Ottawa Subarachnoid Hemorrhage (SAH) Rule for Headache Evaluation
Rules out SAH in patients with headache.
Jennifer Glen
Provided by
EVAL FoundationInstructions
This rule has very specific inclusion and exclusion criteria that must be followed closely for appropriate application:
- Only apply in:
- Alert patients ≥15 years old, new severe atraumatic headache, maximum intensity within 1 hour.
- Patients with headache who are neurologically intact.
- Do not use in: Patients with new neurologic deficits, prior aneurysm, prior SAH, known brain tumors, or chronic recurrent headaches (≥3 headaches of the same character and intensity for >6 months).
The Ottawa SAH Rule was intended for use in the emergency department in patients presenting with new severe atraumatic headache to rule out a subarachnoid hemorrhage.
Criteria include patients who present with headache and are neurologically intact.
- Who are alert and oriented
- Presents within 14 days of headache
- With no history of trauma or fall in the past 7 days
- Intended for use in an emergency department setting.
- The rule is 100% sensitive for SAH
- The specificity is 15% (low)
Summary
Cannot rule out SAH if one or more criteria are present.
- Age ≥40 years.
- Neck pain or stiffness.
- Witnessed loss of consciousness.
- Onset during exertion.
- Thunderclap headache (instantly peaking pain).
- Limited neck flexion on examination.
Inclusion criteria for this rule:
- Alert patients >15 years with a non‐traumatic acute headache:
- “Alert” is a GCS=15,
- “Non‐traumatic” is no direct head trauma in previous 7 days,
- “Acute” is maximal pain in <1 hour and presents within 14 days.
Exclusion criteria for this rule:
- New neurologic deficits, previous aneurysm, brain tumor or SAH.
- Patients with chronic recurrent headaches (≥3 headaches of the same character and intensity for >6 months).
All questions & possible results
InstructionsTitle not visible
Age ≥ 40
Select one option:
- Yes
- No
Neck pain or stiffness
Select one option:
- Yes
- No
Witnessed loss of consciousness
Select one option:
- Yes
- No
Onset during exertion
Select one option:
- Yes
- No
Thunderclap headache (instantly peaking pain)
Select one option:
- Yes
- No
Limited neck flexion on examination
Select one option:
- Yes
- No
Possible results
Ruled Out
This patient can be ruled out of subarachnoid hemorrhage by the Ottawa SAH Rule (the rule was 100% sensitive for SAH in its validation).
Notes
- May consider avoiding further SAH-specific workup in patients with all negative criteria.
- Patients who are ruled out for SAH may still have other causes for headache that require workup or intervention, and differential diagnosis should be broad.
Not Ruled Out
This patient cannot be ruled out of subarachnoid hemorrhage by the Ottawa SAH Rule (the rule was 100% sensitive for SAH but only 15% specific for SAH).
MANAGEMENT
- In patients with any positive criteria by the Ottawa SAH Rule (i.e., cannot rule out SAH), workup for SAH typically begins with includes noncontrast CT head. Consider lumbar puncture (LP) and/or cerebral angiography if clinical suspicion remains.
- By completing this study, the authors were also able to provide insight into the appropriate workup for patients with possible SAH. They recommend:
- Non-contrast CT scan within 6 hours of headache onset is sufficient to rule out SAH in most patients.
- If a patient is deemed to be particularly high-risk, LP should be performed.
- If there is no visual xanthochromia and tube 4 of the LP has <2,000 x 106/L, SAH is ruled out unless 'ultra high risk'.
- If the patient is 'ultra high risk,' CT angiography (CTA) can be performed to evaluate for cerebral aneurysm. Neurosurgical consultation may be particularly helpful in these 'ultra high risk' patients.
- CT angiography can be helpful in significant time delay between presentation and initial headache (e.g. headache last week).
- Neurology and neurosurgical consultation should be obtained in patients with suspected or confirmed SAH.
Note
- Consider SAH workup in patients with ANY positive criteria, but as with other rule-out decision aids, just because a patient fails the rule does not require that all patients are then evaluated for SAH, given its very low specificity.
Literature
- High risk clinical characteristics for subarachnoid haemorrhage in patients with acute headache: propspective cohort study. — Perry JJ, Stiell IG, Sivilotti ML, et al.
- Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. — Perry JJ, Stiell IG, Sivilotti ML, et al.
- External validation of the Ottawa subarachnoid hemorrhage clinical decision rule in patients with acute headache. — Bellolio MF, Hess EP, Gilani WI, et al.
- Prospective Implementation of the Ottawa Subarachnoid Hemorrhage Rule and 6-Hour Computed Tomography Rule. — Perry JJ, Sivilotti MLA, Edmond M, et al.
