High-risk criteria (for neurosurgical intervention)
Medium-risk criteria (for brain injury on CT)
How it's calculated
If any high-risk criterion is present, CT is recommended to detect injury needing neurosurgical intervention. If no high-risk but any medium-risk criterion is present, CT is recommended to detect clinically important brain injury. If none are present, CT can be omitted based on this rule.
Criteria
| Tier | Criteria |
|---|---|
| High risk | GCS<15 at 2h, open/depressed skull fracture, basal skull fracture signs, ≥2 vomiting episodes, age≥65 |
| Medium risk | Amnesia before impact ≥30 min, dangerous mechanism |
Clinical use
- Applies only to patients with GCS 13-15 after head injury with loss of consciousness, definite amnesia, or witnessed disorientation — not validated for anticoagulated patients, those with seizure after injury, or patients under 16 years.
- Designed to reduce unnecessary CT scans in low-risk minor head injury while reliably identifying patients needing neurosurgical intervention or with clinically important brain injury.
- The NEXUS II and New Orleans Criteria are alternative decision instruments for the same clinical question, with different sensitivity/specificity trade-offs.
- A negative rule (no criteria met) does not eliminate all risk — clinical judgement and safety-netting advice remain important, especially with ongoing symptoms or anticoagulation.
Frequently asked questions
What is the Canadian CT Head Rule used for?
It helps decide whether a CT scan is needed after minor head injury (GCS 13-15), aiming to reduce unnecessary imaging while still identifying patients who need neurosurgical intervention or have important brain injury.
Who is this rule not validated for?
Anticoagulated patients, those with a seizure after the injury, and patients under 16 years of age are outside the validated population for this rule.
What happens if a high-risk criterion is present?
CT imaging is recommended, since high-risk criteria are associated with a meaningfully increased risk of needing neurosurgical intervention.
Is this the same as the New Orleans Criteria?
No — both are decision rules for the same clinical question (need for CT after minor head injury) but use different criteria and were derived in different populations.
References
- Stiell IG, et al. The Canadian CT Head Rule for patients with minor head injury. Lancet. 2001;357(9266):1391-1396.
- Stiell IG, et al. Comparison of the Canadian CT Head Rule and the New Orleans Criteria in patients with minor head injury. JAMA. 2005;294(12):1511-1518.