CT scans are frequently done after minor head injury to evaluate for intracranial hemorrhage. While CT scans are an excellent tool for diagnosing or ruling out this disorder, they are not without harms including radiation exposure, cost and department delays. Much of the time, CTs are negative, or find injuries for which no intervention is ever done and do not clinically affect the patient. Decision instruments may aid clinicians in determining which injuries are higher risk and require imaging and which do not.

For the purpose of this study, minor head injury was defined as patients with GCS 15, blunt head trauma within 24 hours causing LOC, amnesia or disorientation.

Clinical Question

Can a clinical decision instrument safely determine which patients with minor head injury do not need advanced imaging?


Adult patients > 18 years of age with blunt head trauma within 24 hours of presentation who had LOC, amnesia or disorientation but presented with a GCS = 15. All patients had normal neurologic examinations.


Phase 1 – 520 consecutive patients were evaluated to derive a clinical decision instrument. Phase 2 – The decision instrument was prospectively validated in the evaluation of 909 minor head trauma patients.


No Comparator Group


The presence of ANY acute traumatic intracranial lesion (subdural, epidural or parenchymal hematoma, subarachnoid hemorrhage, cerebral contusion or depressed skull fracture).


Prospective, cohort study (both for derivation and validation)


• Concurrent injuries precluding CT use
• No LOC
• Amnesia for the traumatic event
• Focal neurologic findings
• Refusal of CT

Primary Results

  • Phase 1: 520 patients presenting with minor head trauma
  • 36 (6.9%) had positive CT scans
  • A decision tool was created including 7 variables formed through logistic regression followed by recursive partitioning.
    • Headache
    • Vomiting
    • Age over 60
    • Drug or alcohol intoxication
    • Deficits in short-term memory
    • Physical evidence of trauma above the clavicles
    • Seizure

Critical Findings

  • Sensitivity 100%
    • 57 patients with positive CT scan
    • All caught by clinical decision instrument
  • Specificity 25%


  • All patients in the study had CT scan performed on initial evaluation
  • No patient with an intracranial injury was missed by the clinical decision instrument


  • Specificity is very low (25%) which means many patients will be positive by the instrument but won’t have findings on head CT
  • Unlike the Canadian rule, this rule was looking for ANY intracranial injury, not necessarily ones that are clinically significant

Author's Conclusions

“For the evaluation of patients with minor head injury, the use of CT can be safely limited to those who have certain clinical findings.”

Our Conclusions

This study derived and prospectively validated a clinical decision instrument with a very high sensitivity and very poor specificity. Unlike the Canadian Head CT instrument, it identifies ALL intracranial injuries regardless of whether they are clinically significant or not. The low specificity limits the utility of this instrument.

Subsequent studies have compared the New Orleans and Canadian head CT decision instruments (Papa 2012, Smits 2005) and found that both rules perform with 100% sensitivity for finding injuries that require neurosurgical intervention. The New Orleans criteria perform better for finding all injuries but, as a result, have much lower specificity. Smits et al estimated that adoption of the New Orleans rule would result in a modest 3% reduction in CT utilization while adoption of the Canadian head CT instrument would result in a 37.3% reduction (Smits 2005).

Potential Impact To Current Practice

This decision instrument continues to be widely used today by clinicians to help guide decision-making in minor head injuries. This article was named one of ALiEM’s Landmark Articles.

Bottom Line

The New Orleans head CT criteria allow clinicians to identify all patients who will have intracranial injuries whether they are clinically significant or not but is unlikely to produce anything more than very small reductions in CT utilization.

Read More

Papa L et al. Performance of the Canadian CT head rule and the New Orleans criteria for predicting any intracranial injury on computed tomography in a United States Level I trauma center. Acad Emerg Med 2012; 19(1): 2-10. PMID: 22251188

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. PMID: 16189365

SGEM #106: O Canada – Canadian CT Head Rule for Patients with Minor Head Injury

See also: Core EM Post on the Canadian Head CT Rule