Cochlear implants have been used for several decades, with major technological advances. However, adjustment can be difficult for patients who have to get used to a new sound that is electrical rather than acoustic. In general, adjustment is based on the patient's responses: the patient must inform the technician of their sensations in order to determine the sound level that is comfortable for them (MCL: maximum comfortable level).

The adjustment therefore depends on a subjective assessment. The aim of the adjustments is to make the sound pleasant while increasing the stimulation level to the maximum tolerated level in order to achieve good listening dynamics. Objective indicators would therefore be useful in improving the accuracy of the adjustments. The objective measurements that can be taken are:

• Electrical compound action potentials (eCAP)
• Electrical auditory brainstem response (eABR)
• Electrical stapedius reflex threshold (eSRT).

Observational study of adult patients who are going to receive or have received a cochlear implant. In fact, two groups of patients will be studied:

Incident case cohort: patients included in the cohort will be followed for one year after surgery.

Data will be collected at each postoperative follow-up visit (M1, M3, M6, M9, M12) to monitor their progress. Each objective measurement will be taken on at least three electrodes: on the left, right, and central electrodes. Data will be collected at each postoperative follow-up visit (M1, M3, M6, M9, M12) in order to monitor their progress. Each objective measurement will be taken on at least three electrodes: on the basal, median, and apical parts of the electrode array. Stimulation will be configured using the software normally used to adjust the implant.

Responses are collected:

• for eCAPs: via the same software
• for eABRs: using an auditory evoked potential recording device synchronized with the implant stimulations
• for eSRTs: using a tympanometer with the probe inserted into the external auditory canal on the same side or the opposite side to the stimulation. Cross-sectional sample of prevalent cases: The same measurements will be taken in patients who had a cochlear implant some time ago (evaluation more than one year after surgery). The measurements will be taken only once during their annual check-up. This population will enable us to compare data from patients who have recently had an implant with data from a population that already has a minimum of experience and adaptation to the implant.

Inclusion Criteria:

Incident case cohort:

• Age ≥ 18 years (18 years or older)
• Scheduled for first-time unilateral cochlear implantation within the next 3 months
• Informed about the study and did not object (non-opposition)

Cross-sectional sample of prevalent cases:

• Age ≥ 18 years (18 years or older)
• Underwent unilateral cochlear implantation more than 1 year ago
• Has used the implant for more than 1 year (interval between implantation surgery and study inclusion > 1 year)
• Informed about the study and did not object (non-opposition)

Exclusion Criteria:

Exclusion Criteria - applies to both the incident case cohort and the cross-sectional sample of prevalent cases:

• Prior middle or inner ear surgery
• Cognitive impairment or insufficient comprehension of French that would prevent understanding of study procedures or accurate measurement of comfort thresholds during programming
• Peripheral facial palsy
• Bilateral cochlear implantation
• Patient under legal guardianship/court-ordered protection

Additional exclusion - cross-sectional sample of prevalent cases only:

- More than half of the electrodes not inserted (i.e., <50% electrode insertion)

Secondary exclusion criteria - Incident case cohort:

• More than half of the electrodes not inserted (<50% electrode insertion)
• Postoperative peripheral facial nerve palsy following the implantation surgery

Adult patients who are going to receive or have received a cochlear implant.