Meningitis is a bacterial infection of the membranes covering the brain and spinal cord (meninges).
Meningitis - Gram-negative
Meningitis - H. influenzae
Meningitis - meningococcal
Meningitis - pneumococcal
Meningitis - staphylococcal
Meningitis - tuberculous
Causes, incidence, and risk factors
The most common causes of meningitis are viral infections that usually get better without treatment. However, bacterial meningitis infections are extremely serious, and may result in death or brain damage, even if treated.
Meningitis may also be caused by:
Gram negative meningitis
H. influenza meningitis
Meningitis due to cancer (carcinomatous meningitis)
Syphilitic aseptic meningitis
Acute bacterial meningitis is a medical emergency, and requires immediate treatment in a hospital.
Viral meningitis is milder and occurs more often than bacterial meningitis. It usually develops in the late summer and early fall, and often affects children and adults under age 30. Most infections occur in children under age 5. Most viral meningitis is due to enteroviruses, which are viruses that also can cause intestinal illness.
Many other types of viruses can cause meningitis. For example, viral meningitis can be caused by herpes viruses, the same virus that can cause cold sores and genital herpes (although people with cold sores or genital herpes are not at a greater risk of developing herpes meningitis).
Recently, West Nile virus, spread by mosquito bites, has become a cause of viral meningitis in most of the United States.
Symptoms usually come on quickly, and may include:
Fever and chills
Mental status changes
Nausea and vomiting
Sensitivity to light (photophobia)
Stiff neck (meningismus)
Other symptoms that can occur with this disease:
Poor feeding or irritability in children
Unusual posture, with the head and neck arched backwards (opisthotonos)
Meningitis is an important cause of fever in children and newborns.
People cannot tell if they have bacterial or viral meningitis by how they feel, so they should seek prompt medical attention.
Signs and tests
Physical examination will usually show:
Fast heart rate
Mental status changes
For any patient who is suspected of having meningitis, it is important to perform a lumbar puncture ("spinal tap"), in which spinal fluid (known as cerebrospinal fluid, or CSF) is collected for testing.
Tests that may be done include:
CSF examination for cell count, glucose, and protein
CT scan of the head
Gram stain, other special stains, and culture of CSF
Doctors prescribe antibiotics for bacterial meningitis. The type will vary depending on the bacteria causing the infection. Antibiotics are not effective in viral meningitis.
Other medications and intravenous fluids will be used to treat symptoms such as brain swelling, shock, and seizures. Some people may need to stay in the hospital, depending on the severity of the illness and the treatment needed.
Early diagnosis and treatment of bacterial meningitis is essential to prevent permanent neurological damage. Viral meningitis is usually not serious, and symptoms should disappear within 2 weeks with no lasting complications.
Buildup of fluid between the skull and brain (subdural effusion)
Calling your health care provider
If you think that you or your child has symptoms of meningitis, get emergency medical help immediately. Early treatment is key to a good outcome.
Haemophilus vaccine (HiB vaccine) in children will help prevent one type of meningitis.
The pneumococcal conjugate vaccine is now a routine childhood immunization and is very effective at preventing pneumococcal meningitis.
Household members and others in close contact with people who have meningococcal meningitis should receive preventive antibiotics to avoid becoming infected themselves.
The meningococcal vaccination is recommended for:
Adolescents ages 11 - 12 and adolescents entering high school (about age 15) who have not already received the vaccination.
All college freshmen who have not been vaccinated and are living in dorms.
Children age 2 and older who do not have their spleen or who have other problems with their immune system.
Those traveling to countries where diseases caused by meningococcus are very common (ask your doctor).
Some communities conduct vaccination campaigns after an outbreak of meningococcal meningitis.