Neurophysiological evaluation of cortical excitability in migraine: A review of the literature

Introduction. - Neurophysiological studies point to altered cortical neuronal excitability in migraine patients. State of art. - Between attacks, migraine brain seems to be "hyperresponsive" to repetitive stimuli, as suggested by evoked potential studies that show a lack of habituation to sensory stimuli. Transcranial magnetic stimulation suggests an impairment of intracortical inhibitory circuits in migraine, especially in migraine with aura. Controversial results are obtained in migraineurs without aura. Repetitive transcranial magnetic stimulation also shows in migraine with aura a paradoxical enhancement of intracortical facilitation by low frequency stimulation and greater increased facilitatory mechanisms by high-frequency stimulation. Importantly, cortical excitability level fluctuates over time in relation to the migraine cycle. The interictal lack of habituation to sensory stimuli normalizes before and during a migraine attack. Changes of cortical excitability consistent with the theory of cortical spreading depression are also observed during migraine aura with magnetoencephalography. Perspectives. - The exact role of cortical excitability changes in migraine pathophysiology and possibly in chronic migraine is still unknown. Further studies are also necessary to clarify the role of migraine preventive drugs on brain excitability. Conclusions. - In this review, the results of neurophysiological studies conducted in migraine patients will be described and the associated pathophysiological hypotheses will be discussed. (c) 2013 Elsevier Masson SAS. All rights reserved.