Figure 1.

Central vs. peripheral mechanism of migraine. The prevailing theories of migraine initiation include the existence of a peripheral trigger and/or central nervous system changes including oscillations in the sensitivity of descending pain modulatory pathways across the migraine cycle. Such changes in brainstem “tone” are proposed to either prevent or allow an external trigger or basal brainstem activity from evoking activity changes in ascending pathways which are ultimately responsible for the presence of a migraine event.