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Suspected subarachnoid haemorrhage after a negative CT performed more than six hours after symptom onset — MRC

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HardNeurological emergenciesSuspected subarachnoid haemorrhage after a negative CT performed more than six hours after symptom onsetMRCEM SBA

A 54-year-old man develops a headache that reaches maximal intensity within seconds during sexual intercourse at 07:10. He briefly loses consciousness. At 16:15 he is alert but still has a severe headache; neurological examination and coagulation results are normal. He takes no anticoagulants. A non-contrast CT head performed at 13:50 has been reported by a radiologist as showing no haemorrhage or mass lesion. He remains clinically stable. What is the most appropriate investigation plan?

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Correct answer: B — Continue observation and arrange lumbar puncture at 19:30 with CSF bilirubin spectrophotometry.

The instantaneous headache and transient loss of consciousness sustain concern for subarachnoid haemorrhage despite a normal examination. CT was performed 6 hours 40 minutes after onset. A negative scan obtained beyond six hours does not exclude haemorrhage as reliably as an earlier scan, so NICE recommends considering lumbar puncture. ([nice.org.uk](https://www.nice.org.uk/guidance/NG228/chapter/recommendations)) At 16:15, fewer than 12 hours have elapsed since onset, making A premature for the recommended bilirubin assessment. By 19:30, 12 hours 20 minutes have elapsed; B combines appropriate observation, timing and CSF bilirubin spectrophotometry. D has the right timing, but visual inspection alone is not the specified spectrophotometric test. ([nice.org.uk](https://www.nice.org.uk/guidance/NG228/chapter/recommendations)) C is attractive because an aneurysm could explain the presentation, but NICE recommends CT angiography to identify the cause after subarachnoid haemorrhage is confirmed; it is not the recommended substitute for investigating this negative, late CT. E repeats non-contrast imaging later, rather than addressing the residual diagnostic uncertainty with lumbar puncture. If haemorrhage is confirmed, urgent discussion with a specialist neurosurgical centre is required. ([nice.org.uk](https://www.nice.org.uk/guidance/NG228/chapter/recommendations))

Reference: NICE NG228: Recommendations (23 November 2022) — https://www.nice.org.uk/guidance/NG228/chapter/recommendations NICE NG228: Rationale and impact — diagnosing subarachnoid haemorrhage (23 November 2022) — https://www.nice.org.uk/guidance/ng228/chapter/Rationale-and-impact