Mapping local hippocampal changes in Alzheimers disease and normal ageing with MRI at 3 Tesla

Histological studies have suggested differing involvement of the hippocampal subfields in ageing and in Alzheimers disease. The aim of this study was to assess in vivo local hippocampal changes in ageing and Alzheimers disease based on high resolution MRI at 3 Tesla. T-1-weighted images were acquired from 19 Alzheimers disease patients [age 766 years, three males, Mini-Mental State Examination 134] and 19 controls (age 745 years, 11 males, Mini-Mental State Examination 291). The hippocampal formation was isolated by manual tracing. Radial atrophy mapping was used to assess group differences and correlations by averaging hippocampal shapes across subjects using 3D parametric surface mesh models. Percentage difference, Pearsons r, and significance maps were produced. Hippocampal volumes were inversely correlated with age in older healthy controls (r 0.56 and 0.6 to the right and left, respectively, P0.05, corresponding to 14 lower volume for every 10 years of older age from ages 65 to 85 years). Ageing-associated atrophy mapped to medial and lateral areas of the tail and body corresponding to the CA1 subfield and ventral areas of the head corresponding to the presubiculum. Significantly increased volume with older age mapped to a few small spots mainly located to the CA1 sector of the right hippocampus. Volumes were 35 and 30 smaller in Alzheimers disease patients to the right and left (P0.0005). Alzheimers disease-associated atrophy mapped not only to CA1 areas of the body and tail corresponding to those also associated with age, but also to dorsal CA1 areas of the head unaffected by age. Regions corresponding to the CA23 fields were relatively spared in both ageing and Alzheimers disease. Hippocampal atrophy in Alzheimers disease maps to areas in the body and tail that partly overlap those affected by normal ageing. Specific areas in the anterior and dorsal CA1 subfield involved in Alzheimers disease were not in normal ageing. These patterns might relate to differential neural systems involved in Alzheimers disease and ageing.