The ACEP clinical policy development process was used. Articles were first classified according to the strength of evidence based on the design of the study, then graded based on six dimensions thought to be most relevant to the development of clinical guidelines. Articles were given a final question-specific level of evidence grade on the basis of a predetermined formula, taking into account design and quality of the study. The recommendations made in the policy were given a level of A, B, or C (with A being the strongest level of evidence and C being the least) according to the strength of the evidence supporting them.

Critical Questions

1. Which patients with mild TBI should have a noncontrast head CT scan in the ED?

• Level A recommendation. A noncontrast head CT is indicated in head trauma patients with loss of consciousness or posttraumatic amnesia only if one or more of the following is present: headache, vomiting, age older than 60 years, drug or alcohol intoxication, deficits in short-term memory, physical evidence of trauma above the clavicle, posttraumatic seizure, GCS score less than 15, focal neurologic deficit, or coagulopathy.
• Level B recommendation. A noncontrast head CT should be considered in head trauma patients with no loss of consciousness or posttraumatic amnesia if there is a focal neurologic deficit, vomiting, severe headache, age 65 years or older, physical signs of a basilar skull fracture, GCS score less than 15, coagulopathy, or a dangerous mechanism of injury such as ejection from a motor vehicle, a pedestrian struck, or fall from a height of greater than 3 feet or five stairs.
• Level C recommendation. None specified.

Two seminal studies have laid the foundation for prediction rules guiding neuroimaging in mild TBI: the Canadian CT Head Rule (CCHR) developed by Stiell et al.,⁹ and the New Orleans Criteria developed by Haydel et al.¹⁰ Subsequent studies have prospectively compared these two criteria sets.

In a Class I study, Smits et al. found that the New Orleans Criteria and the Canadian CT Head Rule had an equal sensitivity of essentially 100% regarding the identification of lesions requiring neurosurgical interventions.¹¹ A difference was seen in identifying acute intracranial injuries, where the New Orleans Criteria had a sensitivity of 98.3% (95% CI, 94% to 99.5%) and the Canadian CT Head Rule a sensitivity of 83.4% (95% CI, 77.7% to 87.9%). This higher sensitivity seen with the New Orleans Criteria came at the expense of specificity, with 5.6% (95% CI, 2.7% to 8.8%) for identifying intracranial injury, versus a specificity of 39.4% (95% CI, 36.0% to 42.8%) seen with the Canadian CT Head Rule. Other studies have had similar findings.^12,13