Results from recent studies indicate that brain injury is common in people with HIV, particularly in late-stage HIV-infected patients. In addition, lower CD4 counts and older age are linked to lower brain functioning.
Studies also show that computerized assessments can be useful for detecting cognitive impairment, but that several simple screening tools are not effective in detecting HIV-associated neurocognitive disorders.
These studies were presented last week at the 2011 Conference on Retroviruses and Opportunistic Infections (CROI) in Boston and are summarized in this article.
People with HIV and AIDS commonly experience neurological problems that can lead to a decline in brain function. Some of the more common conditions associated with HIV include dementia, inflammation of the brain, cancers of the central nervous system, and decline in cognitive function (overall brain function and ability to think).
With the advent of highly active antiretroviral therapy (HAART), many of the most severe forms of brain injury associated with HIV are less common. However, rates of milder forms of brain impairment have not decreased with HAART and still affect around half of people with HIV.
In many cases, patients may not even realize their brains have been affected, since symptoms may be unnoticeable without specialized testing.
There are no specific treatments for HIV-associated neurological injuries. HIV patients are usually aggressively treated with antiretroviral therapy to prevent the replication of HIV in the body, which helps keep patients healthier and avoid certain infections.
Recent research has focused on determining how and why neurological injury occurs in people with HIV and how it can be more easily detected by patients’ physicians.
Neural Injury Is Common In Late-Stage HIV Disease And Is Linked To Low CD4 Count
In a small Swedish study, researchers measured the rate of neural injury in HIV-infected patients with no symptoms of neural problems and found that neural injury was very common in participants with low CD4 (white blood cell) counts.
Neural injury is damage to the nerves of the brain or nervous system. It can be caused by trauma or disease and can be mild or severe.
The researchers measured the amount of a certain brain protein in participants’ cerebrospinal fluid, the fluid that surrounds the brain and spinal cord. According to the researchers, previous studies have linked high levels of this protein to neural injury caused by HIV-associated dementia and central nervous system infections.
The study included 114 HIV-positive adults who were not undergoing treatment for HIV infection.
Results showed that higher protein levels were associated with late-stage HIV infection. Seventy nine percent of participants with CD4 (white blood cell) counts less than 50 had high protein levels, compared to 21 percent of participants with CD4 cell counts between 50 and 199, 17 percent of participants with CD4 counts between 200 and 349, and 7 percent of participants with CD4 counts above 350 cells per microliter of blood.
Results also indicated that high protein levels were associated with markers of inflammation in the central nervous system. There was no link to the amount of HIV present in the cerebrospinal fluid.
Low CD4 Count And Older Age Are Associated With Lower Neurocognitive Performance
Researchers in a second study examined brain function of HIV-positive adults with no symptoms of neural impairment to measure the effects of antiretroviral therapy, CD4 count, and other factors. Results showed that low CD4 counts, as well as older age, were linked to poor cognitive function.
The study included 101 participants who were on stable antiretroviral therapy regimens and had undetectable amounts of HIV in the blood for at least the previous three months.
The researchers evaluated the brain function of study participants by measuring their neurocognitive speed, accuracy, and thinking abilities with a computerized neurocognitive testing program.
Results showed that 19 percent of participants demonstrated neurocognitive impairment, as determined by abnormally low scores in at least two of the three categories.
Results also showed that poor brain function was associated with lower CD4 cell counts and older age. Degree of impairment was not linked to the type of antiretrovirals a participant used or how effectively the drugs crossed into the central nervous system.
Computer-Based Assessment Of Mild Cognitive Impairment May Be Useful For Detecting Cognitive Impairment
Results from a third, small study found that a computerized assessment for mild cognitive impairment gave similar results as a more traditional, time-intensive method of assessment.
Usually mild impairment is diagnosed using a battery of neurological tests that take two to five hours to complete. Shorter or automated tests would be easier for clinicians to administer and could be given to more patients.
The study included 60 participants, half of whom had HIV. Researchers assessed the cognitive ability of each participant using a detailed neurological evaluation and compared results with the Computer-based Assessment of Mild Cognitive Impairment (CAMCI). CAMCI is a computerized assessment tool developed by researchers at the University of Pittsburgh.
Results showed that scores from a visual memory test in CAMCI matched well with the traditional cognitive assessment results. There was no difference in CAMCI’s ability to detect impairment for HIV-positive versus HIV-negative participants.
The researchers suggested that as a result, CAMCI may be useful in detecting cognitive impairment in people with HIV. However, they noted that the study was small and further studies are necessary to fully evaluate the effectiveness of the computerized assessment.
Simpler Screening Tools Fail To Detect Cognitive Impairment In People With HIV
Researchers in a final study evaluated the usefulness of two simple screening tests to identify people with neurocognitive disorders. Results showed that neither test was sensitive enough to accurately diagnose mild impairment in people with HIV.
The study included 58 HIV-positive adults who were taking antiretroviral therapy and had undetectable viral loads (amount of HIV in the blood).
All participants were screened for mild cognitive impairment using three different methods: a traditional, time-intensive neurological screen; the Montreal Cognitive Assessment (MCA), a simple screening test for minor impairment developed in Canada; and the AD-8, a test designed to detect Alzheimer’s disease.
Results from the traditional neurological screen showed that 59 percent of participants had minor cognitive impairment. Results for the MCA and AD-8 were similar, at 52 percent and 47 percent of participants, respectively.
However, analysis showed that the MCA and AD-8 only correctly identified 65 percent and 62 percent of participants with impairment, respectively, and 79 percent and 63 percent of participants who did not have impairment.
As a result, the researchers concluded that the tests were not as sensitive as traditional measures for impairment. However, they suggested the tests may be more useful in HIV-positive patients with mild symptoms of neural disease rather than patients with no symptoms. By Meerat Oza and Courtney McQueen
For more information, please see the CROI 2011 website.
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