White matter alteration of the cingulum in Parkinson disease with and without dementia: evaluation by diffusion tensor tract-specific analysis

Abstract

Background and purpose: In PD, the neurodegenerative process begins in the brain stem and extends to the limbic system and finally into the cerebral cortex. We used diffusion tensor tractography to investigate the FA of the cingulate fiber tracts in patients with PD with and without dementia.

Materials and methods: Fifteen patients with PD, 15 patients with PDD, and 15 age-matched healthy controls underwent diffusion tensor imaging with a 3T MR imager. Diffusion tensor tractography images of the anterior and posterior cingulate fiber tracts were generated. Mean diffusivity and FA were measured along the tractography of the anterior and posterior cingulate fiber tracts. One-way ANOVA with the Scheffé post hoc test was used to compare results among the groups.

Results: FA was significantly lower in patients with PDD than in healthy controls in both the anterior and the posterior cingulate fiber tracts (P = .003, P = .015) and significantly lower in patients with PD than in healthy controls (P = .003) in the anterior cingulate fiber tract. There were no significant mean diffusivity differences among the groups. MMSE and FA values of the anterior cingulate fiber tracts in patients with PDD were significantly correlated (r = 0.633, P < .05).

Conclusions: The reduced FA in patients with PD and PDD might reflect neuropathologic changes such as Lewy body pathology in the cingulate fibers. This abnormality might contribute to the dementing process in PD.

Fig 1.

Diffusion tensor tractography images of the right cingulate, fiber tracts (CFTs), and voxelization along with diffusion tensor tractography images of the anterior CFTs. A, Sagittal section of the color-coded map was used to determine coronal sections at the level of the genu of the corpus callosum and the middle of the corpus callosum. B, The seed ROI, including the entirety of the CFTs (light blue area), was placed manually on a coronal section of the color maps at the level of the genu of the corpus callosum. C, The target ROI, including the entirety of the CFTs (purple area), was placed manually on a coronal section of the color maps at the level of the center of the corpus callosum in the sagittal plane. D, Tractographic image of the right anterior CFTs was generated from the seed ROI (light blue line) to the target region of interest (purple line). E, In this study, the anterior CFTs were defined as the CFTs between the seed ROI and the target ROI. Voxelization was performed along the right anterior CFTs between the seed ROI and the target ROI (blue voxels), and FA values in coregistered voxels were calculated.

Fig 2.

Diffusion tensor tractography images of the right cingulate. Fiber tracts (CFTs) and voxelization along with diffusion tensor tractography of the posterior CFTs. A, Sagittal section of the color-coded map was used to determine coronal sections at the level of the splenium of the corpus callosum and the middle of the corpus callosum. B, The seed ROI, including the entirety of the CFTs (light blue area), was placed manually on a coronal section of the color maps at the level of the splenium of the corpus callosum. C, The target region of interest, including the entirety of the CFTs (purple area), was placed manually on a coronal section of the color maps at the level of the center of the corpus callosum in the sagittal plane. D, A tractographic image of the right posterior CFTs was generated from the seed ROI (light blue line) to the target ROI (purple line). E, In this study, the posterior CFTs were defined as the CFTs between the seed ROI and the target ROI. Voxelization was performed along the right posterior CFTs between the seed ROI and the target ROI (purple voxels), and FA values in coregistered voxels were calculated.

Fig 3.

FA values in the anterior cingulate fiber tracts in patients with PDD were significantly correlated with the MMSE scores (r = 0.633, P < .05).