What is the best imaging technique to determine the cause of recurrent sinusitis?

Best Imaging Technique for Determining the Cause of Recurrent Sinusitis

Non-contrast CT scan is the best imaging technique for determining the cause of recurrent sinusitis, as it provides excellent anatomic detail of the paranasal sinuses and is considered the gold standard for routine sinus evaluation. 1

Imaging Modality Selection

CT Scan (First-line)

• Non-contrast CT is the optimal technique for:

  • Evaluating recurrent acute sinusitis (RARS) 2
  • Providing detailed visualization of the ethmoid sinuses 2
  • Delineating complex ethmoidal anatomy and ostiomeatal complex areas 2
  • Identifying anatomic variations that may contribute to recurrent disease 2
  • Preoperative evaluation before surgical intervention 2

• Low-dose CT protocols should be utilized when possible to reduce radiation exposure while maintaining diagnostic accuracy 1

• Contrast-enhanced CT should be reserved for specific scenarios:

  • Suspected complications (orbital, intracranial extension) 1
  • Suspected cavernous sinus thrombosis 1
  • Suspected invasive fungal sinusitis 1
  • Suspected sinonasal mass or neoplasm 1

MRI (Second-line/Complementary)

• MRI is indicated in specific situations:

  • Suspected fungal sinusitis 2, 1
  • Differentiating between inflammatory disease and malignant tumors 2, 3
  • Detecting intracranial complications 1, 4
  • Better differentiation of mucosal thickening from secretions 1

• MRI has limitations:

  • Limited ability to define bony anatomy 2, 5
  • May require sedation in young children 1
  • Longer imaging time 2

Imaging Techniques to Avoid

• Plain radiography is not recommended due to:

  • Poor sensitivity (25-41% for most sinus groups) 1
  • Inaccuracy in a high percentage of patients 2
  • Limited evaluation of ethmoid sinuses due to structural superimposition 2
  • Limited role in modern management of sinusitis 5

• Ultrasonography has limited utility but may be useful in:

  • Pregnant women to avoid radiation exposure 2, 1
  • Determining amounts of retained sinus secretions 2

Clinical Decision Algorithm

1. Initial evaluation: Nasal endoscopy and clinical evaluation form the basis for diagnosis 6

2. When to order imaging:

   • Symptoms persisting without improvement for ≥10 days despite medical therapy
   • "Double sickening" pattern
   • Recurrent acute sinusitis
   • Chronic rhinosinusitis
   • Sinonasal polyposis
   • Suspected complications 1

3. First-line imaging: Non-contrast CT of maxillofacial region

   • Provides accurate depiction of sinus anatomy and soft-tissue changes
   • Allows multiplanar reconstruction
   • Use low-dose protocols to minimize radiation exposure 1

4. When to add contrast to CT:

   • Suspected orbital complications
   • Suspected intracranial extension
   • Suspected cavernous sinus thrombosis
   • Suspected invasive fungal sinusitis
   • Suspected sinonasal mass or neoplasm 1

5. When to order MRI (after CT or in specific cases):

   • Suspected fungal sinusitis (97% diagnostic accuracy for intracranial complications) 1
   • Suspected intracranial complications not adequately visualized on CT 1, 4
   • Need to differentiate inflammatory disease from neoplasm 2, 3
   • Consider adding MR venography for suspected venous thrombosis 1

Common Pitfalls to Avoid

• Overuse of imaging for uncomplicated sinusitis 1
• Performing both non-contrast and contrast CT unnecessarily 1
• Failing to use contrast when complications are suspected 1
• Imaging too soon after treatment (less than 4 weeks after acute bacterial sinusitis) 1
• Relying on plain radiographs for diagnosis 2, 1
• Overdiagnosis based on nonspecific CT findings (mucosal thickening can be seen in 40% of asymptomatic adults) 5

CT remains the gold standard for pathological-anatomical evaluation of paranasal sinus disease, especially for planning surgical procedures 7. The combination of clinical findings with appropriate imaging provides the best guidance for clinical management and treatment of recurrent sinusitis 3.