Bacterial Meningitis
Bacterial meningitis is infection of the layers of tissue covering the brain and spinal cord (meninges).
Meningitis can occur at any age. Meningitis is similar in older children, adolescents, and adults (see Section 6, Chapter 89) but different in newborns and infants.
Children at particular risk for meningitis include those with sickle cell disease and those lacking a spleen. Children with congenital deformities of the face and skull may have defects in the bones that allow bacteria access to the meninges. Children who have a weakened immune system, such as those with AIDS or those who have received chemotherapy, are more susceptible to meningitis.
Causes
Meningitis in newborns is typically caused by bacteria acquired from the birth canal. The most common such bacteria are group B streptococci, Escherichia coli, and Listeria monocytogenes. Older children usually develop infection from contact with respiratory secretions from infected people. Bacteria that infect older children include Streptococcus pneumoniae and Neisseria meningitidis. Haemophilus influenzae type b was the most common cause of meningitis, but the widespread use of vaccination against that organism has now made it a rare cause. A new, improved vaccine against Streptococcus pneumoniae also should make this organism a rare cause of childhood meningitis.
Symptoms and Diagnosis
Older children and adolescents with meningitis typically have a few days of increasing fever, headache, confusion, and a stiff neck. They may have an upper respiratory tract infection that is unrelated to the meningitis. Newborns and infants rarely develop a stiff neck and are unable to communicate specific discomfort. These younger children become fussy and irritable (particularly when they are held) and stop feeding--important signs that should alert parents to a possibly serious problem. Sometimes newborns and infants have fever, vomiting, or a skin rash. One third have seizures. The nerves controlling some eye and facial movements may be damaged, causing an eye to turn inward or outward or the facial expression to become lopsided. In about 25% of newborns with meningitis, increased pressure of the fluid around the brain may make the fontanelles (the soft spots between the skull bones) bulge or feel firm. These symptoms usually develop over at least 1 to 2 days, but some infants, particularly those between birth and 3 or 4 months old, become ill very rapidly, progressing from health to near death in less than 24 hours.
Pockets of pus (abscesses) may rarely form within the brain of infants with meningitis because of certain germs. As the abscesses grow, pressure on the brain increases, resulting in vomiting, head enlargement, and bulging fontanelles.
A doctor diagnoses bacterial meningitis by examining and culturing a sample of cerebrospinal fluid obtained through a spinal tap (lumbar puncture (see Section 6, Chapter 77)). Doctors also perform blood cultures to look for bacteria in the bloodstream. Ultrasound examination or computed tomography (CT) may be used to determine if an abscess is present.
Prevention, Prognosis, and Treatment
Health care professionals can help prevent bacterial meningitis by ensuring that all children receive the Haemophilus influenzae type b and Streptococcus pneumoniae vaccines.
Even with timely, appropriate treatment, as many as 30% of newborns with bacterial meningitis die. In older infants and children, mortality varies from 3 to 5% when the cause is Haemophilus influenzae type b, 5 to 10% when the cause is Neisseria meningitidis, and 10 to 15% when the cause is Streptococcus pneumoniae. Nearly 25% of children with a brain abscess die.
Of the infants who survive, 10 to 20% develop serious brain and nerve damage, such as enlargement of the ventricles (hydrocephalus), deafness, cerebral palsy, and mental retardation. Up to 50% have mild residual problems, such as learning disorders, mild hearing loss, or occasional seizures.
Doctors give high doses of antibiotics intravenously as soon as they suspect meningitis. Very sick children receive antibiotics even before a spinal tap is performed. A doctor chooses an antibiotic based on the type of bacteria causing the meningitis. Children older than 6 weeks of age sometimes are given corticosteroids to help prevent permanent neurologic problems.
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