Frontal Delta Decreasing and Occipital Ictal Alpha Increasing Associated With Migraine in Preictal and Ictal Phases

Subtle changes across different migraine phases in resting electroencephalography (EEG) studies are commonly observed in migraine patients and have the potential to aid in clinical diagnosis. However, exploring the dynamic changes of brain activity across the migraine phases are extremely rare and difficult to analyze. This study aimed to longitudinally investigate the EEG spectral characteristics across the migraine phases in a paired EEG study. Ninety-five episodic migraine (EM) patients without aura and 59 control subjects participated in the study, and the resting close-eye EEG signals were recorded from their frontal and occipital regions. The EEG signals, recorded using a wireless EEG device with three dry spring-loaded electrodes, were retrospectively divided based on the migraine phases and paired after being transformed into wavelet spectra, resulting in 53 interictal-preictal pairs and 17 interictal-ictal pairs. The delta band power of the migraine patients in the frontal region showed that the preictal power, which was comparable to the control subjects, was significantly lower than that of the interictal ( $\rho \lt 0.01$ ) and ictal powers. Alternatively, the alpha band power in the occipital region exhibited significantly ( $\rho \lt 0.01$ ) higher ictal power compared to the interictal phase but exhibited no significance with preictal condition. The results further showed that 32 out of 46 pairs (69.5%) displayed reduction of frontal delta power from interictal to preictal phase and 11 out of 14 pairs (78.5%) produced increased occipital alpha power from interictal to ictal phase. Further, the low-frequency valley (LFV) power ratio from interictal to preictal phase in frontal region showed a negative correlation with the average headache intensity (AHI) and the domain alpha peak (DAP) power ratio from interictal to ictal phase in occipital region showed a positive correlation with the current headache intensity (CHI). In this longitudinal paired study, our findings suggested that the resting EEG activity efficiently extracted the phase specific spectral characteristics across the migraine patients and obtained significant correlation with the pain intensity levels. Overall, the decreased frontal delta power in the preictal phase and the increased occipital alpha power in the ictal phase may be considered as the potential markers to predict the incoming migraine attack and to quantitatively assess the headache intensity.