When should a computed tomography (CT) scan be ordered in patients with head trauma?

CT Scan Indications in Head Trauma

CT scans should be performed systematically and without delay in all patients with severe (GCS ≤8) or moderate (GCS 9-13) traumatic brain injury, while patients with mild TBI (GCS 14-15) require CT only if they have specific risk factors. 1, 2

Decision Algorithm Based on Severity

Severe TBI (GCS ≤ 8)

• Always obtain CT scan without delay 1
• Consider cervical spine CT simultaneously

Moderate TBI (GCS 9-13)

• Always obtain CT scan without delay 1
• Consider cervical spine CT simultaneously

Mild TBI (GCS 14-15)

CT scan is indicated if ANY of the following risk factors are present:

• Signs of basilar skull fracture (rhinorrhea, otorrhea, hemotympanum, retroauricular hematoma, periorbital hematoma) 1, 2
• Displaced skull fracture 1
• Post-traumatic seizure 1, 2
• Focal neurological deficit 1, 2
• Coagulation disorders or anticoagulant therapy 1, 2
• Age >60-65 years 1, 2
• Drug or alcohol intoxication 1, 2
• Deficits in short-term memory 1
• Physical evidence of trauma above the clavicle 1, 2
• Headache (especially severe) 1, 2, 3
• Vomiting 1, 2, 3
• GCS score <15 (not reaching GCS of 15 within 2 hours) 1, 2
• Dangerous mechanism of injury (ejection from vehicle, pedestrian struck, fall from >3 feet or 5 stairs) 1, 2

Special Considerations

Patients with Loss of Consciousness (LOC) or Post-Traumatic Amnesia (PTA)

• CT scan is indicated if ANY of the risk factors listed above are present 1, 2
• The New Orleans Criteria is highly sensitive (97.7%-99.4%) but less specific (3.0%-5.6%) 1

Patients without LOC or PTA ("Minimal Head Injury")

• Canadian CT Head Rule can be applied with 100% sensitivity for detecting intracranial hemorrhage 4
• CT scan should be considered with:
  • Age >65 years
  • Dangerous mechanism of injury
  • Vomiting
  • Severe headache
  • Signs of basilar skull fracture 1, 4

Patients on Anticoagulation

• Most guidelines recommend CT for all head trauma patients on anticoagulants 1, 2
• However, patients with normal GCS and no focal neurologic deficits may have very low risk of significant findings 5
• Consider CT even with minimal trauma in these patients due to higher bleeding risk 3

When NOT to Order CT Scan

• Patients with mild head injury (GCS 15) without ANY of the risk factors listed above 1, 2, 3
• Patients with minimal head injury and no risk factors have extremely low risk of clinically significant intracranial injury 4

Follow-up Imaging Considerations

• Routine repeat head CT is not warranted in patients with normal neurologic examination 6
• Second CT scan is indicated if:
  • Secondary neurological deterioration occurs
  • Decrease of at least two points in Glasgow Coma Score 1
  • Altered mental status, focal deficits, or pupillary changes 6

Pitfalls to Avoid

1. Relying solely on GCS: A normal GCS (15) should not be the only factor in deciding against imaging if other risk factors are present 2
2. Ignoring age: Patients >60-65 years have higher risk for intracranial injury even with minimal symptoms 2
3. Overlooking anticoagulation: Consider this a significant risk factor even with minor trauma 1, 2
4. Routine repeat CT: Not necessary without neurological deterioration 6
5. Delayed imaging in elderly: Can significantly increase morbidity and mortality 2

CT remains the first-line imaging modality for acute head trauma evaluation due to its speed, availability, and high sensitivity for acute hemorrhage and skull fractures 2. MRI may be considered as a second-line test if symptoms persist despite normal initial CT 2, 7.