Ottawa SAH Rule — JoyShine Medical

Ottawa Subarachnoid Hemorrhage (SAH) Rule

One-way decision rule that helps rule OUT subarachnoid hemorrhage in alert, neurologically intact emergency-department adults (older than 15) presenting with a new, severe, non-traumatic headache that peaked within 1 hour; a positive result cannot rule out SAH and is not a diagnosis.

Applicability — inclusion (all must be Yes)

Alert with GCS 15 (neurologically intact)

No Yes

Age > 15 years (older than 15)

No Yes

New, severe, NON-traumatic headache

No Yes

Headache reached maximum intensity within 1 hour of onset

No Yes

Applicability — exclusion (all must be No)

New neurologic deficit

No Yes

Previous aneurysm, SAH, or brain tumor

No Yes

Recurrent identical headaches (≥ 3 episodes of the same character and intensity over ≥ 6 months)

No Yes

High-risk criteria (scored when the rule applies)

1. Age ≥ 40 years

No (absent) Yes (present)

2. Neck pain or stiffness

No (absent) Yes (present)

3. Witnessed loss of consciousness

No (absent) Yes (present)

4. Onset during exertion

No (absent) Yes (present)

5. Thunderclap headache (instantly peaking pain)

No (absent) Yes (present)

6. Limited neck flexion on examination (inability to touch chin to chest OR raise the head 8 cm off the bed if supine)

No (absent) Yes (present)