The significance of subclinical epileptiform activity after stroke

Early combined functional and structural diagnostic approaches to understand poststroke pathophysiology and related clinical features in acute ischemic stroke have been reported rarely till now despite possibly supplying valuable information. Previous studies of EEG patterns and their predictive value with regard to epilepsy after stroke have been entirely retrospective were unblinded and showed a high degree of variation in EEG interpretation. We therefore present three different new study designs, all of them prospective, standardized, implementing EEG-recording in the early phase of first CT-proven supratentorial infarction, either continous or serial with strict exclusion criteria. Data so far available confirm the hypothesis of an unexpected high percentage of subclinical epileptiform activity, demonstrating SEA in up to 30% of all patients. SEA correlated significantly with extended cortical infarctions, hemispheric syndrome ( vs. lacunar syndrome), severe neurological deficit and short term outcome. Most interstingly, recent animal experiments detected depression-like depolarizations in the penumbra zone resulting in increased cerebral infarct size and localized abnormalities on diffusion-weighted MR imaging, hypothetically correlating with SEA in clinical surface EEG-recordings. Our pilot data emphasize that early systematic EEG - recording allows detection of focal hyperexcitability after stroke and may have practical implications such as antiepileptic treatment.