Diseases & Conditions
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 Infections of the Brain and Spinal Cord: Acute Bacterial Meningitis ) but different in newborns and infants.
Children at particular risk of 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.
Meningitis in newborns usually results from an infection of the bloodstream (sepsis). The infection is typically caused by bacteria acquired from the birth canal, most commonly group B streptococci, Escherichia coli , and Listeria monocytogenes . Older infants and children usually develop infection through contact with respiratory secretions from infected people. Bacteria that infect older infants and children include Streptococcus pneumoniae and Neisseria meningitidis. Haemophilus influenzae type b was the most common cause of meningitis, but widespread vaccination against that organism has now made it a rare cause. Newer, improved vaccines against Streptococcus pneumoniae and Neisseria meningitidis (pneumococcal and meningococcal conjugate vaccines) should also make these organisms rare causes 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.
Rarely, pockets of pus (abscesses) form within the brain of infants with meningitis due to certain bacteria. 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 Diagnosis of Brain, Spinal Cord, and Nerve Disorders: How a Spinal Tap Is Done ). Doctors also order blood cultures to look for bacteria in the bloodstream. Ultrasonography or computed tomography (CT) may be used to determine if an abscess is present.
Prevention, Prognosis, and Treatment
Health care practitioners and parents can help prevent bacterial meningitis by ensuring that all young children receive the Haemophilus influenzae type b and Streptococcus pneumoniae conjugate vaccines and that older children and adolescents receive either the Neisseria meningitidis polysaccharide or conjugate vaccine.
Even with timely, appropriate treatment, as many as 25% of newborns with bacterial meningitis die. In older infants and children, mortality rates vary from 3 to 5% when the cause is Haemophilus influenzae type b, 5 to 10% when the cause is Neisseria meningitidis, and 10 to 20% when the cause is Streptococcus pneumoniae .
Of the newborns who survive, 15 to 25% develop serious brain and nerve problems, such as enlargement of the ventricles (hydrocephalus), deafness, cerebral palsy, and mental retardation. Up to 30% have mild residual problems, such as learning disorders, mild hearing loss, or occasional seizures. Older infants and children tend to have fewer of these complications.
Doctors give high doses of antibiotics intravenously as soon as they suspect meningitis. Very sick children receive antibiotics even before a spinal tap is done. When culture results from the spinal tap become available, doctors change the antibiotics, if needed, based on the type of bacteria causing the meningitis. Children older than 6 weeks are often given corticosteroids to help prevent permanent neurologic problems. Sometimes a second culture and spinal tap are done to determine whether the antibiotics are working fast enough.
Last full review/revision June 2006 by Geoffrey A. Weinberg, MD
Source: The Merck Manual Home Edition