Evaluation of the Relationship Between Facial Nerve and Lateral Semicircular Canal in the Posterior Tympanotomy Approach

Background : To clinically and radiologically evaluate the relationship between the facial nerve and the lateral semicircular canal during posterior tympanotomy. Methods: Patients who received cochlear implants between 2010 and 2020 were included in the study. The relationship between the facial nerve and the lateral semicircular canal was classified into 3 types by evaluating the axial section computed tomography images. If the facial nerve passed medially without contacting the lateral semicircular canal dome, it was classified as type 1; if the facial nerve passed by contacting the medial border of the lateral semicircular canal dome, it was classified as type 2; and if the facial nerve contacted the lateral border of the lateral semicircular canal dome or passed more laterally, it was classified as type 3. Results: In total, 309 ears of 257 patients [139 males (54.1%) and 118 females (45.9%)] were included in the study. Ninety-three (30.1%) of the ears were classified as type 1, 179 (57.9%) were type 2, and 37 (12%) were type 3. It was found that the combined posterior tympanotomy/endomeatal approach was used in 6 ears (1.9%), of which 4 were type 3, and 2 were type 2 (P = .006). Conclusion: Systematic evaluation of the relationship between facial nerve and lateral semicircular canal in computed tomography axial sections might help prevent facial nerve damage that can occur during posterior tympanotomy. It was concluded that type 3 ears should be evaluated in this respect, as a combined posterior tympanotomy/endomeatal approach may be required.