Thesis on inventions and it's neuroscience

1. Cochlear implants
Moderator : Dr Karthik S

2. WHAT ARE COCHLEAR IMPLANTS???
 electronic devices that convert mechanical
sound energy into electric signals that can be
delivered to the cochlear nerve in profoundly
deaf individuals.
 The devices seek to replace a nonfunctional
inner ear hair cell transducer system.

3. The Fundamental Concept of
Cochlear Implant
To bypass the damaged
hair cells.

4. Cochlear Implant History

5.  The first attempt to develop a clinical CI was
in 1957 by Djourno and Eyriès. A recipient
was implanted with a single channel device.
 In 1961, Dr. William F. House, considered the
inventor of the cochlear implant, John Doyle
(a neurosurgeon) and James Doyle (a physicist)
commenced work on a single-channel device
in Los Angeles.

6.  1985 - United States Food &Drug
Administration granted the first approval for
implantation in adults
 1990 - FDA granted approval for cochlear
implants in children

7. How is a Cochlear Implant
Different from a Hearing Aid?
• Hearing Aids:
– acoustically amplify sound
– rely on the responsiveness of surviving hair cells
• Cochlear Implants:
– bypass damaged hair cells
Convert the acoustic input signal into electrical impulses to stimulate
the auditory nerve fibers in the cochlea.

8. Four Basic Parts of a
Cochlear Implant
 A microphone, which picks
up sound from the
environment;
 A speech processor, which
selects and arranges
sounds picked up by the
microphone;

9. Microphone/Speech Processor/Induction
Coil
Source: www.cochlear.com

10.  A transmitter and receiver/ stimulator, which
receive signals from the speech processor
and convert them into electric impulses.
 Electrodes, which collect the impulses from
the stimulator and send them to the brain.

11. Source: www.cochlear.com
Electrodes

14. How Does a CI Work?
 Sound is received by an microphone that
rests over the ear like a behind-the-ear
hearing aid.
 Sound is sent from the microphone to the
signal processor by a thin cable.
 Signal processor translates the sound into
electrical codes.
 Codes are sent by a thin cable to the
transmitter held to the scalp by its attraction
to a magnet implanted beneath the skin.

15.  Transmitter sends codes across the skin to a
receiver/stimulator implanted in the mastoid
bone.
 Receiver/stimulator converts the codes to
electrical signals.
 Electrical signals are sent to the specified
electrodes in the array within the cochlea to
stimulate neurons.
 Neurons send messages along the auditory
nerve to the central auditory system in the
brain where they are interpreted as sound.

16.  The presence of viable auditory nerve fibres is
fundamental to the success of CI.

17.  The electric connection across the skin
between the implanted electrode and the
processor is accomplished via a system of
induction coils in the majority of devices but
may also be accomplished by a direct wire
connection (percutaneous plug).

18. COCHLEAR IMPLANT DEVICES
AVAILABLE
 There are currently three CI systems in
widespread use at present worldwide:
1. Cochlear system, produced by Cochlear Ltd
of Sidney, Australia;
2. Med-El system produced by Med-El of
Innsbruck, Austria;
3. Clarion system, produced by Advanced
Bionics of California, USA.

19.  Originally, there were differences in
construction of the three devices with the
Nucleus comprising a titanium case with a
covering of silastic in the first case ;
 the other two devices were of ceramic
construction.

20. The implanted electrodes differ according to
 The number of channels that are
stimulated (single channel or
multichannel)
 Their electric configuration
(monopolar or bipolar)
 Their site of placement
(extracochlear or intracochlear)

21. Single channel system
 During analog transformation, the speech
waveform or a derivative of it is presented to
the cochlear nerve.
 This strategy, which is used by single-
channel cochlear implants, provides primarily
temporal and intensity information.

22.  An example of this analog transformation
scheme is the 3M/House device, which
incorporates an amplitude-modulated 16 kHz
carrier wave that is passed through a
bandpass filter (200 to 4000 Hz).

23. Multichannel system
 Multichannel cochlear implants attempt to
produce tonal percepts by "place pitch“
mechanisms by stimulating different
locations in the cochlea and thus more
discretely stimulating the central nervous
system.

24.  The bandpass filter scheme separates the
acoustic signal into discrete frequency bands,
which are then delivered to multiple
electrodes along the cochlear array .
 This technique provides spectral information
in addition to temporal and intensity cues.

25. Patient Selection

26. ADULTS -18 years old and older (no
limitation by age)
◦ Bilateral severe-to-profound sensorineural hearing
loss (70 dB hearing loss or greater with little or no
benefit from hearing aids for 6 months)
◦ Psychologically suitable
◦ No anatomic contraindications
◦ Medically not contraindicated

27. Adults
 Cochlear implantation neither eliminates an
underlying disease state nor restores normal
function to the end organ of hearing.
 Therefore an objective view of risk/benefit
ratios must serve to guide clinical decisions.

28.  initially limited to postlingually deafened
adults who received no benefit from hearing
aids and who had no residual hearing.
 Implantation of an ear with any residual,
aidable hearing carries the risk that the
implanted ear could be made worse than that
ear with a hearing aid.

29. Which ear to implant
 Current investigations performed under US Food and Drug
Administration (FDA) guidelines are testing the hypothesis that
an ear with some residual hearing may have a better neuronal
population, increasing the likelihood of superior performance
with a cochlear implant, especially with more complex
multichannel stimulation.

30.  Radiologic examination of the
cochlea is performed to determine
if the cochlea is present and
patent and to rule out a
congenital deformity of the
cochlea.
 High-resolution, thin section CT
scanning of the cochlea is the
current imaging technique of
choice .

31.  Intracochlear bone formation as a
result of labyrinthitis ossificans
can usually be demonstrated by
CT scanning.
 However, sclerosing labyrinthitis
with soft tissue obliteration may
not be accurately imaged.

32.  In these cases magnetic resonance imaging (MRI)
is an effective adjunctive procedure to provide
additional information regarding cochlear
patency.
 T-2 weighted MRI will demonstrate loss of the
endolymph/perilymph signal in sclerosing
labyrinthitis.

33.  Intracochlear ossification (labyrinthitis
ossificans) is not a contraindication to
cochlear implantation but can limit the type
and length of the electrode array that can be
introduced into the scala tympani of the
cochlea .

34.  When temporal bone fracture has resulted in
deafness, CT scanning may provide valuable
information predicting the integrity of the
cochlear nerve.
 This may be confirmed by electrophysiologic
testing .

35. CT MRI
Morphology of cochlea and SCC ++ +++
Potency of cochlear duct + ++
Status of cochlear nerve - +++
Anatomy of fallopian canal ++ +
Defect of modiolar + +++
Defect of cribriform area +++ ++
Enlarged vestibular aqueduct ++ +++
Enlarged cochlear aqueduct +++ +
Presence of round and oval window +++ -
CNS abnormalities +++

36.  No upper age limit is currently used in the
selection process.
 Cochlear implantation is appropriate if other
selection criteria are met and the patient's
general health will permit an elective surgical
procedure under general anesthesia.
 It is anatomically feasible to implant patients
as young as 2 years of age or possibly even
younger.

37. Audiologic assessment
 The audiologic evaluation is the primary
means of determining suitability for cochlear
implantation.
 Performance with an appropriate, highpower
hearing aid is compared to expected
performance with an implant.

38.  As a general guideline, if a patient cannot
attain an aided speech detection threshold of
70 dB SPL (approximately 53 dB HL) or better,
 performs very poorly on discrimination tests
with a hearing aid, or
 both, a cochlear implant is likely to provide
greater benefit.

39. Psychological assessment
 Psychologic testing is performed for
exclusionary reasons to identify subjects with
organic brain dysfunction, mental retardation,
undetected psychosis, or unrealistic
expectations.

40. Indications for Cochlear
Implantation -Children(12
months or older)
 Bilateral severe-to-profound sensorineural
hearing loss with PTA of 90 dB or greater in
better ear
 No appreciable benefit with hearing aids
 Must be able to tolerate wearing hearing aids
and show some aided ability
 No medical or anatomic contraindications
 Motivated parents

41.  Of paramount significance is a commitment
of the child's family and educational setting
towards providing an appropriate
environment and training setting.
 An intact and functioning communication
mode is invaluable in initiating the
rehabilitation process.

42.  The currently accepted minimum age limit of
2 years was initially chosen for anatomic
reasons.
 The cochlea is adult size at birth, and by age
2 years the mastoid antrum and facial recess,
which provide access to the middle ear for
active electrode placement, are adequately
developed.
 From a neurodevelopmental viewpoint an
even younger age limit may be desirable.

43.  However it is difficult to determine with
certainty that a child in the 2- to 3-year age
group is totally deaf and cannot benefit from
a hearing aid.
 For this reason, a prolonged hearing aid trial
under close observation with appropriate
aural rehabilitation is desirable for most
children.

44.  An otologically stable condition should be
present before considering cochlear
implantation in children.
 Because children are more prone to otitis
media than adults, justifiable concern has
been expressed that a middle ear infection
could cause an implanted device to become
an infected foreign body requiring its removal.

45.  infection might extend along the electrode
into the inner ear, resulting in a serious
otogenic complication such as meningitis or
further degeneration of the central auditory
system.

46.  The management of middle ear effusions in
children either under consideration for
cochlear implantation or who already have
cochlear implants deserves special
consideration.

47.  A noninfected middle ear is a preoperative
prerequisite.
 Conventional antibiotic treatment will usually
accomplish this goal.
 When it does not, treatment by myringotomy
and insertion of tympanostomy tubes may be
required.

48.  Removal of the tube several weeks before
cochlear implantation will usually result in a
healed, intact tympanic membrane before
planned cochlear implantation.
 When an effusion occurs in an ear with a
previously placed cochlear implant device, no
treatment is required as long as the effusion
remains uninfected.

49. Medical Evaluation
1. Clinical history
2. Preliminary examination
3. Complete medical and neurologic
examination
4. Cochelar imaging using computed
tomography (CT or magnetic resonance
imaging (MRI)

50. 5. Vestibular examination (electronystagmography)
6. Pathology tests
7. Psychologic or psychiatric assessment or both
8. Vision testing
9. Assessment for anaesthetic procedures

51. Contraindications
 Incomplete hearing loss
 Neurofibromatosis II, mental retardation, psychosis,
organic brain dysfunction, unrealistic expectations
 Active middle ear disease(relative)

52.  CT findings of cochlear agenesis (Michel deformity) or small IAC (CN8
atresia)
 Dysplasia not necessarily a contraindication, but informed consent is
a must
 Advanced cochlear otosclerosis

53. Surgical Implantation

54.  The most widely used surgical approach for
cochlear implantation is through the facial
recess or posterior tympanotomy.
 Skin incisions are designed to provide
coverage of the external portion of the
implant package while preserving the blood
supply of the postauricular flap.
 Anterior- or inferior-based flaps are in
common usage.

56. Recess Marking Template
The Recess Marking Template is
used to determine the location of the
recess bed and channel for the
electrode lead.
From Advanced Bionics

58.  The inferior extent of the incision is made
well posterior to the mastoid tip to preserve
branches of the postauricular artery.
 From here the incision is directed
posterosuperiorly and then directed directly
superior without a superior anterior limb.

59.  In children, the incision incorporates the
temporalis muscle to give added thickness.
 A pocket is created for positioning the
implant induction coil.
 Well anterior to the skin incision, the
periosteum is incised from superior to
inferior and a posterior periosteal flap is
developed.

60.  At the completion of the procedure, the
posterior periosteal flap is sutured to the skin
flap, compartmentalizing the induction coil
from the skin incision.

61.  Following the development of the skin
incision, a complete mastoidectomy is
performed.
 The horizontal semicircular canal is identified,
and the short process of the incus is
identified in the fossa incudis.
 The facial recess is exposed using the fossa
incudis as an initial landmark.

62. The facial recess is a triangular area bounded
by
 (1) the fossa incudis superiorly,
 (2) the chorda tympani nerve laterally and
anteriorly, and
 (3) the facial nerve medially and posteriorly.

64.  The facial nerve can usually be visualized
through bone without exposing it completely.
 The round window niche is visualized
through the facial recess approximately 2 mm
inferior to the stapes.

65.  Occasionally, the round window niche is
posteriorly positioned and is not well
visualized through the facial recess or is
obscured by ossification.
 Particularly in these situations it is important
not to be misdirected by hypotympanic air
cells.

66.  Entry into the scale tympani of the cochlea is
best accomplished through a cochleostomy
created anterior and inferior to the annulus of
the round window membrane.

68.  A small fenestra slightly larger than the
electrode to be implanted (usually 0.5 mm) is
developed.
 A small diamond burr is used to "blue line"
the endosteum of the scala tympani, and the
endosteal membrane is removed with small
picks.

70. Electrode Insertion
The insertion tool is used to
insert the electrode array in
the usual fashion.
The Insertion Tube is placed
just inside the cochlea
toward the basal turn of the
scala tympani, with the
insertion tube slot directed
toward the modiolar (or
inner) wall.
From Advanced Bionics

71. Electrode Array Placement
Within the Cochlea
Illustration courtesy of Cochlear
Corporation

73.  This approach bypasses the hook area of the
scala tympani allowing direct insertion of the
active electrode array.
 After insertion of the active electrode array,
the round window area is sealed with small
pieces of fascia.

74. Cochlear abnormalities
 The most common abnormality encountered
is the ossified cochlea most commonly after
meningitis, although other pathologies may
predispose to ossification, including
otosclerosis, chronic otitis media, ototoxicity,
autoimmunity, trauma and others.

75.  The other exception is the case of the
cochlear anomaly or dysplasia, encountered
in approximately 1.5 percent of cases.
 A variety of techniques may be used to help
control the flow of CSF, including firm
plugging of the cochleostomy using soft
tissue coupled possibly with reducing the
flow by lumbar drainage procedures or even
total drainage of CSF.

76. Closure
The skin incision is closed in layers.
From Advanced Bionics

79. Other techniques
• Suprameatal approach
• Veria technique
• Pericanal electrode insertion
• Middle cranial fossa

80. SMA
 Skin incisions as of facial recess approach
 A well is drilled for the ICS package anchor.
 The posterior wall of the external auditory canal (EAC) skin is
incised 5–7.mm lateral to the annulus.
 A six o’clock incision is made on the meatal skin and the tympano-
meatal •
ap is elevated thus entering the middle-ear cavity.

81.  A groove is then drilled posterior to the chorda tympani (the EAC
groove).
 An oblique tunnel is created in the suprameatal region (the suprameatal
tunnel) connecting to the lateral end of the EAC groove.
 In order to avoid njury to the middle fossa dura, drilling is initiated by
careful exploration of the dural position in the suprameatal region.
 Once the middle fossa dura has been localized, an oblique tunnel
extending away from the dura in the infero-medial direction is created.

82.  The cochleostomy is drilled in the
promontory antero-inferior to the
stapes and
 thus an maginary line is created
between the suprameatal tunnel, the
EAC groove, the space underneath the
chorda tympani between the malleal
manubrium and the long process of the
incus, and the cochleostomy.
 The electrode is passed through this
imaginary line into the cochleostomy
 Small pieces of temporalis muscle are
used for sealing the cochleostomy and
fixing the electrode within the EAC
groove and the suprameatal tunnel.

83. • The ICS package is pushed into the posterior pouch and the ball
electrode underneath the temporalis muscle.
 The subperiosteal flap is used to cover the electrode array.
 The tympanomeatal flap is placed back and the surgical wound is
closed.

84. Veria
 endaural approach to the middle ear,
 inspection of the middle ear and facial nerve anatomy by a small
atticotomy if necessary, to rule out any irregularities,
 drilling a direct tunnel, from behind the suprameatal spine to the
facial recess,
 cochleostomy through the endaural approach,

85.  direction: from suprameatal spine to the anterior rim of the round
window,
 depth of drilling: most superficially, preserving only 0.5 mm of
thickness of the cortex,
 width of the tunnel: start with a 2.4-mm cutting burr for the first
half of the distance and finish with a 1.5-mm burr, and
 stop drilling when the chorda tympani is pushed by the burr, or
the middle ear cavity is entered.

86.  extension of the skin incision superoposteriorly, to expose the
temporomastoid region,
 creation of two flaps: a skin lap inferiorly based and a fascial flap
superiorly based,
 drilling the well for the device,
 fixing the device and inserting the active electrode through the
direct tunnel to the middle ear and the cochlea, and
 closing the incision in layers

87. Pericanal elecrode insertion
• begins with a retroauricular skin incision.
• The bony surface of the mastoid plane behind the ear is dissected
free and the skin of the EAC is elevated together with the posterior
part of the tympanic membrane.

88.  A cochleostomy is performed slightly anterior to the round window
using a Skeeter microdrill (1 mm diameter orange-colored cutting drill)
until the tunnel of the scala tympani is opened.
 The superior edge of the drill hole is smoothed.
 Then, using a normal microsurgical 1.6 mm diameter cutting burr and
applying abundant irrigation with water, a vertical groove of 2 mm
diameter is drilled into the postero-superior region of the bony EAC
from immediately above the incus body towards the outer border of the
EAC.


89. • The rim is connected to the retroauricular bony surface by a short superficial tunnel,
also drilled using the cutting burr.
 A bed for the implant is delineated into the retroauricular parietal bone in the usual
place.
 The electronic device of the implant is put in place and fixed anteriorly with drops of
glass ionomer cement The electrode of the implant is gently passed through the
tunnel and through the vertical bone groove into the tympanic cavity below the
chorda tympani between the malleus handle and the long process of the incus and
 then progressively pushed through the cochleostomy hole into the scala tympani.

90.  The cochleostomy opening around the electrode is sealed with tiny
bits of adipose tissue.
 A small amount of glass ionomer cement is used to fix and cover
the electrode and to fill up the bony rim drilled into the EAC.
 The cement is covered with a thin layer of bone dust.
 After placement of the ground electrode between the bone and
temporal muscle, the internal processor is covered by replacing the
muscle and skin flap.

91. Middle fossa approach
• After adequate exposure of middle fossa floor,a triangular bony area
between the GSPN and the projection of the labyrinthine portion of
facial nerve drilled out
• Basal turn of cochlea facing middle cranial fossa identified and
cochleostomy measuring 1.5 mm is made in the most superficial part
• Electrode carrier inserted
• Receiver stimulator positioned on bone well drilled in squamous bone

92. Complications:
A. Intraoperative
1. Intraoperative cannot be placed appropriately.
2. Insertion trauma

93. Complications (cont.):
B. Postoperative
1. Postauricular flap edema, necrosis or separation
2. Facial paralysis
3. Transient vertigo is more likely to occur on a totally non
functioning vestibular system.
4. Pain is usually associated with stimulation of Jacobson’s nerve,
the tympanic branch of the glossopharyngeal nerve.
5.Facial nerve stimulation
6. Meningitis

94. After the surgery
•Initial stimulation: 4-6
weeks post surgery
•Adjustments made
regularly based on
feedback from patients,
parents, therapists and
educators
•Rehabilitation to meet
specific patient needs
•Regular follow-up
appointments

95. Rehabilitation

96. For children
 After the initial 3 month period,
children are usually seen every 3
months for the first year and
 every 6 months for the second
and third years.
 Thereafter, they are seen annually.

97.  weekly adjustments and communication therapy for the first
month.
 treatment focuses on auditory training, speech reading,
music,telephone use & communication strategies

98. Clinical Results - Adults
 A substantial percentage of postlingually deaf
adults demonstrate some open-set speech
recognition (that is, understanding words or
sentences without a multiple-choice answer
format and without lipreading) with a
multichannel cochlear implant.
 Approximately 25% to 50% of the patients
with multichannel implants can understand
speech to varying degrees on the telephone.

99.  With few exceptions, patients demonstrate
better perception and recognition of
environmental sounds and lip-reading
performance with a multichannel cochlear
implant.

100. Children
 An important difference between the
performance of adults and children with
multichannel implants is the long time course
over which learning takes place in the
pediatric population.

101.  Two other findings with children also are
noteworthy.
 First, improvement in speech perception
skills may not be obvious until the devices
have been used for 1 year or more.
 Second, children with the multichannel
implant achieve significantly higher scores on
nearly every type of speech perception test
than do children who use a single-channel
cochlear implant.

102. Speech production skills
 Although the primary role of a cochlear
implant is that of an aid to speech perception,
a secondary and vital role is that of an aid to
speech production.

103.  A longitudinal study of speech development
in children with implants suggests that these
children acquired consonant and vowel
features that are difficult for children with
profound hearing losses to produce (that is,
high vowels, diphthongs, alveolar consonants,
and fricatives)

104.  Children who are implanted in early
childhood generally show large improvements
in speech in contrast to children who were
not implanted until adolescence (Osberger et
al, 1992).

105.  All the studies point to the duration of
deafness prior to implantation being a
significant predictor of performance (with
performance deteriorating as this duration
increases).

106.  These findings do not mean that
children who are adolescents
should not receive an implant.
 Rather the child and family should
be counseled carefully regarding
realistic expectations in
performance with the implant.

107. Physician's role in counseling families
regarding cochlear implants
Three important areas to be covered with
families are
1) benefits, limitations, and risks of the
cochlear implant;
2) realistic expectations for a given patient;
3) long-term prospects for the implant,
including device failure and device upgrade.

108.  Families, with limited access to accurate
information about the implant, may have
incorrect notions regarding the device.
 These notions often include the assumption
that the device is completely implantable,
with no external hardware; a belief that the
implant is appropriate for hard-of-hearing
individuals, or those with unilateral hearing
loss; and an assumption that the implant
restores normal hearing to deaf patients.

109.  In addition to mentioning possible surgical
complications, patients should be made
aware that any residual hearing in the ear to
be implanted will most likely be destroyed as
a result of electrode insertion, thereby
prohibiting future use of a hearing aid in that
ear.

110. Long-term prospects for
implant
 Patients should be counseled regarding the
long-term maintenance of the implant,
including the cost of parts and repairs and
the possibility of device failure that could
necessitate additional surgery.
 Families frequently inquire about the
potential for upgrading the device to make
use of future improvements in electrode
design or speech processing schemes.