Cochlear Implantation in Cases of Single-Sided Deafness

Single-sided deafness (SSD) can be defined as moderate-to-profound sensorineural hearing loss
with limited speech perception benefit in one ear and normal hearing in the contralateral
ear. Though one ear is within the normal hearing limits, SSD may result in reduced speech
perception in noise, variable abilities on localization tasks, increased subjective report of
hearing handicap, and reduced quality of life.

This patient population cannot utilize conventional amplification due to the severity of the
hearing loss and poor speech discrimination abilities in the affected ear. Current treatment
options include: contralateral routing of the signal (CROS) hearing aids, and bone-conduction
devices. A CROS hearing aid is a two-part system that includes a microphone/transmitter on
the affected ear and a receiver on the normal hearing ear. The microphone/transmitter sends
the acoustic signal from the affected ear to the receiver, which is presented to the normal
hearing ear. Bone-conduction devices utilize a percutaneous, implanted titanium abutment to
send the acoustic signal from the affected side to the normal hearing ear via vibrations. The
goal of both of these technologies is to send the signal from the affected side to the normal
hearing side, thereby leaving the patient in a unilateral listening condition.

Though CROS hearing aids and bone-conduction devices provide the patient with auditory
information from both sides to the better hearing ear, the ability to use binaural cues for
speech perception in noise is variable.

It is of interest whether cochlear implantation of the affected ear would benefit the SSD
population. A cochlear implant is a two-part system, including the internal electrode array
and external speech processor. The internal electrode array is surgically implanted into the
affected cochlea. The external speech processor receives sounds and transmits this signal to
the internal portion. The electrode array presents the acoustic signal via electrical pulses
within the cochlea, which is interpreted by the brain as sound.

Presumably, cochlear implantation may provide the SSD population improvements in speech
perception in the affected ear, which cannot benefit from appropriately fit hearing aids.
Cochlear implantation may provide a benefit over current treatment options in the SSD
population, as it stimulates the auditory pathway on the affected side, thus allowing for
ipsilateral representation of acoustic signals arriving to each ear independently.

The primary goal of this project is to determine whether subjects with SSD experience an
improvement in speech perception, localization, and quality of life with a cochlear implant
as compared to an unaided listening condition. Secondary aims include: 1) a comparison of
speech perception, localization, and quality of life outcomes in the study population to a
SSD control group with long-term listening experience with a current treatment option (i.e.
bone-conduction device), and 2) a within-subject comparison of speech perception and
localization abilities with cochlear implantation versus the bone-conduction test device.

Inclusion Criteria (SSD):

- Unilateral moderate-to-profound sensorineural hearing loss [Unaided residual hearing
thresholds measured from 250-8000 Hertz (Hz) (Pure Tone Average (PTA) ≥70 decibel (dB)
Hearing Level (HL) in the ear to be implanted]

- Normal to mild residual hearing thresholds from 250-8000 Hz in the contralateral ear
(≤35 dB HL at each frequency, 250-8000 Hz)

- Greater than or equal to 18 years of age at implantation

- Duration of moderate-to-profound sensorineural hearing loss less than or equal to 5
years [Either reported by subject or documented in previous audiograms] [Can be less
than or equal to 10 years if the subject consistently utilized hearing technology
(such as a bone conduction device or conventional hearing aid) within the past 5
years]

- Previous experience with a current treatment option for SSD, including a conventional
hearing aid, bone-conduction device, or CROS/BICROS (Bilateral Contralateral Routing
Of the Signal) technology. [At least one month of listening experience with device]
[Dissatisfaction with and/or discontinued use of current treatment option due to:
insufficient gain, poor sound quality, and/or lack of perceived benefit]

- Aided word recognition in the ear to be implanted of 60% or less as measured with
Consonant-Nucleus-Consonant (CNC) words (50-word list) [When listening with an
appropriately fit hearing aid and masking applied to the contralateral ear] [Aided
testing will be conducted in a sound-proof booth with the subject seated 1 meter from
the sound source, facing 0° azimuth. Recorded materials will be presented at 60 dB
Sound Pressure Level (SPL).] [The hearing aid output will be measured using National
Acoustic Laboratory-NonLinear (NAL-NL1) targets.]

- Realistic expectations

- Willing to obtain recommended meningitis vaccinations per Center for Disease Control
(CDC) recommendations

- No reported cognitive issues [Pass the Mini Mental State Examination (MMSE) screener]

- Able and willing to comply with study requirements, including travel to
investigational site and study-related activities

Exclusion Criteria (SSD):

- Non-native English speaker [Speech perception materials are presented in English]

- Conductive hearing loss in either ear

- Compromised auditory nerve, including those with a history of vestibular schwannoma

- Ossification

- Inability to participate in follow-up procedures (i.e., unwillingness, geographic
location)

- History of meningitis, autoimmune disease, or any medical condition that
contraindicate middle or inner ear surgery or anesthesia

- Meniere's disease with intractable vertigo

- Trauma that precludes inner ear surgery

- Case of sudden sensorineural hearing loss that has not been first evaluated by a
physician

- Pregnancy [Subjects who are pregnant or become pregnant prior to surgery are excluded
due to the potential risk of anesthesia to an unborn child.] [Subjects who become
pregnant after surgery may continue to participate in study procedures]

- Tinnitus as the primary purpose for seeking cochlear implantation

- Subject obtains a severe or catastrophic score on the Tinnitus Handicap Inventory
(Newman, Jacobson & Spitzer, 1996).

Inclusion Criteria (asymmetric hearing loss):

a. Ear to be implanted i. Moderate-to-profound sensorineural hearing loss ii. PTA ≥70 dB HL
iii. Aided word recognition of 60% or less as measured with CNC words (50-word list).

b. Contralateral ear i. PTA ≥35 and ≤55 dB HL ii. Aided word recognition of 80% or more as
measured with CNC words (50-word list).

iii. Use of conventional amplification c. Greater than or equal to 18 years of age at
implantation d. Duration of moderate-to-profound sensorineural hearing loss in the ear to
be implanted is less than or equal to 5 years [Either reported by subject or documented in
previous audiograms. Can be up to 10 years if the subject consistently utilized hearing
technology in the ear to be implanted (such as a bone conduction device or conventional
hearing aid) within the past 5 years] e. Previous experience with a current treatment
option for asymmetric hearing loss, including a conventional hearing aid, bone-conduction
device, or CROS/BiCROS technology. [At least one month of listening experience with device.
Dissatisfaction with and/or discontinued use of current treatment option due to:
insufficient gain, poor sound quality, and/or lack of perceived benefit.] f. Realistic
expectations g. Willing to obtain recommended meningitis vaccinations per CDC
recommendations h. No reported cognitive issues [Pass the Mini Mental State Examination
(MMSE) screener] i. Able and willing to comply with study requirements, including travel to
investigational site and study-related activities

Exclusion Criteria (Asymmetric hearing loss):

1. Non-English speaker [Speech perception materials are presented in English]

2. Medical condition considered a contraindication to undergoing cochlear implantation

3. Conductive hearing loss in either ear

4. Compromised auditory nerve, including those with a history of vestibular schwannoma

5. Ossification

6. Inability to participate in follow-up procedures (i.e., unwillingness, geographic
location)

7. History of meningitis, autoimmune disease, or any medical condition that
contraindicate middle or inner ear surgery or anesthesia

8. Meniere's disease with intractable vertigo

9. Trauma that precludes inner ear surgery

10. Case of sudden sensorineural hearing loss that has not been first evaluated by a
physician

11. Pregnancy [Subjects who are pregnant or become pregnant prior to surgery are excluded
due to the potential risk of anesthesia to an unborn child. Subjects who become
pregnant after surgery may continue to participate in study procedures]

12. Tinnitus as the primary purpose for seeking cochlear implantation

13. Subject obtains a severe or catastrophic score on the Tinnitus Handicap Inventory
(Newman, Jacobson & Spitzer, 1996).