B-3. Electroencephalography and seizures learned from ictal recording

Publication date: May 2018
Source:Clinical Neurophysiology, Volume 129, Issue 5
Author(s): Masaki Iwasaki, Naoki Ikegaya, Yuiko Kimura, Yuu Kaneko
Experience on ictal video electroencephalography (EEG) recording enriches knowledge on EEG and seizures. Following five fundamentals are important for correct interpretation of EEG during focal epileptic seizures.Epileptic seizures never happen without EEG changes.Epileptic seizure propagates.EEG changes are not necessarily visible.EEG changes occur as a remote effect.EEG seizure explains clinical symptoms.Focal epileptic seizure starts with several patterns such as low voltage fast activity or repetitive spikes, followed by ictal rhythm that evolves spatially from focal to diffuse area, and temporally from low amplitude fast to high amplitude slow waves. The seizure propagation can occur very rapidly. For the sensitivity of EEG depends on the distance from source to electrode, EEG seizure may only appear after seizure activity involves adequately large area of cortex. The seizure activity limited to the deep area such as mesial temporal region will not appear in scalp EEG. Slow rhythmic activity can be induced in the remote cortex as an inhibitory effect of focal seizure, so that diffuse delta rhythm at the beginning of seizure may not localize the seizure onset zone. Epileptogenic zone is estimated by correlating supposed EEG seizure localization and clinical symptoms.



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