The main objective of this study is to evaluate the correspondence between eCochG and residual hearing by adding two modifications. First, a novel technique for placing and maintaining the probe in place during the whole insertion will be used. Second, a new metric for estimating the eCochG response will be evaluated (eCochG trauma index). The secondary objective is to find other markers of the cochlear trauma insertion associated to eCochG measures. This will be used to evaluate to which extend a traumatic insertion will be deleterious for the patient's post-operative hearing, and ultimately to prevent trauma to the inner ear. Finally, the potential differences in cochlear trauma resulting of the electrode array insertion from two different surgery techniques will be investigated; Either using a manual insertion or using a robotic arm that will drive the insertion automatically.
Main study procedures and assessments: * Visit 1 (D-30+/-14) INCLUSION: subject information/consent, inclusion/exclusion criteria, CT-scan, Tonal audiometry * Visit 2 (D0+/-14) COCHLEAR IMPLANT SURGERY: CT-scan, Intra-op eCochG, eCAP, Impedance * Visit 3 (D+30+/-14) FOLLOW-UP 1 MONTH: Tonal audiometry, Impedance, Fitting maps * Visit 4 (D+60+/-14) FOLLOW-UP 2 MONTH: Tonal audiometry, Impedance, Fitting maps, Phonemes * Visit 5 (D+90+/-14) FOLLOW-UP 3 MONTH: Tonal audiometry, Impedance, Fitting maps, Phonemes
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
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.
Correlation coefficient between the eCochG trauma index (in µV) and the residual hearing (in dB HL).
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.
Time frame: Through study completion, an average of 2 years
Significant decrease of eCochG trauma index (in µV) for electrode array insertion performed manually compared to robotic.
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).
Time frame: Through study completion, average of 2 years
Correlation coefficient between the eCochG trauma index (in µV) and a misplacement of the electrode array inside the cochlea based on CT scan.
The misplacement will be quantified with the cochlear coverage (in %) and a subjective assessment of the Eschraghi trauma index for exploratory purpose. eCochG trauma index (µV) with placement of the CI electrode array in the cochlea (using Pre and Post surgical CT scans).
Time frame: Through study completion, average of 2 years
Correlation coefficient between the eCochG trauma index (in nV) with the electrical charges (in nC) required to elicit eCAP threshold.
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eCochG trauma index (µV) with eCAP thresholds (nC).
Time frame: Through study completion, average of 2 years
Correlation coefficient between the eCochG trauma index (in nV) with impedance measurement (in Ω).
eCochG trauma index (µV) with CI electrode impedances (Ohm).
Time frame: Through study completion, average of 2 years
Correlation coefficient between the eCochG trauma index (in nV) with fitting map electrical charges (in nC), and slopes of their growth functions.
eCochG trauma index (µV) with electrical charge (nC) measured on the patient CI fitting map.
Time frame: Through study completion, average of 2 years
Correlation coefficient between the eCochG trauma index (in nV) with scores of phonemes discrimination (%).
eCochG trauma index (µV) with scores (in %) of phonemes recognition.
Time frame: Through study completion, average of 2 years