Lesion-directed quantitative EEG after reperfusion therapy is associated with malignant cerebral edema and functional outcomes in acute ischemic stroke: a prospective exploratory cohort study

Background Ischemic stroke causes electrophysiological slowing within minutes which may precede detectable structural changes, making electroencephalography (EEG) a sensitive bedside marker of tissue at risk. Prior quantitative EEG (qEEG) studies often averaged bilateral or frontal activity, focused on thrombectomy, and were recorded at 24 h. We tested whether a lesion-directed alpha-to-delta ratio (lesion-ADR) within 72 h after reperfusion is associated with malignant cerebral edema (MCE) and functional outcomes. Methods In a prospective single-center cohort of anterior-circulation ischemic stroke treated with intravenous alteplase (IV-rtPA), endovascular thrombectomy (EVT), or both, a 7-min EEG was obtained ≤72 h after reperfusion. Lesion-ADR was defined as the mean ADR of ipsilesional electrodes; the reperfusion-to-EEG interval (ΔT) was recorded. The primary outcome was MCE (midline shift ≥5 mm and/or decompressive hemicraniectomy). Secondary outcomes were favorable functional outcomes at discharge and 90 days (modified Rankin Scale [mRS] 0–2). Model discrimination was assessed using ROC analysis and AUC with bootstrap internal validation. Adjusted associations were assessed using parsimonious Firth penalized logistic regression models. Results Forty-nine patients were included. For MCE, the combined lesion-ADR + ΔT model achieved an apparent AUC of 0.888 (95% CI 0.765–0.960); bootstrap internal validation yielded an optimism-corrected AUC of 0.889. For discharge independence (mRS ≤ 2; n = 9), the ADR-only model showed an apparent AUC of 0.899. Lesion-ADR remained associated with favorable outcome after separate adjustment for admission NIHSS (OR 1.438 per 0.1-unit increase; p = 0.009) and reperfusion treatment modality (OR 1.367; p = 0.022). For 90-day independence ( n = 13), the ADR-only AUC was 0.759 (95% CI 0.615–0.869) and the ADR-only model showed moderate discrimination for 90-day functional independence. The association with 90-day outcome was attenuated after accounting for admission NIHSS (OR 1.245 per 0.1-unit increase; p = 0.088). Conclusion A brief lesion-directed ADR obtained within 72 h after reperfusion was associated with functional outcomes, while its combination with EEG timing showed encouraging discrimination for MCE in this cohort. These exploratory findings suggest lesion-directed qEEG may serve as a potential adjunctive biomarker after reperfusion therapy and warrant validation in larger cohorts.