Interpreting Intraoperative EEG: Beyond Indices to the Essential Role of Raw EEG and Density Spectral Array

Intraoperative electroencephalography (EEG) is increasingly used to monitor the depth of anesthesia and a range of other perioperative indications. While processed EEG indices offer a convenient numerical representation, exclusive reliance on these values can obscure clinically significant findings. Discordance between the numerical index and the raw EEG or density spectral array (DSA) may arise due to artifacts, patient-specific neurophysiology, or pharmacologic effects. This article highlights common sources of such discordance, illustrated through clinical examples, and emphasizes the importance of integrating raw EEG interpretation and DSA analysis into routine intraoperative monitoring.