Residual hearing preservation after full cochlear implantation of long electrodes Conclusion: After applying full cochlear implantation of long electrodes so that the long electrodes are inserted into the cochlear region of residual hearing, the residual hearing of the patient is still well preserved. Purpose: The noninvasive concept of new electrode designs and noninvasive surgical techniques have enabled the preservation of residual hearing in cochlear implant recipients, and EAS (electroacoustic co-stimulation) and residual hearing preservation have become a new trend in cochlear implantation for patients with residual hearing at low frequencies. However, full implantation of long or medium-length electrodes for residual hearing preservation is still a challenging area that needs to be debated. Methods: In this study, a round window approach, an electrode of noninvasive design, and dexamethasone treatment were used. The noninvasiveness of total electrode implantation (preservation of residual hearing, protection of vestibular function) was evaluated. RESULTS: The postoperative evaluation of electrode total implantation showed excellent preservation of residual hearing in the low-frequency region in all five patients. Postoperative imaging and reference tone topography determined full implantation of the electrodes and showed the frequencies corresponding to the depth of electrode implantation. Based on the analysis of the available cases in this study, the key to the noninvasiveness of the round-window approach is its minimal drilling and grinding time and the preservation of vestibular function.