Match each clinical and neuroimaging presentation of a central nervous system disorder in … — USMLE Step 2 CK

Match each clinical and neuroimaging presentation of a central nervous system disorder in patients with advanced HIV infection to its most appropriate definitive or empiric management.

A $35$ -year-old male with a CD4 count of $80$ cells/mm $^3$ presents with a two-week history of severe headache, nausea, and neck stiffness. Cerebrospinal fluid analysis reveals a significantly elevated opening pressure and a positive latex agglutination test for a polysaccharide capsular antigen.Intravenous amphotericin B and oral flucytosine
A $42$ -year-old female with a CD4 count of $45$ cells/mm $^3$ develops progressive hemiparesis, cognitive impairment, and expressive aphasia over the past month. Brain magnetic resonance imaging reveals multiple asymmetric, non-enhancing white matter demyelinating lesions without mass effect or surrounding edema.Initiation or optimization of antiretroviral therapy
A $39$ -year-old male with a CD4 count of $90$ cells/mm $^3$ is brought to the emergency department after a new-onset generalized tonic-clonic seizure. Brain magnetic resonance imaging with contrast demonstrates multiple small, ring-enhancing lesions predominantly located in the basal ganglia.Oral sulfadiazine, oral pyrimethamine, and oral leucovorin
A $45$ -year-old male with a CD4 count of $25$ cells/mm $^3$ presents with rapidly progressive confusion, apathy, and cranial nerve palsies. Brain magnetic resonance imaging shows distinct periventricular enhancement suggestive of ventriculitis.Intravenous ganciclovir or intravenous foscarnet

Answer

The presentations map to the following treatments: Cryptococcal meningitis requires amphotericin B and flucytosine; Progressive multifocal leukoencephalopathy (PML) requires optimization of antiretroviral therapy; Toxoplasmosis requires sulfadiazine, pyrimethamine, and leucovorin; Cytomegalovirus encephalitis requires ganciclovir or foscarnet.

Each central nervous system infection in advanced HIV has a distinct clinical and radiographic profile that dictates its specific management. Cryptococcal meningitis is characterized by elevated intracranial pressure and is treated with amphotericin B and flucytosine. Toxoplasmosis presents with multiple ring-enhancing lesions and responds to sulfadiazine and pyrimethamine. JC virus causes progressive multifocal leukoencephalopathy (non-enhancing white matter lesions) and is managed solely by reversing immunosuppression with antiretroviral therapy. Cytomegalovirus causes ventriculitis and must be treated with targeted agents like ganciclovir or foscarnet.

Step-by-Step Solution

Analyze the first clinical vignette involving elevated opening pressure and a positive polysaccharide antigen test.

Identify the pathogen as Cryptococcus neoformans.

The polysaccharide capsule is characteristic of Cryptococcus, which typically presents with subacute meningitis and elevated intracranial pressure in patients with CD4 counts below

100

cells/mm

^3

Evaluate the second vignette detailing non-enhancing white matter lesions without edema.

Identify the condition as progressive multifocal leukoencephalopathy (PML) caused by the JC virus.

PML causes asymmetric demyelination without mass effect in severely immunocompromised hosts, distinguishing it from space-occupying lesions.

Examine the third vignette describing seizures and multiple ring-enhancing lesions in the basal ganglia.

Identify the etiology as Toxoplasma gondii.

Toxoplasmosis is the most common cause of ring-enhancing brain lesions in patients with advanced HIV and frequently presents with seizures and focal neurologic deficits.

Assess the fourth vignette featuring rapid neurologic decline and periventricular enhancement.

Identify the pathogen as Cytomegalovirus (CMV).

CMV encephalitis typically presents with ventriculitis and cranial nerve neuropathies in patients with CD4 counts typically less than

50

cells/mm

^3

Match each identified infectious etiology to its guideline-directed management.

Cryptococcus pairs with amphotericin B and flucytosine. PML pairs with antiretroviral therapy. Toxoplasmosis pairs with sulfadiazine and pyrimethamine. CMV pairs with ganciclovir or foscarnet.

Survival and recovery depend on utilizing the pathogen-specific antimicrobial or immune reconstitution strategy indicated for each distinct central nervous system infection.

Key Concept

Identifying opportunistic central nervous system infections in advanced HIV based on CD4 count, clinical presentation, and neuroimaging to determine the targeted pharmacotherapy.

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