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Cochlear Implants

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					Cochlear Implants

   Chris Darwin
                  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
Cochlear implant 2
Shannon
Implant
 Demo
                                                                        Cochlear-implant simulation



                                                                 Waveform of Original Sound                                                                            4                     Simulated w avef orm
                                                                                                                                                                x 10
                            8                                                                                                                              2

                            6                                                                                                                            1.5
                            4
                                                                                                                                                           1
                Amplitude




                                                                                                                                             Amplitude
                            2
                                                                                                                                                         0.5
                            0
                                      TextEnd                                                                                                              0           TextEnd
                            -2

                            -4                                                                                                                           -0.5

                            -6                                                                                                                             -1
                              0         0.5     1       1.5         2           2.5        3        3.5         4       4.5         5                        0             0.5   1   1.5        2           2.5       3     3.5   4   4.5
                                                                            Time (sec)                                                                                                              Time (sec)

                                                                Spectrogram of Original Sound                                                                                         Spectrogram of simulated w avef orm
                8000                                                                                                                                8000


                6000                                                                                                                                6000
    Frequency




                                                                                                                                        Frequency
                4000                                                                                                                                4000

                                    TextEnd                                                                                                                         TextEnd
                2000                                                                                                                                2000


                            0                                                                                                                              0
                                0        0.5        1     1.5           2            2.5        3         3.5       4         4.5                               0          0.5   1   1.5        2            2.5      3     3.5   4   4.5
                                                                              Time                                                                                                                    Time




From herrick_uedamodel/script_demo1:
best 6 of 16 channels, 250 Hz pulserate, 16 kHz sampling H/U filterbank
                Simultaneous sentences


 same Fo             difft Fo        difft Fo & VT



           Shannon 4-channel implant simulation


summer     ignore      difft Fo      difft Fo & VT
           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
              “Deaf is not a disability,
       it’s a culture and a community”.???
1. Should a congenitally-deaf child of deaf parents be given a
   cochlear implant?

2. 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???
               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).
                            Cochlear Implants (UK)                                                    Cochlear Implants (UK)
                                    Adults                                                                   Children
                     2600                                                                      2600

                     2400                                                                      2400

                     2200                                                                      2200

                     2000                                                                      2000




                                                                          Number of patients
Number of patients




                     1800                                                                      1800

                     1600                                                                      1600

                     1400                                                                      1400

                     1200                                                                      1200

                     1000                                                                      1000

                     800                                                                        800

                     600                                                                        600

                     400                                                                        400

                     200                                                                        200

                       0                                                                          0
                            '85 '87 '89 '91 '93 '95 '97 '99 '01 '03 '05                               '85 '87 '89 '91 '93 '95 '97 '99 '01 '03 '05

                                            Year                                                                      Year
                                    Cochlear Implants (UK)                                                            Cochlear Implants (UK)
                                            Adults                                                                           Children
                              300                                                                               300



                              250                                                                               250




                                                                                  Number of patients per year
Number of patients per year
  No. implanted per year




                              200                                                                               200



                              150                                                                               150



                              100                                                                               100



                               50                                                                                50



                                0                                                                                 0
                                    '85 '87 '89 '91 '93 '95 '97 '99 '01 '03 '05                                       '85 '87 '89 '91 '93 '95 '97 '99 '01 '03 '05

                                                    Year                                                                              Year
      Costs of hearing-aids and implants in the U.K.
      Total NHS audiology budget………………………approx. £60 million*

      Annual cost to NHS of hearing aids………………approx. £25 million*
      Annual cost to NHS of implants…………………...approx. £12 million**

      Average cost of supplying one hearing aid………approx. £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)
          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 (>75%) are able to use the telephone
for conversation.
      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?
                         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.
               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!
           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)
            Reading material

Cochlear Implants: fundamentals & applications
Graeme Clark
AIP Press. Springer 2003
In University Library

				
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