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Eosinophilic meningitis — Clinical Guidelines

Overview

Eosinophilic meningitis is a clinical syndrome characterized by inflammation of the meninges, predominantly mediated by eosinophils, often resulting from parasitic infections, particularly those caused by Angiostrongylus cantonensis. This condition is clinically significant due to its potential for causing severe neurological symptoms and, in rare cases, significant morbidity or mortality. It predominantly affects individuals in endemic regions who consume undercooked or raw intermediate hosts such as snails, slugs, or crustaceans harboring the parasite. Understanding and timely recognition of eosinophilic meningitis are crucial in day-to-day practice to prevent complications and ensure appropriate management, especially in endemic areas 1 2 3.

Pathophysiology

The pathophysiology of eosinophilic meningitis induced by Angiostrongylus cantonensis involves several key steps. Initially, ingestion of infected intermediate hosts leads to the ingestion of third-stage larvae, which migrate through the intestinal mucosa and enter the bloodstream. These larvae then disseminate to various organs, including the central nervous system (CNS). Once in the CNS, the larvae fail to mature fully due to the hostile environment, leading to their death and subsequent release of antigens. This triggers a robust immune response, predominantly mediated by eosinophils, which infiltrate the meninges and cerebrospinal fluid (CSF). The inflammatory cascade involves the upregulation of chemokines like eotaxin and the activation of matrix metalloproteinases (MMPs), contributing to meningeal inflammation, increased CSF cell counts, and neurological symptoms 1. Additionally, the host's immune response, characterized by elevated eosinophil counts and increased levels of inflammatory mediators, plays a critical role in the clinical manifestations observed in patients 1 2.

Epidemiology

Eosinophilic meningitis due to Angiostrongylus cantonensis is most prevalent in regions where the parasite's life cycle is established, including parts of Asia, the Pacific Islands, and occasionally in the Americas. Between 1959 and 1976, 34 cases were documented in Hawaii, with presumed infections primarily linked to the consumption of raw terrestrial snails or slugs, and less commonly, crustaceans 2. In Tahiti, a study of 54 patients highlighted the endemic nature of the condition, with a notable seasonal variation linked to dietary habits involving contaminated seafood 3. The incidence tends to be higher in younger populations and those with dietary practices involving raw or undercooked intermediate hosts. While specific incidence rates are not universally reported, the condition underscores the importance of public health measures in endemic areas to reduce exposure risks 2 3.

Clinical Presentation

Patients with eosinophilic meningitis typically present with a constellation of neurological and systemic symptoms. The hallmark symptoms include severe headaches, often accompanied by neck stiffness, though fever is usually mild or absent 2 3. Additional common features include paresthesias, particularly in adult patients, and varying degrees of limb pain or weakness. Some patients may exhibit cranial nerve palsies, such as facial palsy, further complicating the clinical picture. Atypical presentations can include altered mental status in severe cases, though these are less frequent. Red-flag features that warrant immediate attention include significant neurological deficits, persistent fever, or signs of increased intracranial pressure, which may necessitate urgent neuroimaging and CSF analysis 2 3.

Diagnosis

The diagnosis of eosinophilic meningitis involves a combination of clinical evaluation and laboratory investigations. Key steps include detailed patient history focusing on dietary exposures and travel history to endemic areas. The diagnostic approach typically includes:

Cerebrospinal Fluid (CSF) Analysis:

- Elevated CSF leukocyte count (often >100 cells/mm3) 3. - Predominant eosinophilic pleocytosis (mean eosinophil percentage >38%) 2. - Normal or mildly elevated protein levels. - Normal glucose levels unless complicated by other factors.

Imaging:

- MRI or CT scans may show nonspecific meningeal enhancement or no abnormalities in early stages 2.

Parasitological Confirmation:

- Direct detection of Angiostrongylus cantonensis larvae in CSF, though rare 4.

Differential Diagnosis:

Other Parasitic Meningitis: Such as neurocysticercosis (characterized by cysts in imaging).

Bacterial Meningitis: Typically presents with higher fever, more severe systemic symptoms, and often abnormal CSF glucose levels.

Viral Meningitis: Usually milder, with less pronounced eosinophilia and often a more rapid resolution.

Toxoplasmosis: Can present with focal neurological signs and characteristic ring-enhancing lesions on MRI 2 3.

Management

First-Line Treatment

Supportive Care:

- Symptomatic treatment with analgesics (e.g., NSAIDs) for headache. - Hydration and close monitoring of neurological status.

Antiparasitic Therapy:

- Albendazole: 400 mg twice daily for 7-14 days 1. - Combination Therapy: Albendazole plus baicalein (a flavonoid) has shown synergistic efficacy in preclinical studies, though human data are limited 1.

Second-Line Treatment

Adjunctive Therapy:

- Corticosteroids (e.g., prednisone 40-60 mg daily) may be considered to reduce inflammation and alleviate symptoms, particularly in severe cases 2. - Antihistamines (e.g., cetirizine) for pruritus if present.

Refractory Cases / Specialist Escalation

Consultation:

- Neurology consultation for persistent neurological deficits or complications. - Infectious disease specialist for complex cases or refractory symptoms.

Further Investigations:

- Repeat CSF analysis and imaging if symptoms persist or worsen. - Consider additional serological testing for other potential pathogens.

Contraindications:

Albendazole should be used cautiously in patients with hepatic impairment or known hypersensitivity to benzimidazoles 1.

Complications

Common complications of eosinophilic meningitis include:

Persistent Neurological Symptoms: Such as chronic headaches, cognitive impairment, and motor deficits.

Increased Intracranial Pressure: Rare but serious, requiring urgent intervention.

Secondary Infections: Due to immunosuppression or invasive procedures like lumbar puncture.

Referral to neurology or infectious disease specialists is warranted if complications arise, particularly if there is evidence of neurological deterioration or persistent symptoms 2.

Prognosis & Follow-Up

The prognosis for eosinophilic meningitis is generally favorable, with most patients experiencing complete recovery without specific antiparasitic treatment 2 3. However, recovery can be prolonged in some cases, lasting weeks to months. Key prognostic indicators include the severity of initial symptoms and the presence of complications. Recommended follow-up includes:

Neurological Assessments: At 1-2 weeks, 1 month, and 3 months post-onset.

CSF Analysis: If symptoms persist, repeat CSF analysis to rule out persistent infection or complications.

Imaging: Repeat MRI if neurological deficits are noted or if there is suspicion of residual pathology.

Special Populations

Pediatrics: Children may present with more pronounced neurological symptoms due to their developing nervous systems. Close monitoring and supportive care are essential 2.

Elderly: Older adults might experience more severe complications due to comorbid conditions and potentially reduced immune function. Tailored supportive care and early specialist referral are advised 2.

Comorbidities: Patients with pre-existing neurological conditions or immunosuppression require heightened vigilance and possibly more aggressive management strategies 2.

Key Recommendations

Perform CSF analysis with emphasis on eosinophilic pleocytosis for diagnosis (Evidence: Strong 2 3).

Initiate supportive care including hydration and symptomatic treatment for headache (Evidence: Strong 2).

Consider albendazole as first-line antiparasitic therapy at 400 mg twice daily for 7-14 days (Evidence: Moderate 1).

Evaluate for and manage complications such as increased intracranial pressure or persistent neurological deficits (Evidence: Moderate 2).

Repeat neurological assessments and CSF analysis in cases with persistent symptoms (Evidence: Moderate 2).

Consult neurology or infectious disease specialists for refractory cases or complications (Evidence: Expert opinion).

Monitor pediatric and elderly patients closely due to higher risk of complications (Evidence: Expert opinion).

Consider corticosteroids for severe cases to reduce inflammation (Evidence: Moderate 2).

Avoid albendazole in patients with significant hepatic impairment or known hypersensitivity (Evidence: Expert opinion).

Educate patients on dietary precautions to prevent reinfection in endemic areas (Evidence: Expert opinion).

References

1 He HJ, Lv ZY, Li ZY, Zhang LY, Liao Q, Zheng HQ et al.. Efficacy of combined treatment with albendazole and baicalein against eosinophilic meningitis induced by Angiostrongylus cantonensis in mice. Journal of helminthology 2011. link 2 Kuberski T, Wallace GD. Clinical manifestations of eosinophilic memingitis due to Angiostrongylus cantonensis. Neurology 1979. link 3 Bronstein JA, Thevenot J, Tourneux M. Eosinophilic meningitis in Tahiti: clinical study of 54 patients. The New Zealand medical journal 1978. link 4 Nitidandhaprabhas P, Harnsomburana K, Thepsitthar P. Angiostrongylus cantonensis in the cerebrospinal fluid of an adult male patient with eosinophilic meningitis in Thailand. The American journal of tropical medicine and hygiene 1975. link

Eosinophilic meningitis