1. National Hospital for Neurology and Neurosurgery; Department of Neurology and MRC Centre for Neuromuscular Diseases; Queen Square London UK WC1N 3BG
2. National Hospital for Neurology and Neurosurgery; MRC Centre for Neuromuscular Diseases; PO Box 114 Queen Square London UK WC1N 3BG
3. University of Oxford; Pain Research and Nuffield Department of Clinical Neurosciences (Nuffield Division of Anaesthetics); Pain Research Unit Churchill Hospital Oxford Oxfordshire UK OX3 7LE