[Electroencephalographic mapping in migraine during the critical and intercritical periods].

Twenty-nine migraineurs underwent spectral analysis and topographic EEG mapping. In a case of an induced attack of classic migraine with a complex aura, posterior-anterior spreading of slow activities and depression of alpha activity contralateral to the neurological signs were the prominent findings. Another patient who developed a spontaneous attack of classic migraine with a visual aura had unilateral reduction of alpha and theta activity. In 19 out of 22 patients recorded during an attack of common migraine the only abnormality was markedly reduced alpha activity over one occipital region, usually on the side of the headache. Sixteen of these had concomitantly reduction of theta activity in the same location. In all patients, except one, restudied at least 7 days after an attack, EEG asymmetries had disappeared. Unilateral EEG changes can thus be detected during attacks of both classic and common migraine. The posterior-anterior spreading of slow activities during an induced attack of classic migraine has temporal and spatial similarities with the "spreading oligemia" (Olesen et al., 1981). Findings in classic migraine with a strictly visual aura, however, are identical to those observed during common migraine, i.e. unilateral reduction of alpha and theta activity. This suggests that common, as classic, migraine is associated with unilateral disturbances of cortical electrogenesis, which might reflect an underlying metabolic abnormality.