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The Canadian CT Head Rule (CCHR) is a validated clinical decision rule used to determine the need for computed tomography (CT) scanning in adult patients with minor head injury. Developed by Dr. Ian Stiell and colleagues in 2001 through a prospective study of 3,121 patients across 10 Canadian emergency departments, this rule helps clinicians identify which minor head injury patients require CT imaging while safely reducing unnecessary scans for low-risk patients.
The rule applies to patients with head injury who have a Glasgow Coma Scale score of 13–15, witnessed loss of consciousness, definite amnesia, or witnessed disorientation, and who are at least 16 years old. It does not apply to patients on anticoagulant therapy, with obvious open skull fracture, or presenting more than 24 hours after injury.
The CCHR evaluates seven clinical criteria divided into two categories. Five high-risk criteria identify patients requiring neurosurgical intervention: GCS less than 15 at 2 hours post-injury, suspected open or depressed skull fracture, any sign of basilar skull fracture (hemotympanum, raccoon eyes, Battle sign, CSF otorrhea/rhinorrhea), two or more episodes of vomiting, and age 65 years or older. Two medium-risk criteria identify patients at risk for brain injury on CT: amnesia before impact of 30 minutes or more, and dangerous mechanism of injury (pedestrian struck, occupant ejected from vehicle, fall from height greater than 3 feet or 5 stairs).
The CCHR has demonstrated 100% sensitivity for neurosurgical intervention and 98.4% sensitivity for clinically important brain injury in the original validation. Implementation of the rule has been shown to reduce CT scanning rates by 20–30% while maintaining patient safety, representing a significant healthcare efficiency improvement.
The Canadian CT Head Rule evaluates seven criteria in two risk categories:
High-Risk Criteria (for neurosurgical intervention):
Medium-Risk Criteria (for brain injury on CT):
If any high-risk criterion is met, CT is recommended for possible neurosurgical intervention. If any medium-risk criterion is met, CT is recommended to detect brain injury. If no criteria are met, CT is not required.
If any high-risk criterion is positive, CT scanning is strongly recommended as there is a meaningful probability of neurosurgical intervention. If only medium-risk criteria are positive, CT is recommended to identify clinically important brain injury that may require observation or follow-up. If no criteria are met, the rule suggests CT is not needed, and the patient can be safely observed and discharged with appropriate head injury instructions.
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No criteria met — CT not indicated. Safe for observation and discharge with head injury precautions.
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Multiple high-risk criteria met — urgent CT required for possible neurosurgical intervention.
The Canadian CT Head Rule is a clinical decision tool that identifies which adult patients with minor head injury (GCS 13–15) require CT scanning, using seven clinical criteria divided into high-risk and medium-risk categories.
The rule applies to adults (≥16 years) with minor head injury (GCS 13–15) who have witnessed loss of consciousness, amnesia, or disorientation. It does not apply to patients on anticoagulants, with obvious open skull fractures, or presenting >24 hours after injury.
Signs include hemotympanum (blood behind the eardrum), raccoon eyes (periorbital ecchymosis), Battle sign (postauricular ecchymosis), and CSF otorrhea or rhinorrhea (clear fluid leaking from ear or nose).
The rule has 100% sensitivity for neurosurgical intervention and 98.4% sensitivity for clinically important brain injury, meaning it will identify virtually all patients who need treatment.
Yes. Studies have shown that implementing the CCHR can reduce CT scanning rates by 20–30% in minor head injury patients without missing clinically significant injuries.
Dangerous mechanisms include pedestrian struck by a motor vehicle, occupant ejected from a vehicle, or a fall from a height of 3 feet or more (or 5 or more stairs).
No. Patients on anticoagulant therapy are excluded from the rule and should generally receive CT imaging regardless of symptoms, as they have a higher risk of delayed intracranial hemorrhage.
The CCHR is more specific than the New Orleans Criteria, meaning it reduces more unnecessary CT scans while maintaining comparable sensitivity. Both rules have been validated internationally.
CT is still recommended even with GCS 15 if medium-risk criteria are met, as clinically important brain injury can be present in alert, oriented patients with dangerous mechanisms or significant amnesia.
No. The Canadian CT Head Rule was developed and validated for adults (≥16 years). The PECARN Head Injury Prediction Rule should be used for children under 18.
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