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.
