1 Complex Motor Disorders Service, Evelina London Children's Hospital, Guy's and St Thomas' NHS Foundation Trust, UK; Department of Women and Children's Health, King's College London, UK. Electronic address: Daniel.lumsden@gstt.nhs.uk.
2 Complex Motor Disorders Service, Evelina London Children's Hospital, Guy's and St Thomas' NHS Foundation Trust, UK.
3 Department of Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, UK.
4 Complex Motor Disorders Service, Evelina London Children's Hospital, Guy's and St Thomas' NHS Foundation Trust, UK; Department of Women and Children's Health, King's College London, UK.