Cochlear Implantation for Treatment of Single-sided Deafness

The goal of this study is to further investigate the role of CI in treating unilateral
hearing loss and associated tinnitus. Single-sided deafness (SSD) afflicts approximately
60,000 new patients per year in the United States. The most common causes of these
single-sided losses are sudden sensorineural hearing loss, Meniere's disease, trauma, and
vestibular schwannoma. Patients with SSD face significant difficulty with communicating in
the presence of background noise and in sound localization. Another significant problem for
some SSD patients is tinnitus, which can be incapacitating and for which there are no
therapies available that are considered to be of sufficient reliability to become a standard
of care. Difficulty hearing in background noise and increased tinnitus can lead to
significant frustration in social situations and contribute to increased isolation and a
decreased quality of life. Treatment options for single sided deafness in the United States
include contralateral routing of signals (CROS) hearing aids, bone-anchored hearing aids
(BAHA) and use of assistive devices to improve the signal-to-noise in group situations. The
first two devices take sound from the affected ear and transmit it to the unaffected ear. The
last device consists of having a speaker wear a microphone and routing the signal directly to
the patient's ear at a louder listening level. Although these devices can improve speech
understanding in some patients, studies have shown that use of these devices does not
ameliorate tinnitus or sound localization difficulties. Recent European studies have
demonstrated that cochlear implantation (CI) can provide significant improvements in both
perceived hearing ability and measured speech comprehension and localization in adult and
pediatric patients with unilateral hearing loss. This suggests that CI may be a more
effective option for this patient population than the CROS, BAHA or assistive devices.

Inclusion Criteria:

- 18 years of age or older with the ability to provide informed consent

- English as the primary language

- Medically and psychologically suitable

- Willing to receive/have received meningitis vaccinations

- Able to pay for all care received through the study, either through the subject's
insurance company or through self-pay

- Able to comply with study requirements, including travel to the investigational sites

- Severe to profound sensorineural hearing loss (≥70 dB thresholds between 500 and 4000
Hz) in the worse ear with ≤ 20% CNC word scores

- Duration of single-sided deafness ≥ one year

- Tinnitus localized to the affected ear, both ears, or in the head localized to the
affected ear, both ears, or in the head

- Expected subjects include those with:

- Unilateral hearing loss secondary to viral or bacterial infection, such as meningitis
or labyrinthitis

- Ménière's disease

- Sudden sensorineural hearing loss

- Vascular disease affecting the inner ear

- A combination of any number of the above conditions

Exclusion Criteria:

- Duration of single-sided deafness ≥ ten years

- Pure tone thresholds ≥ 35 dB at 500, 1000, 2000, and 4000 Hz in the better ear

- CNC word scores ≤ 70% in the better ear

- Chronic otitis media in either ear

- Inner ear malformation in either ear

- Autoimmune inner ear disease (fluctuation sensorineural hearing loss in either ear)

- Evidence of retrocochlear pathology, including vestibular schwannoma

- Unilateral tinnitus in the unaffected ear

- Cochlear ossification

- Demonstrated cognitive and/or developmental challenges

- Major depression or anxiety; post-traumatic stress disorder; substance abuse

- Medical or psychological conditions that serve as contraindication to surgery

- Additional handicaps that would prevent or limit participation in evaluations

- Unrealistic patient or family expectations regarding the benefits, risks, and
limitations inherent to the procedure and the prosthetic device

- Pregnant women: The investigators will specifically ask all women of childbearing age
if there is a possibility they are pregnant or trying to become pregnant at the
initial clinic visit; any women who are pregnant or actively trying to become pregnant
will be excluded. In cases that are questionable on the day of planned surgery, a
pregnancy test will be performed as per current Massachusetts Eye & Ear Infirmary
anesthesia pre-operative protocols.