1. Headache Unit, Neurology Department, Hospital Universitari Vall d’Hebron, Barcelona, Spain
2. Headache Research Group, Vall d’Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain
3. Sapienza University of Rome Polo Pontino, Department of Medico-Surgical Sciences and Biotechnologies, Latina, Italy
4. University of Cantabria and Service of Neurology, University Hospital Marqués de Valdecilla and IDIVAL, Santander, Spain
5. Neurology Department, Mayo Clinic, Scottsdale, AZ, USA