Progressive multifocal leukoencephalopathy and human immunodeficiency virus-associated white matter lesions in AIDS: Magnetization transfer MR imaging

PURPOSE: To determine the magnetization transfer features of progressive mu ltifocal leukoencephalopathy (PML) and human immunodeficiency virus (HIV)-a ssociated white matter lesions(WML) (hereafter, HIV-WML) on magnetic resona nce (MR) images obtained in patients with acquired immunodeficiency syndrom e (AIDS). MATERIALS AND METHODS: Conventional MR imaging and magnetization transfer M R imaging were performed in 21 AIDS patients with 42 areas of white matter hyperintensity on MR images (13 patients had 25 PML lesions, eight patients had 17 WML). The magnetization transfer ratio was calculated for each lesi on. RESULTS: Compared with normal-appearing white matter (magnetization transfe r ratio = 47.9%), both PML and HIV-WML showed reduced magnetization transfe r ratio. The magnetization transfer ratio was significantly lower in PML le sions (magnetization transfer ratio = 26.1%) than in HIV-WML (magnetization transfer ratio = 38.0%, P < .0001), and there was no overlap in the magnet ization transfer ratio between PML lesions and HIV-WML. The separation in m agnetization transfer ratio between the two lesion types was valid for lesi ons as small as 0.5 cm(2). CONCLUSION: The larger reduction in magnetization transfer ratio for PML le sions is most likely due to demyelination, whereas the reduction in HIV-WML may be associated primarily with gliosis. ML lesions appear to cause stron g reductions in magnetization transfer ratio early in the course of disease . Magnetization transfer MR imaging is a noninvasive tool that improves the differentiation between PML and HIV-WML in patients with AIDS.