Information on the following diseases can be found in the Related Disorders section of this report:

• Meningitis
• Encephalitis
• Rocky Mountain Spotted Fever

Meningococcal meningitis is one of the three most common types of bacterial meningitis. It progresses more rapidly than any other acute form of bacterial meningitis. Meningococcal meningitis involves the central nervous system. In adults and children it is often preceded by respiratory illness or a sore throat. In its acute form, the disorder is characterized by fever, headache, a stiff neck, nausea, and vomiting. Adults may become seriously ill within hours. In children the course of the infection may be even shorter.

Symptoms among older children and adults may progress from irritability to confusion, drowsiness, and stupor, possibly leading to coma. Some affected individuals may experience convulsions. Skin rashes occur in about half of all individuals with meningococcal meningitis. Swelling or inflammation of the brain (cerebral edema or ventriculitis), or hydrocephalus (accumulation of fluid in the brain cavity) may also occur. Additional symptoms may include chills; sweating; weakness; loss of appetite; muscle pain (myalgia) of the lower back or legs; or inability to tolerate bright light (photophobia). (For more information on hydrocephalus, choose "hydrocephalus" as your search term in the Rare Disease Database).

Dehydration often occurs in individuals with meningococcal meningitis. In some cases, collapse of the blood vessels may lead to shock (Waterhouse-Friderichsen syndrome) when the meningococcus bacteria spread to the blood (septicemia). Later symptoms may include paralysis of one side of the body (hemiparesis), hearing loss, or additional neurological abnormalities.

The course of meningococcal meningitis is less predictable among infants between three months and two years of age. Fever, refusal of feedings, vomiting, irritability, and convulsions usually occur. A high-pitched cry, and a bulging or tight soft spot (fontanel) on the crown of the head (where the parts of the skull's still unhardened bones join) may also occur. Since the incidence of most types of meningitis is highest among this age group, any unexplained fever needs to be closely watched. Cerebral fluid may accumulate just inside the tough outer membrane covering the brain (subdural effusions) after several days. Warning signs may include seizures, a persistent fever, and an enlarging head size. A brain abscess or subdural pus accumulation may also occur. Water accumulating in the brain (hydrocephalus), deafness and slowed mental and physical development are possible consequences of meningitis.

Meningococcal meningitis is caused by a bacterium known as Neisseria meningitidis. There are several types, or serogroups, of Neisseria meningitidis. The most common of these serogroups are A, B, C, D, X, Y, 29E, and W135. Serogroups A, B, C, and Y are responsible for most meningococcal diseases.

The bacterium is spread by droplets in the air or close contact with an infected person. It collects in the nasopharynx, or post-nasal space, that connects the nasal cavities with the throat. The bacterium is transported to the membranes (meninges) around the brain or spinal cord by the blood. It usually spreads from nearby infected areas such as the nasal sinuses or from the cerebrospinal fluid.

Meningococcal meningitis primarily affects infants, children, and young adults. Males are affected slightly more than females. Meningococcal meningitis can occur as an epidemic in subgroups such as people in the military services or students in dormitories. Vaccines can help control meningitis epidemics caused by serogroups A, C, Y, or W135.

In the United States, most cases of meningococcal meningitis involve infants and military recruits, and tend to be caused by serogroup B of the bacteria. It occurs most often during winter or spring. Between 1984 and 1986, 2,400 to 2,700 cases of meningococcal infection were reported annually in the United States. Recently, it has been estimated that this infection affects about one in 100,000 people. In the United States, over 3,400 cases were reported during 1996.

Excluding epidemics, approximately 1.2 million cases of bacterial meningitis occur worldwide every year. The disease occurs with greater frequency in temperate climates.

Symptoms of the following disorders may resemble those of meningococcal meningitis. Comparisons may be useful for a differential diagnosis:

In general, meningitis is characterized by inflammation of the membranes (meninges) around the brain or spinal cord. This inflammation may be caused by different types of bacteria, viruses, fungi, malignant tumors, or reactions to certain injections into the spinal canal. (For more information on other types of Meningitis, choose "meningitis" as your search term in the Rare Disease Database.)

Encephalitis is a brain infection. There are different types of this disorder that are caused by different types of viruses. Encephalitis may also be caused by hypersensitivity initiated by a virus or other protein that is foreign to the body. Symptoms may include headache, drowsiness, hyperactivity, and/or general weakness. This disorder may have some symptoms similar to those of meningitis such as a stiff neck, altered reflexes, confusion, speech disorders, convulsions, paralysis and coma. (For more information choose "Encephalitis" as your search term in the Rare Disease Database.)

Rocky Mountain Spotted Fever is an acute infectious disorder transmitted to humans through the bite of an infected tick, usually in wooded areas of the midwest, eastern and southeastern United States. Fever and rash are among major symptoms. The rash may not develop in all cases, possibly making diagnosis difficult. Swelling (edema), headaches, chills, weakness and muscle pains may also occur. Severe headaches, lethargy, confusion, delirium, focal neurological deficits, increased pressure in the skull leading to pressure on and swelling of the optic disk (papilledema), seizures and/or coma may occur in untreated cases as the nervous system is progressively affected. Some individuals may have a stiff neck due to muscle pain (myalgia) or irritation of membranes surrounding the brain and spinal cord tissue (meningismus). (For more information on this disorder, choose "Rocky Mountain Spotted Fever" as your search term in the Rare Disease Database.)

Diagnosis
Testing for meningococcal meningitis may include imaging techniques such as CT scans or magnetic resonance imaging (MRI). Other testing may include examination of the blood and/or skin. Diagnosis is made by laboratory examination of the cerebrospinal fluid that often reveals the presence of bacterial meningitis.

Treatment
Meningococcal meningitis is usually treated with antibiotic drugs used against the bacteria causing the infection. Penicillin G or ampicillin are often prescribed. Alternative drugs include chloramphenicol, cefuroxime, cefotaxime, ceftriaxone, or ceftizoxime. Family members of those infected can be treated with Rifampin as a preventative measure; however, for pregnant women, ceftriaxone is recommended.

Epidemics caused by the bacterium (Neisseria meningitidis) serogroups A, C, Y, or W135 can be controlled with a meningococcal vaccine that prevents infection in vaccinated people.

TEXTBOOKS
Bennett JC, Plum F., eds. Cecil Textbook of Medicine. 20th ed. Philadelphia, PA: W.B. Saunders Co; 1996:1618-21.

JOURNAL ARTICLES
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Ragunathan L, et al., Clinical features, laboratory findings and management of meningococcal meningitis in England and Wales: report of a 1997 survey. Meningococcal meningitis: 1997 survey report. J Infect. 2000;40:74-9.

Kastenbauer S, et al., Prevention of meningococcal meningitis. Nervenarzt. 2000;71:134-7.

Bonadio WA, et al., Bacterial meningitis in older children. Am J Dis Child. 1990;144:463-5.

Chang KH, et al., Gd-dtpa-enhanced MR imaging of the brain in patients with meningitis: comparison with CT. AJR Am J Roentgenol. 1990;154:809-16.

Girgis NI, Ceftriaxone alone compared to ampicillin and chloramphenicol in the treatment of bacterial meningitis. Chemotherapy. 1988;34:16-20.

Masterton RG, et al., Control of an outbreak of group c meningococcal meningitis with a polysaccharide vaccine. J Infect. 1988;17:177-182.