Abstract TP122: Identifying Predictors of Seizure Recurrence After Nonconvulsive Seizures Recorded on Continuous Electroencephalogram (cEEG) in Ischemic Stroke

Abstract

INTRODUCTION: Seizures are well-recognized complications of ischemic strokes (IS). The risk of subsequent development of epilepsy has been shown to be 2-4% in acute IS and much higher in remote IS. However, the risk of epilepsy in IS who have nonconvulsive seizures on cEEG is not well characterized. We present here a five-year retrospective study of IS patients who have nonconvulsive seizures on cEEG identifying risk factors for the development of epilepsy. METHODS: We retrospectively reviewed prospectively collected cEEG and clinical data on consecutive patients monitored from January 1, 2007, to December 31, 2011. We identified those patients with cEEG seizures that were secondary to either acute (<30 days) or remote (>30 days) ischemic stroke (IS; n=109) and then included in this study only those patients with follow-up encounters. Statistical analyses were performed with JMP 9.0. RESULTS: Sixty-five (41.5% acute IS, 58.5% remote IS) patients met inclusion criteria for this study. All patients were discharged on at least one antiepileptic. Nineteen (29.2%) patients were found to have seizure recurrence (i.e., epilepsy) with 84.2% being remote IS (p=0.0116). Periodic lateralized epileptiform discharges (PLEDs) were seen on cEEG in 21.5% (22.2% acute IS, 21.1% remote IS). 15.8% with PLEDs on initial cEEG developed epilepsy (p=0.74). 33.3% of patients classified as stupor/coma at the time of nonconvulsive seizures were found to have seizure recurrence compared to 24.1% of patients classified as awake/lethargy (p=0.5841). On follow up EEG (mean (SEM) 384.4 (59.1) days), the finding of sharp wave/spike (12.1%) significantly correlated with seizure recurrence (p=0.0175). DISCUSSION: This retrospective study found that patients with remote IS are at a higher risk of developing epilepsy when nonconvulsive seizures are recorded on cEEG in the hospital. Additionally, the finding of sharp waves on follow-up routine EEG further identifies those at risk for recurrence. This study highlights the usefulness of cEEG in patients in patients with acute or remote strokes and provides guidance on utility of follow-up EEG.