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

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.

Images

Lumbar puncture - spinal tap

Meninges of the spine

Haemophilus influenza organism

Brudzinski's sign of meningitis

Meninges of the brain

Kernig's sign of meningitis

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Meningitis Symptoms

Review Date: 09/15/2010
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, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)