Uncal apex movement and positioning in Alzheimer's Disease

Abstract

Alzheimer’s Disease (AD) patients have consistently shown declines in declarative memory, consolidation, and in many other cognitive areas. These changes are associated with atrophy and volumetric declines in medial temporal lobe structures, such as the hippocampus. Hippocampal atrophy has been associated with AD. However, the influence of AD atrophy on the position of the uncal apex—an anatomical landmark for the hippocampus—has not been longitudinally examined. The current study’s objective is to investigate changes in the position of the uncal apex of AD patients over the course of two years. The current study draws upon the Alzheimer’s Disease Neuroimaging Initiative (ADNI) data set (adni.loni.usc.edu). For each participant, I obtained demographic data, anatomical MRI images in native space, hippocampal segmentations from the subcortical stream of FreeSurfer (v.5.3.0), and linear transforms to MNI space. Using uncal apex y-positions transformed in MNI space, I found that the uncal apex fell in a more posterior position in AD patients relative to control and that over time, the uncal apex migrates toward a more anterior position in both groups. These results suggest that part of the neuroimaging examinations that are done on AD patients should examine uncal apex positions as a biomarker of early AD progression. Future directions and limitations are discussed