1. Department of Neurology; University of California; San Francisco CA USA
2. Headache Group; NIHR-Wellcome Trust Clinical Research Facility; King's College London; London UK
3. Department of Neurology; University of Munich Hospital - Großhadern; Munich Germany
4. Department of Neurology; The Royal London Hospital (Barts and the London NHS Trust); London UK
5. Basildon and Thurrock University Hospitals NHS Foundation Trust; Nethermayne UK
6. Department of Neurology; University Hospital Basel; Basel Switzerland
7. Division of Neuroradiology; University Hospital Basel; Basel Switzerland