Progressive Multifocal Leukoencephalopathy (PML) is a life-threatening demyelinating condition that results from the reactivation of the polyomavirus JC. It primarily affects the immunocompromised (most commonly individuals with CD4 counts of < 200).
Prior to the advent and widespread use of anti-retroviral therapy, 1 to 5% of those with AIDS developed PML. HAART is now considered a mainstay of treatment, along with cessation of immunosupressant therapies.
PML lesions typically occur bilaterally in the peri-ventricular white matter portions of the brain and do not conform to specific cerebrovascular territories.
Non-contrast CT and MRI may reveal PML lesions, but definitive diagnosis is made via brain biopsy.
Symptoms of PML include subacute neurologic deficitssuch as: mental status abnormality, gait ataxia, limb ataxia, hemiparesis, monoparesis, and visual abnormalities such as diplopia and hemianopia. Seizure occurs in up to 18% of cases.