Before performing a lumbar puncture to evaluate suspected meningitis, which test must be ordered to rule out a space-occupying brain lesion?

• A. Blood culture
• B. CXR
• C. Head CT
• D. EKG

Answer: (C)

When evaluating suspected meningitis, the key safety step before a lumbar puncture is to rule out a space-occupying brain lesion that could trigger brain herniation if CSF is withdrawn. A noncontrast head CT is the test used to detect mass effect, edema, hydrocephalus, or other signs of increased intracranial pressure. If the CT shows a mass or elevated ICP, lumbar puncture is deferred and the patient is treated or further evaluated first. If the CT is normal and there are no other contraindications, you can safely proceed with lumbar puncture to analyze the CSF.

Blood cultures are obtained to identify the causative organism but don’t assess intracranial mass effect. Chest X-ray may help identify comorbid infections but isn’t used to detect brain lesions. An EKG checks heart rhythm and is not relevant to ruling out space-occupying brain lesions.