On the Shoulders of Giants
The Canadian CT Head Rule was 100% sensitive for ruling out clinically important brain injury. It had higher specificity than the New Orleans Criteria, which meant fewer people would need a CT scan by using the Canadian rule.
Use your head
This was a prospective study of 3121 patients with head injury. The Canadian CT Head Rule was derived in this study and consisted of 5 high-risk components:
- failure to reach GCS of 15 within 2 h,
- suspected open skull fracture,
- any sign of basal skull fracture,
- vomiting ≥2 episodes,
- or age >65 years
And two medium-risk components:
- amnesia before impact >30 min
- and dangerous mechanism of injury
If all were negative, the sensitivity for clinically important brain injury or need for neurosurgery was 100%. If the high risk features were used, only 32% would need CT.
The CCHR was subsequently validated and found to have 100% sensitivity. A similar rule is the New Orleans Criteria, which was also 100% sensitive but less specific, meaning many more people would not "rule out" with the New Orleans rule and would need CT.
The Canadian CT Head Rule for patients with minor head injury. Lancet. 2001 May 5;357(9266):1391-6.