aDepartment of Neurology, Danish Headache Center, Copenhagen University Hospital—Rigshospitalet, Copenhagen, Denmark

bDepartment of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

cDepartment of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States

dHarvard Medical School, Boston, MA, United States

eDepartment of Neurology, Athens Naval Hospital, Athens, Greece

fDepartment of Brain and Spinal Cord Injury, Copenhagen University Hospital—Rigshospitalet, Copenhagen, Denmark

*Corresponding author. Address: Department of Neurology, Danish Headache Center, Copenhagen University Hospital—Rigshospitalet, Copenhagen, Denmark. Tel.: +45 38 63 33 85. E-mail address: [email protected] (M. Ashina).

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

H. M. Al-Khazali and C. I. Deligianni contributed equally to this work.