Topography of cortical thinning associated with white matter hyperintensities in Parkinson's disease

Although white matter hyperintensities (WMHs) are associated with cognitive impairments in Parkinson's disease (PD), the relationships between WMHs and cortical atrophy in regard to cognitive impairments are unknown. Here, we investigated the topography of cortical thinning related to deep (DWMHs) and periventricular WMHs (PWMHs) and their differential impacts on cognitive performance in PD.

We enrolled 87 patients with non-demented PD and evaluated WMH scores using a semi-quantitative visual rating system. The patients were divided into low-, moderate-, and high-grade groups based on WMH severity for total WMHs (TWMHs), DWMHs, and PWMHs, and cortical thickness was measured using a surface-based method according to the WMHs severity. Additionally, the correlations between WMH-associated cortical thinning and neuropsychological performance were analyzed.

The detailed neuropsychological test demonstrated that PD patients with high-grade WMHs showed poorer performance on frontal lobe-based cognitive tasks compared with those with low-grade DWMHs. The areas of cortical thinning were more extensive in patients with DWMHs, involving the entire frontal areas and restricted temporoparietal areas, whereas in patients with PWMHs, cortical thinning was localized in the small frontal areas. A multiple regression analysis of the relationships between WMH-associated cortical thickness and cognition revealed that DWMH-associated frontal thickness had an independent effect on frontal lobe-based cognition, while frontal thickness related to PWMHs did not have a significant correlation with cognitive tasks.

These data suggest that in patients with PD, DWMHs are closely coupled with decreased cortical thickness in the frontal areas and may lead to declines in executive function.