Subarachnoid haemorrhage

Assessment (2 marks). Thunderclap headache — its most common secondary cause is SAH. She is Ottawa-rule positive (thunderclap headache, neck stiffness, age 40 or more), so SAH must be investigated.^[1][2] Diagnostic pathway (4 marks). Non-contrast CT now: within 6 hours, CT identified all 121 SAH in Perry's cohort, and in SHED had 97% sensitivity with a 0.5% post-test probability after a negative scan. If CT is negative and suspicion remains, CSF with spectrophotometry (100% vs 73% sensitive for visual inspection), or CT angiography as a reasonable alternative to LP when suspicion of an intracranial source is high.^[4][3][5][1] Immediate management if SAH confirmed (4 marks). Oral nimodipine (60 mg four-hourly reduced infarction 22 vs 33%); lower very high BP slowly with short-acting drugs (expert opinion); no tranexamic acid (ULTRA); urgent neurovascular referral for aneurysm treatment ideally within 24 h — coiling preferred when both options suit (ISAT 23.7 vs 30.6% dependency or death).^[7][6][8]