Fungal meningitis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rim Halaby; Prince Tano Djan, BSc, MBChB [2]
Overview
Fungal meningitis results from the infection of the meninges by fungi, most commonly cryptococcus. While cryptococcal meningitis occurs worldwide, other fungal meningitis are endemic to specific regions of the world.[1] Fungal meningitis usually affects immunocompromised patients like HIV patients and transplant recipients on chronic immunosuppression medications. The course of the disease is progressive and may lead to complications if a high dose long term treatment with antifungals are not initiated.[2]
Pathophysiology
The pathophysiology of fungal meningitis is not very well studied but it is known to have a lot of similarities with bacterial meningitis. Fungal meningitis usually occurs in immunocompromised patients. The initial step in fungal meningitis is the pulmonary exposure to the fungi by the inhalation of airborne fungal spores. The pulmonary infection is usually self limited and maybe asymptomatic. Fungal infections are not contagious so they do not spread from one person to another. In most cases of fungal meningitis, the fungi then undergo hematogenous spread and cross the blood brain barrier causing an infection of the meninges.
Causes
Fungal meningitis is initially caused by the inhalation of airborne fungal spores. The pulmonary infection is usually self limited and can be asymptomatic. The most common cause of fungal infection is C. neoformans which is usually found in soil and bird excreta.[3]
Differentiating (Disease name) from other Conditions
The differential diagnosis of fungal meningitis includes a range of medical conditions that can be broadly classified into infectious and non infectious. The cerebrospinal fluid analysis and radiological findings help distinguishing fungal meningitis from other etiologies.
Epidemiology and Demographics
While cryptococccus and candida infections occur worldwide, other fungal infections tend to cluster in specific geographical regions. The most common cause of fungal meningitis is Cryptococcus neoformans.
Risk Factors
Fungal meningitis rarely occurs in otherwise healthy individuals. Co-existing medical conditions, immunosuppression and travel history to areas where specific fungi are endemic are risk factors for fungal meningitis.
Natural History, Complications and Prognosis
Fungal meningitis usually presents with progressive symptoms of headache, low grade fever and fatigue. If left untreated, neurological complications might occur.
Diagnosis
History and Symptoms
Fungal meningitis can occur in two main clinical pictures: subacute meningitis and chronic meningitis. Chronic meningitis is characterized by the presence of symptoms for more than four weeks. Symptoms include headache, low grade fever, fatigue, weight loss and sometimes focal neurological deficits.
Physical Examination
As in the case of any disease, a complete physical exam must be done on the patient looking for positive and negative symptoms. The clinical presentation of fungal meningitis is usually obscure as are the findings on physical exam. The pertinent findings are low grade fever and possible neurological signs like focal weakness, loss of sensation and cranial nerves involvement.
Laboratory Findings
A lumbar puncture is essential for the diagnosis of fungal meningitis and initiation of the appropriate treatment. The cerebrospinal fluid (CSF) of a patient having bacterial meningitis is distinguished by the presence of lymphocytosis, low glucose level and high proteins level. Specific CSF stains and cultures as well as serologies help in determining the specific nature of the causative fungi.
CT
The diagnosis of fungal meningitis mainly relies on the results of the cerebrospinal fluid (CSF) analysis, stain and culture. The role of imaging is to rule out other differential diagnosis of the initial presentation. In addition, brain imaging must be done when the patient has signs of increased intracranial pressure to prevent brain herniation.
Treatment
Fungal meningitis, such as cryptococcal meningitis, is treated with long courses of high dose antifungals. In addition, frequent lumbar punctures are recommended in order to relieve the increased intracranial pressure[4].
References
- ↑ Bovers M, Hagen F, Kuramae EE, Diaz MR, Spanjaard L, Dromer F; et al. (2006). "Unique hybrids between the fungal pathogens Cryptococcus neoformans and Cryptococcus gattii". FEMS Yeast Res. 6 (4): 599–607. doi:10.1111/j.1567-1364.2006.00082.x. PMID 16696655.
- ↑ Gottfredsson M, Perfect JR (2000). "Fungal meningitis". Semin Neurol. 20 (3): 307–22. doi:10.1055/s-2000-9394. PMID 11051295.
- ↑ Koroshetz WJ. Chapter 382. Chronic and Recurrent Meningitis. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J, eds. Harrison's Principles of Internal Medicine. 18th ed. New York: McGraw-Hill; 2012.
- ↑ Bicanic T, Harrison TS (2004). "Cryptococcal meningitis". Br Med Bull. 72: 99–118. doi:10.1093/bmb/ldh043. PMID 15838017.