A patient with cholesteatoma undergoes mastoid surgery. The surgeon notes disease extending into a deep air cell located medial to the facial nerve and inferior to the lateral semicircular canal, opening into the middle ear just below the oval window. This recess, notorious for residual cholesteatoma because it cannot be fully visualised through the facial recess approach, is the:

• A Facial recess
• B Sinus tympani ✓
• C Hypotympanic air cells
• D Supratubal recess

Explanation

The sinus tympani is a deep posterior tympanic recess lying medial to the facial nerve, bounded above by the ponticulus near the oval window and below by the subiculum near the round window. It opens toward the mesotympanum but its depth hides disease from both transcanal and facial recess views, making it a classic site of residual cholesteatoma. The facial recess, by contrast, lies lateral to the facial nerve and is surgically approachable via posterior tympanotomy.

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

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Written and medically reviewed by the StethoPrep medical team.