Brain Oscillations and Migraine
The rhythmic oscillations embedded in the spontaneous or evoked electroencephalographic (EEG) activity are closely related to the subtle cognitive processes of the brain. This review is aimed to provide a comprehensive overview of the studies investigating brain oscillations across various frequency ranges in migraine, using EEG and evoked potentials.
The analysis of quantitative EEG in migraine provided inconclusive results, especially the amplitude of alpha waves. Alpha phase hyper-synchronization during flash visual stimulation has been consistently reported and helps in the neurophysiological discrimination between migraine with and without aura. The strength of functional connectivity between the alpha rhythmic activity from the cuneus to the temporal pole and the anterior cingulate cortex fluctuates depending on the distance from the last attack. The analysis of the high- (beta/gamma bands) and very high-frequency (around 600 Hz) oscillations (HFOs) underlying the common visual and somatosensory evoked potentials discloses a reduced thalamocortical activity during the pain-free phase of migraine. The amplitude of these HFOs may contribute to the determination of migraine clinical features.
Overall, the analysis of the oscillatory neural activity in the migraineur brain provided evidence in favor of a thalamocortical dysrhythmia, probably due to a thalamic deafferentation from the brainstem monoaminergic tonic activity. Supplementary studies of HFOs are needed to compare the recordings with other primary headaches, such as tension-type or cluster headache, in order to verify the specificity of these findings for migraine.