Researchers from the San Francisco Veterans Affairs Medical Center and the University of California, San Francisco, have discovered significant HIV-related brain damage in HIV-positive patients taking antiretroviral medications, even when they had suppressed blood-based viral loads to undetectable levels. Their study, appearing in the November 14 edition of the journal NeuroReport, used a combination of magnetic resonance imaging of the brain, recording of electrical brain activity, and behavioral tests to compare the size and functions of brains of HIV-positive patients taking anti-HIV drugs with HIV-negative adults. The study found a significant difference in brain wave recordings between HIV-negative and HIV-positive study subjects, including both patients who had suppressed viral replication through anti-HIV drugs and those who had higher viral loads because they were not taking antiretroviral medications. MRI exams also showed in the brains of all HIV-positive study subjects reduced volume of the caudate nuclei, a substructure of the basal ganglia where HIV tends to collect. The MRIs also showed that the area of the brain called the thalamus also was smaller in HIV-positive study subjects, suggesting HIV-related damage there as well.
Although the study could not determine if any or all of the brain damage occurred after the subjects started taking anti-HIV drugs, it's possible that HIV can still damage brain tissue even when viral replication is completely suppressed in the bloodstream, the researchers wrote. The study results also should serve as a warning to members of at-risk populations who may be becoming complacent about AIDS because of the touted successes of antiretroviral therapy, said lead study author Linda Chao. "You see people on antiretroviral medications and they seem fine," she said. "But the take-home message of our study is that antiviral medications might not be stopping brain damage. When we put patients' brains under closer scrutiny, we saw that they were affected."
HIV can cause problems throughout the nervous system, including the brain. Common neurological complications of HIV disease include depression, memory loss, sluggish limb movements, a slowing of physical and mental response times, and even dementia in severe cases. Before the advent of antiretroviral therapy, about 20% of AIDS patients suffered from HIV-related dementia. The incidence of HIV-related dementia has dropped considerably since anti-HIV drug cocktails became available in the late 1990s, but many researchers believed the virus, which can cross the blood-brain barrier, still caused damage to brain tissue over time, which prompted the current study. Follow-up studies are planned.