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Canadian CT Head Rule

Identifies adults with minor head injury who need CT imaging

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Why use it

Identifies patients who can safely avoid head CT, reducing radiation exposure, cost, and ED crowding. High sensitivity for neurosurgical lesions (100%) and for any clinically important CT finding (98.4%). Validated in multiple prospective studies.

About

The Canadian CT Head Rule (CCHR) identifies adults with minor head injury who require CT imaging to detect clinically important brain injury or neurosurgical intervention. It uses 5 high-risk factors (for neurosurgical intervention) and 2 medium-risk factors (for brain injury on CT). The rule applies ONLY to patients with GCS 13–15 and LOC, amnesia, or disorientation after blunt head trauma. It has high sensitivity (>98%) for both endpoints.

When to use

  • Adults (≥ 16 years) with minor head trauma
  • GCS 13–15 at time of evaluation
  • Loss of consciousness, amnesia, or disorientation after blunt head trauma
  • Decision on need for CT head in minor TBI

Formula

High-Risk Factors (for neurosurgical intervention): 1. GCS < 15 at 2 hours after injury 2. Suspected open or depressed skull fracture 3. Any sign of basal skull fracture 4. Vomiting ≥ 2 episodes 5. Age ≥ 65 years Medium-Risk Factors (for brain injury on CT): 6. Amnesia ≥ 30 minutes before impact 7. Dangerous mechanism (pedestrian vs. vehicle, ejection from MVC, fall from > 3 feet or 5 stairs)

Pearls & pitfalls

  • Rule applies ONLY to GCS 13–15, with LOC/amnesia/disorientation — NOT for GCS ≤ 12 (CT always indicated).
  • High-risk factors 1–5 predict need for NEUROSURGICAL INTERVENTION.
  • Medium-risk factors 6–7 predict CLINICALLY IMPORTANT BRAIN INJURY ON CT (may not need surgery).
  • Exclusions: age < 16, coagulopathy (warfarin, antiplatelet), seizure after injury, GCS < 13, unstable vital signs.
  • CCHR has 100% sensitivity for neurosurgical intervention and 98.4% for any clinically important CT finding.
  • The NEXUS Head CT Rule is an alternative; CCHR is more specific (requires fewer CTs).
  • Anticoagulated patients should generally be imaged regardless of CCHR score.

Next steps

Any high-risk factor present: CT recommended (highest urgency — neurosurgical intervention risk). Any medium-risk factor present: CT recommended (clinically important injury on CT). No factors present: CT NOT required — low risk of neurosurgical injury or clinically important finding.

Evidence

Stiell IG et al. (Lancet 2001) derived CCHR from 3,121 patients. Validated prospectively in 2,707 patients (JAMA 2005). Sensitivity 100% for neurosurgical intervention; 98.4% for any clinically important CT finding. Implementation reduces CT use by ~32% vs. universal CT.

References

  1. Stiell IG et al. The Canadian CT Head Rule for patients with minor head injury. Lancet. 2001;357(9266):1391-1396. — link
  2. 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. — link