INTRODUCTION: Although there is a broad differential in a patient presenting with fever and headache, a few infectious diagnoses must be ruled in or out immediately. Acute bacterial meningitis is a critical diagnosis because delay of appropriate antimicrobial therapy increases morbidity and mortality. Distinguishing among bacterial, viral, and more chronic meningitides requires the integration of multiple clinical and laboratory findings. EPIDEMIOLOGY: The Centers for Disease Control and Prevention (CDC) estimates that from 1988 to 1999, more than 800,000 people were hospitalized for meningitis. The majority of these hospitalizations were for viral (50%) and bacterial meningitis (23%). Fungal meningitis accounted for 9% of the hospitalizations and unspecified for 18%. The highest incidence of nonfungal meningitis was in infants younger than 1 year old, whereas fungal meningitis was more common in young adults. Because these numbers describe only hospitalized patients, they underrepresent the actual incidence, especially of viral meningitis. CLINICAL FEATURES: Meningitis is classically characterized as a triad of fever, neck stiffness, and altered mental status, though it may be more appropriate to consider the triad of fever, headache, and meningismus (Table 39.1). Fewer than half of the patients with bacterial meningitis will present with the complete “classic” triad, though most present with headache. In retrospective studies, fever is the most common symptom, though many of these did not evaluate headache as a clinical feature of meningitis.
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