Redefining migraine phases - a suggestion based on clinical, physiological, and functional imaging evidence

Migraine is defined by attacks of headache with a specific length and associated symptoms such as photophobia, phonophobia and nausea. It is long recognized that migraine is more than just the attacks and that migraine should be understood as a cycling brain disorder with at least 4 phases: interictal, preictal, ictal and postictal. However, unlike the pain phase, the other phases are less well defined, which renders studies focusing on these phases susceptible to bias. We herewith review the available clinical, electrophysiological, and neuroimaging data and propose that the preictal phase should be defined as up to 48 hours before the headache attack and the postictal phase as up to 24 hours following the ictal phase. This would allow future studies to specifically investigate these migraine phases and to make study results more comparable.