HIV-Associated Neurocognitive Disorder
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Direct answer
HIV-associated neurocognitive disorder is a spectrum of cognitive impairment caused by HIV infection of the brain, ranging from asymptomatic impairment to HIV-associated dementia. It is a diagnosis of exclusion, made only after opportunistic infections, lymphoma, syphilis and drug toxicity have been ruled out. Effective antiretroviral therapy reduces the severity of the most serious forms, although milder impairment persists in many patients.
What you must remember
- Asymptomatic impairment: Abnormal neuropsychological testing without functional decline in daily activities.
- Mild neurocognitive disorder: Subjective and objective decline with a mild effect on daily life or work.
- HIV-associated dementia: Marked cognitive, motor and behavioural decline that interferes with daily function, now uncommon where treatment is available.
- Subcortical pattern: Slowed processing, apathy, poor recall and motor slowing, rather than early aphasia or agnosia.
- Mimics first: Cryptococcal meningitis, toxoplasmosis, progressive multifocal leukoencephalopathy, CNS tuberculosis, CNS lymphoma, syphilis and drug toxicity must be excluded.
- Investigations: CSF examination and neuroimaging help exclude mimics and document the pattern of brain involvement.
- Antiretroviral therapy: Effective ART reduces progression, and CNS-penetrating regimens are sometimes tried when cognition is affected, although evidence for their benefit is mixed.
Spectrum and approach to cognitive decline in HIV
Cognitive decline in HIV is graded by how much it affects everyday function. The table sets out the three recognised categories and the features that separate them. Mild impairment is often missed on routine examination, so formal neuropsychological testing is the usual route to the diagnosis.
| Category | Everyday function | Typical features |
|---|---|---|
| Asymptomatic impairment | Preserved | Abnormal testing only |
| Mild neurocognitive disorder | Mildly affected | Slowed thinking, forgetfulness, mild motor slowing |
| HIV-associated dementia | Clearly impaired | Apathy, psychomotor slowing, poor recall, gait disturbance and tremor |
The categories form a continuum rather than fixed stages, and patients can move between them as the disease and its treatment change. Patients with milder forms often remain independent, but they still need careful reassessment of ART adherence and of coexisting causes.
Any new decline in a person with HIV should trigger a search for a treatable mimic before the diagnosis is accepted. Clinicians also repeat the testing after treatment changes, since the same score can shift with mood, sleep and education level.
Where the exam tries to catch you
Examiners test whether you exclude the treatable causes before attributing dementia to HIV.
- Trap: Diagnosing HIV-associated dementia without first excluding cryptococcal meningitis or toxoplasmosis Correct: dementia is a diagnosis of exclusion, and both infections are treatable causes that must be ruled out first.
- Trap: Assuming ART has no effect on neurological disease Correct: ART reduces the incidence and severity of HIV-associated dementia, but milder impairment can persist despite suppressed plasma viral load.
- Trap: Attributing early cognitive slowing to Alzheimer disease Correct: HIV-associated disease has a subcortical pattern with slowed processing and apathy, whereas Alzheimer disease shows early amnesia and cortical signs.
Frequently asked questions
What is the key difference between HIV-associated dementia and Alzheimer disease?
HIV-associated dementia is a subcortical dementia with slowed processing, apathy and motor slowing. Alzheimer disease usually presents with early amnesia and cortical features such as aphasia or agnosia. Neuroimaging and CSF testing help separate the two when the presentation overlaps.
Why is HIV-associated neurocognitive disorder a diagnosis of exclusion?
HIV-associated neurocognitive disorder is a diagnosis of exclusion because opportunistic infections, lymphoma, syphilis and drug toxicities can produce the same cognitive symptoms. Careful CSF examination, neuroimaging and serological testing are needed to exclude these mimics. Only after they are excluded can the decline be attributed to HIV itself.
Does antiretroviral therapy prevent HIV-associated neurocognitive disorder?
Antiretroviral therapy has greatly reduced the incidence and severity of HIV-associated dementia, especially when started early. It does not fully prevent milder cognitive impairment, which can persist despite suppressed plasma viral load. Evidence on switching to CNS-penetrating regimens is mixed, so the choice is individualised.
Which opportunistic infections must be excluded in suspected HIV dementia?
Cryptococcal meningitis, toxoplasmosis, progressive multifocal leukoencephalopathy, CNS tuberculosis, CNS lymphoma and syphilis must be excluded in suspected HIV-associated dementia. Cryptococcal antigen testing and MRI for lesions are the usual first steps. Each treatable mimic can cause dementia that improves with specific therapy.