Other forms of therapy There is no evidence that repeated drainage of CSF, a former practice, is therapeutically effective. In fact, increased CSF pressure in the acute phase of bacterial meningitis is largely a consequence of cerebral edema, in which case the lumbar puncture may predispose to cerebellar herniation. As already mentioned, a second lumbar puncture to gauge the effectiveness of treatment is generally not necessary, but it may be of value if the patient is worsening without explanation. Mannitol and urea have been employed with apparent success in cases of severe brain swelling with unusually high initial CSF pressures (400 mm H2O). Acting as osmotic diuretics, these agents enter cerebral tissue slowly, and their net effect is to decrease brain water. However, neither mannitol nor urea has been studied in controlled fashion in the management of meningitis. An adequate but not excessive amount of intravenous normal saline (and avoiding fluids with free water) should be given. Particular care should be taken with children to avoid hyponatremia and water intoxication—potential causes of brain swelling. Antiepileptic drugs need not be administered routinely but should be given if a seizure has occurred or possibly if there is evidence of cortical vein thrombosis.
Prophylaxis Household contacts of patients with meningococcal meningitis should be protected with antibiotic treatment. The risk of secondary cases is small for adolescents and adults, but ranges from 2 to 4 percent for those younger than 5 years of age and is probably higher in the elderly. A single dose of ciprofloxacin is effective. An alternative is a daily oral dose of rifampin—600 mg q12h in adults and 10 mg/kg q12h in children—for 2 days. If 2 weeks or more have elapsed since the index case was found, no prophylaxis is needed.
As mentioned, immunization against H. influenzae is steadily reducing the incidence of meningitis from this organism. Also, many institutions housing young adults, such as colleges and the military, have instituted programs of immunization against N. meningitidis.
Prognosis and Sequelae of Meningitis
Untreated, bacterial meningitis is usually fatal. The mortality rate of treated H. influenzae and meningococcal meningitis has remained approximately 5 percent for many years; in pneumococcal meningitis, the rate is considerably higher (approximately 15 percent), perhaps related to the older and sicker population that is affected. Fulminant meningococcemia, with or without meningitis, also has a high mortality rate because of the shock associated with adrenocortical hemorrhages (Waterhouse-Friderichsen syndrome). A disproportionate number of deaths from meningitis occur in infants and in the aged. The mortality rate is highest in neonates, from 40 to 75 percent in several reported series, and at least half of those who recover show serious neurologic sequelae. In adults, the presence of bacteremia, coma, seizures, and a variety of concomitant diseases—including alcoholism, diabetes mellitus, multiple myeloma, and head trauma—all worsen the prognosis. The triad of pneumococcal meningitis, pneumonia, and endocarditis (Osler triad) has a particularly high fatality rate.
Surprisingly often, it is impossible to explain the death of a patient with meningitis or at least to trace it to a single specific mechanism. The effects of overwhelming infection, with bacteremia and hypotension, or brain swelling and cerebellar herniation (see Rennick), are clearly implicated in some patients during the initial 48 h. These events may occur in bacterial meningitis of any etiology; however, they are far more frequent in meningococcal and pneumococcal infection. Some of the deaths occurring later in the course of the illness are attributable to respiratory failure, often consequent to aspiration pneumonia.