cochlear implant in ENT surgery

3. BY
DR SOHAIL AHMAD
PGR ENT-1
Cochlear implant

4. DEFINITION
 Cochlear implants are surgically placed
electrical device that receive sound and
transmit the resulting electrical signals to
electrodes implanted in the cochlea of the
ear.
 The signals stimulate cochlea, allowing
patient to hear.
 It is also known as Bionic ear

5. HISTORY
 1790-Alessandro Volta electric signal in
auditory system can create perception of
sound.
 1957-(French-Algerian surgeons Andre
Djourno and Charles Eyries) ; They were
the
first who attempted to produce the first
cochlear implant
 It was single channel device

6. CONT.
 1961- Dr. William F. House, an Otologist
considered the inventor of the cochlear
implant along with John Doyle (a
neurosurgeon) and James Doyle (an
electrical engineer) commenced work on a
single-channel device.
 • It was a single channel device but
speech was modulated by 16 hz carrier.

7. CONT.
 1964- Blair Simmons at Stanford University
implanted some recipients with a six-channel device.
 However, it was Dr. Michelson's patent and ultimate
device, which are thought of as the first cochlear
implants
 December 1984, the Australian cochlear implant
was approved by the United States Food and Drug
Administration to be implanted in adults in the United
States.

8. CONT.
 1990 the FDA lowered the approved age for
implantation to two years, then 18 months in
1998, and finally 12 months in 2000,
although off-label use has occurred in babies
as young as 6 months.
 Cochlear Implant in India-1996 Prof Mohan
Kaneswaran in Madras ENT Research
foundation Chennai
 Cochlear Implant Group of India-Nov 2003

9. BASIC PRINCIPLES
 Cochlear implantation is considered for severe
to profound hearing loss who failed to gain
benefit from hearing aids
 Criteria for implantation are different in adults
and children
 The external part of CI detects sound signals
and converts it into electrical signals which is
transmitted to the internal processor
 There are 35000 auditory nerve fibres in the
auditory nerve

10. CONT
 At least 10000 are required for speech
recognition using cochlear implant.
 The success of implant depends upon the
transmission of signals to the auditory cortex
via auditory pathways from the ear.
 Performance with cochlear implant is
optimized through a process of programming
known as “mapping”

11. SELECTION CRITERIA - CHILDREN
 child above 12months below 7 years in pre –
lingually deaf children.
 At birth the cochlea is fully formed but the
auditory pathway is not. Auditory pathway is
dependent
on stimulation for its maturation and this stimulation
is
vital to acquisition of speech and language skill as
well
as amount of cognitive development.
 Post lingual deaf no age limit

12. CONT.
 degree of deafness- profound >90dB SNHL
with poor discrimination in both ears with
cochlear nerve.
 Respond to hearing aid- in those who do not
benefit from a hearing aid ,at least 3 to 6
months of use.
 Absence of contraindications- cochlear
aplasia or absent cochlear nerves are
absolute contraindications to cochlear
implantation.

13. SELECTION CRITERIA- ADULT
 Severe or profound hearing loss with PTA of
70dB or greater hearing level.
 Little or no benefit from hearing aids
 Aided scores on open-set sentence test of
less than 50%.
 No evidence of central auditory lesions or lack
of an auditory nerve.
 No medical or radiological contraindications for
surgery.

14. SPECIAL CASES
In Adults :
1;Residual hearing:
 Cochlear implant receiving ear gets lost its
residual hearing
 Hearing aid is combined with cochlear
implant to save the residual hearing. This is
called electric-acoustic stimulation.
 Hybrid cochlear implants are used for high
frequency loss.

15. CONT
2;The Elderly
 This group performs well with cochlear
implants with good speech perception and
improvement of quality of life
3;Far Advanced Otosclerosis
It is applied to patients with otosclerosis and
profound hearing loss
cochlear implant gives equal results to
stapedectomy

16. CONT
3; Neurofibromatosis Type 2
 Hearing loss may be secondary to bilateral
vestibular shwannomas or their treatment
 Cochlear implantation can be done if we
save the cochlear nerve during surgery
4; Single Sided Deafness
 In patients with treatment of tinnitis, cochlear
implant improves it and speech recognition
and noice

17. CONT
4; Patients Outside Current Criteria
 These patients get benefit significantly from
CI

18. CHILDREN
1; Additional disabilities
 Patients with these disablities are also
considered for CI
 Cognitive impairment
 Developmental delay
 Visual impairment
 Communication disorders

19. CONT
2; Auditory Neuropathy Spectrum Disorder
 It is characterized by absent auditory brain stem
responses wit normal otoacoustic emissions however
in ANSD hearing may improve over time , so close
observation is advised.
3; Anatomical Abnormalities
 Cochlear nerve aplasia
 Cochlear nerve hypoplasia
 Anatomical variations of facial nerve positioning or
CHARGE Syndrome
 Preoperative assessment should be done with care

20. PREOPERATIVE
EVALUATION

21. MEDICAL EVALUATION
 History
• genetic hearing loss
• auditory neuropathydyssynchrony
• Acquired deafness
 Physical examination

22. AUDIOLOGICAL EVALUATION
 to determine the type and severity of hearing
loss
 testing the unaided air and bone conduction
thresholds, unaided speech discrimination,
speech recognition threshold, speech
detection threshold, tympanometry and
acoustic reflexes. The degree of hearing loss
 The duration of hearing loss
 Benefit from hearing aids

23. ELECTROPHYSIOLOGICAL TEST
 Auditory brainstem response (ABR)-
a)verify audiometric test result
b)identify patient with auditory dyssynchrony
c)rule out possibility of functional deafness

24. SPEECH PERCEPTION TEST IN ADULT
 Monosyllabic test
a)north western university(NU-6)monosyllabic
word test.
b)consonant nucleus test(CNC)
 Sentence material-
a)hearing in noise test(HINT)
b)City university of New York(CUNY)

25. SPEECH PERCEPTION TEST IN
CHILDREN
 The Early Speech Perception (ESP): (Moog
& Geers, 1990)
 The Low Verbal version of the test is
administered to young children (2yrs and up)
 The Standard version is used with older
children.

26. CONT.
 MeaWord intelligibility by picture
identification (Wipi) test; (Ross &Lerman,
1979)
 Craig lip inventory
 meaningful auditory integration scale(MAIS

27. CONT.
 Monosyllabic Trochee Spondee Test (MTS);
Erber And Alencewics; 1976Assesses the
closed set word identification in children with
hearing impairment
 Lexical Neighborhood Test (LNT) (Kirk,
Pisoni, and Osberger, 1993 )
 Test (MLNT) Multisyllabic Lexical
NeighborhoodThis is an open-set test of
multisyllabic word recognition.

28. IMAGING
 High resolution temporal bone computed
tomography
• Inner ear morphology
• Patency of cochlea
• Position of facial nerve
• Location of large mastoid emissary veins
• Size of facial recess
• Height of jugular bulb

29. NORMAL COCHLEA

30. COCHLEAR APLASIA

31. COCHLEAR HYPOPLASIA

32. COCHLEAR OSSIFICATION

33. COCHLEAR IMPLANT IN SITU

34. PSYCHOLOGICAL EVALUATION
 No unrealistic expectations, by both family and
the patient.
 The necessary cognitive and behavioral
skills should been developed for successful
programming .
 The revised form of Wechsler intelligence scale
is available for this purpose.
 If skills not developed –postpone the procedure
- help him to develop the skills

35. FACTORS THAT AFFECT PEDIATRIC
COCHLEAR IMPLANT PERFORMANCE
 Age of implantation
 Hearing experience
 Training with amplification in case of some
residual hearing
 Presence of other disabilities
 Parent and family support.

36. THREE MODES OF STIMULATION OF AUDITORY
SYSTEM INVOLVING COCHLEAR IMPLANT
 Electrical stimulation-complete electric
stimulation when there is no residual hearing in
both ear
 Electroacoustic stimulation- (hybrid
implants) lower frequencies stimulated
acoustically via hearing aid while higher
frequencies electrically via cochlear implant.
 Bimodal stimulation-one ear uses implant
while use a high gain hearing aid on other
ear

37. BILATERAL COCHLEAR IMPLANT
 Localisation
 Head shadow
 Squelch
 Summation
Head shadow effect – when the sound has to
cross the head to reach the other side of the
ear. 6dB loss in sound intensity occurs.

38. DEVICE SELECTION

39. PARTS OF COCHLEAR IMPLANT
 External
Microphone
Speech processor
Transmitter
 Internal
Receiver and stimulator
An array of up to 22 electrodes

43. SPEECH PROCESSOR
 converts acoustical signal coded for
transmission to the internal device.
 The signal is sent via a wire to the transmitter
located on the implant users’ head.
 The method by which a signal sent to the
implant recipient is derived is called the Coding
strategy
 Most cochlear implant systems utilize either a
filter bank or a feature extraction procedure for
coding.

44. CONT.
 In filter bank procedure, the signal is
separated into a number of frequency bands
and transmitted as an analogue input
 The feature extraction procedure focuses on
the aspect of the signal that theoretically
provide the greatest degree of speech
recognition

45. CODING STRATEGY
 Method by which pitch, loudness and timing
of sound are translated into series of
electrical impulses.
 Two types:
Simultaneous
Nonsimultaneous

46. SIMULTANEOUS STRATEGIES
 Activation of more than one electrodes at the
same time.
 Only produced by advanced bionics
 Problem of signals interference
 Benefit from modiolus hugging electrode
arrays

47. NONSIMULTANEOUS STRATEGIES
 Continuous interleaved sampling strategies
stimulate each electrode serially (one after
another).
 No electrode is bypassed.
 Cochlea receive the complete information
about the frequency composition of incoming
signal.
 Faster sequential stimulation –better speech
recognition.
 Available with all three devices

48. ELECTRODE ARRAY
 Consists of electrodes and electrode carrier
 Electrode carrier is the wire which extends
from the receiver to the electrodes
 Electrodes are of 2 types:
 Extracochlear electrodes and intracochlear
electrodes

49. TYPE OF ELECTRODES
 Extra cochlear electrodes :
 Located outside the cochlea such as on the
plate of the receiving coil or placed under the
temporalis muscle.
 Used as a ground source for monopolar
stimulation

50. MODIOLUS HUGGING ELECTRODE
 Modiolus – core of cochlear spiral-ganglion
cells resides their.
 Electrodes in close approximation to
modiolus are referred- modiolus hugging
electrodes.
 Placed with stylette - keeps the electrodes
straight, stiff - easily inserted- stylette
withdrawn-springs back into its original
configuration-tightly around the modiolus.

52. SPECIAL ELECTRODE ARRAYS
 Compressed array-same no. of electrodes
compressed into 60% of length.
 Useful for patients with labyrinthitis ossificans.
 Less overlap of electrodes using compressed
electrodes array.
 Double arrays-designed for subjects with
labyrinthitis ossificans.
 Separate cochleostomies are performed into the
inferior and middle turn of cochlea.

53. INSERTION DEPTH:
 The mean length of human being cochlea is
33– 36 mm.
 the implants don't reach to the apical tip . It
may reach up to 25 mm which corresponds
to a tonotopical frequency of 400hz

54. NUCLEUS 24 FREEDOM
N6 WITH CONTOUR ADVANCE ELECTRODE
 Manufactured by cochlear ltd. Sydney,
Australia
 Uses flexible silicone housing surrounds
titanium case for reciever/ stimulator
 Age 12months
 Electrode arrray is curved consist of 22 half
banded platinum electrodes space over
15mm
 MRI compatibility -1.5 T with replaceable

56. ADVANCED BIONICS HI RES SYLMAR
 Electrode (hifocus 1j) system –banana
shaped curved towards Modiolus
 Age :12 months
 No. of electrodes: 16 spaced at 1.1mm over
17mm.
 No. channels :16
 MRI compatibility-1.5 T with magnet
removed

58. MED-EL PULSAR INNSBRUCK
,AUSTRIA
 Age 12 yrs
 Reciever/stimulator housed in titanium case
that is 25.4mm wide :45.7mm long.
 No.of electrodes:26
 No. of channels:12
 MRI compatibility-1.5T

60. VACCINATION
 Two vaccines available
 PPV-23(pneumoccocal polysacharide vaccine)
 PCV-13(pnemococcal conjugated vaccine)
 Children <2 yrs-receiving implant should
receive PCV13
 CHILDREN >2yrs who have completed PCV-
13
should receive PPV23
 Child planned for implant should be up to date
on age-appropriate pnemococcal vaccination
>2 weeks before surgery if possible.

61. CONT.
 all children should receive three doses of
pneumococcal conjugated vaccine before age of
one
 Children aged 24--59 months who have not
received PCV13 should receive PCV13 2month
apart and one dose of PPV23 2month later
 Children who have completed the PCV13
series should receive PPV23 >2 months after
vaccination
with PCV13.
 Persons aged 5--64 years should receive
PPV23 a single dose is indicated

62. SURGICAL PROCEDURE
 Incision and skin flap
 Incision may be C-shaped ,inverted U,
Jshaped.
 The flap is elevated, it includes periosteum
of the mastoid, temporalis fascia, and
temporalis muscle.
 Flap thickness should not be greater than
6mm.

63. C- Shaped incision

64. Inverted
U

65. INVERTED
-J -
INCISION

68. THE WELL
 For the placement of stimulator.
 More superior placement in small children in
the area temporal squama, in adults occipital
portion of temporal bone.
 In children stimulator placed over exposed
Dura.
 Channel formed over the bone to pass the
electrode lead.
 During drilling the well and tie down holes the
CSF leak may occur.

71. MASTOIDECTOMY
 It is performed after creating the site for well.
 The mastoidectomy cavity should not be
saucerized as edges help to retain the electrode
leads.
 Facial recess is identified and widely opened .
 Care should be taken of the anomalous facial
nerve.. Or absent facial nerve.
 The most inferior part facial recess is important
for visualization of round window niche

72. COCHLEOSTOMY
 Round window niche is clearly seen after
opening the facial recess.
 Cochleostomy is created inferior to inferior
attachment of round window membrane.
 The size of cochleostomy varies between
0.8 mm to 1.2mm in diameter.

75. INSERTION OF ELECTRODE ARRAY
 When device is brought into operative field the
monopolar cautery is to be removed.
 The electrode array is inserted into the cochleostomy.
 The tip of the electrode array should be directed
inferiorly so that it will slide along the lateral wall of
the scala tympani.
 Lubricant like healon and mixture of water and
glycerine is used .
 Incomplete insertion may occur in cases of
labyrinthine ossificans.

77. FIXATION
 The stimulator is fixed to skull with sutures.
 Drill holes are made above and below the
receptacle site and sutures are passed through
them.
 It can cause perforation and CSF leak in
children.
 Alternatively a strip of material is placed over
the stimulator secured with miniplates.
 Nonabsorbable material like gortex or
absorbable material like alloderm can be used.

79. THE SKIN INCISION IS CLOSED IN LAYER

80. PRECAUTIONS:
 Device should be handled gently.
 Monopolar cautery should be discarded
when device is brought into operative field.
 Surgeon should have the clear view of round
window and should be assure about scala
tympani.

81. MIDDLE CRANIAL FOSSA APPROACH
 Number of surgeons capable of performing
this approach are limited.
 Post lingually deafened adult
 Individuals who have open canal wall down
mastoidectomy cavities.

82. VERIA TECHNIQUE
 Non mastoidectomy technique
 Done through endaural route for
cochleostomy
 Transcanal tunnel drilled in the posterior
canal wall
 Faster healing,ealier fitting of the processor
 Minimise trauma to facial nerve

85. POST-OP COMPLICATIONS
 Facial nerve injury- ,incidence is less than
1%.however minor paresis of facial
nerve is uncommon.
 May occur in patients with anomalous facial
nerve associated with dysplastic semicircular
canal.
 Taste disturbance due to injury to chorda
tympani.
 Hematoma- formation of more than 10cc
requires evacuation.

86. INFECTIONS
 Generally trivial and can be handled by
gently opening the wound and treating with
antibiotics.
 Device removal is not required.

87. WOUND DEHISCENCE:
 If small can be left to heal by secondary
intention or secondary closure can be done.
 Flap necrosis-most serious complication –
device
removal may be required. It occurs in cases
of
aggressive thining of flap.
 Scalp rotation flap ,temporoparietal facial
flap canbe required.

88. EARLY DEVICE FAILURE:
 Out of box failure
 Due to factory defects or during surgical
manipulation.
 Extracochlear implantation can occur when
hypotympanic cells are mistaken for scala
tympani.
 The electrode array may get migrated after
correct placement.
 Most common cause of displaced electrode is
movement of electrodes array after drill out
procedure

89. CEREBROSPINAL FLUID LEAK:
 Can occur when placing the stimulator, more
likely in young children as skull is very thin.
Also occurs during drilling for tie down
sutures.
 Can also occur during opening the scala
tympani. Chances are increased when
cochlear
dysplasia is there.

90. CONT.
 This can be treated by packing the common
cavity with muscle tissue.
 If this does not controls the leak the ear
must be closed by plugging the eustachian
tube filling the middle ear and mastoid with
fat.

91. VERTIGO :
 Incidence is less than 10%.
 It gets resolved with in few weeks by itself.
 BPPV occurs more commonly
 Bilateral implantation causes bilateral
vestibular hypofunction

92. MENINGITIS:
 Individuals with CSF leak and inner ear
malformations are at more risk.
 Lumbar puncture is required for diagnosis.
 Broad spectrum antibiotics are started.

93. LATE COMPLICATION
 Extrusion or exposure of the device:
 Suture line should be kept away from the
edges of the implant.
 Repair must remove skin to avoid suture line
that parallel the implant edge closer than 1-
1/2 cm
 A pericranial flap should be rotated to fully
cover the device with or without a
temporoparietal flap

94. DISPLACEMENT :
 Due to physical injury.
 During scar formation.
 Assessed by fine cut CT of the temporal
bone.

95. LATE DEVICE FAILURE:
 Usually due to internal device failure-due to
trauma or spontaneously.
 External component is first replaced,
sometimes that solves the problem - fine cut
CT of temporal bone to look for the position
of stimulator and electrodes.

96. RARE COMPLICATIONS
1.Magnet displacement
It occurs due to trauma. Magnet is displaced
from the silicon cover. The connection between
the external and internal component is cut off
and xray confirms the diagnosis. A revision
procedure is done

97. CONT
2.Tip fold over
It involves a few electrodes, it is detected on
imaging. Revision procedure may be done to
salvage the existing electrode by removing and
reinserting it.

98. DEVICE ACTIVATION
 2 to 4 weeks postoperatively,
 referred as hook up”
 Determine stimulation mode-
a)bipolar mode –active electrode paired with
another electrode in intracochlear electrode
array,narrow band of stimulation.
b)monopolar mode-electrode in cochlea is
grounded to extracochlear electrode,resulting in
wide current spread

99. CONT.
 Programming of device requires-threshold level
and most comfortable loudness level for each
active electrode.
 Objective method to assess threshold
a) neural response telemetry(NRT)-use
radiofrequency telemetry to measure the action
potential in auditory nerve.
b)Electrical ABR
c)Stapedius reflex-stapedius reflex correlate
with most comfortable loudness level.

100. FUTURE PROSPECTUS
1. Unmet need
In UK 74% of eligible children receive an
implant
between 0 to 3 years of age and 94% by the
age of 17 years.
In Pakistan the people are very poor and they
do not afford the facility for their children.
So, it should be discussed at higher levels in
political and financial structures and laws
should be made for such persons to provide
the facility

101. CONT.
2.New technology applied to current devices
Web based connections are used between the
implant audiologist and the patient.
In future, software may allow the computer literate
patient to alter his or her on map without any
external input
3.Developing technologies
 Totally implantable cochlear implant
It is safe and effective

102. CONT
 Drug eluting electrodes
Anti inflammatory and neurotrophic agents
are introduced into the inner ear to prevent
post implantation neural degeneration or
progression of deffness
 New insertion technologies
Atraumatic insertion
use of robots ensure a smooth insertion

103. CONT
 New methods of neural stimulation
At present , cochlear implant transmits electrical
signals through multiple electrodes and causes current
spread meaning that neural stimulation is not specific.
Research is going on to stimulate only the auditory
pathway.
 Inner ear treatment
Treatment of the etiology
Current research about the role of stem cells and gene
therapy

104. AUDITORY REHABILITATION AFTER
COCHLEAR IMPLANT
 Detection
 Discrimination
 Identification
 Comprehension
 Auditory feedback loop (imitation or
approximation of speech sound)

105. CONT.
 Children with implants need the implant
system to be working well, and it should be
worn consistently in good listening conditions
when good communication opportunities are
available.
 Keep all external parts in good functioning
order and working with an audiologist who
specializes in CI on a regularly scheduled
basis .

106. CONT.
 to be successful in mainstream education
classroom situation should be appropriate
and has good acoustic and the technology is
successfully managed .