Stiell IG, Wells GA, Vandemheen K, Clement C, et al. The Canadian CT Head Rule for patients with minor head injury. Lancet. 2001 May 5;357(9266):1391-6. PMID: 11356436


What we already know: Prior to this study, there was disagreement and lack of standardization in the use of CT in patients with minor head trauma. Though a number of studies had already been done to identify high risk features, they were not robust enough to create clinical decision rules, and guidelines were sometimes contradictory.

Why is this study important: There are over a million cases of minor head trauma treated yearly in EDs. Use of CT in these cases carry a high cost but low yield. While most of these patients can be safely discharged, a small percentage decompensate and require intervention for intracranial hematoma. The researchers sought to establish sensitive, valid, and reliable guidelines for identifying high-risk minor head trauma patients who should undergo head CT.

Brief overview of the study:

  • Prospective cohort study in 10 Canadian EDs
  • Defined minor head injury as blunt trauma with LOC, amnesia, or disorientation and GCS 13-15
  • Primary outcome: need for neurologic intervention
  • Secondary outcome: clinically important brain injury on CT
  • Patients had CT based on physician discretion
    • Those who did not had a 14 day telephone proxy outcome measure; if they did not fulfill criteria, they were recalled for a reassessment and CT

The researchers found that high risk features associated with need for neurologic intervention were: GCS <15 at 2 hours after injury; open or depressed skull fracture; sign of basal skull fracture; vomiting 2 or more times; 65 years or older. Medium risk features associated with clinically important brain injury on CT were amnesia > 30 minutes before accident or dangerous mechanism.

Limitations: There may be disagreement on the authors’ definition of clinically important brain injury, which was any acute brain finding revealed on CT that would require hospital admission and neuro follow up. They also deemed clinically unimportant lesions to include localized SAHs or isolated contusions < 5 mm diameter. Another limitation is that not all of the patients underwent CT; those that did not had follow-up 2 weeks later via a phone call, which relies on self reported data.

Take home message: The Canadian Head CT Rule is a useful clinical aid for identifying which patients with minor head trauma should undergo head CT. In subsequent studies, it was found to be 100% sensitive in identifying patients requiring neurosurgical intervention.