Electroencephalography (EEG) and Quantitative EEG for Acute Stroke Triage and Post-Reperfusion Monitoring: A Systematic Review.

Introduction: Electroencephalography and quantitative EEG are candidate functional biomarkers that may complement clinical examination and imaging for acute ischemic stroke triage and post-reperfusion monitoring. This review aimed to evaluate the value of electroencephalography (EEG) and quantitative EEG (QEEG) for acute stroke triage and post-reperfusion monitoring. Methods: A systematic search was performed in PubMed, Embase, Scopus, and Web of Science on 4 February 2026, with supplementary backward and forward citation tracking. Eligible studies evaluated EEG, QEEG, processed EEG, visual EEG grading, or EEG-derived physiological markers for acute stroke/transient ischemic attack (TIA) classification, large-vessel occlusion (LVO)/medium-vessel occlusion (MeVO) detection, lesion-related classification, stroke control/severity classification, or post-endovascular treatment/mechanical thrombectomy (EVT/MT) monitoring. Diagnostic components were interpreted in line with Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 and PRISMA for diagnostic test accuracy (PRISMA-DTA) principles. Risk of bias was assessed using Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 for diagnostic/classification evidence and Quality in Prognostic Studies (QUIPS)-oriented criteria for post-EVT/MT monitoring studies. Results: From 4,796 database records, 3,179 unique records were screened, 51 full texts were assessed, and 15 study records were retained: seven diagnostic/classification studies and eight post-EVT/MT monitoring studies. Acute triage evidence suggested candidate value for EEG/QEEG in acute stroke/TIA or LVO/MeVO identification, with promising individual-study signals for slow-to-fast ratios, hemispheric asymmetry/ pairwise-derived brain symmetry index (pdBSI), relative alpha/theta power, and clinical-plus-EEG models. However, devices, settings, target conditions, thresholds, and validation status varied, and no diagnostic domain was poolable. No diagnostic meta-analysis was performed because target conditions, thresholds, reference standards, EEG systems, and intended-use settings were too heterogeneous. Post-EVT/MT monitoring studies suggested candidate value for QEEG slowing/frontal delta alpha ratio (DAR), relative alpha loss, visual EEG grading, Non-Convulsive Status Epilepticus (NCSE) detection, bispectral index (BIS)/near-infrared spectroscopy (NIRS), and EEG-transcranial Doppler (TCD) neurovascular coupling (NVC) in relation to early neurological deterioration (END), edema, seizure-related complications, infarct growth, or functional outcome. Certainty was very low for diagnostic domains and low for post-EVT/MT monitoring. Conclusions: EEG/QEEG is a promising but still investigational adjunct for acute ischemic stroke triage and post-reperfusion monitoring. Current evidence does not support a universal diagnostic threshold, pooled diagnostic accuracy estimate, or stand-alone clinical implementation. Larger intended-use validation studies with complete diagnostic accuracy reporting and externally validated thresholds are required.