In the ostiomeatal complex (OMC), the uncinate process plays a crucial role in sinus drainage. Medialization of the uncinate process on CT would be expected to obstruct drainage of which sinus first?

• A Frontal sinus, as the frontal recess drains directly into the inferior meatus
• B Ethmoid sinus, as the ethmoid bulla is posterior to the uncinate process
• C Maxillary sinus, as its ostium drains into the hiatus semilunaris (infundibulum) which is bounded anteromedially by the uncinate process ✓
• D Sphenoid sinus, as it drains medial to the uncinate via the sphenoethmoidal recess

Explanation

The uncinate process is a sickle-shaped projection of the ethmoid bone forming the medial boundary of the infundibulum (ethmoid infundibulum). The maxillary sinus ostium drains into the hiatus semilunaris via the ethmoid infundibulum. Medialization or lateralization of the uncinate process (common anatomical variant) can directly obstruct maxillary sinus drainage, making it the first sinus affected. The frontal sinus drains via the frontal recess (bounded anteriorly by the agger nasi cell and posteriorly by the bulla ethmoidalis) into the infundibulum, so uncinate pathology can also affect frontal drainage indirectly.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.