Anatomic limitations of posterior exposure of the sinus tympani.

OBJECTIVE: The sinus tympani is a challenging area for the otologic surgeon to access and from which to remove the disease process. Recently, a posterior approach to the sinus tympani through the mastoid was proposed as an alternative technique in cases of deep sinus tympani. STUDY DESIGN AND SETTING: The posterior approach was performed by dissecting the triangular bony area formed by the facial nerve, lateral semicircular canal, and posterior semicircular canal in 8 temporal bone specimens. RESULTS: The edges of the triangle on the facial nerve and lateral semicircular canal were almost constant at 5 mm. The edge on the posterior semicircular canal was about 4 mm. CONCLUSION: It is possible to expose the sinus tympani from the posterior by careful dissection through this triangle, which has almost constant dimensions.