Point-of-Care Guides

Identifying Patients with Headache Who Are at Risk of Subarachnoid Hemorrhage


Am Fam Physician. 2018 Aug 15;98(4):256-257.

Author disclosure: No relevant financial affiliations.

Clinical Question

When is urgent imaging warranted in patients presenting with new nontraumatic headache and normal findings on a neurologic examination?

Evidence Summary

At least one-half of adults worldwide have a headache at least once within any given year.1 A study of more than 9,000 physician visits for headaches from 1999 to 2010 found trends toward increased use of imaging during the evaluation.2 Physicians justify the use of imaging to avoid missing a potentially life-threatening intracranial pathology such as a subarachnoid hemorrhage (SAH).

The incidence of hospital admissions because of SAH has remained stable over the past 30 years and is estimated to be 7.2 to 9 per 100,000 person-years.3 In a series of 1,507 patients diagnosed with SAH, 5.4% (95% confidence interval [CI], 4.3% to 6.6%) had a missed diagnosis at initial presentation to the emergency department.4 The risk was higher in patients who presented with a low acuity of symptoms (odds ratio = 2.7) and in patients who presented to a nonacademic hospital, regardless of the hospital's emergency department volume (odds ratio = 2.1).

A meta-analysis of 22 studies revealed that a history of neck pain (positive likelihood ratio [LR+] = 4.1) and the physical examination finding of neck stiffness (LR+ = 6.6) significantly increase the likelihood of SAH.5 Noncontrast computed tomography within six hours of headache onset was the most accurate test for SAH (LR+ = 230, negative likelihood ratio [LR–] = 0.01). Noncontrast head computed tomography after six hours also demonstrated good accuracy in ruling out SAH when normal (LR– = 0.07). Cerebrospinal fluid analysis to evaluate for red blood cells or xanthochromia had a much lower diagnostic accuracy than imaging.

The Ottawa SAH clinical decision rule (https://www.mdcalc.com/ottawa-subarachnoid-hemorrhage-sah-rule-headache-evaluation) was created to determine when imaging is warranted in persons 15 years and older with new severe headache, peaking within one

Address correspondence to Neelima Kale, PhD, MD, MBA, FAAFP, at neelima.kale@utsouthwestern.edu. Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


show all references

1. Atlas of Headache Disorders and Resources in the World. Geneva, Switzerland: World Health Organization; 2011....

2. Mafi JN, Edwards ST, Pedersen NP, Davis RB, McCarthy EP, Landon BE. Trends in the ambulatory management of headache: analysis of NAMCS and NHAMCS data 1999–2010. J Gen Intern Med. 2015;30(5):548–555.

3. Rincon F, Rossenwasser RH, Dumont A. The epidemiology of admissions of nontraumatic subarachnoid hemorrhage in the United States. Neurosurgery. 2013;73(2):217–222.

4. Vermeulen MJ, Schull MJ. Missed diagnosis of subarachnoid hemorrhage in the emergency department. Stroke. 2007;38(4):1216–1221.

5. Carpenter CR, Hussain AM, Ward MJ, et al. Spontaneous subarachnoid hemorrhage: a systematic review and meta-analysis describing the diagnostic accuracy of history, physical examination, imaging, and lumbar puncture with an exploration of test thresholds. Acad Emerg Med. 2016;23(9):963–1003.

6. Perry JJ, Stiell IG, Sivilotti ML, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013;310(12):1248–1255.

7. Bellolio MF, Hess EP, Gilani WI, et al. External validation of the Ottawa subarachnoid hemorrhage clinical decision rule in patients with acute headache. Am J Emerg Med. 2015;33(2):244–249.

8. Kimura A, Kobayashi K, Yamaguchi H, et al. New clinical decision rule to exclude subarachnoid haemorrhage for acute headache: a prospective multicentre observational study. BMJ Open. 2016;6(9):e010999.

This guide is one in a series that offers evidence-based tools to assist family physicians in improving their decision making at the point of care.

This series is coordinated by Mark H. Ebell, MD, MS, Deputy Editor for Evidence-Based Medicine.

A collection of Point-of-Care Guides published in AFP is available at https://www.aafp.org/afp/poc.



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