Meningitis is a dangerous disease that can lead to severe consequences and even death. Unfortunately, it also has a lot of causes and many types that make it more likely to get one of these. You can get bacterial meningitis, viral meningitis, fungal meningitis, parasitic meningitis, amebic meningitis or even noninfectious meningitis.
This is the case because the word meningitis is very broad and does include a lot of subtypes. The word “Meningitis” is composed of the first part “meninges,” which refers to the surrounding layers around the brain tissue. The suffix “itis” refers to inflammation, and it is the presence of inflammatory cells for any particular reason. Because the word is very broad as you can see, this allows for many subtypes, which makes determining the diagnosis very challenging and increases the number of ways by which you can get meningitis.
As we mentioned meningitis occurs due to various causes, and identifying the type and cause of meningitis is the first step towards an effective treatment.
The types of meningitis are classified into different categories according to the causative agents:
1- Bacterial meningitis:
Bacterial meningitis is the term referring to bacterial inflammation of protective membranes covering the brain and spinal cord, the meninges, usually by bacterial invasion of the fluid surrounding the brain and spinal cord, causing a characteristic swelling of these membranes.
Despite being life-threatening, bacterial meningitis is not the most frequent type of meningitis, thanks to childhood vaccination in the past few decades. This refers to an incidence rate of 1.3 per 100,000 persons in the United States.
Causes:
According to the patients’ age group, bacterial meningitis occurs due to infection by a wide variety of bacterial species.
The most frequent causes are Streptococcus pneumonia, Group B Streptococcus, Neisseria meningitides, Haemophilus influenza, and Listeria monocytogenes.
How do you catch these infections?
During birth: Some of these agents can pass from a mother to her baby during natural delivery. Group B Streptococcus (GBS) is the leading cause since 25% of adult women carry these bacteria in the vagina or rectum; hence, they can pass the organisms during delivery. That’s why physicians usually test pregnant women for GBS during routine prenatal care.
Close contact with patients: Patients transmit the disease in their secretions (saliva) while coughing, sneezing, or kissing. This is typical with (Hib) and N. meningitidis infections. This mode of transmission is pervasive in meningitis outbreaks.
Eating contaminated food: Food might be contaminated with bacteria either from the food handlers, especially E. coli, or from the food itself. Unwashed fruits and vegetables might harbor E. coli, while L. monocytogenes are usually found in unpasteurized milk, smoked salmon, processed meat, including ham, cold cuts, hot dogs, sprouts, and soft cheeses made with raw milk.
After entering the body, these bacteria migrate to the fluid around the brain and spinal cord, the CSF, to reach the meninges.
What makes someone at a higher risk of getting bacterial meningitis?
› Age: Although people can develop bacterial meningitis at any age, young children are at higher risk due to immune immaturity. Thanks to the introduction of conjugate vaccines in the past few decades, the rates have dropped tremendously. While previously bacterial meningitis was a disease of children and adolescents, currently, most patients are elderly with an average age of 50, especially for Listeria monocytogenes meningitis.
› Living in groups: Bacterial meningitis can spread at ease in overcrowded or densely populated community settings. College campuses, dormitories, military bases, and retirement houses are the usual places. This is more frequent with meningococcal meningitis, caused by Neisseria meningitides.
› Certain medical conditions: Pulmonary diseases, malignancies, chronic sinusitis, chronic middle ear inflammation (otitis media), and immunity problems, for instance, HIV infections, diabetes mellitus, cancer, or the use of immunosuppressive drugs, are all risk factors for bacterial meningitis.
Patients who underwent splenectomy (surgical removal of the spleen) are at significant risk for S. pneumoniae and Haemophilus influenzae meningitis since the spleen is the only site in the human body where encapsulated bacteria; such as S. pneumoniae, can be cleared from the bloodstream.
Recent cranial neurosurgery may increase the risk of meningitis, known as (postoperative meningitis).
› Pregnancy: Pregnant females are at higher risk for Listeria monocytogenes infection, causing meningitis, miscarriage, stillbirth, and premature delivery.
› Travel: Traveling to crowded locations, for instance, Mecca during pilgrimage seasons, facilitates the spread of meningococcal meningitis between pilgrims. Therefore, vaccination is mandatory by law before the pilgrimage.
Sub-Saharan Africa is called the meningitis belt, and traveling there during the dry seasons increases the risk of meningococcal spread, too.
› Genetic factors: It’s believed that the risk of getting meningococcal and pneumococcal diseases, disease outcomes, and increased disease severity run in families. Specific genes that control the immune response to bacterial invasions have protective roles in ordinary people deficient in the absence of these genes.
› Certain factors in neonates and infants: Preterm labor, Down syndrome, and congenital heart diseases are linked to increased risk of bacterial meningitis.
› Vaccination: The US centers of disease control and prevention (CDC) recommend Meningococcal vaccines, Pneumococcal vaccines, and Hib vaccines for children and adults on schedule for maximal protection from bacterial meningitis.
Vaccination of pneumococcal meningitis patients also reduces the risk of second meningitis episodes.
Symptoms:
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- Headache: severe and not relieved by usual pain killers.
- Fever: sudden and high.
- Altered Consciousness, confusion, and lack of concentration.
- Neck Stiffness is a characteristic feature.
- Nausea and vomiting.
- Sensitivity to light.
- Skin rash may be present in meningococcal meningitis.
- Seizures occur in severe cases.
In newborns: Fever, vomiting, sleepiness, neck stiffness, and fontanelle bulging (soft spot on the baby’s head) are significant signs.
Prevention:
− General measures: avoiding smoking, getting enough rest, and avoiding close contact with patients.
− Pregnancy: Pregnant women should avoid certain foods during pregnancy e.g., unpasteurized milk, soft cheeses, raw sprouts, and some smoked and processed meat products to reduce the risk of Listeria monocytogenes infection.
− Vaccination: Vaccines are available against Meningococcal, Pneumococcal, and H. Influenza infection according to particular schedules.
− Prophylactic antibiotics: Doctors may recommend preventive antibiotic therapy to anyone who has recently contacted bacterial meningitis patients to avoid their infection.
2- Viral meningitis:
Viral meningitis (often referred to as aseptic meningitis) occurs when viral particles invade the fluid around the brain and spinal cord, the CSF, causing inflammation of the lining of the brain and spinal cord, usually following viral infections of the other body parts.
Despite being the most frequent type of meningitis, viral meningitis is less severe than other types, and patients usually get better on their own (without any treatment).
Causes:
Often no cause is identified; among adult patients with aseptic meningitis, only 50% get a confirmed diagnosis with the following common viruses:
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- Non-polio enteroviruses: Accounting for 46% of confirmed cases, it became the most common cause in the last few decades thanks to the mumps, measles, and rubella (MMR) vaccination policies. Enteroviruses infection occurs more often in the late spring or fall, and only a few patients develop viral meningitis.
- Herpesviruses, including Epstein-Barr virus, herpes simplex viruses, and varicella-zoster virus (which causes chickenpox and shingles), are the 2nd common cause.
- Influenza viruses: complicated cases of flu can develop into viral meningitis.
- Mumps and Measles viruses: in infants and children, especially if unvaccinated.
- Arboviruses: they spread by mosquitoes and insects.
- Lymphocytic Choriomeningitis Virus: it spreads by rodents and is a rare cause of viral meningitis.
How do you catch these infections?
Direct contact: Touching contaminated surfaces, objects, or hands of an infected person, then touching the eyes, nose, or mouth without handwashing can transmit non-polio enteroviruses.
Changing diapers of infected children is a common method of transmission of these viruses.
Close contact with patients: Herpesviruses usually spread by direct contact with infected individuals via kissing, sexual contact, or just touching the lesions.
Varicella-zoster virus, influenza viruses, mumps, and measles spread by breathing in tiny droplets of saliva released into the air when an infected person breathes, coughs, sneezes, or speaks. This can occur even if you are 3 meters away from the patient.
Drinking contaminated water: Non-polio enteroviruses can also spread via food and water contamination.
Mosquito bites: Arboviruses, including the West Nile virus, are transmitted via mosquito bites. This is quite common in the continental United States during summer and fall.
Rodents: Exposure to fresh urine, excrement, saliva, or nesting materials from infected rodents can transmit Lymphocytic Choriomeningitis Virus. The bite of an infected rodent is also reported to transmit the infection.
During pregnancy: Some of these viruses are transmitted from infected pregnant women to their babies during pregnancy. This is known as vertical transmission and includes non- polio enteroviruses, Mumps, West Nile virus (WNV), and Lymphocytic Choriomeningitis Virus. However, vertical transmission of these viruses is uncommon.
Most of these viral infections cause viral meningitis under certain conditions; otherwise, they cause other mild diseases.
What makes someone at a higher risk of getting viral meningitis?
› Age: Anybody can develop viral meningitis at any age, but infants and young children (under 5) are most susceptible to viral infections, especially enteroviruses.
› Immunity: People with weakened immunity, for instance, HIV-infected individuals and organ recipients taking immunosuppressive medications.
› Previous infections: Herpes simplex virus (HSV) exists as 2 types (HSV-1 and HSV-2), both closely related antigenically. This means when someone contracts either of the 2 types. They become relatively immune against the other kind. This phenomenon is called (cross-protection).
Since HSV-2 infection is more likely to cause viral meningitis than HSV-1, the declining rates of childhood infection with HSV-1 in the developed countries, the UK, for example, somehow increased the risk of getting HSV-2 infection in the adulthood (genital herpes) and, therefore, increased the risk of Herpes meningitis.
HSV-2 meningitis may also occur in the absence of genital herpes.
Symptoms:
Symptoms of viral meningitis are quite similar to those of bacterial meningitis but less severe. It even goes unreported in many cases.
Physical examination, lab investigations, and imaging are required to differentiate from bacterial meningitis.
Prevention:
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- General measures: Proper handwashing and avoiding close contact with patients.
- Vaccination: Vaccines are available against measles, mumps, chickenpox, and influenza with adequate protection (up to 97% with measles vaccine).
- Rat and insect control: to avoid Arboviruses and lymphocytic Choriomeningitis Virus infections.
3- Fungal meningitis:
Fungal meningitis occurs when fungi invade the body, usually the lungs, and pass to the brain and spinal cord, causing inflammation of their covering meninges.
Causes:
The most common form of fungal meningitis is caused by cryptococcus neoformans fungus. Other fungi causing this condition include Histoplasma, Blastomyces, and Coccidioides.
These fungi usually live in soil, on decaying wood, and in bird droppings. They are transmitted via breathing the fungal spores into the lungs and do not spread between humans.
A fungus living naturally on and inside our bodies, candida, can become harmful in certain patients with weakened immunity and cause fungal meningitis.
How do you catch these infections?
Inhalation: Infection occurs when people breathe in fungal spores from the surrounding environment. Fungal spores are present generally in the soil, bird or bat droppings, and on decaying wood.
Opportunistic infection: This term refers to infection by weak organisms, often non-harmful ones, when medications or certain diseases weaken your immunity. The fungus Candida usually lives on and inside our bodies and is known to cause opportunistic oral, genital, or even meningeal infections in HIV-infected individuals and patients on immunosuppressive drugs.
What makes someone at a higher risk of getting fungal meningitis?
› Immunity: people with weakened immunity are at higher risk. Examples include HIV-infected individuals, cancer patients, and people on immunosuppressive medications.
› Premature infants with low birth weight.
› Living in certain areas.
Symptoms:
Symptoms of Fungal meningitis are quite similar to those of bacterial meningitis.
Physical examination, lab investigations, and imaging are required to differentiate from bacterial meningitis.
Prevention:
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- General measures: Since the condition is rare and affects mostly people with weakened immunity, no measurements are required. However, avoiding areas with too many bird and bat droppings and dusty environments can be relatively protective for those people.
- Vaccination: No vaccines are needed.
4- Tuberculous meningitis (TB meningitis):
This typically describes inflammation of the meninges of the brain and spinal cord when a particular bacterium, Mycobacterium tuberculosis, invades the meninges, forming characteristic bacterial aggregations known as (granulomas), which rupture, triggering the patient’s immune response, in the form of severe inflammation, giving rise to TB meningitis.
Causes:
Tb meningitis occurs as a complication of pulmonary tuberculosis (TB). It may be the only clinical manifestation of tuberculosis or may occur in conjunction with disseminated disease (TB affecting most body organs at the same time and known as miliary TB).
How do you catch TB.?
Tuberculosis is a droplet infection, meaning it spreads by breathing in the Mycobacteria from tiny droplets of saliva released into the air when an infected person breathes, coughs, sneezes, or speaks.
TB. It can also spread by breathing in dust containing dried secretions of infected patients.
TB. less commonly spreads by drinking contaminated milk from infected cows.
After the invasion of the patient’s meninges, they form bacterial aggregations known as (granulomas) which trigger the patient’s immune response in severe inflammation.
Symptoms:
The condition starts with non-specific symptoms: fatigue, loss of appetite, vomiting, headache, and fever. It usually develops into acute meningitis with similar symptoms to bacterial meningitis.
It may be associated with dementia, personality changes, or paralysis of cranial nerves. In severe cases, the cerebellum and brain stem may be affected.
5- Parasitic meningitis (Eosinophilic meningitis):
A rare condition caused by the parasites: angiostrongylus cantonensis, baylisascaris procyonis (known as neural larva migrans), and gnathostoma spinigerum.
These parasites typically infect animals, but humans may contract the infection by eating infected animal tissues or contaminated food (usually raw fish and snails).
How do you catch these parasitic infections?
Eating raw food: Raw or undercooked freshwater fish, eels, frogs, poultry, snakes, snails, or slugs may be contaminated with these parasites.
Eating contaminated food: Food contaminated with raccoon feces may contain B. procyonis eggs.
6- Primary amebic meningoencephalitis (PAM):
PAM is a rare, highly fatal condition that occurs when the (Naegleria fowleri) organism enters the brain and the fluid around it.
People may contract this infection after swimming in contaminated water of lakes, rivers, hot springs, and minimally-chlorinated swimming pools.
The organism enters through the nose and passes to the brain tissues causing severe inflammation, which is almost always fatal.
7- Non- infectious meningitis:
It’s a term that refers to inflammation of the meninges due to causes rather than infectious agents. Non- infectious meningitis includes:
Drug-induced meningitis: some drugs might trigger meningitis in certain people, for instance, ibuprofen in some patients with lupus and immunoglobulin in a few chronic migraine patients. However, it’s still a very little chance.
Rheumatoid meningitis: a rare complication of the known autoimmune disease, rheumatoid arthritis.
Lupus meningitis: rarely affects patients with systemic lupus erythematosus (SLE), also an autoimmune condition.
Other causes, such as cancer and head injuries, can also cause non- infectious meningitis.
Meningitis Treatment Depending On The Actual Cause
Meningitis can be life-threatening, and treatment often starts in an emergency room to manage seizures and other critical symptoms. Treatment plans depend on the actual cause of meningitis:
1. Bacterial meningitis
› Stabilization
In acute cases, the patient’s airways are checked as the first thing to do in order to assess any breathing or circulatory troubles. If any of those problems exist, they need to be managed by an emergency specialist before starting the antibiotic treatment. Intravenous fluids (applied directly into the veins) are preferred during the first 48 hours, and some patients may also need oxygen masks and anti-seizure medications.
› Antibiotic treatment
Bacterial meningitis is usually dangerous, and treatment should start after hospitalization as soon as possible. The patient is kept in a dim-lightened and quiet room to avoid seizures and photo-sensitivity. In most cases, doctors begin antibiotic therapy with broad-spectrum antibiotics once the suspicion is made and the patient is admitted into the hospital.
Still, a more specific antibiotic treatment is the best choice, and it will be determined by a procedure called lumbar puncture or spinal tap. Lumbar puncture should be done before starting antibiotic therapy. In a lumbar puncture, a physician asks the patient to lie on one side, introduces a needle into the spine and draws some of the spinal fluid to check for bacteria or other organisms. Once the causal bacteria are identified and got tested for antibiotic sensitivity, the doctor will choose the best antibiotic accordingly. A typical round of antibiotics takes from 5 days to 3 weeks according to the etiology (causal bacteria) and is applied into the veins for rapid effects (intravenously). Patients who are improving after six days of therapy can receive the rest of the treatment at home with the appropriate care, medical follow up, and under a specialist’s permission.
› Steroids
Steroids are applied into the veins (intravenously), along with or before starting the antibiotic therapy, and should be discontinued after four days in some instances. Steroids prevent brain swelling and help to reduce the risk of complications, especially hearing loss and neurological sequelae.
› Fluids and pain killers
Fluids are essential to prevent dehydration, while pain killers are given to provide analgesia (pain relief) and lower the fever. Both are given into the veins for rapid effects (intravenously).
› Careful observation
It’s essential during the whole course of the disease. A physician regularly checks for any signs of brain affection, seizures or complications. Continuous assessment and evaluation of the blood glucose levels and the mental status via especial scales are required.
› Eliminating the source of infection
In many cases, the source of infection is located in the paranasal sinus or middle ear (otitis media), so an otolaryngologist examines the patient to determine the source and treat its causes. Treatment may involve surgery for drainage of the infected areas. This promotes faster recovery from the current condition and reduces the risk of recurrence.
› Measures for the close contacts
If the bacterial meningitis is caused by a particular bacterial species called meningococcal bacteria, it will be important to give prophylactic antibiotic therapy to anyone who has been in contact with the patient recently in order to avoid their infection.
› Complicated cases, e.g. meningococcal sepsis
Patients receive more intensive antibiotic therapy and are stabilized regarding their blood flow and breathing.
2. Viral meningitis
Despite being the most frequent type of meningitis, viral meningitis is usually self-limiting, which means the patient recovers spontaneously without specific treatment within a few days. Yet, patients should receive intravenous fluids and pain killers to minimize the pain and avoid dehydration.
Patients with specific immunity problems may need antibodies in a procedure called Immunoglobulin replacement.
Patients with suspected/confirmed viral encephalitis, on the other hand, are hospitalized and treated with antivirals, especially if Herpes (HSV- encephalitis) or influenza viruses are suspected/confirmed to be the cause. This reduces the risk of neurological complications, including permanent brain damage. Thus, viral meningitis must be differentiated from viral encephalitis to determine a suitable treatment plan.
Patients with (HSV-meningitis) should be referred to a sexual health clinic after recovery and treatment may include antivirals.
N.B. The physician might recommend antiviral therapy for some patients with HSV-meningitis.
3. Fungal meningitis
Treatment depends on the immunity status of the patient. Intravenous and oral anti-fungal medications are recommended for all patients. However, the dosage and duration of treatment may change according to each patient with a much longer duration for immunocompromised patients and people living with HIV. Treatment regimen usually takes up to 10 weeks based on the regular testing results and clinical recovery.
During treatment, special measures are performed to keep the patient hydrated and stable. Thus, it is essential to check for blood electrolyte balance and to avoid drug toxicity.
There is not a prophylactic treatment for close contacts of the patient because fungal meningitis does not spread between humans.
4. Tuberculous meningitis (TB meningitis)
It can be fatal, so hospitalization and treatment are necessary once TB meningitis is suspected.
The treatment primarily depends on specific antibiotic combinations called anti-tuberculous drugs. It takes 6 to 9 months for full recovery according to the patient’s response. The physician may also prescribe steroids in these cases.
5. Parasitic meningitis (Eosinophilic meningitis)
Treatment depends on both steroids and pain killers. Doctors also perform measures to lower the intracranial pressure; such as repeated spinal tab (repeated withdrawal of little spinal fluid).
6. Primary amebic meningoencephalitis (PAM)
Despite being almost always fatal, a particular combination of antibiotics, anti-fungal, anti-leishmanial agents and steroids is prescribed as a survival therapy for PAM patients.
7. Non-infective meningitis
Since it arises due to various causes, it’s treated according to its actual cause.