1. Department of Neuromedicine and Movement Science, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway
2. Department of Neurology and Clinical Neurophysiology, St. Olavs Hospital, Trondheim, Norway
3. Norwegian Headache Research Centre (NorHEAD), Trondheim, Norway
4. Department of Clinical Medicine, University of Bergen, Bergen, Norway
5. Department of Neurology, Haukeland University Hospital, Bergen, Norway
6. Division of Research, National Institute of Occupational Health, Oslo, Norway