HIV Encephalitis Vs PML

* A 50 yo male with altered behavior and sensorium. Known Retro positive.On admission drowsy.

MRI Brain Axial FLAIR shows:
Diffuse cerebral cortical atrophy - significant for age. An associated ex vacuo dilatation of lateral ventricles and mid brain atrophy.
Faint ill defined T2 hyper intensity in fronto parietal peri ventricular white matter, bilateral and symmetrical involvement goes in favor of HIV Encephalitis.

* A 31 yo male with left side weakness.
On admission Tridot test positive.

MRI study of Brain shows:
Bilateral patchy ill defined parietal T2 hyper intensities, confined to white matter, peri ventricular as well as sub cortical white matter.
No mass effect.
High signal on Diffusion attributed to prolonged T2 effect, bilateral asymmetrical involvement goes in favor of PML.

HIV Encephalitis – Encephalopathy

Syn: HIV- 1 Encephalitis / Encephalopathy, HIVE.
A syndrome of cognitive, behavioural and motor abnormalities attributed to direct effect of HIV on brain, in absence of opportunistic infection.
Most freqauent neurological manifestation of HIV infection.
Atrophy with bilateral symmetric confluent peri ventricular white matter disease, hypodense on CT and T2 hyperintense on MRI is a diagnostic clue.
Clinical finding should guide imaging finding and not reverse.
Affect any age group and gender.

Progressive Multifocal Leukoencephalopathy (PML)

A sub acute progressive demyelinating disease.
Bad prognosis, even fatal.
Seen in patients with immune disorders particularly impaired cell mediated immune response. Predominantly occurs in patients with AIDS, in ~ 5% of patients with AIDS. Results from JC virus infection - genus Polyomavirus -  family Papovaviridae. Before AIDS epidemic, PML was rare and was associated with other immune compromised conditions like leukemia, lymphoma, organ transplantation and severe combined immunodeficiency (SCID).
Imaging findings:
MRI is the preferred imaging modality over CT.
Usually bilateral and asymmetrical involvement. Patchy and multifocal. Unilateral involvement uncommon.
Predominantly involve fronto parietal white matter; may involve periventricular white matte or sub cortical white matter or both.
On CT, ill defined patcy areas of low attenuation. No enhancement on post contrast.
On MR, ill defined patchy areas of T2 hyperintensity. May show high signal on diffusion due to prolonged T2 effect. No enhancement on post contrast T1.
An associated atrophy,  increase in confluence of lesions, increase in hypo intensity of lesion on T1,  involvement of corpus callosum are poor prognostic indicators.
Faint enhancement seen on post contrast T1 in follow up MRI of PML pts treated with Anti Retroviral Therapy is associated with increase in their CD4+ count, may indicate favourable prognosis.

HIV Encephalitis Vs PML

Imaging wise HIV Encephalitis - Encephalopathy  is usually characterised by bilateral symmetrical Periventricular T2 white matter hyperintensity, An associated diffuse cortical atrophy and ventricular dilatation which are not predominant findings of PML.
In PML involvement is usually bilateral, patchy and asymmetrical. Unilateral involvement is uncommon. Predominantly involve fronto parietal white matter.
Clinically HIV Enecephaltis pt present with altered cognition where as PML is associated progressive focal motor and sensory deficits.
HIV Encephalitis is attributed to direct effect of HIV on brain parenchyma where as PML is attributed to Demyelinating disease and opportunisting infection occurring in pts with advanced AIDS with severely impaired cell mediated immunity and CD 4 counts.

Similar cases:
Hiv-encephalitis-encephalopathy
PML