HIV/AIDS and CNS Disease

Summary

  • Toxoplasmosis is most common
  • Less common: Cryptococcus, Primary CNS Lymphoma (~5% patients)
  • Rare: PML, tuberculosis
Lesion
Typical Cause / Organism
Imaging Features
CD4 Level
Notes / Clinical Clues
1. Toxoplasmosis (most common)
Toxoplasma gondii (reactivation)
- Multiple ring-enhancing lesions- Basal ganglia or corticomedullary junction- Surrounding edema, mass effect
<100 cells/µL
Fever, focal deficits, seizures. Improves with anti-toxoplasma therapy (pyrimethamine + sulfadiazine + leucovorin).
2. Primary CNS Lymphoma (PCNSL)
EBV-driven B-cell lymphoma
- Solitary or few ring-enhancing lesions- Often periventricular or corpus callosum- Thallium-201 SPECT positive- Restricted diffusion on MRI
<50 cells/µL
Often mistaken for toxo; diagnosis via biopsy or EBV DNA in CSF. Poor prognosis.
3. Progressive Multifocal Leukoencephalopathy (PML)
JC virus (polyomavirus)
- Non-enhancing white matter lesions- Asymmetric, multifocal- No mass effect
<200 cells/µL
No enhancement! Subacute deficits; not a true abscess.
4. Cryptococcal infection
Cryptococcus neoformans
- May cause gelatinous pseudocysts (non-enhancing) or meningeal enhancement
<100 cells/µL
Often with meningitis; India ink + cryptococcal antigen positive.
5. Tuberculoma
Mycobacterium tuberculosis
- Ring or nodular enhancement, variable- May calcify
Variable (<200 cells/µL)
Common in endemic areas.
6. CNS abscess (bacterial/fungal)
Nocardia, Listeria, Candida, Aspergillus
- Ring-enhancing lesions with restricted diffusion
<100 cells/µL
Nocardia: predilection for brain, often multiple. Aspergillus: angioinvasive.

Detailed Info

Progressive Multifocal Leukoencephalopathy (PML)

  • caused by JC virus infecting oligodendrocytes
  • progressive demyelination
  • 55-85% associated with HIV
  • also occurs in other immunocompromised states (CLL, lymphoma)
  • MRI:
    • hyperintense T2 lesions in white matter (spares gray matter)
    • no contrast enhancement