meningitis (redirected from Viral meningitis)

meningitis (mĕnĭnjī`tĭs) or cerebrospinal meningitis (sĕr'əbrōspī`nəl), acute inflammation of the meninges, the membranes that cover and protect the brain and spinal cord. It can be caused by bacteria, viruses, fungi, or other organisms, usually introduced via the bloodstream from infections elsewhere in the body.

Viral meningitis

Viral meningitis, sometimes referred to as nonbacterial or aseptic meningitis, is milder and more common than bacterial forms. It can be caused by any of a number of viruses, including enteroviruses, the mumps virus, herpesviruses, HIV, and several mosquito-borne viruses (Bunyavirus and flavivirus) usually associated with encephalitis. Viral meningitis is usually seen only in individual cases rather than in outbreaks. Those not vector-borne are usually spread from person to person by the fecal-oral route. Symptoms include headache, fever, stiff neck, and tiredness, sometimes accompanied by a rash. There is no specific treatment.

Bacterial meningitis

A variety of organisms can cause bacterial meningitis, a serious form that can be fatal, especially in children. Symptoms include high fever, headache, chills, vomiting, stiff neck or back, and confusion, sometimes accompanied by a purplish rash. Serious cases can quickly lead to delirium, coma, or convulsions. It is spread by oral or nasal secretions.

The leading cause of bacterial meningitis is the ill-named bacterium Haemophilus influenzae b (Hib), originally thought to be an influenza virus. It commonly affects infants and children. The second most common bacterial cause of meningitis is Neisseria meningitidis (meningococcus). Meningococcal meningitis affects people of all ages and tends to occur in epidemics, especially among those who live in crowded conditions. An outbreak in the slums of Brazil in 1974–75 killed 11,000 people and left over 75,000 with permanent neurological complications. In 1996, an epidemic centered in the Sahel region of W Africa killed 16,000. In the United States it is seen most often in children and teens.

Strepococcus pneumoniae, also referred to as pneumococcus, is another cause of serious meningitis cases. It is the most common cause of meningitis in adults. It often accompanies pneumococcus infections in other parts of the body, such as the ear or sinuses. Other bacterial causes of meningitis include tuberculosis, leptospirosis, and Lyme disease.

Bacterial meningitis calls for emergency medical care and the administration of antibiotics. Close contacts of patients with bacterial meningitis may receive prophylactic antibiotics, such as rifampin. Definitive diagnosis can be made by laboratory tests of cerebrospinal fluid obtained by a lumbar puncture (spinal tap). Twenty to thirty percent of children who survive bacterial meningitis sustain permanent neurological damage such as deafness, mental retardation, or convulsions. Since the late 1980s, routine vaccination of young children against Hib has virtually eliminated Hib disease in the United States. Routine vaccination against meningococcal meningitis is recommended for pre-adolescents, and vaccination is also recommended for persons in the military or traveling to parts of Africa where the disease is endemic. The meningococcal vaccine does not provide protection against all meningococcus strains.

Fungal meningitis

Fungal meningitis has been on the rise in the United States due to opportunistic infection with Cryptococcus neoformans in people weakened by AIDS. In these patients, it is often fatal. It can be treated with the antifungals amphotericin B and fluconazole. Other causes include coccidioidomycosis and histoplasmosis.

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meningitis

Inflammation of the meninges. Bacteria (including meningococcus, among others), often from infection elsewhere, produce the most dangerous forms. Symptoms develop rapidly: vomiting, then severe bursting headache, then stiff neck. Young children may have convulsions. The patient may die within hours. Pus in cerebrospinal fluid can block brain passages and spinal spaces, leading to life-threatening hydrocephalus. Speedy diagnosis (by lumbar puncture) and treatment (with antibiotics) can prevent brain damage and death. Viral meningitis usually has a short course and requires no therapy.

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meningitis

inflammation of the membranes that surround the brain or spinal cord, caused by infection

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meningitis [‚men·ən′jīd·əs]

(medicine)

Inflammation of the meninges of the brain and spinal cord, caused by viral, bacterial, and protozoan agents.

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Meningitis

Inflammation of the meninges. Certain types of meningitis are associated with distinctive abnormalities in the cerebrospinal fluid. With certain types of meningitis, especially bacterial, the causative organism can usually be recovered from the fluid. See Central nervous system

Meningeal inflammation in most cases is caused by invasion of the cerebrospinal fluid by an infectious organism. Noninfectious causes also occur. For example, in immune-mediated disorders antigen-antibody reactions can cause meningeal inflammation. Other noninfectious causes of meningitis are the introduction into the cerebrospinal fluid of foreign substances such as alcohol, detergents, chemotherapeutic agents, or contrast agents used in some radiologic imaging procedures. Meningeal inflammation brought about by such foreign irritants is called chemical meningitis. Inflammation also can occur when cholesterol-containing fluid or lipid-laden material leaks into the cerebrospinal fluid from some intracranial tumors.

Bacterial meningitis is among the most feared of human infectious diseases because of its possible seriousness, its rapid progression, its potential for causing severe brain damage, and its frequency of occurrence. Most cases of bacterial meningitis have an acute onset. Common clinical manifestations are fever, headache, vomiting, stiffness of the neck, confusion, seizures, lethargy, and coma. Symptoms of brain dysfunction are caused by transmission of toxic materials from the infected cerebrospinal fluid into brain tissue and the disruption of arterial perfusion and venous drainage from the brain because of blood vessel inflammation. These factors also provoke cerebral swelling, which increases intracranial pressure. Before antibiotics became available, bacterial meningitis was almost invariably fatal. See Antibiotic

Most types of acute bacterial meningitis are septic-borne in that they originate when bacteria in the bloodstream (bacteremia, septicemia) gain entrance into the cerebrospinal fluid. Meningitis arising by this route is called primary bacterial meningitis. Secondary meningitis is that which develops following direct entry of bacteria into the central nervous system, which can occur at the time of neurosurgery, in association with trauma, or through an abnormal communication between the external environment and the cerebrospinal fluid.

Many viruses can cause meningeal inflammation, a condition referred to as viral aseptic meningitis. The most common viral causes include the enteroviruses, the various herpesviruses, viruses transmitted by arthropods, the human immunodeficiency virus type I (HIV-1), and formerly, the mumps virus. If the virus attacks mainly the brain rather than the spinal cord, the disorder is termed viral encephalitis. See Animal virus, Arboviral encephalitides, Enterovirus, Herpes

Fungal, parasitic, and rickettsial meningitis are less common in the United States than are bacterial and viral. These infections are more likely to be subacute or chronic than those caused by bacteria or viruses; in most cases, the meningeal inflammation is associated with brain involvement. An acute form of aseptic meningitis can occur in the spirochetal diseases, syphilis and Lyme disease. See Lyme disease, Medical mycology, Medical parasitology, Rickettsioses, Syphilis