Reproducibility and clinical relevance of quantitative EEG parameters in cerebral ischemia: A basic approach.

Objective To investigate reproducibility and clinical relevance of quantitative EEG parameters in ischemic cerebrovascular disease. Methods EEG was recorded in 31 patients suffering from subacute ischemic cerebrovascular disease. Ten age-matched control subjects were included as a reference group. Intra-recording, intrarater and interrater reproducibility was calculated for standard EEG measures and for a pair wise derived Brain Symmetry Index (pdBSI). Correlations between EEG parameters, clinical status and volume of ischemia on diffusion weighted imaging (DWI) were calculated. Results pdBSI was sensitive to asymmetry in the amplitude and frequency domain in a random white noise model and in a simulated sinusoidal model. Minimal Cronbach alpha for intra-recording, intra- and inter-rater reproducibility ranged between 0.95 and 0.99 for standard spectral parameters and between 0.96 and 0.99 for pdBSI. We found a significant difference in pdBSI between stroke patients and control or TIA (p = 0.0003). pdBSI correlated significantly with NIH stroke scale at admission and DWI volume across different levels of stroke probability (Spearman’s ρ = 0.64–0.70 and 0.79–0.84, respectively, p < 0.00001 for both). Conclusions pdBSI displays high multilevel reproducibility and reliably discriminates between stroke and TIA patients or control subjects, and correlates significantly with clinical and radiological status. Significance Based on this methodological analysis, reliable EEG parameters can be evaluated in a general stroke population for clinically relevant state and outcome measures.