PERIODIC LATERALIZED EPILEPTIFORM DISCHARGES - A CRITICAL-REVIEW

It is the purpose of this review to critically consider and organize t he literature dealing with the ephemeral electroencephalographic (EEG) pattern periodic lateralized epileptiform discharges (PLEDs). Althoug h the retrospective nature of these studies limits their ability to di scuss accurately the clinical and pathophysiological aspects of this E EG entity, the available data strongly emphasize stroke as the dominan t etiology and its high association with seizures. Recent evidence, pa rticularly from functional neuroimaging studies, strongly suggests tha t PLEDs might reflect a key pattern for focal hyperexcitability in the penumbra zone of ischemic stroke. The authors prefer to consider PLED s as an EEG signature of a dynamic pathophysiological state in which u nstable neurobiological processes create an ictal-interictal continuum , with the nature of the underlying neuronal injury, the patient's pre existing propensity to have seizures, and the co-existence of any acut e metabolic derangements all contributing to whether seizures occur or not. This review underlines the need for further sophisticated prospe ctive controlled studies implementing early continuous EEG monitoring in order to contribute to an understanding of the incidence, dynamics, and relevance of this pattern.