Canadian CT head rule

Last revised by Yaïr Glick on 3 Feb 2022

The Canadian CT head rule (CCTHR) is a validated clinical decision rule to determine the need for CT head in adult emergency department patients with minor head injuries.

Inclusion criteria

Patient has suffered minor head trauma with resultant:

  • loss of consciousness
  • GCS 13-15
  • confusion
  • amnesia after the event

Exclusion criteria

  • anticoagulant medication or bleeding disorder
  • age <16 years
  • seizure

Risk factors

The initial study was carried out in 10 Canadian emergency departments amongst 3121 patients. Five high risk factors and two medium risk factors were identified to predict the need for subsequent neurosurgical intervention 1.

High risk factors

Medium risk factors

  • amnesia post event >30 min
  • dangerous mechanism of injury
    • pedestrian struck by motor vehicle
    • occupant ejected from motor vehicle
    • fall from >3 feet or 5 stairs


If the patient does not have any of the risk factors identified by the CCTHR then the CT head is deemed unnecessary. If any of the above risk factors are identified then a CT head should be obtained.

Several studies have found the CCTHR to be highly sensitive in identifying injuries requiring neurosurgical intervention (80-100%) 1-5, with varying degrees of specificity (49.6-80.7%) 1-5.

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