MR Imaging of BK virus encephalitis

Abstract

BK virus infection is most often associated with urologic disease in patients who have undergone renal or bone marrow transplantation. We report a rare case of biopsy-confirmed BK virus encephalitis in an immunocompromised patient with hemorrhagic cystitis, in whom dramatic imaging findings were present despite relatively mild clinical symptoms. MR imaging demonstrated widespread increased signal intensity on T2- and fluid-attenuated inversion recovery-weighted images, with restricted diffusion, in the cerebellum, cerebral white matter, and deep gray matter structures. The simultaneous presence of urologic abnormalities and neurologic deficits in certain immunocompromised patients should prompt consideration of BK virus encephalitis.

Fig 1.

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.