The EEG findings in extratemporal seizures.

Extratemporal seizures originate from the frontal, central, parietal, occipital, and midline regions of the brain. The scalp EEG can show various types of interictal and ictal discharges consisting of spikes, spike and wave sharp waves, paroxysmal fast activity, or rhythmic activity in the beta, alpha, theta, or delta frequency ranges. The discharges can occur as focal, regional, lateralized, or secondarily generalized discharges. Discharges arising from the frontal region are varied and at times complex. Centro-temporal spikes associated with benign epilepsy of childhood have a characteristic blunt spike and wave appearance. Centro-parietal spikes can occur in children with benign childhood epilepsy or in association with symptomatic epilepsies at any age. Occipital spike discharges have been seen in young children with visual problems, benign occipital epilepsy of childhood, the Sturge-Weber syndrome, and other symptomatic or structural lesions involving the occipital lobe. There may be problems with detection of the source of origin of seizures secondary to the anatomy of the various regions, deep foci, small restricted foci, rapid spread of epileptiform discharges, and contaminating effects of muscle and movement artifact. Depth or intracranial recordings may help in further localization of foci.