During cortical mastoidectomy, the surgeon drills along the linea temporalis but encounters a dense bony plate preventing entry into the antrum. This plate represents a persistence of the petrosquamous suture line and is known as:

• A Korner's septum ✓
• B Sinodural angle (Citelli's angle)
• C Scutum (spur of Henle)
• D Bill's bar

Explanation

Korner's septum is a persistent bony partition formed at the petrosquamosal junction that may be mistaken for the antrum itself during mastoid drilling. It must be penetrated or removed to enter the true mastoid antrum lying deep to it. Bill's bar separates the superior vestibular from the anterior inferior vestibular area at the fundus of the internal acoustic meatus, and Citelli's angle is a landmark between the sinus plate and tegmen, not an obstructing plate.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.