Diagnosis
PML is diagnosed by testing for JC virus DNA in cerebrospinal fluid or in a brain biopsy specimen. Characteristic evidence of the damage caused by PML in the brain can also be detected on MRI images, which classically show multifocal nonenhancing lesions without mass effect. The most common area of involvement is the cortical white matter, but the brainstem and cerebellum may also be involved.
Read more about this topic: Progressive Multifocal Leukoencephalopathy