• The primary aim of clinical and radiological assessment is to identify those patients with clinically important brain injury and, most crucially, those with an intracranial haematoma requiring urgent neurosurgical management.

• There are an estimated 700,000 hospital attendances per annum for head injury in England and Wales. The large majority of these are classified as mild with a low risk of intracranial haematoma.  Recent UK practice has relied heavily on the use of skull radiography to triage patients with mild head injury, but sensitivity for detection of intracranial haematoma may be as low as 38%.  CT has both sensitivity and specificity close to 100% but carries a high radiation burden and major resource implications if used indiscriminately.

• A number of attempts have been made to derive clinical decision rules that can identify patients who are not at risk of a neurosurgical haematoma or other clinically important brain injury and do not require cranial imaging.  The Canadian Head CT Rule was derived from a cohort of more than 3,000 patients using a methodologically sound multivariate analysis of several risk factors.  Coagulopathy, focal neurological deficit, post-traumatic seizure, and clinically suspected open or depressed skull fracture were considered a priori indications.  Five further clinical risk factors identified 100% of patients who required neurosurgical intervention, with a further two factors identifying 98.4% with clinically important brain injury.

• At the time of publication of these Guidelines the validation study of this rule has not yet been completed and it therefore constitutes Level 2 evidence.  These Guidelines adopt the Canadian Head CT Rule as the basis for selection of patients for CT scanning, but may be subject to change as new evidence emerges.

• If CT is normal or the patient does not qualify for a CT scan and no other clinical risk factors or social factors are present, the risk of complications requiring hospital care is low enough to warrant discharge to the care of a responsible adult with head injury instructions.

• These recommendations are likely to increase the use of CT in head trauma in most UK centres.  There are implications for population radiation dose and cost, although routine CT followed by patient discharge if CT is negative may be cost-effective.  CT scanning protocols should be optimised to minimise dose, especially in children.

• Current Royal College of Surgeons Guidelines state that 24-hour availability of CT is required in all centres receiving head-injured patients.  In circumstances where, for whatever reason, CT is not promptly available, skull radiographs may still have a role.  Other local circumstances may require modification of these guidelines.

• MRI, SPECT, and transcranial Doppler US are specialised investigations in head injury whose role is still under evaluation.

• Assessment of the cervical spine including imaging if indicated (see sections K7-11) is essential in all head-injured patients. The opportunity to perform CT of the cervical spine while the patient is having a head scan should be carefully considered, especially if the patient is unconscious. Multi-slice CT scanners enable the whole cervical spine to scanned at high resolution and multiplanar reformats to be generated with relative ease. Sensitivity to fractures is superior to plain radiographs.  

• Occipital condylar fractures are uncommon, but serious injuries are associated with high-energy blunt trauma to the head and/or upper cervical spine. They are difficult to diagnose clinically although they should be suspected in any patient showing signs of lower cranial nerve palsy after injury. Demonstration on plain radiographs is extremely difficult and radiological diagnosis requires good quality CT. This region should be routinely reviewed on 'bone windows' in head-injured patients, with additional high resolution imaging if necessary.  

• The Canadian Rule was derived from a cohort that did not include children. Children have a lower risk of intracranial haematoma than adults, and it is considered safe to apply the rule to this age group. If non-accidental injury is suspected, a skull radiograph as part of a skeletal survey is required. In children 0-2 years old, CT of the head is mandatory. In addition, MRI of the brain may be required later to further document timing of the injury.  

(For non-accidental injury in children see Section M) 

• Patients with head injury who are fully orientated, have no history of loss of consciousness or amnesia nor any other clinical risk factors have a negligible risk of a clinically important brain injury and do not require imaging.

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