74 - Bacterial meningitis

Summary

Clinical presentation

The classic clinical presentation in patients with bacterial meningitis is that of fever, headache, meningismus, and signs of cerebral dysfunction (confusion, delirium, or a declining level of consciousness). In a review of 493 cases of acute bacterial meningitis in adults, the classic triad (i.e., fever, nuchal rigidity, and change in mental status) was found in only two-thirds of patients, but all had at least one of these findings. In another review of 696 episodes of community-acquired bacterial meningitis, the triad of fever, neck stiffness, and altered mental status was present in only 44% of episodes, although almost all patients (95%) presented with at least two of the four symptoms of headache, fever, stiff neck, and altered mental status. The meningismus may be subtle, marked, or accompanied by Kernig and/or Brudzinski signs. However, in a prospective study that examined the diagnostic accuracy of meningeal signs in adults with suspected meningitis, the sensitivity of these findings was only 5% for Kernig sign, 5% for Brudzinski sign, and 30% for nuchal rigidity, indicating that they did not accurately distinguish patients with meningitis from those without meningitis, and the absence of these findings did not rule out the diagnosis of bacterial meningitis. Cranial nerve palsies and focal cerebral signs are seen in 10% to 20% of cases. In an observational study of 696 patients with community-acquired bacterial meningitis, cerebral infarction occurred in 25% of episodes, and in 36% of those specifically with pneumococcal meningitis. Seizures occur in about 30% of patients. Papilledema is observed in less than 5% of cases early in infection, and its presence should suggest an alternative diagnosis. As meningitis progresses, patients may develop signs of increased intracranial pressure (e.g., coma, hypertension, bradycardia, and palsy of cranial nerve III).