Objective: To determine the relative changes in white matter integrity as measured by diffusion tensor imaging (DTI) magnetic resonance imaging (MRI) in PD patients relative to a matched control group.

Background: Progressive neuronal loss in neurodegenerative diseases such as Parkinson’s disease (PD) is associated with progressive degeneration of associated white matter tracts. These findings, in particular in a de novo population, may have diagnostic and functional implications. Therefore, longitudinal DTI data from Parkinson Progression Markers Initiative PD patients and control participants were analyzed for relative changes over time.

Methods: Baseline and one-year follow-up DTI MRI data from 71 PD patients and 45 healthy control PPMI participants were included in the analyses. Whole-brain fractional anisotropy (FA) and mean diffusivity (MD) images were analyzed in SPM12 implemented in Matlab R2013b with analyses of covariance, with age and sex as covariates. FA indicates the degree to which water molecules’ diffusion is directionally restricted (where lower values indicate more degeneration), while MD indicates the mean diffusivity of water molecules in a given voxel (where higher values indicate more degeneration). Significant results are defined as those surviving a voxel-wise threshold of p < .01 combined with a permutation-based multiple comparison correction at cluster level (p<.05).

Results: Whole-brain voxel-wise exploratory analyses revealed a significant FA decline in PD over one year as compared to HC. These changes were apparent in both white matter (body of corpus callosum, splenium, and posterior thalamic radiation) and gray matter (middle, superior frontal gyri, orbito-frontal gyri, middle temporal gyrus, occipital lobes) regions. Correspondingly, mean diffusivity significantly increased in PD relative to HC participants in the middle and superior frontal and precentral gyri.

Conclusions: Significant gray and white matter degeneration takes place already in the first year of de novo PD, indicating functional-neuroanatomical circuits likely to be affected. These findings suggest that DTI may serve as a sensitive biomarker of disease progression in early-stage PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/longitudinal-decline-in-white-matter-integrity-in-parkinsons-disease-an-analysis-of-parkinson-progression-markers-initiative-diffusion-tensor-imaging-data/