For healthcare professionals
Canadian CT Head Rule
The Canadian CT Head Rule helps decide which adults with a minor head injury need a CT scan of the head. Any one of 7 findings calls for CT. Stiell and colleagues published it in 2001. This tool is written for clinicians and is not a diagnosis.
Patient findings
Tick each finding that applies. Nothing you enter leaves this page.
What you will see
Whether the rule calls for CT, and which findings triggered it.
Educational only, not medical advice. Not a diagnosis. Imaging decisions belong to the treating team.
Source
Stiell IG and colleagues, The Lancet 2001. The criteria are taken from the open-access (CC BY) table by Mata-Mbemba and colleagues, SpringerPlus 2016, and the definitions of basal skull fracture signs and dangerous mechanisms from Kavalci and colleagues, World Journal of Emergency Surgery 2014 (CC BY). The tests check each of the 7 findings, the age cut point and the order of high and medium risk.
Validated in
Adults with minor head injury (Glasgow Coma Scale score 13 to 15 after witnessed loss of consciousness, amnesia or confusion). Mata-Mbemba and colleagues studied 142 consecutive patients in Japan; Kavalci and colleagues studied 175 adults in Turkey, excluding patients under 18, pregnant patients and those with bleeding disorders or oral anticoagulants.
Limits
In the study by Kavalci and colleagues, the rule had a sensitivity of 76.4% and a specificity of 41.7% for intracranial injury. Patients on anticoagulants need particular care (Lee 2022). The rule does not apply to patients outside its inclusion criteria, such as non-trauma presentations or a Glasgow Coma Scale score under 13 (Sampalli 2023).
The 7 findings
CT is required for patients with minor head injury with any one of the following findings (Mata-Mbemba 2016):
High risk for neurosurgical intervention
- Glasgow Coma Scale score lower than 15 at 2 hours after injury
- Suspected open or depressed skull fracture
- Any sign of basal skull fracture: hemotympanum, "panda" eyes, cerebrospinal fluid otorrhea or Battle's sign (Kavalci 2014)
- Two or more episodes of vomiting
- Age 65 years or older
Medium risk for brain injury on CT
- Amnesia for events before impact of more than 30 minutes (Kavalci 2014)
- Dangerous mechanism: pedestrian struck by a vehicle, ejection from a vehicle, or a fall from more than 3 feet or 5 stairs (Kavalci 2014)
The original rule is by Stiell and colleagues (Stiell 2001). Lee and colleagues quote the amnesia item as more than 30 minutes (Lee 2022); one open table prints it as 30 or more minutes (Mata-Mbemba 2016).
Worked example: a 45-year-old who was briefly knocked out after falling down a flight of 8 stairs, with a Glasgow Coma Scale score of 15 and no other findings, meets the dangerous mechanism item, so the rule calls for CT (medium risk).
What the studies found
In 142 patients with mild traumatic brain injury in Japan, the number of positive Canadian rule items was linked with important CT findings (area under the curve 0.69), and it performed better than the New Orleans Criteria. Age and a Glasgow Coma Scale score under 15 at 2 hours were the strongest predictors (Mata-Mbemba 2016).
In 175 adults with minor head injury in Turkey, the rule had a sensitivity of 76.4% and a specificity of 41.7% (Kavalci 2014). In a Canadian trauma center, emergency physicians followed the rule in 87.8% of the cases where it applied (Sampalli 2023).
An Australian hospital used a tool based on the rule, with its original minimum inclusion criteria, for older people who fell in residential aged care, and reminded clinicians to be particularly wary of patients taking anticoagulants (Lee 2022).
Related calculators
To score the level of consciousness, use the Glasgow Coma Scale calculator. For stroke, see the NIH Stroke Scale calculator and the ABCD2 score. For children, see the PECARN head injury rule. For the neck, see the NEXUS C-spine criteria. For ankle and midfoot injuries, the Ottawa Ankle Rules show which need an X-ray. Other bedside scores are listed under For healthcare professionals.
Sources
- Mata-Mbemba D, Mugikura S, Nakagawa A, et al. Canadian CT head rule and New Orleans Criteria in mild traumatic brain injury: comparison at a tertiary referral hospital in Japan. Springerplus. 2016;5:176. doi:10.1186/s40064-016-1781-9. PMID 27026873. Open access (CC BY 4.0). Table 1(A): the Canadian CT Head Rule; 142 patients; area under the curve 0.69. pmc.ncbi.nlm.nih.gov/articles/PMC4766169/
- Kavalci C, Aksel G, Salt O, et al. Comparison of the Canadian CT head rule and the new orleans criteria in patients with minor head injury. World J Emerg Surg. 2014;9:31. doi:10.1186/1749-7922-9-31. PMID 24742359. Open access (CC BY). Table 1: signs of basal skull fracture and dangerous mechanisms; 175 adults; sensitivity 76.4%, specificity 41.7%. pmc.ncbi.nlm.nih.gov/articles/PMC3997198/
- Lee C, Beavers J, Pham J, Hackett L, Miller J, Buntine P. Impact of the Canadian CT head rule supplemented by the original published minimum inclusion criteria to assist emergency department clinicians' assessment of patients presenting post fall from residential aged care: a retrospective audit. BMC Geriatr. 2022;22(1):607. doi:10.1186/s12877-022-03284-0. PMID 35864470. Open access (CC BY 4.0). Five high-risk and two medium-risk factors; minor head injury definition; caution with anticoagulants. pmc.ncbi.nlm.nih.gov/articles/PMC9306092/
- Sampalli A, Kang J, Campbell SG, LeBlanc CH. Adherence to the Canadian CT Head Rule in a Nova Scotian Emergency and Trauma Center. Cureus. 2023;15(5):e39484. doi:10.7759/cureus.39484. PMID 37362496. Open access (CC BY). Adherence 87.8% where the rule applied; cases where the rule did not apply (Table 4). pmc.ncbi.nlm.nih.gov/articles/PMC10290497/
- Stiell IG, Wells GA, Vandemheen K, et al. The Canadian CT Head Rule for patients with minor head injury. Lancet. 2001;357(9266):1391-1396. doi:10.1016/S0140-6736(00)04561-X. PMID 11356436. Original paper (cited; the criteria used here are taken from Mata-Mbemba 2016 and Kavalci 2014, CC BY). doi.org/10.1016/S0140-6736(00)04561-X
Written and maintained by the uncovermyrisk.com editorial team. We do not have a medical reviewer; every claim links to its primary source above. Last reviewed: 2026-11-02. Spotted an error? See About.