When should a computed tomography (CT) scan be ordered to assess for orbital fracture?

CT Imaging for Orbital Fracture Assessment

Non-contrast orbital CT is the gold standard for evaluating orbital trauma and should be ordered immediately when orbital fracture is suspected, particularly in cases with signs of muscle entrapment, oculocardiac reflex, diplopia with positive forced ductions, or significant enophthalmos/hypoglobus. 1

Indications for Immediate CT Imaging

• Urgent/Immediate CT indications:

  • Suspected muscle or periorbital tissue entrapment (especially with oculocardiac reflex)
  • White-eyed blow-out fracture (trap-door fracture with muscle entrapment)
  • Globe subluxation into the maxillary sinus
  • Signs of optic nerve compression
  • Significant vision changes after trauma 2, 1

• CT within 2 weeks:

  • Symptomatic diplopia with positive forced ductions
  • Large floor fractures with hypoglobus
  • Progressive infraorbital hypoesthesia
  • Early enophthalmos causing facial asymmetry 2

Clinical Findings That Warrant CT Imaging

• Restricted ocular movements or diplopia
• Periorbital edema with blepharohematoma (58.3% of patients with isolated blepharohematoma have orbital fractures) 3
• Enophthalmos or hypoglobus
• Infraorbital nerve hypoesthesia
• Oculocardiac reflex symptoms (bradycardia, nausea, vomiting, dizziness) 2, 1

Optimal CT Protocol

• Non-contrast orbital CT with thin-section axial imaging (1mm slices)
• Multiplanar reconstructions, particularly coronal views
• Coverage should include the entire orbit and surrounding structures 1, 4

The combination of axial images with multiplanar reconstructions and 3D imaging provides the highest sensitivity (90.5%) for orbital fracture detection 5. Coronal views are particularly valuable for evaluating orbital floor fractures 6.

Evaluation Approach

When reviewing orbital CT images, systematically assess:

1. Bony orbit for fractures (floor, medial wall, lateral wall, roof)
2. Orbital contents for herniation into adjacent sinuses
3. Extraocular muscles for entrapment or edema
4. Globe integrity
5. Orbital apex and optic nerve complex
6. Presence of intraorbital air (emphysema) 1, 4

Common Pitfalls to Avoid

• Relying solely on plain radiographs (insufficient for orbital trauma)
• Delaying imaging when muscle entrapment is suspected
• Failing to recognize that entrapment can involve muscle or fat
• Waiting for oculocardiac reflex symptoms before diagnosing entrapment
• Premature surgical intervention without proper imaging assessment 1

Important Considerations

CT imaging is particularly valuable when clinical assessment is limited due to:

• Periorbital edema obscuring examination
• Patient's reduced level of consciousness
• Limited cooperation in alert patients
• Severity of associated head injuries 7

Remember that while CT is excellent for bony anatomy, it has limitations in soft tissue characterization and optic nerve pathology evaluation. In patients with suspected orbital fracture, CT findings should always be correlated with clinical examination to guide appropriate management decisions.