G. HIV-ASSOCIATED CNS DISORDERS
-- CNS involvement may occur due to primary effects of HIV infection
or to secondary effects of immune suppression
1. General Issues
2. Pathologic Changes due directly to HIV infection (subacute encephalitis)
- Between 10 and 20% of HIV-infected patients present with neurologic
signs as their first clinical manifestation of infection. In some, no other
signs of AIDS develop. Between 50 and 70% of all AIDS patients eventually
develop some features of what is called AIDS dementia or the AIDS
related cognitive-motor complex. This term is used to describe the characteristic
pattern of cognitive, motor, and behavioral dysfunction, including mood
disturbances, seen in AIDS patients. At autopsy, between 60 and 90%
of AIDS patients' brains show some form of pathology.
3. Secondary Effects of Immune Suppression
- a. The pathology associated with the AIDS-related cognitive-motor
complex, sometimes called subacute encephalitis, is located mainly in subcortical
areas, with relative sparing of cerebral cortex. Microscopic changes include:
- 1) diffuse white matter pallor
- 2) perivascular infiltrates of lymphocytes and macrophages
- 3) foci of necrosis, gliosis, and/or demyelination
- 4) microglial nodules, macrophages and multinucleated cells
- The virus enters the brain, probably primarily by way of macrophages,
as HIV has been localized in CNS, mainly in macrophages, microglia and multinucleated
giant cells. The virus is able to reproduce in the brain.
- b. Vacuolar myelopathy is sometimes seen in the spinal cord.
This change consists of white matter vacuolation in posterior and lateral
columns, and is mainly due to swelling within mhyelin sheaths.
- a. Opportunistic infections. In addition to HIV infection,
opportunistic viral infection of the brain is a relatively frequent complication
of HIV-related immunosuppression. A variety of viruses and fungi, have been
- These infecting agents can be isolated from the brains of about 25%
of AIDS patients.
- b. Other secondary effects include increased incidence of primary
CNS lymphoma and progressive multifocal leukoencephalopathy (PML) -- see
4. Peripheral Nervous System Pathology
- a. PNS damage is seen in some HIV-infected patients. Inflammatory
demyelinating neuropathy is the primary PNS pathology.