Meningitis means "inflammation of the meninges." The meninges (plural of meninx) are membranes that cover the brain and spinal cord. They can become inflamed when an infection occurs in the cerebrospinal fluid (CSF) surrounding these membranes. Other things such as medications, tumours, and chemical exposure can also cause meningitis.
The majority of people with meningitis that is not caused by bacteria (e.g., meningitis caused by a virus) recover quickly and completely. However, bacterial meningitis is fatal for 1 in 10 people who get it, even with treatment. Up to 1 in 5 people will be left with problems such as deafness or brain injury.
Quick diagnosis and treatment are vital to reduce the risk of death or complications from bacterial meningitis.
The most common causes of meningitis are bacteria or viruses, although there are many other causes. Rarer causes such as fungi can be seen, but often only in people with poor immune systems. Some of the more exotic causes of meningitis, such as parasites, usually are restricted to tropical countries.
Meningitis commonly occurs when bacteria or viruses make their way into the fluid surrounding the brain. Sometimes they enter directly as a result of an operation such as brain surgery. Sometimes they erode through the small bones in our skull, for instance in extreme cases of severe sinusitis. Sometimes they are carried there by our blood from an infection occurring elsewhere in our body such as pneumonia (a lung infection). But in most cases, we don't really understand how and why this happens.
Cryptococcus, a fungus, can also cause meningitis. It usually occurs in people with weakened immune systems, such as people with AIDS. But recently there has been a more aggressive strain found on Vancouver Island's eastern coast that can infect healthy people. Tuberculosis (TB) can cause meningitis, but in Canada it is usually seen in people who became infected with TB in their youth while growing up in other countries.
Certain medications and chemical irritants can cause in inflammation of the brain similar to meningitis. There have also been rare reports of vaccines causing meningitis. Viral or chemically-induced meningitis often goes away on its own.
Bacterial meningitis, on the other hand, is a very serious illness. The different types of bacteria that can cause it aren't normally dangerous – over half the population carries one or another of these bacteria in the back of the nose and throat. They're commonly transmitted by coughing, sneezing, and kissing, but they can't live outside the human body for very long. When they manage to enter the cerebrospinal fluid and begin multiplying, the bacteria cause inflammation and other symptoms of meningitis.
There are many species of bacteria that can cause meningitis. The most common causes of bacterial meningitis depend on the person's age and underlying medical conditions:
- newborns: group B streptococcus, E. coli (Eschericia coli), Listeria monocytogenes
- infants and children: Streptococcus pneumoniae, Neisseria meningitides, Haemophilus influenzae type b
- adolescents and young adults: Streptococcus pneumoniae, Neisseria meningitides
- older adults (usually over 65 years old): Streptococcus pneumoniae, Neisseira meningitides, Listeria monocytogenes
- people with alcohol use disorder, weakened immune systems: Listeria monocytogenes
Before 1992, the bacteria Haemophilus influenzae type b (Hib) was the most common cause of bacterial meningitis. Now that infants in Canada are immunized with the Hib vaccine, meningitis caused by Hib is very rare.
Children under the age of 2 are most susceptible to meningitis. Other things that increase the risk are:
- brain or spinal cord surgery
- head injury
- impaired or abnormal immune system
- kidney failure
- the use of corticosteroids (e.g., prednisone)
- pre-existing ear infection
- cancer, especially breast, lung, skin, leukemia, and lymphoma. When cancer is the cause of the meningitis it is called carcinomatous meningitis or leptomeningeal metastasis.
Symptoms and Complications
People with bacterial meningitis quickly become very sick, usually within hours, and shouldn't wait to get medical treatment. For people with non-bacterial meningitis (e.g., viral, chemical), the symptoms usually follow flu-like symptoms and include fever and headaches. Symptoms develop more slowly and are not as severe.
Symptoms of meningitis can include:
- high fever over 39°C (102°F)
- stiff and sore neck, especially when it's moved, turned, or bent (the discomfort is caused by inflammation of the meninges) – this may not be obvious in people whose immune systems are not functioning properly, such as:
- people taking corticosteroids
- people with AIDS
- people taking cancer or transplant medications
- children less than 24 months of age and especially those less than 6 months of age.
- severe headache due to extra pressure in the head – look for signs of fussiness and irritability in children too young to complain of a headache
If blood vessels in the brain become inflamed, the brain won't get enough oxygen. This can make a person drowsy and less responsive, and, in extreme situations, they can fall into a coma. Lack of oxygen to the brain can also cause seizures.
Inflammation results in increased pressure on the brain, which sometimes causes vomiting. You might also notice a rash that resembles clusters of tiny red or purple pinpricks. When you press on the spots, they won't turn white, as skin normally does. The skin itself can develop cyanosis, a bluish tinge caused by a lack of oxygen. Not all symptoms of meningitis appear at once, however, and they may be less obvious for seniors.
Symptoms for very young children can include:
- fever, with cold hands and feet
- not eating
- difficulty waking up
- high-pitched moaning or crying
- arching their backs and pulling at their necks
- not settling down or taking comfort when held
- having a vacant expression
- showing a pale, mottled complexion
- rash (red or purple pinpricks)
Long-term complications can occur and last long after the infection has been treated. These include deafness, mental impairment, paralysis, and sometimes seizures that require lifelong treatment.
Making the Diagnosis
Your doctor will ask you questions about your symptoms and perform a physical exam. Your doctor will want to confirm the diagnosis by analyzing a sample of cerebrospinal fluid.
Fluid is drawn through a needle from the lower part of the spinal cord in a procedure called a lumbar puncture (spinal tap). The fluid is then checked for the presence and type of bacteria. Knowing which species of bacteria is responsible for the meningitis allows your doctor to tailor the treatment for best results.
Your doctor may also order other tests such as blood tests and computed tomography (CT) or magnetic resonance imaging (MRI) scans.
Treatment and Prevention
The infection that causes bacterial meningitis is treated with a combination of antibiotics. The antibiotics you receive will depend on the bacteria that are suspected, your age, and other factors. The antibiotics are injected into a vein. You might have to receive the antibiotics for as long as 3 weeks.
For the first few days of antibiotic treatment, you may also be given dexamethasone* (a corticosteroid) to help reduce the risk of meningitis complications. People with meningitis, regardless of the cause, may need supportive treatment such as intravenous fluids and fever-reducing medications.
Children are routinely immunized with the Hemophilus influenzae type b (Hib) vaccine. This is an important preventive measure, since the Hib bacteria used to be the most common cause of meningitis in children. For infants, the Hib vaccine is recommended at 2, 4, 6, and 18 months.
Other recommended vaccines such as those against meningococcal group C bacteria and pneumococcal bacteria promise to greatly reduce the risk for meningitis caused by these organisms. Health Canada recommends that children be immunized with the meningococcal vaccine routinely at 12 months, although some provinces may start immunization earlier. . Another dose is given around 12 years of age. Pneumococcal conjugate vaccine is also being recommended for infants at 2, 4, and 12 months, or at 2, 4, 6, and 12 to 15 months of age.
For adults over 65, a different pneumococcal vaccine is available to reduce the risk of getting meningitis from the pneumococcal bacteria. It's also recommended for people without a spleen or those whose immune systems are not working properly.
If you've been in close contact with someone who has meningitis caused by a Meningococcus or H. influenzae infection, your doctor likely will prescribe antibiotics for you as a precautionary measure.
Carcinomatous meningitis is usually treated with chemotherapy which is administered in the cerebrospinal fluid (CSF) by lumbar puncture or via an Ommaya reservoir.