Neonatal Meningitis. Streptococcus agalactiae (group B streptococcus) and Escherichia coli cause three fourths of all infections in the neonate. Prematurity is the greatest risk factor for infection in neonates.
Infancy
In infants, Haemophilus influenzae is the most common bacterium causing meningitis. The widespread use of H. influenzae type B (HiB) conjugate vaccines has decreased the incidence of HiB meningitis by 95%.
Streptococcus pneumoniae is the second most common cause of meningitis.
Neisseria meningitidis has the highest attack rate in children younger than 2 years. Most often the infant is feverish, lethargic.
Childhood. The frequency of meningitis decreases markedly in children older than 2 years, and it remains at a relatively constant level until adulthood. Etiologies include H influenzae, S pneumoniae.
Newborns
In the newborn, signs and symptoms of bacterial meningitis are often very similar to those of sepsis or other serious illnesses.
Neonates with acute bacterial meningitis often lack meningismus. Meningitis may manifest as hyperthermia.
Older Infants and Children
In older infants and children, initial symptoms of bacterial meningitis consist of fever.
Suspecting the Diagnosis
Meningitis is frequently associated with acute otitis media, pneumonia, and even gastroenteritis. The most important consideration in suspecting acute bacterial meningitis.
Lumbar Puncture
Analysis of CSF by LP is the basis for evaluation of suspected meningitis. A CT scan is not necessary prior to an LP In children without evidence of increased intracranial pressure, focal neurological findings, or papilledema.
If increased intracranial pressure is suspected, LP should be postponed, a blood culture obtained and empiric antimicrobial therapy initiated while the CT scan is pending.
CSF studies include cell count, protein, glucose, bacterial culture, and Gram's stain. Opening pressures are helpful in older children and adults, but they are usually not obtained.
Treatment of Meningitis
Antibiotics
Antibiotics should be initiated immediately on suspicion of bacterial meningitis. Initial agents are chosen empirically because culture results will not be available for 24 hours.
In neonates without grossly purulent CSF, ampicillin and gentamicin are the agents of choice while awaiting culture results.
Three weeks of parenteral therapy is required.
Acute Complications of Bacterial Meningitis
Cerebral Edema
Within the first 2 days of bacterial meningitis, the most common complication is cerebral edema.
Increased intracranial pressure, secondary to cerebral edema manifests as coma, absence of a oculocephalic reflex (ie, fixed response to the doll head maneuver), or fixed eye deviation.
Subdural Empyema
Subdural empyema usually occurs in infants with severe Gram-negative meningitis.
Ventriculitis
Ventriculitis is a common complication of Gram-negative and group B streptococcal meningitis.
Brain Abscess is an uncommon complication of bacterial meningitis.
Chemoprophylaxis for Pediatric Meningitis
Haemophilus Influenzae (HiB)
Household contacts should receive rifampin only if there is one or more child less than 4 years.