emergency clinicians do not rule in migraine or other benign causes of headache. unless the headache is congruent to an established pattern for that patient, the history and physical specifically targets these 13 conditions.
subarachnoid hemorrhage: family history, PCKD, known berry aneurysm, sudden and maximal intensity at onset, posterior location
intracerebral hemorrhage: trauma, coagulopathy, decreased level of consciousness, hypertension
CNS infection: fever, immunocompromise, CNS instrumentation, recent head/face infection, meningismus
increased intracranial pressure: slowly progressive, cancer history, worse in morning, worse with head in dependent position, papilledema
carbon monoxide toxicity: contacts with similar illness, locationality (worse at home or at work)
acute angle closure glaucoma: unilateral anterior location, precipitated by darkness, change in vision, red eye
temporal (giant cell) arteritis: elderly, temporal location, jaw claudication, shoulder girdle symptoms
cervical artery dissection: unilateral pain involving neck/face, trauma history
cerebral venous sinus thrombosis: thrombophilia, neurologic signs/symptoms in non-arterial distribution, eyelid edema, proptosis
hypertensive encephalopathy: altered mentation, marked hypertension, improves with antihypertensive therapy
ENT/dental infection: ear, sinus, dental findings
idiopathic intracranial hypertension: young overweight female, hormone use, vision changes
preeclampsia: late pregnancy or postpartum
Ottawa SAH Rule / ACEP Headache Clinical Policy, June 2019
1. Neck pain/stiffness
2. Age ≥40
3. Witnessed LOC
4. Onset during exertion
5. Thunderclap (peak intensity at onset)
6. Limited neck flexion on exam
If one or more features present, CT. If negative CT within 6 hours of onset and neuro exam normal, SAH ruled out. Otherwise CT angio or LP may be used as second test.