Comparing Slim Straight and Slim Perimodiolar Electrode Arrays for Cochlear Implantation: Hearing Results and Risks—A Systematic Review (2015–2025)

<b>Background/Objectives</b>: Cochlear implant (CI) electrode array design plays a critical role in determining intracochlear position, hearing outcomes, and insertion-related risks. Straight (lateral wall) and perimodiolar electrode arrays are the two principal designs used in modern cochlear implantation, yet their comparative benefits and risks remain debated. We aim to systematically review and compare hearing outcomes and surgical risks associated with straight versus perimodiolar electrode arrays in cochlear implantation. <b>Methods</b>: A systematic literature search of PubMed, Embase, Scopus, and the Cochrane Library was conducted for studies published between 2015 and 2025. Comparative clinical studies reporting speech perception outcomes, residual hearing preservation, or electrode-related complications were included. Study selection followed PRISMA 2020 guidelines. <b>Results</b>: A total of 32 studies were included. Speech perception outcomes were generally comparable between straight and perimodiolar arrays. However, straight electrode arrays demonstrated significantly lower rates of scalar translocation and tip fold-over and superior residual hearing preservation in most comparative cohorts. Perimodiolar arrays showed potential advantages in electrophysiological efficiency but were associated with a higher risk of intracochlear trauma when malposition occurred. <b>Conclusions</b>: Contemporary evidence suggests that straight (lateral wall) electrode arrays offer a more favorable safety profile with equivalent functional hearing outcomes compared to perimodiolar arrays. Electrode positioning within the scala tympani appears to be a stronger determinant of outcome than electrode design alone.