This is a prospective multicenter multinational randomized control trial. The duration of the study for the individual patient will be approximately 1 year (pre-operative assessments, 1 week, 3 months and 12 months follow-up assessments). Participants will be randomized to one of two surgical approaches: eRW or CO, with a 1:1 allocation in a parallel design.
Rationale: Preserving residual hearing in cochlear implant (CI) surgery has gained significant attention. It not only signifies minimally invasive implantation but also supports natural sound perception and enables electrical-acoustic stimulation, enhancing sound localization, music appreciation, and speech recognition in noisy environments. Using the Cochlear™ Nucleus® CI with Slim Modiolar electrode (Cochlear Ltd., Sydney, Australia), potential sites of residual hearing loss in surgery include approaches to the cochlear lumen, potential damage during entry, and damage during electrode insertion. Studies comparing different surgical approaches (cochleostomy (CO) and extended round window (eRW)) show varied results. Electrocochleography (ECochG) can be used to indicate intracochlear damage during electrode insertion, however, the variability observed in ECochG responses during cochlear implantation remains significant. Moreover, ECochG has not yet been used to monitor cochlear functions throughout every phase of surgery, including the insertion of the sheath or stabilization of the electrode lead. Objective: The aim of this study is to investigate whether the type of surgical approach to the cochlea; CO or eRW using the CI632 affects the final residual hearing and secondarily, intracochlear trauma and electrode position, as determined by pure tone audiometry, EcochG and imaging. Study population: Adult CI candidates with post-lingual onset of severe to profound hearing loss, who are scheduled to receive a Nucleus CI632 with a slim modiolar electrode array and have a preoperative audiometric low-frequency average air conduction threshold of \<80 decibel (dB) hearing level at 500 Hz in the ear to be implanted.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
50
Surgical placement of a cochlear implant electrode array
Radboud University Medical Center
Nijmegen, Netherlands
RECRUITINGResidual hearing
The difference in residual hearing per group (eRW or CO) between pre- and postoperative pure tone thresholds, averaged at 500, 750 and 1000 Hz (PTAlow).
Time frame: 3-months postoperatively
ECochG thresholds after multiple surgery stages
ECochG thresholds with a promontory recording electrode after the following surgery stages: a) posterior tympanotomy (baseline), b) drilling for RW membrane exposure, c) completion of the approach to implantation (CO or eRW), d) sheath insertion, e) electrode array insertion, f) sheath withdrawal, and g) positioning of the electrode lead.
Time frame: Intraoperatively
Intracochlear electrode position
The position of electrode contacts relative to the modiolus and the angular insertion depth (AID), as assessed with pre- and post-operative CT-scan.
Time frame: 3-months postoperatively
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