2nd Yr. PG (ENT)
Cochlear 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.
1800 – 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 response
1972 – 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 IMPLANT
EXTERNAL PART –
2. Speech processor
INTERNAL PART –
1. Receiver – Stimulator
2. Electrode Array
TYPES OF COCHLEAR IMPLANT
3 Types :-
1. NUCLEUS 24 FREEDOM by Cochlear Corporation
2. HI RES 90K by Advanced Bionics
3. PULSAR by Med El
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.
Age – More than 18 yrs
Bilateral severe to profound Sensorineural hearing loss.
Both Advanced Bionics and Med El - severe-to-profound
Cochlear Corporation - moderate-to-profound
Must be Postlingual Deaf
Little or no benefit from hearing aids.
Inner ears must be surgically able to accept the device
Must not have any chronic illness
A deaf adult who never learned to speak does not benefit from a cochlear
Gone are the days when cochlear implantation is done only in
hearing loss above 90 dB
Sentence recognition testing is done in best aided condition at 60 dB
FDA approved sentence lists used are –
1. BKB – SIN sentences in Noise & Quiet
2. Az -Bio sentences
3. CNC monosyllabic words
Maximum score for cochlear implant candidacy varies
Advanced Bionics – 50 %
Cochlear Corporation – 60 %
Med El – 40 %
Age – More than 12 months
Bilateral profound sensorineural hearing loss > 90 dB
No benefit at all with the most optimized hearing aid.
Inner Ear surgically accesible in CT scan
Auditory nerve present in MRI
Post lingual profound deafness caused by meningitis is not a good
candidate for cochlear implant. – neoosteogenesis causing cochlear
AGE 12 – 24 months
Bilateral profound sensorineural hearing loss
Trial 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.
IT-MAIS – Infant Toddler version of
meaningful Auditory Integration Scale
FAPCI - 23-item Functioning after Pediatric
35-item Little Ears auditory questionnaire
PEACH - Parents' Evaluation of
Aural/Oral Performance in Children
The determination of cochlear implant candidacy for older children
is generally based upon either mono- or multi-syllabic word
Early Speech Perception Test
Multisyllabic Lexical Neighbourhood test
HINT Sentences for children < 30 %
WHICH EAR TO IMPLANT
Better hearing ear
Most recently deaf ear
Least obstructed labyrinth
In traumatic hearing loss the ear with reduced labyrinth
Electroacoustic / Hybrid Implant
Combine a cochlear implant with hearing aid.
Indication – Individuals with profound high frequency loss with
retained low frequency hearing
CI – Stimulates basal turn >> High Frequency
Hearing aid amplifies low frequency
A 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
Activation of more than one electrode at same time.
Provide a more natural quality of sound
Only 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
MODIOLUS HUGGING ELECTRODE
Self coiling electrode array with
Comes with a stylete which keeps
the electrode straight during insertion
As it uses low intensity signals –
Extended Battery Life
Can be done as outpatient or inpatient.
Can be done under GA or LA.
IV antibiotics should be given at least 20 minutes before skin
Surgery duration – 3 -5 hrs
Duration of stay in Hospital – 2 days
3 to 4 weeks later – Programming of device
INCISION & SKIN FLAP
Inverted – J shaped incision.
Incision should not cross the edges of
Flap elevated in 2 layers
Periosteum of mastoid is elevated as
an anteriorly based Palva flap.
Skin thickness over implanted
stimulator should be less than 6.0 mm
A 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 stimulator
A channel is also formed for the passage of electrodes to mastoid
Tie down holes are drilled around the well. Dangerous !!!
Device is fixed with sutures in the well.
The 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 !!!
Remove the anterior lip of round window niche.
Apply Lubricant – “Healon” or “Provisc”
The electrode array is inserted as atraumatically as possible with its
tip directed inferiorly.
Cochleostomy sealed with a small piece of soft tissue.
Three layered wound closure done –
Palva flap closed tightly with interrupted absorbable sutures
Superficial flap closed with burying interrupted sutures
Skin closed with Subcuticular sutures.
Facial N. Injury
Alteration of Taste
Wound dehiscnce / Flap Necrosis
Early Device Failure
WOUND DEHISCENCE / FLAP NECROSIS
Wound dehiscence occurs commonly in an active child.
If small – leave as such to heal by secondary intension
If large – Secondary closure in OT
Flap Necrosis occurs due to aggressive thining of flap – most
serious complication & require device removal.
Occurs 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. GUSHERS
Controlled 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.
Extrusion / Exposure of Device
Displacement of Electrodes
Late device failure
Cochlear implantation recipients are at high risk of developing
Center for Disease Control made it mandatory for pneumococcal vaccination
as follows -
All children < 1 yr. must receive 3 doses of Pneumococcal Conjugate
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
After 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
There are 2 types of device stimulation modes –
BIPOLAR – each active electrode paired with another
MONOPOLAR – It is most preferred mode. Paired with
Determination of Threshold level – (minimum) & most comfortable
loudness level (maximum) for each electrode
Then frequency bands are assigned to each electrode pair by software
In prelingually deaf child this process is very complicated so recently
some objective methods are devised like –
Neural Response Telemetry
Stapedial reflex estimation