🧠 Ottawa SAH Rule (Subarachnoid Hemorrhage)
UseApply only to those meeting entry criteria, then check the six items; any positive item means SAH cannot be e…
SourcePerry JJ, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JA…
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.
Methodology · worked example, guidelines & full notes
The rule is designed to be ~100% sensitive at the cost of low specificity — it rules out, it does not rule in, so a positive result is expected in many benign headaches. (original synthesis · not guideline verbatim)
When to use
Apply only to those meeting entry criteria, then check the six items; any positive item means SAH cannot be excluded and mandates further workup (CT ± LP/CTA).
How it works
Six items: age ≥ 40, neck pain/stiffness, witnessed loss of consciousness, onset during exertion, thunderclap (instantly peaking) headache, limited neck flexion on exam. Rule positive if any item present.
Key points
- The rule is designed to be ~100% sensitive at the cost of low specificity — it rules out, it does not rule in, so a positive result is expected in many benign headaches. (original synthesis · not guideline verbatim)
- Entry criteria are strict: age ≥ 15, new severe atraumatic headache peaking within 1 hour, and a normal neurological exam.
- It does not apply to patients with neurological deficits, prior aneurysm/SAH/brain tumor, or recurrent identical headaches.
References
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Age ≥ 40 years | Yes |
|---|---|
| Neck pain or stiffness | Present |
| Witnessed loss of consciousness | Present |
| Onset during exertion | Yes |
| Thunderclap headache (instantly peaking) | Yes |
| Limited neck flexion on exam | Present |
→DeterminationCannot exclude — further workup needed
- Positive items：6 / 6
| Age ≥ 40 years | No |
|---|---|
| Neck pain or stiffness | Absent |
| Witnessed loss of consciousness | Absent |
| Onset during exertion | No |
| Thunderclap headache (instantly peaking) | No |
| Limited neck flexion on exam | Absent |
→DeterminationRule negative
- Positive items：0 / 6
Verification & sources · governance
FAQ
Frequently asked questions
- What are the limits and cautions when using Ottawa SAH Rule (Subarachnoid Hemorrhage)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- Does Ottawa SAH Rule (Subarachnoid Hemorrhage) upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is Ottawa SAH Rule (Subarachnoid Hemorrhage) calculated in practice? Can you show a worked example?
- Inputs: Age ≥ 40 years Yes, Neck pain or stiffness Present, Witnessed loss of consciousness Present, Onset during exertion Yes, Thunderclap headache (instantly peaking) Yes, Limited neck flexion on exam Present → Result: Determination Cannot exclude — further workup needed（Positive items: 6 / 6） Inputs: Age ≥ 40 years No, Neck pain or stiffness Absent, Witnessed loss of consciousness Absent, Onset during exertion No, Thunderclap headache (instantly peaking) No, Limited neck flexion on exam Absent → Result: Determination Rule negative（Positive items: 0 / 6）