HIV-Associated Neurocognitive Disorders

• Direct viral invasion and CNS infection: HIV crosses the blood-brain barrier via infected monocytes (Trojan horse mechanism) or direct infection of endothelial cells. Macrophages and microglial cells serve as primary CNS reservoirs, producing high levels of viral RNA and proinflammatory cytokines. CD4+ T cells are relatively spared in the CNS compared to systemic infection, explaining why HAND can occur at higher CD4 counts than other opportunistic infections.

• Chronic neuroinflammation and excitotoxicity: Infected macrophages and microglia secrete excessive levels of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), creating a pro-inflammatory microenvironment. These cytokines cause activation of NMDA receptors on neurons, leading to excessive glutamate release and subsequent excitotoxic injury via calcium influx. Chronic immune activation persists despite viral suppression on cART, contributing to ongoing neurocognitive decline in some patients.

• White matter damage and neuronal loss: Productive infection of oligodendrocytes causes demyelination and white matter pallor, particularly in frontal lobes and basal ganglia. Loss of neuronal dendrites and synapses occurs through multiple mechanisms including direct viral gp120-mediated toxicity, viral protein Tat-mediated neurotoxicity, and indirect effects from activated glial cells. Neuroimaging demonstrates brain atrophy, ventricular enlargement, and white matter hyperintensities correlating with cognitive severity.

• Blood-brain barrier dysfunction: Infection of endothelial cells and astrocytes compromises tight junction integrity, allowing infiltration of peripheral immune cells and toxic substances. Release of matrix metalloproteinases (MMPs) by infected macrophages further disrupts the BBB, perpetuating CNS inflammation.

Direct causes

• HIV encephalitis (HIVE): Characterized by microglial nodules, myelin pallor, and neuronal loss on autopsy; seen in 50% of HAD cases
• HIV-associated white matter disease: Predominant finding in some cases with extensive demyelination

Major risk factors

• Immunosuppression severity: CD4+ count <200 cells/μL carries significantly higher risk; however, HAND can occur at any CD4 count
• Viral replication burden: Both CSF and plasma HIV RNA levels correlate with cognitive decline; unsuppressed virus on cART is major risk factor
• cART regimen and CNS penetration: Antiretrovirals with poor CNS penetration (high protein binding, low lipophilicity) associated with higher HAND rates; protease inhibitors show better CNS penetration than some NRTIs
• Duration of HIV infection: Longer disease duration without treatment increases risk
• Genetic factors: CCR5-Δ32 deletion, HLA alleles, and polymorphisms in inflammatory cytokines affect susceptibility
• Age: Older patients show accelerated cognitive decline
• Comorbidities: Hepatitis C coinfection, substance abuse (particularly methamphetamine), depression, and cardiovascular disease worsen outcomes
• Poor antiretroviral adherence: Critical determinant of viral suppression and cognitive preservation

• Slowed cognitive processing and difficulty concentrating (earliest and most sensitive finding)
• Memory impairment affecting both short-term and long-term memory; typically subcortical pattern (retrieval > encoding difficulty)
• Executive dysfunction: Impaired judgment, planning, problem-solving, and decision-making
• Word-finding difficulty and anomia (not fluent aphasia; comprehension preserved)
• Decreased mental flexibility and difficulty with complex tasks

Motor symptoms

• Slowed motor movements and bradykinesia (often precedes cognitive changes)
• Gait disturbance: Unsteady gait, difficulty with balance, wide-based gait
• Tremor and myoclonus: Fine tremor typical; myoclonus indicates more severe disease
• Weakness: Focal or generalized depending on severity
• Loss of fine motor coordination: Evident on rapid alternating movements and finger tapping

Behavioral and psychiatric symptoms

• Apathy and motivation loss (most common behavioral change, easily mistaken for depression)
• Irritability and mood lability
• Depression (occurs in >30% of HAND patients)
• Personality changes
• Psychosis: Rare but indicates severe disease

Physical examination findings

• Slowed saccadic eye movements and impaired smooth pursuit
• Hyperreflexia and spasticity in lower extremities
• Extensor plantar responses (Babinski sign positive)
• Impaired rapid alternating movements and dysmetria
• Gait abnormalities: Ataxia, shuffling gait, or spastic paraparesis pattern
• Frontal release signs: Snout reflex, grasp reflex in severe cases
• Neuropsychological testing abnormalities: Slower processing speed, reduced attention, executive dysfunction out of proportion to memory impairment

1. 1.Confirmed HIV infection
2. 2.Documented cognitive, motor, or behavioral impairment affecting daily function (distinguishes from asymptomatic impairment)
3. 3.Exclusion of other causes of cognitive dysfunction
4. 4.Evidence of cognitive/motor dysfunction on neuropsychological testing, examination, or validated screening tools

Diagnostic categories

• Asymptomatic Neurocognitive Impairment (ANI): Abnormality on neurocognitive testing only; no functional impact
• Mild Neurocognitive Disorder (MND): Mild functional decline with documented cognitive/motor abnormality
• HIV-Associated Dementia (HAD): Substantial functional impairment (inability to work, self-care deficits) with cognitive/motor dysfunction

Screening and cognitive assessment

• Montreal Cognitive Assessment (MoCA) or Mini-Cog: Quick screening tools
• Trail Making Test A and B: Sensitive for processing speed and executive function; HAND-sensitive
• Hopkins Verbal Learning Test: Assesses memory and learning
• Formal neuropsychological battery: Gold standard; includes tests of processing speed, attention, memory, executive function, and motor function; requires 4-6 hours
• Frascati criteria: Standardized research criteria requiring 1.0 SD below normative mean in two cognitive domains or 2.0 SD in one domain

Laboratory evaluation

• CD4+ count and plasma HIV RNA: Essential for prognosis; CD4 <200 associated with increased risk
• CSF HIV RNA: Elevated CSF viral load (often higher than plasma) correlates with cognitive dysfunction; CSF/plasma ratio >1 suggests CNS viral replication
• CSF markers: Elevated neurofilament light chain (NFL), phosphorylated tau (p-tau), and total tau associated with neuronal damage; research tools
• Standard CSF analysis: Normal in HAND (unlike other CNS conditions); rule out meningitis, encephalitis, or other infections

Neuroimaging

• MRI brain (preferred modality):
• White matter abnormalities: T2/FLAIR hyperintensities, particularly periventricular and frontal regions
• Brain atrophy: Ventricular enlargement and sulcal widening; correlates with HAD severity
• Basal ganglia abnormalities: T2 hyperintensities, particularly in putamen
• Demyelination patterns: Diffuse white matter disease in advanced cases
• Normal scan does not exclude HAND (up to 20% of HAD patients have normal MRI)

• MR Spectroscopy (research tool):
• Elevated myoinositol and choline (glial markers)
• Reduced N-acetylaspartate (NAA) (neuronal marker)
• NAA/creatinine ratio correlates with cognitive dysfunction

• PET imaging: Hypometabolism in frontal lobes, basal ganglia, and white matter; research only

• CNS infections: Toxoplasma encephalitis, cryptococcal meningitis, CMV ventriculoencephalitis, PML, tuberculosis (obtained via CSF analysis, imaging, cultures)
• Primary CNS lymphoma: Distinguished by contrast-enhancing lesions and CSF cytology
• Stroke or cerebrovascular disease: Imaging findings, acute presentation
• Metabolic encephalopathy: Liver disease, renal failure, electrolyte abnormalities (labs)
• Substance use disorders: Stimulant use particularly can mimic or worsen cognitive dysfunction; urinalysis, history
• Psychiatric disorders: Primary depression, bipolar disorder
• Age-related cognitive decline: Establish baseline, longitudinal decline
• Medication effects: Some antiretrovirals (particularly early PIs), anticholinergics, benzodiazepines

First-line therapy: Optimization of antiretroviral therapy

• Mechanism: Maximal suppression of HIV replication in plasma and CSF prevents ongoing viral damage and neuroinflammation
• Selection criteria: Regimens with good CNS penetration including integrase strand transfer inhibitors (INSTIs) such as dolutegravir or bictegravir (superior CNS penetration), combined with two nucleoside reverse transcriptase inhibitors (NRTIs) or boosted protease inhibitors (PIs)
• CNS Penetration Score: Three-drug regimens targeting score ≥8-10 shown superior outcomes; examples include dolutegravir/TAF/FTC, bictegravir/TAF/FTC
• Duration: Cognitive improvement often requires 4-12 weeks of viral suppression; some improvement can occur months to years later
• Adherence monitoring: Critical for success; baseline counseling, pill counts, pharmacy refill tracking
• Expected response: 30-50% improvement in cognitive symptoms with adequate viral suppression; some patients show partial or no improvement suggesting fixed neuronal damage

Alternative regimens

• Efavirenz-based regimens: Historical first-line for HAND due to CNS penetration, but neuropsychiatric side effects limit use; reserve for specific indications
• Two-drug regimens: Dolutegravir + lamivudine or dolutegravir + TAF/FTC if tolerating well with sustained viral suppression (less data in HAND specifically)

• Memantine: NMDA receptor antagonist to reduce excitotoxicity; mixed data, may benefit subset of HAD patients; dose 10-20 mg daily
• Minocycline: Inhibits microglial activation; small studies show modest cognitive benefit; dose 100 mg twice daily; limited by tolerance with long-term use
• Psychostimulants: Methylphenidate or modafinil for apathy and fatigue; symptomatic benefit without addressing underlying pathology; dose methylphenidate 5-20 mg twice daily or modafinil 100-200 mg daily
• Selective serotonin reuptake inhibitors (SSRIs): For comorbid depression (present in >30%); sertraline or escitalopram first-line
• Low-dose naltrexone: Emerging evidence for neuroinflammation reduction; 4.5 mg nightly; requires further validation

Non-pharmacological interventions

• Cognitive rehabilitation: Structured programs targeting specific deficits; limited evidence but may help functional adaptation
• Neuropsychological counseling: Education about disease, compensatory strategies, realistic expectations
• Exercise programs: Aerobic and resistance training; evidence supports cognitive and mood benefits
• Social engagement and mental stimulation: Activities promoting cognitive reserve
• Occupational/physical therapy: Gait training for motor impairment, fall prevention, adaptive equipment
• Caregiver support: Education and resources for family members involved in care
• Substance abuse treatment: Cessation of stimulants particularly critical; referral to addiction medicine

Monitoring and follow-up

• Baseline neuropsychological assessment: Establishes baseline for future comparison (especially important given mild forms can progress)
• Repeat assessments: Every 6-12 months clinically; formal testing yearly or with symptom change
• Viral load monitoring: Monthly initially, then every 3-6 months; goal is undetectable (<50 copies/mL)
• CD4 recovery: Immune reconstitution occurs over months; may worsen neuroinflammation transiently (immune reconstitution inflammatory syndrome [IRIS])
• Adherence assessment: Regular counseling and verification of cART adherence

Neuropsychiatric complications

• Major depression: Occurs in 30-50% of HAND patients; complicates rehabilitation efforts; treat with SSRIs while optimizing ART
• Suicidality: Increased risk with depression and cognitive decline; assess at each visit; requires acute psychiatric intervention when present
• Psychosis and delirium: In advanced HAD; rule out secondary causes (infection, metabolic derangement); may require antipsychotics

Functional decline complications

• Loss of employment and economic hardship: Cognitive and motor impairment prevents work; counseling and disability benefits assessment
• Loss of independence in activities of daily living (ADLs): Inability to manage finances, medication, self-care; requires caregiver support and possible placement in assisted living
• Falls and injuries: Gait disturbance and cognitive decline increase fall risk; implement fall prevention strategies, assistive devices
• Motor complications: Spasticity, contractures, pressure ulcers with advanced disease; require physical therapy and nursing care

Life-threatening complications

• Opportunistic infections with cognitive decline: Acute decompensation may unmask concurrent CNS infections (toxoplasma, cryptococcal meningitis, CMV); requires emergent evaluation with brain imaging and LP
• Aspiration pneumonia: Dysphagia and cognitive decline → aspiration risk; swallow evaluation, dietary modification
• Seizures: Occur in 2-5% of HAND patients, indicating severe disease; require EEG, neuroimaging, and antiepileptic drugs (levetiracetam or lamotrigine preferred due to drug interactions)
• Status epilepticus: Medical emergency; ICU care required
• Severe metabolic disturbance: Hepatic encephalopathy, uremia worsening cognition

Treatment-related complications

• IRIS (immune reconstitution inflammatory syndrome): Occurs with CD4 recovery on cART; worsening cognition, imaging changes; may temporarily worsen HAND; managed by continuing cART and treating underlying inflammation
• Medication side effects: Efavirenz neuropsychiatric effects, PI GI intolerance affecting adherence, mitochondrial toxicity with older NRTIs

Modern era with cART

• Dramatic improvement: Incidence of HAD declined 50-80% with universal cART implementation
• Reversibility: Early cognitive decline may be partially or completely reversible with viral suppression (particularly MND and early HAD)
• Partial improvement: Even advanced HAD shows 30-50% cognitive improvement with cART optimization, though fixed neuronal damage may limit full recovery
• ANI and MND outcomes: Generally stable or slowly progressive

• **HAND is a subcortical dementia**: psychomotor slowing, apathy, and impaired retrieval with relatively preserved language and comprehension. The examiner's contrast is cortical Alzheimer disease (aphasia, apraxia, agnosia, encoding failure that does not improve with cueing). Prominent early bradykinesia and gait slowing in a young patient with dementia is the buzzword pair.
• Single best next step in any HIV patient with new cognitive or focal deficits: contrast-enhanced MRI brain before lumbar puncture to exclude mass lesions and herniation risk. HAND is a diagnosis of exclusion — never the first answer when focal signs, fever, or new seizures are present.
• Definitive therapy is virologic suppression, not a neuroprotectant: per the DHHS/NIH Antiretroviral Guidelines, start or optimize combination ART (INSTI-based, e.g., dolutegravir or bictegravir, with two NRTIs). Memantine, minocycline, and stimulants are adjuncts only — a distractor stem offering "start donepezil" or "start memantine as primary therapy" is wrong.

The lesion the question is really testing

• Toxoplasma encephalitis: multiple ring-enhancing lesions with mass effect, basal ganglia/gray–white junction, positive Toxoplasma IgG. Treat empirically (pyrimethamine + sulfadiazine + leucovorin) and re-image; failure to respond pushes toward biopsy.
• Primary CNS lymphoma: usually a solitary periventricular enhancing lesion, EBV DNA in CSF — the classic toxoplasmosis mimic.
• PML (JC virus): asymmetric, non-enhancing subcortical white matter lesions without mass effect; JC virus PCR in CSF; treatment is ART, and paradoxical worsening suggests IRIS.
• Cryptococcal meningitis: subacute headache and fever with scant meningeal signs; CSF cryptococcal antigen (most sensitive), India ink on classic stems. Per IDSA guidance, induction is liposomal amphotericin B plus flucytosine, and elevated opening pressure is managed with therapeutic serial lumbar punctures — not steroids or shunt as the first move.
• Association tested most: HAND can occur at any CD4 count and even with suppressed plasma virus, unlike the CD4-threshold opportunistic infections — a favorite trap.