![]() This has been observed in young children with neutropenia and other immunocompromised states, and very early in the course of meningococcal meningitis. Rarely, patients with bacterial meningitis may present with normal or near-normal white blood cell counts, glucose levels, and protein levels. Although no single measure is diagnostic, a combination of abnormal CSF findings is highly suggestive of meningitis and helpful in determining the likely etiology ( Table 3). 16Īfter CSF is obtained, the Gram stain results, white and red blood cell counts, glucose levels, and protein levels should be evaluated immediately. Life-threatening herniation from lumbar puncture has not been reported in patients who are neurologically unremarkable before the procedure. ) The concern with lumbar puncture is the poorly quantified risk of herniation in patients with a space-occupying lesion or severe diffuse cerebral swelling, and the degree to which the risk can be recognized by a previous computed tomography scan. 15 (A video of a lumbar puncture is available at. Lumbar puncture is a safe procedure, although postprocedure headache occurs in about one third of patients. 14 Meningitis should be suspected in patients with those features previously noted that cannot be fully explained by other diagnoses. 13 The peripheral white blood cell count alone is not helpful in distinguishing bacterial from aseptic meningitis, particularly in young children (i.e., a normal white blood cell count does not rule out bacterial meningitis). ![]() Given the lack of specificity of clinical findings, the key to the diagnosis of meningitis is the evaluation of CSF. For example, in a study of 297 adults who underwent a lumbar puncture for suspected meningitis, only 80 (27 percent) had any degree of CSF pleocytosis, only 20 (6.7 percent) had a white blood cell count of 100 cells per μL or higher, and only three (1 percent) had culture-confirmed bacterial meningitis. 12 The illness course varies, with progression over hours to several days. 11 A recent history of upper respiratory tract infection is common in children with bacterial meningitis children are also more likely than adults to experience a seizure. 10 Similarly, the classical features of bacterial meningitis are not observed as often in younger children, who may present with subtle findings, such as lethargy and irritability. aeruginosa), Propionibacterium acnesĬompared with younger adults, persons 65 years and older with bacterial meningitis are less likely to have headache, nausea, vomiting, and nuchal rigidity, and are more likely to have seizures and hemiparesis. aureus, aerobic gram-negative bacilli (including P. Staphylococcus aureus, coagulase-negative staphylococci, aerobic gram-negative bacilli (including Pseudomonas aeruginosa)Ĭoagulase-negative staphylococci, S. Patients with penetrating trauma or postneurosurgery influenzae, group A beta-hemolytic streptococci Patients with basilar skull fracture or cochlear implant monocytogenes, aerobic gram-negative bacilli coliĬhildren and adults two to 50 years of ageĪdults older than 50 years, with altered cellular immunity, or with alcoholism Streptococcus pneumoniae, Neisseria meningitidis, S. Streptococcus agalactiae (group B streptococcus), Listeria monocytogenes, Escherichia coli, other gram-negative bacilli However, the use of conjugate vaccines has reduced the incidence of bacterial meningitis in children and adults. Among adults in developed countries, the mortality rate from bacterial meningitis is 21 percent. Within the United States, almost 30 percent of strains of pneumococci, the most common etiologic agent of bacterial meningitis, are not susceptible to penicillin. Concomitant therapy with dexamethasone initiated before or at the time of antimicrobial therapy has been demonstrated to improve morbidity and mortality in adults with Streptococcus pneumoniae infection. Empiric therapy should not be delayed, even if a lumbar puncture cannot be performed because results of a computed tomography scan are pending or because the patient is awaiting transfer. Empiric antimicrobial therapy based on age and risk factors must be started promptly in patients with bacterial meningitis. Clinical signs and symptoms are unreliable in distinguishing bacterial meningitis from the more common forms of aseptic meningitis therefore, a lumbar puncture with cerebrospinal fluid analysis is recommended. Although the annual incidence of bacterial meningitis in the United States is declining, it remains a medical emergency with a potential for high morbidity and mortality.
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