🧠 Canadian CT Head Rule
Decide whether CT is needed after minor head injury with the Canadian CT Head Rule.
Applies to witnessed LOC/amnesia/disorientation with GCS 13–15.
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When to use
Reduce unnecessary CT in minor head injury (GCS 13–15).
How it works
CT if any high-risk (GCS < 15 at 2 h, suspected open/depressed or basal skull fracture, ≥ 2 vomits, age ≥ 65) or medium-risk (amnesia ≥ 30 min, dangerous mechanism) factor.
Key points
- Applies to witnessed LOC/amnesia/disorientation with GCS 13–15.
- Excludes anticoagulation, seizure and age < 16.
- High-risk factors predict neurosurgical intervention.
References
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| GCS < 15 at 2 h after injury | No |
|---|---|
| Suspected open/depressed skull fracture | No |
| Sign of basal skull fracture | No |
| ≥ 2 episodes of vomiting | No |
| Age ≥ 65 | No |
| Amnesia before impact ≥ 30 min | No |
| Dangerous mechanism | No |
→CT headNot indicated by rule
- High-risk criteria：Absent.
- Medium-risk criteria：Absent.
| GCS < 15 at 2 h after injury | Yes |
|---|---|
| Suspected open/depressed skull fracture | Yes |
| Sign of basal skull fracture | Yes |
| ≥ 2 episodes of vomiting | Yes |
| Age ≥ 65 | Yes |
| Amnesia before impact ≥ 30 min | Yes |
| Dangerous mechanism | Yes |
→CT headIndicated
- High-risk criteria：Present — CT (neurosurgical risk).
- Medium-risk criteria：Present — CT (clinically important injury).
Frequently asked questions
- What is Canadian CT Head Rule?
- Decide whether CT is needed after minor head injury with the Canadian CT Head Rule.
- How is Canadian CT Head Rule calculated? What is the core formula?
- CT if any high-risk (GCS < 15 at 2 h, suspected open/depressed or basal skull fracture, ≥ 2 vomits, age ≥ 65) or medium-risk (amnesia ≥ 30 min, dangerous mechanism) factor.
- When is Canadian CT Head Rule used?
- Reduce unnecessary CT in minor head injury (GCS 13–15).
- What are the key clinical points for Canadian CT Head Rule?
- Applies to witnessed LOC/amnesia/disorientation with GCS 13–15. Excludes anticoagulation, seizure and age < 16. High-risk factors predict neurosurgical intervention.
- What are the limits and cautions when using Canadian CT Head Rule?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is Canadian CT Head Rule calculated in practice? Can you show a worked example?
- Inputs: GCS < 15 at 2 h after injury No, Suspected open/depressed skull fracture No, Sign of basal skull fracture No, ≥ 2 episodes of vomiting No, Age ≥ 65 No, Amnesia before impact ≥ 30 min No, Dangerous mechanism No → Result: CT head Not indicated by rule（High-risk criteria: Absent., Medium-risk criteria: Absent.） Inputs: GCS < 15 at 2 h after injury Yes, Suspected open/depressed skull fracture Yes, Sign of basal skull fracture Yes, ≥ 2 episodes of vomiting Yes, Age ≥ 65 Yes, Amnesia before impact ≥ 30 min Yes, Dangerous mechanism Yes → Result: CT head Indicated（High-risk criteria: Present — CT (neurosurgical risk)., Medium-risk criteria: Present — CT (clinically important injury).）