Introduction

Fungal meningitis is a fungal infection of the brain and/or spinal cord (also termed the central nervous system). This means that fungi have inflamed the tissues surrounding one's brain and spinal cord.¹ Fungal meningitis is less common than bacterial meningitis, nevertheless, it is just as life-threatening and requires treatment as soon as possible when detected.²

Fungal meningitis is a rare disease, however, between 2010 and 2020, about 1 million cases were detected worldwide per year.² It should also be noted that the overall disease burden of fungal meningitis has decreased due to the availability of novel treatments.³

Causes and risk factors

Fungal infections of the central nervous system (CNS) usually originate from a systemic fungal infection that has occurred elsewhere in the body and subsequently spread to the CNS.^4,5 However, several predisposing factors increase a person’s susceptibility to invasive fungal infections.⁶ 

There is not one distinct fungus that causes fungal meningitis, but several types of fungi that can. These are usually subcategorised into 3 types:⁶ 

1. Yeasts 
2. Moulds or filamentous fungi 
3. Dimorphic fungi

Most of these fungi live in the environment and can enter the body by one breathing in their fungal spores. Once in the body, the fungi can spread across the body to the lungs, heart and eventually the CNS.¹

One key factor that could increase a patient’s susceptibility to fungal meningitis is if their immune system is compromised. This means that the patient already has a pre-existing immune deficiency, which makes it more difficult for the body to fight off pathogens with an appropriate immune response.⁴ Additionally, patients undergoing chemotherapy for cancer treatment or suffering from a chronic disease will also be at higher risk.^6,7 

Conditions where the immune system is compromised include HIV/AIDS or patients who have received an organ transplant.^3,5,6 HIV is a virus that attacks the immune system, therefore weakening its ability to fight off any infections and diseases. People with AIDS (later stage of HIV infection) have a very weak immune system and are at especially high risk of fungal infections.⁸ Similarly, organ transplant recipients receive medications that are used to suppress their immune system to prevent the body from rejecting the new organ. However, this suppression will also make it more difficult to fight off other infections such as fungal meningitis.⁹ 

Patients suffering from chronic diseases will also be more susceptible to fungal meningitis. This can be drawn back to a similar reason as with HIV patients, wherein patients suffering from chronic disease will have a weakened immune system either directly or indirectly through medications that suppress the immune system.^6,7 

It needs to be noted that not only immunocompromised patients can contract fungal meningitis, but immunocompetent people can too. Two types of fungi can be found in bird droppings and contaminated soil.⁶ When these are inhaled, their spores can lodge in the lungs and grow there. In some cases, the fungus can then travel from the lungs to the CNS and cause inflammation and fungal meningitis.^6,10 

Signs and symptoms

As fungal meningitis can affect the brain and spinal cord, most symptoms that will be experienced affect skills controlled by the brain. Various symptoms include:^1,5,11

• Headaches 
• Nausea and vomiting
• Visual impairment 
• Neck stiffness
• Fever 
• Seizures
• Personality changes 

Diagnosing fungal meningitis comes with the difficulty of misdiagnosing the patient with a different cause. This is a challenge as fungal meningitis presents similar to other brain diseases and infections such as brain abscesses or bacterial meningitis. In order to immediately establish the correct diagnosis, aspects such as risk factors, geographic location of patients and the presence of fungal infection in other systemic organs need to be taken into consideration.^5,11 

Prompt diagnosis and treatment of fungal infections are crucial in fungal meningitis.⁶ Fungal meningitis is a serious infection that can be life-threatening as the fungus causes inflammation and swelling of the protective membranes surrounding the brain and spinal cord. If this is not treated promptly, the inflammation can cause damage to the brain tissue and lead to serious complications.¹²

Additionally, antifungal medications often need to be taken for extended periods. Early diagnosis therefore allows for treatment to begin promptly.^11,12 By promptly diagnosing and treating fungal meningitis, doctors can significantly improve the chances of a full recovery and minimize the risk of serious complications. 

Diagnostic approaches 

Diagnosing fungal meningitis relies heavily on laboratory tests performed on samples collected from the patient. 

Key laboratory tests for diagnosis include spinal taps (also called a lumbar puncture) and a fungal culture. During a spinal tap, a thin needle is inserted into the patient's lower back to collect cerebrospinal fluid (CSF) – the fluid that surrounds the brain and spinal cord – which is then analysed for any abnormalities. ¹³ Furthermore, a sample of this collected CSF can be cultured in a special medium to see if the fungus continues to grow.^6,12

Depending on the situation, other tests might be used to aid in the diagnosis. These can include imaging studies, wherein CT scans or MRIs of the brain may be used to look for inflammation or swelling.^1,12 In other cases, biopsies can be undertaken. During a biopsy, the doctor will take a sample of the brain tissue or other affected areas which will then be examined under a microscope for the presence of the fungus.¹³ 

Treatment 

Based on the type of fungus that was established during diagnosis, doctors will prescribe a specific antifungal medication. Common antifungal medications include amphotericin B, fluconazole, itraconazole, posaconazole, and isavuconazole.^13,14 These medications are typically administered intravenously (into a vein) for the initial phase of treatment, especially in severe cases.⁵ If improvement is in sight, the patient may be transitioned to oral medication for an extended period often lasting weeks to months. The total duration, however, depends on the severity of the infection, the immune system strength, and the specific fungus involved.¹⁴

Alongside the primary antifungal treatment, doctors will provide supportive care to manage pain and symptoms. This can include pain relievers, fluids and electrolytes.¹⁵ In some rare cases, surgical intervention may be necessary if the infection and complications increase. 

Early diagnosis and treatment are critical for a good prognosis in fungal meningitis. The success of treatment depends highly on various factors including types of fungus, the severity of infection upon diagnosis, and the patient’s overall health.^13-16

Prevention 

As with many diseases, there is no guaranteed way to prevent fungal meningitis, but several measures can be undertaken to significantly reduce your risk. This includes things as easy as taking care of your general hygiene including washing hands frequently and wearing masks.⁶ For people with weakened immune systems, prophylactic medication might be prescribed such as preventative antifungal medication to reduce the risk of contracting fungal infections.¹⁵ These patients should minimize exposure by avoiding high-risk environments such as areas contaminated with bird droppings.^6,14 

Summary 

Fungal meningitis can be a life-threatening infection of the brain and spinal cord caused by fungi that can be found in bird droppings or contaminated soil. It needs to be noted that patients with an already compromised immune system are at higher risk of infection. Gradual onset of symptoms includes fever, headaches, nausea, and vomiting. As these symptoms are commonly found in other diseases too, differential diagnosis is crucial, particularly to initiate adequate treatment. This includes antifungal medications, supportive care and in serious conditions, surgery. 

Future outlooks for better outcomes in fungal infections of the meninges include not only improved diagnostics for faster and more accurate tests for earlier detection but also exploring strategies to optimize treatment outcomes by developing combination therapies or targeted therapies. 

The key takeaway for fungal meningitis is that early diagnosis and treatment are crucial for a good prognosis.