Hiv-associated dementia

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HIV-associated dementia is chronic cognitive deterioration due to brain infection by HIV.
(See also Overview of Delirium and Dementia and Dementia.)
Dementia is chronic, global, usually irreversible deterioration of cognition. HIV-associated dementia (AIDS dementia complex) may occur in the late stages of HIV infection. Unlike almost all other forms of dementia, it tends to occur in younger people.
Dementia should not be confused with delirium, although cognition is disordered in both. The following helps distinguish them:

Dementia affects mainly memory, is typically caused by anatomic changes in the brain, has slower onset, and is generally irreversible.
Delirium affects mainly attention, is typically caused by acute illness or drug toxicity (sometimes life threatening), and is often reversible.

Other specific characteristics also help distinguish the 2 disorders (see table Differences Between Delirium and Dementia).
Purely HIV-associated dementia is caused by neuronal damage by the HIV virus. However, in patients with HIV infection, dementia may result from other disorders, some of which may be treatable. These disorders include other infections, such as secondary infection with JC virus causing progressive multifocal leukoencephalopathy and central nervous system (CNS) lymphoma. Other opportunistic infections (eg, cryptococcal meningitis, other fungal meningitis, some bacterial infections, tuberculosis meningitis, viral infections, toxoplasmosis) may also contribute.
In purely HIV-associated dementia, subcortical pathologic changes result when infected macrophages or microglial cells infiltrate into the deep gray matter (ie, basal ganglia, thalamus) and white matter.
Prevalence of dementia in late-stage HIV infection ranges from 7 to 27%, but 30 to 40% may have milder forms. Incidence is inversely proportional to CD4 count.