AIDS patient with progressive multifocal leukoencephalopathy (PML)

There is a focal area of low density on CT scan (A) which involves the right periventricular white matter and extends peripherally to involve the subcortical white matter. MRI of same patient shows the lesion to be hyperintense on T2-weighted (B) and FLAIR (C) images, without contrast enhancement on post-contrast T1-weighted image (D). Diffusion-weighted image (E) shows increased signal intensity with a more hyperintense ring along the periphery, or advancing edge of the lesion. MR Spectroscopy of this lesion (F) shows that this lesion has characteristic decreased NAA, increased MI, increased choline, and elevated lactate/lipid peaks. (Refer to Izano et al).