Trauma & Burns
Canadian CT Head Rule (CCHR) Calculator
Decides which adults with minor head injury need a head CT, from five high-risk and two medium-risk findings.
Formula
For minor head injury (GCS 13–15 with witnessed loss of consciousness, definite amnesia or witnessed disorientation), CT is needed with any one of:
High risk (neurological intervention): GCS under 15 at 2 h; suspected open or depressed skull fracture; any sign of basal skull fracture; vomiting 2 or more episodes; age 65 or older
Medium risk (brain injury on CT): amnesia before impact over 30 minutes; dangerous mechanism
How it is used
- Derived in 3,121 adults at 10 Canadian emergency departments: the five high-risk factors were 100% sensitive for neurological intervention and would have scanned 32%; all seven were 98.4% sensitive and 49.6% specific for clinically important brain injury, scanning 54% (Stiell 2001).
- The four clinically important injuries the rule missed were small contusions needing no treatment (Stiell 2001).
- Excluded from the derivation: under 16, minimal injury, no clear trauma (primary seizure or syncope), obvious penetrating or depressed fracture, acute focal deficit, unstable vital signs, seizure before assessment, bleeding disorder or oral anticoagulant, return visits and pregnancy (Stiell 2001).
Key points
- Anticoagulants and bleeding disorders were excluded: a head injury on a blood thinner is not cleared by this rule.
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For education and exam preparation only. Follow your institution’s protocols. For education and exam preparation only. Verify results independently and follow your institution’s protocols. Not a substitute for clinical judgment.