What is the approach to ruling out and diagnosing traumatic brain injury (TBI) secondary to trauma in a patient with a history of head injury, considering their mechanism of injury, level of consciousness, and past medical history?

Approach to Ruling Out and Diagnosing Traumatic Brain Injury

The initial assessment of TBI severity relies on the Glasgow Coma Scale (specifically the motor component), pupillary size and reactivity, followed by non-contrast head CT based on validated clinical decision rules to identify patients requiring imaging. 1

Initial Clinical Assessment

Primary Severity Classification

• Assess GCS score immediately, documenting all three components (Eye-Verbal-Motor), with particular emphasis on the motor response as it remains the most robust predictor even in sedated patients 1, 2

  • Mild TBI: GCS 13-15
  • Moderate TBI: GCS 9-12
  • Severe TBI: GCS 3-8 2

• Evaluate pupillary size and reactivity as these are key predictors of neurological outcome at 6 months, validated in studies of over 15,000 patients 1

Critical Secondary Insult Detection

• Immediately identify and correct systemic factors that worsen outcomes:
  • Hypotension (systolic BP <90 mmHg for ≥5 minutes) increases mortality significantly 1
  • Hypoxemia (SaO2 <90%) is associated with increased mortality, with duration of hypoxemic episodes being particularly deleterious 1
  • The combination of hypotension and hypoxemia carries a 75% mortality rate 1

Neuroimaging Decision-Making

For Mild TBI (GCS 13-15)

Level A Recommendation: Perform non-contrast head CT if the patient has loss of consciousness OR post-traumatic amnesia PLUS any of the following: 1

• Headache
• Vomiting
• Age >60 years
• 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

Level B Recommendation: Consider non-contrast head CT even WITHOUT loss of consciousness or amnesia if: 1

• Focal neurologic deficit present
• Vomiting
• Severe headache
• Age ≥65 years
• Physical signs of basilar skull fracture
• GCS score <15
• Coagulopathy
• Dangerous mechanism of injury (ejection from vehicle, pedestrian struck, fall >3 feet or 5 stairs)

Validated Clinical Decision Rules

Three major prediction rules can safely identify patients who can avoid CT (sensitivity 97-100%): 1

Canadian CT Head Rule (for GCS 13-15):

• High-risk factors: GCS <15 at 2 hours, suspected open skull fracture, signs of basilar skull fracture, ≥2 episodes of vomiting, age ≥65 years, amnesia >30 minutes before impact, dangerous mechanism 1

New Orleans Criteria (for GCS 15 only):

• Headache, vomiting, age >60 years, drug/alcohol intoxication, persistent anterograde amnesia, visible trauma above clavicles, seizure 1

For Moderate to Severe TBI (GCS ≤12)

• Non-contrast head CT is mandatory for all patients 1, 2

Serial Neurological Monitoring

Frequency of Reassessment

Repeat clinical examination is essential to detect secondary neurological deterioration: 1

• For moderate TBI (GCS 9-13): Every 15-30 minutes for first 2 hours, then hourly for 4-12 hours depending on protocol 1
• Any decrease of ≥2 points in GCS or new neurological deficit mandates repeat CT scan 1

Repeat Imaging Indications

• Perform repeat CT for any neurological deterioration (Class I recommendation) 1
• Routine repeat CT is NOT recommended for mild TBI with negative initial CT (only 2.3-3.9% show management changes) 1
• Exception: Anticoagulated patients with abnormal initial CT warrant repeat imaging 1

Critical Pitfalls to Avoid

The "Mild" TBI Misnomer

• Up to 15% of patients with GCS 15 have acute intracranial lesions on CT, and <1% require neurosurgical intervention 1, 2
• 5-15% of mild TBI patients have compromised function at 1 year, despite the "mild" label 2
• Absence of loss of consciousness does NOT exclude significant injury: 1.8% of patients without LOC have intracranial lesions, and 0.6% require neurosurgery 3

Imaging Limitations

• Negative CT does not exclude clinically significant TBI, particularly diffuse axonal injury or hypoxic-ischemic encephalopathy 1
• Patients with GCS 13-15 but intraparenchymal lesions on CT perform neuropsychologically similar to moderate TBI patients 4
• MRI is more sensitive for axonal injury but is NOT routinely recommended in acute mild TBI 1

Special Populations

• Anticoagulated patients require lower threshold for imaging and consideration of repeat CT 1
• Elderly patients (≥60-65 years) have higher risk and warrant imaging even with minimal symptoms 1, 3

Documentation Requirements

• Record pre-sedation GCS (especially motor component) and pupillary exam before any sedation or intubation, as these cannot be reliably assessed afterward 1, 4
• Document mechanism of injury, duration of any loss of consciousness (<30 minutes for mild TBI), and duration of post-traumatic amnesia (<24 hours for mild TBI) 2