Cochlear implant

1. Cochlear implant
DR DISHA
SHARMA
JR ENT-HNS
IGMC,SHIMLA

2. Definition
O 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.
O The signals stimulate cochlea, allowing
patient to hear.
O It is also known as Bionic ear.

3. HISTORY

4.  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
the first
first who attempted to produce
cochlear implant
 It was single channel device .

5.  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.

6. 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.

7.  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

8. Selection criteria - children
O 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

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

10. Selection criteria- adult
O Severe or profound hearing loss with PTA of
70dB or greater heaing level.
O Little or no benefit from hearing aids
O Aided scores on open-set sentence test of
less than 50%.
O No evidence of central auditory lesions or
lack of an auditory nerve.
O No medical or radiological
contraindications for surgery.

11. PREOPERATIVE
EVALUATION

12. O Medical evaluation
History
• genetic hearing loss
• auditory neuropathydyssynchrony
•Acquired deafness
Physical examination-

13. O Audiological evaluation
O to determine the type and severity of
hearing loss
O 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
O The duration of hearing loss
O Benefit from hearing aids

14. Electrophysiological test
O Auditory brainstem response (ABR)-
O a)verify audiometric test result
O b)identify patient with auditory
dyssynchrony
O c)rule out possibility of functional deafness

15. Speech perception test in adult
O Monosyllabic test-a)north western
university(NU-6)monosyllabic word test.
b)consonant nucleus test(CNC)
O Sentence material-
O a)hearing in noise test(HINT)
b)City university of New York(CUNY)

16. Speech perception test in
children
O The Early Speech Perception (ESP): (Moog &
Geers, 1990)
O The Low Verbal version of the test is
administered to young children (2yrs and
up)
O The Standard version is used with older
children.

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

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

19. O 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

21. Magnetic resonance imaging
O Labyrinthine ossifican
O Cochlear nerve
O CNS abnormalities

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

24. Factors that affect pediatric
cochlear implant performance.
O Age of implantation
O Hearing experience
O Training with amplification in case of some
residual hearing
O Presence of other disabilities
O Parent and family support.

26. Three modes of stimulation of auditory
system involving cochlear implant
O Electrical stimulation-complete electric
stimulation when there is no residual
hearing in both ear
O Electroacoustic stimulation- (hybrid
implants) lower frequencies stimulated
acoustically via hearing aid while higher
frequencies electrically via cochlear implant.
O Bimodal stimulation-one ear uses implant
while use a high gain hearing aid on other
ear

27. Bilateral cochlear implant
O Localisation
O Head shadow
O Squelch
O 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.

28. Device selection

29. Parts of cochlear implant
O External
O Microphone
O Speech processor
O Transmitter
O Internal
O Receiver and stimulator
O An array of up to 22 electrodes

32. Parts of cochlear implant
O External
O Microphone
O Speech processor
O Transmitter
O Internal
O Receiver and stimulator
O An array of up to 22 electrodes

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

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

35. Coding strategy
 Method by which pitch, loudness and timing
of sound are translated into series of
electrical impulses.
Two types:
 Simultaneous
 Nonsimultaneous

36. Simultaneous strategies
 Activation of more than one electrodes at
the same time.
 Only produced by advanced bionics
electrode
 Problem of signals interference
 Benefit from modiolus hugging
arrays

37. 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.
–better speech
 Faster sequential stimulation
recognition.
 Available with all three devices .

38. Electrode Array
O Consists of electrodes and electrode carrier
O Electrode carrier is the wire which extends
from the receiver to the electrodes
O Electrodes are of 2 types:
O Extracochlear electrodes and intracochlear
electrodes

39. Type of electrodes
O Extra cochlear electrodes :
O Located outside the cochlea such as on the
plate of the receiving coil or placed under
the temporalis muscle.
O Used as a ground source for monopolar
stimulation

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

41. are inserted next to
Electrodes
modiolus

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

43. O Insertion depth:
O The mean length of human being cochlea is 33–
36 mm.
O the implants don't reach to the apical tip . it
may reach up to 25 mm which corresponds to a
tonotopical frequency of 400hz

44. 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
magnet

46. 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

48. Med-el Pulsar Innsbruck
,Austria
 Age 12 yrs
 Reciever/stimulator housed in titaniumcase that is
25.4mm wide :45.7mm long.
 No.of electrodes:26
 No. of channels:12
 MRI compatibility-1.5T

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

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

52. Surgical procedure
Incision and skin flap
o Incision may be C-shaped ,inverted U, J-
shaped.
o The flap is elevated, it includes
periosteum of the mastoid, temporalis
fascia, and temporalis muscle.
o Flap thickness should not be greater than
6mm.

54. C- Shaped incision

55. Inverted
U

56. INVERTED
-J -
INCISION

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

62. 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.

63. 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.

66. 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.

68. 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.
 Alternatevely a strip of material is placed over
the stimulator secured with miniplates.
 Nonabsorbable material like gortex or
absorbable material like alloderm can be used.

70. The skin incision is closed in layers.
From Advanced Bionics

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

72. Middle Cranial Fossa approach
O Number of surgeons capable of performing
this approach are limited.
O Post lingually deafened adult
O Individuals who have open canal wall down
mastoidectomy cavities.

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

77. Post-op complication
 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.

78.  Generally trivial and can be handled by gently
opening the wound and treating with antibiotics.
 Device removal is not required.
Infections
:

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

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

81. 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.

82. O This can be treated by packing the common cavity with
muscle tissue.
O 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.

83. Balance disturbances :
O Incidence is less than 10%.
O It gets resolved with in few weeks by itself.

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

85. 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.
Late complication

86. Displacement :
 Due to physical injury.
 During scar formation.
 Assessed by fine cut CT of the temporal bone.

87. Late device failure:
O Usually due to internal device failure-due to trauma
or spontaneously.
O 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.

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

89. O Programming of device requires-threshold level
and most comfortable loudness level for each
active electrode.
O 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.

90. Auditory rehabilitation after
cochlear implant
O Development of speech preception with
training in implant listeners.
O Programs of auditory training in children
are with implant are often organised with
hierarchic approach by which the child
learns to associate meaning with unfamiliar
and unnatural sounds

91. Auditory training in children
with cochlear implant
O Detection
O Discrimination
O Identification
O Comprehension
O Auditory feedback loop (imitation or
approximation of speech sound)

92. O 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.
O Keep all external parts in good functioning
order and working with an audiologist who
specializes in CI on a regularly scheduled
basis .

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