1. Headache Unit, Department of Neurology, Hospital Clínico Universitario de Valladolid, Valladolid, Spain
2. Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
3. Headache Unit, Department of Neurology, Institute of Neurosciences, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria San Carlos (IdISSC), Madrid, Spain
4. Department of Emergency Medicine, Hospital Clínico San Carlos, IdiSSC, Madrid, Spain
5. Department of Neurology, Hospital Clínico San Carlos, Madrid, Spain
6. Department of Medicine, Universidad Complutense de Madrid, Madrid, Spain
7. Department of Medicine, School of Medicine, Universidad de Valladolid, Valladolid, Spain