Figure 1 (A–C) Cerebral MRI at admission. (A, B) Fluid attenuated inversion recovery (FLAIR) weighted images showing pathological signal hyperintensities in the deep white matter of both hemispheres and the basal ganglia. (C) T1 weighted image with gadolinium (GD) application at the corresponding plane to B showing absence of contrast enhancement in the parenchyma with only an enhanced vessel. (D–F) Cerebral MRI 18 days later revealed a prominent increase in signal hyperintensities in FLAIR weighted images (D, E) now also involving the thalamus but still lacking contrast enhancement after GD (F). (G, H) Statistical parametric mapping analysis of cerebral fluor‐desoxy‐glucose‐positron emission tomography (FDG‐PET) at the planes corresponding to D and E showing increased FDG uptake (red) in the deep cerebral white matter. (I) Cerebral T1 weighted MRI 4 months later showing multiple nodular contrast enhancing lesions.