How the brain anticipates an attack: a study of neurophysiological periodicity in migraine.

We investigated cortical excitability and the pattern of arousal in migraine patients using contingent negative variation (CNV) and EEG power spectrum analysis performed before and after a migraine attack. Twenty females suffering from migraine without aura and 12 healthy controls were enrolled in the study. In the group of patients, the CNV, EEG power spectrum and hemispheric asymmetry analyses were performed 1-4 days before the first day of an attack and 4 days following the last day with migraine. The recordings in healthy subjects were carried out on a day chosen by the participants. The comparisons were made using non-parametric procedures. After an attack no difference was found between patients and controls in EEG power spectrum, hemispheric asymmetry or CNV components (with the exception of the beta 1 power, which was more pronounced in patients). Before an attack, however, a significant increase in the power of delta and theta frequency bands, in the alpha asymmetry, and in early CNV amplitude were observed. The patients differed from controls both in the extent of cortical excitability and in the arousal pattern found. In such a way migraine is characterized by periodic CNV and EEG power spectrum changes during the pain-free interval. The abnormalities in cortical excitability and arousal were only observed before an attack, and could be used to predict the next migraine episode. We assume that these changes reflect the increased susceptibility of the migrainous brain to precipitating factors and the neurophysiological readiness to generate an attack. The time duration since the last attack must be taken into account when performing studies in the field of migraine research.