Question

Which CSF pattern is most characteristic of acute bacterial meningitis?

• A. Lymphocytosis, normal glucose and mildly increased protein
• B. Neutrophilic Pleocytosis, decreased glucose and increased protein
• C. Normal cell count, decreased protein and increased glucose
• D. Eosinophilia with increased glucose

Answer 1

Answer:

B. Neutrophilic Pleocytosis, decreased glucose and increased protein

Cerebrospinal Fluid (CSF) Analysis in Acute Bacterial Meningitis

• Appearance: The CSF is typically turbid or purulent (cloudy) due to the presence of high numbers of white blood cells and bacteria.
• Opening Pressure: Elevated opening pressure is commonly observed, often exceeding 200–300 mm H2O.
• White Blood Cell (WBC) Count: There is a marked pleocytosis, usually ranging from 1,000 to 10,000 cells/µL, with a distinct neutrophilic predominance (often >80% polymorphonuclear leukocytes).
• Glucose Concentration: A hallmark finding is hypoglycorrhachia, where CSF glucose levels are significantly reduced, typically <40 mg/dL or a CSF-to-serum glucose ratio of <0.4.
• Protein Concentration: CSF protein levels are consistently elevated, frequently ranging from 100 to 500 mg/dL, reflecting increased blood-brain barrier permeability.
• Gram Stain and Culture: Gram stain is positive in approximately 60–90% of untreated cases, and culture confirms the causative organism (e.g., Streptococcus pneumoniae, Neisseria meningitidis, or Haemophilus influenzae).