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CASE 2

37 year old male with history of AIDS, CD4 count of 64

Findings

Multifocal FLAIR hyperintensities predominating in the cerebellar white matter

Faint associated enhancement is present

Differential

Primary CNS Lymphoma (EBV)

Ring-enhancing lesions, surrounding edema

Multiple lesions 50%

Variable signal on T2; isointense or hypointense on T1

Basal Ganglia, deep white matter

More likely to cross corpus callosum or occur in periependymal areas than TE

Can be > 4cm

Toxoplasma encephalitis (T. Gondii)

Thin-walled ring-enhancing lesions, surrounding edema; rarely diffuse encephalitis

Multiple lesions 80%

Usually hyperintense with hypointense rim on T2 (can have decreased signal in central areas from calcium and hemorrhage)

Basal Ganglia, G/W junction; parietal, frontal, thalamus

PML (JC)

Multiple areas of demyelination, without contrast-enhancement or edema

Bilateral, asymmetric; hypointense on T1, hyperintense on T2

Can see atypical enhancing lesions with immune reconstitution syndrome

Periventricular and subcortical white matter (rarely grey matter)

HIV Encephalitis (HIV)

Indistinct lesions in subcortical white matter

Symmetric; hyperintense on T2

CMV Encephalitis (CMV)

Scattered micronodules in the cortex, BG, brain stem, and cerebellum; or

Large ventricles with periventricular enhancement/hyperintensity on T2; or

Ring-enhancing lesions with edema

Progressive Multifocal Leukoencephalopathy

Single or multiple confluent lesions without mass effect are seen most frequently in the parietooccipital white matter

CT

Hypodense lesions

Rare contrast enhancement

MRI

T1 images - Hypointense lesions

T2 images - Hyperintense lesions

Rare contrast enhancement

Occasional gray matter involvement with scalloped appearance

Progressive Multifocal Leukoencephalopathy

Widespread demyelinative lesions due to infection of oligodendrocytes by a human papovavirus

Reactivation of the endemic JC papovavirus

As many as 90% of healthy individuals have serum antibodies to this virus, but less than 10% show any evidence of ongoing viral replication

Occurs almost exclusively in immunosuppressed individuals, such as patients with AIDS, leukemia, or those undergoing organ transplants

Progressive Multifocal Leukoencephalopathy

PML progresses to severe dementia and death over several months

Survival exceeds 1 year in only 9%

This is more likely to happen when PML is the AIDS-defining event or when CD4 counts are relatively high

Approximately 8% of patients experience spontaneous recovery

CD4+ T-cell counts greater than 100/mL at baseline and the ability to maintain a viral load of less than 500 copies per mL are factors influencing a favorable outcome

Progressive Multifocal Leukoencephalopathy

Polymerase chain reaction (PCR) of the CSF has been shown to be 92-99% specific and 74-93% sensitive for the detection of JC virus in patients with PML

Brain biopsy has a specificity of 92-100% and sensitivity of 74-92%

Pathology

Treatment

All treatments are experimental

Treatment trials with cidofovir (used in AIDS patients with CMV), topotecan (topoisomerase inhibitor), and interferon alpha have been inconclusive

Recent studies provide evidence that patients with advanced HIV disease on HAART (Highly active antiretroviral therapy) survived an average of 46 weeks, while historical controls survived an average of only 11 weeks after the diagnosis of PML