Health Encyclopedia

Meningitis

Definition

Meningitis is swelling and irritation (inflammation) of the membranes covering the brain and spinal cord. This inflammation causes changes in the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord.

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 is also 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 true 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 the age of 5. Most viral meningitis is due to enteroviruses, which are viruses that also 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

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
Opisthotonos
Poor feeding or irritability in children
Rapid breathing

Meningitis is an important cause of fever in newborn children.

Signs and tests

Blood culture
Chest x-ray
Head CT scan
Gram-stain and culture of CSF (cerebral spinal fluid)
Lumbar puncture ("spinal tap") with CSF glucose measurement and CSF cell count

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
Hearing loss or deafness
Hydrocephalus
Loss of vision

Calling your health care provider

If you feel 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.

References

Swartz MN. Meningitis: bacterial, viral, and other. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 437.

Review Date:9/28/2008
Reviewed By:David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, PhD, MD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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