Head Injury CT Decision Rule (Canadian CT Head Rule)
Note: This document provides a structured summary of the Canadian CT Head Rule for educational and reference purposes. This rule is validated for adults ($\ge$ 16 years) with minor head injury (GCS 13-15) within 24 hours of injury who have experienced a loss of consciousness, amnesia, or disorientation. It is not a substitute for clinical judgment or local protocols.
Patient aged $\ge$ 16 years with GCS 13-15 after blunt head trauma, presenting within 24 hours of injury, and experiencing loss of consciousness, amnesia, or disorientation.
Presence of ANY of the following high-risk factors:
- GCS < 15 at 2 hours post-injury
- Suspected open or depressed skull fracture
- Any sign of basal skull fracture (hemotympanum, “raccoon eyes”, Battle’s sign, CSF leak)
- Two or more episodes of vomiting
- Age $\ge$ 65 years
Patient has one or more high-risk criteria.
Perform a head CT scan to evaluate for intracranial injury requiring neurosurgical intervention.
Patient does not have any high-risk criteria.
Presence of ANY of the following medium-risk factors:
- Amnesia before impact $\ge$ 30 minutes
- Dangerous mechanism of injury (pedestrian struck by motor vehicle, occupant ejected from motor vehicle, fall from height $\ge$ 3 feet or 5 stairs)
Patient has one or more medium-risk criteria.
Perform a head CT scan to evaluate for clinically important brain injury.
Patient does not have any medium-risk criteria.
Clinically important brain injury is unlikely. Observe patient or discharge with clear head injury instructions.
If CT performed: Manage findings (e.g., consult neurosurgery for bleed/fracture). If no CT: Observe patient or discharge with strict head injury precautions and return instructions.
