White and gray matter microstructural alterations in subjective cognitive decline: An exploratory study using TBSS...

Subjective cognitive decline (SCD), which may represent the preclinical stage of Alzheimer's disease (AD) in a subset of individuals, lacks objective biomarkers, thus hindering the implementation of early intervention for AD. This study tentatively explored the potential value of neurite orientation dispersion and density imaging (NODDI) in assessing the microstructural integrity of gray matter (GM) and white matter (WM) in SCD.

We enrolled 47 SCD subjects and 30 healthy controls (HCs). Through the TBSS and GBSS analysis based on NODDI, the neurite density index (NDI) and orientation dispersion index (ODI) were used to evaluate the microstructural integrity of GM and WM. NODDI parameters were extracted from multiple brain regions to assess their diagnostic utility in distinguishing SCD from HCs.

In WM microstructure, NDI of the genu of corpus callosum was decreased, and the ODI of the left posterior thalamic radiation and posterior corona radiata were decreased. In GM microstructure, the NDI of the left hippocampus, amygdala and parahippocampal gyrus were decreased, whereas the ODI of the rolandic operculum, opercular part of inferior frontal gyrus, and precentral gyrus were increased. Logistic regression analysis results showed that the NDI value of GM, the ODI value of GM and the ODI value of WM were independent predictors and the combination of the three parameters had the best classification effect.

This exploratory study suggests that NODDI may detect microstructural differences in GM and WM associated with SCD. These preliminary findings provide hypothesis-generating clues for future research into potential imaging markers for identifying SCD individuals. Additional studies are necessary to confirm these preliminary results.