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Suspected subarachnoid haemorrhage after normal CT — SCE Acute Medicine MCQ

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ModerateAcute Neurological PresentationsSuspected subarachnoid haemorrhage after normal CTSCE Acute Medicine

A 64-year-old woman presents with thunderclap headache that peaked instantly while gardening. CT head at four hours is normal and neurological examination is normal. She is still photophobic and has neck stiffness. What is the most appropriate investigation?

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Correct answer: D — Lumbar puncture for xanthochromia at least 12 hours after headache onset

A normal CT does not fully exclude subarachnoid haemorrhage when clinical suspicion remains, and LP timed after 12 hours can assess xanthochromia. Discharge is unsafe with thunderclap headache and meningism. D-dimer has no role in excluding SAH. The teaching point is that onset kinetics matter: instant maximal headache is a red flag even with normal early imaging.

Reference: NICE CKS subarachnoid haemorrhage, RCP stroke guideline