Anatomic limitations of posterior exposure of the sinus tympani

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.

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.

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.

It is possible to expose the sinus tympani from the posterior by careful dissection through this triangle, which has almost constant dimensions.