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Specific clinical decision rules applied to adults and adolescents with apparent minor head injury identified groups at low risk of severe internal head injuries, potentially reducing the number of unnecessary CT scans used in this low-risk group.

For example, patients with apparent minor head injury lacking any of the features of the Canadian CT Head Rule had a probability of severe head injury of 0.31%, much lower than 7.1% for the patient group as a whole. These features were; 65 years or over; two vomiting episodes, amnesia for over 30 minutes, pedestrian struck, ejected from vehicle, fall from higher than a metre, suspected skull fracture, or Glasgow Coma Scale score less than 15 at two hours.

The findings clarify the likelihood of severe internal head injury in a large group of adults with apparent minor head injury. 2014 NICE guidelines recommend multiple criteria to assess head injury and prioritise patients for a CT scan, although differ from the specific decision rules studied here.

Why was this study needed?

Head injury is the commonest cause of death and disability in people aged 1 to 40 years in the UK. Each year, 1.4 million people attend emergency departments in England and Wales with a recent head injury and about 200,000 people are admitted to hospital. The incidence of death from head injury is however low, with as few as 0.2% of all patients attending emergency departments with a head injury dying as a result of this injury. Most people with minor head injuries have no lasting effects and need no specific treatment.

A significant minority, 7.1% in this study, have severe internal head injuries requiring urgent treatment. CT scans, are widely used to detect acute brain injury, but scanning everyone is inefficient, costly and needlessly exposes many people to the radiation used in the scan. They also can’t assure against risk of developing longer term physical, psychological or cognitive problems.

Clinical decision rules have therefore been developed to help doctors identify people most in need of a CT head scan and appear in 2014 NICE guidance.

This review looked into the ability of different clinical decision rules to identify serious head trauma in people presenting with minor head injuries. The clinical decision rule was compared against a reference standard, either neuroimaging or follow-up evaluation.

What did this study do?

This systematic review included 14 studies from eight countries (US, Japan, Korea and from continental Europe) including 23,079 adults and adolescents with minor head trauma, defined as a Glasgow Coma Scale (GCS) of 13 to 15, where 15 is completely alert.

The review was carried out to a high standard, assessed risk of bias and excluded the lowest quality study. However, none of the studies were based in the UK so the precise estimate of severe internal head injury in those with apparent minor head injury (7.1%) may differ from that in the UK.

What did it find?

  • The occurrence of severe internal head injuries in all those with apparent minor head trauma was 7.1% (95% confidence interval [CI] 6.8% to 7.4%). Prevalence of fatal injuries or needing brain surgery was 0.9% (95% CI 0.78% to 1.0%).
  • Those with apparent minor head injuries lacking any of the features of the Canadian CT Head Rule (see Definitions) had a probability of severe internal head injury of 0.31%, much lower than 7.1% for the group as a whole. Absence of any of the New Orleans Criteria gave a similar probability of 0.6%.
  • The risk factors most strongly associated with severe internal head injury were: skull fracture (likelihood ratio [LR] 16, 95% CI 3.1 to 59); GCS score of 13 (LR 4.9, 95% CI 2.8 to 8.5); two or more vomiting episodes (LR 3.6, 95% CI 3.1 to 4.1); any decline in GCS score (LR range 3.4 to 16), and pedestrians struck by motor vehicles (LR range, 3.0 to 4.3).
  • The criteria of pedestrians struck by motor vehicles alone (LR of 3.0 to 4.3) was linked to 19-25% probability of severe internal head injury.

What does current guidance say on this issue?

2014 NICE guidance on head injury assessment and early management provides a list of risk factors necessitating a CT head scan. This includes clinical judgement as well as similar criteria to those investigated in this review, although not identical.

What are the implications?

For assessing people with minor head trauma, increased adoption of clinical decision rules such as the Canadian Head CT Rule or the New Orleans Criteria may help improve clinicians’ ability to prioritise CT scans. However, no single factor or rule can completely exclude the likelihood of traumatic brain injury, or replace clinical judgement and repeated assessment. The review’s findings are broadly in line with 2014 NICE guidance to use multiple criteria to assess likelihood of severe brain injury, although these specific decision rules are not mentioned.


Citation and Funding

Easter JS, Haukoos JS, Meehan WP, et al. Will Neuroimaging Reveal a Severe Intracranial Injury in This Adult With Minor Head Trauma? The Rational Clinical Examination Systematic Review. JAMA. 2015;314(24):2672-81.

This work was supported in part by grants K12 HS019464-01, Physician Scientist Award (Dr Easter), and K02 HS017526, an Independent Scientist Award (Dr Haukoos), both from the Agency for Healthcare Research and Quality, R01AI106057 from the National Institute of Allergy and Infectious Diseases (Dr Haukoos), the National Football League Players Association (Dr Meehan), and the National Hockey League Alumni Association through the Corey C. Griffin Pro-Am Tournament (Dr Meehan).



Haydel MJ, Preston CA,Mills TJ, et al. Indications for computed tomography in patients with minor head injury. N Engl J Med. 2000;343(2):100-105.

NHS Choices. Concussion – complications. Leeds: NHS Choices; 2016.

NHS Choices. Severe head injury. Leeds: NHS Choices; 2016.

NICE. Head injury: assessment and early management. CG176. London: National Institute for Health and Care Excellence; 2014.

Stiell IG,Wells GA, Vandemheen K, et al. The Canadian CT Head Rule for patients with minor head injury. The Lancet. 2001;357(9266):1391-1396.

Teasdale G, Jennett B. Assessment of coma and impaired consciousness: A practical scale. The Lancet. 1974;2(7872):81–4.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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The Glasgow Coma Scale (GCS) is used to assess the severity of head injuries based on the state of consciousness of a person. It assigns the best eye opening, verbal response, and motor scores up to a total of 3-15 points, where three is least conscious and 15 is totally alert.

Clinical decision rules included in this study:

New Orleans Criteria

  • Older than 60 years
  • Intoxication
  • Headache
  • Any vomiting
  • Seizure
  • Amnesia
  • Visible trauma above the clavicle

Canadian CT Head Rule

  • 65 years or older
  • Dangerous mechanism (pedestrian struck by vehicle, occupant ejected from vehicle, fall >1m or five stairs)
  • Vomiting more than one episode
  • Amnesia longer than 30 minutes
  • GCS score less than 15 at two hours
  • Suspected open, depressed, or basilar skull fracture

Patients without any features of the above rules are considered to be at low risk of severe intracranial injury. The decision to discharge, observe, or CT scan the patient with one or more features of a rule depends on the setting, clinician’s judgement about the likelihood of injury, patient preference, number of features present, and the particular features present.


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