White matter microstructural damage as an early sign of subjective cognitive decline

Abstract

AbstractBackgroundSubjective cognitive decline (SCD) is considered a preclinical state of Alzheimer's disease (AD) and may represent a more advanced preclinical status than amnestic mild cognitive impairment (aMCI). Our aim was to explore changes in the white matter (WM) microstructure and their correlation with cognitive function in these AD‐spectrum patients.MethodDiffusion tensor images from 43 individuals with normal cognition (NC), 38 SCD patients and 36 aMCI patients were compared using an atlas‐based segmentation strategy. The correlation between diffusion parameters and cognitive function was further analysed.ResultThe anatomical pattern of WM impairment was generally similar between SCD and aMCI patients. However, aMCI patients showed significantly lower fractional anisotropy (FA) values in corpus callosum (forceps major (Fma) and forceps minor (Fmi)), as well as significantly increased mean diffusivity (MD) in the bilateral anterior thalamic radiation (ATR), left corticospinal tract (CST. L), Fmi, left Cingulum (cingulate gyrus) (CgC. L), left cingulum (hippocampus) (CgH. L), and left inferior fronto‐occipital fasciculus (IFO. L), than those of SCD subjects, indicating a disruption in WM microstructural integrity in the aMCI. Individuals with microstructural disruption in Fmi, CgC. L and CgH. L tracts performed worse in general cognition and memory function tests, as indicated by line regression analysis.ConclusionSCD individuals had extensive WM microstructural damage in a pattern similar to that seen in aMCI, although presenting a cognitive performance comparable to cognitively healthy individuals. Our results suggest that WM integrity might precede objectively measurable memory decline and may be a potential early biomarker for AD.