continuing developments in cochlear implants · continuing developments in cochlear implants april...
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Continuing Developments in Cochlear Implants
April 2004
D Wagenfeld J Loock L Müller J Perold G Kerr I Kaltenbrünn
University Stellenbosch-Tygerberg HospitalCochlear Implant Unit
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How the Cochlear Implant System works
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Internal Components
Nucleus® 24 Contour Array held straight with stylet
Nucleus® 24 Contour Array in its natural shape
Nucleus 24 Contour (CI24R)
Receiver/stimulator and plate electrode
Ball electrode
Intra-cochlear electrode
Self curling tapered array - Close proximity to modiolus- Focused stimulation
22 half banded electrodes
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Electrode Options
o Nucleus 22 Series (1985 FDA release)
o Nucleus 24 (straight) (1997 FDA release)
o Nucleus 24 K (straight) (1999 FDA release)
o Nucleus 24 Contour (1999 FDA release)
o Nucleus 24 Contour Softip (2000)
o Nucleus 24 Double Array (1997)
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Nucleus 22 series
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Nucleus 24 Contour
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• Self-curling electrode array• 22 half-band electrodes• Adjacent to the inner wall of the cochlea• Cast pre-curved to regain pre-designed shape
& size
Nucleus 24 Contour
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Nucleus 24 Double Array
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Nucleus Hybrid CI
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Speech Processors
ESPrit 3G (Behind the Ear)
Small and LightweightDesign and Colours Full range of Speech Coding Strategies In-Built telecoil (T)Whisper SettingLong battery lifeIntegrated FM Technology
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Speech Processors
SPrint (Body worn)
Full range of Speech Coding Strategies, including ADRO
Four user selectable listening programs
Programmable volume and sensitivity controls
LCD panel to display control setting and system status
Warning alarms for low batteries (single and double)
Optional button lock
Full line of accessories
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Speech Coding Strategies
Speech Coding represents a set of ‘rules’ that define how the incoming acoustic speech signal will be analysed and coded by the speech processor
Types of Speech Coding Strategies:
– SPEAK (Spectral Peak Selection)– CIS (Continuous Interleaved Sampling)– ACE (Advanced Combination Encoders)
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Speech Coding Strategies (cont.)
Apical end processes low frequency information
Basal end processes high frequency informationNatural tonotopic
organisation of the cochlea
Spectral Information processed through 22 electrodes
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OUTCOME:Speech Processing Strategies
CID Sentence Scores for different Coding Strategies (N= 40 adults)
0
20
40
60
80
100
Sent
ence
Sco
re Pre Op6 Months12 Months24 Months
F0F1F2 MPEAK SPEAK SPEAK ACE22 22 22 24 24
1986 1989 1994 1997 2001
Coding strategies
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Advanced processing algorithms
• Effect of noise on speech perception• Directional microphone• Multi-microphone techniques
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Introduction of Cochlear Implants in South Africa
o 1986 US-Tygerberg Hospital
o 1991 Pretoria & Johannesburg o 2003 Bloemfontein
Multidisciplinary teams:ENT surgeons, audiologists, radiologists, pediatricians, speech therapists, educators, social workers, psychologists
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Number of implants per year 1986-2002US-TBH Cochlear Implant Unit
3 4 58
5 3 3 4 4 3 5 4 5
2
3
23
8 1411
1415
14
20
14 10
112 1
002
4
0
5
10
15
20
2519
86
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Years
Num
ber
ChildrenAdults
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Selection ConsiderationsPhilosophy: Ensure potential for significantbenefits from the device and the procedure
Specific considerations:• degree of hearing loss• age at onset of hearing loss• CTScan & MRI• medical• (re) habilitation support• informed consent
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Referral Criteria and Patient Selection
Previously restricted to patients over 2 years with profound HLExtended to severe HL, and children under 2 yearsAbnormal cochleas
Additional handicaps
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Selection Criteria for Cochlear Implants in Adults
Ages 18 years and overSevere to – profound sensorineural hearing loss in both earsPost-lingual onset of hearing lossReceive little or no useful benefit from hearing aidsScore of 50% or < on sentence recognition tests in the ear to be implanted and 60% or < in the non-implanted ear or bilaterally
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New candidacy guidelines: adults (cont.)
• Dowell, Hollow & Winton* (2003) Melbourne• Retrospective study post-operative speech
perception scores from 92 implantees• Statistical method developed • Outcomes: Adults with post-lingual hearing
loss & some useful pre-operative aided speech perception are now candidates if:- open-set sentences in quiet in best aidedcondition is < 70%
- open-set sentences in quiet in the implantear is < 40%
*Changing selection criteria for cochlear implants, the Melbourne experience.9th Symposium Cochlear Implant in Children, Washington DC, May 2003
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Selection Criteria for Children
Bilateral severe-to-profound sensorineural hearing lossNo useful benefit from HA:Birth – 2 years: restricted access to speech sounds with HA (aided thresholds outside speech spectrum at2000Hz and above) 2-5 years: lack of progress in development of
auditory skills (speech & language delay)> 5 years: <50% or less open-set sentence discrimination
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Selection Criteria for Children(cont.)
Realistic expectations of results
Family or caregiver is proactive and committed with re/habilitativeexercises
Has to be in an oral environment
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Selection Criteria (cont.)
Implantation of pre-lingually deafened adults and teenagersHave to be primarily oral communicators
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Selection Criteria: Disadvantaged Patients
ADULTS:- skill to enable re-entry to workforce- motivated to be gainfully employed- access to rehabilitation programCHILDREN:- adequate family support- parent/s be employed- accessible, appropriate educationaland audiological facilities
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Selection Criteria in Developing Countries
Lifetime commitment: maintenance ofdevice, sociological aspects andeducational placementLimited resources and allocation offundsEvery effort made to ensure optimal utilization of device, and avoid non-usage
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Outcomes
Majority are successful users
The cochlear implant gives access to all speech and environmental sounds
Sound-field thresholds 30dB average
Improved quality of speech production
Gives young children the potential todevelop spoken language
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dB H
eari
ng T
hres
hold
Lev
el
125 250 500 1000 2000 4000 8000
10 years old
20 years old
After Implantation
Frequency in hertz
0102030405060708090
100110120
MU O
EE
PSH
THSF
x x x x x
x
o
o o o o
o
x x x x x
x
o
o o o o
o
10 years old
Audiogram History
Just before Implantation
o
o
oo
o ox
x
xx
xx
oxox
Just before Implantation
o
o
oo
o ox
x
xx
xx
oo
o o
oo
xx
xx
xx
oo
o o
oo
xx
xx
xx
20 years old
CICI
CICI
CI
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Outcomes in adults
60% with current generation of cochlear implants achieve scores of 80-100% on open-set sentence recognition testsTelephone useImproved quality of life
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Improved employmentAdults with a CI are twice as likely to be in paid work,
compared to adults with severe hearing loss.
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Outcomes in Children
Spoken language acquisition andimproved speech intelligibility are theprimary benefits of CIBenefits for children in readingcomprehension and language knowledge may lead to mainstreameducation
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Age at implantation
Age at onset of hearing loss, communication mode, amount of residual hearing and duration of implant use are factors that influence performanceNeural plasticity and deprivation
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OUTCOME: Age at implantation in children
• Age at implantation is a prognostic variable for congenitally deaf children
• Biological bases
• Study:Compared progress in speech perception of a group of children implanted before 2 yrs (Group I) with a group implanted between2-3 yrs (Group II)
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Rate of Speech Perception Development
Figure 4. Speech Perception Categories after 12 months
0%
10%
20%
30%
40%
50%
60%
1 2 3 4 5 6 7Speech Perception Categories
Group 1Group 2
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Rate of Speech Perception Development
Figure 6. Speech Perception Categories after 24 months
0%
10%
20%
30%
40%
50%
60%
70%
1 2 3 4 5 6 7
Speech Perception Categories
Group 1Group 2
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• Children implanted before 2 years of age showed considerable progress in speech perception development that matched and even surpassed the progress of children implanted at later ages
• Earliest possible implantation would lead to the most normal development of hearing, speech and language
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Improved language developmentAfter cochlear implantation:Increased rate of language developmentthat exceeds that of non-implanted children
Rizer & Burkey 1999
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Consequences of un-managed hearing loss
Cost to society
Delayed and limited language development
Limited access to education
Underemployment/Unemployment
Difficulty participating in social activities
Negative impact on physical and mental health
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Funding in SABetween 1985 & 2003, 439 patients were referred to US-TBH CIU for CI evaluation46% adults, 56% children241 of 439 were NOT implantedMain reason: financial and socio-economic constraintsSA population: 43.1 millionHuge division in health market between public and private health sector
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New and future directions
Bilateral implantation
Hybrid electro-acoustic stimulation
Totally Implantable Cochlear Implant (TIKI)
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Bilateral ImplantationBilateral benefit is the ability to listen using
the ear with the better signal-to-noise-ratio
Sound localisation
Binaural advantage of using the signal from
both ears
Capturing the better ear
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Cochlear Implantationin a child with Schizencephaly
Schizencephaly: cortical malformation resulting from late neural migration and disruption of early cortical organization before 25th week of gestation
Cause: CMV during pregnancy
Multi-handicapped: quadriplegic cerebral palsy, profound hearing loss, global developmental disability
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Cochlear Implantationin a child with Schizencephaly
Criteria for selection: had to show intentional communicative behaviour
Implanted at age 2;11
Left ear (contra-lateral pathway)
Intra-operative stapedius reflex & NRT plus behavioural responses guided programming of electrodes.