Cochlear Implant

Cochlear ImplantCochlear Implant

The Fundamental Concept of The Fundamental Concept of Cochlear ImplantCochlear Implant

To bypass the damaged hair cells.

HistoryHistory::

• Old generation: Sound awareness only

• New generation: Improved communication abilities (auditory cues with lip reading, open set speech)

• Since 1972 more than 16 different cochlear implants

• 1984 FDA approval for adults

• 1990 children approval

AnatomyAnatomyAnatomy

AnatomyAnatomyScala tympani

Scala vestibuli

Cochlear duct

Basilar membrane

Vestibular membrane

Tectorial membrane

Hair cells (outer/inner)

Cochlear nerve fibers

Physiology of Hearing

Anatomy-microAnatomy-micro

AnatomyAnatomy

Sensorineural Hearing LossSensorineural Hearing LossDeath of hair cells vs. ganglion cells

Otte, et al estimated we need 10,000 ganglion cells with 3,000 apically to have good speech discrimination

Apical ganglion cells tend to survive better

Pathologic AnatomyPathologic Anatomy

Structure of Cochlear ImplantStructure of Cochlear Implant

1. External components

2. Internal components

Components of Cochlear Implant

Anatomy of a Cochlear ImplantAnatomy of a Cochlear Implant

How does it work?

Neural Responses to SoundNeural Responses to Sound

1. Temporal coding: Provide information about timing cues (rhythm and intonation.

2. Place coding: Rely on the tonotopic organization of a neural fibers.

3. Provide information about quality (timber of a speech signal – sharp to dull)

Site of StimulationSite of Stimulation

1. Extracochlear

2. Intracochlear

3. Retrocochlear (lateral recess of the fourth ventricle over the cochlear nuclei.

Number of ChannelsNumber of Channels

1. Single channel – no place coding

2. Multi channel

Electrode DesignElectrode Design

1. Single electrode

2. Multielectrode

Indication for Cochlear ImplantIndication for Cochlear Implant

AdultsAdults 18 years old and older (no limitation by age)18 years old and older (no limitation by age) Bilateral severe-to-profound sensorineural Bilateral severe-to-profound sensorineural

hearing loss (70 dB hearing loss or greater hearing loss (70 dB hearing loss or greater with with littlelittle or no benefit from hearing aids for 6 or no benefit from hearing aids for 6 months)months)

Psychologically suitablePsychologically suitable No anatomic contraindicationsNo anatomic contraindications Medically not contraindicatedMedically not contraindicated

Indications for Cochlear Indications for Cochlear Implantation -- ChildrenImplantation -- Children

12 months or older12 months or older

Bilateral severe-to-profound sensorineural hearing loss Bilateral severe-to-profound sensorineural hearing loss with PTA of 90 dB or greater in better earwith PTA of 90 dB or greater in better ear

No appreciable benefit with hearing aids (parent survey No appreciable benefit with hearing aids (parent survey when <5 yo or 30% or less on sentence recognition when <5 yo or 30% or less on sentence recognition when >5 yo)when >5 yo)

Must be able to tolerate wearing hearing aids and show Must be able to tolerate wearing hearing aids and show some aided abilitysome aided ability

Enrolled in aural/oral education programEnrolled in aural/oral education program

No medical or anatomic contraindicationsNo medical or anatomic contraindications

Motivated parentsMotivated parents

Factors Affecting Patient Factors Affecting Patient SelectionSelection

a. Onset of deafness (congenital or adventitious)

b. Year of deafness

c. Length of sensory deprivation (i.e. no hearing aids)

d. Socioeconomic factors

e. Educational level

f. Individual ability to use minimal cues

g. General health

Factors Affecting Pt. (cont.)Factors Affecting Pt. (cont.)

h. Personality

i. Willingness to participate in rehabilitation program

j. Language skills

k. Appropriate expectations

l. Desire to communicate in a hearing society

m. Psychological stability

n. Cochlear patency

Audiologic EvaluationAudiologic Evaluation

1. Pure tone audiometry under headphones

2. Audiometry with a hearing aid in a monitored free field

3. Immittance testing

4. Speech recognition testing

5. OAE

Audiologic Evaluation (cont.)Audiologic Evaluation (cont.)

6. Environmental sounds (closed and open set)

7. Speech reading (lip reading) ability

8. Electrical response audiometry

9. Auditory discrimination

10.Transtympanic electrical stimulation (promontory or round window test)

Medical EvaluationMedical Evaluation

1. Clinical history and initial interview2. Preliminary examination3. Complete medical and neurologic examination4. Cochelar imaging using computed tomography

(CT or magnetic resonance imaging (MRI)5. Vestibular examination (electronystagmography)6. EKG7. Psychologic or psychiatric assessment or both8. Vision testing9. Assessment for anesthetic procedures

CT FindingsCT Findings

ContraindicationsContraindications

Incomplete hearing lossIncomplete hearing lossNeurofibromatosis II, mental retardation, psychosis, Neurofibromatosis II, mental retardation, psychosis, organic brain dysfunction, unrealistic expectationsorganic brain dysfunction, unrealistic expectationsActive middle ear diseaseActive middle ear diseaseCT findings of cochlear agenesis (Michel deformity) or CT findings of cochlear agenesis (Michel deformity) or narrow IAC (CN8 atresia)narrow IAC (CN8 atresia)Dysplasia not necessarily a contraindication, but Dysplasia not necessarily a contraindication, but informed consent is necessaryinformed consent is necessaryH/O CWD mastoidectomyH/O CWD mastoidectomyLabyrinthitis ossificans—follow scansLabyrinthitis ossificans—follow scansAdvanced otosclerosisAdvanced otosclerosis

RehabilitationRehabilitation

1-6-121-6-12 programprogram

Binaural Hearing AidBinaural Hearing Aid

Who’s eligibleWho’s eligible??

CurrentlyCurrently::Adults: severe to profound sensorineural hearing loss in both Adults: severe to profound sensorineural hearing loss in both

earsears Children (below age 2): a profound sensorineural hearing loss in Children (below age 2): a profound sensorineural hearing loss in

both earsboth ears Age 12 months or olderAge 12 months or older  

Receive little or no benefit from hearing aidsReceive little or no benefit from hearing aids  Adults: <50% open-set sentencesAdults: <50% open-set sentencesChildren: <30%Children: <30%

No medical contraindicationsNo medical contraindications    High motivation and appropriate expectationsHigh motivation and appropriate expectations  

* *Access to education and rehabilitation follow-upAccess to education and rehabilitation follow-up..

Surgical ProcedureSurgical Procedure

All electrode insertions are carried out through the facial recess approach. Various incision designs are used to allow wide exposure of the mastoid and squamous portions of the temporal bone. The temporalis muscle and periosteum are widely stripped to accommodate a “table” for the pedestal of the Ineraid device or the receiver-stimulator of the other devices. The mastoidectomy is not widely saucerized, but instead overhanging ledges are purposefully maintained. Care must be exercised so as not to damage the fibrous annulus during the facial recess approach..

Surgical TechniqueSurgical Technique

ComplicationsComplications::

A. Intraoperative

1. Intraoperative cannot be placed appropriately.

2. Insertion trauma 3. Gusher

Complications (cont.)Complications (cont.)::

B. Postoperative 1. Postauricular flap edema, necrosis or separation 2. Facial paralysis 3. Transient vertigo is more likely to occur on a totally nonfunctioning vestibular system. 4. Pain is usually associated with stimulation of Jacobson’s nerve, the tympanic branch of the glossopharyngeal nerve. 5. Facial nerve stimulation 6. Meningitis 7. Device extrusion

RehabilitationRehabilitation

Tuning or mapping of the external processor to meet individual auditory requirements after 3 - 4 weeks postop.

RehabilitationRehabilitation

RehabilitationRehabilitation

RehabilitationRehabilitation

RehabilitationRehabilitation

RehabilitationRehabilitation

RehabilitationRehabilitation

RehabilitationRehabilitation

Pediatric ImplantationPediatric Implantation

Five years after approval was given for adult implanta-tion by FDA, approval of cochlear implants for use in patients ages 2 to 17 years was granted. The major concerns regarding implantation in children included difficulty in evaluating the young child’s hearing impairment, assessing the performance and effect of implantation on the child’s development compared with traditional types of training, the risks of implantation (both intraoperative and long term), the effects of implantation on the auditory system, and the challenges of effectively programming such sophisticated devices in children.

New ConceptsNew Concepts

AgeAge

ABIABI

Binaural CIBinaural CI

Auditory Brain StemAuditory Brain Stem