Evidence-based decision template identifying which patients need neuroimaging before LP.
Query: Which patients need a head CT before lumbar puncture?
Summary
Patients with signs of elevated intracranial pressure (ICP) or other risk factors for brain herniation require a head CT before performing a lumbar puncture.
At-a-glance
Risk Factor
Description
Age > 60
Increased risk of intracranial lesions
Immunocompromised
Higher risk for CNS infections or mass lesions
History of CNS Disease
Prior stroke, mass, or other CNS pathology increases risk
Recent Seizure (<1 week)
Can be an indicator of increased ICP or mass effect
Altered Mental Status/Decreased Level of Consciousness
Inability to answer two consecutive questions or follow commands reliably
Focal Neurological Deficits
Lateralizing signs suggesting a mass lesion or other structural abnormality
Papilledema and Other Signs of Elevated ICP
Direct evidence of raised intracranial pressure that contraindicates immediate LP
Explanation
A head CT prior to LP is indicated when there is any concern for increased ICP or risk factors for brain herniation. According to WikEM, LP without CT is generally safe if the patient is under 60, immunocompetent, has no history of CNS disease, no recent seizures, and has a normal neurological exam . Conversely, patients who fail these criteria—such as those older than 60, immunocompromised, with a history of CNS pathology, recent seizures, altered mental status, or focal deficits—should have a head CT prior to LP. Additionally, the “TAP AS IF” mnemonic (Trauma, Age >60, Papilledema, Altered mental status, Seizure, Immunocompromised, Focal deficits) from ALiEM reinforces this approach .
This approach minimizes the risk of causing a catastrophic herniation in patients with intracranial mass effect or other structural abnormalities.