Hearing and Structure Preservation Via ECochG

Cochlear implantation is a highly effective method of rehabilitating hearing in individuals with severe to profound hearing loss. One current hurdle to optimising hearing outcomes following cochlear implantation is the unavoidable trauma caused to the inner ear during implant surgery. This damage can mean residual hearing that would remain valuable following implantation is lost. Various approaches have been trialed to preserve hearing during implantation surgery, modifying implantation technique and administering steroids. Electrocochleography (ECochG) is a monitoring technique that can be used during electrode insertion to record inner ear structural integrity and function.

The PRESERVE trial is an international, multi-centre, randomised controlled trial. The trial will randomly allocate adult cochlear implant recipients to undergo implantation surgery either with ECochG-guidance, or via the standard approach without guidance. Participants will be blinded, meaning they will not know which group they will be allocated to. Where ECochG is used, evidence of damage during insertion detected with the monitoring will trigger the surgeon to follow a corrective pathway. All other aspects of surgery and post operative care will follow standard clinical pathways for both groups.

Participants will have their natural hearing measured preoperatively, and 3- and 6-months following implant activation. The change in natural hearing thresholds at different frequencies, and the degree of hearing preservation will then be calculated and compared between the standard surgery and ECochG-guided group. Using their cochlear implant, understanding of speech will also be measured and compared between groups. In addition, participants will undergo a second CT scan following implantation surgery, and this will be compared to the routine pre-operative imaging to assess both the location of the implant electrode, and structural preservation of the cochlear. Throughout the study participants will remain under the care of their routine medical team.

Inclusion criteria

• Aged 18 years of age or older
• Within cochlear implant inclusion criteria by local regulations/guidelines at the time of implantation
• Severe to profound hearing loss (average air conduction unaided hearing threshold of ≥ 70 dB HL for 500, 1000, 2000 and 4000 Hz) in the ear to be implanted
• Air conduction unaided hearing threshold ≤ 70 dB HL at 500 Hz in the ear to be implanted
• Less than 15 years of severe to profound deafness on the implant ear prior to surgery
• Post-lingually acquired hearing loss in the ear to be implanted
• Normal cochlear anatomy as confirmed by pre-operative imaging in the ear to be implanted
• Listed for an Advanced Bionics HiRes Ultra (3D) HiFocus SlimJ electrode array
• Listed for cochlear implant surgery under general anaesthesia
• Fluent in local language
• Given informed consent to participate in the study

Exclusion criteria

• Abnormal cochlear anatomy (including ossification) as identified by pre-operative radiological evaluation in the ear to be implanted
• Any pre-existing cochlear or middle ear pathology, such as otosclerosis, cholesteatoma, or previous middle ear surgery in the ear to be implanted
• Any medical conditions that would increase the risk of local complications during cochlear implantation, such as autoimmune diseases or active local infections
• Diagnosis of auditory spectrum neuropathy disorder
• Deafness due to lesions of the acoustic nerve or central auditory pathway
• Deafened by meningitis
• Single sided deafness (average for 500, 1000, 2000 and 4000 Hz in the better ear ≤ 30 dB HL)
• Asymmetric hearing loss (average for 500, 1000, 2000 and 4000 Hz in the better ear > 30 dB HL and ≤ 55 dB HL)
• History of previous cochlear implantation/re-implantation on either ear
• Any contraindications to computed tomography (CT) scans
• Concurrent participation in other cochlear implant related studies