Common hippocampal structural and functional changes in migraine.

The hippocampus is classically involved in memory consolidation, spatial navigation and is involved in the stress response. Migraine is an episodic disorder characterized by intermittent attacks with a number of physiological and emotional stressors associated with or provoking each attack. Given that migraine attacks can be viewed as repeated stressors, alterations in hippocampal function and structure may play an important role in migraine pathophysiology. Using high-resolution magnetic resonance imaging, hippocampal morphometric and functional differences (in response to noxious heat stimulation) were compared in age and gender-matched acute episodic migraineurs with high (HF) versus low (LF) frequency of migraine attacks. Morphometric results were compared with age and gender-matched healthy control (HC) cohort. Significant larger bilateral hippocampal volume was found in LF group relative to the HF and HC groups suggestive of an initial adaptive plasticity that may then become dysfunctional with increased frequency. Functional correlates of greater deactivation (LF > HF) in the same hippocampal regions in response to noxious stimulation was also accompanied by overall reduction in functional connectivity of the hippocampus with other brain regions involved in pain processing in the HF group. The results implicate involvement of hippocampus in the pathophysiology of the migraine.