Surface-based but not voxel-based morphometry reveals structural abnormalities in individuals with subjective cognitive decline

: BackgroundSubjective cognitive decline (SCD) refers to individuals who perceive a decrease in their cognitive functioning despite no detectable deficits on neuropsychological tests, and may represent the earliest clinical stage of Alzheimer's disease (AD).ObjectiveThe aim of this study was to assess grey matter (GM) volumes and cortical folding patterns in individuals with SCD compared with the broader AD spectrum.MethodsA total of 107 participants were enrolled: 31 with AD, 23 with amnestic mild cognitive impairment (aMCI), 25 with SCD and 28 healthy participants (HS). All participants underwent neuropsychological assessment and 3T MRI to acquire T1-weighted images, which were processed using CAT-12 for voxel-based morphometry (VBM) and surface-based morphometry (SBM).ResultsVBM revealed expected atrophic patterns in AD and aMCI patients compared to SCD and HS, with no volumetric differences found between SCD individuals and HS. Notably, AD patients showed cortical surface abnormalities in all SBM measures. aMCI patients showed reduced cortical thickness and gyrification compared to SCD and HS. In contrast, SCD individuals showed reduced gyrification and sulcal depth compared to HS.ConclusionsThese findings suggest that cortical surface abnormalities may manifest early in the AD continuum, whereas volumetric changes occur later. The use of multiparametric MRI techniques may be beneficial in detecting subtle changes within the AD spectrum, highlighting the potential for early identification of structural changes associated with cognitive decline in SCD individuals. Further research is warranted to explore these relationships and their implications for early intervention strategies in AD.