portree Medical Centre, Isle of Skye, Scotland, UK. 3. National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London, UK anand.trip@nhs.net. 4. Department of Neurology, Northwick Park Hospital, LNWUH NHS Trust, Harrow, UK.