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Progressive Multifocal Leukoencephalopathy

Last Updated: October 1, 2018

Progressive Multifocal Leukoencephalopathy (PML) is the infection of myelin-producing oligodendrocytes by reactivated JC virus due to immunodeficiency, particularly in AIDS patients when the CD4+ cell count falls below 100 cells/µl. 90% of patients die of the disease within 1 year of diagnosis.

Imaging Features

PML shares similarities to other demyelinating diseases – including the presence of a leading edge enhancement and restricted diffusion, its predominantly white matter distribution, and central edema. The distribution of PML is classically asymmetric (while HIV encephalitis is classically symmetric). Though PML may involve most areas of the brain, common locations include subcortical white matter (often frontoparietal) and thalami, progressing to involve more and more areas of the brain in a confluent and often multifocal pattern.

  • CT:
    • Asymmetric focal low-density lesions in the periventricular and subcortical white matter.
  • MRI:

    • T1: Low signal intensity, often quite striking.
    • T2/FLAIR: High signal focal white matter lesions.
    • SWI/GRE: Usually normal. Minimal hemorrhage is sometim...