Meningitis
LIFE-THREATENING DISORDERWith meningitis, the brain and the spinal cord meninges become inflamed, usually as a result of bacterial infection. Such inflammation may involve all three meningeal membranes—the dura mater, arachnoid, and pia mater.
Age AlertAbout 70% of cases occur in children younger than age 5. Also, incidence is increasing among college students who reside in dormitories.
The prognosis is good and complications are rare, especially if the disease is recognized early and the infecting organism responds to an antibiotic. However, mortality in patients with untreated meningitis is 70% to 100%. The prognosis is poorer for infants, elderly people, and those who are immunocompromised.
Causes
Meningitis is almost always a complication of another bacterial infection—bacteremia (especially from pneumonia, empyema, osteomyelitis, and endocarditis), sinusitis, otitis media, tooth abscess, encephalitis, myelitis, or brain abscess—usually caused by Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae, and Escherichia coli. Viral meningitis is generally less severe, and is usually the result of a complication of an existing viral infection.
Meningitis may also follow skull fracture, a penetrating head wound, lumbar puncture, or ventricular shunting procedures. Aseptic meningitis may result from a virus or other organism. Sometimes no causative organism can be found.
Meningitis commonly starts out as an inflammation of the pia-arachnoid, which may progress to congestion of adjacent tissues and destroy some nerve cells.
Signs and symptoms
Typical signs and symptoms include the following features.
Cardinal signs and symptoms
The cardinal signs and symptoms of meningitis are those of infection—including fever, chills, and malaise—and those of increased intracranial pressure (ICP)—including headache, vomiting and, rarely, papilledema.
Meningeal irritation
Signs of meningeal irritation include nuchal rigidity, positive Brudzinski’s and Kernig’s signs, exaggerated and symmetrical deep tendon reflexes, and opisthotonos (a spasm in which the back and extremities arch backward so that the body rests on the head and heels).
Other manifestations
Other signs and symptoms of meningitis include sinus arrhythmias; irritability; photophobia, diplopia, and other visual problems; and delirium, deep stupor, and coma. An infant may show signs of infection but often is simply fretful and refuses to eat. Such an infant may vomit a great deal, leading to dehydration; this prevents a bulging fontanel and thus masks this important sign of increased ICP.
As the illness progresses, twitching, seizures (in 30% of infants), or coma may develop. Most older children have the same symptoms as adults. In those
with subacute meningitis, onset may be insidious.
with subacute meningitis, onset may be insidious.
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