Continuous Versus Short EEG After Ischemic Stroke: What cEEG Adds for Detecting Abnormalities and Predicting Post-Stroke Epilepsy

OBJECTIVE: The objective of this study was to quantify incremental diagnostic yield and prognostic value of continuous electroencephalography (cEEG; ≥12 hours) versus a 60-minute short electroencephalography (sEEG) in predicting post-stroke epilepsy (PSE) in patients without acute symptomatic seizures.

METHODS: We retrospectively included 283 adults who underwent cEEG within 7 days; sEEG comprised the first 60 minutes of the same recording. EEGs were interpreted using American Clinical Neurophysiology Society (ACNS) terminology by neurophysiologists blinded to outcomes. Within-patient yield was quantified using odds ratios (ORs) with 95% confidence intervals (CIs). PSE were modeled using Fine-Gray competing-risks regression (death as competing event) and reported as subdistribution hazard ratios (sHR). SeLECT-EEG derived from sEEG and cEEG was compared using C-index and net reclassification improvement (NRI).

RESULTS: Over a median follow-up of 41 months (interquartile range [IQR] = 22-64), 41 of 283 patients (14.5%) developed PSE. Compared to sEEG, cEEG increased detection of interictal epileptiform discharges (11 vs 3%, OR = 3.75, 95% CI = 1.75-8.02, p < 0.001) and electrographic seizures (4 vs 0.7%, OR = 6.22, 95% CI = 1.38-28.06, p = 0.01). Lateralized periodic discharges (sHR = 4.50, 95% CI = 2.13-9.51) and electrographic seizures (sHR = 3.63, 95% CI = 1.52-8.63) were the strongest predictors of PSE. The cEEG-derived SeLECT-EEG improved discrimination versus sEEG-derived scoring (ΔC-index 0.055, 95% CI = 0.012-0.101, p = 0.014) and reclassification (NRI = 0.25, 95% CI = 0.07-0.42). Epileptiform activity emerging after the first hour conferred higher 5-year PSE risk than never detected (28 vs 11%, Gray p = 0.006).

INTERPRETATION: The cEEG identifies additional epileptiform abnormalities with prognostic value beyond routine-duration EEG, supporting extension of monitoring in selected cases based on baseline risk and early EEG findings. ANN NEUROL 2026;100:400-415.