Ottawa Subarachnoid Hemorrhage (SAH) Rule for Headache Evaluation

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)

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).

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).