Progressive multifocal leukoencephalopathy (PML) is a subacute demyelinating disease caused by an opportunistic polyomavirus,named JC virus according to the initials of the patient from whose brain it was initially isolated. It typically occurs in patients with defective cell-mediated immunity. Those with lymphomas, leukemias, and drug-induced immunosuppression used to be the primary targets, but more recently AIDS has become the most common clinical setting.

PML is characterized by the presence of multiple (in part confluent) areas of CNS demyelination, primarily in subcortical white matter. As the disease progresses, the demyelinated plaques coalesce to form large lesions. The onset is subacute to chronic.


Clinical manifestations are diverse and related to lesion location and size. Focal and generalized seizures are an infrequent complication.

CSF is usually normal. The EEG often demonstrates nonspecific diffuse slowing. CT and MRI reveal white-matter abnormalities.


There is no definitive treatment. Seizure management, if needed, is routine.96

Adapted from: Goldstein MA and Harden CL. Infectious states. In: Ettinger AB and Devinsky O, eds. Managing epilepsy and co-existing disorders. Boston: Butterworth-Heinemann; 2002;83-133.
With permission from Elsevier (

Authored By: 
MA Goldstein
Cynthia L. Harden MD
Steven C. Schachter, MD
Authored Date: 
Reviewed By: 
Steven C. Schachter, MD
Monday, March 1, 2004