Quantitative EEG in post-stroke delirium: Spectral and Functional Connectivity Analyses in a Case-Control Study

Delirium is a common complication of ischemic stroke (IS). Previous quantitative EEG (qEEG) studies have linked delirium to increased delta and theta power and reduced alpha band functional connectivity. Most excluded patients with structural brain lesions, limiting extrapolation to post-stroke delirium (PSD). This study aims to compare qEEG measures in IS patients with and without PSD. IS patients hospitalized within 24 h after symptom onset were included. The presence of delirium was evaluated by two raters based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria, using a retrospective chart review method. When no consensus was reached, a third rater was consulted. PSD cases were matched to non-PSD patients based on stroke location, severity (NIHSS) and age. Spectral and connectivity EEG results were compared using Mann-Whitney U tests. Relative delta power was significantly higher in PSD patients (n = 40; median(M) = 0,541; IQR = 0,404-0,631) compared to non-PSD patients (n = 40; M = 0,451; IQR = 0,358-0,534; p-value 0,022; r = 0.256). In the alpha band, functional connectivity strength was significantly lower in PSD patients based on phase lag index (PLI M = 0,130 (IQR = 0,118-0,155) versus M = 0,149 (IQR = 0,120-0,174); p-value 0,044; r = 0.157) and amplitude envelope correlation (AEC-c M = 0,517 (IQR = 0,506-0,535) versus M = 0,526 (IQR = 0,514-0,544); p-value 0,029; r = 0.244). PSD is associated with increased delta power and reduced alpha connectivity. Results align with prior qEEG studies in delirium due to other etiologies, suggesting common pathophysiological mechanisms.