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Thunderclap headache with negative delayed CT head — SCE Acute Medicine MCQ

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HardNeurology and ophthalmologyThunderclap headache with negative delayed CT headSCE Acute Medicine

A 46-year-old presents 10 hours after a thunderclap headache. Neurological examination is normal and non-contrast head CT is reported normal. Subarachnoid haemorrhage remains clinically suspected. What is the next diagnostic step?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: D — At 12 hours, perform lumbar puncture with spectrophotometric bilirubin analysis

Explanation lettering: E = shown as A · A = shown as C · C = shown as E

D is correct. CT sensitivity declines with time; because imaging occurred more than 6 hours after onset and suspicion remains, NICE advises considering lumbar puncture. The sample should be taken at least 12 hours after symptom onset and analysed for spectrophotometric bilirubin. A overgeneralises the high sensitivity of early expert CT. B does not supply the required downstream test. C samples too early and uses unreliable visual inspection. E bypasses the recommended CT-to-LP pathway and incidental aneurysms on angiography may confuse causality. If bilirubin is detected, CT angiography is then used to identify the aneurysm.

Reference: NICE NG228: aneurysmal subarachnoid haemorrhage: https://www.nice.org.uk/guidance/ng228/chapter/Recommendations