What are the clinical features, diagnosis, and treatment of eosinophilic meningoencephalitis?

Eosinophilic Meningoencephalitis: Clinical Features, Diagnosis, and Treatment

Eosinophilic meningoencephalitis is primarily treated with corticosteroids (prednisolone 60 mg daily for 14 days) as the mainstay of therapy, with albendazole (15 mg/kg/day for 14 days) as an effective adjunctive treatment for reducing headache duration in cases caused by Angiostrongylus cantonensis. 1, 2

Clinical Features

Common Presenting Symptoms

• Severe acute headache (most common symptom)
• Meningism (neck stiffness, photophobia)
• Visual disturbances
• Paresthesias
• Cranial nerve palsies 1
• Altered consciousness (in severe cases) 3

Advanced/Severe Presentations

• Focal neurological signs
• Seizures
• Hydrocephalus (common in cysticercal meningitis) 1
• Coma (associated with poor prognosis - high mortality rate) 3

Etiology

Common Parasitic Causes

1. Angiostrongylus cantonensis (rat lung worm)

   • Most common cause in Southeast Asia, Caribbean, Hawaii
   • Incubation: 1-3 weeks (range 1 day-3 months)
   • Transmission: Ingestion of larvae in undercooked snails, prawns, crabs, frogs 1, 4

2. Neurocysticercosis (Taenia solium)

   • Common in South/Southeast Asia, Central/South America, Africa
   • Incubation: >1 year
   • Transmission: Fecal-oral route 1, 4

3. Schistosomiasis (S. haematobium, S. mansoni, S. japonicum)

   • Causes myelitis, cerebral involvement
   • Transmission: Freshwater exposure 1

4. Gnathostoma spinigerum

   • Endemic in tropical countries 4

5. Toxocariasis (T. canis, T. catis)

   • Can cause eosinophilic meningoencephalitis 1

Diagnostic Approach

Definition

• Presence of at least 10% eosinophils in CSF leukocyte count 4

Initial Workup

1. Travel history - critical for diagnosis

   • Recent travel to endemic regions (SE Asia, Caribbean, Hawaii, Central/South America)
   • Freshwater exposure
   • Consumption of raw/undercooked foods 1, 5

2. Cerebrospinal Fluid Analysis

   • Eosinophilia in CSF (defining feature)
   • Lymphocytosis (in cysticercal meningitis) 1

3. Blood Tests

   • Peripheral eosinophilia (marked in Angiostrongylus infection)
   • Serology for specific parasites 1, 5

4. Neuroimaging

   • MRI Findings:
     • Prominence of Virchow-Robin spaces
     • Subcortical enhancing lesions
     • Abnormal high T2 signal in periventricular regions
     • Small hemorrhagic tracts (rare)
     • Multiple small high-intensity areas on Gd-DTPA-enhanced T1-weighted images 6, 7
   • CT may be normal in Angiostrongylus infection 1

Treatment

Angiostrongylus cantonensis

• Primary treatment: Corticosteroids (prednisolone 60 mg daily for 14 days) - reduces severity and duration of headache 1
• Adjunctive therapy: Albendazole (15 mg/kg/day for 14 days) - reduces headache duration 1, 2
• Supportive care: Therapeutic lumbar punctures may be necessary to relieve pressure 1

Neurocysticercosis

• Albendazole (400 mg twice daily for 14 days)
• Dexamethasone (4-12 mg/day, reducing after 7 days)
• Ventricular shunting for hydrocephalus
• Repeated courses may be required
• Prognosis is poor in cysticercal meningitis with acute hydrocephalus 1

Schistosomiasis with CNS involvement

• Praziquantel (40 mg/kg twice daily for 5 days)
• Dexamethasone (4 mg four times daily, reducing after 7 days, for 2-6 weeks)
• For acute neuroschistosomiasis (Katayama syndrome): initial treatment with corticosteroids alone 1

Toxocariasis

• Corticosteroids plus albendazole (400 mg twice daily for 5 days) 1

Prognosis and Monitoring

• Regular monitoring of blood counts to confirm resolution is essential 5
• Poor prognosis in severe cases with coma - high mortality rate 3
• Corticosteroids appear ineffective in severe cases with coma 3
• Prompt diagnosis and treatment are crucial to prevent irreversible neurological damage 5

Important Caveats

• Severe cases with coma have extremely poor outcomes - 10/11 patients died in one study 3
• Delayed treatment of persistent hypereosinophilia can lead to irreversible organ damage 5
• Consider empirical treatment when clinical suspicion is high, even if initial testing is negative 5
• Exclude Loa loa in people who have traveled to endemic regions before treating with ivermectin 5