MR Imaging of BK Virus Encephalitis

A 38-year-old woman with hemorrhagic cystitis, generalized psychomotor slowing, and dysarthria 10 months after bone marrow transplantation for relapsing Hodgkin lymphoma.

A, Axial T2-weighted MR image shows symmetric hyperintensity in the globus pallidi, as well as the thalami and white matter.

B, More caudal axial T2-weighted MR image shows extensive hyperintensity in the cerebellum.

C, More rostral axial FLAIR-weighted MR image shows diffuse hyperintensity in the white matter; the cortex appears largely or completely spared.

D, Axial diffusion-weighted (b = 1000) MR image at a similar level to panel C shows mild to moderately restricted diffusion in the supratentorial white matter.

E, ADC map at the same level as panel D confirms the presence of restricted diffusion in the supratentorial white matter.

F, More caudal axial diffusion-weighted (b = 1000) MR image shows moderately restricted diffusion in the cerebellum; the deep cerebellar white matter appears relatively spared. Diffusion restriction was also identified in the globus pallidi (not shown).

G, ADC map at the same level as panel F confirms the presence of restricted diffusion in the cerebellum.

H, Axial T2-weighted MR image at a similar level as panel F shows extensive hyperintensity in the cerebellum.

I, Sagittal T1-weighted enhanced MR image shows generalized swelling and hypointensity of the cerebellum. The deep cerebellar white matter appears relatively spared. There is no abnormal enhancement of the visualized parenchyma.