Chapter 9: Cochlear Implants

Front 1

Review: Sensorineural HL

Back 1

Inner ear or deeper in brain
Typically permanent HL & problem is in cochlea

Front 2

Cochlea

Back 2

Not an organ we can remove from body- inside temporal bone
-NO such thing as cochlear transplant-a cochlear implant

Front 3

Organ of Corti

Back 3

Pressure variations within cochlear fluids causes basilar membrane (BM) to move.
BM movement contains information about the frequency of the acoustic signal.

*hair cells stimulated by fluid moving

Hair cells are attached to BM. If hair cells are damaged, sounds can’t be transmitted to the brain, thus causing sensorineural hearing loss.

Front 4

Now that we’ve concluded our brief review of auditory A&P... ask yourselves “Why cochlear implants?”

Back 4

First, remember how hearing aids work:
Hearing aids rely on ACOUSTIC
transmission of sound through the peripheral auditory system

Front 5

Healthy vs. absent auditory nerve fibers

*Auditory nerve fibers *Missing nerve fibers

Back 5

Degree of neural survival in implanted ear is single most significant physiological predictor of successful CI use.

Front 6

What is a cochlear implant?

Back 6

 A surgically implanted electronic device (in the cochlea) that can help provide sound to a person with severe-profound SNHL.
 It transforms acoustic sound energy into electrical energy that will initiate impulses in the auditory nerve.

Front 7

How is a Cochlear Implant Different From a Hearing Aid?

Back 7

Hearing Aids — rely on the responsiveness of healthy, inner ear hair cells. Type of transmission: acoustic.

Cochlear Implants — bypass the inner ear hair cells; stimulate auditory nerve (auditory neurons) directly. Type of transmission: electrical stimulation

Front 8

How a hearing aid works

Back 8

MIC
Acoustic to electric energy--->
AMP
Boosts signal------>
RCVR
Electric to acoustic energy---->
VIBRATE
Directly stimulate hair cells

Front 9

How a cochlear implant works

**Was on quiz

Back 9

MIC
Acoustic to electric energy--->
CODE
Speech processor encodes signal------->
SEND
From external to internal unit->
DECODE
Coded
signal passed to electrodes--->
STIM
Electrodes stimulate auditory nerve cells

Hint 9

1. External speech processor captures sound and converts it to digital signals
2. Processor sends digital signals to internal implant
3. Internal implant turns signal into electrical energy, sending it to an array inside the cochlea
4. Electrodes stimulate hearing nerve, bypassing damaged hair cells, and the brain perceives signals: you hear
sound

*Have to have a lof of HL to be a candidate

Front 10

A cochlear implant consists of 2 parts:

Back 10

Internal equipment
External equipment

*Look at picture know parts-had to label on quiz

Front 11

How does it work?

Back 11

 A small directional microphone located in the ear-level processor picks up sounds.
 The speech processor filters, analyzes, and digitizes the sound into coded signals
 Coded signals are transmitted to the headpiece.

Front 12

How does it work?

Back 12

 The transmitting coil sends coded signals as FM radio signals to the cochlear implant under the skin.
 The internal device delivers the appropriate electrical energy to an array of electrodes that has been inserted into the cochlea.

Front 13

How does it work?

Back 13

 The electrodes stimulate the remaining auditory nerve fibers in the cochlea.
 Once the auditory nerve fibers are stimulated, they send neural impulses to the brain, which are interpreted as sound.

-need functioning auditory nerve

Front 14

Pitch & loudness of sound depend on...

Back 14

Frequency (pitch)
 Different electrodes are stimulated depending on the frequency
of the stimulus.
• Electrodes placed near base are stimulated with high-freq signals
• Electrodes placed near apex are stimulated with low-freq signals
 Thus, pitch is related to place in cochlea being stimulated.

Intensity (loudness)
 Perceived loudness may depend on number of nerve fibers activated & rate of firing.
• Large number of fibers activated: perceived as loud
• Small number activated: perceived as soft

Front 15

What do speech & music sound like through a CI?

Back 15

 Multi-channel implants: electrode array stimulates different places in cochlea
• Processor breaks signal into different freq. channels
• Different manufacturers: different # of possible electrodes
(Nucleus=24, Combi=12 pairs, HiRes=16)
• Not all electrodes will be used

Multichannel simulation (1, 2, 4, 8, 16, 32 channels, then original)
Music simulation (4, 8, 16, 32 channels, then original)

Front 16

COCHLEAR IMPLANT PROCESS

Stages of CI Process (multi-disciplinary team)

Back 16

 Audiological evaluation to determine candidacy
 Medical evaluation- make sure the person is a candidate, medically able to handle surgery
 Preimplant counseling- what do we expect- what are your expectations
 Surgery
 Fitting/tune-up
 Follow-up
 Aural (re)habilitation

Front 17

Chronological Progression of Candidacy Approval

Back 17

1. 1985: CI developed for post-linguistically deafened adults
- only >90-100 dB HL PTA (originally)
2. NEXT: Peri- and pre-linguistically deafened adults
3. NEXT: Post-linguistically deafened children
4. 1990: Peri-linguistically deafened children (> 2
years)
5. Prelinguistically and congenitally deaf children are now included
•1998: 18 months approved
•2002: 12 months approved
•From 1990 – 2002, 8000 infants & children in US received CI

Special approval:
•As early as 6 months in U.S.
•As early as 4 months internationally

** look at notes page 6

Hint 17

Doing CI this early
PROS: access to auditory info

CONS:
-medical risk
-skull still growing
-Diagnosis might not be great at this age (not many pediatric audiologists)

Front 18

Current Candidacy Requirements (Adults)

Back 18

 At least 18 years old
 Moderate-profound SNHL in low freq; severe-
profound in high freq (>or=70dB HL bilaterally)
 < 50% open-set speech recognition with HAs in ear
to be implanted & < 60% in unimplanted ear
 3-6 month HA trial with limited benefit
 Medical contraindications ruled out by surgeon
 Speech & language eval if prelingually deafened

Front 19

Current Candidacy Requirements (Children)

Back 19

• Medical contraindications ruled out by surgeon
• Lack of benefit from HA
• 6 month HA trial with consistent bilateral HA use & must be receiving auditory training
• 3 month HA trial for meningitis

**look at slide on page 6

Front 20

Candidacy (review)

*was on quiz

Back 20

 Severe-profound SNHL
 Functioning auditory nerve
 Lack of benefit from HAs
 Plateau of auditory development in children
 Motivation & appropriate expectations

Front 21

Medical/Surgical Evaluation

Back 21

 Note potential complicating factors:
• Previously created surgical defects
• Congenital anomalies-some people have no cochlea
• General exam to make sure patient is healthy enough
for surgery
 Radiologic assessment of cochleae
• CT scans to study basal turn of cochlea
• Malformations or disease processes (otosclerosis or
meningitis) too much bony growth to get electrode in

**Wipes out structures in cochlea when putting electrode array in cochlea
-destroys internal structures of cochlea

Front 22

Risks/Considerations

Back 22

 Head growth
• At birth, cochlea is adult size but temporal bone, which houses
CI components, continues to grow until age 2
 Device malfunction-rare but can happen
• Reimplantation is necessary  Meningitis – 52 cases of postimplant meningitis have
been reported in US (out of 67,000+)
• FDA recommends following for prevention (FDA, 2003)
• Diagnose & treat otitis media promptly
• Pneumococcal vaccinations (Streptococcus pneumoniae)
• Hib vaccination (Haemophilus influenzae-type B)

Front 23

Preimplant Counseling Topics

Back 23

 Cochlear implant hardware-metal so no MRIs/problems with airport security etc.
 Costs
• $60,000 - $80,000
• Include evaluations, hospitalization, surgery, device,
fitting, follow-up visits, aural rehab
-usually insurance covers, but not always
 Realistic expectations
• Does not cure deafness!
• Talk with other CI users
• Speech/language development in children

Front 24

Preimplant Counseling Topics

Back 24

 Commitments for intensive therapy & regular usage -takes a lot of work/appointments follow up visits
 Social considerations
• Be aware of controversy surrounding
implantation in children by Deaf community
 Communication mode
• Aural/oral, total, ASL

Front 25

Outpatient Surgery

Back 25

 Incision made in mastoid bone for placement of receiver stimulator
 Electrode array inserted into scala tympani of cochlea through the round window
 Insertion depth: up to 31 mm depending on implant system
-how far goes in cochlea=the frequency you can get. Can't get much further then that
 3-6 week waiting period for incision area to heal

Front 26

CI Fitting (Hook-up)

when it gets turned on

Back 26

 May take 11⁄2 - 2 hrs
 Program speech processor by computer
 Telemetry: examine integrity of internal components (check electrode voltages)
 Determine electrical dynamic range:
• electrical threshold (C-level)
• maximal level of current that is comfortable (M-level)
-how much sound they can handle-softest sound perceived & loudest-threshold
-how much signal do you have to send before they can precieve
 Create MAPs based on dynamic range

Front 27

Follow-Up Visits

Back 27

 1st follow-up approx. 1 wk after hook-up
 Discuss patient’s experiences
 Re-evaluate dynamic range settings & program new MAPs
 Decreased performance is cause for concern (no longer responds to sound, voice quality change)

Front 28

Aural (re)habilitation

Back 28

 Listening and speech skills do not occur automatically...a concerted effort is required
 Aural rehab plan in children must include:
• Parents – games/activities at home that provide listening
practice
• Speech/hearing professionals – develop auditory training
program
• Educators – become familiar with device & troubleshooting

Front 29

VARIABLES THAT AFFECT PERFORAMANCE

Factors that Influence Performance

Back 29

 Individual characteristics
•Age at implantation
•Previous auditory experience
•Presence of other learning handicaps
•Personal attributes
•Strong family support
 Communication mode

Front 30

Age at implantation

Back 30

 Younger = better
 Kids implanted < 2 years develop better speech perception and speech production skills than later-implanted children.
 Highly ‘plastic’ brains

Front 31

There is a sensitive period of 3.5 years during which implantation occurs into a highly plastic central auditory system.

0-3=critical period for language development

Back 31

Implantation after 7 years occurs into a relatively degenerate central auditory system which shows reduced plasticity.

Front 32

Age at implantation

Back 32

 Older children who have used hearing aids consistently and communicate orally perform better than older children using a more manual approach.

Front 33

Previous auditory experience

Back 33

 Onset of deafness
• Residual hearing provides a
“bank” of auditory experiences from which a child can pull to understand sound input from a CI
• A child born with profound deafness must start from scratch with a CI

Front 34

Duration of deafness

Back 34

 Adults with prelingual, long-term deafness who receive CI typically do not develop open-set word recognition abilities.

 WHY? Brain “hearing” areas are allocated for other functions. The brain is no longer as ‘plastic’ as in childhood.

Front 35

Presence of other handicaps

Back 35

 Children who have other handicapping conditions in addition to deafness may make slower progress.

 Is the child able to make use of intact sensory modalities?
• A child in tune with his environment (vision, taction) will be able to make use of auditory input better than a child who ignores visual cues or is tactiley defensive.

Front 36

Personal attributes

Back 36

Cognitive abilities
Behavioral temperament Overall health

Front 37

Additional factors to consider

Back 37

 Bilateral hearing
• HA in one ear, CI in other
• CIs in both ears
-arguments for which is better
 Strong family support for developing auditory behavior
 Finances
 Time/availability and distance from the treatment program

Front 38

Communication Mode

Back 38

 Comm. mode is more important to auditory & spoken language development than any other rehab factor
• More than classroom placement, amount of therapy, experience of therapist, parental participation (Roeser & Bauer, 2004)
-best predictor for success

 Children with a cochlear implant benefit most from methods strongly encouraging development of listening & speaking skills & integrating these skills into everyday life.
• Oral-aural communication

Front 39

Communication Mode: Goals

Back 39

 Getting language to the child.
-getting language up to brain
 Helping the child understand what he hears.
 Helping the child develop spoken language
skills.
 Helping the child gain independence &
self-confidence.

Front 40

Teaching Auditory Integration

Back 40

Even though the cochlear implant makes sound signals available to a child’s auditory system, the child must be taught to make meaningful use of this auditory information

Front 41

Teaching Auditory Integration


Characteristics of school programs that teach Meaningful Auditory Integration

Back 41

 Consistently communicate that sound has meaning...there is a reason to listen! ***
 Maintain strong expectations for listening.  Reduce predictability.

Front 42

Teaching Auditory Integration

Characteristics of school programs that teach Meaningful Auditory Integration

Back 42

 Participate with student’s therapists and parents to bridge activities into the child’s real life.
 Integrate language goals into auditory classroom activities.
 Integrate the process of listening, speaking, and thinking.

Front 43

Monitoring progress

Back 43

 Children receiving cochlear implants, on average, make one year of language growth in one year’s time.
 Research supports this language growth over 2-4 yrs post implantation

Front 44

Monitoring progress

Back 44

MAIS (Meaningful Auditory Integration Scale)
• Parent report scale (10 probing questions) to evaluate child’s skills in
real-world situations
• Scored based on parent report & clinician observation

IT-MAIS (Infant-Toddler MAIS)  An adaptation of the MAIS, with items modified so as to be appropriate for
very young children. Areas assessed include:
• Vocalization behavior
• Alerting to sounds • Deriving meaning from sound
*Use interview format to avoid “leading” parents into telling clinicians what they want to hear

Front 45

Example: MAIS question #3

Back 45

Does the child spontaneously respond to his name in quiet when called auditorially-only with no visual cues?

Clinician asks, "If you called ______'s name from behind his back in a quiet room with no visual cues, what percentage of the time would he respond the first time you called?"
_____0=Never: If the child never does.
_____1=Rarely: If he has done it only once or twice or only with multiple repetitions. _____2=Occasionally: If he does it about 50% of the time on the first trial or does it consistently but only when parent repeats his name more than once.
_____3=Frequently: If he does it at least 75% of the time on the first try.
_____4=Always: If he does this reliably and consistently, responding every time just as a hearing child would. Ask for examples.

**look at graphs on p. 12

Front 46

The Deaf Culture’s perspective about cochlear implants...

National Association of the Deaf (NAD) Position on Cochlear Implants

Back 46

 In 1990s, NAD was strongly opposed to implantation in children

 The NAD played a big role in quieting the controversy in 2000-2001 when it boldly took a balanced position on cochlear implants

Front 47

NAD’s Current CI Position

Back 47

What are the deaf community's
concerns today?

Front 48

Review

Back 48

 Cochlear implant components
 How does it work?
 Cochlear implant process
 Variables that affect performance