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Background: Accumulating data emphasizes the importance of olfaction in migraine pathophysiology. However, there are only a few studies evaluating how the migraine brain processes olfactory stimulation, and virtually no studies comparing patients with and without aura in this context. Methods: This cross-sectional study recorded event-related potentials from 64 electrodes during a pure olfactory or pure trigeminal stimulus in females with episodic migraine with aura (n = 13) and without aura (n = 15), to characterize the central nervous processing of these intranasal stimuli. Patients were tested in interictal state only. Data were analyzed in the time domain and in the time–frequency domain. Source reconstruction analysis was also performed. Results: Patients with aura had higher event-related potentials amplitudes for left-sided trigeminal and left-sided olfactory stimulations, and higher neural activity for right-sided trigeminal stimulation in brain areas related to trigeminal and visual processing. Following olfactory stimulations patients with aura displayed decreased neural activity in secondary olfactory structures compared to patients without aura. Oscillations in the low frequency bands (< 8 Hz) differed between patient groups. Conclusions: Altogether this may reflect hypersensitivity to nociceptive stimuli in patients with aura relative to patients without aura. Patients with aura have a bigger deficit in engaging secondary olfactory-related structures, possibly leading to distorted attention and judgements towards odors. The cerebral overlap between trigeminal nociception and olfaction might explain these deficits. [ABSTRACT FROM AUTHOR]

Background: Sensitization to sensory stimuli is an essential feature of migraine attacks. The relationship between the clinical course of migraine and increased sensitivity to olfactory stimuli has been little studied so far. Methods: We analyzed the frequency and quality of osmophobia depending on the phase of migraine in patients with episodic and chronic migraine treated in an tertiary headache center with regard to gender, age, medical history and migraine disability assessment score (MIDAS). Standardized diagnostic questions were used for the assessment of osmophobia. Results: In our cross-sectional investigation (n = 113), 38.1% of the patients showed an increased preictal hypersensitivity to odors, whereas 61.9% described ictal and 31.9% interictal hypersensitivity to odors, odor-triggered migraine was described in 30.1%. Median migraine disease duration has been statistically significantly longer in patients who suffered from interictal hypersensitivity to odors (28.5 years vs. 20 years; p = 0.012). There was a significant correlation between interictal hypersensitivity and higher age (54.50 vs. 45; p = 0.015). Patients with higher migraine disability in MIDAS experienced more frequently preictal and interictal olfactory sensitization and odor triggered migraine attacks. Conclusions: In patients with longer migraine disease duration and higher migraine-related impairment, osmophobia was more frequently observed. These results might support the hypothesis of increasing sensitization with increasing burden of migraine. [ABSTRACT FROM AUTHOR]

Purpose: Olfactory adaptation is a peripheral (at the epithelium level) or a central (at the brain level) mechanism resulting from repeated or prolonged odorous exposure that can induce a perceptual decrease. The aim of this study was to assess whether a peripheral adaptation occurs when an odor is repeated ten times. Moreover, the specificity of the peripheral adaptation to the nature of the odorant was investigated. Methods: Four odorants (eugenol, manzanate, ISO E Super and phenylethanol) were presented using precisely controlled air-dilution olfactometry. They differed in terms of their physicochemical properties. Electrophysiological recordings were made at the level of the olfactory mucosa, the so-called electro-olfactogram (EOG). Thirty-five right-handed participants were recruited. Results: Sixty-nine percent of the participants presented at least one EOG, whatever the odor condition. The EOG amplitude did not significantly decrease over 10 repeated exposures to any odorant. The intensity ratings tended to decrease over stimulations for manzanate, PEA, and eugenol. No correlation was found between the mean EOG amplitudes and the mean intensity ratings. However, the presence of EOG amplitude decreases over stimulations for few subjects suggests that peripheral adaptation might exist. Conclusion: Overall, our results did not establish a clear peripheral adaptation measured with EOG but indicate the eventuality of such an effect. [ABSTRACT FROM AUTHOR]