The objective of this feasibility study is to obtain preliminary safety and efficacy data associated with cochlear implantation in individuals with severe to profound sensorineural hearing loss contralateral to an ear with normal, or near-normal, hearing. The hypothesis is that restoration of hearing in the deafened ear will result in improved speech perception in the treated ear and advantages related to restoration of hearing to both ears.

Inclusion Criteria:

1. Ability to provide informed consent.

2. Eighteen years-of-age or older at the time of implantation.

3. Presence of single-sided deafness as follows:

   1. Poorer ear (ear to be implanted):

      • severe to profound sensorineural hearing loss, defined as pure-tone thresholds 80 dB HL or greater for the frequencies 500, 1000, 2000, 3000, and 4000 Hz.
      • Monosyllabic word understanding, as measured using the CNC Word Test at 60 dBA under earphones, less than or equal to 10%.

   2. Better ear (contralateral ear):

      • Normal or near-normal hearing, defined as pure-tone thresholds no poorer than 30 dB HL at 250, 500, 1000, 2000, and 3000 Hz and no poorer than 40 dB HL at 4000 Hz.
      • Monosyllabic word understanding, as measured using the CNC Word Test at 60 dBA under earphones, of greater than or equal to 90%.

4. Duration of severe to profound sensorineural hearing loss of at least 6 months (to ensure stability of hearing loss) but no greater than 10 years.

5. English spoken as a primary language.

Exclusion Criteria:

1. Alleviation of tinnitus as the stated primary or sole motivation for seeking implantation by the subject and/or investigator.
2. Actively using an implantable device in the poorer ear.
3. Onset of severe to profound hearing loss < 6 years-of-age.
4. Evidence of active middle-ear pathology based on otologic examination and/or immittance testing.
5. Medical or psychological conditions that contraindicate undergoing surgery.
6. Ossification or any other cochlear anomaly at the implant ear that might prevent complete insertion of the electrode array.
7. Hearing loss of neural or central origin, including auditory neuropathy.
8. Unrealistic expectations on the part of the subject regarding the possible benefits, risks, and limitations inherent to the surgical procedure and prosthetic device.
9. Unwillingness and/or inability of the candidate to comply with all investigational requirements including, but not limited to, study protocol and surgical procedure, as determined by the investigator.

12 months

Suspected allergic response to a drug used during the anesthesia procedure.