The Neurological Impacts of HIV
- Reviewed21 Aug 2023
- Author Gail Zyla
- Source BrainFacts/SfN
The first verified case of the human immunodeficiency virus (HIV), the virus that causes acquired immune deficiency syndrome (AIDS), was found in a person’s blood sample taken in 1959. The virus spread across the globe, which led to a public health epidemic in the 1980s — and by 1999, it was the fourth largest cause of death in the world. Since then, new medications have been developed to help prevent the initial contraction of HIV, lower the risk of transmission, and reduce some of the neurological complications associated with the virus.
*Currently, an estimated 39 million people worldwide live with HIV. The majority live in eastern and southern Africa, and an estimated 14% of people living with HIV are unaware that they are infected with the virus. From 2010 to 2022, the estimated number of new HIV diagnoses around the world fell by 38% from 2.2 million to 1.3 million, possibly due to targeted prevention efforts. Globally, the number of people receiving treatment for HIV has increased dramatically in recent years, particularly in developing countries. In 2022, 29.8 million people living with HIV (76% of those worldwide with HIV) were receiving life-prolonging antiretroviral therapy (ART). In 2010, only 7.7 million people were receiving this treatment.
HIV is transmitted through bodily fluids such as blood, semen, vaginal fluids, anal fluids, and breast milk. The virus attacks the immune system, specifically T cells — a type of white blood cell that helps protect the body from infection. Over time, it can destroy so many T cells that the body can’t fight off infections and diseases, eventually leading to the most severe form of an HIV infection: AIDS.
Although HIV targets the immune system, the nervous system can also be affected. HIV does not directly invade neurons, but it puts their function at risk by infecting resident immune cells in the brain like microglia. HIV also triggers inflammation that can damage the brain and spinal cord. Around half of people with HIV also develop HIV-associated neurocognitive disorders (HAND). HAND symptoms range from mild difficulty with concentration, memory, coordination, and complex decision-making to progressive dementia, called HIV-associated dementia. Even people who receive antiretroviral treatments can develop mild symptoms of HAND; however, the treatment may help prevent or even reverse mild to severe HAND symptoms in many people.
Mild forms of HAND have been reported in people with HIV infection who have no other symptoms. In advanced disease, people can develop increasing problems with concentration and memory as well as an overall slowing of mental processes. At the same time, they might experience arm or leg weakness and loss of balance, coordination, and dexterity. MRI and CT scans show brain shrinkage in people with HAND. Examination of the brains of people who die with AIDS sometimes reveals loss of nerve cells, white matter abnormalities, and damage to cellular structures involved in cell-to-cell communication. Inflammation and blood vessel disease can also be present.
Another neurological problem common in people with HIV is peripheral neuropathy. Peripheral neuropathy involves injury to the nerves of the extremities and causes discomfort ranging from tingling and burning to severe pain. Inflammation from HIV can trigger the injury, and certain ARTs can cause the neuropathies or make them more frequent and severe. About a third of people with advanced AIDS have neuropathy.
Despite remarkable advances in new therapies, AIDS cannot be cured, and some of its neurological problems do not respond to treatment. Fortunately, combination ARTs, using three or more drugs to treat HIV and stop the virus from multiplying, can reduce the incidence of HIV transmission and severe HAND symptoms. These treatments can also improve cognitive performance and brain connectivity compared to those who have HIV and aren’t on ART. And importantly, pre-exposure prophylaxis (PrEP) medications have provided a means for prevention against initial contraction of HIV for those at-risk of contact with the virus.
*This paragraph was updated August 21, 2023 with the latest UNAIDS figures for HIV incidence, prevalence, and treatment.
Adapted from the 8th edition of Brain Facts by Gail Zyla.
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