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The Canadian Head CT Rule; A Hospital Audit

John Kinyua

Coast General Hospital

Correspondence to: Dr John Kinyua, P. O BOX 90231 - 80100 Mombasa, Kenya.



Background: Minor head trauma is one of the leading cause of emergency department visits worldwide. The Canadian Head CT-scan rule (CCHR) in minor head injury is an evidence-based aid in decision making as regards to use of CT-scans to detect head injury requiring neuro-intervention. It therefore avoids wastage of resources. The objective was to compare the number of CT-scans done for minor head injury as compared to the number that would have been done if the CCHR was applied. Methods: A retrospective study was done. All patients resenting with minor head injury (GCS 13-15) were identified from the hospital registry and their files obtained. Patients not meeting the CCHR criteria excluded. Ten parameters were extracted and tabulated. Results: Forty-one patients were included with three exclusions. 89% (n=34) of the patients presented with a 2-hour GCS of 13 or more. 11% (n=4) were suspicious of base skull fractures. 23% (n=9) had signs of open fracture. Vomiting was seen in 2 patients (5%). The mean age of patients was 29 years. 2 patients (5%) reported amnesia. All the patients had a CT scan done. Fourteen patients would have required CT scans had the rule been used. Positive findings were noted in seven of the patients who qualified and in three who did not. This demonstrated a 50% positive predictive value, a negative predictive value of 89%, a sensitivity 70% and 75% specificity. Conclusion: Use of CCHR would reduce unnecessary use of CT scans in minor head injury in this setup.


Keywords: Canadian, head, CT scan, rule, minor head injury

Ann Afr Surg. 2018;15(2):57-61 DOI:

© 2018 Author. This work is licensed under the Creative Commons Attribution 4.0 International License.

Conflicts of Interest: None

Funding: None


Mild traumatic brain injury is defined as a traumatically induced physiologic disruption of brain function as manifested by one of the following: any loss of consciousness, any memory loss, altered mental status at the time of the accident, focal neurological deficits which may or may not be transient (1). Operational criteria for clinical identification include: 1 or more of the following: confusion or disorientation, loss of consciousness for 30 minutes or less, post-traumatic amnesia for less than 24 hours, and/or other transient neurological abnormalities such as focal signs, seizure, and intracranial lesion not requiring surgery; Glasgow Coma Scale score of 13–15 after 30 minutes post-injury or later upon presentation for healthcare. These manifestations of minor traumatic brain injury must not be due to drugs, alcohol, medications, caused by other injuries or treatment for other injuries (e.g. systemic injuries, facial injuries or intubation), caused by other problems (e.g. psychological trauma, language barrier or coexisting medical conditions) or caused by penetrating craniocerebral injury (1).The complexity of the definition underscores the difficulty which the physician in an emergency department faces in the management of patients presenting with mild traumatic brain injury.Reported worldwide incidence of traumatic brain incidence is 100 to 300 per 100,000 (2). This figure denotes the persons who present to medical facilities with traumatic head injury. It is estimated that more than 600 per 100,000 people who have sustained mild traumatic brain injury do not present to hospital (3).

The estimated casualty department presentation is therefore as high as 900 per 100,000 people. Extrapolating these statistics to the hospital where the audit was carried out with a catchment area of 939,000 people (4), this presents a patient population of between 939 to 2817 annually based on international incidence rates. With such a patient burden, there is need for a system to rapidly assess the patient and accurately determine whether further investigations are warranted or not. As such there exists a substantial disagreement in regards to the indication of CT scan in minor head injury (5). Unwarranted imaging leads to unnecessary wastage of resources in regards to time and money while inadequate imaging results in missed injuries with attendant morbidity and litigation risk (5).

​The Canadian CT head rule was developed as an aid to decision making in minor head injury (6). The Canadian CT head rule focuses on five high risk factors. The first factor is 2-hour GCS of less than 13 which indicates deteriorating neurological function. The next factor is a suspected open skull fracture or a base of skull fracture. This differs from an obvious fracture where the operator is able to identify an open skull fracture or base of skull fracture, a finding which obviates the need for a CT scan. The final high-risk factors are presence of vomiting which may indicate a rise in intracranial pressures (7) and patients older than 65 years. Patients older than 65 years have a risk for subdural hematoma formation in the absence of any clinical findings (8) and thus the indication for imaging. Intermediate risk factors are amnesia and a dangerous mechanism of injury. These factors when applied to study participants were shown to be sensitive for intracranial injury. The excluded f