Subcortical Atrophy Is Associated with Cognitive Impairment inMild Parkinson Disease: A Combined Investigation of Volumetric Changes, Cortical Thickness, and Vertex-Based Shape Analysis

BACKGROUND AND PURPOSE: The involvement of subcortical deep gray matter and cortical thinning associated with mild Parkinson disease remains poorly understood. We assessed cortical thickness and subcortical volumes in patients with Parkinson disease without dementia and evaluated their associations with cognitive dysfunction. MATERIALS ANDMETHODS: The study included 90 patients withmild Parkinson diseasewithout dementia. Neuropsychological assessments classified the sample into patients withmild cognitive impairment (n 25) and patients without cognitive impairment (n 65). Volumetric data for subcortical structures were obtained by using the FMRIB Integrated Registration and Segmentation Tool while whole-brain, gray and white matter volumes were estimated by using Structural Image Evaluation, with Normalization of Atrophy. Vertex-based shape analyses were performed to investigate shape differences in subcortical structures. Vertex-wise group differences in cortical thickness were also assessed. Volumetric comparisons between Parkinson disease with mild cognitive impairment and Parkinson disease with no cognitive impairment were performed by using ANCOVA. Associations of subcortical structures with both cognitive function and disease severity were assessed by using linear regression models. RESULTS: Compared with Parkinson disease with no cognitive impairment, Parkinson disease with mild cognitive impairment demon-strated reduced volumes of the thalamus (P .03) and the nucleus accumbens (P .04). Significant associationswere found for the nucleus accumbens and putamen with performances on the attention/working memory domains (P .05) and nucleus accumbens and languag