Eosinophilic meningitis (EM) is a rare form of meningitis characterized by an elevated eosinophil count in the cerebrospinal fluid (CSF).
It is defined by the presence of 10 or more eosinophils per microliter of CSF or eosinophils accounting for at least 10% of the total white blood cells in the CSF.
The most common cause of eosinophilic meningitis is infection by helminthic parasites, particularly Angiostrongylus cantonensis, also known as the rat lungworm.
Patients present with symptoms such as severe headache, neck stiffness, paresthesia, and nausea/vomiting.
The most common symptoms and signs of EM are:
sudden intense headache stiff neck and inability to flex your neck forward (nuchal rigidity) paresthesia abdominal pain nausea vomiting photophobia fever itchy rash Psoriasis, an autoimmune condition.
The diagnosis is often supported by a history of consuming raw or undercooked snails, slugs, or contaminated vegetables, which are common sources of A. cantonensis larvae.
Treatment involves supportive care, including the management of inflammation and intracranial pressure.
Corticosteroids may be used to reduce inflammation and alleviate symptoms.
The use of antihelminthic agents is generally avoided due to the risk of exacerbating the inflammatory response to dying larvae.
Doctors rarely treat the infection itself because researchers haven’t observed a clear benefit of this approach.
Diagnosis: lumbar puncture for diagnosis, noting that elevated intracranial pressure should prompt removal of a large volume of CSF to relieve symptoms.
Eosinophilic meningitis most often develops from certain parasites that normally infect animals, not people.
Eosinophilic meningitis is much less common than viral or bacterial meningitis.
Some people may be at risk of eosinophilic meningitis because of where they live, travel, or work.
Several types of helminth worms cause EM:
Angiostrongylus cantonensis (rat lungworm) Baylisascaris procyonis (a raccoon roundworm) Gnathostoma spinigerum
These parasites can enter the body through contaminated water or interact with the stool or droppings of an infected animal, and eventually spread to your brain or spinal cord, where it can cause EM.
Rarer causes of EM include:
Cocciodioides fungi, common in the southwestern United States tuberculosis neurosyphilis Rocky Mountain spotted fever
Possible complications of eosinophilic meningitis:
loss of coordination and muscle control weakness paralysis permanent disability coma death
Mild cases of EM are more common and usually resolve on their own within a few weeks.
More than 90% of people who entered a coma due to rat lungworm infection eventually die.
Neurological symptoms of EM are usually associated with a poor outlook.
Rat lungworms are common in: Southeast Asia the Pacific Islands, including Hawaii Australia
Rat lungworms can infect people who eat raw: snails slugs frogs freshwater prawns crabs fish
Less commonly, it can exist in contaminated vegetables, water, and fruit juice.
Babies, toddlers, and young children can contract an infection after playing with snails or other animals and then touching their mouths.