Single-Sided Deafness and Asymmetric Hearing Loss

Inclusion Criteria:

* Five years of age or older at the time of implantation
* Unilateral profound hearing loss, as defined by a pure-tone average (500, 1000, 2000, and 4000 Hz) of 90 dB or greater in the ear to be implanted
* Sensorineural hearing loss in the ear to be implanted, as defined by an air-bone gap less than or equal to 10 dB at two or more frequencies out of 500, 1000, 2000, and 4000 Hz and a diagnosed pathology of the outer or middle ear
* Normal hearing or mild to moderate hearing loss in the non-implanted ear, as defined by a pure-tone average (500, 1000, 2000, and 4000 Hz) of 55 dB or less
* Word recognition in the ear to be implanted of 5% or less on CNC word score in quiet
* Previous experience with an appropriately-fit Contralateral Routing of Signal (CROS) hearing aid, BI-Contralateral Routing of Signal (CROS) hearing aid, bone conduction, or traditional hearing aid, as deemed appropriate by investigator
* Fluent in English

Exclusion Criteria:

* Duration of profound hearing loss of 10 years or more
* Absence of cochlear development or non-functionality of cochlear nerve
* Other retrocochlear hearing loss
* Evidence of severe cochlear malformation (i.e., common cavity or ossification)
* External or middle ear infection
* Suspected developmental or cognitive concern
* Other medical contraindication for surgery or anesthesia