What is Cryptococcal Meningitis?
Cryptococcosis is a significant infection that often affects individuals with weakened immune systems, causing over 100,000 HIV-related deaths each year. The disease was first identified by Otto Busse and Abraham Buschke in 1894, leading to it being named the Busse-Buschke disease.
While the infection is commonly linked to HIV, in many medical facilities, particularly in developed countries, a substantial number of patients affected are those undergoing treatments that weaken the immune system or those with issues affecting the normal functioning of their organs. These could include people who have undergone transplants, those with innate immune system issues, individuals with a condition known as common variable immunodeficiency syndrome, and those with blood disorders.
What Causes Cryptococcal Meningitis?
Cryptococcus is a type of fungus with over 50 species, but most infections in humans are caused by just two: C. neoformans and C. gattii.
C. neoformans is a type of yeast that’s often found in old pigeon droppings. The infections it causes can range from mild to severe. It might simply colonize a person’s airways or cause no symptoms at all in people who work in labs. However, in severe cases, it can lead to meningitis or disseminated disease, where the infection spreads throughout the body. This yeast is the most common Cryptococcus found in temperate climates, including regions like Brazil.
People with HIV are particularly prone to infections from Cryptococcus. However, there are other factors that can predispose people without HIV to get cryptococcal infections:
– Certain syndromes and autoantibodies: These include issues like idiopathic CD4 lymphopenia, pulmonary alveolar proteinosis with autoantibodies to granulocyte-macrophage colony-stimulating factor, and autoantibodies to interferon-gamma.
– Monogenic disorders: Some genetic mutations can make some people more prone to these infections, like primary immunodeficiency due to GATA2 mutations, chronic granulomatous disease, Hyperimmunoglobulin E recurrent infection syndrome (Job syndrome), or X-linked CD40L deficiency (hyper-IgM syndrome).
– Polygenetic modifiers: Certain gene variants like Fc gamma receptor (FCGR) II polymorphism can also predispose people to these infections.
– Comorbid conditions: People with conditions like sarcoidosis, autoimmune diseases, steroid treatment, liver diseases, or those who have received solid organ transplants might also be more susceptible.
Risk Factors and Frequency for Cryptococcal Meningitis
Every year, around 1 million cases of a brain infection called cryptococcal meningitis are reported. This infection has become more common since the 1950s due to the use of certain medications called corticosteroids and the increased survival rates in cancer patients. Most of these infection reports surfaced in the 1980s and are mainly associated with AIDS. About 6% of individuals with AIDS get this infection, and they represent 85% of all people diagnosed with cryptococcosis.
Signs and Symptoms of Cryptococcal Meningitis
Cryptococcal meningitis is a condition that usually shows up as a slower progressing inflammation of the brain and its surrounding tissues. The person may often have brain-related symptoms like a headache, changes in the way they think and act, and signs of tiredness, fever, stiff neck, nausea, and vomiting. In cases where the person also has HIV, the symptoms might be minimal or not very specific when they first show up.
The symptoms usually start to show 1 to 2 weeks after exposure in people with HIV and 6 to 12 weeks in people without HIV.
- Double vision and sensitivity to light at the beginning
- Later, there may be loss of sharpness in vision because of too much fluid pressure in their brain or squeezing of the optic nerves and pathways
- Other possible signs include hearing loss, lack of coordination, difficulty speaking, seizures, and irregular, jerking movements
Even though the Cryptococcus neoformans, the organism causing the condition, enters the body through the lungs, the brain and its surrounding tissues are the main areas where obvious symptoms of the infection can be seen.
Testing for Cryptococcal Meningitis
When you go to your doctor for an initial evaluation, they will have to run some tests. They might look at your cerebral spinal fluid (CSF) – a clear, colorless fluid found in your brain and spinal cord – via different lab tests. If there’s a risk of a brain herniation – a life-threatening type of stroke – after a dural puncture, your doctor may decide to perform a CT scan or MRI of your brain, or a fundus examination (a simple procedure that checks the back of your eye) before performing a lumbar puncture.
Your blood and CSF should also be checked for fungal growth and for a specific antigen associated with an infection caused by Cryptococcus fungi. It’s important to note that even if your disease has spread, routine lab tests may still appear normal. However, the pressure of your CSF, measured during the first spinal tap, can indicate the seriousness of your condition. A pressure reading over 25 cm of water is usually a sign of a poor prognosis.
Generally, in such cases, your CSF will show low glucose and high protein levels. The count of white blood cells (cells of the immune system involved in protecting the body against diseases) can be normal or slightly raised, with a dominance of lymphocytes. Even so, the CSF can appear normal but still test positive on the India ink stain test and antigen testing (especially in HIV-positive patients who may not have a normal immune response).
Treatment Options for Cryptococcal Meningitis
According to the 2010 Infectious Diseases Society of America (IDSA) update, the treatment approach for certain types of patients hasn’t significantly changed over the past decade. Here’s a summary of the recommended treatments:
For patients with HIV-related disease, the primary form of treatment comprises three stages: induction, consolidation, and maintenance.
During the induction stage, there are various options, including Amphotericin B deoxycholate and Flucytosine. Treatment typically lasts two weeks, but for those who do not tolerate Flucytosine, it can extend to 4-6 weeks. Alternatives include Amphotericin B deoxycholate combined with fluconazole, fluconazole combined with flucytosine, fluconazole alone, and itraconazole.
The consolidation stage involves fluconazole for approximately two months, while maintenance therapy extends for a year or more, typically with lower doses of fluconazole. Alternatives for maintenance therapy include itraconazole and Amphotericin B deoxycholate.
For transplant-related disease, treatment again involves an induction, consolidation, and maintenance phase. Induction largely involves using liposomal amphotericin B or amphotericin B lipid complex combined with flucytosine. The doses of fluconazole are higher for consolidation and maintenance therapy compared to those with HIV-related disease.
For individuals without HIV or a transplant-related condition, the treatment is similar. However, the induction phase may be prolonged to 4-6 weeks, and maintenance therapy is given for 6 to 12 months.
Researchers have found that the combination of amphotericin B and flucytosine is the most effective for clearing the infection and has a greater survival rate compared to using amphotericin alone. However, flucytosine can be costly and isn’t always available in places with limited resources where the disease is prevalent. Hence, combinations of amphotericin B and fluconazole have been studied and found to be more effective than amphotericin B alone.
Without treatment, symptoms can worsen to confusion, seizures, unconsciousness, and eventually coma.
Patients with headaches that don’t improve with painkillers may be treated with spinal decompression, a procedure that involves removing fluid with a lumbar puncture, after a thorough examination with a CT scan or MRI. However, it’s uncertain how much fluid can be safely removed at once, but volumes up to 30 mL are often drained with pressure checked after each 10 mL is removed.
What else can Cryptococcal Meningitis be?
When doctors need to find out what’s going on in the brain, they might consider several causes. Those could range from infections to abnormal growth of cells (mass lesions). Here are some possibilities:
- Abscesses caused by bacteria, Nocardia, or fungi from the Aspergillus family
- Infections due to Mycobacterium tuberculosis or Histoplasma capsulatum, which are types of bacteria and fungus, respectively
- Acanthamoeba infection, which is due to a tiny organism known as an amoeba
- Neurosyphilis, which is a form of syphilis infection that affects the brain and nervous system
- Lymphomas, or cancers that start in cells that are part of the body’s immune system
- Lymphocytic meningitis, which is an inflammation of the protective membranes covering the brain and spinal cord
- Meningeal metastases, which refers to cancer that has spread to the membranes that surround the brain and spinal cord
- Hemorrhages, or bleeding in the brain
It’s important to understand that diagnosing these conditions requires a careful examination and the use of specific tests. It’s not something that’s easily done without the expertise of a health professional.
What to expect with Cryptococcal Meningitis
The initial prediction of how a condition unfolds depends on several factors that predict mortality. These include the amount of fluid pressure in the brain, a low count of white cells in this fluid, impairment of senses, a delayed diagnosis, increased levels of certain elements in the fluid, rate at which the infection clears, and abnormally high yeast content in the fluid – a common situation in Brazil.
There are also additional factors for patients who don’t have HIV, such as weak inflammatory reactions, not having a headache, underlying blood cancers, and chronic kidney or liver disease.
The number of deaths varies widely from country to country, largely depending on the healthcare resources available. It remains relatively high in the United States and France with a 10-week mortality rate ranging from 15% to 26%. And it’s even higher in non-HIV patients due to later diagnosis and compromised immune responses.
In countries with fewer resources, the death rate can rise from 30% to 70% in the same 10-week period. This increase is primarily due to late diagnoses of the disease and lack of access to suitable medication, pressure gauges (manometers), and optimal monitoring.
Possible Complications When Diagnosed with Cryptococcal Meningitis
There are several complications that could arise in certain medical situations. These include:
- Persistent Infection: This refers to cases where, despite four weeks of proven antifungal therapy at an adequate dose, the culture of cerebrospinal fluid (CSF) still tests positive for the infection.
- Relapsed Infection: This is based on two main factors:
- The relapse of the disease can be assessed by finding Cryptococci, a type of yeast, in a previously checked sterile part of the body.
- Returning signs and symptoms at the previous infection site suggest the presence of the disease.
- Elevated CSF Pressure: High pressure in the CSF that causes symptoms (sometimes because of initial antifungal therapy) should be addressed quickly through methods like lumbar taps (spinal punctures), temporary lumbar drainage catheter, or ventriculostomy in some patients.
- Immune Reconstitution Inflammatory Syndrome (IRIS): This includes two situations:
- Unmasking IRIS, where symptoms of a Cryptococcus infection appear after starting antiretroviral therapy.
- Paradoxical IRIS, when the response occurs during the treatment of cryptococcosis along with antiretroviral therapy administration.
- Cerebral cryptococcomas: These fungus balls in the brain can lead to serious short-term and long-term neurologic problems. They are difficult to treat and usually need long-term antifungal therapy.
- Hydrocephalus: This late complication often shows as dementia or chronic headaches.