What goes into the Ottawa SAH rule
- Age ≥ 40 (+1)
- Neck pain or stiffness (+1)
- Witnessed loss of consciousness (+1)
- Onset during exertion (+1)
- Thunderclap headache (instantly peaking) (+1)
- Limited neck flexion on exam (+1)
How to interpret the result
- No criteria: SAH ruled out (sensitivity about 100% in derivation, specificity low)
- Any criterion: investigate (CT head; LP or CT angiography if CT is negative beyond 6 hours)
Clinical pearls
- Only for alert patients with new severe atraumatic headache peaking within 1 hour.
- A normal modern CT within 6 hours of onset makes SAH very unlikely.
- Consider other thunderclap causes: RCVS, cervical artery dissection, venous sinus thrombosis, pituitary apoplexy.
Evidence
- Perry JJ, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013;310:1248-1255.
Related workups
Related calculators
For education only. Check the inputs and the population the score was validated in before acting on it. Not a substitute for clinical judgment.