VIII. Progressive Multifocal Leukoencephalopathy (PML)
A. Clinical features
Onset: occurs in patients with associated immune suppression or chronic disease, e.g. lymphoma, AIDS
Clinical presentation: The major consistent symptom is intellectual deterioration and dementia. Other symptoms include cortical visual symptoms, motor disorders, abnormal movements.
Duration: death usually in 2‑6 months
CSF findings: normal
Viral encephalitis caused by a polyomavirus. Because the virus preferentially infects oligodendrocytes, demyelination is its principal pathologic effect.