1. MRC Centre for Neuromuscular Diseases; UCL Institute of Neurology; Queen Square London WC1N 3BG UK
2. Department of Clinical Neurophysiology; Norfolk and Norwich University Hospital; Norwich UK
3. Joint UCLH/UCL Biomedical Research Unit; Biostatistics Group; London UK
4. IRCCS Foundation; Carlo Besta Neurological Institute; Milan Italy
5. Department of Epidemiology and Biostatistics; European Institute of Oncology; Milan Italy
6. Department of Clinical Neurophysiology; National Hospital for Neurology and Neurosurgery; London UK