Immediate scanning criteria and the one hour and eight hour rules
Expansion
CT within 1 hour if any of
- GCS under 13 on initial assessment, or under 15 at 2 hours after the injury
- Suspected open or depressed skull fracture
- Any sign of a basal skull fracture: panda eyes, Battle’s sign, cerebrospinal fluid from the ear or nose, haemotympanum
- Post-traumatic seizure
- Focal neurological deficit
- More than one episode of vomiting
CT within 8 hours if there has been loss of consciousness or amnesia plus any of
- Age 65 or over
- Coagulopathy, including any anticoagulant or a bleeding disorder
- Dangerous mechanism: pedestrian or cyclist struck by a vehicle, ejection from a vehicle, a fall from over 1 metre or five stairs
- Retrograde amnesia of more than 30 minutes before the injury
Anticoagulated patients: CT within 8 hours of the injury regardless of any other factor, and within 1 hour if there are other indications. Delayed bleeding is the concern, so a period of observation and consideration of repeat imaging applies even after a normal scan.
Children have separate, more cautious criteria, with additional attention to a tense fontanelle, a bruise, swelling or laceration over 5 cm in an infant, and any suspicion of non-accidental injury.
CT cervical spine is considered alongside, using the Canadian C-spine rule, and in anyone with a GCS under 13, intubation, a focal deficit, or where plain films are inadequate.
The purpose of the scan is to find a lesion needing neurosurgery; a normal scan in a patient with a persisting deficit does not exclude significant brain injury.