Computed tomography and magnetic resonance imaging of the brain in the axial plane. (A) Non-enhanced computed tomography images of the head showing diffuse leukoencephalopathy involving the frontal, parietal and temporal lobes with relative sparing of the cortex. Brain magnetic resonance imaging showed extensive white-matter abnormality throughout both hemispheres, greatest in the superior convexities, consisting of numerous collections of cystic spaces on T2-weighted (B) and fluid-attenuated inversion recovery (C) images. The spaces have smooth margins and are roughly elongated parallel to the expected direction of the vascular and radial fibers, suggestive of tumefactive perivascular spaces. Many of the spaces have adjacent T2-weighted and fluid-attenuated inversion recovery parenchymal hyperintensity. There was no enhancement after gadolinium contrast administration (D).