Neuropathological Findings in Parkinson's Disease With Mild Cognitive Impairment

Objective: There are few neuropathological studies on Parkinson's disease with mild cognitive impairment (PD-MCI). Those published reveal coexisting Lewy body and Alzheimer's disease pathology. Our objective is to determine the pathology that underlies PD-MCI. Methods: We used data from the Arizona Study of Aging and Neurodegenerative Disorders, a longitudinal clinicopathological study. Of 736 autopsied subjects with standardized movement and cognitive assessments, 25 had PD-MCI. Neuropathological findings, including Lewy body and Alzheimer's disease pathology, were compared in PD subjects with amnestic MCI (A-MCI) and nonamnestic MCI (NA-MCI). Results: Significant pathological heterogeneity within PD-MCI was found. This included varying Lewy body stages, Alzheimer's disease pathology, and cerebral amyloid angiopathy. There was a significant increase in the severity of Lewy body pathology (meeting The Unified Staging System for Lewy Body disorders neocortical stage) in nonamnestic MCI (7/1, 63%) when compared with amnestic MCI (3/14, 21%, P = 0.032). Conclusion: Although a small study, distinct pathological changes may contribute to PD-MCI phenotype.