In transsphenoidal endoscopic surgery, the sphenoid sinus is entered through its natural ostium. Where is the sphenoid ostium located?
- A Lateral to the middle turbinate, at the level of the ethmoid bulla
- B Medial to the superior turbinate, approximately 1 to 1.5 cm above the posterior choana ✓
- C In the sphenoethmoidal recess, immediately below the basal lamella
- D On the anterior face of the sphenoid, lateral to the vidian canal
Correct answer: B. Medial to the superior turbinate, approximately 1 to 1.5 cm above the posterior choana
Explanation
The sphenoid ostium lies on the anterior face of the sphenoid bone, medial to the superior (or supreme) turbinate and about 1 to 1.5 cm above the posterior choanal rim. It opens into the sphenoethmoidal recess. The safe surgical rule is to stay medial and inferior, because the internal carotid artery and optic nerve lie in the lateral wall of the sphenoid sinus. Locating the ostium too laterally risks carotid injury.
Reference: Cummings Otolaryngology Head and Neck Surgery, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.