1. Danish Headache Center, Department of Neurology, Rigshospitalet – Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
2. BIDMC Comprehensive Headache Center, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
3. Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
4. Department of Clinical Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark