A 6-year-old boy is brought to the emergency department by his parents with a 2-day history of fever and headaches. The parents report that he vomited once this afternoon. All of his vaccinations are up-to-date and he has no significant past medical history. His temperature is 38.7 C (102 F). Examination shows mild pharyngeal erythema in addition to neck stiffness. Cerebrospinal fluid analysis reveals the following:
Glucose 70 mg/dL Protein 85 mg/dL Leukocytes 300/mm3 Differential Neutrophils 15% Lymphocytes 85% Red blood cells none
Which of the following infectious agents is most likely to have caused this patient's illness?
Differences between bacterial & viral meningitis | ||
Viral | Bacterial | |
Common microbes |
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CSF cell differential |
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CSF glucose & protein |
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CSF Gram stain & culture |
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CSF = cerebrospinal fluid; WBC = white blood cell. | ||
This child has clinical evidence of meningitis (fever, headache, vomiting, stiff neck). Analysis of the cerebrospinal fluid (CSF) shows normal glucose, marginally elevated protein (generally <150 mg/dL), and pleocytosis with a lymphocytic predominance. This pattern suggests aseptic meningitis, which is usually viral in etiology.
Enteroviruses (eg, coxsackievirus, echovirus, poliovirus) are responsible for >90% of cases. Clinical symptoms are similar to meningitis caused by bacterial or fungal pathogens. However, aseptic meningitis is generally less severe, and focal neurologic signs, seizures, and alterations in mental status are absent. The presence of any of these should prompt consideration of other conditions, including bacterial meningitis, encephalitis, and intracranial hemorrhage. A negative Gram stain and sterile culture will further support the diagnosis of aseptic meningitis.
(Choice A) Coronaviruses are a common cause of cold symptoms and have caused fatal respiratory illnesses (eg, severe acute respiratory syndromes). They are not a common cause of viral meningitis.
(Choice B) Cryptococcus neoformans is a common cause of meningitis in immunocompromised patients (eg, AIDS patients). The diagnosis is made by testing for cryptococcal antigens or by identifying India ink-stained organisms in the CSF.
(Choice D) The mumps virus can cause aseptic meningitis, but this would be extremely unlikely in this fully immunized child. Meningitis caused by mumps is accompanied by parotitis in 50% of cases.
(Choices E, F, and G) Streptococcus pneumoniae and Neisseria meningitidis are the most common causes of bacterial meningitis in adults; S agalactiae (group B Streptococcus) is the most common cause of meningitis in neonates. Bacterial and viral meningitis both cause fever, nuchal rigidity, and headache. However, this patient's CSF analysis is more suggestive of aseptic meningitis.
Educational objective:
Fever; meningeal signs (eg, headache, neck stiffness); and cerebrospinal fluid that shows lymphocytic pleocytosis, a modestly elevated protein level (<150 mg/dL), and normal glucose are suggestive of aseptic meningitis. Enteroviruses are the most common cause of aseptic meningitis.