Cochlear Implants

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Cochlear Implants

• Chris Darwin

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Cochlear Implant
1. Mic. 2.Lead 3. speech processor. 4 the
transmitting coil 5. Transmitting coil sends the
signals transdermally to the implanted
receiver/stimulator via an FM radio signal. 6.
The receiver stimulator 7. The electrodes along
the array stimulate the remaining auditory nerve
fibers in the cochlea. 8. auditory nerve
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Cochlear implant 2
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ShannonImplantDemo
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Cochlear-implant simulation
From herrick_uedamodel/script_demo1 best 6 of
16 channels, 250 Hz pulserate, 16 kHz sampling
H/U filterbank
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Simultaneous sentences
same Fo
difft Fo VT
difft Fo
Shannon 4-channel implant simulation
summer
ignore
difft Fo
difft Fo VT
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Suitability for implant
Over 2 years of age Profound hearing loss in
both ears Does not benefit from conventional
hearing aids Has strong desire to communicate

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Deaf is not a disability, its a culture and a
community.???

• Should a congenitally-deaf child of deaf parents
  be given a cochlear implant?
• Should a congenitally-deaf child of
  normal-hearing parents be given a cochlear
  implant? (95 of early-onset children are born to
  hearing families)
• If given an implant, the child will get the
  sensation of hearing and may learn language. But
  is the child then removed from the Deaf world in
  which he/she would otherwise grow-up in and
  contribute to?
• Should the wishes of the parents or of the Deaf
  community be paramount?
• Misinformation from both sides???

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Prevalence of hearing-loss in the U.K.
Hearing loss Prevalence
Number of people (approximate) 25 dB
or more (mild) 16
8 million 45 dB or more (moderate) 4
2 million 65 dB or more (severe)
1 500,000 90 dB or more
(profound) 0.3 150,000
From NICE report p 4/5 and National Study of
Hearing. My maths for the number of people
(50million or so).
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(No Transcript)
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No. implanted per year
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Costs of hearing-aids and implants in the U.K.
Total NHS audiology budgetapprox. 60
million Annual cost to NHS of hearing
aidsapprox. 25 million Annual cost to NHS
of implants...approx. 12
million Average cost of supplying one hearing
aidapprox. 90 (average cost of aid alone
40) Total costs of implant per child
patient...approx. 42 000 Total costs of
implant per adult patient...approx. 29
000 (includes fitting, rehabilitation and
maintenance for twelve years)
NICE report p.7 (1997 costs). Hearing aid
costs is for aids/batteries Summerfield and
Marshall (1995) Cochlear Implantation in the
UK 1990-1994 (in the Documents section of the
library Dept. Health 1995 Coc)
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Effectiveness of implants

• Cochlear implantees require continual follow
  up.
• Children, in particular, require a long period
  of rehabilitation
• to teach them to listen to the new sounds and
• to optimally tune the device.
• All children who receive cochlear implants can
  learn to hear everyday sounds.
• Most children are able
• to hear conversation without lip-reading and
• to use spoken language for everyday
  communication.
• Most implanted adults (gt75) are able to use
  the telephone for conversation.

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Arguments against implantation

• Destroys any residual hearing in the ear.
• Not a cure for deafness.
• Can children actually learn language from an
  implant?
• and some children gain no benefit from an
  implant.
• Surgical operation under general anaesthetic.
• Sign language is a proper language and is not
  English
• There are Deaf schools and (one) Deaf
  university.
• Is Deaf culture a minority culture? Do UN
  declarations on
• minorities apply?

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Arguments for implantation

• Implants do provide some hearing sensation.
• Complication rate from surgery is extremely
  low.
• Some congenitally-deaf children can carry on a
  conversation.
• Best current medicine can offer for
  profoundly-deaf children.
• Deaf education may not be as good as
  normal-hearing education.
• Deaf children are more vulnerable to
  mental-health problems.

P Hindley (2002), paper at BNPA conference.
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Progress

• Effective number of channels is increasing
• Music needs very good spectral resolution
• Possible to double effective number of channels
  by alternating them spatially between the ears.
• Experimental implants let the patient enjoy
  Beethoven again!

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WWW resources
here (outlining the background behind a new
American documentary on Deaf culture and
implants). here (position statement of the
National Association for the Deaf (USA) on
cochlear implants). here (Cochlear implant
information and resources squillions of links)
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Reading material
Cochlear Implants fundamentals
applications Graeme Clark AIP Press. Springer
2003 In University Library