Objective: The aim of this study was to use MR diffusion tensor imaging to investigate the brain microstructural alterations in newly diagnosed drug-naïve Parkinson’s disease patients with and without mild cognitive impairment.

Background: Cognitive impairment is one of the most frequent non-motor symptoms of Parkinson’s disease (PD) and varies from mild deficit through to severe dementia. While mild cognitive impairment (MCI) frequently occurs in early stage of dementia. Prevalence of MCI ranges from 19% to 38% in early PD patients and these PD-MCI patients are at increased risk of dementia compared with cognitively intact patients. Diffusion tensor imaging (DTI) is an MRI technique used to assess white matter microstructural changes in vivo by exploiting the diffusion characteristics of water molecules in the brain. However, only a few DTI studies have investigated the white matter changes associated with MCI in PD patients and their results are not consistent. Up to date, no DTI study has focused on newly diagnosed drug-naïve PD-MCI patients.

Methods: We studied 16 patients with PD-MCI, 10 PD patients with no cognitive impairment (PD-NCI) and 17 healthy controls (HC) matched with age, gender and education years. DTI data were acquired and analyzed in terms of fractional anisotropy (FA) and mean diffusivity (MD). Partial correlations were computed to examine relationships between the mean DTI parameter values in significant regions and cognitive scores.

Results: Patients with PD-MCI exhibited increased MD values in the precuneus bilaterally, posterior cingulate cortex bilaterally, right caudate, left cuneus and vermis when compared with HC, left posterior cingulate cortex and left dental nucleus when compared with PD-NCI. Compared with HC, patients with PD-NCI also demonstrated significantly increased MD in the left precuneus. In PD patients, there were significant correlations between mean MD values in the precuneus and posterior cingulate cortex and cognitive scores of attention, memory and visuospatial abilities, after controlling for age and gender.

Conclusions: Our whole-brain-based analysis firstly identifies microstructural abnormalities of newly diagnosed untreated PD patients with MCI, suggesting precuneus and posterior cingulate cortex may be potential neural substrates of cognitive impairment in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/microstructural-abnormalities-in-drug-naive-parkinsons-disease-with-mild-cognitive-impairment-a-diffusion-tensor-imaging-study/