Neuroanatomic basis of amnestic MCI differs in patients with and without Parkinson disease

Objective: To explore the neuroanatomic basis of amnestic mild cognitive impairment (aMCI) in patients with Parkinson disease (PD; aMCI-PD⁺) and without PD (aMCI-PD⁻).

Methods: A total of 119 patients with aMCI (aMCI-PD⁻, n = 78, and aMCI-PD⁺, n = 41) underwent T1-weighted MRI, and the image data were analyzed using voxel-based morphometry.

Results: No significant differences in demographic characteristics or general cognition were found between patients with aMCI-PD⁻ and aMCI-PD⁺. Comparisons of neuropsychological tests between groups revealed that patients with aMCI-PD⁻ had lower scores in delayed verbal and visual recognition memory, whereas visuospatial dysfunction was more severe in patients with aMCI-PD⁺. Gray matter (GM) density in the right temporal and posterior cingular cortices was significantly lower in the aMCI-PD⁻ group compared with controls. In contrast, GM density in the aMCI-PD⁺ group was significantly lower in the precuneus and left prefrontal and primary motor areas relative to controls. A direct comparison between groups showed that decreased GM density in aMCI-PD⁻ relative to aMCI-PD⁺ was localized in the right temporal and anterior prefrontal areas, whereas decreased GM density in aMCI-PD⁺ relative to aMCI-PD⁻ was involved in the bilateral precuneus, left primary motor, and right parietal areas. Memory decline was correlated with temporal area atrophy in aMCI-PD⁻ and with posterior cingulate cortex atrophy in aMCI-PD⁺.

Conclusions: Our data suggest that different neuroanatomic systems underlie memory dysfunction in patients with aMCI-PD⁻ and aMCI-PD⁺.