Intracranial EEG for Detecting Epileptic Activity in Acute Brain Injury: A Systematic Review and Meta-analysis

Intracranial electroencephalography (iEEG) has been increasingly explored as part of multimodal neuromonitoring in acute brain injury, yet its diagnostic benefit compared with continuous surface EEG (suEEG) remains uncertain. We have performed a meta-analysis to quantify seizure and rhythmic and periodic pattern detection rates and concordance with suEEG. Secondary objectives were the assessment of correlations with brain injury, safety, and techniques. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, PubMed, Scopus, and Embase were searched for studies reporting iEEG monitoring in adults with acute brain injury. Epileptic patterns were harmonized to the American Clinical Neurophysiology Society Standardized EEG Nomenclature for Critically Ill Patients (ACNS) 2021 terminology, classifying events as seizures/status epilepticus (SZ/SE) or rhythmic and periodic/ictal-interictal continuum patterns (RPP/IIC). Risk of bias was assessed using the Newcastle-Ottawa scale and custom bias domains. Random-effects meta-analyses were conducted for (i) pooled proportions and (ii) pooled paired within-patient comparisons. Twelve cohorts (n = 864 participants) with aneurysmal subarachnoid hemorrhage (n = 343), traumatic brain injury (n = 351), and mixed etiologies (n = 170) were included. Six studies provided paired iEEG-suEEG data (n = 273). Techniques were based on a strip or depth electrode. No severe adverse events were reported. Pooled iEEG versus suEEG incidence rates were respectively: 26% vs. 15% for SZ/SE, 47% vs. 34% for RPP/IIC, and 57% vs. 37% for clinically relevant epileptic activity. Pooled paired analysis demonstrated that iEEG additionally detected SZ/SE in 16.5% of patients [pooled McNemar odds ratio (OR) 3.46 (0.51-23.6); I² = 63%; p = 0.158] and RPP/IIC in 26% [pooled OR 4.25 (0.19-96.1); I² = 73%; p = 0.236], while suEEG was negative. Sensitivity analyses for high-risk studies or cohort overlap did not alter the results. Invasive EEG monitoring substantially increased the detection of seizures and RPP/IIC patterns compared with suEEG alone in patients with acute brain injury, serving as a promising monitoring adjunct.