1. Headache Unit, Neurology Department, Hospital Clínico Universitario, Valladolid, Spain
2. Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
3. Emergency Department, Hospital Clínico San Carlos, Madrid, Spain
4. Emergency Department, Hospital Rey Juan Carlos, Móstoles, Madrid, Spain
5. Headache Unit, Neurology Department, Hospital Clínico San Carlos, Madrid, Spain
6. Imaging Processing Laboratory (IPL), University of Valladolid, Valladolid, Spain
7. Department of Medicine, University of Valladolid, Valladolid, Spain
8. Universidad Complutense De Madrid, Madrid, Spain
9. Instituto De Investigación Sanitaria San Carlos (Idissc), Madrid, Spain
10. Universidad Complutense De Madrid, Spain