Canadian CT Head Rule Calculator (Minor Head Injury)
Apply the Canadian CT Head Rule to adults with minor head injury (GCS 13–15 with loss of consciousness, amnesia or disorientation): 5 high-risk and 2 medium-risk findings decide on CT.
How it works
For minor head injury (GCS 13–15 with LOC, amnesia or disorientation) and no exclusion: CT is required if ANY high-risk finding (GCS < 15 at 2 h, suspected open or depressed fracture, signs of basal fracture, vomiting ≥ 2, age ≥ 65) or ANY medium-risk finding (retrograde amnesia ≥ 30 min, dangerous mechanism) is present.
The Canadian CT Head Rule (Stiell et al., Lancet 2001) was derived in 3,121 adults with minor head injury. The five high-risk findings identified all patients who needed neurosurgical intervention (100% sensitivity), and adding the two medium-risk findings detected 98% of clinically important brain injuries. In head-to-head validation it was more specific than the New Orleans Criteria, so it reduces unnecessary CT scans. It does not apply to children, anticoagulated patients or people who had a seizure.
Worked example
A 40-year-old briefly lost consciousness after falling from a 2-metre ladder; GCS is 15, there is no vomiting, no sign of skull fracture and amnesia lasts only a few minutes. The fall from more than 1 m is a dangerous mechanism (medium risk), so the result is: CT head recommended — medium risk (for brain injury on CT).
Sources: Stiell IG et al. The Canadian CT Head Rule for patients with minor head injury. Lancet 2001 · Stiell IG et al. Comparison of the Canadian CT Head Rule and the New Orleans Criteria. JAMA 2005
Frequently asked questions
Who does the Canadian CT Head Rule apply to?
Adults aged 16 or over with a blunt head injury causing witnessed loss of consciousness, definite amnesia or witnessed disorientation, and a GCS of 13–15. It does not apply to people on anticoagulants, with a bleeding disorder, a seizure after injury or an obvious skull fracture.
What counts as a dangerous mechanism?
A pedestrian struck by a motor vehicle, an occupant ejected from a vehicle, or a fall from a height of more than 3 feet (about 1 metre) or five stairs.
Why is age 65 or over high risk?
Older adults have a much higher chance of intracranial bleeding after minor trauma, so the rule recommends CT for everyone aged 65 or over who meets its inclusion criteria.
Canadian CT Head Rule or NICE guidance?
NICE head injury guidance in the UK is largely built on the Canadian rule, with extra criteria such as anticoagulation. Follow your local protocol.
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Clinical decision tool for education and for use by trained clinicians alongside clinical judgement — not a diagnosis and not a substitute for medical assessment. Scores validated in specific populations may not apply to every patient.