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 rho=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.