Deep round window insertion versus standard approach in cochlear implant surgery.

The aim of this study was to compare the outcomes of vestibular tests and the residual hearing of patients who have undergone full insertion cochlear implant surgery using the round window approach with a hearing preservation protocol (RW-HP) or the standard cochleostomy approach (SCA) without hearing preservation. A prospective study of 34 adults who underwent unilateral cochlear implantation was carried out. One group was operated using the RW-HP (n = 17) approach with Med-El +Flex(SOFT) electrode array with full insertion, while the control group underwent a more conventional SCA surgery (n = 17) with shorter perimodiolar electrodes. Assessments of residual hearing, cervical vestibular-evoked myogenic potentials (cVEMP), videonystagmography, subjective visual vertical/horizontal (SVH/SVV) were performed before and after surgery. There was a significantly (p < 0.05) greater number of subjects who exhibited complete or partial hearing preservation in the deep insertion RW-HP group (9/17) compared to the SCA group (2/15). A higher degree of vestibular loss but a lower degree of vertigo symptoms could be seen in the RW-HP group, but the differences were not statistically significant. It is possible to preserve residual hearing to a certain extent also with deep insertion. Full insertion with hearing preservation was less harmful to residual hearing particularly at 125 Hz (p < 0.05), than was the standard cochleostomy approach.