Reaching international consensus on the definition of refractory migraine using the Delphi method

AimDespite its frequency in tertiary headache centers, the International Classification of Headache Disorders, 3rd edition (ICHD-3) does not include refractory migraine. Multiple definitions have been proposed with a recent 2020 proposal for both refractory migraine and resistant migraine by the European Headache Federation (EHF). The aim is to reach an international consensus on the definition of refractory migraine.MethodsThis study is a Delphi consensus carried out by a group of international experts in headache medicine. Following a focus group, a panel of 20 experts and one facilitator reviewed the EHF proposed criteria to build upon their definitions. The Delphi consensus was conducted across five rounds. Questions with >70% consensus were deemed to have strong agreement, 60-70% consensus was deemed minor agreement, and <60% deemed no agreement. A final meeting was held to discuss any concerns and specific wording.ResultsThe Delphi consensus led to the development of four key categories: refractory migraine, probable refractory migraine, resistant migraine, and treatment-responsive migraine. Similar to the EHF 2020 definitions, refractory migraine requires treatment failure of all evidence-based classes, and resistant migraine requires failure of at least three classes. Probable refractory migraine criteria were designed to account for situations where treatment access barriers may prevent trials of certain medication classes (e.g. pediatrics, low to middle-income countries, lack of insurance coverage). Finally, treatment-responsive migraine criteria were developed to allow for standardization in research studies comparing refractory or resistant migraine to migraine that is treatment-responsive.ConclusionsThese four categories may aid in enrollment for studies on pathophysiology, biomarkers, and new treatment targets. Clinically, the criteria for refractory and resistant migraine will help with clinical decision-making by reinforcing the need to try evidence-based treatments and by providing guidance regarding when to try more aggressive treatment approaches. These criteria may also increase attention to this population's disease burden to help advocate for them as a specific migraine subgroup. Field testing in diverse clinical settings will be needed, but it is recommended that ICHD-3 considers inclusion of these four categories in their appendix.