Objective: To explore the utility of the quantitative electroencephalogram (EEG) as a potential biomarker of cognitive status in patients with Parkinson’s disease (PD).

Background: While predominantly a motor disease, non-motor symptoms in PD, such as cognitive impairment, may impact the quality of life even more than the motor disability itself. Specifically, cognitive impairment may reduce the life expectancy of patients by up to 5 years. Recently, neurophysiological measures, such as quantitative EEG, have been proposed as reliable measures of cognitive decline in PD. In this study we explored the association between EEG power and connectivity, and cognitive screening tests in PD.

Method: We included 30 patients diagnosed with PD who attended the National Institute of Neurology and Neurosurgery in Mexico City. Twelve healthy participants similar in age and education were recruited as a control group. The PD group was assessed under dopaminergic treatment (ON status). The used cognitive tests were the Montreal Cognitive Assessment (MoCA) and the Minimental State Examination (MMSE). We recorded a resting state (closed eyes) EEG with 64 channels. Quantitative measures included relative power and phase-locking value from frontal and posterior regions in the ranges of delta (1-3 Hz), theta (4-7 Hz), alpha (8-14 Hz), and beta (15-30 Hz).

Results: A lower overall mean frequency was observed in the PD group compared to the control group (p<0.001). The PD group showed increases of power for low frequencies, especially in frontal regions (p<0.001), for delta (p=0.05) and theta bands (p=0.05), as well as a decrease in beta in all regions (p=0.03). Within the PD group, both MoCA and MMSE showed significant associations with the years of evolution (r=-0.45, p=0.015 and r=-0.43, p=0.02) and with the power of theta and beta bands exclusively in posterior regions (theta: r<-0.4, p<0.03, beta: r>0.45, p<0.01). Also, increased phase-locked theta in frontal regions was inversely associated with MoCA and MMSE scores (r<-0.4, p<0.05).

Conclusion: PD shows increased EEG low frequencies, especially in frontal regions, and general decreased beta activity. Cognitive screening tests are sensitive to theta amplitude changes in posterior regions and increased connectivity within frontal areas. Our results provide evidence that basic neuropsychological testing may reflect subtle neurophysiological changes in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/quantitative-eeg-measures-reflect-general-cognitive-status-in-parkinsons-disease/