- Toxoplasma encephalitis is more common than HIV encephalitis
- Toxoplasma is the most common opportunistic neuroinfection in AIDS
- Toxoplasma encephalitis preodominantly involves periventricular white matter
- The more the nodular or ring enhancement, the more is the CD count
- On an unenhanced CT scan, the lesions are usually hypodense
Answers: F, T, F, T, F
Notes: HIV encephalitis accounts for up to 60% with AIDS, where as toxoplasma encephalitis accounts for approximately 30% of cases. Toxoplamosis, being the most common opportunistic neuroinfection, may result in necrotising encephalitis, predominantly involving the basal ganglia and thalami. On Unenhcened CT, the lesions are usually isodense to grey matter, but may be hyperdense due to hemorrhage and on contrast, usually show ring or nodular enhancement. Faint or absent enhancement is seen if the CD count is less than 50 and the enhancement increases with increase in the CD count.
Regarding neuroinfections in HIV/AIDS,
- HIV encephalitis preferentially shows white matter changes in the centrum semiovale
- CMV encephalitis usually involves brain stem and periventricular white matter
- CMV encephalitis typically heals by periventricular calcifications
- Cryptococcus usually causes ring enhancing lesions in the basal ganglia
- PML (progressive multifocal leucoencephalopathy) typically shows mass effect and contrast enhancement
Answers: T, T, F, F, F
Notes: Demyelination and gliosis in HIV encephalitis affects deep white matter, preferentially involving the centrum semiovale. CMV cause meningoencephalitis with predominant involvement of periventricular white matter and brain stem, ventriculitis, infarcts, spinal cord, cranial nerves. CT may show diffuse white matter hypodensity and on contrast, may show ependymal, ring or nodular enhancement. Periventricular calcification is a sign of congenital CMV infection and not a feature of CMV infection in immunocompromised. Cryptococcus is the most common fungal infection in AIDS and typically causes meningitis. PML is caused by Gr B papovavirus and shows bilateral pathy white matter abnormality without mass effect or contrast enhancement.
