Neuropathology of AIDS :: Health Medicine Medical Diseases Essays

Neuropathology of AIDS Since its discovery in 1981, AIDS has mainly been characterized as a disease effecting the bodying immune system. It has been recognized, however, that there are distinct neurological pathologies associated with the disease. AIDS neuropathology can be characterized by the existence of subcortical dementia, motor difficulties, and affective disorders. Most AIDS patients experience dementia of one form or another. It has been observed that approximately 95% of AIDS patients brain’s show signs of damage, and 60% of patients develop dementia of one degree or another. The AIDS virus is an RNA retrovirus which attaches to and infects T helper cells and other cells of the immune system. The virus normally goes through a typical lytic life cycle which is seen in the pathology of most viruses. Originally the HIV virus was associated wilt the CD4 receptor found on the immune cells, but it has been discovered that the OKT4 receptor is also a site of entry for the virus. This receptor is not only present in macrophages, but it is also found in glial cells of the CNS. There are basically three sites of entry where the HIV virus and infected macrophages can invade the CNS. The first is the blood brain barrier. If there is damage to the integrity of this barrier, the virus can easily pass into the brain tissue and proliferate. The second barrier is the blood CSF barrier. The choroid plexus males up this particular barrier, and the barrier is maintained by the existence of tight junctions. If there is a breakdown of these tight junctions, infected macrophages can pass from the blood into the CSF where they can pass to nearly any area of the CNS. The final site of entry, and perhaps the most likely' are the cicumventricular organs. This is the only site in the CNS where there is an absence of a barrier, and the macrophages carrying the virus are free to pass through these. From here the virus can spread almost anywhere in the CNS, but they intend to infect areas near their site of entry. The most common initial symptom seen in neurological disorders related to AIDS is subcortical dementia. The cardinal feature of subcortical dementia include slowing of mental processes, progressive impairment of memory, and deficits in manipulating or using spontaneously acquired information (i.e., poor problem solving). However, unlike the cortical dementias, higher-order associative function is preserved' and intellectual impairment is milder in the subcortical dementias.