Lecture #100: CNS: Fungal Parasite Infections

What defines chronic meningitis?

Meningeal inflammation lasting longer than 4 weeks with CSF pleocytosis and gradually evolving symptoms such as headache, fever, neurologic deficits, and increased intracranial pressure.

What are common categories of CNS infections caused by fungi and parasites?

Meningitis, encephalitis, myelitis, and brain abscesses affecting different regions of the CNS.

What is a key feature of fungal chronic meningitis?

It is typically opportunistic, occurring in immunocompromised patients with lymphocytic pleocytosis.

What are common fungal causes of chronic meningitis?

Aspergillus, Candida, Coccidioides, Cryptococcus, Histoplasma, Pseudallescheria, and Sporothrix species.

What is the most important fungal cause of chronic meningitis?

Cryptococcus neoformans, which causes subacute meningoencephalitis and hydrocephalus.

How is Cryptococcus neoformans diagnosed?

By cryptococcal antigen testing and visualization with India ink showing encapsulated yeast.

How is Cryptococcus neoformans treated?

With amphotericin B combined with flucytosine.

What are key features of Coccidioides infection?

It presents with erythema nodosum, hydrocephalus, and CSF eosinophilia in endemic regions.

How is Coccidioides diagnosed?

By complement fixing antibodies, CSF eosinophilia, and culture.

How is Coccidioides treated?

With amphotericin B and azole antifungals.

What are key features of Histoplasma capsulatum CNS infection?

It occurs in endemic regions such as the Ohio River Valley and presents with fever, hepatosplenomegaly, and hydrocephalus.

How is Histoplasma diagnosed?

By antigen detection in urine, blood, or CSF and visualization inside macrophages.

How is Histoplasma treated?

With amphotericin B.

What is unique about Pseudallescheria infection?

It is associated with polluted water exposure, near drowning, and is resistant to amphotericin B.

What is the most common parasitic cause of CNS infection?

Taenia solium causing neurocysticercosis.

What are key features of neurocysticercosis?

Seizures, hydrocephalus, and space occupying brain lesions.

How is neurocysticercosis diagnosed?

By CT showing calcified lesions and CSF eosinophils.

How is neurocysticercosis treated?

With albendazole, steroids, antiepileptics, and sometimes surgical intervention.

What parasite causes eosinophilic meningitis after eating contaminated seafood?

Angiostrongylus cantonensis, also known as rat lung worm.

How is Angiostrongylus infection diagnosed?

By history of exposure and CSF or peripheral eosinophilia.

How is Angiostrongylus infection treated?

It typically resolves spontaneously without specific treatment.

What is the most deadly parasitic CNS infection?

Naegleria fowleri causing primary amebic meningoencephalitis.

How does Naegleria fowleri enter the body?

Through the nose during freshwater exposure.

What are key symptoms of Naegleria infection?

Altered mental status, loss of smell, and rapid progression to death.

What is the prognosis of Naegleria infection?

Nearly 100 percent mortality even with treatment.

What laboratory findings are seen in Naegleria infection?

Neutrophilic pleocytosis and motile trophozoites in warm CSF.

What treatment may be used for Naegleria infection?

Miltefosine shows some promise despite high mortality.

What parasite causes granulomatous amebic encephalitis?

Balamuthia mandrillaris.

How does Balamuthia infection occur?

Through skin wounds or inhalation of contaminated soil.

What are key features of Balamuthia infection?

Slow progressive disease with cranial nerve deficits, hydrocephalus, and high mortality.

What laboratory findings are seen in Balamuthia infection?

Lymphocytic pleocytosis, low glucose, and confirmation by histopathology or PCR.

What is the treatment for Balamuthia infection?

Combination therapy with sulfadiazine, macrolides, rifampin, and fluconazole.

What parasite is associated with raccoon exposure and eosinophilic encephalitis?

Baylisascaris procyonis.

How is Baylisascaris infection acquired?

By ingestion of contaminated soil or dust containing eggs.

What are key lab findings in Baylisascaris infection?

Eosinophilic pleocytosis, peripheral eosinophilia, and MRI abnormalities.

How is Baylisascaris treated?

With albendazole.

What parasite is acquired from raw freshwater fish and migrates to the brain?

Gnathostoma species.

How is Gnathostoma diagnosed?

By identifying larvae in tissue or ELISA testing.

What is the treatment for CNS Gnathostoma infection?

There is no effective treatment once CNS infection occurs.

What causes parasitic brain abscesses?

Organisms such as Taenia solium, Entamoeba histolytica, Schistosoma japonicum, and Paragonimus species.

What are common symptoms of brain abscesses?

Headache, altered mental status, focal deficits, fever, seizures, nausea, and vomiting.

What is a key diagnostic feature of brain abscesses?

Space occupying lesions seen on imaging such as CT or MRI.

How does Entamoeba histolytica affect the CNS?

It forms brain abscesses following systemic infection.

How is Entamoeba histolytica treated?

With metronidazole or tinidazole followed by luminal agents such as paromomycin.

What is Schistosoma japonicum?

A blood fluke causing granulomatous brain lesions after freshwater exposure.

How is Schistosoma japonicum diagnosed?

By identifying eggs, serology, and evidence of granulomas.

How is Schistosoma japonicum treated?

With praziquantel.

What parasite is associated with eating raw crab or crayfish?

Paragonimus species.

What are key features of Paragonimus infection?

Symptoms similar to tuberculosis with eosinophilia and lung involvement.

How is Paragonimus treated?

With praziquantel.

What is a major diagnostic challenge in encephalitis?

The causative pathogen is identified in less than 50 percent of cases.

What is a key epidemiologic clue in CNS infections?

Travel history, diet, environmental exposure, and immune status help determine the cause.

What is the role of CSF analysis in CNS infections?

It is critical for identifying the type of infection and guiding antimicrobial therapy.