AIDS Dementia Complex

Neurocognitive Impairment Seen in Up to 30% of People Living with HIV

PET scan of a healthy brain (left) compared to that of a person with AIDS dementia complex before antiretroviral therapy (center) and after (right). Credit: National Cancer Institute

AIDS dementia complex (ADC), also known as HIV encephalopathy, is a neurological disorder directly caused by HIV. It is a condition classified by the Centers for Disease Control and Prevention (CDC) as an AIDS-defining condition and is characterized by the deterioration of cognitive, motor and behavioral function, the symptoms of which can include:

  • Memory and concentration problems
  • Diminished emotional and/or intellectual response
  • Marked behavioral changes
  • Diminished strength/frailty
  • Loss of fine motor skills (e.g. tremors, clumsiness)
  • Progressive loss of mobility
  • Dementia

Dementia is defined as having a persistent disruption of mental processes marked by personality changes, memory disorders, and impaired reasoning.

Causes of AIDS Dementia

ADC usually occurs in advanced disease when the patient's CD4 count is below 200 cells/μl and is generally accompanied by a high viral load.

Unlike most AIDS-defining conditions, ADC is not an opportunistic infection insofar as the condition is caused by HIV itself. Research indicates that HIV-infected white blood cells called macrophages and nerve cells called microglia secrete neurotoxins that adversely affect developing and mature nervous tissue. Over time, this can result in the degeneration of synaptic function (i.e. the transmission of information between neurons), as well as indirectly inducing cell death in neurons.

Diagnosing and Treating AIDS Dementia

There is no single test that can confirm the diagnosis of HIV encephalopathy. Diagnosis is made largely by exclusion, ruling out other possible causes of the impairment. A full assessment must be made by an experienced clinician, examining the patient's history, lab tests (e.g. lumbar puncture), brain scans (MRI, CT scan), and a review of the so-called "stage characteristics."

Stage characteristics determine the severity of impairment on a scale of 0 to 4, as follows:

  • Stage 0: Normal motor and mental function.
  • Stage 0.5: Minimal dysfunction with normal gait and strength. Person is able to work and perform regular day-to-day routines.
  • Stage 1: Functional impairment of motor and/or mental skills. Person can still walk without assistance and carry on all but the most demanding daily tasks.
  • Stage 2: Cannot work and has problems coping with more difficult aspects of daily life. However, the person is still able to care for himself/herself and is able to walk (albeit occasionally with the assistance of a single prop).
  • Stage 3: Major mental and/or motor incapacity. Person is unable to care for himself/herself.
  • Stage 4: Near vegetative state.

While the more severe manifestations of ADC have decreased greatly in numbers since the advent of combination antiretroviral therapy (cART), mild neurocognitive impairment is still seen in about 30% of those with asymptomatic HIV and 50% of those with AIDS.

Generally, the risk for ADC is seen to be higher in individuals who have not achieved viral suppression, although it can persist in 3% to 10% of those with fully controlled virus. It is suggested that early cART intervention may delay or reduce the risk of ADC.

For those with attributable neurocognitive impairment, cART would ideally include two drugs with appreciable penetration of the brain-blood barrier. Options include the nucleoside reverse transcriptase inhibitor-class drugs Retrovir (AZT) and Ziagen (abacavir), as well as the protease inhibitor-class drug Crixivan (indinavir).

Also Known As:

  • HIV encephalopathy
  • HIV-associated neurocognitive disorder (HAND)
  • HIV-associated dementia (HAD)


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Robertson, K.; Smurzynski, M.; Parsons, T.; et al. "The prevalence and incidence of neurocognitive impairment in the HAART era." AIDS. September 12, 2007; 21(14): 1915-1921.

Tozzi, V.; Balestra, P.; Bellagamba, R.; et al. "Persistence of Neuropsychologic Deficits Despite Long-Term Highly Active Antiretroviral Therapy in Patients With HIV-Related Neurocognitive Impairment: Prevalence and Risk Factors." Journal of Acquired Immune Deficiency Syndromes. June 1, 2007; 45(2):174-182.

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