Canadian CT Head Rule for Head Trauma

High-Risk Criteria

The American College of Radiology recommends a CT scan for patients with head trauma who have a GCS score of 13-15 and any one of the following high-risk criteria: GCS <15 at 2 hours post-injury, suspected open or depressed skull fracture, signs of basilar skull fracture, vomiting ≥2 episodes, age ≥65 years, amnesia >30 minutes before impact, or dangerous mechanism of injury 1, 2
A GCS score <15 at 2 hours after injury is a high-risk criterion for neurosurgical intervention in patients with head trauma 2
Suspected open or depressed skull fracture is a high-risk criterion for neurosurgical intervention in patients with head trauma 2
Any sign of basilar skull fracture is a high-risk criterion for neurosurgical intervention in patients with head trauma 2
Vomiting ≥2 episodes is a high-risk criterion for neurosurgical intervention in patients with head trauma 2
Age ≥65 years is a high-risk criterion for neurosurgical intervention in patients with head trauma 2

Amnesia before impact >30 minutes is a medium-risk criterion for brain injury detection in patients with head trauma 2
A dangerous mechanism of injury, such as pedestrian struck by vehicle, occupant ejected from vehicle, or fall from height >3 feet or 5 stairs, is a medium-risk criterion for brain injury detection in patients with head trauma 2, 3

The Canadian CT Head Rule was originally developed for patients with GCS 13-15 with witnessed loss of consciousness, amnesia, or disorientation, and has been validated to be 100% sensitive for detecting injuries requiring neurosurgical intervention 4, 5
The Canadian CT Head Rule offers better specificity (37.2%-39.7%) compared to the New Orleans Criteria (3.0%-5.6%) for detecting traumatic brain injury 4
The Canadian CT Head Rule could potentially reduce CT scan usage by approximately 37%, while the New Orleans Criteria would only reduce scans by about 3% 5

The American College of Emergency Physicians recommends CT for all patients with coagulopathy, including those on anticoagulant medications, regardless of other criteria 1, 6
Anticoagulated patients have a significantly higher risk of intracranial hemorrhage (3.9%) compared to non-anticoagulated patients (1.5%) 6

The American College of Radiology recommends assessing GCS score and checking for high-risk criteria, which requires immediate CT if any are present 2
For patients on anticoagulants, the American College of Emergency Physicians recommends proceeding directly to CT regardless of other criteria 6
For elderly patients (≥65 years), the American College of Radiology recommends maintaining a lower threshold for CT as age is a strong independent predictor of intracranial injury 3

The Canadian CT Head Rule demonstrated 100% sensitivity for neurosurgical intervention with specificity of 60-76% in validation studies 2
The Canadian CT Head Rule has lower sensitivity (83.4%-87.2%) for detecting all traumatic intracranial findings, and clinical judgment should supplement the rule, especially in high-risk populations like the elderly and those on anticoagulants 2

The American College of Radiology recommends using validated clinical decision rules, such as the Canadian CT Head Rule or New Orleans Criteria, to determine which head trauma patients require CT scanning, rather than imaging all patients or relying on clinical gestalt alone 7, 8

The American College of Radiology states that head trauma severity, classified by the Glasgow Coma Scale, guides imaging decisions, with severe head trauma (GCS ≤8) requiring immediate attention 8

The American College of Radiology advises that all patients on anticoagulants or with coagulopathy require CT regardless of other criteria, due to a 3.9% risk of intracranial hemorrhage versus 1.5% in non-anticoagulated patients 9
The American College of Radiology recommends that all patients with GCS ≤12 require immediate CT, as they have substantially higher rates of positive CT findings and neurosurgical intervention needs 7, 8

The American College of Radiology suggests that CT can be safely avoided in patients who meet all of the following criteria: GCS 15 maintained throughout evaluation, no loss of consciousness or amnesia, no headache or vomiting, no physical evidence of trauma above clavicles, not on anticoagulant therapy, no dangerous mechanism of injury, and age <60-65 years, as only 10% of mild head trauma shows positive CT findings and only 1% requires neurosurgical intervention 7, 8, 9

The American College of Radiology emphasizes that adhering to validated decision rules is crucial, as recent data shows that 57% of all head CTs and 80.2% of mild trauma CTs are potentially avoidable when guidelines are not followed 7