The EEG Findings in Extratemporal Seizures

Abstract

Summary: 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 β, α, θ, or δ 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.

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“…One of the victims was a male subject who at the time of the attack presented severe disturbance of consciousness, developed convulsions, and required assisted ventilation. At a 1-year follow-up examination, sharp wave complexes, which are consistent with epileptiform activity (Westmoreland, 1998), were present in the EEG of this victim. Two other victims were women who at the time of the attack presented no convulsions, needed no artificial ventilation, and had only mild disturbance of consciousness.…”

Frontal Lobe Seizures

“…Those abnormalities were restricted to one frontal lobe, although inter-ictal EEG abnormalities can be diffuse and bilateral in frontal lobe seizures. Epileptiform inter-ictal discharges may occur in various multilobar locations [7,9,41] or not be accessible to surface EEG recording, as in seizures originating in the medial frontal cortex [42]. In a series of 11 patients with seizure originating in the supplementary motor area, only one patient had inter-ictal EEG abnormalities [24].…”

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“…However structural lesions are associated with zones of epileptogenesis in neighboring and remote areas of the brain [1]. The detection of the epileptogenic zone solely through scalp EEG recordings may be problematic due to the complex anatomy of the various regions, deep or restricted foci, rapid propagation or contamination from muscle and movement artifacts [2]. Therefore, intra-or extraoperative subdural recordings may be required for further localization.…”