PMC

FA and MD values in the tracts of the genu of the corpus callosum in the PD and PDD patient groups combined were significantly correlated with MMSE score (FA: r = 0.472, P = 0.002; MD: r = −0.453, P = 0.003)

In PD and PDD patients, TBSS analysis identified a significant positive correlation between FA and MMSE score. (P < 0.05, corrected for multiple comparisons, gender and age at the time of MRI). Red–yellow voxels demonstrate a significant correlation between the MMSE score and FA

Diffusion tensor tractography images of the genu of the corpus callosum and fibre tracts, and voxelisation. a The seed region of interest was placed manually including the entire genu of the corpus callosum (light blue area) on a reconstructed mid-sagittal image with a non-diffusion-weighted image (b = 0 s/mm²). b Tractographic image of the genu of the corpus callosum was generated with threshold values of line-tracking termination as fractional anistropy (FA) > 0.18. c, d Fibre tracts of the genu of the corpus callosum were defined as follows: anterior–posterior, including the first sixth of the corpus callosum; above and below, including the upper and lower border of the genu of the corpus callosum; right–left, between the anterior horns of the lateral ventricles. e Voxelisation was performed along the genu of the corpus callosum (blue voxels). FA and mean diffusivity (MD) values in co-registered voxels were calculated

Corrected P maps. Tract-based spatial statistics (TBSS) analysis of the FA of normal control vs Parkinson’s disease with dementia (PDD) (a), MD of normal controls vs PDD (b), FA of Parkinson’s disease (PD) vs PDD (c), MD of PD vs PDD (d). All images are displayed in Montreal Neurological Institute space. a TBSS analysis demonstrated significantly decreased FA (red–yellow voxels) in several major white-matter tracts in the PDD group compared with the control group. b MD was increased in almost the same white-matter tracts as those in which FA was decreased in the PDD group compared with the control group (blue-light blue voxels). c In patients with PDD, FA values in the anterior part of the inferior fronto-occipital fasciculus (i.e. the white matter adjacent to the prefrontal area) and in part of the genu of the corpus callosum were significantly lower than those in PD patients (red-yellow voxels). d MD was increased in almost the same white-matter tracts as those in which FA was decreased in PDD patients relative to PD patients (blue-light blue voxels)