• Floris Heutink, Simone R de Rijk, Berit M Verbist, Wendy J Huinck, and Mylanus Emmanuel A M EAM Department of Otorhinolaryngology..
• Department of Otorhinolaryngology.
• Otol. Neurotol. 2019 Aug 1; 40 (7): 900-910.

ObjectiveBy discussing the design, findings, strengths, and weaknesses of available studies investigating the influence of angular insertion depth on speech perception, we intend to summarize the current status of evidence; and using evidence based conclusions, possibly contribute to the determination of the optimal cochlear implant (CI) electrode position.Data SourcesOur search strategy yielded 10,877 papers. PubMed, Ovid EMBASE, Web of Science, and the Cochrane Library were searched up to June 1, 2018. Both keywords and free-text terms, related to patient population, predictive factor, and outcome measurements were used. There were no restrictions in languages or year of publication.Study SelectionSeven articles were included in this systematic review. Articles eligible for inclusion: (a) investigated cochlear implantation of any CI system in adults with post-lingual onset of deafness and normal cochlear anatomy; (b) investigated the relationship between angular insertion depth and speech perception; (c) measured angular insertion depth on imaging; and (d) measured speech perception at, or beyond 1-year post-activation.Data Extraction And SynthesisIn included studies; quality was judged low-to-moderate and risk of bias, evaluated using a Quality-in-Prognostic-Studies-tool (QUIPS), was high. Included studies were too heterogeneous to perform meta-analyses, therefore, effect estimates of the individual studies are presented. Six out of seven included studies found no effect of angular insertion depth on speech perception.ConclusionAll included studies are characterized by methodological flaws, and therefore, evidence-based conclusions regarding the influence of angular insertion depth cannot be drawn to date.

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