Detection of hippocampal volume changes on elderly control, MCI and AD patients from the ADNI database: a one-year follow-up

Abstract

A number of MRI studies have shown the significant role of hippocampus in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Furthermore, longitudinal studies suggest that hippocampal volume loss predicts cognitive decline in MCI and AD patients. In this study, 10 patients with AD (4 males, 6 females, age ± standard-deviation (SD) = 75 ± 5 years, mini-mental score (MMS) = 24.2 ± 2.5), 10 patients with MCI (4 males, 6 females, age ± SD = 72 ± 9 years, MMS = 27.5 ± 1.9) and 10 elderly healthy (C) controls (4 males, 6 females, age ± SD = 77 ± 6years) from the ADNI database were studied. Written informed consent for the study was obtained from all participants before protocol-specific procedures, including cognitive testing, were performed. All subjects were scanned at baseline, month-6 and at month-12 with a standardized MRI protocol (3D T1-weighted MP-RAGE sequence). For each patient, left and right hippocampi were segmented using a semi-automated technique [3] which allows fast segmentation with minimal user interactions. Segmented hippocampus masks were quality controlled prior to final quantification. Group differences in hippocampus volume were assessed using the Student's t-tests. Significant hippocampal volume reductions were observed at baseline and were increased at month-6 and month-12, in both AD and MCI patients, compared to elderly controls (Table 1). AD patients also had significantly smaller hippocampal volumes compared to MCI patients (Figure 1). Atrophy rates, computed at month-6 and month-12 are given in Table 2. Hippocampal atrophy rates were significantly higher in MCI and AD groups. This study demonstrated that the quantification technique was able to detect significant absolute volume differences in both AD and MCI patients compared to elderly controls. Moreover, significant atrophy rates were observed over time in all groups with significantly higher levels in MCI and AD groups. The results are in agreement with recently published results. A deeper clinical validation involving more patients, demographic data and clinical scores is in progress.