Two cases of non–prion-related rapidly progressive dementia or ataxia syndromes. Note that in these cases, the abnormalities are best seen in FLAIR images. (A,B) A 66-year-old man with intravascular lymphoma. (B) FLAIR multifocal abnormalities involving cerebral and cerebellar gray and white matter in a vascular distribution. These lesions, also involving the right hippocampus, showed patchy enhancement after contrast administration (not shown). (A) DWI shows a right periventricular focal region with diffusion restriction; DWI hyperintensity is common in lymphomas. (C,D) A 65-year-old woman with anti-Yo paraneoplastic cerebellitis. MRI shows mild diffuse hyperintensity of the cerebellar, compared with the cerebral, cortex with slight atrophy of the lateral folia. Note (D) the strong hyperintense FLAIR signal in superior, medial cerebellum (arrows), and (C) no major hyperintensity in the axial DWI scan. (E,F) A 60-year-old woman with paraneoplastic limbic encephalitis and FLAIR MRI showing hyperintensity of bilateral insula, medial (arrows) and inferior temporal cortex, hippocampus, amygdala (F) on FLAIR and only subtle hyperintensity (E) on DWI. FLAIR, fluid-attenuated inversion recovery; DWI, diffusion-weighted imaging; MRI, magnetic resonance imaging.