1. Headache Unit, Neurology Department, Vall d’Hebron University Hospital, Barcelona, Spain
2. Headache and Neurological Pain Research Group, VHIR, Universitat Autonoma of Barcelona, Barcelona, Spain
3. Headache Science Center, IRCCS Mondino Foundation, Pavia, Italy
4. Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
5. Medical Faculty of the University Duisburg-Essen, Essen, Germany
6. Department of Neurology, Thomas Jefferson University Hospital, Philadelphia, PA, USA