Increased Cortical Thickness and Caudate Volume Precede Atrophy in PSEN1 Mutation Carriers

Abstract

Neuroimaging studies of familial Alzheimer's disease allow investigation of the disease process before clinical onset. We performed semi-automated MRI analysis to evaluate cortical thickness (CTh), grey matter (GM) volumes, and GM diffusivity indexes in PSEN1 mutation carriers (MC). We recruited 11 MC from 4 families with PSEN1 mutations (L286P, M139T, K239N) and 6 familial and 12 non-familial healthy controls. MC were classified as either asymptomatic (n=6) or symptomatic (n=5). Subjects underwent structural and diffusion-weighted 3-Tesla MRI scanning. CTh and GM volumes of subcortical structures and diffusivity indexes were calculated and group comparisons were performed. Structural images were reanalyzed with voxel-based morphometry methodology. Cerebrospinal fluid amyloid-β1-42 levels (Aβ) were measured. We found that symptomatic MC presented widespread cortical thinning, especially in precuneus and parietotemporal areas (p<0.01) and increased mean diffusivity (MD) in these areas compared to controls. Unexpectedly, asymptomatic MC, 9.9 years prior to the predicted age of disease onset, presented increased CTh in the precuneus and parietotemporal areas (p<0.01), increased caudate volumes (p<0.01), and decreased MD (p<0.05) in these areas compared to HC. In MC, CTh correlated with adjusted age. Aβ values were within normal limits in AMC. In conclusion, at early preclinical stages, CTh in the precuneus and parietotemporal regions and caudate volume increase in PSEN1 MC and decrease thereafter with disease progression. The different trends in MD in asymptomatic and symptomatic MC suggest that different microstructural changes underlie the contrasting morphometric findings. Reactive neuronal hypertrophy or/and inflammation may account for increased CTh and decreased MD in asymptomatic MC.