When is a head CT (Computed Tomography) scan indicated after a motor vehicle collision (MVC) with airbag deployment?

Head CT Indications After Motor Vehicle Collision with Airbag Deployment

Head CT is not routinely indicated after motor vehicle collision (MVC) with airbag deployment alone, but should be performed when specific risk factors or clinical findings are present, according to validated clinical decision rules.

Key Clinical Decision Rules for Head CT After MVC

Canadian CT Head Rule (CCHR)

• Head CT is indicated with any of the following high-risk factors 1, 2:

  • GCS score <15 at 2 hours after injury
  • Suspected open or depressed skull fracture
  • Signs of basilar skull fracture
  • Vomiting ≥2 episodes
  • Age ≥65 years

• Medium-risk factors also warranting CT 1, 2:

  • Amnesia >30 minutes before impact
  • Dangerous mechanism of injury

New Orleans Criteria (NOC)

• Head CT is indicated with any of the following 1, 2:
  • Headache
  • Vomiting
  • Age >60 years
  • Drug or alcohol intoxication
  • Persistent anterograde amnesia (short-term memory deficit)
  • Physical evidence of trauma above the clavicle
  • Seizure

Clinical Findings That Warrant Head CT After MVC

• Neurological deficits: Any focal neurological signs suggest possible intracranial injury 1, 2
• Altered mental status: Decreased level of consciousness or confusion requires imaging 1, 2
• Severe headache or vomiting: These symptoms may indicate elevated intracranial pressure 2, 3
• Anticoagulation therapy: Patients on blood thinners have higher risk of intracranial bleeding 2
• Signs of basilar skull fracture: Including periorbital ecchymosis, Battle's sign, hemotympanum, or CSF otorrhea/rhinorrhea 2
• Deterioration of consciousness: Any decline in alertness or responsiveness 2

Special Considerations

• Airbag deployment alone is not an independent indication for head CT 4
• Injury Severity Score (ISS) is a reliable predictor of positive head CT findings in MVC patients 4
• Front-seat passengers may be at higher risk for traumatic head injury than drivers 4
• Mechanism of injury should be considered - high-speed collisions or rollovers may increase risk 1, 2
• Children under 12 with airbag deployment should receive special consideration due to higher risk of cervical spine injuries 5

When Head CT Can Be Safely Avoided

• Normal neurological examination with GCS 15 1
• No loss of consciousness or amnesia 1, 6
• No headache or vomiting 2, 6
• No physical evidence of trauma above the clavicle 1, 2
• No anticoagulant therapy 2
• No drug or alcohol intoxication 1, 6

Algorithm for Decision-Making

1. Assess GCS score - if <15, obtain head CT 1
2. Check for high-risk factors from CCHR (age ≥65, vomiting ≥2 times, signs of skull fracture) 1, 2
3. Evaluate for NOC criteria (headache, any vomiting, age >60, trauma above clavicle) 1, 2
4. Consider mechanism of injury and patient position in vehicle 4
5. Assess for anticoagulant use 2
6. If all negative, head CT can be safely avoided with high negative predictive value 1

Pitfalls to Avoid

• Relying solely on airbag deployment as an indication for CT 4
• Failing to recognize subtle neurological deficits that may indicate brain injury 2, 3
• Not considering anticoagulant use as a risk factor 2
• Missing delayed presentations of intracranial hemorrhage in patients discharged without CT 1