Resting-state EEG changes associated with cognitive decline in Parkinson's disease: a systematic review

Cognitive decline is a common and disabling feature of Parkinson's disease (PD), frequently progressing from mild cognitive impairment to Parkinson's disease dementia. Due to substantial heterogeneity in PD phenotypes, current research is increasingly focused on identifying robust biomarkers to predict which individuals are at higher risk of cognitive deterioration relative to those likely to exhibit cognitive stability. Electroencephalography (EEG), a non-invasive and cost-efficient method for measuring neural activity, has shown potential in detecting early electrophysiological alterations associated with cognitive decline in PD. This review aims to summarise recent findings on the utility of resting-state quantitative EEG measures as candidate biomarkers for cognitive trajectory in PD. Relevant studies from over the last 10 years were retrieved through PubMed and Scopus, resulting in the inclusion and evaluation of 67 articles. Distinct EEG features, identified using various analytic approaches, were found to discriminate PD patients across different cognitive stages, as well as from those cognitively unimpaired and healthy controls. We suggest that EEG surrogate markers may be a valuable tool in conjunction with clinical and genetic variables to help early detection and monitoring, as well as development of personalised interventions for cognitive impairment in PD.