The Effect of Cerebrovascular Damage on BEAM EEG Event-Related Potentials in Mild Cognitive Impairment and Alzheimer’s Disease

Background: Mild cognitive impairment (MCI) is a disease state in which memory, attention, learning, and similar capabilities are decreased below a patient’s baseline level. It is often a pre-dementia stage – specifically Alzheimer’s Disease (AD) – and has been shown to be associated with a variety of comorbid conditions, of which one of the most prominent is hypertension. Biomarker-Based Electrophysiology for Advanced Brain Monitoring (BEAM) is an electroencephalography-based tool used to record event-related potentials (ERP) as patients undergo various tasks. A previous study has demonstrated the potential effect of hypertension to influence these ERPs in neurodegenerative disease patients when compared to non-hypertensive controls, but it is unclear how cerebrovascular disease in general may influence them, which this study aims to address.

Methods: This was a retrospective chart review of Hawaii Pacific Neuroscience patients with a diagnosis of MCI or Alzheimer’s Disease who underwent BEAM testing. Fazekas and Global Cortical Atrophy (GCA) scores were collected from MRI findings as measures of cerebrovascular and neurodegenerative disease burden, respectively. Patients were excluded if MRI findings were incomplete or if there were at least two years between BEAM testing and MRI. Linear regression models were used to evaluate the association between Fazekas score and individual BEAM ERPs from Resting State and Auditory Oddball testing domains, with GCA score, age, and sex included as covariates. p-values were then adjusted using the Benjamini–Hochberg False Discovery Rate (FDR), with statistical significance accepted for FDR-adjusted p-value < 0.05.

Results: A total of 254 patients were included in the final analysis. The mean age at time of BEAM testing was 69.3 ± 11.8 years, and 57.1% of patients were female. Higher Fazekas scores were associated with increased Eyes Open Individualized Theta (β = 0.03, FDR-adjusted p = 0.002) and Eyes Closed Individualized Theta (β = 0.027, FDR-adjusted p = 0.026) in the Resting State EEG domain.

Conclusion: The individualized theta ERP generated in the resting state during EEG testing appears to be influenced by the presence of cerebrovascular damage independent of cortical atrophy, with worsening degrees of cerebrovascular damage corresponding to greater values of theta. This demonstrates that individualized theta may be an effective EEG biomarker for tracking the progression of cerebrovascular damage without the need for more extensive imaging modalities such as MRI. The results also demonstrated no significant effect of Fazekas score on other biomarkers, indicating that BEAM EEG may still be valid and applicable to neurodegenerative disease patients with varying degrees of cerebrovascular disease burden.