1Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
2MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK
3Department of Neurology and Neurophysiology, Guy’s and St. Thomas’ NHS Foundation Trust, Lambeth Palace Road, London SE7 1EH, UK
4Department of Neurology, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland
5Department of Neurosurgery, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland