1. Department of Neurology, Móstoles General Hospital, Móstoles, Madrid, Spain
2. Department of Neurology, University Hospital 12 de Octubre, Madrid, Spain
3. Department of Neurology, Nuestra Sra. del Prado Hospital, Talavera de la Reina, Toledo, Spain
4. Department of Epidemiology, University Hospital La Princesa, Madrid, Spain
5. Department of Research, Ministry of Labor and Social Affairs, Madrid, Spain