The Truth About AIDS Dementia Essay, Research Paper
The Truth About AIDS Dementia
The Bare Facts
Most people have heard of AIDS; they know it stands for Acquired Immune Deficiency Syndrome, and it’s the result of the Human Immunodeficiency Virus (HIV). The virus attacks the body’s immune system, rendering an individual incapable of fending off bacteria and viruses that the immune system could normally destroy. And most people have heard of dementia, a condition where an individual has difficulty concentrating and remembering things. But the average American does not know much about AIDS dementia. AIDS dementia is a complication of HIV infection; it’s basically dementia caused by HIV, and it’s present in a number of HIV positive people. The effects of AIDS dementia do not surface for a number of years until after one has had a serious bout with AIDS. But once the symptoms appear, the effects can devastate.
It’s estimated that 10 to 30 percent of HIV positive people have some degree of AIDS dementia (3). The symptoms of AIDS dementia range from mild memory loss to seizures-the same symptoms any type of dementia sufferer would display. The symptoms appear gradually, but grow worse with time. Besides the behavioral changes associated with AIDS dementia, there are also physical, detectable changes in the brain. The total volume of the brain decreases because portions of the brain atrophy (7). Autopsies of individuals who suffered from AIDS dementia reveal a general atrophy of the brain, especially in the basal ganglia, the region of the brain that controls some motor and cognitive functions (4). AIDS dementia sufferers tend to have a lower nerve cell count and a higher concentration of cerebral spinal fluid (5). The preceding physical changes can all be monitored using some type of medical imaging device.
The Machines
The differences between the brains of patients with AIDS dementia and normal brains can be scanned using the following imaging mechanisms: computed tomography (CT), magnetic resonance imaging (MRI), and single photon/positron emission computed tomography (SPECT/PET). CT scans involve passing an X-ray through the brain at different angles. The attenuation of the X-rays enables sensitive receptors to determine the density of the tissue, and since the atrophied parts of the brain have a smaller density, this shows up on the image. MRI involves the use of magnets to stimulate protons to receive and transmit electromagnetic energy, which can then construct an image. With SPECT and PET scans, a radiolabeled molecule, like glucose, is injected into the body, and scanners detect where the radioactive elements are in the brain. Glucose powers the brain, so active areas of the brain use more glucose than inactive areas, therefore the scans will show images of the active areas of the brain. In AIDS dementia patients, the atrophied regions of the brain will not show up at all in the image because those areas would not use any glucose (6). All three of the medical imaging devices are useful in identifying an AIDS dementia patient.
The Pathway of the Pathogen
The mechanism by which HIV causes the atrophy of the brain is still unclear. Patients with AIDS dementia tend to have a lower number of nerve cells than average, leading some researchers to suspect that the HIV stimulates apoptosis of the nerve cells. Apoptosis is a cell suicide program; macrophages and microglia, cells of the immune system, become “activated” when infected by certain strains of HIV. The macrophages and microglia would then release toxins that kill off nerve cells, and the reduced number of nerve cells leads to dementia (4). This method is believed to be identical to the way HIV attacks the cells of the immune system; attack a cell, and cause it kill other cells.
Predictions?
New research indicates that it may be possible to identify individuals who will develop AIDS dementia, but who have not shown the symptoms yet. Autopsies revealed that ninety percent of people with AIDS have some type of pathological change in the brain, but only 10 to 30 percent of people with AIDS are diagnosed with AIDS dementia (3). This research indicates that the symptoms of AIDS dementia are only apparent when the atrophy of the brain has gone far enough to warrant a behavioral change; a slight physical change precedes any behavioral change, and since medical imaging allows physicians to see the changes in the brain, it may be possible to diagnose a patient with AIDS dementia before the symptoms are apparent.
Treatment
Once the problem is identified, the patient may be treated with a number of drugs to slow down the development of AIDS dementia. The drug AZT, which has already been shown to slow down the development of AIDS, has also been shown to slow the onslaught of AIDS dementia, although AZT-resistant strains of the virus exist (4). There are other more unconventional drugs such as Memantine and Atevirdine that are currently being tested that may prove to slow AIDS dementia (1,2). The precise mechanisms of such drugs are not yet understood, but their effects are observed to note any change in the development of AIDS dementia.
If HIV causes apoptosis of the nervous system, then it may be possible to completely stop the spread of AIDS dementia in an individual. Researchers have identified drugs that can block certain parts of the apoptosis process, thus preventing the loss of so many nerve cells. Only further testing and more research determine if such drugs may someday be used as a treatment for AIDS dementia.
Why Image?
There are research-based as well as life-determining reasons for imaging AIDS dementia. If scans of the developing disease were taken, the data gathered might aid researchers in developing a better understanding of HIV. Progressive scans would show where, when, and possibly how the virus spreads into the nervous system. With the information about how HIV attacks the nervous system, scientists may be able to formulate a better model for how HIV attacks the immune system. A better understanding of how the virus works would lead to an understanding of how to stop it, saving thousands of lives.
Although as of yet there is no cure for HIV, the quality of life of those who are HIV positive does not necessarily have to be all bad. People can live somewhat normal lives for years with HIV; the virus doesn’t automatically mean prolonged pain and instant death. AIDS dementia would detract from the quality of life that HIV positive individuals want. Imaging that could detect early signs of dementia, before the symptoms actually developed, might save precious time for treatment of the disease.
References
1. AIDS Dementia Complex (Therapy). B.J. Brew, et al. Obtained on 3/12/97. http://www.newsfile.com/112596ip.htm#A3
2. AIDS Dementia Complex Treatment. Author Unknown. Obtained on 3/12/97. http://sfghaids.ucsf.edu/aidstrials/trials/trial31543160.html
3. Being Alive Newsletter for August 1995: Understanding AIDS Dementia. Anne Cole. Obtained on 3/12/97. http://gopher.hivnet.org:70/0/magazines/alve/ba9508
4. The Harvard Mahoney Neuroscience Institute Letter On the Brain: Nerve Cell “Suicide” in AIDS Dementia. Dana Gabuzda, M.D. Obtained on 3/12/97. http://www.med.harvard.edu/publications/On_The_Brain/Volume5/Number1/AIDS.htm
5. Jama – HIV/AIDS Reuters Health News – 8/8/96: Markers for AIDS Dementia Complex Described. Author unknown. Obtained on 2/25/97. http://www.ama-assn.org/special/hiv/newsline/archive/0896/re080896.ht#markers
6. Neuroimaging Primer. Keith A. Johnson, M.D. Obtained on 3/12/97. http://www.med.harvard.edu/AANLIB/hms1.html
7. WBA Navigator: AIDS Dementia: Overlay – Image #10. Author Unknown. Obtained on 3/12/97. http://count51.med.harvard.edu/AANLIB/cases/case14/mr1-tc1/010.html