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Acquired HIV Encephalitis


KEY FACTS

Terminology

  • HIV-1 encephalitis/HIV-1 encephalopathy

  • HIV-associated neurocognitive disorders

Imaging

  • CT

    • Atrophy

    • Bilateral periventricular/diffuse WM hypointensities

    • Basal ganglia, cerebellum, brainstem hypodensity

  • MR

    • Diffuse “hazy” hyperintense WM on T2/FLAIR

    • Nonenhancing (if enhancement present, consider opportunistic infections, immune reconstitution inflammatory syndrome)

Pathology

  • HIV has ability to cause neurologic disease

    • Does not replicate within neural/glial cells

    • Microglial nodules with multinucleated giant cells

  • WM pallor early, neocortical infection/atrophy late

Clinical Issues

  • Moderate cognitive impairment common despite good virologic response to therapy

  • Direct HIV infection of brain

    • Opportunistic infections absent

    • Cognitive, behavioral, motor abnormalities in 25-70%

    • Most frequent neurological manifestation of HIV infection

Diagnostic Checklist

  • Evidence of “cerebral atrophy” by CT/MR does not indicate AIDS dementia complex in HIV-positive patient

  • Consider reversible causes 1st (dehydration, malnutrition, protein depletion, alcoholism)

Sagittal T1WI MR in a 35-year-old man with HIV shows generalized atrophy, enlarged sulci
, and severe atrophy of the corpus callosum
.

Axial FLAIR MR in the same patient shows enlarged ventricles
and sylvian fissures
due to diffuse atrophy. There are hazy periventricular white matter hyperintensities
. These imaging findings are characteristic of HIV encephalitis.

Axial NECT in a 38-year-old man with longstanding HIV/AIDS, who was receiving HAART, was obtained for decreasing cognitive function. Note the gross atrophy and low density
within the subcortical white matter.

Axial NECT in the same patient shows characteristic low density in the periventricular white matter
along with diffusely enlarged sulci and lateral ventricles.

TERMINOLOGY

Definitions

  • HIV-1 encephalitis/encephalopathy (HIVE)

  • Direct HIV infection of brain

    • Opportunistic infections absent

    • Cognitive, behavioral, motor abnormalities in 25-70%

    • HIV-associated neurocognitive disorders (HAND) = most frequent neurological manifestations of HIV infection

  • Moderate cognitive impairment common despite good virologic response to therapy

IMAGING

General Features

  • Best diagnostic clue

    • Atrophy + bilateral diffuse white matter (WM) abnormalities

      • –

        Pathology/imaging varies with patient age, acuity of onset

  • Location

    • Bilateral periventricular/centrum semiovale WM, basal ganglia, cerebellum, brainstem

  • Size

    • Variable, often diffuse

  • Morphology

    • Extends to gray-white matter junction

CT Findings

  • NECT

    • Children: Atrophy and diffuse WM hypodensity

      • –

        In utero HIV infection: Characteristic bilateral and symmetrical calcifications in basal ganglia and frontal WM with eventual contrast enhancement

    • Adults: Normal or mild atrophy, WM hypodensity

    • No mass effect

  • CECT

    • Usually no contrast enhancement

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