Subarachnoid hemorrhage (SAH) is a rare but life-threatening cause of headache. The incidence of SAH peaks in mid to late adulthood. Clinical presentation of SAH varies significantly depending on severity — from sudden onset headache without other symptoms to loss of consciousness.1 Headache may be accompanied by nausea and/or vomiting, stiff neck, photophobia, brief loss of consciousness, or focal neurological deficits such as cranial nerve palsies.1

The challenge is deciding which patients require CT scans to diagnose SAH without scanning the larger population of patients who present with migraines, tension headaches, and other benign conditions. Patients with migraines are particularly challenging because they may also present with vomiting and photophobia. However, a migraine should immediately be put to the bottom of the list of possible diagnoses in a patient who is having symptoms not previously experienced with their migraines.

Clinical decision tools such as the Ottawa SAH Rule may provide some guidance, but many unnecessary CT scans may still be performed when using this tool.2 The most important “red flag” for SAH is a peak in pain within 5 minutes of headache onset and that is different from prior headaches.

The manner of asking questions to determine if the headache is truly maximal at onset is important and part of the art of medicine. If clinicians ask “did the headache start suddenly?” they will end up ordering a lot more unnecessary head CTs than if they had asked “is the headache still getting worse?” or “how many hours did it take for the headache to reach maximum severity, or is it still getting worse?”

When a head CT scan is ordered and performed within 6 hours of headache onset, the sensitivity for SAH has been reported to be approximately 100% for all patients, which typically obviates the need for lumbar puncture (LP).3 However, an LP should be performed early if there is a clinical concern for meningitis, which can also present with sudden onset headache, or the patient has considerable risk factors for SAH (eg, family history of cerebral aneurysm). An LP should also be performed if CT is performed more than 6 hours after pain onset or is not definitive due to scanner generation or because the patient has anemia.

Management of confirmed SAH in the ED includes neurosurgical consult; elevating the head of bed to 30°; treatment with antihypertensive medications to maintaining systolic BP less than 140 mm Hg to prevent stroke; and administering nimodipine, a calcium channel blocker, to improve neurologic outcomes. Other treatment should be directed by the neurosurgeon and includes surgically clipping or coiling the aneurysm in the majority of cases. 

Brady Pregerson, MD, is an emergency physician at Tri-City Medical Center in Oceanside, California and at Scripps Coastal Urgent Care in Oceanside, California.


1. Connolly ES Jr, Rabinstein AA, Carhuapoma JR, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2012;43(6):1711-1737. doi: 10.1161/STR.0b013e3182587839

2. Perry JJ, Stiell IG, Sivilotti ML, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013;310(12):1248-55. doi: 10.1001/jama.2013.278018

3. 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;343:d4277. doi: 10.1136/bmj.d4277

This article originally appeared on Clinical Advisor