What is Meningitis (Eosinophilic meningitis)

Meningitis - Eosinophilic meningitis Meningitis is defined as inflammation of the meninges. Meninges are thin membranes that cover the spinal cord and the brain. There are many causes of meningitis, most commonly infection. Depending on the types of bugs that causes the infection, there will be different immunological cells in the cerebrospinal fluid (CSF – the fluid that surrounds the brain and spinal cord). In eosinophilic meningitis, there is increased number of eosinophils in the CSF. Eosinophil is a type of white blood cell responsible to fight off parasitic infection or to mount an allergic response.

Statistics on Meningitis (Eosinophilic meningitis)

The incidence of eosinophilic meningitis is unknown, but it is considered to be a rare disease.

Risk Factors for Meningitis (Eosinophilic meningitis)

Because most eosinophilic meningitis is caused by parasitic infestation of the meninges, any risk factors that predispose individuals to such exposure will increase the risk of eosinophilic meningitis. Areas of low socioeconomic status and personal hygiene, especially in the tropics increase the risk of infection. This include accidental ingestion of raw seafood, fish and poultry. Ingestion of raw mollusc or food contaminated with raccoon faeces can increase the risk as well.

Progression of Meningitis (Eosinophilic meningitis)

The most common cause of eosinophilic meninigitis is parasitic infestation. Several parasites have been identified to cause eosinophilic meninigitis, including:

  • Angiostrongylus cantonensis
  • Baylisascaris procyonis
  • Gnathostoma spinigerum

Another cause of eosinophilic meningitis is fungal infection. The one that causes it is Coccidioidomycosis. Other non-infectious cause is idiopathic hypereosinophilic syndrome. It is a blood disease where the number of eosinophils (a type of white blood cell) rises in the blood without any known causes. There is no apparent parasitic, allergic or other causes found. Other than this, Hodgkin’s disease is the commonest cancer associated with eosinophilic CSF (this does not necessarily mean meningitis). Otherwise, drug-induced eosinophilia in CSF can occur as well. These drugs include ibuprofen (a pain-killer) and certain antibiotics.

How is Meningitis (Eosinophilic meningitis) Diagnosed?

Patients having features suggestive of eosinophilic meningitis are usually admitted to the hospital for observation and treatment. Therefore, a general routine investigation will be done, and this include looking at the blood function, liver function, kidney function and the body’s electrolyte balance.

Prognosis of Meningitis (Eosinophilic meningitis)

The outcome of eosinophilic meningitis depends on the cause of it. Parasitic meningitis generally resolves after supportive treatment. In one study of 484 cases of eosinophilic meningitis in Thailand due to angiostrongyliasis, the mortality rate was less than 0.5%. However, gnathostomiasis causing eosinophilic meningitis is usually more serious than angiostrongyliasis due to the nature of infection leading to tissue destruction and severe inflammation.

How is Meningitis (Eosinophilic meningitis) Treated?

Depending on the causative agent, treatment usually consists of supportive measures, and antihelminth agents. Antihelminths agents are drugs used to treat the parasites. Supportive measures include reducing the temperature, maintaining the hydration status of the patient, and providing reassurance to the patient and relatives. In angiostrongyliasis, usually antihelminthic agent is not given. Symptomatic relief of headache may include repeating lumbar punctures. If the disease remains unresponsive antihelminths can be administered. In gnathostomiasis, because the disease progression is more serious, usually corticosteroid is added. In other kinds of eosinophilic meningitis, the treatment options would be treating those diseases themselves and will not be discussed here.

Meningitis (Eosinophilic meningitis) References

  1. Asperilla, MO, Smego, RAJ. Eosinophilic meningitis associated with ciprofloxacin. Am J Med 1989; 87:589.
  2. Bronstein, JA, Thevenot, J, Tourneux, M. Eosinophilic meningitis in Tahiti: Clinical study of 54 patients. N Z Med J 1978; 88:491.
  3. Kuberski T. Eosinophils in the cerebro spinal fluid. Ann Intern Med 1979;91:70-75.
  4. Lo Re, V, Gluckman, SJ. Eosinophilic meningitis. Am J Med 2003; 114:217.
  5. Punyagupta, S, Juttijudata, P, Bunnag, T. Eosinophilic meningitis in Thailand. Clinical studies of 484 typical cases probably caused by Angiostrongylus cantonensis. Am J Trop Med Hyg 1975; 24:921.
  6. Quinn, JP, Weinstein, RA, Caplan, LR. Eosinophilic meningitis and ibuprofen therapy. Neurology 1984; 34:108.
  7. Up to Date: Eosinophilic meningitis [online]. 2005. [Cited 2005 October 15th]. Available from: URL: http://www.utdol.com/application/topic.asp?file=parasite/8476&type=A&selectedTitle=1~3.

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