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Canadian CT Head Rule
Need for CT after minor head injury.
Canadian CT Head Rule
High risk: GCS <15 at 2 hours after injury
High risk: suspected open or depressed skull fracture
High risk: any sign of basal skull fracture
Haemotympanum, raccoon eyes, CSF oto/rhinorrhoea, Battle sign.
High risk: >=2 episodes of vomiting
High risk: age >=65 years
Medium risk: retrograde amnesia to the event >=30 minutes
Medium risk: dangerous mechanism
Pedestrian struck by vehicle, occupant ejected, or fall from >1 m / 5 stairs.
ResultCT not required by rule
No high- or medium-risk criteria; CT can reasonably be deferred in an otherwise well patient.
When to use
- Minor head injury with GCS 13-15 and witnessed loss of consciousness, amnesia, or confusion.
- Excludes anticoagulation, seizure, age <16, and unstable patients.
Formula
CT indicated if any high-risk factor (GCS <15 at 2 h, suspected open/depressed fracture, basal skull fracture sign, >=2 vomiting episodes, age >=65) OR any medium-risk factor (retrograde amnesia >=30 min, dangerous mechanism).
Pearls and pitfalls
- High-risk factors target neurosurgically important injury; medium-risk factors add sensitivity for any injury on CT.