AIDS-Related Brain Damage Unexplained

Recent research indicates that the retrovirus that causes acquired immunodeficiency syndrome (AIDS) attacks specific brain regions and cell types. Through use of a staining procedure which marks different cell types within a multinucleated giant cell and in situ hybridization a technique that detects AIDS viral nucleic acid the cell types in the brain infected by the AIDS virus have been more precisely identified. 95% of the virus is in multinucleated giant cells and most of the cells fused within these clumps are derived from macrophages. Also found has been damage to the gray matter deep within the brain particularly the basal ganglia and thalamus. About 10% of AIDS patients present 1st with neurologic symptoms including dementia neuropathy or opportunistic infections of the central nervous system and up to 60% eventually develop dementia. The brain of an AIDS patient is typically shrunken and the ventricles are larger than normal because of the atrophy. Accompanying the atrophy are lesions confined primarily to white matter of the brain. Another white matter abnormality called vacuolar myelopathy affects the spinal cord and contributes to the weakness and motor disturbances experienced by many AIDS patients. Researchers are still unclear about how the AIDS virus causes these changes. It has been suggested that macrophages infected by the retrovirus may secrete a toxic substance that is undetectable in brain scans or histologic sections. It also remains to be determined how the AIDS virus enters the brain. An ongoing debate among researchers concerns whether or not the AIDS virus is neurotropic and attacks brain cells specifically.