What CSF findings are typical of acute bacterial meningitis?

• A. Elevated opening pressure; high protein; low glucose; neutrophilic; Gram stain/culture positive
• B. Low opening pressure; low protein; high glucose
• C. Normal CSF
• D. High lymphocytes

Answer: (A)

In acute bacterial meningitis, the CSF changes reflect an intense bacterial invasion and inflammation of the meninges. The opening pressure is typically elevated because inflammation increases intracranial pressure. Protein rises because the blood–brain barrier becomes leaky, allowing proteins to flood into the CSF. Glucose drops since bacteria consume glucose and immune cells also use glucose, reducing its level in the CSF. The cellular response is neutrophilic predominance, which is the hallmark of an acute bacterial infection in the CSF. In support of the diagnosis, Gram stain or culture of the CSF is often positive, revealing the causal organism.

This pattern helps distinguish bacterial meningitis from other meningitis etiologies. Viral meningitis, for example, usually shows normal or only mildly elevated opening pressure, normal or only modestly elevated protein, normal glucose, and a lymphocytic predominance with usually negative Gram stain and culture.