Cochlear Implants for Single Sided Deafness

Cochlear implants (CI) provide auditory information through direct electrical stimulation of the auditory nerve for those individuals with severe to profound hearing loss who obtain little benefit from appropriately fitted conventional hearing aids. Those with profound hearing loss frequently suffer from concomitant tinnitus, the troublesome perception of noises of different frequencies and intensities in the absence of corresponding sound stimuli. In addition to providing auditory information, clinical investigators have noted that cochlear implantation has been found to ameliorate tinnitus in those receiving a cochlear implant for deafness. Investigators have reported tinnitus improvement rates as high as 88% as a beneficial side effect of cochlear implantation placed for the indication of bilateral severe to profound hearing loss.

With tinnitus improvement in cochlear implantation, trials in more than 80 European patients with single sided deafness (SSD) have shown that cochlear implantation can significantly reduce tinnitus in addition to improving sound source localization and speech understanding in noise. Although the sound quality with the CI is poorer than with the normal ear, subjective reports suggest that the sound quality of the normal ear appears to dominate or override the poorer quality of sound from the CI ear. These early trials have demonstrated SSD CI performance superior to acoustic hearing with only one ear, even when compared to the normal ear plus a bone anchored hearing appliance or contralateral routing of sound device. Most promisingly, these SSD patients were greatly satisfied with the CI, reporting that “the world sounds whole again” and “I now forget that I have a deaf ear.” These studies also reported great variability in SSD CI patient outcomes indicating further investigation is needed to determine the indications for CI in SSD. To further understand the therapeutic benefits of cochlear implantation in SSD, the House Ear Clinic is conducting a clinical trial of cochlear implantation for select patients with normal hearing in one ear and profound loss in the other ear.