Who does the Canadian CT Head Rule apply to?

Adults (age ≥16) with a minor head injury defined as blunt trauma resulting in witnessed loss of consciousness, definite amnesia, or witnessed disorientation, with a GCS of 13–15 on initial assessment.

What are the exclusion criteria?

The rule does NOT apply to: GCS <13, age <16, patients on warfarin or bleeding disorders, an obvious open or depressed skull fracture, or a seizure after injury.

What is the difference between high-risk and medium-risk factors?

High-risk factors predict need for neurosurgical intervention (sensitivity 100% in the original study). Medium-risk factors predict any brain injury visible on CT. CT is recommended for either, but the urgency differs.

What does "failure to reach GCS 15 within 2 hours" mean?

The patient's GCS did not return to 15 within 2 hours of the injury event. This is a high-risk factor requiring CT.

Is this rule validated?

Yes. The Canadian CT Head Rule was derived and validated in a multicenter prospective study published in The Lancet (Stiell et al., 2001) and has been externally validated in multiple subsequent studies.

Can I use this for pediatric patients?

No. For patients under 16, use PECARN (Pediatric Emergency Care Applied Research Network) rules, which are specifically validated for children.

Canadian CT Head Rule

Name: Canadian CT Head Rule
Availability: InStock
Author: Nham Vu

Apply the validated Canadian CT Head Rule to determine if a CT scan is needed for minor head injury patients (GCS 13–15).

Patient Criteria

Applies to adults ≥16 with minor head injury (GCS 13–15) + witnessed LOC, amnesia, or disorientation. Do not use if GCS <13, age <16, anticoagulated, open/depressed fracture, or post-injury seizure.

High Risk Neurosurgical intervention

GCS score <15 at 2 hours after injury Suspected open or depressed skull fracture Any sign of basal skull fracture (hemotympanum, "raccoon eyes", cerebrospinal fluid otorrhea/rhinorrhea, Battle's sign) Vomiting ≥2 episodes Age ≥65

Medium Risk Brain injury on CT

Amnesia before impact ≥30 minutes Dangerous mechanism (pedestrian struck by motor vehicle, occupant ejected from MV, fall from height >3 feet or 5 stairs)

Result

Select criteria above

Check any applicable boxes to see the recommendation.

Interpretation Guide

Any High-Risk Factor

CT head indicated — high risk for neurosurgical intervention. Sensitivity 100% for neurosurgical intervention in the original validation.

Medium-Risk Factor Only

CT head recommended — risk for clinically important brain injury on CT even without immediate neurosurgical need.

No Criteria Met (GCS 15 at assessment)

CT not required per rule. Clinically important brain injury is unlikely. Discharge with head injury instructions at clinician discretion.

Reference: Stiell IG et al. The Canadian CT Head Rule for patients with minor head injury. Lancet. 2001;357(9266):1391–1396. This tool is for educational use only and does not constitute medical advice.

Summary

Apply the validated Canadian CT Head Rule to determine if a CT scan is needed for minor head injury patients (GCS 13–15).

How it works

Confirm the patient has a minor head injury with a GCS of 13–15.
Verify the rule applies: witnessed loss of consciousness, definite amnesia, or witnessed disorientation.
Check each of the five high-risk criteria (any = CT required for neurosurgical intervention risk).
If no high-risk criteria, check the two medium-risk criteria (any = CT recommended for brain injury risk).
A result of "CT Not Required" assumes GCS 15 at time of assessment with no criteria met.
Always apply clinical judgment; this tool supplements, not replaces, physician decision-making.

Use cases

Emergency department triage of minor head injury patients.
Reducing unnecessary CT scans in low-risk presentations.
Identifying high-risk features that warrant immediate imaging.
Standardizing head injury assessment across clinical teams.
Medical education on evidence-based head injury management.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu