Iris Publishers- Open access Journal of Biomedical Engineering & Biotechnology | Comparison of Cholinergic Status with Quantitative EEG in Healthy Subjects and Patients Suspected of Dementia

Authored by Rolf Ekedahl

Introduction: Objective is to evaluate quantitative electroencephalography (qEEG) variables to distinguish healthy subjects from patients who investigated for dementia and, to assess also at follow-up examination if acetylcholinesterase inhibitor (AChEI) treatment or not influenced the qEEG.
Methods: Average value from four EEG epochs obtained with eyes closed (E.Cl.) and eyes open (E.O.), the peak frequency with eyes closed and the Vigilance-index (ratio of E.O./E.Cl. average powers) calculated. A healthy group and a group suspected of having primary dementia compared, and the assumed dementia group evaluated with follow-up qEEG after approximately 12-14 months with or without acetylcholinesterase inhibitor treatment. The statistical analyze (Student`s t-test) p-values compared the healthy individuals against the suspected dementia patients, and at follow-up of AChEI treated against non-treated analyzed with paired p-values.
Result: When the healthy group compared with suspected dementia group at baseline, all variables were altered statistically significant except E.Cl. average power. The Vigilance-index (p-value < 0.001) and average power of E.O. (p-value < 0.001) increased, and the mean peak- frequency (p-value < 0.001) decreased. At the follow-up for the suspected dementia group, the Vigilance-index of the untreated increased significantly (p-value < 0.001) but not for the AChEI treated group. No other statistically significant changes for the other parameters.
Conclusion: The Vigilance-index may be used to assess cholinergic deficits in patients with dementia, also early in the course of the disease and evaluate the effects of AChEI treatment. Also, identify unwanted central cholinergic side-effects of other medication.
Longitudinal studies using electroencephalography (EEG) and follow-up are rare in dementia studies; however, varying effects on EEG parameters reported from existing studies [1-7]. Probably due to the heterogeneity and different stages of the dementia diseases, and also mixed types of dementia, e.g., Alzheimer’s dementia (AD), vascular dementia (VaD), Lewy body dementia (LBD) studied. Interpreting the EEG measurements is also tricky because the procedures used to collect and analyze data are different. The commonly used EEG parameters have assessed changes in the proportion of different frequency bands, average frequency, EEG power, the ratio of low-frequency activity to global and fluctuations in EEG frequency and coherence.
Varying proportions of patients did not display EEG changes at follow-up compared to baseline values [1,3,4,5,8]. Therefore, examinations of other EEG parameters that better reflect the electrophysiological changes in patients with dementia diseases needed for improving the diagnostic precision. Particularly in the early stages of dementia, and to monitor disease progression and evaluate the effects of Acetylcholinesterase inhibitor (AchEI) treatment. One possible way is to try to find methods to measure the cholinergic deficit in patients with primary degenerative dementia, such as AD [9-17]. Which, potentially could lead to an earlier AChEI treatment initiation in the early course of the disease than previous EEG methods [18-28] and other diagnostic measures, but also be used as a biomarker for dementia disease characterized by cholinergic deficiency.

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