1. Department of Neurology, Danish Headache Center, Copenhagen University Hospital—Rigshospitalet, Copenhagen, Denmark
2. Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
3. Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States
4. Harvard Medical School, Boston, MA, United States
5. Department of Neurology, Athens Naval Hospital, Athens, Greece
6. Department of Brain and Spinal Cord Injury, Copenhagen University Hospital—Rigshospitalet, Copenhagen, Denmark