Learn EM

Canadian Head CT Rule

The Canadian Head CT Rule was originally published in 20011 and validated in 20052. There have been multiple subsequent validation studies. It was designed to determine which patients with mild traumatic brain injury (mTBI) require imaging. 

Inclusion Criteria: GCS 13-15 AND at least one of the following

  • Loss of consiousness
  • Amnesia to the traumatic event
  • Witnessed disorientation

Exclusion Criteria:

  • Age <16 years old. 
  • ANY anticoagulation (or antiplatelet agents)
  • Seizure after injury

High Risk Criteria (Yes to any of these, consider imaging. Patient at high risk. If negative, excludes need for neurosurgical intervention)

  • GCS <15 at 2 hours post injury
  • Suspected open or depressed skull fracture
  • Any signs of basilar skull fracture (hemotympanum, racoon eyes, battle’s sign, CSF otorrhea or rhinorrhea)
  • >2 episodes of vomiting
  • Age >65

Medium Risk Criteria (Yes to any of these, consider imaging. Patient at medium risk for clinically important” brain injury. If negative, excludes positive CT findings usually resulting in admission, but not intervention)

  • Retrograde amnesia to the event > 30 minutes
  • “Dangerous” mechanism (Pedestrian struck by vehicle, ejected from vehicle, fall from >3 feet or >5 stairs)

Take Home Points: 

  • Failing the rule means the medical provider should use his/her judgement to determine the need for imaging. It is not mandatory. 
  • The rule was created and validated in Canada.1,2 It has also been validated once in the US.3
  • Interestingly, a retrospective application of the rule to a UK population found it would have increased the number of head CTs ordered.4
  • There is debate about the need to identify all injuries vs clinically important injuries requiring intervention. 

MDCalc has a free calculator for this rule here.


  1. Stiell IG, Wells GA, Vandemheen K, et al. The Canadian CT Head Rule for patients with minor head injury. Lancet. 2001;357(9266):1391-1396. PubMed
  2. Stiell IG, Clement CM, Rowe BH, et al. Comparison of the Canadian CT Head Rule and the New Orleans Criteria in patients with minor head injury. JAMA. 2005;294(12):1511-1518. PubMed
  3. Papa L, Stiell IG, Clement CM, et al. Performance of the Canadian CT Head Rule and the New Orleans Criteria for predicting any traumatic intracranial injury on computed tomography in a United States Level I trauma center. Acad Emerg Med. 2012;19(1):2-10. PubMed
  4. Boyle A, Santarius L, Maimaris C. Evaluation of the impact of the Canadian CT head rule on British practice. Emerg Med J. 2004;21(4):426-428. PubMed
  5. Runde, Daniel, Calculated Decisions,Canadian CT Head Injury/Trauma Rule, EB Medicine. Sept, 2012. Link
  6. Canadian CT Head Injury/Trauma Rule, MDCalc

Leave A Comment