Which CSF finding is most typical for acute bacterial meningitis compared to viral meningitis?

• A. Lymphocytic pleocytosis
• B. Neutrophilic pleocytosis with elevated protein and decreased glucose
• C. Normal glucose
• D. Decreased opening pressure

Answer: (B)

CSF findings in acute bacterial meningitis show a neutrophil-predominant pleocytosis with high protein and low glucose. This pattern reflects an acute neutrophilic inflammatory response in the subarachnoid space, increased permeability allowing proteins to enter the CSF, and consumption of glucose by bacteria plus impaired glucose transport. In contrast, viral meningitis typically has a lymphocytic pleocytosis, with only mild to moderate protein elevation and normal glucose, since the inflammatory process is less disruptive to glucose handling. Opening pressure is often elevated with bacterial meningitis due to intense meningeal inflammation, whereas it’s usually normal or only mildly elevated in viral meningitis. Thus, neutrophilic pleocytosis with elevated protein and decreased glucose best distinguishes bacterial from viral meningitis.