Temporal bone changes in the angle of insertion after cochlear implantation and its effects on outcome: Unlocking the controversy.

Introduction: A meaningful social life depends on our ability to perceive and respond to our environment, with hearing being crucial. Deafness impacts both individuals and families, making cochlear implantation (CI) vital for those with hearing loss. Success in CI relies on factors like proper patient selection, electrode placement, and post-operative monitoring. Studies show deeper electrode insertion and more active electrodes improve speech perception, while optimal angles and electrode lengths enhance outcomes. Despite advancements, the long-term effects of changes in electrode insertion angle on speech, language, and societal integration remain underexplored. This study aims to address this gap by examining these long-term effects. Methods: Sixty children with bilateral congenital profound SNHL (sensorineural hearing loss) who were implanted via a conventional posterior tympanotomy round window approach prior to 5 years of age were analyzed for angle of insertion using postoperative X-ray. (Modified Stenver’s view). Insertional angle ‘ICI’ (immediate post operatively) and ‘TCI’ (3 years after cochlear implantation) was assessed for angle change. Both the observers measuring the insertion angle were blinded with each other. The outcome analysis of each implant recipient was performed under the domains of hearing, speech, language and integration to society. The hearing domain was assessed using the Revised CAP (Category of Auditory Performance), aided audiogram, and FAPCI (Functioning after Pediatric Cochlear Implantation)], speech assessed using the SIR (Speech Intelligibility Rating) and MUSS (Meaningful Use of Speech Scale) questionnaires], language assessed using the Extended REELS (Receptive Expressive Emergent Language Scale)], and subjective evaluation of the implant recipient’s ability to integrate into society based on educational attainment. Results: The angle of insertion at two time points was compared. No statistically significant difference was observed (Paired Wilcoxon test: v-367.0 p=0.122) between the two measurements. Outcome analysis in hearing, speech and language scoring suggested that a cochlear insertion angle of 270-360 degrees produced better outcomes than a complete cochlear insertion. Conclusion: Over a long-time period, we observed a minimal, yet not statistically significant, change in the angle of electrode insertion. It can be concluded that skull growth had no effect on the angle of insertion. An optimal insertion of 270-360 degree would suffice for successful outcome compared to deeper insertion (>360 degree).