Abstract
Purpose: The aim of this study was to evaluate microstructural changes of major white matter (WM) tracts in patients with vascular cognitive impairment (VCI).Method: Diffusion tensor imaging (DTI) data were obtained from 24 subjects with subcortical ischemic vascular disease (SIVD), including 13 subjects with VCI-no dementia (VCIND) and 11 subjects with normal cognition (as a control group). A tract-based spatial statistics approach was performed to investigate WM microstructure in VCIND by integrating multiple indices including fractional anisotropy (FA) and mean diffusivity (MD), which are intra-voxel metrics, and local diffusion homogeneity (LDH), which is an inter-voxel metric.Results: The VCIND group had decreased FA and increased MD values throughout widespread WM areas predominately in the corpus callosum, bilateral internal capsule/corona radiata/posterior thalamic radiation/inferior fronto-occipital fasciculus and right inferior/superior longitudinal fasciculus. There was a slight discrepancy between the distribution of areas with decreased FA and LDH. The FA, MD and LDH values were significantly correlated with cognitive test results. According to a WM tract atlas, 10 major tracts were identified as tracts of interest in which three diffusion metrics simultaneously differed between groups, including bilateral anterior thalamic radiation, forceps minor, right corticospinal tract, bilateral inferior fronto-occipital fasciculus, left inferior and superior longitudinal fasciculus, and bilateral uncinate fasciculus. Receiver operating characteristic (ROC) analysis demonstrated the feasibility of using diffusion metrics along the forceps minor and left anterior thalamic radiation for separating two groups.Conclusion: The results suggest WM microstructural abnormalities contribute to cognitive impairments in SIVD patients. DTI parameters may be potential biomarkers for detecting VCIND from SIVD.
Highlights
Vascular cognitive impairment (VCI) is defined as cognitive deficits attributable to various cerebrovascular causes, which can be classified into three subtypes: vascular cognitive impairment-no dementia (VCIND), vascular dementia, and mixed primary neurodegenerative dementia with vascular dementia (Moorhouse and Rockwood, 2008)
The fractional anisotropy (FA), mean diffusivity (MD) and local diffusion homogeneity (LDH) values were significantly correlated with cognitive test results
According to a White matter (WM) tract atlas, 10 major tracts were identified as tracts of interest in which three diffusion metrics simultaneously differed between groups, including bilateral anterior thalamic radiation, forceps minor, right corticospinal tract, bilateral inferior fronto-occipital fasciculus, left inferior and superior longitudinal fasciculus, and bilateral uncinate fasciculus
Summary
Vascular cognitive impairment (VCI) is defined as cognitive deficits attributable to various cerebrovascular causes (such as small and large vessel diseases), which can be classified into three subtypes: vascular cognitive impairment-no dementia (VCIND), vascular dementia, and mixed primary neurodegenerative dementia (usually Alzheimer’s disease) with vascular dementia (Moorhouse and Rockwood, 2008). Correlation analyses have consistently shown that DTI metrics are associated with cognitive performance among patients with small vessel disease (SVD, one of most common causes for VCI; Kim et al, 2011; Zhou et al, 2011; Tuladhar et al, 2015). Several DTI studies, which utilizes the fiber tracking technique and graph theoretical analysis, have highlighted disruption of structural WM networks (e.g., reduced connection strengths and network efficiency) in SVD (Tuladhar et al, 2016a), which is considered as an important neural substrate of cognitive impairment (Lawrence et al, 2014) and a predictor of disease progression (Tuladhar et al, 2016b)
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