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Suspected subarachnoid haemorrhage after negative late CT head — MRCEM SBA MCQ

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HardProcedures, imaging and diagnosticsSuspected subarachnoid haemorrhage after negative late CT headMRCEM SBA

A 48-year-old woman develops an abrupt, severe headache at 08:00 while exercising; it reaches maximal intensity within a minute. At 19:00 she still has headache and neck stiffness. She is alert, afebrile and neurologically intact, with no papilloedema. She takes no anticoagulants, and her platelet count and coagulation results are normal. A non-contrast CT head performed at 17:30 has been reported by a consultant radiologist as showing no haemorrhage. Subarachnoid haemorrhage remains a clinical concern. What is the most appropriate next diagnostic plan?

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

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Correct answer: A — Arrange lumbar puncture from 20:00 onwards for CSF bilirubin spectrophotometry.

The headache reached maximal intensity within a minute, so subarachnoid haemorrhage remains an important possibility despite a normal neurological examination. Her CT was performed 9½ hours after onset: a negative CT obtained more than 6 hours after onset does not provide the reassurance associated with an appropriately reported early CT. NICE therefore advises considering lumbar puncture when suspicion persists. At 19:00, however, only 11 hours have elapsed. She should remain under assessment until lumbar puncture can be performed at least 12 hours after onset, with CSF assessed for elevated bilirubin by spectrophotometry. ([nice.org.uk](https://www.nice.org.uk/guidance/NG228/chapter/recommendations)) **B** selects the appropriate investigation but performs it too early for the recommended bilirubin assessment. **C** is attractive because angiography can identify an aneurysm, but NICE recommends it without delay *after subarachnoid haemorrhage is confirmed* to establish its cause; it does not replace this diagnostic step after a negative late CT. **D** does not replace the recommended lumbar puncture pathway in this presentation. **E** substitutes another non-contrast CT for the indicated CSF investigation; elapsed time does not make repeat CT the preferred next test. ([nice.org.uk](https://www.nice.org.uk/guidance/NG228/chapter/recommendations))

Reference: NICE NG228: Subarachnoid haemorrhage caused by a ruptured aneurysm — Recommendations (23 November 2022) — https://www.nice.org.uk/guidance/NG228/chapter/recommendations NICE NG228: Rationale and impact — Diagnosing a subarachnoid haemorrhage (23 November 2022) — https://www.nice.org.uk/guidance/ng228/chapter/Rationale-and-impact