Neuroimaging and Neuropsychological Performance in Parkinson's Disease Patients with Mild Cognitive Impairment: A Systematic Review

Introduction: One of the most common non motor symptoms of Parkinson's disease (PD) is cognitive decline. Scientific evidence has demonstrated that patients with PD experience rapid cognitive decline in multiple cognitive domains, specifically executive functions, attention, visuospatial, language and memory. However, the extent of cognitive decline with its correlation to brain regions on neuroimaging have not been reviewed extensively in the literature.

Objective: The objective of this review is to summarize the existing literature that explores cognitive performance in patients with PD with mild cognitive impairment (MCI) using different neuroimaging techniques.

Methods: A comprehensive search was conducted on PubMed and Web of Science databases. This review is focused on articles that explored neuroimaging and neuropsychological performance in patients with Parkinson’s disease. We screened articles and excluded those that did not fit the criteria of this study, and a total of 13 articles have met the criteria.

Results: Overall, PD-MCI patients experienced more cognitive decline than PD patients without MCI. Global cognitive ability was associated with frontal lobe, basal ganglia, para-hippocampal gyrus, occipital lobe, and the cerebellum. In addition, some specific cognitive domains were associated with specific brain regions. Attention and executive functions were associated with insula network and the parietal and frontal regions. Learning and memory were associated with grey matter atrophy and right cingulate gyrus and the limbic lobe. Language was associated with frontal cortex, precuneus, and anterior cingulate gyrus. Visuospatial ability was associated with Salience network (SN) and White Matter Hyperintensity (WMH).

Conclusion: This review of the literature showed that PD-MCI patients display different cognitive impairment as well as different neuroanatomical changes when compared to PD-Normal Cognition (NC). These findings may suggest that cognitive impairment in PD-MCI patients require different clinical treatment and care. This review also can have diagnostic and treatment implications for this group of patients.