Progressive multifocal leukoencephalopathy: a rare cause of cerebellar edema and atypical mass effect. A case report.

Progressive multifocal leukoencephalopathy (PML) is an opportunistic demyelinating disease of the CNS caused by the JC papovavirus (JCV). Demyelination due to oligodendrocyte death leads to multifocal, asymmetric lesions. MRI is a valuable tool for detecting and differentiating PML from other neuropathies.