Adult cochlear implants Al Basra General Hospital

1. Cochlear Implant
in adult
PREPARED BY
DR. SAIF M.DEHIES
MB.CH.B
SHO ORL-HNS
• Structure
• Classification
• Speech processing strategies
• Candidacy
• Ear selection
• Contraindication
• complication

2. Referance :
Scott-Brown's Otorhinolaryngology, Head and Neck Surgery
7th edition
Andrew H Marshall Bsc MBBS FRCS
Consultant Otolaryngologist
Department of Otorhinolaryngology and Head and Neck Surgery
University Hospital
Nottingham, UK
Cummings Otolaryngology Head & Neck Surgery
FIFTH EDITION
Thomas J. Balkany, M.D., F.A.C.S., F.A.A.P.
Hotchkiss Professor and Chair
Department of Otolaryngology
Professor of Neurological Surgery and Pediatrics
University of Miami Miller School of Medicine
Chief of Service , Division of Otology
Jackson Memorial Hospital
Miami, Florida
COCHLEAR IMPLANTS
Fundamentals and Applications
Graeme Clark
The University of Melbourne and The Bionic Ear Institute,
East Melbourne, Victoria, Australia
Key topics in otolaryngology 2nd edition
N.J Roland
MD ,FRCS ,
CONSULTANT ORL-HNS
HONORARY LECTURER ,LIVERPOL UNIVERSITY , UNIVERSITY HOSPITAL AINTREE, LIVERPOOL , UK

3. Components of a Cochlear Implant
Current CI device consist of 2 parts :
A - External component
1. Microphone :simply receives and transduces sound into an electrical
representation. This is done in an analog fashion. Its hooked behind
the ear
2. The speech processor : (body worn ) this use various processing
strategies & then send the processed signal to :
3. The transmitting coil :held on the scalp behind the ear by a magnet
to the implanted part of the device and sends the processed signal
to the receiver via radiofrequency.
B - Surgically implanted Internal component:
1. The receiver : surgically placed in a well over the mastoid, receives
the signal and sends electrical energy to one or many electrodes in
the array.
2. The electrode array, which lies within the cochlea, delivers the
electric signal to electrodes along its length. The electrical field
generated at these locations serves to discharge the neural
components of the auditory system.

5. The external speech processor and signal-transfer hardware use the
follownig steps to shapes the electrical signal :
1 – Amplification : this increase signal levels to the point that they can
be used in the electrical circuits.
2 - Compression : second step of signal modulation. The normal human
ear can hear sound intensity in a range of 120 dB. Persons with severe to
profound hearing loss do not have this same range. In the high
frequencies their dynamic range (the difference between their absolute
threshold and painful sound) can be only 5 dB! The range in the lower
frequencies is often 10-25dB. This means that significant compression of
the sound energy must take place in order to render it useful. all
cochlear implants employ gain control of one kind or another. These
systems monitor the output voltage and adjust the ratio of compression
to keep the output in a range where it provides useful, but not painful
stimuli.
3 - Filtering : this allows for removal of the unimportant frequencies &
keep the usefull frequencies of interest to be separately modified. This
information can then be analyzed for speech patterns and channeled to
the appropriate portion of the electrode array.

6. Speech Anatomy :
• Spectral (pitch) information
• Temporal (loudness ) information
The speech signals
have 2 main
components:
• F0 is fundamental frequency
• F1 & F2—contribute to vowel identification
• F3—l,r (lateral and retroflex glides)
• F4 & F5—higher frequency speech sounds
• Some speech based on amplitude—k, f, l, s
• The original stratigies based on extracting
vowel & fundamental formant information are
now obsolete .
Formant
frequencies:

7. Types of Cochlear Implants
Single channel vs. Multiple channels:
• In SCCI there is one or more electrodes with the electrical stimuli pass to them all
so it have single channal
• In MCCI typically use 22 pair of electrodes with multible channal ( 4-8) with
subseqent better sence of pitch
Monopolar vs. Bipolar CI
• Monopolar CI have only one ground electrode to all the other which located at or
outside the RW
• Bibolar CI have ground electrode for each pair of electrodes
• many implants offer both grounding methods.
Speech processing strategies
• Spectral peak (Nucleus)
• Continuous interleaved sampling (Med-El, Nucleus, Clarion)
• Advanced combined encoder (Nucleus)
• Simultaneous analog strategy (Clarion)

8. Speech Processing Strategies
1-The S-PEAK strategy ( spectral peak )
• is by filtering sound into 20 different bands covering the range of 200
Hz to 10,000 Hz.
• Each filter corresponds to an electrode on the array.
• The outputs for each filter are analyzed and those channels of highest
amplitude that contain speech frequencies are stimulated.
• The stimulus rate is equal to the period of the lowest frequency of
speech (F0).
• The dominant speech frequency between 280 and 1000 Hz (F1) is then
identified and the appropriate apical electrode is stimulated.
• The dominant speech frequency between 800 and 4000 Hz (F2) is then
identified and the appropriate basal electrode is stimulated.
• 3 additional high frequency filters measure input in the 2000-2800 Hz,
2800-4000 Hz, and >4000 Hz ranges. Stimulus is sent to apical
electrodes (in order to take advantage of the greater incidence of
ganglion cell survival at the apex of the cochlea). These channels
provide additional cues for consonant perception and environmental
sounds.

9. The continuous interleaved sampled (CIS) strategy
• employed by the Clarion and MED-EL systems.
• This system works by filtering the speech into 8 bands.
• The bands with the highest amplitude within the speech frequencies are subsequently
compressed and their corresponding electrodes are stimulated.
• The CIS strategy uses high-rate pulsatile stimuli to capture the fine temporal details of
speech.
The advanced combined encoder (ACE) strategy
• filters speech into a set number of channels and then selects the highest signals for
each cycle of stimulation.
• Stimulation is carried out in a very rapid fashion (much faster than the SPEAK strategy
The simultaneous analog strategy (SAS)
• closely mimics the normal ear.
• All incoming sound is compressed and filtered into 8 channels.
• These channels are then simultaneously and continuously presented to the
appropriate tonotopic electrode.
• There is no effort to select for speech frequencies.
• Intensity is coded by either stimulus amplitude, rate or both.

10. The SAS strategy has met with limited success, whereas the SPEAK and CIS
strategies have been relatively successful.
recent advances have made it possible for one cochlear implant to offer several
speech processing strategies in the same implant .This allows the audiologist
and patient to choose what strategy is best for that individual .
Currently, the Nucleus systems are made to employ several processing
strategies .
The Clarion systems use CIS to stimulate in a monopolar fashion as well as
simultaneous analog stimulation (SAS).
Medical Electronic (Med-El) produces a product (currently in USA clinical trials)
with 12 electrode pairs suitable for deep insertion that relies on the CIS
strategy with the most rapid stimulation rate of all implants.

11. Candidature for CI
It’s the process of selecting appropriate individuals for implantation. The
selection criteria may be considered under the following headings:
1-Age :no upper age limit for CI as long as the recipient is in good health.
2-Audiological & vestibular candidature :
• The most important is the audiological performance in aided & un
aided state
• Current agreed audiological criteria in UK include failure to achieve
aided score more than 30% on BKB sentence list _ in USA a more
relaxed criteria of BKB aided score of up to 40% .
• The duration of deafness in postlingually deafened adult is important
as prognostic indicator with respect to outcome
• Loss of vestibular function may accompany the hearing loss particularly
after meningitis.. So in adult a caloric test is needed to asses the
vestibular function especially if CI is to be undertaken in the ear with
the better or the only vestibular function
3-Otological :
• Exclude the presence of active ontological disease
• Cochlear obliteration duo to meningitis or cochlear otosclerosis may
require modification to the surgical procedure.

12. 4-Medical :
the most important criterion is absence of significant life-limiting
disease. In general terms, the patient should be fit enough to undergo a
relatively prolonged general anesthetic for the implant surgery.
5-Imaging :
is a mandatory step in assessment
both MRI (with 3D reconstruction of T2 image ) & HRCT are used in the
pre op assessment
• MRI is more accurate in identifying cochlear dysplasia ,LVA & the
presence of the cochlear nerve while both are of equal value in
detecting cochlear patency in case of labrynthitis ossificance .
6-Psychological :
the most important criterion should be the absence of major
psychological or psychiatric disorder.
• However deafness itself may engender some psychological problems
& improvement may be seen in certain measures of psychological well-
being after CI

13. Contraindication to adult CI
1- Incomplete hearing loss for example a patient with sever to profound hearing loss with residual hearing
in the 2000 kz frequency.
2- Neurofibromatosis type II , mental retardation , psychosis , organic brain dysfunction & unrealistic
expectation.
3- Active middle ear disease .. Need to be controlled prior to surgery.
4- Radiological finding of cochlear agenesis ( michel deformity ) or small IAC (8th cranial nerve agensis ) is a
contraindication to CI on that side
Other form of dysplasia is not a contraindication to CI but modification of surgery is required with informed
consent about higher risk for complication as CSF leak & meningitis
5- Patient with CWD mastoidectomy .. may need surgery to reconstruct the posterior canal wall or close
off the canal before implantation.
6- Labyrinthitis ossificans is a relative contraindication when there is a patent contralateral basal turn.
usually identifiable on CT scan but MRI is often better at delineating patency of the cochlea
Note : Adults and children with acute meningitis should be treated with steroids to avoid hearing loss.
Those that sustain hearing loss secondary to meningitis should be observed for 6 months before
implantation due to the substantial number of patients that will regain their hearing in at least one ear.
7- advanced otosclerosis seen on CT cause ossification of the basal turn of the cochlea. This is not a
contraindication as long as the surgeon is prepared to perform a drill to put the implantation into the scala
vestibule.
Patients with otosclerosis can achieve excellent results from implantation.

15. After surgery :
• The initial switch on of the device occur
after about 4 weeks when all the post
operative scalp swelling has settled &
the wound healed.
• For several weeks then after an intensive
program of auditory & speech training
takes place with fine tuning of the
speech processing map of the individual
.
• The rehabilitation process continues for
several m. in adult and years in children.
Rehabilitation
:

16. Complication :
1- Surgical Cx : the complication rate for individual surgeons is greatest during their first 30 cases.
2- FACIAL NERVE STIMULATION
• Facial nerve stimulation has been reported to occur in between 7 - 25 percent. This is noted
more frequently in patients with otosclerosis,
• can be controlled by device reprogramming in nearly all cases.
3- DEVICE FAILURE
• one of the more common problems, although it should not be considered as a surgical
complication, the cause rarely being surgical mismanagement.
• reimplan-tation is safe and effective
4- VERTIGO
• Seen in three-quarters of adults with implants,
• relieved by vestibular therapy.
• MENINGITIS :risk factors for developing meningitis included young age, cochlear dysplasia and
temporal bone abnormalities.
5- Non auditary stimulation : pain in the ear ,scalp or the throat , intrusive tinitus
• Treated by programing out the offending electrods