What is the main purpose of performing a lumbar puncture in adults with suspected meningitis?

• A. To obtain cerebrospinal fluid for cell count, glucose, protein, culture; and measure opening pressure.
• B. To drain excess cerebrospinal fluid only.
• C. To measure intracranial pressure via imaging.
• D. To inject antibiotics into the cerebrospinal fluid.

Answer: (A)

When meningitis is suspected, the lumbar puncture is done mainly to obtain cerebrospinal fluid for diagnostic analysis. The CSF is examined for cell count and differential to see the pattern of inflammation, for glucose and protein levels to help distinguish bacterial from viral infections, and for Gram stain and culture to identify the causative organism and guide treatment. Measuring the opening pressure during the tap also provides information about intracranial pressure, which can influence management. Draining CSF or injecting antibiotics into the CSF are not the primary purposes of the procedure in this context; the test is about diagnosing and guiding therapy through CSF analysis and culture.