Performance and Hearing-related Outcomes in Adults Implanted With the CI622D Dexamethasone-eluting Cochlear Implant Compared to Those Implanted With a Standard Cochlear Implant (CI622)

• CI622D (Device): A dexamethasone-eluting Slim Straight electrode
• CI622 (Device): A standard Slim Straight electrode

Primary outcomes

• Difference in the mean impedance between CI622D and CI622 [6 months post-activation]: Mean monopolar impedance measured across the active electrodes of the implant for each participant.

Secondary outcomes

• Incidence of Treatment-Emergent Adverse Events of the CI622D and CI622 [Throughout study (12 months)]: Percentage of the number of participants who experience an adverse event for the CI622D group and the CI622 group
• Difference in the proportion of participants with preservation of low frequency residual hearing with CI622D compared with CI622 [Pre-implantation to 6 months post activation]: The proportion of participants achieving ≤ 30 dB change in the low frequency pure tone average (LFPTA) (250 Hz and 500 Hz). This measure will be applied to the subgroup of participants who have a LFPTA < 80 dB HL at the pre-operative baseline.
• Mean change (within-subject) in word recognition score in the preferred unilateral listening mode in quiet with the CI622D [Pre-implantation to 6 months post-activation]: Change in percent correct word recognition score
• Mean change (within-subject) in word recognition score in the preferred bilateral listening mode in quiet with the CI622D [Pre-implantation to 6 months post-activation]: Change in percent correct word recognition score
• Difference in mean (within-subject) change in word recognition score in the preferred unilateral listening mode in quiet with the CI622D compared with CI622 [Pre-implantation to 12 months post-activation]: Change in percent correct word recognition score
• Difference in mean (within-subject) change in word recognition score in the preferred bilateral listening mode in quiet from pre-implantation to post-activation with CI622D compared with CI622 [Pre-implantation to 12 months post-activation]: Change in percent correct word recognition score
• Difference in mean (within-subject) change in sentence recognition score in noise in the preferred unilateral listening mode from pre-implantation to post-implantation with CI622D compared with CI622 [Pre-implantation to 12 months post-activation]: Change in percent correct sentence recognition score (Matrix test + 10 SNR)
• Difference in mean (within-subject) change in sentence recognition score in noise in the preferred bilateral listening mode from pre-implantation to post-implantation with CI622D compared with CI622 [Pre-implantation to 12 months post-activation]: Change in percent correct sentence recognition score (Matrix test + 10 SNR)
• Characterization of four-point nested impedances and monopolar impedance of the CI622D and CI622 [Activation, 12 months post-activation]: Group mean impedance measured across the active electrodes for four-point nested impedance and MP1+2 impedance for the CI622D and CI622
• Characterization of mean estimated sound processor battery life for CI622D and CI622 [12 months post-activation]: The estimated sound processor battery life (hours per day) as calculated by the programming software
• Difference in mean within-subject changes in global score on the Speech, Spatial, and Qualities of Hearing Scale (SSQ12) between CI622D and CI622 [Pre-implantation to 12 months post-activation]: Speech, Spatial, and Qualities of Hearing Scale global score (SSQ-12). Scores range from 0 to 10, where higher scores indicate greater ability (less hearing disability).
• Difference in mean within-subject changes in global Health Utilities Index III (HUI3) between CI622D and CI622 [Pre-implantation to 12 months post-activation]: Health Utilities Index (HUI 2/3) global score. Scores range from -0.36 to 1.00, where a negative score represents a state "worse than dead" and a top score of 1.00 is "perfect health".

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Aged 18 years or older (at time of consent)
* Clinically established post-linguistic bilateral moderately severe to profound sensorineural hearing loss
* Meets local candidacy criteria for cochlear implantation
* Compromised functional hearing with a hearing aid in the ear to be implanted
* Willing to participate in and comply with all requirements of the protocol, including willingness to be randomised to either arm
* Evidence of pneumococcal vaccination (e.g., Pneumovax) according to local guidelines prior to randomisation
* Candidate is proficient in the language used to assess speech perception performance
* Willing and able to provide written informed consent.

Exclusion Criteria:

* Planned for a partial insertion of the electrode array
* Intra-axial (within the brain) lesions or deafness due to lesions of the acoustic nerve affecting the ear to be implanted
* Middle ear infection (including acute otitis media, chronic otitis media, suppurative otitis media, or serous drainage) in the ear to be implanted either at the time of surgery or within 3 months prior to enrolment
* Active autoimmune disease or active immunosuppressive therapy
* Any of the following in the ear to be implanted within 3 months prior to enrolment: history of prior otologic surgery including grommets, or tympanic membrane perforation
* Previously reported diagnosis of auditory neuropathy, in the ear to be implanted
* Previously reported diagnosis, in the ear to be implanted, of Large Vestibular Aqueduct Syndrome (LVAS), Meniere's disease, or cochlear hydrops
* Ossification, otosclerosis, malformation or any other cochlear anomaly, such as common cavity, that might prevent complete insertion of the electrode array, as confirmed by imaging, in the ear to be implanted
* Current cerebrospinal fluid (CSF) shunts or drains, existing perilymph fistula, temporo- parietal skull fracture or CSF leaks
* History of bacterial meningitis
* Known allergic reaction or contraindication to dexamethasone or corticosteroids
* Severe, or poorer, bilateral sensorineural hearing loss prior to 5 years of age, as reported by the subject
* Severe, or poorer, sensorineural hearing loss of more than 20 years, as reported by the subject, in the ear to be implanted
* Prior cochlear implantation, in either ear
* Medical plan for cochlear implantation during the clinical investigation, contralateral to the ear to be implanted
* Medical or psychological conditions that contraindicate general anaesthesia, surgery or participation in the clinical investigation, as determined by the investigator
* Women who are pregnant
* Unrealistic expectations on the part of the subject, regarding the possible benefits, risks, and limitations that are inherent to the surgical procedure(s) and prosthetic devices as determined by the Investigator
* Additional disabilities that may affect the subject's participation or safety during the clinical investigation, as determined by the Investigator
* Unable or unwilling to comply with the requirements of the clinical investigation as determined by the Investigator
* Investigator site personnel directly affiliated with this study and/or their immediate families; immediate family is defined as spouse, parent, child, or sibling to the study candidate
* Cochlear employees or employees of Contract Research Organisations or contractors engaged by Cochlear for the purposes of this investigation
* Current participation, or participation in another interventional clinical study/trial in the past 30 days, involving an investigational drug or device (unless Cochlear sponsored and determined by investigator or Sponsor to not impact this investigation)
* Subjects recruited at a French site who are not affiliated with social security
* Subjects recruited at a French site who are under legal protection.

• Antje Aschendorff, Principal investigator, University Hospital Freiburg