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Cochlear ImplantsJohn S. Oghalai, MD

Division of Otology, Neurotology, and Skull Base SurgeryDept. of Otorhinolaryngology & Communicative Sciences

• Hearing allows us to be conscious of what goes on around us

• Always “working” to warn us of danger• Hearing allows communication• Hearing loss affects 28 million Americans

(1/10)• Isolation from society

Background

Frequency GradientHigh Low

Sound Propagation in theInner Ear

2

All Hair Cells Have Two FunctionsMechano-Electrical Transduction

Neurotransmission

Outer Hair Cells Carry OutElectro-Mechanical Transduction Passive Cochlear Model

• Mass• Stiffness• Damping

Mechanical models

Filtering

Passive

Frequency

Active Sensorineural Hearing Loss

• Mechanisms of sensorineural hearing loss– Congenital malformations (otic capsule

may or may not be involved)– Stria vascularis– Spiral ganglion cells– Organ of Corti / hair cells

• Presbyacusis (age- related hearing loss)• Noise- induced hearing loss

Loss of OHCs(12,000 max)

3

Normal Cochlea

AuditoryNerve

HairCells

Hearing-Impaired Apex

Scala Vestibuli

Spiral Ganglion

Organ ofCorti

(Hair Cells)

Bipolar Contacts

Auditory Nerve

Oval Window

Round Window

Electrode

Central Rib

BaseCochleostomy(scala tympani)

ClarionTM

Cochlear Implant

Common Components of all Cochlear Implant Systems

Microphone & Cable

Speech Processor

Antenna/Transmitter

Receiver/Stimulator

Electrode Array

Nucleus 3 system

1

Sound enters microphone on headpiece

2

Sound travels down cable to processor

4

3

Processed sound travels back up cable to headpiece

4

Processed sound is transmitted to implant through skin

5

Implant sends sound to cochlea through electrode

6

Electrode in cochlea stimulates auditory nerve

Advances in Implant Technology

• Technological advances have resulted in improvements in patient performance

• In turn, improvements in patient performance have resulted in expanded audiological criteria!

Optimal Electrode Placementat Medial Wall

LATERAL MEDIAL

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Advances in Electrode Design

Spiral Electrode(1990)

Spiral Electrode with Positioning System (EPS)

(1998)

HiFocus Electrode with Positioning System (EPS)

(1999)

CLARION & POSITIONER17 mm insertion 630º

CLARION ELECTRODE 24 mm insertion 500º

Design changes implemented so that the electrode closely hug the modiolus

Positioner

Mean Most Comfortable LevelsThree Electrode ConfigurationsMonopolar Pulsatile Stimulation

100

150

200

250

300

350

400

1 2 3 4 5 6 7 8Channel Number

Clin

ical

Uni

ts

Spiral alone at3 months(n=51)

Spiral + EPS at1 month (n=20)

HiFocus+EPSat 1 month(n=34)

Nucleus Contour ElectrodeStylet in place

Stylet removed

K117L, 12.5 mm el. #1

Insertion trauma: K117L, 11.5 mm el. #2Insertion trauma: K117L, 11.5 mm el. #2

SGSG

SGSGOSLOSL

Slide from Pat Leake, UCSF

SpLSpL

RMRM

ContourContourTM

ElectrodeElectrodeSpGSpG

OSLOSL

OticOticcapsulecapsule

Slide from Pat Leake, UCSF

SpGSpG

OSLOSL

ElectrodeElectrode

Sc Sc TymTym

Sc VestSc Vest

Slide from Pat Leake, UCSF

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SpLSpLRMRM

ElectrodeElectrode

PositionerPositioner

OSLOSL

SpGSpGHiFocusHiFocus

OticOticCapsuleCapsule

Slide from Pat Leake, UCSF

External Equipment

Speech Processors• Automatic, Continuous

Functionality Check of All External and Internal Components

• Multiple Indicator Lights

• Programmable Acoustic Alarm

• ESD Resistant• Easy to Adjust Controls

> Built-in microphone tester

> Multiple Signal-to-Noise ratio options for FM/Accessories

“mini-computer”

BTE Sound Processor

8 Runs all processing strategies plus new ones under development

8 Rechargeable batteries for low operating cost

8 Compatible with all CLARION internal implants

8 Same functionality as Body worn PSP, except no warning lights/alarms

8 Check functionality with Sensor

Clarion

Nucleus

CLARION Sound Processor Development

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100

S-Series Platinum Series & BTE

Million Instructions Per Second (MIPS)

Continuous Two-Way Telemetry

• Ongoing monitoring achieved with two distinct carrier frequencies

• Normal concurrent signal operation

• Benefit for children who are unable to communicate

Power & Data

BackTelemetry

Headpiece ICS

SP Status Indicator

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Input Dynamic Range (IDR)

•The normal ear captures widely fluctuating speech intensities ranging over 50 dB as well as speech from talkers when they are far away or speaking softly•CLARION captures the widest range of incoming sounds through its electronics and software

CLARION60 dB IDR

Industry norm

30 dB IDRNormal

Hearing120 dB

50 dBPeaks

& Valleysof Speech

30

90

70

50

““Narrowed” IDR (30 dB)Narrowed” IDR (30 dB)Perceptual D

R (Perceptual D

R ( uAuA))

Soun

d Pr

essu

re L

evel (dB

SPL

)So

und

Pres

sure

Lev

el (dB

SPL

)

IDR T

M

AGCAGC

Speech ProcessorSpeech Processor ElectrodeElectrode

30

90

70

50

““Widened” IDR (60 dB)Widened” IDR (60 dB)

Perceptual DR (

Perceptual DR ( uAuA

))

Soun

d Pr

essu

re L

evel (dB

SPL

)So

und

Pres

sure

Lev

el (dB

SPL

)

IDR

T

M

AGCAGC

Speech ProcessorSpeech Processor ElectrodeElectrode

Acoustic Signal

Pass band 1 Envelope Compression Ch 1

Pulse Train Carrier

Pass band 2 Envelope Compression Ch 2

Pass band N Envelope Compression Ch N

AGC & Low Pass

high

low

mid

BTE Decals

Six inter-changeable color headpiece caps

Nucleus

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Speech Processing

Speech Spectrum

S e n t e n ce

Spectral Resolution (Number of Channels)

• Most important factor is the number of spectral channels of information– number of distinct pitch channels

• Number of effective channels is not the same as the number of electrodes

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Spectral Cues in Music

• While spectral and temporal fine structure are not necessary for speech recognition they constitute the very heart of music, illustrating the different demands of speech and music on peripheral sensory processing

• Melody recognition requires many more spectral channels than speech

• “The cochlea isn’t designed for speech… the cochlea is designed for music” (Ed Burns)

4 8 16 32 Original

Popular Music with male vocal

Processing Strategy and Stimulation Mode

CISMonopolar

SASEnhanced Bipolar

Ch. 1

Ch. 2

Ch. 3

Ch. 4

Ch. 5

Ch. 7

Ch. 8

Ch. 6

MPSMPSBipolar or MonopolarBipolar or Monopolar

Who is a CI Candidate?

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Who Should Get a Cochlear Implant? Children

• Children aged 12 mos-17 years

• Profound sensorineural hearing loss of 90 dB or greater in both ears (No Response ABR)

• Lack of benefit from high powered hearing aids – 3-6 month Required Hearing Aid Trial– < 2 on Questions 3, 5, & 6 on the IT-MAIS

Questionnaire• Older child (>6yrs): Some auditory skills

• 0-20% on tests of open-set word recognition (PB-K or MLNT)

Don’t Wait! The Younger the Better!

Who Should Get a Cochlear Implant? Children

• Rehabilitative or educational setting where development of listening and speaking skills are emphasized

• Positive family environment where device use through listening and speaking is encouraged

Adults Who Should Get a Cochlear Implant?

• Healthy adult over 18 years of age, no upper age limit

• Severe-Profound sensorineural hearing loss of 70 dB or greater in both ears

• Postlingual onset of deafness (after age 6 yrs)• Prelingual adults that are members of the hearing

community (lip readers, verbal intent)• Lack of benefit from hearing aids

– HINT Sentence score < 50%

Adult Referral Criteria

• PTA of >70dB in Both Ears

• Monosyllabic Word score of < 30% in Both Ears

Audiological Measurement:CI Candidate?

250 500 1000750 1500 2000 4000 6000 8000-10

01020304050

Hz

60708090

100110120

dB

X XX

XXX

86 Yr. Old AdultPTA=103dB ASPTA=105dB ADCNC Words:=0% AS =0% AD

O

OO

OO

O

X

CI CI CI CI CI

YESAudiological Measurement:

CI Candidate?

250 500 1000750 1500 2000 4000 6000 8000-10

01020304050

Hz

60708090

100110120

dB

X

X

XX

X

X

56 Yr. Old AdultPTA=83dB AS

PTA=75dB ADCNC Words

=12% AS =16% AD

O

OOO

O

O

X

XO

YES

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Evaluation &

Expectations

Adult Evaluation: Pre-Operative

• Thorough Audiological assessment to determine degree and type of hearing loss and amount of benefit from acoustic amplification

• Include OAEs &/or Acoustic Reflex Testing

• Medical work up, including CT scan or MRI

• Counseling for realistic expectations

Cochlear Implant Surgery

• About 2.5 hours• General anesthesia, Outpatient• Procedure

– Incision– Drill facial recess– Trough for electrode lead– Bony bed for receiver/stimulator– Secure receiver/stimulator with sutures– Cochleostomy for electrode insertion– Pack with fascia and close incision

Covered by InsuranceDon’t take “NO” for an answer

Cochlear Implant Surgery72 year old male with progressive sensorineural hearing loss

A Post-Auricular Incision

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Exposure of the Mastoid Cortex Drilling the Mastoid and Countersinking the Implant

Securing the Implant The Facial Recess

Stapes

Round Window

Facial Nerve

LateralSCC

Incus

Placement of the Electrode Complications

• Hearing loss - in everyone– New techniques to reduce HL

• Variable outcomes • Chorda tympani nerve injury

COMMON

•Infections - uncommon•Flap necrosis - uncommon•Tinnitus & Imbalance - usually self limited •Facial nerve injury - congenital abnormality•MENINGITIS - a problem of mythic

proportions

UNCOMMON

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Risk factors for meningitis

Inner Ear MalformationsPrior history of meningitisYoung children (esp.< 5 yrs).Otitis mediaImmune dysfunctionPrior ear surgery

Meningitis in Cochlear Implantation

• 91 people worldwide (N=60,000)• 17 deaths• 53 US cases (N= 25,000)

– Ages 18 mos to 84 yrs; Most under 7 years of age (n=33)

– Signs and Sx <24hrs to >6 yrs– 50% developed meningitis < 1 year postop

(N=32)– 29 Advanced Bionics CLARION (1996;N=7500) – 22 Cochlear Nucleus (1985; N=16,500)– 2 MED-EL (2001; N=770)

Design Flaws?

• Higher incidence with Clarion positioner

• Removed from the market

• HF1 electrode now available without the positioner

Positioner

Post-Operative Evaluations:Device Fitting and Follow-up

• Initial stimulation: 3-6 weeks post surgery

• Adjustments made regularly based on feedback from patients, parents, therapists and educators

• Speech perception evaluations semi-annually to annually

Evolution of Implant Outcomes

• Single-channel implants• Sound detection, perception of speech

rhythm, lipreading enhancement

• First generation multichannel implants• Closed-set word identification, some

open-set sentence recognition; poor open-set word recognition

Current Expectations

• Sound Field thresholds 20-45dB @ 250-6K Hz

• Cannot return to Hearing Aid in implanted ear

• >80% Postlingual Adults use the telephone

• >50% of Postlingual Adults enjoy music

• Near peak performance by 3 months!

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Open-Set Speech RecognitionN=56 Postlinguistic Patients

Six-Month Scores

* Note: Only patients who score > 20% on HINT Sentences in quiet are administeredHINT Sentences in noise.

3%13%11%

20%

44%

57%

71%

35%

79%

40%51%

67%

47%

73%

52%

81%

0%

20%

40%

60%

80%

100%

CNC Words CID Sentences HINT in Quiet HINT +10 S/N*

Perc

ent C

orre

ct

Pre1Month3Month6Month

Individual CNC Word Scores at 3 Monthsand Duration of Deafness (n= 67)

High levels of CNC word recognition were achieved by patients with long as well as short duration of deafness.

0%10%20%30%40%50%60%70%80%90%

100%

0 0 1 1 1 1 2 2 2 2 2 3 3 3 6 6 7 7 8 10 12 12 15 17 20 20 21 26 26 28 30 38 43 58

Years of Deafness - Implanted Ear

Perc

ent C

orre

ct

0 00

Mean = 40% Median = 42%

Individual CNC Word Scores at 3 Monthsand Age at Implant (n=67)

31% of the sample was implanted at > 70 years of age. Some of these older patients show high levels of word recognition at three months. Others may require more implant experience before they demonstrate open-set word recognition abilities.

0%10%20%30%40%50%60%70%80%90%

100%

22 26 28 33 39 40 43 45 46 49 50 52 53 55 56 59 60 61 62 63 65 68 69 71 73 73 75 75 76 78 80 82 84 88

Age at Implant (Years)

Perc

ent C

orre

ct

00 0

Mean = 40% Median = 42%

SPIRAL GANGLION CELL DEGENERATIONFOLLOWING NEONATAL DEAFNESS

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10 11 12

Duration of Deafness (months or years)

< 1 year n = 56

r2 = 0.83 p<0.001

61 2 3 4 5 7

> 2 years n = 11 (6 cats)

Gan

glio

n C

ell D

ensi

ty (

% n

orm

al)

Slide from Pat Leake, UCSF

K117 L, GM1 Stimulated: K117 L, GM1 Stimulated: 5 mm, SG = 80% of normal5 mm, SG = 80% of normal

K117R, GM1 Deafened Control:K117R, GM1 Deafened Control:5 mm, SG = 40% of normal5 mm, SG = 40% of normal

Slide from Pat Leake, UCSF

Why Research Cochlear Implant Alternatives?

• Outcomes with a cochlear implant are good… but not as good as normal hearing

• Cochlear implants can not be used for mild or moderate levels of hearing loss

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-10

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10

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30

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80

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125 250 500 1000 2000 4000 8000

FREQUENCY IN HERTZ

HEA

RIN

G L

EVEL

IN d

B(A

NSI

- 19

96)

750 1500 3000 6000

-10

0

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30

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FREQUENCY IN HERTZ

HEA

RIN

G L

EVEL

IN d

B(A

NSI

- 19

96)

750 1500 3000 6000

Pie in the Sky? Modulation of Cochlear Mechanics• Drug therapy• Gene therapy• Physical

manipulations

1) Measure hearing with various cochlear potentials (CAP, DPOAES, CM, & EP)

2) Measure basilar membrane motion using laser doppler vibrometer (2 picometersensitivity)

Ventral Exposure of the Guinea Pig Cochlea Perfusion Technique

CanaliculaePerforantes

Research Implications:Developing a Treatment for Cochlear Hearing Loss

• Techniques for performing surgery of the inner ear• Potential surgical objectives:

– Change mass, stiffness, or damping of organ of Corti• Laser• Physical manipulations

– Drug therapy • Modulate outer hair cell electromotility• Modulate stereociliary transduction

– Genetic manipulations:• Insert exogenous motor proteins (prestin)• Modulate tectorial membrane passive mechanics

– Electronic device implantation (bionic OHC’s)

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Baylor College of MedicineChul-Hee Choi, Ph.D.Gentiana Wenzel, M.D.Anping Xia, M.D., Ph.D.Nicola Schug, M.S.

William E. Brownell, Ph.D.Ruth Anne Eatock, Ph.D.Fred Pereira, Ph.D.Peter Saggau, Ph.D.

University of California – San FranciscoPat A. Leake, Ph.D.Russell Snyder, Ph.D.

New York UniversityAnil K. Lalwani, M.D.

Stanford UniversityRobert K. Jackler, M.D.

Rice UniversityBahman Anvari, Ph.D.Robert Raphael, Ph.D.

Johns Hopkins UniversityAlex Spector, Ph.D

University of Tuebingen, GermanyMarkus Pfister, M.D., Ph.D.Nicola Schug, M.S.

National Institutes of HealthNational Organization for Hearing Research

Acknowledgments