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Mov Disord. 2018 Jul;33(7):1139-1150. doi: 10.1002/mds.27364. Epub 2018 Apr 23.

White matter degeneration profile in the cognitive cortico-subcortical tracts in Parkinson's disease.

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Department of Clinical Neurosciences and Department of Radiology, University of Calgary, Calgary, Alberta, Canada.
Cumming School of Medicine, Hotchkiss Brain Institute, Calgary, Alberta, Canada.
Sherbrooke Connectivity Imaging Lab (SCIL), Computer Science Department, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montréal, Quebec, Canada.
Centre de Recherche, Institut Universitaire de Gériatrie de Montréal, Montréal, Quebec, Canada.
Department of Neurology and Neurosurgery, McGill University, Montréal, Quebec, Canada.
Movement Disorders Unit, McGill University Health Center, Montréal, Quebec, Canada.
Unité des Troubles du Mouvement André Barbeau, Centre Hospitalier de l'Université de Montréal, Montréal, Quebec, Canada.
Department of Radiology, Faculty of Medicine, University of Montréal, Montréal, Quebec, Canada.



In Parkinson's disease cognitive impairment is an early nonmotor feature, but it is still unclear why some patients are able to maintain their cognitive performance at normal levels, as quantified by neuropsychological tests, whereas others cannot. The objectives of this study were to perform a cross-sectional study and analyze the white matter changes in the cognitive and motor bundles in patients with Parkinson's disease.


Sixteen Parkinson's disease patients with normal cognitive performance, 19 with mild cognitive impairment (based on their performance of 1.5 standard deviations below the healthy population mean), and 16 healthy controls were compared with respect to their tractography patterns between the cortical cognitive / motor regions and subcortical structures, using high angular resolution diffusion imaging and constrained spherical deconvolution computation.


Motor bundles showed decreased apparent fiber density in both PD groups, associated with a significant increase in diffusivity metrics, number of reconstructed streamlines, and track volumes, compared with healthy controls. By contrast, in the cognitive bundles, decreased fiber density in both Parkinson's groups was compounded by the absence of changes in diffusivity in patients with normal cognition, whereas patients with cognitive impairment had increased diffusivity metrics, lower numbers of reconstructed streamlines, and lower track volumes.


Both PD groups showed similar patterns of white matter neurodegeneration in the motor bundles, whereas cognitive bundles showed a distinct pattern: Parkinson's patients with normal cognition had white matter diffusivity metrics similar to healthy controls, whereas in patients with cognitive impairment white matter showed a neurodegeneration pattern. © 2018 International Parkinson and Movement Disorder Society.


Parkinson's disease; constrained spherical deconvolution; high angular resolution diffusion imaging; mild cognitive impairment; white matter


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