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Lumbar puncture: when to wait, and the numbers
Three slides deal with the question that delays most lumbar punctures.
- Image first for a GCS below 13 or a fall of more than 2, focal signs, papilloedema, abnormal posture or doll's eye movements, seizures until stabilised, relative bradycardia with hypertension, or immunocompromise.
- Delay whatever the scan shows for shock or respiratory compromise, suspected meningococcal septicaemia, infection at the puncture site, or a coagulopathy.
- Platelets. A count above 40 × 10⁹/L is regarded as safe; between 20 and 40 the decision is individual and made with haematology; a rapidly falling count is a reason to wait. The 2012 encephalitis guideline used 100.
- Warfarin. INR of 1.4 or less on the day.
- Heparins. 12 hours after a prophylactic dose of low-molecular-weight heparin, 24 hours after a treatment dose; a heparin infusion stopped for 4–6 hours with an APTT ratio of 1.4 or less.
- DOACs. At least 24 hours after apixaban or rivaroxaban and 48 hours after dabigatran, when creatinine clearance is 50 mL/min or more.
- Antiplatelets. Aspirin does not delay a lumbar puncture. Clopidogrel, prasugrel and ticagrelor are stopped for 7 days before an elective one; in an emergency the decision is a balance, discussed with haematology.
- If the needle waits, aciclovir does not. Review the decision at 12 hours.
Inside
A three-question pre-test (answers at the end) · a short history, from Babylon in 323 BC to encephalitis lethargica, aciclovir and the NMDA receptor · definitions and the 2013 consortium case definition · the first six hours: lumbar puncture, CSF, PCR, MRI and EEG · herpes simplex encephalitis: presentation, aciclovir, the steroid question and relapse · other viruses and geography · infections that are not viral · autoimmune encephalitis: the Graus criteria, the antibodies, NMDA receptor encephalitis and its treatment ladder · Bickerstaff's brainstem encephalitis, with a case · over-diagnosis · intensive care, prognosis and life afterwards · ten rules to take home.
Main sources
- Granerod J, et al. Diagnosis and management of infectious encephalitis in adults: guidelines from the EAN and ESCMID. Eur J Neurol 2026. doi:10.1111/ene.70647
- Solomon T, et al. Management of suspected viral encephalitis in adults: ABN and BIA national guidelines. J Infect 2012;64:347–373.
- Dodd KC, et al. Periprocedural antithrombotic management for lumbar puncture: Association of British Neurologists clinical guideline. Pract Neurol 2018;18:436–446. doi:10.1136/practneurol-2017-001820
- McGill F, et al. The UK joint specialist societies guideline on the diagnosis and management of acute meningitis and meningococcal sepsis in immunocompetent adults. J Infect 2016;72:405–438.
- Venkatesan A, et al. Case definitions, diagnostic algorithms and priorities in encephalitis. Clin Infect Dis 2013;57:1114–1128.
- Graus F, et al. A clinical approach to diagnosis of autoimmune encephalitis. Lancet Neurol 2016;15:391–404.
The full list of 25 references is on the last slides.
Teaching material, not a protocol. Check doses and thresholds against local guidance; the antithrombotic intervals are for elective lumbar puncture. This lecture was drafted and fact-checked with AI assistance; the clinical content is the author's responsibility. Our AI policy.
