(0927) Endoscopic Visualisation of the Round Window During Cochlear Implantation

Introduction: Endoscopes have been successfully used in middle-ear surgical procedures. In cochlear implantation (CI), locating the round window membrane (RWM) is crucial for atraumatic and soft electrode insertion. However, in pediatric patients and patients with cochleovestibular malformations, identification of the RWM is difficult. The use of an otoendoscope can facilitates excellent visualization of the RWM.

Methods: This study was carried out from July 2016 to January 2019 and September 2022 to December 2023. In total, 34 patients who underwent CI during this period were included in the study. After performing posterior tympanotomy, the accessibility of the round window membrane using the microscope was graded according to the St. Thomas Hospital (STH) classification. A 0-degree rigid otoendoscope (1.9 mm) was then inserted into the posterior tympanotomy, and the RWM was again visualized and graded according to the STH classification. For each patient, the RWM visibility achieved by microscope and endoscope was compared.

Results: The study had 34 patients who underwent CI surgery where the accessibility of the RWM using the microscope was classified as STH type IIa in 10 ears, type IIb in 18 and type III in 6. The accessibility of all 10 type IIa RWM using the microscope improved to type I using the endoscope. Of the 18 type IIb RWM, the grades of 10 improved to type I and 8 to type IIa using the endoscope. The accessibility of 5 of the type III RWM improved to type IIa using the endoscope, and one improved to IIb using the endoscope. For 2 patients, both with incomplete cochlear partition type II (STH type III using the microscope and IIa/IIb using the endoscope), a bony cochleostomy had to be performed for electrode insertion, because of unfavorable anatomy.

Conclusions: The study describes the auxiliary role of the endoscope in conventional transmastoid microscopic CI. The benefit of endoscope in CI is is improved visibility of the round window. This also reduces the risk of complications and is of particular benefit in patients with congenital malformations. The surgeons should be trained and well versed in both endoscopic and microscopic ear surgery.