Should a computed tomography (CT) scan of the brain be performed in patients with suspected orbital cellulitis?

CT Brain Imaging in Suspected Orbital Cellulitis

CT brain imaging should not be performed as the initial evaluation in patients with suspected orbital cellulitis; instead, CT orbits with IV contrast is the recommended first-line imaging modality, with brain imaging reserved only for cases with suspected intracranial complications. 1

Initial Imaging Approach

• First-line imaging: CT orbits with IV contrast

  • Most useful for suspected orbital infection 1
  • Helps differentiate preseptal from postseptal cellulitis and abscess 1
  • Superior for detecting foreign bodies, calcifications, and bone erosion 1
  • Can evaluate for subperiosteal abscess that may require surgical intervention 1

• When to consider brain imaging:

  • Only when intracranial complications are suspected 1
  • Signs suggesting intracranial involvement:
    • Altered mental status
    • Severe headache
    • Neurological deficits
    • Poor response to initial therapy 2

Intracranial Complications Requiring Brain Imaging

Brain imaging should be added when there are concerns for:

• Cavernous sinus thrombosis
• Subdural empyema
• Meningitis
• Brain abscess
• Cerebritis 1, 3, 4

Imaging Modality Selection for Suspected Complications

1. CT head with IV contrast:

   • May be considered when intracranial complications are suspected 1
   • Faster acquisition time (beneficial in unstable patients)
   • More readily available in emergency settings 3

2. MRI brain with contrast:

   • Preferred when intracranial extension is suspected 1, 2
   • Provides greater soft-tissue resolution than CT
   • Should include high-resolution images of cavernous sinuses 1
   • Better for evaluating cavernous sinus thrombosis and parenchymal brain involvement 2

Risk Factors for Complications

Patients with the following factors have higher risk for complications and may warrant consideration of brain imaging:

• Immunocompromised status (especially for invasive fungal infections) 1
• Diabetes mellitus 4
• Poor response to initial antibiotic therapy
• Proptosis, pain with eye movement, or ophthalmoplegia 5
• Age >3 years
• Previous antibiotic therapy
• Neutrophil count >10,000/μL
• Absence of conjunctivitis 5

Clinical Pitfalls to Avoid

• Relying solely on clinical examination to rule out intracranial complications
• Delaying imaging in patients with concerning symptoms
• Performing unnecessary brain CT in uncomplicated cases
• Using plain radiography, which is insufficient for detecting orbital pathology 1
• Failing to use contrast enhancement, which is essential for detecting abscesses and vascular complications 6, 7

In summary, while brain imaging is not routinely indicated for all cases of suspected orbital cellulitis, it should be promptly obtained when there are signs of intracranial extension, as delayed diagnosis of complications can lead to permanent vision loss, neurological deficits, or death 2.