EEG patterns and epileptic seizures in acute phase stroke

The rate of early post-stroke epileptic seizures ranges from 2 to 33%. This wide range is likely due to differences in study design, patient selection and type of neurophysiological monitoring. Electroencephalography (EEG), which is not used in the routine work-up of acute stroke, is the best neurodiagnostic technique for detecting epileptic activity, especially in patients with non-convulsive post-stroke epileptic activity. The aim of this study was to analyze patterns on EEGs performed within 24 h of stroke onset, and to investigate correlations between these patterns and the occurrence of early epileptic seizures and status epilepticus (SE), vascular risk factors, stroke subtypes and short-term outcome.

We prospectively studied 232 patients (mean age 71 ± 12 years; 177 ischemic strokes and 55 hemorrhagic). EEG recording was performed within 24 h from hospitalization. The follow-up lasted 1 week.

Fifteen patients (6.5%) had early seizures within 24 h; 10 of these patients had focal SE with or without secondary generalization. EEG revealed sporadic epileptiform focal abnormalities in 10% and periodic lateralized epileptiform discharges (PLEDs) in 6%. SE was recorded in 71.4% of patients with PLEDs. At the multivariate analysis, only early epileptic manifestations (p < 0.001) were independently associated with PLEDs.

Our study confirms that seizures are not frequent in the early phase of acute stroke and occur prevalently as focal SE at onset. EEG may help to detect specific patterns, such as PLEDs, that are closely related to early seizures. EEG monitoring should be performed in order to detect purely electrographic seizures.