Applicable patient populations:

Head CT is not necessary if:

 

97-99% sensitive for "clinically important findings" (any intracranial traumatic finding on the CT scan in which the patient would generally be admitted to the hospital, including depressed skull fractures)
100% sensitive for identifying injuries requiring neurosurgical intervention (craniotomy, intracranial pressure monitoring, elevation of skull fracture, ventricular drainage within 30 days)

 

Canadian CT Head Rule vs New Orleans CT Head Rule: both 100% sensitive at identifying lesions requiring surgery, but for clinically significant traumatic brain injuries the CCHR has lower sensitivity (83-87%) than NOC (97-99%) but higher specificity (38% vs 4%).

 

Stiell, IG et al. Comparison of the Canadian CT Head Rule and the New Orleans Criteria in patients with minor head injury. JAMA. 2005; 294(12):1511-8. Text

Smits M et al. External validation of the Canadian CT Head Rule and the New Orleans Criteria for CT scanning in patients with minor head injury. JAMA. 2005; 294(12):1519-25.  Text

Haydel MJ et al. Indications for computed tomography in patients with minor head injury. NEJM. 2000; 343(2):100-5. Text