1. Department of Medicine, Toxicology and Dermatology, Faculty of Medicine, University of Valladolid, 47002 Valladolid, Spain
2. Headache Unit, Department of Neurology, Hospital Clínico Universitario de Valladolid, 47003 Valladolid, Spain
3. Imaging Processing Laboratory, Escuela Superior de Telecomunicaciones (ETSI), Universidad de Valladolid, 47002 Valladolid, Spain
4. Department of Neurology, Hospital Universitario de Burgos, 09006 Burgos, Spain