HIV-Associated Neurocognitive Disorders

HIV-Associated Dementia and Others

HIV-associated dementia. Getty Images Credit: Andrew Brookes

As its name suggests, the human immunodeficiency virus (HIV) infects the immune system. HIV particularly attacks immune cells called CD4 positive T-cells. As these cells die, the body becomes more prone to infections and cancers that healthy people would be able to fight off.

What some people don't realize is that the HIV virus itself can cause serious problems even without other infections getting involved. One of these problems is HIV-Associated Dementia (HAD), also known as HIV encephalopathy or AIDS dementia complex.

While it used to be thought that HAD only occurred in advanced HIV, we are now seeing it in people who have been otherwise stable on their medications and who have relatively high CD4 counts.

HIV-Associated Neurocognitive Disorders

The types of cognitive impairments associated with HIV exist on a spectrum of severity. When considered together, these types of impairments are referred to as HIV-Associated Neurocognitive Disorders.

The least severe form of HIV-associated Neurocognitive Disorder is asymptomatic neurocognitive impairment, in which someone scores poorly on an aspect of neuropsychological testing, but their life isn't noticeably impacted. If the person's life is impacted but not seriously, some clinicians will instead diagnose the patient with minor cognitive-motor disorder (MCMD).

If the problem is both detectable on neuropsychological testing and significantly interferes with daily life, a diagnosis can either be made of HIV-Associated Dementia.

Signs of HIV-Associated Dementia

Many people assume that HIV-Associated Dementia (HAD) will be similar to better-known forms of dementia such as Alzheimer's disease. This is not usually the case. While memory can be impaired as it can in Alzheimer's disease, people with HIV-Associated Dementia can also have difficulty concentrating or paying attention, which is not always seen in Alzheimer's disease. People with HIV-Associated Dementia are also slower than they would be, not just in thinking, but often in moving as well. In this way, dementia caused by HIV can mimic Parkinson's disease dementia (PDD).

People with HAD may also have changes in their mood such as apathy, where they lack motivation to do much of anything. As the disease progresses, they may become more irritable, and about 5 to 8 percent develop AIDS mania with psychotic features like paranoia and hallucinations.

The Cause of HAND

HIV enters the central nervous system (CNS) shortly after the initial infection. Although the brain is protected by a series of tissues known as the blood-brain barrier, some immune cells, such as macrophages, can get through. This makes some degree of sense. Usually, these cells are used to fight off infection. In HIV, though, the cells are actually carrying the infection. It's a bit like dressing up like a security guard in order to sneak into a fortress.

Once in the brain, the virus does not enter the nerve cells themselves but damages them indirectly by triggering an inflammatory response.

Risk Factors for HAD

Major risks factors for HAD include poor adherence to antiretroviral medications and a detectable viral load. The length of time that someone has been infected with HIV is less important than how low their CD4 count has gotten overall.

Evaluation for HAD

Because HIV makes people prone to other problems that can cause cognitive changes, such as infections and cancers, a thorough evaluation is called for when someone with HIV has a change in how they think. This is especially true if someone is getting worse quickly. Most dementias are slow, and a fast course could either mean that there is a different problem going on, or that the HIV is getting out of control.

Workup for HIV dementia should include an MRI of the brain to look for signs of infection or cancer. HIV-associated dementia itself causes significant changes in the picture of the brain taken by MRI. The brain can be shown to be shriveling, and there are increased amounts of white matter hyperintensities, which are bright spots where they don't belong.

Treatment of HAD

Like many other forms of dementia, it is not clear what, if any, treatments can help someone with HIV-Associated Dementia. One of the medications commonly used in Alzheimer's disease, Memantine, has been proven not to help, and there's really no reason to believe that other medications used for Alzheimer's would be useful.

Good adherence to antiretroviral therapy has been associated with lower risks of HAD, but it's less certain whether adding or changing medications in someone with HAD is of any benefit. In one study, changing antiretroviral medications actually made people worse. However, if someone has a very concerning HIV-Associated Dementia, many people will change medications, especially if the medications the patient is on are not well known for entering the central nervous system (CNS). Medications such as tenofovir, zalcitabine, nelfinavir, ritonavir, saquinavir and enfuviritide all have been shown to have good penetrance into the CNS, though the helpfulness of that penetrance does remain in question, and may actually cause more harm than good.

Some people use methylphenidate (Ritalin) to help with cognitive slowing. In general, staying mentally, socially and physically active is advised.

HIV dementia is a serious problem, and unfortunately, we still do not know much about it. Unlike many other forms of dementia, people with HIV dementia do sometimes improve, and so it is important to discuss these symptoms with a qualified physician.

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Article Sources
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