What diagnostic test is essential to differentiate bacterial from viral meningitis?

What diagnostic test is essential to differentiate bacterial from viral meningitis?

• A. MRI brain
• B. Lumbar puncture with CSF analysis
• C. CT scan of head
• D. Blood culture only

Answer: (B)

Differentiating bacterial from viral meningitis relies on directly examining the cerebrospinal fluid obtained by lumbar puncture. This analysis reveals the characteristic differences in the CSF that reflect the underlying pathogens. In bacterial meningitis, you typically see a neutrophil-dominant (polymorphonuclear) pleocytosis, low glucose levels (because bacteria consume glucose), and high protein, often with elevated opening pressure; Gram stain or culture can identify the organism. In viral meningitis, the CSF usually has a lymphocyte-predominant profile, normal or near-normal glucose, and only mildly elevated protein, with viral PCR helping to identify the specific virus. Imaging and blood cultures can be helpful adjuncts but do not reliably distinguish bacterial from viral meningitis; they don’t sample the CSF directly to make the differentiation. So the essential test is lumbar puncture with CSF analysis.

Differentiating bacterial from viral meningitis relies on directly examining the cerebrospinal fluid obtained by lumbar puncture. This analysis reveals the characteristic differences in the CSF that reflect the underlying pathogens. In bacterial meningitis, you typically see a neutrophil-dominant (polymorphonuclear) pleocytosis, low glucose levels (because bacteria consume glucose), and high protein, often with elevated opening pressure; Gram stain or culture can identify the organism. In viral meningitis, the CSF usually has a lymphocyte-predominant profile, normal or near-normal glucose, and only mildly elevated protein, with viral PCR helping to identify the specific virus. Imaging and blood cultures can be helpful adjuncts but do not reliably distinguish bacterial from viral meningitis; they don’t sample the CSF directly to make the differentiation. So the essential test is lumbar puncture with CSF analysis.