During FESS for chronic rhinosinusitis, uncinectomy is the initial step. The natural ostium of the maxillary sinus is located at the:

• A Posterior fontanelle, behind the uncinate process
• B Hiatus semilunaris, in the ethmoidal infundibulum, anteromedial to the natural ostium of the maxillary sinus ✓
• C Superior wall of the maxillary sinus near the orbital floor
• D Anterior fontanelle, inferior to the uncinate process attachment

Explanation

The natural ostium of the maxillary sinus opens into the ethmoidal infundibulum (posterior to the uncinate process) via the hiatus semilunaris, which is the crescentic gap between the uncinate process and the bulla ethmoidalis. After uncinectomy, the infundibulum is opened and the natural maxillary ostium is identified on the medial wall of the infundibulum. The anterior and posterior fontanelles are membranous areas where accessory ostia may form, not the natural ostium.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.