Comparison of hippocampus, entorhinal cortex, and amygdala volumes in individuals with Alzheimer's disease, mild cognitive impairment, and healthy individuals

BackgroundMild cognitive impairment (MCI) and Alzheimer's disease (AD) are associated with structural alterations in medial temporal lobe regions, which can be evaluated using volumetric magnetic resonance imaging.ObjectiveIn this study, we aimed to compare the volumes of the hippocampus, amygdala, and entorhinal cortex in individuals diagnosed with MCI and AD with those of healthy controls.MethodsMagnetic resonance images from AD, MCI, and healthy control groups were retrospectively obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, including 100 individuals in each group. Volumetric measurements of the right, left, and total hippocampus, amygdala, and entorhinal cortex, as well as their ratios to total brain volume, were obtained using the VolBrain automated segmentation software.ResultsThe volumes of the hippocampus, amygdala, and entorhinal cortex were significantly lower in the AD group compared with both the MCI and control groups (p < 0.05). In comparisons between the MCI and control groups, a statistically significant difference was observed only in the left entorhinal cortex volume, whereas no significant differences were detected in other medial temporal structures.ConclusionsThese findings demonstrate group-level differences in medial temporal lobe volumes, with more pronounced reductions observed in individuals with AD. The isolated reduction observed in the left entorhinal cortex in the MCI group reflects a region- and hemisphere-specific structural difference at the group level, which should be interpreted cautiously and warrants further investigation using longitudinal and clinico-cognitive approaches.