The purpose of this investigation is to determine the safety and preliminary efficacy of implanting a cochlear implant (CI) in the profoundly deaf ear of an adult with one normal hearing (NH) ear (termed "single-sided deaf" person, or SSD). The potential subjects will have been deafened post-lingually, thus, at one point the now deafened ear did conduct sound from the periphery. The MED-EL CI system will be implanted in ten (10) SSD patients.The long-term goal of this research program is to determine whether the CI, in combination with the NH ear, may provide improved localization ability and better speech understanding in noise, relative to performance before cochlear implantation (i.e., with the NH ear alone). A secondary long-term goal is to determine whether CI stimulation may reduce tinnitus severity, compared to tinnitus experienced prior to cochlear implantation or when the CI is turned off, after implantation.

Inclusion Criteria:

• Is an adult (18 years of age or older)

• English as the primary language

• Able to undergo general anesthesia, as determined by physical examination and written report from the physician

• Receives pneumovax vaccine within 2 weeks of surgery and provides documentation to the principal investigator

• Profoundly/severely deaf in one ear ("implant ear"), as defined by:

  • 3-frequency pure-tone average≥70 dB Hearing Loss
  • Bone conduction thresholds consistent with air conduction thresholds (i.e., no conductive component to the hearing loss)
  • HINT sentence recognition score ≤40% correct, 60 dBA presentation level
  • Post-lingual onset of hearing loss, i.e., after age 6 years of age
  • Hearing loss occurred <10 years prior, as obtained by history

• Normal hearing in one ear ("non-implant ear"), as defined by:

  • 3-frequency PTA ≤25 dB HL
  • No tested frequency air conduction threshold >35 dB HL
  • Bone conduction thresholds consistent with air conduction thresholds
  • Word recognition score ≥80% correct, 60 dBA presentation level
  • HINT sentence recognition score ≥ 80%, 60 dBA presentation level

• Provides informed consent

• Willing and able to follow the study protocol

Exclusion Criteria:

• Retrocochlear pathology resulting from Neurofibromatosis 2, or other types of cranial nerve/brainstem tumors

• Co-existing medical conditions that require radiotherapy of the brainstem and/or auditory cortex

• Any medical contraindication precluding safe administration of general anesthesia, e.g.,

  • Cardiopulmonary disease
  • Renal disease

• Otologic conditions which contraindicate surgery

  • Active middle ear infection
  • Tympanic membrane perforation

• Anatomic abnormalities detected on CT preventing appropriate placement of the stimulator housing in the bone of the skull or placement of the electrode array in the cochlea (e.g., ossification)

• Psychological conditions contraindicating surgery

• Skin or scalp conditions that may preclude attachment of the coil or that may interfere with the use of the coil

• Chronic pain in or around the head

• Current or previous use of an active hearing implant (e.g., bone-anchored hearing aids, cochlear implant, etc.)

• Developmental delays or organic brain dysfunction