The alpha-delta ratio as a novel neurophysiological biomarker for early prediction of delayed cerebral ischemia in aneurysmal subarachnoid hemorrhage

Quantitative EEG (qEEG) features, particularly the Alpha/Delta Ratio (ADR), reflect cortical metabolic status and may predict Delayed Cerebral Ischemia (DCI) following aneurysmal subarachnoid hemorrhage (aSAH). This retrospective study included 63 aSAH patients. Early background EEG segments were analyzed to extract the ADR and Asymmetry Index (ASI). We compared their predictive value against the modified Fisher (mFisher) score using multivariate logistic regression and ROC analysis. DCI occurred in 24 (38.1%) patients. In univariate analysis, the DCI group exhibited significantly lower baseline ADR (P < 0.001) and significantly higher ASI (P = 0.022). However, in the multivariate analysis, only a lower ADR emerged as the sole independent predictor of DCI, while both ASI and the mFisher score lost significance. The ADR achieved an AUC of 0.844, significantly outperforming the mFisher score (AUC = 0.613). An ADR cut-off of < 0.14 yielded a sensitivity of 96%, markedly superior to that of mFisher (46%). Decreased ADR is a robust, independent predictor of DCI, offering superior sensitivity compared to radiographic grading. An ADR < 0.14 serves as a critical early warning sign for impending ischemia.