If head imaging reveals a space-occupying lesion, what should be done before LP?

• A. Proceed with LP
• B. Defer LP
• C. Perform LP after antibiotics
• D. Perform LP with imaging guidance

Answer: (B)

When imaging shows a space-occupying lesion, intracranial pressure is likely elevated. A lumbar puncture lowers CSF pressure in the spine, which can create a pressure gradient that pulls brain tissue toward the foramen magnum, risking brain herniation. This is why LP is contraindicated in the presence of a mass effect. The safest course is to defer LP and involve neurosurgery to address the lesion and reduce ICP as needed before considering any LP. If meningitis is still a concern, treat empirically according to clinical judgment, but do not perform LP until it’s safe. Imaging guidance cannot overcome the fundamental risk posed by a mass lesion with raised ICP.