1. Servicio de Neurologia; Hospital Universitario Virgen del Rocío; Seville; Spain
2. MRC Centre for Neuromuscular Diseases; UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery; Queen Square; London; WC1N 3BG
3. Division of Neuropathology and Department of Neurodegenerative Disease; Institute of Neurology; Queen Square; London
4. UCL Institute of Neurology; Department of Brain Repair and Rehabilitation; Queen Square; London