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PML

Caused by infection of oligodendrocytes with a papovavirus (JC virus)

Clinical presentation

Focal neurologic deficits, e.g. hemiparesis

Less common in primary HIV encephalopathy

Visual symptoms

Mental status changes

Differential Diagnosis

Demyelination related to CMV or HIV

Progressive multifocal leukoencephalopathy

Lymphoma

Clinical course

Rapidly progressive with continued neurologic decline

CNS demyelination

Death usually within 6-12 months from onset of symptoms

Imaging

CT: focal regions of hypodensity in white matter, without mass effect or enhancement

MRI: T2 signal hyperintensity

Predilection for subcortical white matter

Slight predilection for parietal and occipital white matter

MRI Imaging:

Single lesions

Multifocal lesions with bilateral but asymmetric distribution

Mass effect and/or enhancement uncommon

Less than 10% of cases

Usually hypointense on T1 images