[Neuroradiological study of progressive multifocal leukoencephalopathy associated with acquired immunodeficiency syndrome by MR imaging including diffusion-weighted imaging].

A 27-year-old man presented with subacute progressive left hemiparesis and hemi-sensory loss. Laboratory examinations revealed CD4 count at 14/microl, the HIV antibody positive, and HIV-RNA at 4.3 x 10(4) copies. Brain CT showed hypodence areas without contrast enhancement or mass effect in the right parietooccipital white matter and the right external capsule. On MR imaging, the lesion in the parietooccipital area showed hypointensity without enhancement on T1-weighted images and hyperintensity on T2-weighted images. On FLAIR images, the lesion showed hypointensity surrounded by hyperintensity. Meanwhile, diffusion-weighted images revealed three layers of different intensity. The area that demonstrated hypointensity on FLAIR images showed also hypointensity, while that in the area that demonstrated hyperintensity on FLAIR was divided into two parts; an area of isointense that encircles an hypointense area and a hyperintense area in the margin. The isointense and hypointense areas on diffusion-weighted images showed hyperintensity on apparent diffusion coefficient map. As JCV DNA was detected from his CSF, the diagnosis of PML was made. Based on comparative assessment of these MR images, it was speculated that the PML lesion appeared to be constituted of three parts from the margin to the center: cytotoxic edema, vasogenic edema, and liquefied lesion such as necrosis.