Cochlear Implants for Adults With Single-sided Deafness

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