Calculators · Emergency Medicine · Criteria
Canadian CT Head Rule
Also called CCHR, CT head rule minor head injury
Which adults with minor head injury (GCS 13–15) need a CT scan.
CT head
Not required by the rule
- Risk group
- Low risk
No high- or medium-risk factor. The rule does not call for CT, provided the patient meets the inclusion criteria and none of the exclusions.
Formula and scoring
High risk: GCS <15 at 2 h, open/depressed fracture, basal skull fracture signs, vomiting ≥2, age ≥65. Medium risk: amnesia before impact >30 min, dangerous mechanism. Any factor → CT.
Exam and ward pearls
- Applies only to blunt head injury with witnessed LOC, definite amnesia or disorientation, GCS 13–15, within 24 hours.
- Age ≥65 alone mandates CT under this rule.
When not to rely on it
- Exclusions: age <16, anticoagulant use or bleeding disorder, obvious open skull injury, focal deficit, unstable vitals, seizure before assessment, pregnancy, return visit for the same injury.
- The Lancet abstract writes 'vomiting >2' and 'age >65'; the rule's own table (reproduced in CJEM 2002) uses ≥2 and ≥65, which is followed here.
Source
- Stiell IG, Wells GA, Vandemheen K, et al. The Canadian CT Head Rule for patients with minor head injury. Lancet. 2001;357(9266):1391-6. doi:10.1016/s0140-6736(00)04561-x · PMID 11356436
- Jin E, Bullard MJ. Which emergency department patients with minor head injuries require computed tomography? CJEM Journal Club. CJEM. 2002;4(3):209-11. (Reproduces Table 1 of the rule, incl. the dangerous-mechanism definition.) doi:10.1017/S1481803500006412
Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.