In suspected meningitis, which CSF profile best differentiates bacterial from viral meningitis?

• A. Bacterial: pleocytosis with neutrophil predominance, high protein, low glucose; Viral: lymphocytic predominance, normal or mildly elevated protein, normal glucose
• B. Bacterial: lymphocytic predominance; Viral: neutrophil predominance
• C. Bacterial: low protein; Viral: high protein
• D. Bacterial: high glucose; Viral: low glucose

Answer: (A)

The key idea is that the CSF inflammatory pattern helps distinguish bacterial from viral meningitis. Bacterial meningitis typically causes a pleocytosis dominated by neutrophils, with a marked rise in protein and a low glucose level. This happens because bacteria provoke a strong neutrophilic response, the inflammatory process increases blood-brain barrier permeability (raising protein), and bacteria/tin leukocytes consume glucose, lowering CSF glucose.

Viral meningitis, on the other hand, usually shows a predominance of lymphocytes, with only mild to moderate protein elevation and normal or near-normal glucose. The inflammation is less intense regarding glucose consumption, and the blood-brain barrier disruption is less severe, so glucose stays normal.

So, the CSF profile of neutrophil-predominant pleocytosis with high protein and low glucose points to bacterial meningitis, while lymphocyte-predominant pleocytosis with normal glucose points to viral meningitis.