EEG Patterns of Grand Mal Seizures Occurring Under Different Recording Conditions

Abstract

SUMMARYThirty‐five EEG patterns of grand mal seizures recorded under some conditions such as awake‐rest, sleep activation, beme‐gride activation and intermittent photic stimulation were studied in 31 epileptics and four non‐epileptics.Preictal EEG's were generally variable in comparison with ictal EEG's. It was not till 10 sec before seizures that the incidence of seizure discharges changed in most all cases, of which six increased and four decreased.A paroxysmal extreme varied EEG abnormality often continued for several to several ten sec immediately before a tonic phase, associated with some clinical symptoms. EEG patterns of the “preconvulsive phase” were divided into six types with different clinical features. In most all cases of bamegride activation, poly‐spike and wave discharges preceded on seizure activities and some of them related with absence or psychomotor epilepsies. In all cases of sleep activation and photic stimulation, high voltage slow bursts or poly spikes preceded. Seizure patterns recorded at awake‐rest were indefinite. A few cases didn't show any preconvulsive EEG changes, and were closely related with grand mal epilepsies.While the grand mal seizure during sleep had a long tonic‐clonic convulsive phase and a short pre‐ and postconvulsive phase, that induced by bemegride activation showed the opposite findings. The grand mal seizure at awake‐rest had the middle tendency between the two.The differences among the effects of various recording conditions on seizure patterns present some suggestions as to the patho‐physiological mechanism of epileptic seizures.