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 patients with a GCS below 13, age under 16, oral anticoagulant use or a bleeding disorder, an obvious open or depressed skull fracture, or a seizure before the emergency assessment. The 2001 study also left out patients with no clear trauma (for example a faint that caused the fall), an acute focal neurological deficit, unstable vital signs, pregnancy, or a return visit for the same injury.

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

The five high-risk factors predict the need for neurosurgical intervention: in the 2001 study they caught all such patients (100% sensitivity) and would have meant scanning 32% of patients. The two medium-risk factors widen the net to clinically important brain injury on CT, meaning injury that would normally need admission and neurological follow-up, not every small finding. With all 7 factors the rule was 98.4% sensitive and 49.6% specific for that outcome. A finding from either group means the rule calls for a CT.

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. Stiell and colleagues derived it from 3,121 patients in 10 Canadian emergency departments (The Lancet, 2001) and then validated it prospectively in 2,707 patients in 9 departments (JAMA, 2005). In that validation it was 100% sensitive for both neurosurgical intervention and clinically important brain injury. Studies outside Canada have reported lower sensitivity in some settings.

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.

How does the Canadian CT Head Rule compare with the New Orleans Criteria?

The New Orleans Criteria cover only patients with a GCS of 15 and call for CT if any of 7 findings is present: headache, vomiting, age over 60, drug or alcohol intoxication, a persistent short-term memory deficit, visible injury above the collarbone, or a seizure. In Stiell's 2005 JAMA comparison of 1,822 patients with GCS 15, both rules caught every patient who needed neurosurgery or had clinically important brain injury. The Canadian rule was more specific (50.6% vs 12.7% for brain injury), so it led to fewer scans (52.1% vs 88.0%).

What does CT Not Required mean on this page?

It appears when none of the 7 findings is ticked. It assumes the patient fits the rule (an adult with a minor head injury and GCS 13 to 15) and has reached GCS 15 within 2 hours. A GCS still below 15 at 2 hours is itself a high-risk finding, so tick it if it applies. The result is a decision aid for clinicians and does not replace their judgment or local imaging policy.

Canadian CT Head Rule

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

The Canadian CT Head Rule says an adult with a minor head injury (witnessed loss of consciousness, amnesia or disorientation, GCS 13 to 15) needs a head CT if any of 7 findings is present.

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.

Quick answer

The Canadian CT Head Rule says an adult with a minor head injury (witnessed loss of consciousness, amnesia or disorientation, GCS 13 to 15) needs a head CT if any of 7 findings is present. Five are high risk for neurosurgery, such as age 65 or older or vomiting 2 or more times. Two are medium risk for brain injury on CT. In the 2001 study of 3,121 patients the five high-risk findings caught every patient who needed neurosurgical intervention.

Examples

Finding	Tool result
GCS under 15 at 2 hours	CT required
Vomiting 2 or more times	CT required
Age 65 or older	CT required
Pre-impact amnesia 30+ min	CT recommended
Fall over 3 ft or 5 stairs	CT recommended
None of the 7, GCS 15	CT not required

Tick each finding that applies.

Summary

The Canadian CT Head Rule is a validated clinical decision rule that identifies adult patients with minor head injury (GCS 13–15) who require a CT scan of the head. It uses five high-risk factors for neurosurgical intervention and two medium-risk factors for brain injury on CT. Patients who meet any criterion should be imaged; patients meeting none may be safely discharged without a scan in appropriate clinical contexts.

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: 2026-06-11 · Reviewed by Nham Vu