The association between hippocampal subfield volumes in mild cognitive impairment and conversion to Alzheimer's disease.

The hippocampal complex, strongly implicated in Alzheimer's disease (AD), is a region with functionally and structurally distinct subfields. Hippocampal subfield volumes may represent a more sensitive indicators of AD development than total hippocampal volume. We aimed to identify which subfield is the most predictive measure for an AD diagnosis and which is the most specific indicator of the conversion from mild cognitive impairment (MCI) to AD. We analyzed longitudinal structural neuroimaging data of 1350 individuals, 350 healthy controls (HC), 650 MCI and 350 AD, using FreeSurfer v6.0. The linear regression models corrected for total hippocampal volume revealed that subicular fields are the most predictive measures of AD diagnosis. Hippocampal fissure volume was significantly associated with conversion from MCI to AD. Our findings suggest that subicular hippocampal fields are most predictive of AD diagnosis, which has clinical implications for early detection. Specifically, subicular and hippocampal fissure volume measures may be used to select MCI participants who are most likely to convert in AD in clinical trials.