Three-dimensional patterns of hippocampal atrophy in mild cognitive impairment

Objective: To measure hippocampal volumes in patients diagnosed as having subtypes of mild cognitive impairment (MCI) relative to those of elderly control subjects and those of patients with Alzheimer disease (AD) using 3-dimensional mesh reconstructions. Design: A magnetic resonance imaging volumetric study of MCI subgroups (MCI, amnesic subtype [MCI-A]; and MCI, multiple cognitive domain subtype) using 3-dimensional mesh reconstructions of the structure. Setting: Referral dementia clinic. Subjects: Twenty-six subjects with MCI (MCI-A, n = 6; and MCI, multiple cognitive domain subtype, n= 20), 20 subjects with AD, and 20 controls who were equivalent in age, education, and sex distributions. Main Outcome Measures: Three-dimensional parametric mesh models of the hippocampus and total hippocampal volumes. Results: The hippocampi of the patients with AD were significantly atrophic relative to those of the healthy controls. The MCI, multiple cognitive domain subtype, group did not differ from the controls, yet was significantly different from the MCI-A and the AD groups. The MCI-A patients had significant hippocampal atrophy compared with the controls, and did not differ significantly from the patients with AD. Conclusion: These data add to the growing evidence that there are multiple forms of MCI, that they have distinct neuropathological correlates, and that MCI, multiple cognitive domain subtype, is not a more advanced form of the MCI-A subtype.