Meningitis is an infection which causes inflammation of the membranes covering the brain and spinal cord. Non-bacterial meningitis is often referred to as "aseptic meningitis." Bacterial meningitis may be referred to as "purulent meningitis."

Causes, incidence, and risk factors

The most common causes of meningitis are viral infections that usually resolve without treatment. However, bacterial infections of the meninges are extremely serious illnesses, and may result in death or brain damage even if treated. Meningitis is also caused by fungi, chemical irritation or drug allergies, and tumors. Types include:

meningitis - cryptococcal

syphilitic aseptic meningitis

meningitis - H. influenza

meningitis - meningococcal

meningitis - pneumococcal

meningitis - staphylococcal

meningitis - tuberculous

aseptic meningitis

meningitis gram negative

carcinomatous meningitis (meningitis due to cancer)

Acute bacterial meningitis is a true medical emergency, and requires immediate hospital-based treatment. Bacterial strains that cause meningitis include Streptococcus pneumoniae , Haemophilus influenzae , Neisseria meningitidis (meningococcus), Listeria monocytogenes , and many other types of bacteria. In the U.S. about 17,500 cases of bacterial meningitis occur each year. Viral meningitis is milder and occurs more often than bacterial meningitis. It usually develops in the late summer and early fall, often affects children and adults under 30. Seventy percent of the infections occur in children under the age of 5. Most viral meningitis is associated with enteroviruses, which are viruses that commonly cause stomach flu. However, many other types of viruses can also cause meningitis; for example, viral meningitis may occur as a complication in people with genital herpes.

Signs and tests

Lumbar puncture

with

CSF glucose measurement and CSF cell count.

Gram-stain and culture of CSF (cerebral spinal fluid)

.

Chest X-ray

to look for other sites of infection.

Head CT scan

looking for hydrocephalus,

abscess or deep swelling.

Treatment

Antibiotics will be prescribed for bacterial meningitis; the type will vary depending on the infecting organism. Antibiotics are ineffective in viral meningitis. Treatment of secondary symptoms including brain swelling , shock , and convulsions will require other medications and intravenous fluids. Hospitalization may be required depending on the severity of the illness and the needed treatment.

Expectations (prognosis)

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 residual complications.

Complications

hearing loss

/

deafness

brain damage

loss of vision

hydrocephalus

Calling your health care provider

If you feel that you or your child have symptoms suggestive of meningitis, you must seek emergency medical help immediately. Early treatment is key to a good outcome.

Prevention

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

It is highly recommended that household contacts and individuals with close contact with individuals with

meningococcal meningitis receive preventative antibiotics to avoid becoming infected themselves.

Some communities conduct vaccination campaigns following an outbreak of meningococcal meningitis. Military recruits are routinely vaccinated against this form of meningitis because of its high rate of occurrence.

The American Academy of Pediatrics and the American College Health Association encourage college students (particularly freshmen living in dormitories) to consider being vaccinated with the meningococcal vaccine.