How is cerebrospinal fluid (CSF) testing used to differentiate the cause of viral meningitis?

Updated: Jul 17, 2018
  • Author: Cordia Wan, MD; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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CSF examination is the most important test in differentiating the cause of meningitis. Prior to lumbar puncture (LP), a computed tomography (CT) scan should be performed in patients with any abnormal neurologic sign, to exclude an intracranial lesion or obstructive hydrocephalus. [20] CSF culture remains the criterion standard in discerning bacterial or pyogenic from aseptic meningitis. Again, a partially-treated bacterial meningitis may present with a negative Gram stain result and thus appear aseptic.

Consider saving CSF for less common tests (ie, PCR for HIV and CMV) if the cause of meningitis is not certain after initial tests.

The exact sequence of testing for these agents depends on the patient’s clinical condition and on suggestive facts in his or her history and examination. For example, most cases of viral meningitis do not require PCR testing for HIV.

A high WBC count in the CSF (especially neutrophils), a high protein level, and a low glucose level should suggest a diagnosis of a bacterial meningitis, although some viral pathogens may produce similar CSF profiles.

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