Diffusion tensor imaging of vascular parkinsonism: structural changes in cerebral white matter and the association with clinical severity.

OBJECTIVE: To investigate the white matter (WM) microstructure using diffusion tensor imaging in patients with vascular parkinsonism (VP) and specific fiber tract involvement with respect to clinical severity.

DESIGN: Diffusion measures (fractional anisotropy and mean diffusivity) were calculated from diffusion tensor images of patients with VP and control subjects. We performed global-, voxel-, and tract-based analyses to compare WM microstructural properties between groups.We further correlated findings with Unified Parkinson's Disease Rating Scale scores and modified postural instability gait difficulty (PIGD) scores to identify most relevant tract involvement.

SETTING: Shin-Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.

PARTICIPANTS: Twelve patients with VP and 12 age-matched healthy controls without VP.

RESULTS: In the VP group, the left thalamus, right frontal subcortical WM, and left anterior limb of the internal capsule had a significantly lower regional fractional anisotropy compared with the control group. The bilateral frontal subcortical WM showed a significantly higher regional mean diffusivity. The diffusion metrics in these regions were significantly correlated with the modified PIGD score part III, and the sum of modified PIGD scores parts II and III. Tract-based analysis showed a group difference in mean fractional anisotropy and mean diffusivity for multiple fiber bundles, but only diffusion measures of fiber tracts from the bilateral frontal lobe that pass through the anterior limb of internal capsule and tracts of the genu of the corpus callosum showed significant correlation with these scores.

CONCLUSIONS: Disruption of the microstructural organization of frontal lobe WM is associated with the severity of VP. Our findings are in accordance with the frontal lobe disconnection hypothesis for gait problems and reinforce the paradigm that the involvement of fibers related to the prefrontal cortex is crucial for the core features of VP.