🧠 Canadian CT Head Rule
UseReduce unnecessary CT in minor head injury (GCS 13–15).
StrataHigh-risk factors predict neurosurgical intervention; medium-risk factors predict clinically important brain …
LimitsExcludes anticoagulation, post-traumatic seizure and age <16 — use ot… · Dangerous mechanism and amnesia definitions must follow the original … · A negative rule supports observation strategies but does not eliminat…
SourceStiell IG, et al. Lancet 2001
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
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Methodology · worked example, guidelines & full notes
Applies to witnessed LOC/amnesia/disorientation with GCS 13–15.
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).
Verification & sources · governance
FAQ
Frequently asked questions
- Does Canadian CT Head Rule upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- 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).）