Figure 21a.

Patient with vascular dementia from a strategic left thalamic hemorrhagic infarct. (a–c) Axial T2-weighted fluid-attenuated inversion-recovery (FLAIR) (a), T2-weighted (b), and gradient-recalled-echo (c) MR images show encephalomalacia and hemosiderin staining in the left thalamus (arrow), compatible with a chronic hemorrhagic infarct. (d, e) Axial ¹⁸F-FDG PET images at the level of the thalami (d) and lateral ventricles (e) show nearly absent activity in the left thalamus (arrow in d) and decreased activity in the left cerebral hemisphere, respectively, when compared with the normal activity depicted in the right thalamus and right cerebral hemisphere. Corroborative findings are compatible with thalamic infarct and vascular dementia. (f) Coronal ¹⁸F-FDG PET image shows decreased activity (arrows) in the left cerebral hemisphere and right cerebellar hemisphere, compatible with crossed cerebellar diaschisis. This is secondary to wallerian degeneration of the white matter tracts, which decussate contralaterally. I = inferior, S = superior.