A 28-year-old woman from Delhi, known to be HIV-positive for 2 years, presents with a 2-month history of progressive cognitive decline, memory loss, and gait disturbance. Her CD4 count is 45 cells/μL. Neurological examination reveals mild dementia, ataxia, and hyperreflexia. MRI brain shows diffuse white-matter abnormalities without focal lesions. CSF analysis is unremarkable. She is not on ART. What is the most likely diagnosis?

Explanation

## HIV-Associated Neurocognitive Disorder (HAND) **Key Point:** HAND (formerly called HIV-associated dementia, HAD) is a direct CNS manifestation of HIV that occurs at any CD4 count but is most severe at CD4 <50 cells/μL. It presents with cognitive decline, motor slowing, and behavioral changes. ### Diagnostic Criteria for HAND | Feature | HAND | Cryptococcal Meningitis | Toxoplasma Encephalitis | PML | |---------|------|------------------------|------------------------|-----| | CD4 threshold | Any (worse <50) | <100 | <100 | <50 | | Onset | Insidious (weeks–months) | Subacute (2–4 weeks) | Acute (days–weeks) | Subacute (weeks) | | Cognitive pattern | Slowed processing, memory loss | Meningeal signs + confusion | Focal deficits, seizures | Focal white-matter lesions | | CSF findings | Normal or mild protein ↑ | Positive India ink, low glucose | Toxo serology, focal lesions on imaging | JC virus PCR | | Imaging | Diffuse white-matter atrophy | Normal or mild hydrocephalus | Ring-enhancing lesions (multiple) | Demyelinating lesions, no enhancement | | Response to treatment | ART (immune reconstitution) | Fluconazole | TMP-SMX + pyrimethamine | Cidofovir, immune reconstitution | **High-Yield:** **Unremarkable CSF** rules out infectious causes (cryptococcus, toxoplasma, TB, syphilis) and strongly favors HAND as a primary HIV effect on the CNS. ### Pathophysiology of HAND 1. HIV infects macrophages and microglia in the CNS 2. Viral replication and inflammatory cytokine release (TNF-α, IL-6) cause neuronal injury 3. Diffuse white-matter damage without focal lesions 4. Progressive cognitive slowing, memory impairment, and motor dysfunction 5. Immune reconstitution with ART halts and may reverse progression **Clinical Pearl:** HAND is a **diagnosis of exclusion** — all other opportunistic infections must be ruled out (especially cryptococcal meningitis and toxoplasma encephalitis) before attributing cognitive decline to HIV itself. ### Clinical Presentation Spectrum - **Asymptomatic neurocognitive impairment (ANI):** Cognitive deficits on testing, no functional impact - **Mild neurocognitive disorder (MND):** Mild cognitive/motor symptoms, mild functional impact - **HIV-associated dementia (HAD):** Marked cognitive decline, significant functional impairment, motor slowing ### Diagnostic Approach 1. **Neuropsychological testing:** Formal cognitive assessment (Mini-Cog, Montreal Cognitive Assessment) to document impairment 2. **MRI brain:** Diffuse white-matter abnormalities, cerebral atrophy, no focal lesions 3. **CSF analysis:** Normal cell count, normal glucose, mildly elevated protein; negative for cryptococcus, toxoplasma, TB, syphilis, JC virus 4. **Exclude other causes:** Blood cultures, serology (syphilis, toxoplasma), neuroimaging (focal lesions) ### Management **First-line:** Initiate ART immediately — immune reconstitution is the cornerstone of treatment - Most patients show cognitive improvement within weeks to months of achieving undetectable viral load - CD4 recovery to >200 cells/μL associated with stabilization and partial reversal of cognitive deficits **Adjunctive:** - Psychostimulants (methylphenidate) for apathy and cognitive slowing - Antiretrovirals with good CNS penetration (efavirenz, integrase inhibitors) may provide additional benefit - Symptomatic management of depression, behavioral disturbances **Key Point:** HAND is **preventable and largely reversible** with early ART initiation; prognosis has dramatically improved in the era of combination ART.