EM · Subarachnoid haemorrhage
Subarachnoid haemorrhage
Also known as Aneurysmal SAH · Subarachnoid bleed · Thunderclap headache
Subarachnoid haemorrhage in the emergency department — thunderclap headache, the Ottawa SAH Rule (derivation, validation, implementation), CT sensitivity by time (Perry, SHED), ACEP 2019, CSF spectrophotometry versus visual xanthochromia, modified Fisher grading, and initial management per the 2026 ESO/EANS/ESMINT guideline (oral nimodipine, no tranexamic acid, aneurysm treatment within 24 h, coiling when both options suit).
Checked against its sources on 8 Oct 2026
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Target exams
ACEMFRCEMABEMFRCPCCCFPEMEBEEM
Red flags
- A negative CT beyond 6 hours does not exclude SAH — overall CT sensitivity was 92.9%
- Visual inspection for xanthochromia was only 73% sensitive — use spectrophotometry
- The Ottawa SAH Rule applies only to alert, neurologically intact patients with headache peaking within 1 hour
- No routine tranexamic acid before aneurysm treatment (ULTRA)
- Oral nimodipine for every patient with aneurysmal SAH
[16]
Meet the patient
A 48-year-old woman arrives two hours after a sudden, severe headache while lifting groceries, with neck stiffness and one vomit. She is alert, GCS 15, without a focal deficit. Severe sudden-onset headache is the most common symptom of SAH, variably with meningismus and transient or prolonged loss of consciousness.[16]
References19ShowHide
- [1]Chen CY, Fuh JL Evaluating thunderclap headache. Current opinion in neurology, 2021.PMID 33661161
- [2]Sjulstad AS, Brekke OL, Alstadhaug KB Visual inspection versus spectrophotometry for xanthochromia detection in patients with sudden onset severe headache-A diagnostic accuracy study. Headache, 2025.PMID 39087907
- [3]Molyneux A, Kerr R, Stratton I, et al. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised trial. Lancet (London, England), 2002.PMID 12414200
- [4]Molyneux AJ, Kerr RS, Yu LM, et al. International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet (London, England), 2005.PMID 16139655
- [5]Molyneux AJ, Birks J, Clarke A, et al. The durability of endovascular coiling versus neurosurgical clipping of ruptured cerebral aneurysms: 18 year follow-up of the UK cohort of the International Subarachnoid Aneurysm Trial (ISAT). Lancet (London, England), 2015.PMID 25465111
- [6]Vergouwen MDI, Ramos-Pachon A, Terecoasa EO, et al. European Stroke Organisation (ESO), European Association of Neurosurgical Societies (EANS) and European Society for Minimally Invasive Neurological Therapy (ESMINT) guideline on aneurysmal subarachnoid haemorrhage. European stroke journal, 2026.PMID 42095754
- [7]Pickard JD, Murray GD, Illingworth R, et al. Effect of oral nimodipine on cerebral infarction and outcome after subarachnoid haemorrhage: British aneurysm nimodipine trial. BMJ (Clinical research ed.), 1989.PMID 2496789
- [8]Perry JJ, Sivilotti MLA, Émond M, et al. Prospective Implementation of the Ottawa Subarachnoid Hemorrhage Rule and 6-Hour Computed Tomography Rule. Stroke, 2020.PMID 31805846
- [9]Perry JJ, Sivilotti MLA, Sutherland J, et al. Validation of the Ottawa Subarachnoid Hemorrhage Rule in patients with acute headache. CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne, 2017.PMID 29133539
- [10]Trainee Emergency Research Network (TERN) Subarachnoid haemorrhage in the emergency department (SHED): a prospective, observational, multicentre cohort study. Emergency medicine journal : EMJ, 2024.PMID 39266054
- [11]Dorhout Mees SM, Rinkel GJ, Feigin VL, et al. Calcium antagonists for aneurysmal subarachnoid haemorrhage. The Cochrane database of systematic reviews, 2007.PMID 17636626
- [12]Perry JJ, Stiell IG, Sivilotti ML, et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ (Clinical research ed.), 2011.PMID 21768192
- [13]Gathier CS, van den Bergh WM, van der Jagt M, et al. Induced Hypertension for Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage: A Randomized Clinical Trial. Stroke, 2018.PMID 29158449
- [14]Gathier CS, Zijlstra IAJ, Rinkel GJE, et al. Blood pressure and the risk of rebleeding and delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage. Journal of critical care, 2022.PMID 36208555
- [15]Frontera JA, Claassen J, Schmidt JM, et al. Prediction of symptomatic vasospasm after subarachnoid hemorrhage: the modified fisher scale. Neurosurgery, 2006.PMID 16823296
- [16]Claassen J, Park S Spontaneous subarachnoid haemorrhage. Lancet (London, England), 2022.PMID 35985353
- [17]Perry JJ, Stiell IG, Sivilotti ML, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA, 2013.PMID 24065011
- [18]Vergouwen MD, Vermeulen M, van Gijn J, et al. Definition of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage as an outcome event in clinical trials and observational studies: proposal of a multidisciplinary research group. Stroke, 2010.PMID 20798370
- [19]Kirkpatrick PJ, Turner CL, Smith C, et al. Simvastatin in aneurysmal subarachnoid haemorrhage (STASH): a multicentre randomised phase 3 trial. The Lancet. Neurology, 2014.PMID 24837690