Single-Sided Deafness and Cochlea Implantation

Single-Sided Deafness and Cochlea Implantation

Single-sided deafness (SSD) is a severe to profound loss of hearing ability in one ear with conserved audiometric verges in the contralateral ear. Over the last years, cochlear implantation (CI) surgery has been of a significant improvement in both children adult patients who have single-sided deafness (SSD).

Historical Treatment for Single-Sided Deafness and their disadvantages

People relied on amplification devices that transmit sound through the air from the affected year to the normal ear in order to restore binaural hearing. To conduct contralateral routing of sounds (CROS), bone conducting technologies and SoundBite dental conduction devices were used in transferring sound from the deafened ear to the normal ear (Friedmann et al 2016). CROSS hearing aids were the first intervention for SSD due to its inexpensiveness.

Although CROSS hearing aid had taken steps in allowing sound awareness from the deaf ear, the success of CROSS hearing aid was faced with a lot of drawbacks.

Some of the disadvantages that CROSS encountered include the need to occlude the better ear canal, and a relatively weak overall improvement in hearing experience, mostly in sound localization and noise hearing. Transcranial CROSS transmitted signals received by the air conduction hearing aid in the affected ear to the contralateral cochlea through bone conduction (Friedmann et al 2016). However, transaction CROSS use was never established due to the limited number of trials with little sample sizes, and conflicting data in regards to speed perception improvement, patients satisfaction based on air condition CROSS, and sound localization.

Advantages of Cochlea Implantation in Single Sided Deafness

Despite the steps taken by CROSS in improving localization, and hearing in noise, cochlear implantation (CI) has been more successful in treatment for SSD. Cochlear implantation for SSD began during the early 2000s as an experimental treatment for intractable and incapacitating tinnitus (Zeitler Sladen et al 2017). After the first experiment with CI, users reported improvements in sound localization and speed perception in multifaceted listening environments. Individuals living with tinnitus suffer hearing loss to a level of 85 per cent, and 85 per cent hearing improvement were reported on CI in tinnitus patients.

When noise and speed are presented in different configurations, the real benefit of CI in SSD becomes apparent. Tevora-Vieira reported a better speech comprehension with CI-on versus CI-off when noise and speech were presented directly in front of the listener (Zeitler Sladen, 2017). In the CI-on, Tavora reported improvements in speech understanding in three different conditions: speed in front and noise at the NH ear, speed, and speech in front, noise in the NH ear and speed at the CI ear. CI was effective when speech was presented either to the SSD ear or in front, and the noise was presented to the NH ear.

Irrespective of most studies reporting significant gains with speech comprehension in noisy environments, the utility of CI in SSD for all patients remain controversial. Roland said that one out of three patients receiving CI for SSD showed improvements in free field comprehension test when comparing postoperative CI scores to preoperative scores (Zeitler Sladen, DeJong, Torres, Dorman & Carlson, 2017). Vlastarakos reported that CI insertion in the SSD ear led to good speech perception when speech was presented direct to the SSD ear, while concurrent noise is presented in front or at the regular hearing.

Impact of Cochlea in Sound Localization

CI improves SSD subject’s ability in identifying sound sources. Binaural benefit from CI was limited in patients with limited localization ability in the HA- only condition. Patients implanted for SSD can recognize which side sound were being presented. Firszt found improvements in localization with CI compared to HA-only localization. Also, patients with CI performed better with their CI when localizing than in CROS conditions.

Localization benefits are better in adults than in children. Three children aged 4, 10, 12 respectively were taken for study. Localization of the two older children was assessed through OLSA sentences presented in 7 equidistant speakers (Finbow et al 2015). Children with SSD should be implanted immediately because the best outcomes in SSD associates early children implantation. Many children with SSD have shown a delay in speech and language understanding and difficulty in academics. Children with lingual acquired SSD who were implanted with CI performed empirically better with localization, speed in noise, and hearing ability (Finbow et al 2015). Children with unilateral deafened ear do not respond to amplification, and cochlear implants have shown significant benefits in academics, speech, and quality of life.

Factors to be taken into account

Policy makers can include SSD as an indication for cochlear implementation due to CI’s great impact in reducing single-sided deafnenes. Several factors should be considered in order to curb post-implant outcomes of SSD defects more effectively. Primary contributing factors to post-implant outcomes are the attempts in preserving hearing during implantation, the inclusion of therapy during the postoperative auditory neuroplastic window, and the use of other aural amplifiers. Maintaining of hearing through the surgical techniques can reduce trauma in the cochlea, and ultimately help in speech and localization benefits. Postoperatively, the auditory cortex shows the most significant extent of reorganization during the first few months of post activation, and it is necessary to maintain the implanted subjects’ motivation high during the critical period of speech analysis (Finbow, 2015). Additionally, combined electro-acoustic stimulation with an acoustic amplifier can be beneficial in different types of people. In cases where patients suffer from preserved low-frequency hearing, an acoustic amplifier implanted in the affected ear may assist in detecting low-frequency tones post-implant. Combining an amplifier in the affected ear is associated with increased hearing abilities concerning speech in both children and adults.

Conclusion

Many years ago, people relied on amplification devices that transmit sound through the air from the affected year to the normal ear to restore binaural hearing. Some of the drawbacks that were faced by CROSS include the need to occlude the better ear canal, and a relatively weak overall improvement in hearing experience. Despite the steps taken by CROSS in improving localization, and hearing in noise, cochlear implantation (CI) has been more successful in treatment for SSD. Cochlear implantation for SSD began during the early 2000s as an experimental treatment for intractable and incapacitating tinnitus. CI improves SSD subject’s ability in identifying sound sources. Binaural benefit from CI was limited in patients with limited localization ability in the HA- only condition. Primary contributing factors to post-implant outcomes are the attempts in preserving hearing during implantation, the inclusion of therapy during the postoperative auditory neuroplastic window, and the use of other aural amplifiers.

References

Finbow, J., Bance, M., Aiken, S., Gulliver, M., Verge, J., & Caissie, R. (2015). A comparison      between wireless CROS and bone-anchored hearing devices for single-sided deafness: a     pilot study. Otology & Neurotology, 36(5), 819-825.

Friedmann, D. R., Ahmed, O. H., McMenomey, S. O., Shapiro, W. H., Waltzman, S. B., & Roland Jr, J. T. (2016). Single-sided deafness cochlear implantation: candidacy, evaluation, and    outcomes in children and adults. Otology & Neurotology, 37(2), e154-e160.

Zeitler, D. M., Sladen, D. P., DeJong, M. D., Torres, J. H., Dorman, M. F., & Carlson, M. L.        (2019). Cochlear implantation for single-sided deafness in children and       adolescents. International journal of pediatric otorhinolaryngology, 118, 128-133.