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