Chapter 16 - Cochlear implants

Sensorineural hearing loss

Hearing loss is a major health and economic burden on society. For example, it is estimated that 22% of Europeans are affected by a hearing loss, costing the community €284 billion annually (http://www.hear-it.org/multimedia/Hear_It_Report_October_2006.pdf). Hearing impairment can result in significant communication disorders including poor development of spoken and written language in children, leading to important educational, social and vocational ramifications that can adversely affect

Cochlear implants

The development of CIs has dramatically changed the clinical management of patients with a profound, bilateral SNHL. CIs electrically stimulate discrete populations of residual SGNs via an electrode array located in the scala tympani, thereby taking advantage of the known tonotopic organization of the cochlea by dividing speech into discrete frequency bands mapped to specific electrodes.

Central auditory prostheses

Although cochlear implants have clearly demonstrated clinical benefit for severe–profoundly deaf patients (Bond et al., 2009), there have been numerous attempts to develop auditory prostheses based on electrical stimulation of the central auditory pathway. Studies of the mammalian auditory pathway have demonstrated well organized cochleotopic maps within the major auditory nuclei from the cochlear nucleus to the auditory cortex (Irvine, 1992), implying that appropriately positioned electrode

Future directions

There are a number of active areas of research directed towards improving the clinical performance of CI users. This research covers a wide spectrum of hearing ability ranging from patients with a profound SNHL to those with useful levels of acoustic hearing and includes: combined electric/acoustic stimulation (Gantz et al., 2000, Von Ilberg et al., 2011); bilateral cochlear implantation for improved sound localization and speech perception in noise (Van Hoesel and Tyler, 2003, Litovsky, 2011);

Conclusions

This chapter reviews the biological basis of CIs and provides an overview of both existing technologies and future research that will impact on the field. CIs have made a major impact on the quality of life of severe-profoundly deaf adults and children. With this clinical success come even broader patient selection criteria both in terms of age at implantation and hearing ability. The broadening of selection criteria will influence CI research in the future, including the development of

Acknowledgments

The authors would like to thank their colleagues within the Bionics Institute for useful discussions on aspects of this work.

We gratefully acknowledge the following financial contributions to this work: National Institutes of Health (HHS-N-263-2007-00053-C), the Garnett Passe and Rodney Williams Memorial Foundation, and the National Health and Medical Research Council of Australia. The Bionics Institute also acknowledges the support it receives from the Victorian Government through its