The alpha rhythm of 18 patients with classical migraine (migraine with aura) was studied by EEG spectrum analysis for evidence of neural abnormalities during the asymptomatic period. The temporal relationship of the findings to attacks was studied by serial records in 11 cases. Increased frequency dispersion and frequency asymmetries of the alpha rhythm were found. The records were, however, mostly normal when separated from attacks by at least 10 asymptomatic days. The abnormalities increased significantly before the onset of prodromal symptoms and clearly outlasted the headache phase. The results give evidence of a fluctuating asymmetric neural disorder in classical migraine.
The amplitude of visual evoked potentials (VEPs) for flickering light has been reported to be increased in migraine. In the present study, we have examined whether the VEPs are attenuated when the clinical state of the patient improves during a double-blind experiment with propranolol and femoxetine. VEPs for sinusoidally-modulated light were measured by spectral analysis, and an index depicting the visual reaction type was calculated. The group mean VEP index closely followed the group mean attack frequency, but individual variance was considerable. The changes were most evident in VEPs elicited by stimuli of about 20 Hz. During the treatments, the VEP and headache were also significantly correlated among subjects. The results suggest a close relationship between the enlarged VEPs and the headache mechanisms.
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