What is the initial imaging study recommended for head injury, specifically for a plain Non-Contrast Scan (NSS)?

Initial Imaging Study for Head Trauma: Non-Contrast CT Scan

Non-contrast head CT is the recommended initial imaging study for head trauma when imaging is indicated by clinical decision rules. 1

Indications for Non-Contrast Head CT in Head Trauma

For Mild Head Trauma (GCS 13-15) with Loss of Consciousness or Post-Traumatic Amnesia:

• Non-contrast head CT is indicated if one or more of the following are present:
  • Headache 1, 2
  • Vomiting 1, 2
  • Age >60 years 1, 2
  • Drug or alcohol intoxication 1, 2
  • Deficits in short-term memory 1, 2
  • Physical evidence of trauma above the clavicle 1, 2
  • Post-traumatic seizure 1, 2
  • GCS score <15 1, 2
  • Focal neurologic deficit 1, 2
  • Coagulopathy 1, 2

For Mild Head Trauma without Loss of Consciousness or Post-Traumatic Amnesia:

• Non-contrast head CT should be considered if any of the following are present:
  • Focal neurologic deficit 1, 2
  • Vomiting 1, 2
  • Severe headache 1, 2
  • Age ≥65 years 1, 2
  • Physical signs of a basilar skull fracture 1, 2
  • GCS score <15 1, 2
  • Coagulopathy 1, 2
  • Dangerous mechanism of injury (e.g., ejection from a motor vehicle, pedestrian struck by a vehicle, fall from >3 feet or 5 stairs) 1, 2

For Moderate to Severe Head Trauma:

• Non-contrast head CT is always appropriate for patients with:
  • Moderate head trauma (GCS 9-12) 1
  • Severe head trauma (GCS 3-8) 1
  • Penetrating head trauma 1

Benefits of Non-Contrast CT for Initial Imaging

• Rapid acquisition time, making it ideal for potentially unstable trauma patients 3, 4
• High sensitivity for detecting neurosurgically relevant lesions such as hemorrhage, herniation, and hydrocephalus 1, 4
• Ability to detect skull fractures, which may not be visible on MRI 3, 5
• Compatible with life support equipment and monitoring devices commonly used in trauma settings 3, 4
• Widely available in emergency departments 4, 5

Clinical Considerations and Pitfalls

• Despite its utility, CT has limited sensitivity for non-hemorrhagic axonal injury and may miss subtle findings 6, 3
• Only 10% or less of mild head trauma cases will have positive findings on CT, and only 1% or less will require neurosurgical intervention 1, 2
• Multiplanar reformatted images should be included as they increase diagnostic accuracy 1
• For pediatric patients (under 16 years), different clinical decision rules apply and are addressed in separate guidelines 1

Follow-up Imaging Considerations

• Non-contrast head CT is appropriate for short-term follow-up in patients with:
  • Positive findings on initial imaging (e.g., subdural hematoma) 1, 7
  • New or progressive neurologic deficits 1, 6
• MRI may be more appropriate than repeat CT for persistent symptoms beyond the acute phase, as it offers superior detection of subtle abnormalities 6, 3
• In patients with normal initial CT but persistent unexplained neurologic findings, non-contrast brain MRI is indicated 6, 5

Other Imaging Modalities

• There is no evidence supporting the use of the following as initial imaging for acute head trauma:
  • CT angiography (unless vascular injury is suspected) 1
  • MRI (as initial imaging) 1
  • Skull radiographs (replaced by CT) 1
  • FDG-PET/CT 1
  • Functional MRI 1
  • MR spectroscopy 1

Non-contrast head CT remains the cornerstone of initial imaging evaluation for head trauma, providing rapid assessment of potentially life-threatening injuries while guiding immediate management decisions 4, 5, 8.