Topography of cortical thinning areas associated with hippocampal atrophy (HA) in patients with Alzheimer's disease (AD)

Prior studies have shown that patients with AD have decreased functional or structural connectivity between the hippocampus and other brain areas. To the best of our knowledge, however, there have been no studies investigating the topography of cortical thinning areas and correlations with HA using surface based morphometry of three-dimensional (3D) T1-weighted magnetic resonance (MR) images. Cortical thickness was measured using SBM, and hippocampal volume was measured using an automated method, in 219 patients with AD and 54 subjects with no cognitive impairment (NCI). A partial correlation model was used in analysis of cortical thinning related to HA. Cortical thinning areas related to HA were found mostly within areas associated with polysynaptic or direct pathways of the hippocampus, a finding consistent with the disconnection hypothesis. Therefore, the cortical atrophy related to HA in patients with AD may represent disrupted cortical brain networks in connection with HA. However, since the topography of HA-related cortical thinning in groups with Clinical Dementia Ratings (CDR) of 0.5 and 1 corresponded to the stages I-II and III-IV of Braak and Braak staging, respectively, we could not exclude the possibility of the "concomitant hypothesis," i.e. that these areas are affected concomitantly with the hippocampus.