Hypothesis. This study aimed to evaluate whether there is a difference in the degree of intracochlear trauma when the cochlear implant electrode arrays is inserted through different quadrants of the round window membrane. Background. The benefits of residual hearing preservation in cochlear implant recipients have promoted the development of atraumatic surgeries. Minimal trauma during electrode insertion is crucial for residual hearing preservation. Methods. In total, 25 fresh human temporal bones were subjected to mastoidectomy and posterior tympanotomy. The cochlear implant electrode array was inserted through the anterosuperior quadrant of the round window membrane in 50% of the bones and through the anteroinferior quadrant in the remaining 50%. The temporal bones were dehydrated, embedded in epoxy, serially polished, stained, viewed through a stereomicroscope, and photographed with the electrode arrays in situ. The resulting images were analyzed for signs of intracochlear trauma. Results. Histological examinations revealed varying degrees of damage to the intracochlear structures, although the incidence and severity of intracochlear trauma were not influenced by the quadrant of insertion. Conclusions. The incidence and severity of intracochlear trauma were similar in all samples, irrespective of electrode array insertion through the anterosuperior or anteroinferior quadrant of the round window membrane.

Introduction Middle fossa approach has been suggested as an alternative for patients in whom other routes of electrode insertion are contraindicated. Even though there are temporal bone studies about the feasibility of introducing the cochlear implant through the middle fossa, until now, very few studies have described results when cochlear implant surgery is done through this approach. Objective The objective of this study is to review a series of temporal bone studies related to cochlear implantation through the middle fossa and the results obtained by different surgical groups after cochlear implantation through this approach. Data Sources PubMed, MD consult and Ovid-SP databases. Data Synthesis A total of 8 human cadaveric temporal bone studies and 6 studies reporting cochlear implant surgery through the middle fossa approach met the inclusion criteria. Temporal bone studies show that it is feasible to perform cochlear implantation through this route. So far, only two surgical groups have performed cochlear implantation through the middle fossa with a total of 15 implanted patients. One group entered the cochlea in the most upper part of the basal turn, inserting the implant in the direction of the middle and apical turns; meanwhile, the other group inserted the implant in the apical turn directed in a retrograde fashion to the middle and basal turns. Results obtained in both groups were similar. Conclusions The middle fossa approach is a good alternative for cochlear implantation when other routes of electrode insertion are contraindicated.

Objective To evaluate cochlear trauma after cochlear implant insertion through a middle fossa approach by means of histologic and imaging studies in temporal bones. Study Design Prospective cadaveric study. Setting University-based temporal bone laboratory. Subjects and Methods Twenty fresh-frozen temporal bones were implanted through a middle cranial fossa basal turn cochleostomy. Ten received a straight electrode and 10 a perimodiolar electrode. Samples were fixed in epoxy resin. Computed tomography (CT) scans determined direction, depth of insertion, and the cochleostomy to round window distance. The samples were polished by a microgrinding technique and microscopically visualized to evaluate intracochlear trauma. Descriptive and analytic statistics were performed to compare both groups. Results The CT scan showed intracochlear insertions in every bone, 10 directed to the middle/apical turn and 10 to the basal turn. In the straight electrode group, the average number of inserted electrodes was 12.3 vs 15.1 for the perimodiolar group ( U = 78, P = .0001). The median insertion depth was larger for the perimodiolar group (14.4 mm vs 12.5 mm, U = 66, P = .021). Only 1 nontraumatic insertion was achieved and 14 samples (70%) had important trauma (Eshraghi grades 3 and 4). No differences were identified comparing position or trauma grades for the 2 electrode models or when comparing trauma depending on the direction of insertion. Conclusion The surgical technique allows a proper intracochlear insertion, but it does not guarantee a correct scala tympani position and carries the risk of important trauma to cochlear microstructures.

Aos meus pais, José Octavio e Maria Helena, norte de moral e ética, exemplos pessoais e profissionais. Com esforço e dedicação construíram uma família sólida e unida. Seus valores, presença constante e amor são responsáveis por minhas qualidades, méritos e vitórias. Ao meu marido Pedro, essa é a nossa tese! Seu apoio aos meus sonhos é o alicerce para eles se tornarem realidade. Ao meu irmão Frederico, por todas as vezes que me escutou e me levantou. Nossa relação de irmão é a que desejo para meus filhos. Aos meus filhos Joaquim e Fernando, obrigada por me ensinar o que eu mais amo na vida: ser mãe de vocês.