When to Order CT Head for Concussion
Non-contrast head CT is indicated in concussion patients with loss of consciousness (LOC) or post-traumatic amnesia (PTA) if ANY of the following risk factors are present: headache, vomiting, age >60 years, drug/alcohol intoxication, short-term memory deficits, trauma above the clavicle, post-traumatic seizure, GCS <15, focal neurologic deficit, or coagulopathy. 1
Clinical Decision Algorithm
The 2021 ACR Appropriateness Criteria endorses the 2008 ACEP Clinical Policy, which provides a two-tiered approach based on whether LOC or PTA occurred 2:
Patients WITH Loss of Consciousness or Post-Traumatic Amnesia (Level A)
Order CT head if one or more of these are present:
- Headache
- Vomiting
- Age >60 years
- Drug or alcohol intoxication
- Deficits in short-term memory
- Physical evidence of trauma above the clavicle
- Post-traumatic seizure
- GCS score <15
- Focal neurologic deficit
- Coagulopathy (including warfarin, though controversy exists for antiplatelet agents alone)
Patients WITHOUT Loss of Consciousness or Post-Traumatic Amnesia (Level B)
CT head should be considered if any of these are present:
- Focal neurologic deficit
- Vomiting
- Severe headache
- Age ≥65 years
- Physical signs of basilar skull fracture
- GCS score <15
- Coagulopathy
- Dangerous mechanism of injury (ejection from vehicle, pedestrian struck, fall >3 feet or 5 stairs)
Evidence Supporting This Approach
Both the New Orleans Criteria and Canadian CT Head Rule have been validated as essentially 100% sensitive for detecting injuries requiring neurosurgical intervention 2. The New Orleans Criteria prioritizes sensitivity (97.7%-99.4%) at the cost of specificity (3.0%-5.6%), while the Canadian CT Head Rule accepts lower sensitivity for non-neurosurgical findings (83.4%-87.2%) but offers better specificity (37.2%-39.7%) and reduces unnecessary imaging 2.
The ACEP approach strategically applies the more sensitive New Orleans Criteria to higher-risk patients (those with LOC/PTA) and the more specific Canadian CT Head Rule criteria to lower-risk patients (those without LOC/PTA) 2.
Key Clinical Pitfalls
Coagulopathy considerations: Most guidelines recommend CT for all head trauma patients on anticoagulation (e.g., warfarin), though controversy exists regarding antiplatelet therapy alone or minimal trauma 2. When in doubt with coagulopathy, err toward imaging.
Age thresholds differ: Note the age cutoff is >60 years for patients with LOC/PTA but ≥65 years for those without LOC/PTA 1.
Repeat imaging: In patients with normal initial CT and unchanged neurologic examination, routine repeat CT is not recommended unless neurologic deterioration occurs. The risk of delayed intracranial hemorrhage is very low (0.04%-0.3%) even in patients on anticoagulation 2.
What NOT to Order Initially
The following have no role in initial concussion evaluation 2:
- CT angiography (unless vascular injury suspected)
- MRI (not useful acutely; may have role after negative CT)
- Skull radiographs (replaced by CT)
- PET/CT, MR spectroscopy, functional MRI, or DTI
Population Specificity
These guidelines apply to patients ≥16 years of age presenting within 24 hours of injury with GCS 14-15 1. Different criteria apply to pediatric patients.