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 are Meningococcus (Neisseria meningitis), Pneumococcus (Streptococcus pneumoniae), group B Streptococcus (Streptococcus agalactiae) and E. coli (Eschericia coli). 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:
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:
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:
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.