When to Perform CT Scan for Concussion
For mild traumatic brain injury (GCS 14-15), obtain a non-contrast head CT scan if ANY high-risk clinical feature is present, including signs of basilar skull fracture, displaced skull fracture, post-traumatic seizure, focal neurological deficit, coagulation disorders, or anticoagulant therapy. 1
Immediate CT Indications for Mild TBI (GCS 14-15)
Perform non-contrast CT scanning when patients present with any of the following:
High-Risk Clinical Features (Grade 1+ Recommendation)
- Signs of basilar skull fracture (hemotympanum, raccoon eyes, Battle's sign, CSF otorrhea/rhinorrhea) 1
- Displaced skull fracture on examination 1
- Post-traumatic seizure 1
- Any focal neurological deficit 1, 2
- Coagulation disorders or current anticoagulant therapy 1, 2
Additional Medium-High Risk Criteria
- GCS score <15 at 2 hours post-injury 2
- Vomiting ≥2 episodes 2
- Age ≥65 years 2
- Amnesia >30 minutes before impact 2
- Dangerous mechanism of injury (high-speed collision, ejection from vehicle, pedestrian struck) 2
- Severe or worsening headache 2
Moderate to Severe TBI (GCS 3-12)
Non-contrast CT is the mandatory initial imaging test for all patients with moderate to severe TBI (GCS ≤12), regardless of clinical findings. 3 This represents a Class I recommendation with strong consensus that CT is essential for triaging patients to surgery, admission with close observation, or determining prognosis. 3
Special Considerations for GCS 13-14 Patients
Patients with GCS 13-14 represent a distinct higher-risk subgroup within "mild" TBI:
- Significantly higher incidence of abnormal CT findings compared to GCS 15 patients 4
- Higher rates of neurological deterioration and need for neurosurgical intervention 4
- Recommend CT for all GCS 13-14 patients not improving within 4-6 hours of injury 4
When CT Can Be Safely Avoided
CT scanning may be deferred in patients meeting ALL of the following low-risk criteria:
- GCS score of 15 with normal neurological examination 2
- No loss of consciousness or amnesia 2
- No headache or vomiting 2
- No physical evidence of trauma above the clavicles 2
- Not on anticoagulant therapy 2
However, a critical caveat: normal cognitive screening scores (such as SAC ≥25) do NOT exclude intracranial injury—38.2% of CT-positive patients had normal SAC scores in one study. 5 Clinical decision rules should guide imaging, not isolated cognitive assessments.
Repeat CT Imaging Indications
Mandatory Repeat CT
- Any decrease of ≥2 points in GCS 1
- Development of new neurological deficits 1
- Neurological deterioration in patients with initial abnormal CT 6
Routine Repeat CT NOT Recommended
Do not perform routine repeat CT in mild TBI patients (GCS 13-15, AIS 1-2) with negative initial CT and stable neurological examination. 1, 7 In patients with mild TBI and minor injuries, worsening intracranial hemorrhage on repeat imaging did not predict need for surgical or medical intervention. 7 Clinical examination should guide the decision to reimage rather than arbitrary time intervals. 7
Critical Pitfalls to Avoid
- Do not rely on skull radiographs as a substitute for CT in patients with GCS 13-14 or high-risk features 4
- Do not discharge patients on anticoagulation without extended observation or admission, even with negative initial CT 1
- Do not use biomarkers (S100b, NSE, UCH-L1, GFAP) for routine clinical decision-making as they lack sufficient evidence for clinical use 1
- Do not assume normal mental status testing excludes injury—proceed with CT based on mechanism and risk factors 5
Algorithm Summary
- Assess GCS score: If ≤12, obtain immediate CT (Class I recommendation) 3
- For GCS 13-15, screen for high-risk features: Any present → obtain CT 1, 2
- If GCS 13-14 without immediate high-risk features: Observe 4-6 hours; if not improving → obtain CT 4
- If GCS 15 with ALL low-risk criteria met: May safely defer CT with structured discharge instructions 2
- Monitor all admitted patients: Any decline in GCS ≥2 points or new deficits → immediate repeat CT 1