When is a Non-Contrast Head CT Indicated in a 17-Year-Old with Concussion?
A non-contrast head CT is indicated in a 17-year-old with concussion if ANY of the following risk factors are present: headache, vomiting, 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, or coagulopathy—even with loss of consciousness or post-traumatic amnesia. 1
Clinical Decision Framework
The 2021 ACR Appropriateness Criteria provides the most current guidance for patients ≥16 years of age with head trauma 1. The approach differs based on whether loss of consciousness (LOC) or post-traumatic amnesia (PTA) occurred:
For Concussion WITH LOC or PTA (Level A Recommendation):
Obtain non-contrast head CT if one or more of these factors are present:
- Headache
- Vomiting
- Age >60 years (not applicable to your 17-year-old)
- 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 anticoagulant medications)
For Concussion WITHOUT LOC or PTA (Level B Recommendation):
Consider non-contrast head CT if any of these are present:
- Focal neurologic deficit
- Vomiting
- Severe headache
- Age ≥65 years (not applicable to your 17-year-old)
- Physical signs of basilar skull fracture
- GCS score <15
- Coagulopathy
- Dangerous mechanism of injury (ejection from motor vehicle, pedestrian struck by vehicle, fall from >3 feet or 5 stairs)
Key Clinical Decision Rules
The evidence supports two validated clinical decision rules with essentially 100% sensitivity for identifying mild head trauma requiring neurosurgical intervention 1:
New Orleans Criteria: Highly sensitive (97.7%–99.4%) but lower specificity (3.0%–5.6%)—casts a wider net
Canadian CT Head Rule: Lower sensitivity for non-neurosurgical findings (83.4%–87.2%) but higher specificity (37.2%–39.7%)—reduces unnecessary imaging
Both rules have been validated in thousands of patients and are essentially 100% sensitive for detecting injuries requiring neurosurgical intervention 1.
Important Caveats
Age Consideration
While these guidelines apply to patients ≥16 years of age, your 17-year-old patient falls within this category. For younger pediatric patients, different criteria (PECARN) would apply 1.
The "No Risk Factor" Patient
Critical point: If your 17-year-old patient has none of the risk factors listed above, CT imaging is generally not indicated 1. Only 10% or less of mild head trauma cases show positive CT findings, and only 1% or less require neurosurgical intervention 1.
Coagulopathy Controversy
Most guidelines recommend CT in all patients with coagulopathy (including warfarin), though there is debate about whether this applies to antiplatelet therapy alone or minimal head trauma 1.
Radiation Exposure
The guidelines emphasize discussing the risks of CT radiation exposure with the patient and family when imaging is being considered, particularly in younger patients 2.
What NOT to Order
- Plain skull radiographs: Replaced by CT, which is more sensitive for neurosurgical lesions 1
- MRI in acute setting: Not indicated for initial evaluation of acute head trauma 1
- CT angiography: No role in initial evaluation without suspected vascular injury 1
Bottom Line Algorithm
- Assess GCS score: If <15, obtain CT
- Check for LOC or PTA: Determines which risk factor list to apply
- Screen for ALL risk factors in the appropriate category
- If ANY risk factor present: Obtain non-contrast head CT
- If NO risk factors present: CT not indicated; observe and provide discharge instructions
This algorithmic approach balances sensitivity for detecting clinically important injuries against unnecessary radiation exposure in young patients 1, 2.