Fungal meningitis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 28, 2016
StartDiseasesFungal meningitis

Fungal meningitis is a rare form of meningitis caused by fungus that has spread through blood and infected the spinal cord and/or brain. The disease is most commonly caused by Cryptococcus neoformans infection, usually when the fungi are inhaled. This rare type of meningitis gained national headlines in the U.S. when contaminated epidural corticosteroid injections killed eight and exposed 13,000 patients.

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Definition & Facts

Fungal meningitis is a rare but life-threatening fungal infection of the central nervous system. The disease is not contagious and usually develops when the fungus enters the blood from somewhere else, such as inhaling spores from contaminated soil.

As with all cases of meningitis, fungal meningitis involves inflammation of the meninges which are the membranes protecting the spinal cord and brain. These membranes are called dura mater, arachnoid mater, and pia mater.

While anyone can develop fungal meningitis, it usually affects people with weakened immune systems. Fungi responsible for meningitis, including Cryptococcus and Candida (fungus), are usually harmless to people with a healthy immune system.

Symptoms of fungal meningitis may include vomiting, nausea, fever, headache, neck stiffness, hallucinations, and changes in mental state. Antifungal medication is the most common treatment.

Symptoms & Complaints

Symptoms of fungal meningitis typically begin slowly after infection, usually over the course of a few days or even a few weeks. Symptoms resemble other forms of meningitis and may include confusion, vomiting, nausea, headache, fever, stiff neck, sensitivity to light, blurred vision, fast heart rate (tachycardia), and hallucinations. These symptoms typically worsen progressively over the course of weeks.

While these symptoms are similar to viral meningitis and bacterial meningitis, the symptoms of fungal meningitis usually develop more slowly with a slow onset that becomes very severe. This can make the infection harder to diagnose for physicians and patients may take longer to see a doctor. While very common, headache caused by fungal meningitis are typically less debilitating and excruciating than those caused by viral or bacterial meningitis.

In severe cases, meningitis can affect the blood vessels, causing bleeding, clots, and difficulty speaking or maintaining stability. These symptoms may be mistaken for a stroke

Causes

Most cases of fungal meningitis are caused by the fungus Cryptococcus neoformans, which is typically found in soil. Also called cryptococcal meningitis, this form of the disease may be contracted by inhaling soil particles contaminated with the fungi. Fungal meningitis may also be caused by the fungus Candida albicans that causes candidiasis (thrush), although this is far less common.

Different types of fungus may be transmitted in different ways. For example, Crytococcus is usually transmitted by inhaling soil contaminated with bird droppings whereas Histoplasma fungus is found in environments contaminated with bat or bird droppings. People with compromised immune systems may develop meningitis from an infection by the Histoplasma fungus, which is typically harmless. Most cases develop after environmental contact with fungus, but some people develop fungal meningitis due to contaminated medications.

While anyone can get fungal meningitis, it is most common in people with weakened immune systems, including people with HIV/AIDS or cancer, people who have had surgical procedures like organ transplants or people who take immunosuppressive drugs steroids or certain medications to treat rheumatoid arthritis.

Premature babies with low birth weights are at a higher risk of getting Candida infection in the blood which can spread to the brain. The disease is not contagious, that is, it is not transmitted from person to person, and it is very rare among people who have a healthy immune system. 

Diagnosis & Tests

Fungal meningitis can be diagnosed in several ways. A computed tomography (CT) scan that takes images of the brain and skull may be able to diagnose the disease. A magnetic resonance imaging (MRI) scan of the brain, skull, and blood vessels may also assist physicians with determining the extent of the infection.

A lumbar puncture or spinal tap is the most common method of diagnosing meningitis. This procedure requires inserting a needle into the spine to withdraw and test cerebrospinal fluid (CSF) surrounding the spinal cord. A spinal tap can detect infections in the brain and spinal cord.

Other tests that may be done include a chest X-ray, blood cultures, and cryptococcal antigen testing in the CSF or blood to look for antibodies of the fungi. Blood cultures are not typically used to diagnose meningitis as the culture will not be positive except in a heavy fungal infection.

Testing for cryptococcal antigens from cerebrospinal fluid is generally viewed as the best diagnostic tool for cryptococcal meningitis because the test is very sensitive. Unfortunately, it can be very hard to get fungus to grow in laboratory settings and some people will test negative for fungus after a lumbar puncture, even if they have the infection.

Physicians generally look for other signs of infection in the spinal fluid, including an elevated number of white blood cells (leukocytosis).

Treatment & Therapy

A few forms of treatment may be used to combat fungal meningitis. The most common treatment is a course of antifungal medication that kills the fungus causing the infection. A long course of antifungal medication that is specific to the type of fungus is usually administered intravenously in a hospital.

The antifungal amphotericin B is commonly used in IV therapy and combined with the oral antifungal medication 5-flucytosine. Fluconazole, another oral medication, may be given in high doses later in the treatment to fight the fungal infection. Steroids may also be necessary to reduce inflammation.

Cryptococcal meningitis is often fatal, even when treated, with a three-month fatality rate of 9% in high-income regions. People recovering from cryptococcal meningitis often require long-term maintenance treatment with medication that prevents the fungal infection from returning. This is also true of people with weakened immune systems. Fungal meningitis is most common in people with HIV/AIDS and treatment options for people without HIV have not been thoroughly researched.

Prevention & Prophylaxis

There are no vaccines that offer protection against fungal meningitis as there are against certain types of viral meningitis and bacterial meningitis. The most important way to prevent the disease is avoiding the soil in which the fungi live.

This is especially important for people with weakened immune systems, who should avoid gardening and disturbing soil without protection against airborne particles.