Figure 14b.

Alzheimer disease. (a) Sagittal T1-weighted MR image in a patient with memory loss shows disproportionate moderate volume loss in the precuneus (arrow), a finding suspicious for Alzheimer disease. The remainder of the brain parenchymal volume is relatively preserved. (b) Sagittal ¹⁸F-FDG PET image shows corresponding decreased activity in the precuneus (arrow). Image inset shows a coronal section through the middle of the brain in this particular case to aid in lateralization. Normal uptake is depicted in the frontal and occipital regions, reinforcing the diagnosis of Alzheimer disease.