Objective: To evaluate diffusion characteristics of the corpus callosum in Parkinson’s disease (PD) patients with varying degrees of cognitive impairment using Diffusion Tensor Imaging (DTI).

Background: The majority of PD patients eventually develop dementia (PDD), often preceded by a prodrome of mild cognitive impairment (PD-MCI). Prior studies have demonstrated volumetric and DTI changes in the corpus callosum in PD participants with cognitive impairment, but with limited information regarding the subregions of the callosum affected.

Methods: 75 PD and 24 healthy control (HC) participants received clinical and neuropsychological evaluation, MRI brain scans including DTI sequences with 26 non-collinear directions, and cognitive classification by Movement Disorder Society criteria (cognitively normal [PD-NC], n=23; PD-MCI, n=35; demented [PDD], n=17). Z-scores for cognitive domain performance (attention/working memory, executive function, memory, language, visuospatial function) were calculated. Diffusion weighted imaging volumes were pre-processed using FSL, including calculation of Fractional Anisotropy (FA), Mean Diffusivity (MD), Radial Diffusivity (RD), and Axial Diffusivity (AD) scalar values which were non-linearly registered to the IIT Brain Atlas mean-FA map (Varentsova, 2014). The callosum was divided into 5 parcellated segments (Hofer & Frahm, 2006). Scalar values of the 5 callosal segments were compared between PD and HC cohorts and among PD cognitive groups using MANCOVA models, covarying for age, sex, and PD duration. Regression analyses were performed on cognitive domain scores and callosal scalar values.

Results: PD participants showed increased AD values in the anterior 2/3rds of the corpus callosum compared to HCs. PDD participants had increased AD, MD, and RD values in the anterior 1/2 of the callosum compared to PD-NC and the anterior 1/6 of the callosum compared to PD-MCI participants. DTI scalar values and cognitive domain z-scores showed the strongest associations in the most anterior callosal region.

Conclusions: Conclusions:
 The corpus callosum appears to undergo white matter microstructural changes in PD. These changes may contribute to PD cognitive dysfunction due to altered information transfer among connected cortical areas.


Study Supported by:
 NIH K23NS060949, Michael J. Fox Foundation, and Parkinson’s Disease Foundation

References: Varentsova, A., Zhang, S., & Arfanakis, K. (2014). Development of a high angular resolution diffusion imaging human brain template. NeuroImage, 91, 177-186.

Hofer, S., & Frahm, J. (2006). Topography of the human corpus callosum revisited—comprehensive fiber tractography using diffusion tensor magnetic resonance imaging. Neuroimage, 32(3), 989-994.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/diffusion-tensor-imaging-changes-in-the-corpus-callosum-and-cognitive-impairment-in-parkinsons-disease/