By: Sam Spink

Cochlear Implant

What is it?

• System of external and internal devices that aim to restore hearing to sensorineural hearing loss patients

• Both pre- and post-lingual hearing loss • Does not restore functionality to natural cochlea;

stimulates auditory nerve directly• Restored hearing is not exactly like natural hearing

Problem being solved

• Sensorineural hearing loss• Most common form of hearing loss • Damage to either brain, auditory nerve, but most commonly

sensory cells of cochlea (cochlear implant used for patients with this type)

• 1.2 million Americans affected by hearing loss; sensorineural most common form

• Functioning cochlea: vibrations cause fluid movement, which is sensed by hair cells of cochlea causing action potential firing to auditory nerve• These cells don’t function in those with cochlear implants

Current Technology

• 5 major components• External devices:

• Microphone-wraps around front of ear

• Speech processor-behind ear; attached to microphone

• Transmitter-above processor

• Internal devices:• Receiver/stimulator-across

from transmitter• Electrode array-placed on

natural cochlea; wired to receiver

How it works

• Microphone picks up sound, sends it to speech processor

• Speech processor filters sound, converts to electrical signals through fast Fourier Transforms

• Transmitter wirelessly sends signals to receiver/stimulator

• Receiver/stimulator sends electrical current according to received signal to electrodes

• Electrodes stimulate auditory nerve

Effectiveness

• One study shows ability of cochlear implant recipients to identify sentences over telephone with 82 % success rate (pre-lingual) and 70% success rate (post-lingual)• With an adaptor increases to 93% and 88%, respectively

• Speech development in children• For each 6 month period over first 30 months after receiving

implant, subjects’ increase in “language age” was about double that of subjects without implants

• Some performed at around same level as non-impaired

Limitations

• Requires intense therapy post-implantation to achieve high level of speech comprehension (especially for post-lingual patients)

• Device has trouble processing late echoing effects that go unnoticed by non-impaired ears

• Costs between $45,000 and $125,000• Surgical complications include infection, facial muscle

weakness, facial paralysis, damaged vestibular system, loss of all residual hearing

Future Direction

• Improvement in surgical techniques to keep residual hearing intact• If cure came about, patients would want what natural hearing still

remained

• Different electrode arrangements• Longer electrode arrays have shown potential to increase pitch

range • Variations in electrode spacing at different points on the cochlea

could improve sound quality

References

• Hu, Y. and Kokkinakis, K. (2014). Effects of early and late reflections on intelligibility of reverberated speech by cochlear implant listeners. The Journal of the Acoustical Society of America, 135(1), pp.22--28.

• Landsberger, D., Mertens, G., Punte, A. and Van De Heyning, P. (2014). Perceptual changes in place of stimulation with long cochlear implant electrode arrays. The Journal of the Acoustical Society of America, 135(2), pp.75--81.

• Nidcd.nih.gov, (2014). Cochlear Implants. [online] Available at: http://www.nidcd.nih.gov/health/hearing/pages/coch.aspx [Accessed 27 Sep. 2014].

• Rigotti, P., Costa, O., Bevilacqua, M., Nascimento, L. and Alvarenga, K. (2013). Assessment of telephone speech perception in individuals who received cochlear implant in the period 1993-2003. 25(5), pp.400--406.

• Svirsky, M., Robbins, A., Kirk, K., Pisoni, D. and Miyamoto, R. (2000). Language development in profoundly deaf children with cochlear implants. Psychological science, 11(2), pp.153--158.

• Wikipedia, (2014). Cochlear implant. [online] Available at: http://en.wikipedia.org/wiki/Cochlear_implant [Accessed 27 Sep. 2014].