by Stacey Chamberlain
A 24-year-old woman presents with headache that began three hours prior to arrival to the ED. The patient was at rest when the headache began. The headache was not described as “thunderclap,” but it did reach maximum severity within the first 30 minutes. The headache is generalized and rated 10/10. She denies head trauma, weakness, numbness, and tingling in her extremities. She denies visual changes, changes in speech and neck pain. She has not taken anything for the headache. She does not have a family history of cerebral aneurysms or polycystic kidney disease. On physical exam, she has a normal neurologic exam and normal neck flexion.
Should you do a head CT and/or a lumbar puncture to evaluate for a sub-arachnoid hemorrhage in this patient?
Ottawa SAH Rule
Investigate if ≥1 high-risk variables present
- Age ≥ 40
- Neck pain or stiffness
- Witnessed loss of consciousness
- Onset during exertion
- Thunderclap headache (instantly peaking pain)
- Limited neck flexion on exam
A CDR to determine risk for sub-arachnoid hemorrhage (SAH) was derived and has been externally validated in a single study. The CDR’s purpose was to identify those at high risk for SAH and included those with acute non-traumatic headaches that reached maximal intensity within one hour and who had normal neurologic exams. Of note, the rule has many inclusion and exclusion criteria that the ED physician must be familiar with and was only derived for patients 16 years or older. The study authors note that the CDR is to identify patients with SAH; it is not an acute headache rule. In the validation study, of over 5,000 ED visits with acute headache, only 9% of those met inclusion criteria. Also, clinical gestalt again plays a role as the authors suggest not to apply the CDR to those who are ultra-high risk with a pre-test probability for SAH of > 50%.
The Ottawa SAH Rule was 100% sensitive but did not lead to reduction of testing vs. current practice. The authors state that the value of the Ottawa SAH Rule would be to standardize physician practice in order to avoid the relatively high rate of missed sub-arachnoid hemorrhages.
By applying the Ottawa SAH Rule, this patient is low risk and does not require further investigation for a SAH.