1 Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and UK Dementia Research Institute, University College London, London, UK. Electronic address: j.sleigh@ucl.ac.uk.
2 Department of Neuromuscular Diseases and UCL Queen Square Motor Neuron Disease Centre, UCL Queen Square Institute of Neurology, and UK Dementia Research Institute, University College London, London, UK.