definition of cochlear implant , history of the procedure , purpose of the procedure , indications for cochlear implant , surgical procedure , risk of cochlear implant surgery , post operative care , normal result

1. Implant Surgery
Dr , Ibrahim habib barakat , M.D.

2. overview
Definition
Purpose
History
Hardware
Description
Indications
Surgical Procedure
Normal results
Risks

3. Definition
A cochlear implant is a small, complex
electronic device used to treat
severe to profound hearing loss.
It is surgically implanted underneath
the skin behind the patient's ear.

4. purpose
A cochlear implant bypass nonfunctional parts
of the ear and directly stimulating the
auditory nerve.
It does not merely amplify sound.
It increases the amount of nervous response to
sound.
It often improves sound detection and
increases speech understanding.

5. history
Between 1965 and 1970, Dr. House teamed up
with Jack Urban, an innovative engineer, to
ultimately make cochlear implants a clinical
reality
The new devices consisted of a single electrode
and benefited from microcircuit fabrication
derived from space exploration and
computer development

6. history
Between 1965 and 1970, Dr. House teamed up
with Jack Urban, an innovative engineer, to
ultimately make cochlear implants a clinical
reality
The new devices consisted of a single electrode
and benefited from microcircuit fabrication
derived from space exploration and
computer development

7. The House 3M Single-Electrode
Implant
In 1972, a speech processor was developed to
interface with the single-electrode implant and it
was the first to be commercially marketed as the
House/ 3M cochlear implant
More than 1,000 of these devices were implanted
between 1972 to the mid 1980s
In 1980, the age criteria for use of this device was
lowered from 18 to 2 years and several hundred
children were subsequently implanted

8. Multi-Channel Implants
During the late 70s, work was also being done
in Australia, where Clark and colleagues were
developing a multi-channel cochlear implant
later to be known as the Cochlear Nucleus
Freedom
Multiple channel devices were introduced in
1984, and enhanced the spectral perception
and speech recognition capabilities
compared to House’s single-channel device

9. Cochlear Nucleus Freedom

10. Cochlear Nucleus Freedom

11. Advanced Bionics Hi-Res 90K

12. Advanced Bionics Hi-Res 90K

13. Description
Normal hearing , sound vibrates the eardrum.
The vibration is carried through the middle ear
and the cochlea.
Movement in the cochlear fluid is transferred to
hair fibers within the cochlea.
The movement of these hair cells stimulates
ganglion cells that send an electrical current to
the auditory nerve.
The nerve carries the current to the brain, where
the electrical stimulation is recognized as sound.

19. description
Damage to the hair cells within the
cochlea (sensorineural deafness ), can
often be treated with cochlear implants
, if damage to the hair cells is not
accompanied by damage to the auditory
nerve itself.

21. description
Cochlear implants consist of internal and
external parts.
The external parts include a microphone, a
speech processor, and a transmitter.
The internal parts include a receiver-stimulator
and an electrode..

23. The various components are :
1. The electrode array (which is placed in the
inner ear).
2. The receiver for the electrode array.
3. The speech processor, a small electronics
package that typically is placed in the
wearer's pocket.
4. Transmitting coil and
5. Microphone, both of which are worn behind
the ear.

26. description
Within the headpiece, the microphone picks up
sound in the environment.
The speech processor converts these sounds into a
digital signal.
The content of the generated digital signal is
determined by the programming of the
processor and is complex.
The transmitter converts the digital signals into
FM radio signals and sends them through the
skin to the internal parts of the implant.

29. description
The internal parts are those that are
surgically implanted into the patient.
The receiver-stimulator is disk-shaped
and is about the size of a quarter.
It receives the digital signals from the
transmitter and converts them into
electrical signals..

32. description
A wire connects the receiver to a group of
electrodes that are threaded into the cochlea
when the implant is placed.
As many as 24 electrodes, depending on the
type of the implant, stimulate the ganglion
cells in the cochlea.
These cells transmit the signals to the brain
through the auditory nerve. The brain then
interprets the signals as sound.

35. description
The sounds heard through an implant artificial
or robot-like.
This is because the implant's electrodes cannot
match a person's 15,000 hair cells.
However, as more electrodes are added, and
the software for the implant speech are
moving closer to how speech and other
sounds are naturally perceived.

36. indications
For children who can
respond reliably,
standard pure-tone and
speech audiometry
tests are used to screen
likely candidates.
Otherwise, ABR and OAEs
can be used to detect
very young children
with severe-to-
profound hearing loss

37. indications
For children aged 12-23
months, the pure-
tone average (PTA) for
both ears should
equal or exceed 90
dB.
For individuals older
than 24 months, the
PTA for both ears
should equal or
exceed 70 dB.

38. indications
Older children are then evaluated with speech-
recognition tests with best-fit hearing aids in place
in a sound field of 55-dB
One of the most common speech-recognition tests is
the hearing in noise test (HINT), which tests speech
recognition in the context of sentences (open set
sentences)
Current guidelines permit implantation in children
whose recognition is <60%

39. Meningitis and labyrinthitis
ossificans
12 months is the current age limit the FDA has
established for implantation
However, a child with deafness due to
meningitis may develop labyrinthitis
ossificans, filling the labyrinth with bone
In these cases, special techniques may be
needed for implantation and suboptimal
outcome may result

40. Meningitis and labyrinthitis
ossificans

41. Meningitis and labyrinthitis
ossificans
Using serial imaging, implant teams may monitor
patients with new deafness due to meningitis and
perform implantation at the first sign of
replacement of the scala tympani with fibrous
tissue or bone
Otherwise, implantation in patients with
postmeningitic deafness is usually recommended
after 6 months to allow for possible recovery of
hearing

42. Cochlear Abnormalities
Preoperative CT scan should always be
performed, to detect cochlear abnormalities
or absence of CN VIII
Cochlear malformations, though, do not
necessarily preclude implantation
In pediatric patients with progressive hearing
loss, neurofibromatosis II and acoustic
neuromas should be excluded by performing
MRI

43. Cochlear Abnormalities

44. procedure
The future site of the implant reciever is marked with
methylene blue in a hypodermic needle
This site at least 4 cm posterosuperior to the EAC,
leaving room for a behind-the-ear controller
Next, a postauricular incision is made and carried
down to the level of the temporalis fascia superiorly
and to the level of the mastoid periosteum
inferiorly
Anterior and posterior supraperiosteal flaps are then
developed in this plane

49. procedure
Next, an anteriorly based periosteal flap,
including temporalis fascia is raised, until the
spine of Henle is identified.
Next, a superior subperiosteal pocket is
undermined to accept the implant transducer
Using a mock-up of the transducer, the size of
the subperiosteal superior pocket is checked

51. procedure
Next, using a 6 mm cutting burr, a cortical
mastoidectomy is drilled
It is not necessary to completely blueline the
sinodural angle, and doing so may interfere
with proper placement of the implant
transducer

54. procedure
Using a mock-up of the transducer for sizing, a well is
drilled into the outer cortex of the parietal bone to
accept the transducer magnet housing
Small holes are drilled at the periphery of the well to
allow stay sutures to pass through.
These suture will be used to secure down the implant
Stay sutures are then passed through the holes

56. procedure
Using the incus as a depth level, the facial
recess is then drilled out
Through the facial recess, the round window
niche should be visualized
Using a 1 mm diamond burr, a cochleostomy is
made just anterior to the round window
niche

57. procedure
The transducer is then laid into the well and
secured with the stay sutures
The electrode array is then inserted into the
cochleostomy and the accompanying
guidewire is removed

67. procedure
Small pieces of harvested periosteum are
packed in the cochleostomy around the
electrode array, sealing the hole
Fibrin glue is then used to help secure the
electrode array in place
The wound is then closed in layered fashion
and a standard mastoid dressing is applied

72. Aftercare
For a short period of time after the surgery, a special bandage
is worn on the head during sleep.
After about one month, the surgical wounds are healed and
the patient returns to the implant clinic to be fitted with
the external parts of the device and to have the device
turned on and mapped.
Mapping involves fine tuning the speech processor and setting
levels of stimulation for each electrode, from soft to loud.
The patient is then trained in how to interpret the sounds
heard through the device.
The length of the training varies from days to years,
depending on how well the person can interpret the sounds
heard through the device.

80. Normal results
Most profoundly deaf patients who receive an
implant are able to discern medium and loud
sounds, including speech, at comfortable
listening levels.
Many use sound clues from the implant,
together with speech reading and other facial
cues, to achieve understanding.

81. Normal results
Almost all adults improve their communication skills
when combining the implant with speech reading
(lip reading), and some can understand spoken
words without speech reading. More than half of
adults who lost hearing after they learned to speak
can understand some speech without speech
reading. Especially with the use of accessory
devices, the great majority can utilize the telephone
with their implants.

84. Risks
As with all operations, there are risks with this
surgery. These include:
infection at the incision site
bleeding
complications related to anesthesia
transient dizziness
facial paralysis (rarely)
temporary taste disturbances
additional hearing loss
device failure

85. Risks
However, it should be noted that serious
surgical complications have been observed at
only one in 10,000 procedures of this type.
Some long-term risks of the implant include the
unknown effects of electrical stimulation on
the nervous system.
It is also possible to damage the implant's
internal components by a blow to the head,
which will render the device unworkable.

86. Risks
A further consideration is that the use of magnetic
resonance imaging (MRI) for patients with cochlear
implants is not recommended because of the magnets
present in the devices.
Several companies have developed implants that do not use
magnets or have altered the receiver-stimulator make up
to make it easier to remove the magnets before testing.
One fact that reduces the concern about MRI testing is that
for many medical indications, MRI can be replaced with a
computer assisted tomography scan (CAT or CT scan),
which is not a problem for persons with cochlear
implants.

87. Risks
Additionally, in July 2002, the Food and Drug
Administration (FDA) issued a warning about a
possible connection between increased incidence of
meningitis and the presence of a cochlear implant.
This warning included special vaccine recommendations
for those with implants, as well as the voluntary
removal from the market of certain devices.
Specifically, those implants that included a positioner
to hold the electrodes in place in the cochlea appear
to be associated with an increased risk of the disease.