The surgeon will follow a classical surgical procedure for the cochlear implantation, i.e. mastoidectomy to access the temporal bone, posterior tympanotomy to access the cochlea and round window (RW) approach for the CI electrode array insertion. Before opening the RW, the eCochG recording electrode is placed on the cochlear promontory, and placed not to obstruct the surgery. The probe is thus maintained during the whole MANUAL insertion (by the surgeon).

The surgeon will follow a classical surgical procedure for the cochlear implantation, i.e. mastoidectomy to access the temporal bone, posterior tympanotomy to access the cochlea and round window (RW) approach for the CI electrode array insertion. Before opening the RW, the eCochG recording electrode is placed on the cochlear promontory, and placed not to obstruct the surgery. The probe is thus maintained during the whole ROBOTIC insertion.

Before the mastoidectomy, the ear canal is cleaned, the insert earphone is connected to the Eclipse (Oticon Medical software) preamplifier and placed into the ear canal. The EEG scalp electrodes (active, ground electrode) are placed on the patient's head. After the posterior tympanotomy, the reference electrode (eCochG probe) is placed on the cochlear promontory.

The CI electrode array will be inserted following one of the two possible techniques while the eCochG will be recording. The surgeon will either manually insert the array using the Oticon Medical stylet and following the surgery guides and recommendations from Oticon Medical or will control the Robotol insertion angle and drive the robotic arm in the same way.

The eCochG trauma index correspond to electrophysiological changes of the cochlear response during the CI electrode insertion, and is calculated from the difference between post-insertion and pre-insertion eCochG measure (in µV).

The hearing loss is calculated from the difference between the post-surgical and pre-surgical hearing thresholds (in dB HL).

The correspondence is calculated from the correlation coefficient between the eCochG trauma index and the hearing loss.

It is expected that a potential damage measured by the eCochG during the surgery have affected auditory threshold.

eCochG trauma index (µV) as a result of manual electrode insertion compared with robotic insertion.

Different behaviors of audiological markers since the cochlea may have suffered from biological cell degradation due to the CI electrode insertion. Allied with cochlear degradation will come increased tissue scar density, subsequently increased resistivity of the biological field to the electrical current. This would imply a cascade effect of electrical and audiological outcomes (higher impedances, higher electrical charges required to evoke a sound or the auditory nerve feedback - eCAP, lower overall performances).