Increased limbic and brainstem activity during migraine attacks following olfactory stimulation

Abstract

Migraine patients have dysfunctional cortical olfactory processing and very often report hypersensitivity and phobic symptoms to odors during acute headache attacks. However, imaging data of how the brain processes associate migraine symptoms, such as photophobia, phonophobia, or osmophobia, are rare. The present study aimed to explore neuronal processing in response to olfactory stimulation (rose odor) in migraine patients in and outside acute headache attacks. Using event-related fMRI we studied 20 migraine patients and compared behavioral and imaging data with sex- and age-matched healthy controls. Additionally, 13 of the 20 patients were scanned within 6 hours after the onset of a spontaneous migraine attack. Imaging data showed that interictal migraineurs did not differ from control subjects. However, during spontaneous and untreated attacks, migraine patients showed significantly higher blood oxygen level-dependent signal intensities in brain areas including limbic structures (amygdala and insular cortices) and, more specifically, in the rostral pons in response to olfactory stimulation. Increased activity in the rostral part of the pons has previously been specifically linked to the pain of the migraine attack. The present finding suggests that the activity level of this structure can be triggered by olfactory input and thus points to the strong physiologic relationship between the olfactory and the trigemino-nociceptive pathway in the pathophysiology of migraine disease.