Hypothesis: The retrofacial approach is a feasible approach to the round window niche and that the Round window-Sigmoid sinus line will help determine the feasibility of retrofacial approach for cochlear implantation unless there is a very high jugular bulb.
Background: When the round window cannot be visualized by facial recess approach during cochlear implantation, other conservative techniques can be used to improve visualization such as the retrofacial approach.
Methods: Thirteen adult dry cadaveric temporal bones were studied. Computed tomography (CT) scan was obtained on all temporal bones. An imaginary Round window-Sigmoid sinus line was drawn on the axial images. We assessed whether this line is anterior (including intersection) or posterior to the facial nerve (FN). The following closest distances were measured on CT scans: 1) posterior semicircular canal (PSC)-FN, 2) PSC-Stapedius muscle, 3) PSC-Jugular bulb, 4) lateral semicircular canal (LSC)-Jugular bulb, 5) sigmoid sinus-FN. A canal wall-up mastoidectomy, facial recess, and retrofacial approach were performed in all specimens. We have noted whether we need a standard or an extended mastoidectomy.
Results: The Round window-Sigmoid sinus line was posterior to the FN in all specimens. The retrofacial approach was feasible and the round window was visualized in all specimens. Extended mastoidectomy was required in seven specimens and the PSC-FN was ≤ 3 mm in five of them.
Conclusion: Retrofacial approach is feasible in cochlear implantation when the Round window-Sigmoid sinus line is posterior to the FN and the jugular bulb is not obstructing the round window.