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Cochlear ImplantationDr. Utkal Mishra2nd Yr. PG (ENT)

INTRODUCTIONCochlear implants are the 1st true bionic sense organs. It is surgically implanted in the inner ear and activated by a device worn behind the ear.Cochlear Implants are not hearing aids. The Fundamental Concept of Cochlear Implant is to bypass the damaged hair cells.The device bypasses damaged parts of the auditory system and directly stimulates the nerve of hearing, allowing individuals who are profoundly deaf to receive sound.

HISTORY1800 Alexandro Volta - electrical stimulation to metal rods inserted in his ear canal created an auditory sensation .1957 Djourno & Eyeries stimulated auditory nerve directly with current & the patient reported a clear auditory percept.1961 House & Doyle put electrodes in scala tympani of 2 profoundly deaf adults & get a clear auditory response1972 First single channel cochlear implant developed.1984 Cochlear Corporation introduced the first ever Multichannel Cochlear Implant System called NUCLEUS 22 1976 Wednesday 22 September - The first cochlear implant took place at Saint-Antoine hospital, Paris. It was performed by CH Chouard & assisted by Bernard Meyer.

PARTS OF COCHLEAR IMPLANTEXTERNAL PART 1. Microphone2. Speech processor3. Transmitter

INTERNAL PART 1. Receiver Stimulator2. Electrode Array

EXTERNAL PART

MICROPHONESPEECH PROCESSORTRANSMITTER

INTERNAL PART

MAGNETANTENNASTIMULATORELECTRODE

TYPES OF COCHLEAR IMPLANT3 Types :-1. NUCLEUS 24 FREEDOM by Cochlear Corporation2. HI RES 90K by Advanced Bionics3. PULSAR by Med El

NUCLEUS 24 FREEDOM

HI RES 90K

MED EL PULSAR

COCHLEAR IMPLANT CANDIDATES

Each cochlear implant system is shipped with a Physician's Package Insert which specifies the FDA labeled indications for implantation. Since the three cochlear implant manufacturers generally work independently, the labeled indications for cochlear implant criteria vary across the companies.

ADULTAge More than 18 yrsBilateral severe to profound Sensorineural hearing loss.Both Advanced Bionics and Med El - severe-to-profound Cochlear Corporation - moderate-to-profoundMust be Postlingual DeafLittle or no benefit from hearing aids.Inner ears must be surgically able to accept the deviceMust not have any chronic illnessA deaf adult who never learned to speak does not benefit from a cochlear implant.

AUDIOMETRIC CRITERIAGone are the days when cochlear implantation is done only in hearing loss above 90 dB

SPEECH RECOGNITIONSentence recognition testing is done in best aided condition at 60 dB SPLFDA approved sentence lists used are BKB SIN sentences in Noise & QuietAz -Bio sentencesCNC monosyllabic wordsMaximum score for cochlear implant candidacy variesAdvanced Bionics 50 %Cochlear Corporation 60 %Med El 40 %

PEDIATRICAge More than 12 monthsBilateral profound sensorineural hearing loss > 90 dBNo benefit at all with the most optimized hearing aid.Inner Ear surgically accesible in CT scanAuditory nerve present in MRIPost lingual profound deafness caused by meningitis is not a good candidate for cochlear implant. neoosteogenesis causing cochlear duct obliteration.

AGE 12 24 monthsBilateral profound sensorineural hearing lossTrial of hearing aids for 3 months - should make at least 3 months of progress in auditory skills and speech/language development. The evaluation of auditory skills and progress for children aged birth to 2 years is not achieved by simply looking at the audiogram. Auditory skills are generally assessed via parental history and administration of validated questionnaires designed to gauge auditory-based responsiveness to speech and sounds in a child's environment.

QUESTIONNAIREIT-MAIS Infant Toddler version of meaningful Auditory Integration Scale (Commonest) FAPCI - 23-item Functioning after Pediatric Cochlear Implantation35-item Little Ears auditory questionnairePEACH - Parents' Evaluation of Aural/Oral Performance in Children

OLDER CHILDRENThe determination of cochlear implant candidacy for older children is generally based upon either mono- or multi-syllabic word recognition byEarly Speech Perception TestMultisyllabic Lexical Neighbourhood testHINT Sentences for children < 30 %

WHICH EAR TO IMPLANTBetter hearing earMost recently deaf earLeast obstructed labyrinthIn traumatic hearing loss the ear with reduced labyrinth function chosen

Electroacoustic / Hybrid ImplantCombine a cochlear implant with hearing aid.Indication Individuals with profound high frequency loss with retained low frequency hearingCI Stimulates basal turn >> High FrequencyHearing aid amplifies low frequency

DEVICE SELECTIONAesthetic looksCoding StrategyElectrode arrays 1. Compressed array2. Double array

CODING STRATEGYA speech coding strategy defines the method by which pitch, loudness & timing of sound is translated into series of impulses.2 types 1. Simultaneous (Only AB)2. Non simultaneous

SIMULTANEOUS STRATEGYActivation of more than one electrode at same time.Provide a more natural quality of soundOnly Advanced Bionics is capable of SS.Disadvantage- When 2 electrodes are activated simultaneously there is chance of signal interference.So Modiolus Hugging Electrodes are developed lies close to spiral ganglion so less intensity sound is required for activation hence less interference.

MODIOLUS HUGGING ELECTRODESelf coiling electrode array with memory.Comes with a stylete which keeps the electrode straight during insertionAs it uses low intensity signals Extended Battery Life

Electrode 1Electrode 2

Channel interactionIncreased Distance

Spiral Ganglion cells

Electrode 1Electrode 2

Activated Cells

Activated Cells

PRE-OP EVALUATION1. AUDIOLOGICAL PTASpeech audiometryAided audiometryBERAPromontory Stimulation TestOAE2. RADIOLOGICAL HRCT Cochlear HypoplasiaIACMRI Early Labyrinthitis OssificansPostmeningitic Endocochlear ObstructionAbsent Cochlear Nerve

SURGICAL PROCEDURE

CONSIDERATIONSCan be done as outpatient or inpatient.Can be done under GA or LA.IV antibiotics should be given at least 20 minutes before skin incision.Surgery duration 3 -5 hrsDuration of stay in Hospital 2 days3 to 4 weeks later Programming of device

INCISION & SKIN FLAPInverted J shaped incision.Incision should not cross the edges of deviceFlap elevated in 2 layersPeriosteum of mastoid is elevated as an anteriorly based Palva flap.Skin thickness over implanted stimulator should be less than 6.0 mm

THE WELLA portion of skull as flat as possible selected for the placement of stimulator minm. 15mm postr. to EAC.Surgical drill used to create a defect in the skull contoured exactly to fit the stimulatorA channel is also formed for the passage of electrodes to mastoid cavity.Tie down holes are drilled around the well. Dangerous !!!Device is fixed with sutures in the well.

MASTOIDECTOMYThe cavity should not be saucerized.Edges should be left as acute as possible to retain the electrodes within its confine.Facial recess identified & posterior tympanotomy done.If facial recess seems unusually large Facial N. anomaly suspected Be ready for a cochlear anomaly also !!!

COCHLEOSTOMYRemove the anterior lip of round window niche.Apply Lubricant Healon or ProviscThe electrode array is inserted as atraumatically as possible with its tip directed inferiorly.Cochleostomy sealed with a small piece of soft tissue.

CLOSUREThree layered wound closure done Palva flap closed tightly with interrupted absorbable suturesSuperficial flap closed with burying interrupted suturesSkin closed with Subcuticular sutures.

POST OP COMPLICATIONS

EARLYFacial N. InjuryAlteration of TasteInfectionWound dehiscnce / Flap NecrosisEarly Device FailureCSF Leak

WOUND DEHISCENCE / FLAP NECROSISWound dehiscence occurs commonly in an active child.If small leave as such to heal by secondary intensionIf large Secondary closure in OTFlap Necrosis occurs due to aggressive thining of flap most serious complication & require device removal.

CSF LEAKOccurs frequently at the time of drilling tie down holes.Can also occur after opening of scala tympani in case of modiolar defect. / Common cavity deformity. GUSHERSControlled by packing the common cavity with muscle.If still not controlled Ear is closed by plugging the eustachian tube, filling the middle ear & mastoid with fat and oversewing the Extn. Auditory canal.

LATEExtrusion / Exposure of DevicePainDisplacement of ElectrodesLate device failureOtitis MediaMeningitis

MENINGITISCochlear implantation recipients are at high risk of developing Pneumococcal Meningitis.Center for Disease Control made it mandatory for pneumococcal vaccination as follows -All children < 1 yr. must receive 3 doses of Pneumococcal Conjugate (PEVNAR) vaccine.Cochlear implant child > 2 yr who have received PEVNAR should receive one dose dose of pneumococcal polysacharide vaccine.Cochlear Implant child > 5yr should receive one dose of pneumococcal polysaccharide vaccine.

DEVICE ACTIVATION

PROCESSAfter 3 -4 weeks post op when the wound is well healed implantee returns to clinic to have the external parts of the device fitted called HOOK UPThere are 2 types of device stimulation modes BIPOLAR each active electrode paired with another intracochlear electrode.MONOPOLAR It is most preferred mode. Paired with extracochlear electrode.

PROCESS Determination of Threshold level (minimum) & most comfortable loudness level (maximum) for each electrodeThen frequency bands are assigned to each electrode pair by software program.In prelingually deaf child this process is very complicated so recently some objective methods are devised like Neural Response TelemetryStapedial reflex estimationElectrical ABR

Now I am ready to answer your Questions !!!