In suspected meningitis, which CSF components are routinely analyzed during lumbar puncture?

• A. Brain tissue markers.
• B. Cell count, glucose, protein, and culture.
• C. Blood urea nitrogen.
• D. Serum electrolytes.

Answer: (B)

When meningitis is suspected, the analysis of cerebrospinal fluid focuses on features that reveal the type and extent of infection. The best-fit routine CSF components are the cell count, glucose, protein, and culture.

Cell count shows pleocytosis, indicating inflammation in the CSF. The type of cells helps distinguish bacterial from viral meningitis: bacterial infections typically cause a neutrophil-predominant pleocytosis, while viral infections more often produce lymphocytes.

Glucose (often compared to simultaneous serum glucose) is important because bacterial meningitis commonly lowers CSF glucose due to consumption by bacteria and inflammatory cells, whereas viral meningitis usually preserves CSF glucose.

Protein in CSF increases with inflammation and blood-brain barrier disruption, which is more pronounced in bacterial meningitis but can be elevated in other inflammatory states as well.

Culture (and Gram stain) identifies the causative organism, guiding targeted therapy, and can be positive in bacterial meningitis.

Brain tissue markers aren’t measured in routine CSF analysis. BUN and serum electrolytes are systemic tests, not CSF parameters, so they don’t reflect CSF findings during lumbar puncture.