1. Department of Neurology; Inselspital, Bern University Hospital, University of Bern; Bern Switzerland
2. Department of Neurology; Grosshadern, University Hospital Munich, University of Munich; Munich Germany
3. Headache Science Center, C. Mondino National Neurological Institute; Pavia Italy
4. Headache Group, NIHR-Wellcome Trust King's Clinical Research Facility, King's College London; London United Kingdom