Q&A: Causes of Confusion in HIV-infected Patients

Changes in memory, concentration, attention, and motor skills are common in HIV-infected patients and present a diagnostic challenge to the clinician. Since these symptoms can be caused by a variety of disorders, accurate diagnosis is critical for patient treatment. When not clearly attributable to an alternate cause other than HIV infection, such impairments have been collectively classified as HIV-associated neurocognitive disorders (HAND).

This article is for Medical Students & Professionals

This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the HIV Disease article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.

In this article:
HIV-associated neurocognitive disorders (HAND)
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

HIV-associated neurocognitive disorders (HAND)

The presence of neurocognitive deficits in certain HIV-infected individuals without alternative explanation other than HIV infection has long been recognized. The umbrella term, HIV-associated neurocognitive disorders (HAND) includes three levels of impaired neuropsychological test performance and functional impairment:

• Asymptomatic neurocognitive impairment (ANI) – defined by a score of one standard deviation or more below the mean in at least two cognitive domains on standardized neuropsychological testing without a symptomatic or observable functional impairment.
• Mild neurocognitive disorder (MND) – defined by a score of one standard deviation or more below the mean in at least two cognitive domains on standardized neuropsychological testing with at least mild symptomatic or functional impairment.
• HIV-associated dementia (HAD) – defined by a score of two standard deviations or more below the mean in at least two cognitive domains on standardized neuropsychological testing with concomitant impairment in activities of daily living.

The definitions are applied only when the observed impairment cannot be explained by other conditions, either alternative neurological diagnoses (such as opportunistic infection, stroke, or metabolic or toxic encephalopathy) or underlying "confounding" comorbidities that might alter neuropsychological test performance (such as severe substance abuse, prior head trauma, or severe psychiatric disease).

MCQ exam: clinical scenario

A 34 year old HIV positive patient develops a new-onset of confusion. A CT scan of the brain reveals multiple enhancing lesions.

The most likely diagnosis is:

a) HIV encephalitis
b) Cryptococcus
c) PML
d) Lymphoma
e) Toxoplasmosis

MCQ exam: answer

The correct answer is E.

MCQ exam: explanation

The main differential diagnosis of focal brain lesions in HIV-infected patients is between CNS lymphoma and toxoplasmic encephalitis.

In T gondii-seropositive, HIV-infected patients with CD4 T-cell counts <100/µL, who are not receiving anti-T gondii prophylaxis, the presence of multiple enhancing lesions is strongly suggestive of toxoplasmic encephalitis. In patients on prophylaxis, or those with a single brain lesion, the differential diagnosis includes CNS lymphoma, fungal abscess, mycobacterial or cytomegaloviral disease, or Kaposi sarcoma in addition to toxoplasmic encephalitis.

The absence of anti-T gondii IgG in serum strongly argues against the diagnosis of toxoplasmic encephalitis.

Reference(s)
1). UpToDate: HIV-associated neurocognitive disorders: Epidemiology, clinical manifestations, and diagnosis. Available online: https://www.uptodate.com/contents/hiv-associated-neurocognitive-disorders-epidemiology-clinical-manifestations-and-diagnosis