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Canadian CT Head Rule

Decides who needs a head CT after minor blunt head trauma — and only applies if there was LOC, amnesia, or disorientation.

CT not required
No criteria met
Valid only if the patient is genuinely in the rule's population — blunt trauma, GCS 13–15, with LOC/amnesia/disorientation
The rule does not account for anticoagulation
0pts
High risk — predicts need for neurosurgical intervention (100% sensitivity)
GCS <15 at 2 hours after injury
Suspected open or depressed skull fracture
Any sign of basal skull fracture (hemotympanum, raccoon eyes, CSF otorrhea/rhinorrhea, Battle's sign)
≥2 episodes of vomiting
Age ≥65 years
Medium risk — predicts clinically important brain injury on CT (98.4% sensitivity)
Retrograde amnesia >30 min before impact
Dangerous mechanism (pedestrian struck, ejected from vehicle, fall ≥3 ft or ≥5 stairs)
Stiell IG, et al. Lancet. 2001 · Applies ONLY to blunt head trauma with GCS 13–15 AND witnessed LOC, amnesia, or disorientation. Adults ≥16. The rule does not account for anticoagulation or antiplatelet use — lower your threshold independently in those patients.