Before every lumbar puncture many providers reactively get a CT to rule out a mass or reduce the risk of herniation, However, not every patient requires a CT.
If your patient meets the criteria below, they have a 97% negative predictive value (i.e. 97% chance of having a negative head CT.
A review of pediatric lumbar puncture and meningitis recommends not scanning any pediatric patients suspected to have bacterial meningitis, because is delays antibiotics and would be normal in the case of increased ICP.
Lumbar Puncture Checklist