In a canal wall up (CWU) mastoidectomy for chronic otitis media with cholesteatoma, the posterior tympanotomy approach is used to achieve adequate exposure. Which structure defines the posterior tympanotomy boundaries superiorly and inferiorly respectively?

• A Short process of incus superiorly; chorda tympani inferiorly
• B Fossa incudis superiorly; round window niche inferiorly ✓
• C Tegmen mastoideum superiorly; jugular bulb inferiorly
• D Lateral semicircular canal superiorly; facial nerve at second genu inferiorly

Explanation

Posterior tympanotomy (facial recess approach) is bounded superiorly by the fossa incudis (which houses the short process of incus), inferiorly by the round window niche, medially by the facial nerve, and laterally by the chorda tympani. This corridor gives access to the middle ear without removing the posterior canal wall, which is the hallmark of CWU mastoidectomy.

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

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Written and medically reviewed by the StethoPrep medical team.