Increased homocysteine levels correlate with cortical structural damage in Parkinson's disease.

BACKGROUND: Blood homocysteine appears to be increased in Parkinson's disease (PD) and may play a role in the development and progression of this disorder. However, the specific contribution of abnormal homocysteine levels to cortical degeneration in PD remains elusive. OBJECTIVE: To characterize the cortical structural correlates of homocysteine levels in PD. METHODS: From the COPPADIS cohort, we identified a subset of PD patients and healthy controls (HC) with available homocysteine and imaging data. Surface-based vertex-wise multiple regression analyses were performed to investigate the cortical macrostructural (cortical thinning) and microstructural (increased intracortical diffusivity) correlates of homocysteine levels in this sample. RESULTS: A total of 137 PD patients and 43 HC were included. Homocysteine levels were increased in the PD group (t = -2.2, p = 0.03), correlating in turn with cognitive performance (r = -0.2, p = 0.03). Homocysteine in PD was also associated with frontal cortical thinning and, in a subset of patients with available DTI data, with microstructural damage in frontal and posterior-cortical regions (p < 0.05 Monte-Carlo corrected). CONCLUSIONS: Homocysteine in PD appears to be associated with cognitive performance and structural damage in the cerebral cortex. These findings not only reinforce the presence and importance of cortical degeneration in PD, but also suggest that homocysteine plays a role among the multiple pathological processes thought to be involved in its development.

In vivo cholinergic basal forebrain degeneration and cognition in Parkinson's disease: Imaging results from the COPPADIS study.

INTRODUCTION: We aimed to assess associations between multimodal neuroimaging measures of cholinergic basal forebrain (CBF) integrity and cognition in Parkinson's disease (PD) without dementia. METHODS: The study included a total of 180 non-demented PD patients and 45 healthy controls, who underwent structural MRI acquisitions and standardized neurocognitive assessment through the PD-Cognitive Rating Scale (PD-CRS) within the multicentric COPPADIS-2015 study. A subset of 73 patients also had Diffusion Tensor Imaging (DTI) acquisitions. Volumetric and microstructural (mean diffusivity, MD) indices of CBF degeneration were automatically extracted using a stereotactic CBF atlas. For comparison, we also assessed multimodal indices of hippocampal degeneration. Associations between imaging measures and cognitive performance were assessed using linear models. RESULTS: Compared to controls, CBF volume was not significantly reduced in PD patients as a group. However, across PD patients lower CBF volume was significantly associated with lower global cognition (PD-CRStotal: r = 0.37, p < 0.001), and this association remained significant after controlling for several potential confounding variables (p = 0.004). Analysis of individual item scores showed that this association spanned executive and memory domains. No analogue cognition associations were observed for CBF MD. In covariate-controlled models, hippocampal volume was not associated with cognition in PD, but there was a significant association for hippocampal MD (p = 0.02). CONCLUSIONS: Early cognitive deficits in PD without dementia are more closely related to structural MRI measures of CBF degeneration than hippocampal degeneration. In our multicentric imaging acquisitions, DTI-based diffusion measures in the CBF were inferior to standard volumetric assessments for capturing cognition-relevant changes in non-demented PD.