During translabyrinthine removal of a vestibular schwannoma, the surgeon works through a triangular dural window posterior to the internal acoustic meatus to reach the cerebellopontine angle. Which set of boundaries correctly defines this surgical landmark (Trautmann's triangle)?
- A Anteriorly the bony labyrinth, posteriorly the sigmoid sinus, superiorly the superior petrosal sinus ✓
- B Anteriorly the sigmoid sinus, posteriorly the bony labyrinth, inferiorly the jugular bulb
- C Anteriorly the internal acoustic meatus, posteriorly the mastoid emissary vein, superiorly the tegmen tympani
- D Anteriorly the carotid canal, posteriorly the sigmoid sinus, inferiorly the jugular bulb
Correct answer: A. Anteriorly the bony labyrinth, posteriorly the sigmoid sinus, superiorly the superior petrosal sinus
Explanation
Trautmann's triangle is bounded in front by the posterior semicircular canal and other labyrinthine bone, behind by the sigmoid sinus, and above by the superior petrosal sinus. Its floor of dura overlies the cerebellopontine angle, so it is the standard access route to that region after labyrinthectomy. Option B reverses the anterior and posterior limits, which is the classic error and the distractor to eliminate.
Reference: Cummings Otolaryngology Head and Neck Surgery, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.