Stereotactic brain biopsy for diagnosis of progressive multifocal leukoencephalopathy.

We describe three patients in whom the diagnosis of progressive multifocal leukoencephalopathy (PML) was made by stereotactic biopsy. All three patients had a rapidly progressive clinical course pathologically characterized by demyelination, Alzheimer I astrocytes, and basophilic intranuclear inclusions in oligodendrocytes. In each case, the diagnosis was confirmed with immunohistochemical staining of oligodendrocytes for the JC virus and in one case by electron microscopy. Determination of the adequacy of tissue received at the time of frozen section is critical and can direct the appropriate submission of tissue to maximize available diagnostic procedures.