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CT Maxillofacial (Sinus)

Non-contrast CT of the paranasal sinuses is the standard imaging test for chronic and recurrent rhinosinusitis and for mapping the surgical anatomy before functional endoscopic sinus surgery. Its high bony detail delineates the ostiomeatal complex, drainage pathways, septal and turbinate anatomy, and critical anatomical variants relevant to surgical safety. It also assesses facial fractures and screens for complications, with contrast reserved for suspected aggressive infection or neoplasm.

Indications

  • Chronic or recurrent rhinosinusitis refractory to medical therapy
  • Preoperative mapping of sinus anatomy before endoscopic sinus surgery
  • Nasal obstruction and evaluation of septal deviation or turbinate hypertrophy
  • Facial/midface trauma to assess sinus wall and orbital fractures
  • Suspected complications of sinusitis (orbital, intracranial) - often with contrast
  • Assessment of suspected sinonasal mass, mucocele, or fungal disease

Contraindications & Cautions

  • No absolute contraindication for the standard non-contrast study
  • Pregnancy: justify; the head is out of the primary pelvic beam but limit dose and use low-dose protocols
  • Radiation stewardship, particularly to the lens; use low-dose sinus CT protocols
  • Contrast (for suspected complications/tumor) requires renal function and allergy screening
  • Recent nasal surgery or acute epistaxis may alter mucosal appearances

Patient Preparation

  • No fasting for standard non-contrast sinus CT
  • Ideally image after a course of medical therapy so mucosal disease reflects true chronic change
  • Remove dentures, earrings, and other metallic objects from the field to reduce artifact
  • Position supine or prone; acquire volumetric data allowing multiplanar reformats
  • Explain breath-hold/stillness; sedation may be required in young children
  • Confirm the clinical question, surgical planning intent, and any prior imaging

Technique & Parameters

  • Thin-section (0.5-1.25 mm) volumetric non-contrast acquisition covering frontal sinus to hard palate
  • Reconstruct primary coronal, axial, and sagittal images in a bone (high-frequency) algorithm
  • Low-dose technique (reduced mAs) is standard given high inherent bone-air contrast
  • Review on bone (W2000-4000/L400-700) and soft-tissue windows
  • Coronal plane best demonstrates the ostiomeatal complex; sagittal aids frontal recess and sphenoethmoidal recess
  • Add IV contrast when orbital/intracranial complication or neoplasm is suspected

Systematic Review

  • Assess each sinus (maxillary, ethmoid, frontal, sphenoid) for mucosal thickening, opacification, and fluid levels
  • Evaluate the ostiomeatal complex and drainage pathways for obstruction
  • Examine the nasal septum for deviation/spurs and the turbinates for hypertrophy or concha bullosa
  • Identify surgically critical variants: Onodi (sphenoethmoidal) cell, Haller (infraorbital) cell, dehiscent lamina papyracea
  • Assess the skull base, cribriform plate, and fovea ethmoidalis height (Keros classification)
  • Review the orbits, optic canals, and carotid canals for dehiscence and proximity
  • Check bony walls for erosion, expansion, or fracture and inspect the dentition/alveolus

Key Findings & Significance

  • Mucosal thickening and ostiomeatal obstruction: chronic rhinosinusitis
  • Air-fluid level: acute sinusitis (or post-lavage/trauma)
  • Hyperdense sinus content with bony expansion/erosion and calcifications: fungal sinusitis
  • Expansile opacified sinus with wall remodeling: mucocele
  • Bony erosion with a soft-tissue mass: neoplasm (benign or malignant) - characterize further with contrast/MRI
  • Septal deviation, spurs, concha bullosa, and other variants contributing to obstruction
  • Sinus wall or orbital floor fracture with herniation or emphysema in trauma

Differential Considerations

  • Unilateral sinus opacification: fungal sinusitis vs neoplasm vs obstructing polyp/mucocele vs odontogenic source
  • Hyperdense sinus contents: inspissated secretions/fungal disease vs hemorrhage vs calcified mass
  • Expansile sinus lesion: mucocele vs polyp vs benign tumor (e.g., inverted papilloma) vs malignancy
  • Diffuse polypoid mucosal disease: chronic polyposis vs allergic fungal sinusitis vs cystic fibrosis
  • Bony sclerosis/thickening: chronic osteitis vs fibrous dysplasia vs osteoma
  • Opacified maxillary sinus with adjacent tooth: odontogenic sinusitis vs primary sinus disease

Pearls & Pitfalls

  • Always flag surgically dangerous variants (Onodi cell, dehiscent lamina papyracea/carotid, low skull base) for the surgeon
  • Report Keros classification of the olfactory fossa depth to alert to CSF-leak risk
  • Unilateral opacification, bone erosion, or calcification should prompt concern for fungal disease or neoplasm, not simple sinusitis
  • Image after medical therapy where possible; transient viral mucosal change overestimates chronic disease
  • Correlate maxillary sinus disease with the adjacent dentition to identify an odontogenic source
  • Assess the orbit and skull base carefully when infection is aggressive - complications change management

Structured Report

  • State technique (non-contrast low-dose sinus CT) and comparison
  • Report mucosal disease and drainage-pathway (ostiomeatal complex) patency per sinus
  • Describe septal and turbinate anatomy and any obstructing variants
  • List surgically relevant anatomical variants and skull-base/orbital relationships
  • Note bone erosion, expansion, fractures, and any features concerning for fungal disease or neoplasm
  • Impression: dominant diagnosis, surgical anatomy summary/caveats, and any recommendation for contrast MRI/biopsy

References

  • ACR Appropriateness Criteria: Sinonasal Disease
  • European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS)
  • ACR-ASNR-SPR Practice Parameter for the Performance of Sinonasal CT
  • Som & Curtin, Head and Neck Imaging

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.