Clinical Study of Cochlear Implants in Adults With Asymmetrical Hearing Loss

The objective of this study is to investigate benefits of binaural hearing for non-traditional cochlear implant candidates (with Asymmetric Hearing Loss). Asymmetric candidates are patients with severe to profound hearing loss in one ear and better hearing in the other ear. (One ear is deaf and the other ear has better hearing and in most cases uses a hearing aid.) The investigators hypothesize that cochlear implantation of the poorer ear provides a functional increase in word and sentence understanding in quiet or noise, perceived benefit, localization ability, and other measures of auditory performance relative to use of the better hearing ear alone.

Multichannel cochlear implants have been highly successful in restoring speech understanding in adults and children who have congenital or acquired bilateral profound or severe-to-profound sensorineural (permanent) hearing loss. As implant technology has continued to develop and post-implant performance of patients has improved, the patient selection criteria has broadened to include patients with less severe hearing loss. Further, results from studies where patients received bilateral cochlear implants have demonstrated not only improved performance but the feasibility of integrating signals from both ears.

In contrast to persons with bilateral severe-to-profound hearing loss, persons who have only one ear with profound or severe-to-profound hearing loss and the other ear with substantially less hearing loss have not, to date, been considered cochlear implant candidates. This is because it has been assumed they will do well enough with a conventional hearing aid in the better ear. A problem with this assumption is that even with an appropriately fit better ear hearing aid, many of these hearing-impaired individuals still experience significant difficulties in speech understanding in their everyday listening environments, along with significant communication handicaps that interfere with their employment and quality of life.

Previous studies that have examined the performance of patients who have more symmetrical hearing loss and who wear a cochlear implant on one ear and a power hearing aid on the other ear, have illustrated that the two inputs can be combined and provide binaural hearing benefits. It is hypothesized in this study that patients with an asymmetrical sensorineural hearing loss may also receive significant binaural benefit from having a cochlear implant on the poorer ear along with an appropriately fit hearing aid on the better ear. That is, this study examines whether patients with asymmetrical sensorineural hearing loss can utilize both types of input (acoustic to one ear and electric to the other) effectively, and combine them to receive binaural hearing assistance for improving speech understanding, localization ability, and patient satisfaction.

Eligibility Criteria:
Inclusion Criteria:

* 18 years of age or older at time of surgery
* The poorer ear (implant ear) will have a severe-to-profound hearing loss and meet current cochlear implant candidacy criteria.
* The better ear (contralateral ear) will have hearing levels less than current cochlear implant candidacy criteria and stable/non-fluctuating hearing levels for at least the previous year
* Normal/patent cochlear anatomy
* Fluent in English
* Desire to have more functional binaural hearing and willingness to comply with all of the study requirements

Exclusion Criteria:

* Medical or psychological conditions that contraindicate undergoing surgery
* Additional handicaps that would prevent or restrict participation in the audiological evaluations
* Ossification or any other cochlear anomaly that might prevent complete insertion of the electrode array
* Hearing loss of neural or central origin, including auditory neuropathy
* Chronic and severe tinnitus in the ear to be implanted
* Unwillingness or inability to comply with all investigational requirements