Meningitis

Meningitis is a bacterial infection of the membranes covering the brain and spinal cord (meninges).

See also:

Aseptic meningitis

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:

Chemical irritation

Drug allergies

Fungi

Tumors

Types include:

Aseptic meningitis

Cryptococcal meningitis

Gram negative meningitis

H. influenza meningitis

Meningitis due to cancer (carcinomatous meningitis)

Meningococcal meningitis

Pneumococcal meningitis

Staphylococcal meningitis

Syphilitic aseptic meningitis

Tuberculous 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

Symptoms usually come on quickly, and may include:

Fever and chills

Mental status changes

Nausea and vomiting

Sensitivity to light (photophobia)

Severe headache

Stiff neck (meningismus)

Other symptoms that can occur with this disease:

Agitation

Bulging fontanelles

Decreased consciousness

Poor feeding or irritability in children

Rapid breathing

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

Fever

Mental status changes

Stiff neck

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:

Blood culture

Chest x-ray

CSF examination for cell count, glucose, and protein

CT scan of the head

Gram stain, other special stains, and culture of CSF

Treatment

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.

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 lasting complications.

Complications

Brain damage

Buildup of fluid between the skull and brain (subdural effusion)

Hearing loss

Hydrocephalus

Seizures

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.

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.

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.

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