Funding for this research was provided by:
Received: 4 January 2020
Accepted: 12 February 2020
First Online: 24 February 2020
Ethics approval and consent to participate
: All participants provided written consent to participate after receiving written and oral information in accordance with the Declaration of Helsinki of 1964, with subsequent revisions. The study was approved by the Ethics Committee of the Capital Region of Denmark (H-18008313). The study was registered retrospectively at ExternalRef removed (ExternalRef removed).
: Not applicable.
: The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Messoud Ashina is a consultant, speaker or scientific advisor for Allergan, Amgen, Alder, ATI, Eli Lilly, Novartis, and Teva, primary investigator for Alder, Amgen, ElectroCore, Novartis and Teva trials. MA has no ownership interest and does not own stocks of any pharmaceutical company. MA serves as associated editor of Cephalalgia, Headache, and co-editor of the Journal of Headache and Pain. MA is the President of the International Headache Society. Mohammad Al-Mahdi Al-Karagholi has acted as an invited speaker for Novartis and received travel grant from ElectroCore, Hashmat Ghanizada, Nanna Arngrim, Faisal Mohammad Amin, Mette Mørch-Rasmussen, Matias Metcalf-Clausen and Henrik Bo Wiberg Larsson declare they have no conflicts of interest.