Examination of medial temporal atrophy measured on antemortem MRI in relation to postmortem neuropathology has shown that tau pathology was associated with posterior hippocampal atrophy, whereas TDP-43 pathology was associated with anterior medial temporal atrophy.6 Medial temporal atrophy, although a common characteristic, is not always observed in AD. This evidence concerns the gene MAPT and Alzheimer disease.