EM · Red-flag headache
Red-flag headache (approach)
Also known as Dangerous headache · Secondary headache · Worst headache of my life
The red-flag headache approach — the structured identification of the dangerous secondary causes of the headache (the SNNOOPS/SNNOPT10 mnemonic); the thunderclap (the SAH), the fever and the neck stiffness (the meningitis), the age over 50 (the giant cell arteritis), the papilloedema (the idiopathic intracranial hypertension or the tumour), the positional (the low-CSF-pressure or the venous sinus thrombosis), the visual change (the angle-closure glaucoma); the diagnostic pathway (the CT, the LP, the ESR, the CRP); and the management of the specific cause. ACEM-primary, globally tagged.
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Red flags
- The thunderclap headache (the maximal intensity within seconds to minutes) is a subarachnoid haemorrhage until proven otherwise
- The fever and the neck stiffness is a bacterial meningitis — the ceftriaxone 2 g IV before the CT or the LP
- The new headache in the over-50-year-old is a giant cell arteritis until the ESR and the CRP are checked
- The papilloedema and the positional headache may indicate the venous sinus thrombosis or the idiopathic intracranial hypertension
Meet the patient
A 45-year-old woman grips the triage desk at 7 pm: a headache that hit "like a hammer" at the back of her head while hanging washing, maximal within thirty seconds, the worst of her life, with neck stiffness and a single vomit. GCS 15, afebrile, no focal deficit, fundi normal. She has a history of migraine.[3][5]
The migraine history is the decoy that buries more subarachnoid haemorrhages than any other detail in emergency medicine. The one question that decides her next hour — and every red-flag headache you will ever see — is this: does any SNNOOP10 flag light up? Hers lights up at O, onset sudden. Hold that question and the rest of this topic is the structured answer to it.[3][5]
References15ShowHide
- [1]García-Azorín D, Monje MHG, González-García N, et al. Presence of red flags in patients with cerebral venous sinus thrombosis admitted to the emergency department because of headache: A STROBE compliant cohort-study Medicine (Baltimore), 2020.PMID 32702831
- [2]Anand J, Pawlas N, Schetz D, Kot J Management of acute intoxication with carbon monoxide - Polish Medical Society, Section of Clinical Toxicology position statement. Int J Occup Med Environ Health, 2025.PMID 41185922
- [3]Perry JJ, Stiell IG, Sivilotti ML, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache JAMA, 2013.PMID 24065011
- [4]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, 2011.PMID 21768192
- [5]van Gijn J Slip-ups in diagnosis of subarachnoid haemorrhage Lancet, 1997.PMID 9167456
- [6]Tunkel AR, Hartman BJ, Kaplan SL, et al. Practice guidelines for the management of bacterial meningitis Clin Infect Dis, 2004.PMID 15494903
- [7]Rajasekaran S, Vanderpump M, Baldeweg S, et al. UK guidelines for the management of pituitary apoplexy Clin Endocrinol (Oxf), 2011.PMID 21044119
- [8]Smith SV, Friedman DI. The Idiopathic Intracranial Hypertension Treatment Trial: A Review of the Outcomes Headache, 2017.PMID 28758206
- [9]Fam D, Saposnik G Critical care management of cerebral venous thrombosis Curr Opin Crit Care, 2016.PMID 26645556
- [10]Dejaco C, Ramiro S, Bond M, et al. EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice: 2023 update Ann Rheum Dis, 2024.PMID 37550004
- [11]Viera AJ, Antono B. Acute Headache in Adults: A Diagnostic Approach Am Fam Physician, 2022.PMID 36126007
- [12]Ducros A. Reversible cerebral vasoconstriction syndrome Lancet Neurol, 2012.PMID 22995694
- [13]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, 1989.PMID 2496789
- [14]Currier CE, Bays AM, Thomason JL Normal inflammatory markers in giant cell arteritis: a diagnostic blind spot. Rheumatol Int, 2025.PMID 40682608
- [15]Dasgupta B, Borg FA, Hassan N, et al. BSR and BHPR guidelines for the management of giant cell arteritis. Rheumatology (Oxford), 2010.PMID 20371504