CT Scan Indications for Concussion
A CT scan should be performed in patients with concussion who have any high-risk clinical features according to validated clinical decision rules, but is not indicated for all concussion patients. 1
Clinical Decision Rules for CT Scanning
The most evidence-based approach is to use validated clinical decision rules to determine which patients require CT scanning after concussion. Three major clinical decision rules have strong evidence supporting their use:
1. New Orleans Criteria (for GCS 15 only) 1
CT scan is indicated with ANY of the following:
- Headache
- Vomiting
- Age > 60 years
- Drug or alcohol intoxication
- Deficits in short-term memory
- Physical evidence of trauma above the clavicle
- Seizure
2. Canadian CT Head Rule (for GCS 13-15) 1
CT scan is indicated with ANY of:
- GCS < 15 at 2 hours after injury
- Suspected open or depressed skull fracture
- Signs of basilar skull fracture
- Vomiting ≥ 2 episodes
- Age ≥ 65 years
- Amnesia > 30 minutes
- Dangerous mechanism of injury (ejection from vehicle, pedestrian struck, fall from > 3 feet or 5 stairs)
3. NEXUS-II Criteria 1
Similar risk factors to the above rules.
High-Risk Features Requiring Immediate CT
CT scanning should be performed immediately when any of these concerning features are present:
- Deteriorating level of consciousness
- Focal neurological deficit
- Persistent vomiting
- Severe or worsening headache
- Seizure after injury
- Signs of skull fracture (including basilar skull fracture)
- Age > 60-65 years
- Coagulopathy or anticoagulant use
- Dangerous mechanism of injury
- Drug or alcohol intoxication
When CT Is Not Indicated
If a patient meets none of the criteria in the validated clinical decision rules, CT scanning can be safely avoided 1. These rules have demonstrated sensitivity of 97-100% for detecting clinically significant intracranial injuries requiring neurosurgical intervention 1.
Follow-up Imaging Considerations
- Routine repeat CT is not recommended for patients with mild TBI and normal initial CT findings (Class III recommendation) 1
- Follow-up MRI may be indicated when:
- CT is normal but there are persistent unexplained neurologic findings
- New-onset, progressive, or worsening symptoms develop
- Symptoms persist beyond the expected recovery timeframe 1
Common Pitfalls to Avoid
Overuse of CT scanning: CT utilization for concussion increased by 35.7% from 2006 to 2011 despite decreasing injury severity 2. This exposes patients to unnecessary radiation.
Underuse in high-risk patients: Missing the clinical indicators that warrant CT scanning can lead to delayed diagnosis of intracranial hemorrhage.
Relying solely on GCS: A patient can have GCS 15 but still have significant risk factors requiring CT scanning.
Delayed presentation: Patients presenting >12 hours after injury with symptoms like vomiting have higher risk of abnormal CT findings 3.
Misinterpreting normal CT as "no injury": CT has limited sensitivity for diffuse axonal injury and non-hemorrhagic lesions 1, 4.
By following these evidence-based guidelines, clinicians can appropriately identify patients who require CT scanning after concussion while avoiding unnecessary radiation exposure in low-risk patients.