Also called: Aseptic Meningitis, Bacterial Meningitis, Meningococcal Disease, Viral Aseptic Meningitis, Viral Meningitis
Meningitis is inflammation of the meninges (the membranes that protect the brain and spinal cord) due to infection by viruses, bacteria or fungi.
Viral (aseptic) meningitis is the most common type of the disease. However, symptoms of viral meningitis tend to be very mild with many cases going unnoticed or undiagnosed. Therefore, the exact number of viral meningitis cases that occur each year is unknown. Bacterial meningitis is far less common than viral meningitis, although it tends to be much more dangerous and can be fatal if not treated promptly.
A variety of signs and symptoms (e.g., fever, headache) may indicate a mild meningitis infection, with most subsiding after a few days. Symptoms of a more serious meningitis infection (e.g., seizures, vomiting) require immediate medical attention. In most cases, meningitis can be diagnosed from a complete medical history, physical examination and certain medical tests (e.g., spinal tap, imaging tests).
Treatment of meningitis is dependent on its type or cause. Some common treatments for viral meningitis include rest, over-the-counter medications and fluid consumption. Bacterial meningitis is typically treated with antibiotics. The combinations prescribed depend on the infection source, severity and age of the patient, among other variables. Vaccinations are available to prevent some forms of bacterial meningitis. Avoiding viruses that cause viral meningitis may also reduce the risk of infection.
Meningitis occurs when inflammation from some type of infection affects the meninges, the tissue covering the brain and spinal cord. These infections may be bacterial, viral or fungal in origin. Rarely, meningitis may also occur in reaction to some medications or diseases (e.g., cancer). Anyone can develop meningitis, although it tends to occur most frequently in older adults, young children and individuals with a long-standing health condition (e.g., HIV/AIDS). However, cases of bacterial meningitis among adolescents and young adults may be becoming more common in the United States and United Kingdom.
The central nervous system includes the brain and spinal cord. Its neural tissues are protected by three membranous layers of connective tissue called meninges. The meninges also enable the vertebral column and spinal cord to flex and twist.
The outermost layer of the meninges is called the dura mater. It fuses with the lining of the skull. The middle layer of the meninges is called the arachnoid mater. This membrane is separated from the delicate, innermost membrane (pia mater) by a space that contains cerebrospinal fluid (CSF). This fluid carries nutrients, helps absorb impact and helps defend the brain from harmful microorganisms.
Bacteria, viruses or fungi reach the meninges through the bloodstream, from nearby infections (e.g., sinusitis) or by direct contact (e.g., penetrating injury, surgical procedure). While in the bloodstream, these microorganisms resist attack by white blood cells, causing receptors in the brain to allow penetration into the CSF. Once in the CSF, infection tends to progress rapidly due to the lack of disease-fighting substances (antibodies). The resulting inflammation causes oozing fluid called exudate to damage cranial nerves and pathways that carry signals to other parts of the body. It also causes swelling of the meninges, which disrupts the normal flow of blood and oxygen to the brain.
Types and differences of meningitis
Meningitis can be classified into three types:
- Viral (aseptic) meningitis. The most common form of meningitis, it tends to be relatively mild. Each year, between 25,000 and 50,000 cases of viral meningitis require hospitalization, according to the U.S. Centers for Disease Control and Prevention (CDC). Most patients with viral meningitis have symptoms that go away without any special treatment. However, symptoms of viral meningitis may closely resemble those associated with bacterial meningitis, a much more serious form of the disease that requires immediate treatment. This similarity may complicate the process of diagnosing the source and severity of the infection. Viral meningitis may be caused by enteroviruses (viruses that infect the intestinal tract) or other viral conditions (e.g., herpes simplex virus, human immunodeficiency virus).
- Bacterial meningitis. Usually the most severe type of meningitis. Many different types of bacteria can cause bacterial meningitis if they travel through the bloodstream and enter the brain. The most common forms of bacterial meningitis include the bacteria that cause pneumonia (pneumococcus) and meningococcus bacteria (Neissaria meningitides).
According to the CDC, about 6,000 people develop pneumococcal meningitis and 2,600 people develop meningococcal meningitis in the United States each year. Vaccines are available that can prevent some types of bacterial meningitis from spreading to other people. The disease can also occur if bacteria invade the meninges directly (e.g., ear or sinus infections, skull fractures). Left untreated, bacterial meningitis may cause brain damage, deafness, cognitive impairment and even death.
- Chronic meningitis. Inflammation of the meninges that is ongoing or recurrent. Patients with chronic meningitis may experience spontaneous episodes of severe headache and fever, often interrupted by extended periods without painful symptoms. Most cases of chronic meningitis have no known underlying cause, though it occurs relatively frequently in people with compromised immune systems (e.g., due to HIV/AIDS, cancer, chemotherapy use, long-term use of the corticosteroid prednisone). It also sometimes occurs in people with healthy immune systems who contract tuberculosis (TB), Lyme disease or other infections. Bacterial meningitis that has been only partially treated (but not eliminated from the body) may lead to chronic meningitis. Drugs such chemotherapy medications, organ-transplantation medications and nonsteroidal anti-inflammatory drugs have also been associated with chronic meningitis.
In addition, certain fungi (e.g., cryptococcus) may cause meningitis. This is rare, however, and usually occurs in patients whose immune systems are severely weakened from disease (e.g., HIV/AIDS, cancer).
Risk factors and causes of meningitis
Meningitis is a rare but deadly disease. It is usually caused by a viral infection, although it may also be caused by bacterial or fungal infections.
Certain populations have an increased risk of developing meningitis, including:
- Older adults
- Children under age 5
- Young adults
- People who live in community settings (e.g., college dormitory)
- Pregnant women
- People with compromised immune systems
- Travelers to areas with meningitis outbreaks. These include parts of sub-Saharan Africa and parts of the Middle East during religious pilgrimages.
Viral (aseptic) meningitis is the most common form of the disease. However, symptoms of viral meningitis tend to be very mild with many cases going unnoticed or undiagnosed.
The viral form of the disease may be spread in several ways (e.g., poor hygiene, polluted water or sewage). However, contact with a person who has viral meningitis may not necessarily lead to the development of meningitis. Although the initial virus (e.g., chickenpox) may be infectious, it will not necessarily result in viral meningitis. An enterovirus or chickenpox virus may reach the bloodstream and cause viral meningitis in one patient. Another person may contract that original enterovirus or chickenpox virus, but it may not develop into meningitis in the second person.
Many viruses may cause viral meningitis. The most common include:
- Enteroviruses. The most common cause of viral meningitis, they are responsible for about 90 percent of all cases, according to the U.S. Centers for Disease Control and Prevention. Enteroviruses (e.g., coxsackievirus, echovirus) live in human intestines and are usually spread through biological matter (e.g., saliva, feces, mucus). However, most produce only mild symptoms (e.g., sore throat, cold) with only a very small percentage of infections resulting in the development of meningitis. Exposure to enteroviruses tends to occur in the summer and fall months. People usually develop symptoms between three and seven days after they are infected and may be contagious beginning three days after being infected and until 10 days after symptoms occur.
- Herpes simplex virus (HSV). Both HSV-1 (virus that causes cold sores) and HSV-2 (virus that causes genital herpes) can cause meningitis in rare instances. HSV-2 is the leading cause of recurrent (Mollaret’s) meningitis infection.
- Human immunodeficiency virus (HIV). Patients with HIV may occasionally develop meningitis or meningoencephalitis (meningitis accompanied by encephalitis). This can be due to a suppressed immune system or direct HIV infection of the central nervous system. Most patients with this form of viral meningitis experience mild symptoms (e.g., headache, rash).
- Mumps and measles. May cause meningitis as well as encephalitis. Cases of meningitis resulting from mumps or measles are extremely rare because of the success of routine child vaccinations for these diseases.
Other common viruses may occasionally cause viral meningitis (e.g., arboviruses that cause Lyme disease, chickenpox, mononucleosis).
Bacterial meningitis is far less common than viral meningitis, although it can occur very quickly and tends to be much more dangerous. It can spread from person to person and needs contact isolation. It is most common in children between the ages of 1 month and 2 years and is much less common in adults. However, outbreaks of bacterial meningitis sometimes occur in groups of people who live in close quarters, such as those in college dormitories or military barracks.
Some of the more common causes of bacterial meningitis include:
- Streptococcus pneumoniae (pneumococcal). The bacteria that causes pneumonia, as well as ear and sinus infections. This is the most common cause of bacterial meningitis in adults. Although it occurs rarely, pneumococcal meningitis has a fatality rate of approximately 20 percent, according to the National Institutes of Health. Furthermore, about half of all who recover have serious long-term complications as well (e.g., deafness).
- Neisseria meningitidis (meningococcal). A relatively frequent cause of meningitis, it has increased by nearly 60 percent among adolescents and young adults since the early 1990s, according to the National Meningitis Association (NMA). Each year, about 2,500 Americans contract this form of meningitis, and 10 to 15 percent die from it, according to the NMA. In addition, about 20 percent of survivors have long-term disabilities such as brain damage, hearing loss or limb amputations. However, many people who carry the N.meningitidis bacteria never develop signs or symptoms of meningitis. These bacteria live naturally in the back of the nose, throat and upper respiratory areas of the human body. They pass between people through personal contact (e.g., touching, kissing) and by coughing or sneezing. Meningococcal bacteria cannot live outside of the body, making contagious outbreaks rare. Septicemia (blood poisoning) occasionally occurs in conjunction with meningitis when meningococcal bacteria enter the bloodstream.
- Haemophilus influenzae b (Hib). Formerly the most common cause of meningitis. The recent development of a Hib vaccine has reduced instances of haemophilus meningitis substantially, with very few cases reported annually.
- Listeria monocytogenes (listeriosis). Meningitis may occur as a result of listeriosis (infection caused by eating contaminated food). This type of meningitis is most frequent in pregnant women, their fetuses, newborns and adults with weakened immune systems. People who work with animals, who are diagnosed with kidney failure or who take corticosteroids (which suppress the immune system) are at increased risk for this form of meningitis.
- Escherichia coli. Bacteria that live in the colon or large intestine of healthy people. E. coli meningitis usually affects people with suppressed immune systems (e.g., cancer patients, AIDS patients). Because these bacteria may be present in the birth canal of pregnant women, some newborns (e.g., premature babies, low birth weight babies) may have a higher risk of becoming infected during delivery.
- Bacillus tubercle (tuberculosis). A rare form of meningitis may occasionally occur when the bacterium that causes tuberculosis spreads from the lungs, attacking the meninges (membranes that cover the brain and spinal cord).
- Cochlear implants. Special hearing devices placed surgically in people with hearing loss. Rarely, bacterial meningitis may occur in people who receive cochlear implants. This may stem from a number of factors (e.g., inner ear abnormalities, surgical complications, history of ear infections).
In addition, some fungi (e.g., cryptococcus, histoplasma) may occasionally cause meningitis. However, this is rare and usually occurs in patients whose immune systems are severely weakened from disease (e.g., HIV, AIDS, cancer) or in young children. In extremely rare cases, an amoeba sometimes found in fresh or standing water can cause a very rare but serious form of amebic meningitis infection.
Signs and symptoms of meningitis
Symptoms of meningitis vary depending on the nature of the infection. In the case of viral meningitis, symptoms may be very mild and resemble those of a cold, sometimes accompanied by low-grade fever and a rash. In some cases, no symptoms appear at all.
However, all cases of meningitis require emergency medical attention because some forms of meningitis are potentially serious and even fatal. Any symptoms that appear should be treated seriously.
Symptoms of meningitis infection may appear in as little as 24 hours, and in severe cases they may rapidly progress. Such symptoms may include:
- Confusion or disorientation
- Stiff or painful neck (resulting in difficulty or inability to touch chin to chest)
- Muscle aches or weakness
- Sensitivity to light
- Skin rash
Infants with meningitis typically exhibit some different symptoms than adults. These are often difficult to identify. Parents may find it difficult to awaken their baby, or the baby may refuse to eat. In latter stages, the child may experience spasms in which the body is extremely hyperextended (opisthotonos). Other symptoms may include:
- Jaundice (yellowing of the skin, whites of the eyes and mucous membranes)
- Neck rigidity
- High pitched cry
- Bulging of the soft spot (fontanelle) on top of the skull
People with severe forms of meningitis may quickly develop complications that include stroke symptoms, low blood pressure, paralysis, blindness, hearing loss, loss of speech and brain damage. Stupor and coma also can occur, and death can quickly follow. The longer a person waits to be treated following infection, the more severe symptoms are likely to be.
Diagnosis methods for meningitis
To diagnose meningitis, a physician will review a medical history and perform a physical examination. One method of diagnosing meningitis is to bend the neck of a patient forward while the person lies flat on his or her back. A person with meningitis will involuntarily flex the knees in response. This is believed to be a reaction to irritation of the inflamed meninges.
Certain medical tests may also be performed that can help determine the nature of the meningitis (e.g., viral or bacterial). If the meningitis is bacterial, these tests can help identify the specific type of bacterium responsible, which can help the physician to devise a more effective treatment plan. It may take a few days before the results of these tests are available.
These tests include:
- Spinal tap. The insertion of a long needle into the spinal canal to collect cerebrospinal fluid (CSF) for laboratory testing. Analysis of CSF is the only definitive diagnosis method of meningitis. CSF is checked for indicators of an infection (e.g., the number of white blood cells, glucose and protein levels) and then interpreted by a physician to determine if meningitis is present. CSF may also help identify if the source of infection is bacterial or viral. A spinal tap is nearly always performed if meningitis infection is suspected.
- Throat culture. The back of the throat is swabbed and examined under a microscope. A throat culture can determine if the presence of microorganisms that can cause meningitis or a disease with similar symptoms (e.g., encephalitis) are present. In addition, it may also be helpful in determining the appropriate course of treatment.
- Imaging tests. Tests that produce images of internal body organs, tissues, structures and pathways (e.g., x-ray, CAT scan, MRI). Imaging tests of certain parts of the body (e.g., chest, skull) may show swelling or inflammation consistent with meningitis and the severity of the infection.
- Urine tests. Urine may be tested to check for the cause of painful symptoms associated with meningitis.
- Blood tests. Blood may be analyzed to check counts of white and red blood cells and biochemistry (hormone levels). Cultures of blood can be developed that can be examined for the presence of bacteria or viruses.
- Polymerase chain reaction (PCR). A DNA test that checks blood for the presence of viruses or parasites. A PCR may be performed if a patient is suspected of having meningitis.
- Biopsy. Rarely, a sample of tissue from a rash thought to be caused by meningitis may be removed for laboratory analysis.
Treatment options for meningitis
Treatment of meningitis depends on its type or cause. For example, viral meningitis may sometimes resolve on its own within seven to 10 days, whereas viral meningitis caused by herpes simplex virus may require antiviral medication. Over-the-counter medicine (e.g., analgesics such as aspirin and ibuprofen) is also often used to treat viral meningitis. However, patients should always consult their physician before taking any type of medication, including over-the-counter remedies. In addition, children and teens should not be given aspirin due to the risk of the quick-acting and life-threatening Reye syndrome. Other common treatments include rest and fluid consumption.
Although bacterial meningitis is less common than viral meningitis, it is potentially much more dangerous. It requires prompt treatment under a physician’s supervision. Antibiotics will be prescribed to treat bacterial meningitis. The combination of medications prescribed depends on a number of factors, including:
- Source of infection (e.g., type of bacteria)
- Age of the patient
- Severity of infection
- Presence of other medical conditions or complications
Tests to determine the type of meningitis present may take a few days. A physician will often begin administering intravenous antibiotics before the cause has been determined due to the possibility of severe complications from the disease (e.g., death). Appropriate treatment with antibiotics can reduce the fatality rate associated with the most common types of bacterial meningitis to less than 15 percent in most patients, according to the U.S. Centers for Disease Control and Prevention (CDC). Treatment may be altered or stopped later if testing indicates a viral infection as the source of meningitis.
A physician may also prescribe treatments to deal with symptoms of the disease (e.g., brain swelling, convulsions and dehydration). Fluid that has accumulated in and around the brain may be drained or otherwise removed. Analgesics or nonsteroidal anti-inflammatory drugs may be administered to reduce pain and/or inflammation. Steroids are also used in certain cases of bacterial meningitis.
Some forms of bacterial meningitis are contagious, especially in group settings such as college dormitories or daycare centers. If a case occurs, health authorities may notify other people who may have been in contact with the patient. Bacterial meningitis caused by Neisseria meningitidis is a nationally notifiable disease and all cases must be reported to the CDC.
Prevention methods for meningitis
Although meningitis itself is not communicable, microorganisms (e.g., viruses, bacteria, fungi) that cause infections that may lead to meningitis may be spread through:
- Personal contact (e.g., touching, kissing)
- Coughs or sneezes
- Sharing certain personal items (e.g., toothbrush, eating utensils)
Living with someone who has meningitis may also increase the risk of infections that can lead to meningitis. In many cases, people in close contact with bacterial meningitis patients are given antibiotics to help prevent transmission of the condition.
Vaccinations are available to prevent some forms of bacterial meningitis, including:
- Meningococcal conjugate vaccine (MCV4). Expected to give better, longer-lasting protection than previous meningitis vaccines. Licensed in 2005, MCV4 is also predicted to prevent person-to-person spread of meningitis. The U.S. Centers for Disease Control and Prevention (CDC) recommends this vaccine for children at their routine adolescent visit (11 or 12 years of age) and other people at increased risk for the disease, including:
- Adolescents at high school entry
- College freshman living in dormitories
- Microbiologists routinely exposed to meningococcal bacteria
- U.S. military recruits
- People living in or traveling to areas with high rates of infection (e.g., Africa)
- Anyone with a damaged or removed spleen
- People with compromised immune systems
- Individuals who may have been exposed to meningitis during an outbreak
- Adolescents at high school entry
Up to 80 percent of meningococcal meningitis cases can be prevented with vaccination, according to the National Meningitis Association.
- Haemophilus influenzae type b vaccine (Hib). Routinely given to children in the United States. Formerly a leading cause of meningitis, Hib is no longer a leading cause of the disease. The vaccine may also be used on adults with certain diseases (e.g., AIDS, sickle cell anemia).
- Pneumococcal conjugate vaccine (PCV7). Also part of regular immunizations for young children. It may also be used for older children at risk for pneumococcal disease or who have other serious conditions (e.g., chronic lung disease, cancer). PCV7 should be avoided by children who have had a previous allergic reaction to the vaccine.
- Pneumococcal polysaccharide vaccine (PPV). This vaccine is recommended by the CDC for adults over age 65 and children with compromised immune systems or certain chronic conditions (e.g., heart disease).
- Measles, mumps and rubella vaccine (MMR). In most cases, people over the age of 18 who were born after 1956 should receive the MMR vaccine at least once. Children usually receive two doses of the vaccine; the first at 12 to 15 months of age and the second between the ages of 4 and 6. The vaccine has reduced the number of cases of meningitis formerly caused by measles, mumps or rubella.
Avoiding viruses that cause meningitis reduces the risk of contracting the viral form of the disease (e.g., herpes simplex virus, arboviruses). Cooking meat thoroughly will substantially reduce the risk of listeriosis, which may cause meningitis in some cases.
Washing hands regularly and properly kills germs and reduces the risk of viral meningitis. For example, parents are urged to wash their hands carefully after changing the diaper of an infected infant.
Use of insect repellant when outdoors may help prevent exposure to infected mosquitos and ticks.
Whenever a case of meningitis is diagnosed, it should be reported to local or state departments of health to help control the spread of the virus or bacteria responsible for the outbreak.
Questions for your doctor regarding meningitis
Preparing questions in advance can help patients have more meaningful discussions regarding their conditions. Patients may wish to ask their doctor the following questions related to meningitis:
- How serious is my case of meningitis?
- Is my child’s meningitis bacterial or viral?
- How long will it take to recover?
- How likely am I to have long term disabilities as a result of my infection?
- Are there vaccines I can take to prevent a future recurrence?
- What antibiotics will you prescribe, if any?
- How common is this form of meningitis?
- Is it possible I could have infected others?
- How do I know if my meningitis is gone?
- Will over-the-counter medicines help me?