Who needs a scan after a bump on the head?
Every year, millions of adults visit emergency departments after a minor head injury. Most recover fully, and fewer than 10% have a bleed or fracture visible on CT. Scanning everyone exposes many people to radiation and costs a great deal. In 2001, Ian Stiell and colleagues, who earlier developed the Ottawa ankle rules, published the Canadian CT head rule after studying more than 3,000 patients.
Who the rule applies to
Adults aged 16 or older with a minor head injury, a Glasgow Coma Scale score of 13 to 15, and witnessed loss of consciousness, definite amnesia or disorientation. It does not apply to people taking blood thinners, those with a seizure after the injury, an obvious open skull injury, unstable vital signs or pregnancy.
High-risk criteria
These predict an injury needing neurosurgery. A CT scan is needed if any is present:
- GCS score below 15 two hours after the injury.
- Suspected open or depressed skull fracture.
- Any sign of a fracture at the base of the skull: bruising around the eyes (raccoon eyes), bruising behind the ear (Battle’s sign), blood behind the eardrum, or clear fluid from the nose or ear.
- Vomiting two or more times.
- Age 65 or older.
Medium-risk criteria
These predict a brain injury visible on CT:
- Amnesia for events more than 30 minutes before the impact.
- Dangerous mechanism: a pedestrian struck by a vehicle, an occupant ejected from a vehicle, or a fall from more than 3 feet or 5 stairs.
Worked example
A 40-year-old cyclist falls down a flight of 8 stairs and is briefly knocked out. Two hours later, the GCS is 15, there has been no vomiting and no sign of skull fracture. No high-risk criterion is present, but the dangerous mechanism is a medium-risk criterion, so a CT scan is recommended.
Performance
In validation studies, the rule identified all patients who needed neurosurgery and reduced the use of CT compared with scanning everyone. It performs better than several other head injury rules, which is why many emergency departments use it.
After a minor head injury
If you go home without a scan, have someone stay with you for the first night. Return immediately for worsening headache, repeated vomiting, unusual drowsiness, confusion, slurred speech, weakness, a seizure, or clear fluid from the nose or ears. Avoid alcohol and sedating medicines for 24 hours.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.