Eosinophilic meningitis is characterized by elevated eosinophils in the cerebrospinal fluid (CSF) (the presence of more than 10 eosinophils per microliter in the CSF, or CSF eosinophilia of at least 10%), frequently associated with certain infectious agents.
A travel and exposure history including a careful history of foods recently ingested is important. Ingestion of raw or undercooked snails, slugs, prawns, crabs, lizards, or leafy vegetables and other foods contaminated by expelled larvae may cause disease. Specific behaviors such as pica can expose patients to other etiologies as well.
Symptoms typically begin within 24 hours to several days following consumption but can have delayed onset of several weeks. Common signs and symptoms include sudden-onset intense, painful headache, nuchal rigidity, and abdominal pain. Other signs and symptoms may include nausea, vomiting, pruritic rash, and fever. Neurologic findings may be absent or may include hyperesthesias, paresthesias, facial nerve palsy, paralysis, pain, weakness, coma, and death. Additional findings specific to the parasite may include ocular signs, blurred vision, blindness, and nerve damage.
Rarely, meningitis may persist for 4 weeks and is then considered chronic meningitis.
Several infections are associated with eosinophilic meningitis:
- Angiostrongylus cantonensis is a rat lungworm. Humans can be infected by ingesting mollusks (eg, undercooked prawns) that are infected with the larval stage of the organism.
- Baylisascaris procyonis is a raccoon nematode that can infect humans if soil contaminated with raccoon feces is ingested. Infection may involve the eye. Eosinophilic meningitis occurs in up to half of baylisascariasis cases and is associated with high mortality rates.
- Gnathostoma spinigerum is a helminth (adult worms infect mammals such as cats, dogs, and raccoons) that causes human infection when larval forms in contaminated animals (eg, fish, chicken, pork) are ingested by humans. Infectious larvae can also directly burrow through skin and infect humans. Patients may present with intracerebral hemorrhage or subarachnoid hemorrhage.
- Coccidioides immitis / posadasii is an endemic fungus found in the United States in the desert southwest (including Arizona and California). Humans can be infected by inhaling arthroconidia of the organism. Infection occasionally results in eosinophilic meningitis.
- Taenia solium is the pork tapeworm and the agent of neurocysticercosis. Humans are infected by eating the eggs of the organism. Occasionally, patients with neurocysticercosis may present with eosinophilic meningitis.
- Paragonimus species are lung flukes that cause human infection following ingestion of contaminated freshwater crustaceans. Patients may have CNS involvement.
- Mycobacterium tuberculosis can cause meningitis, which may occasionally be eosinophilic meningitis.
- Cryptococcus species can cause meningitis, usually in patients who are immunosuppressed (including with AIDS). In some cases, this may be eosinophilic meningitis.
- Hematologic disorders such as hypereosinophilic syndromes and Hodgkin lymphoma in some cases, as well as some other neoplastic etiologies.
- Drug reactions described with ibuprofen (NSAIDs), ciprofloxacin, and trimethoprim-sulfamethoxazole as well as intraventricular gentamicin and vancomycin.
- CSF shunt malfunction.