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Abstract
Objective To evaluate microstructural characteristics of the corpus callosum using diffusion tensor imaging (DTI) and their relationships to cognitive impairment in Parkinson disease (PD).
Methods Seventy-five participants with PD and 24 healthy control (HC) participants underwent structural MRI brain scans including DTI sequences and clinical and neuropsychological evaluations. Using Movement Disorder Society criteria, PD participants were classified as having normal cognition (PD-NC, n = 23), mild cognitive impairment (PD-MCI, n = 35), or dementia (PDD, n = 17). Cognitive domain (attention/working memory, executive function, language, memory, visuospatial function) z scores were calculated. DTI scalar values, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD), were established for 5 callosal segments on a midsagittal plane, single slice using a topographically derived parcellation method. Scalar values were compared among participant groups. Regression analyses were performed on cognitive domain z scores and DTI metrics.
Results Participants with PD showed increased AD values in the anterior 3 callosal segments compared to healthy controls. Participants with PDD had significantly increased AD, MD, and RD in the anterior 2 segments compared to participants with PD-NC and most anterior segment compared to participants with PD-MCI. FA values did not differ significantly between participants with PD and participants with HC or among PD cognitive groups. The strongest associations for the DTI metrics and cognitive performance occurred in the most anterior and most posterior callosal segments, and also reflected fronto-striatal and posterior cortical type cognitive deficits, respectively.
Conclusions Microstructural white matter abnormalities of the corpus callosum, as measured by DTI, may contribute to PD cognitive impairment by disrupting information transfer across interhemispheric and callosal–cortical projections.
Glossary
- AD=
- axial diffusivity;
- ANCOVA=
- analyses of covariance;
- DTI=
- diffusion tensor imaging;
- FA=
- fractional anisotropy;
- HC=
- healthy control;
- HD=
- Huntington disease;
- IIT=
- Illinois Institute of Technology;
- MANCOVA=
- multivariate analyses of covariance;
- MD=
- mean diffusivity;
- MDS=
- Movement Disorder Society;
- MDS-UPDRS=
- Movement Disorder Society–Unified Parkinson's Disease Rating Scale;
- MMSE=
- Mini-Mental State Examination;
- PD=
- Parkinson disease;
- PD-MCI=
- Parkinson disease with mild cognitive impairment;
- PD-NC=
- Parkinson disease with normal cognition;
- PDD=
- Parkinson disease with dementia;
- RD=
- radial diffusivity;
- ROI=
- region of interest;
- TBSS=
- tract-based spatial statistics
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
CME Course: NPub.org/cmelist
- Received April 2, 2018.
- Accepted in final form August 23, 2018.
- © 2018 American Academy of Neurology
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