Electrophysiological findings in migraine may reflect abnormal synaptic plasticity mechanisms. A narrative review

Background: The cyclical brain disorder of sensory processing accompanying migraine phases lacks an explanatory unified theory. Methods: We searched Pubmed for non-invasive neurophysiological studies on migraine and related conditions using transcranial magnetic stimulation, electroencephalography, visual and somatosensory evoked potentials.We summarized the literature, reviewed methods, and proposed a unified theory for the pathophysiology of electrophysiological abnormalities underlying migraine recurrence. Results: All electrophysiological modalities have determined specific changes in brain dynamics across the different phases of the migraine cycle. Transcranial magnetic stimulation studies show unbalanced recruitment of inhibitory and excitatory circuits, more consistently in aura, which ultimately results in a substantially distorted response to neuromodulation protocols. Electroencephalography investigations highlight a steady pattern of reduced alpha and increased slow rhythms, largely located in posterior brain regions, which tends to normalize closer to the attacks. Finally, nonpainful evoked potentials suggest dysfunctions in habituation mechanisms of sensory cortices that revert during ictal phases. Conclusion: Electrophysiology shows dynamic and recurrent functional alterations within the brainstem-thalamuscortex loop varies continuously and recurrently in migraineurs. Given the central role of these structures in the selection, elaboration, and learning of sensory information, these functional alterations suggest chronic, probably genetically determined dysfunctions of the synaptic short- and long-term learning mechanisms.