The approach to the patient with acute bacterial meningitis depends on prompt recognition of the clinical syndrome and performance of a lumbar puncture to determine whether the cerebrospinal fluid values are consistent with the diagnosis. This article outlines the typical clinical features of and diagnostic approach to the patient with bacterial meningitis and discusses recommendations for antimicrobial and adjunctive therapies.
More than 85 percent of patients with acute bacterial meningitis present with the classic triad of fever, headache and stiff neck. The meningismus may be subtle, marked or accompanied by Kernig's and/or Brudzinski's signs (which occur in about 50 percent of adult patients). Other signs and/or symptoms include vomiting (35 percent of patients) seizures (30 percent of patients), and cranial nerve palsies and focal cerebral signs (10 to 20 percent of patients). Papilledema occurs in less than 1 percent of patients during the early phase of infection, and its presence should suggest an alternative diagnosis.
Some categories of patients may not present with many of these classic symptoms and/or signs. In neonates, clinical clues to the presence of meningitis include temperature instability (hypothermia or hyperthermia), listlessness, high-pitched crying, fretfulness, lethargy, refusal to eat, a weak sucking response, irritability, vomiting, diarrhea and respiratory distress. Because neonates usually do not have meningismus, a change in the child's affect or state of alertness is one of the most important signs. A bulging fontanelle may occur late in the course of the disease in one third of neonates. Forty percent of neonates have seizures. In the elderly patient with bacterial meningitis, the presentation may be insidious, with lethargy or obtundation, no fever and variable signs of meningeal irritation. Examination of cerebrospinal fluid in these patients is crucial in order to diagnose bacterial meningitis.
Examination of cerebrospinal fluid values following lumbar puncture is necessary to make a definitive diagnosis of bacterial meningitis; typical findings are shown in Table 1. In patients with typical cerebrospinal fluid findings of bacterial meningitis and a negative cerebrospinal fluid Gram stain, several other laboratory tests are available to assist in making an etiologic diagnosis.
TABLE 1 Typical Cerebrospinal Fluid Values in Patients with Bacterial Meningitis
Duration of Therapy
The duration of antimicrobial therapy in patients with bacterial meningitis has traditionally been from 10 to 14 days for non-meningococcal isolates. However, several studies have documented that seven days of therapy is safe and effective for H. influenzae type b meningitis, although treatment durations must be individualized and some patients may require longer courses. Meningococcal meningitis can be treated for seven days with intravenous penicillin, although some authors have suggested that four days of therapy is adequate.
In patients with bacterial meningitis caused by enteric gram-negative bacilli, treatment should be continued for three weeks because of the high rate of relapse in patients treated with shorter courses of therapy. S. pneumoniae meningitis should be treated for 10 to 14 days. Antimicrobial therapy lasting from 14 to 21 days is recommended for meningitis caused by L. monocytogenes, Staphylococcus aureus and S. agalactiae. However, it is important to note that these treatment durations are based more on tradition than on rigidly standardized clinical trials. Table 4 summarizes current recommendations for the duration of antibiotic treatment.
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ALLAN R. TUNKEL, M.D., PH.D. is associate professor of medicine and associate chair for education at Allegheny University of the Health Sciences, MCP * Hahnemann School of Medicine, Philadelphia, and director of the internal medicine residency program at Allegheny University Hospitals, Philadelphia. Dr. Tunkel graduated from the UMDNJ--New Jersey Medical School, Newark, where he also received his Ph.D. He completed an internship and residency in internal medicine at the Medical College of Pennsylvania Hospital, Philadelphia. Dr. Tunkel also completed a fellowship in infectious diseases at the University of Virginia Health Sciences Center, Charlottesville.
W. MICHAEL SCHELD, M.D. is professor of medicine and neurosurgery, associate chair for residency programs and director of the internal medicine residency training program at the University of Virginia School of Medicine, Charlottesville. He received his medical degree from Cornell University Medical College, New York City and completed an internship, residency and fellowship in infectious diseases at the University of Virginia Health Sciences Center.
Address correspondence to Allan R. Tunkel, M.D., Ph.D. Department of Internal Medicine, Allegheny University Hospitals, MCP, 3300 Henry Ave., Philadephia, PA 19129.
Dr. Tunkel is a member of the speaker's bureaus for Pfizer Inc. and Roche Pharmaceuticals.
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