Clinical Utility of Residual Hearing in the Cochlear Implant Ear

Abstract
A major concern in cochlear implantation is the loss of residual hearing associated with surgery. Hence,
many candidates are faced with the decision to relinquish their remaining acoustic hearing in exchange for
electric hearing via the cochlear implant (CI). A potential solution is a stimulation strategy termed Electric acoustic
stimulation (EAS), which has been used to describe the ipsilateral combination of electric hearing via a CI and
acoustic hearing via a hearing aid. This, however, requires preservation of residual hearing, which has been
possible but inconsistent. A new technology to potentially improve hearing preservation, intraoperative
electrocochleography (ECochG), has been introduced and it was recently implemented into commercially
available CI systems.
Studies comparing EAS with conventional CI have were able to demonstrate a performance benefit of EAS.
However, these studies have compared conventional CI candidates to EAS candidates with more residual
hearing. Thus, the clinical importance of residual acoustic hearing in cochlear implantation (CI) remains unclear.
Therefore, the present protocol seeks to answer two critical clinical questions in cochlear implantation:
(Specific Aim 1) Are cochlear implant electrode insertions using Electrocochleography (ECochG) feedback better
for achieving hearing preservation (HP) and (Specific Aim 2) is combined ipsilateral EAS better than non-HP
(conventional) cochlear implantation among CI candidates with substantial residual hearing (EAS candidates).
We plan to enroll and randomize EAS candidates in seven large US centers. Patients will be assigned to
either intraoperative ECochG monitoring or conventional CI electrode insertions. Hearing preservation and other
performance outcomes will be recorded and analyzed between the groups to assess the clinical value of
intraoperative monitoring. Further, subjects from both groups will have either useable or no useable residual
hearing as the result of surgery. Audiometric and patient reported performance outcomes will be obtained and
evaluated for 24 months following initial stimulation.
In summary, the present proposal aims to answer two critical clinical questions: Is CI electrode insertion
based on ECochG better for achieving HP? and Is EAS better than conventional cochlear implantation among
EAS candidates? A positive answer to these questions will inform an evidence-based clinical practice for EAS
candidates that uses longer electrodes, broadens the candidate pool by including patients with greater levels of
residual hearing, and potentially improves outcomes following CI.

Grant Number: 5U01DC018920-05
NIH Institute/Center: NIH
Principal Investigator: Oliver Adunka