Diffusion Tensor Imaging Changes Correlate with Clinical Progression in Vascular Mild Cognitive Impairment and Vascular Dementia of Subcortical Type

Abstract

Background: Cerebral small vessel disease (SVD) induces vascular cognitive impairment (VCI) such as subcortical vascular dementia (SVaD) and subcortical vascular mild cognitive impairment (svMCI). We compared MRI parameters between SVaD and svMCI and determined which MRI parameters best correlated with cognitive function and disability on cross-sectional and longitudinal analyses within them. Methods: Twenty-four patients with SVaD and twelve with svMCI were recruited. They underwent multimodal MRIs including fluid-attenuated inversion recovery lesion load, lacunar infarct number, and fractional anisotropy (FA) and mean diffusivity (MD) from diffusion tensor imaging (DTI), neuropsychological testing, Sum of Boxes of Clinical Dementia Rating Scale (CDR-SB), Barthel Index, and the Korean version of a Geriatric Depression Scale (GDS-K). Seventeen patients were retested after 20 months for a brain MRI and clinical evaluation. Results: There were significant differences in average MD and peak height of MD histograms within normal-appearing brain tissue (NABT) between SVaD and svMCI patients. In the cross-sectional analysis, average MD within NABT significantly correlated with the composite neuropsychology score (r=-0.80, p<0.001), the composite executive function score (r=-0.67, p< 0.001), and the CDR-SB (r=0.54, p=0.001), and the Barthel Index correlated with peak heights of the MD histograms (r=0.37, p=0.03) in NABT. Changes of CDR-SB was associated with changes of average MD within WMH (r=0.57, p=0.02), and changes of GDS-K was associated with changes of WMH volume (r=0.51, p=0.04) on a longitudinal scale. Conclusions: DTI parameters in NABT correlated with cognitive impairment and disability in VCI associated with SVD. Clinical progression of SVD was associated with some increment of WML volume and ultrastructural changes in WMH.