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Welcome you all
BY:lokendra yadav
Cochlear implant A
REVOLUTION IN
The world of implant & hearing
cochlear
WHAT IS cochlear implant?
?
Volta: 18th century
Djourno and Eyries: 1950 & 1957(head)
House, Doyle, Simmons(six channel implant)
1972 Single-channel implant
1984 FDA approval
1990’s
Beyond
A cochlear implant is an electronic device that allows many people with hearing loss to hear better. Unlike hearing aids, which amplify sound, cochlear implants bypass the damaged inner ear and send sound directly to the brain. Many recipients can reconnect with loved ones, contribute their talents at work, and chat comfortably in restaurants.
Cochlear implant Cochlear implant
Medical
Approach
Engg.
Approach
Engineering
approach
Components of Cochlear Implant
Single vs. Multiple channels Audio example of how a cochlear implant sounds with
varying number of channels
Monopolar vs. Bipolar
Speech processing strategies Spectral peak (Nucleus)
Continuous interleaved sampling (Med-El, Nucleus, Clarion)
Advanced combined encoder (Nucleus)
Simultaneous analog strategy (Clarion)
Firing rate responses (color
coded) evoked by various
cochlear-implant stimuli in the
auditory cortex (guinea pig).
Vertical axis = cortical place
• top = caudo-medial
• bottom = rostro-lateral
Horizontal axis = time relative
to stimulus onset
Blue Yellow Red
Low FR high FR
(where “FR” = firing rate in
action potentials/second)
= FR weighted centroid of
activity
Monopolar electrode
Bipolar electrode
Tripolar electrode
Basal coochlea
High frequencies
Apical cochlea
Low frequencies
Cochlear stimulation
Strategy Signal Representation
Stimulation Channels Rate per channel
Device
CA Bandpassed Waveforms
Analog 4 Continuous Waveform
Ineraid
CA Bandpassed Waveforms
Analog 8 13,000 samples/sec
Clarion1.0
CIS Envelope signals Pulsatile 8 833 pps Clarion1.0
CIS Envelope signals Pulsatile 8 1,515 pps Med-El
F0/F2 Second formant, Voicing features
Pulsatile 1 F0 or random rate
Nucleus
F0/F1/F2 First and second formant, Voicing features
Pulsatile 2 F0 or random rate
Nucleus
Simulation of cochlear implant……….
Cochlear-implant simulation
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-6
-4
-2
0
2
4
6
8Waveform of Original Sound
Time (sec)
Am
plit
ud
e
TextEnd
Time
Fre
qu
en
cy
TextEnd
Spectrogram of Original Sound
0 0.5 1 1.5 2 2.5 3 3.5 4 4.50
2000
4000
6000
8000
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5-1
-0.5
0
0.5
1
1.5
2x 10
4 Simulated waveform
Time (sec)
Am
plit
ud
e
TextEnd
Time
Fre
qu
en
cy
TextEnd
Spectrogram of simulated waveform
0 0.5 1 1.5 2 2.5 3 3.5 4 4.50
2000
4000
6000
8000
From Lokendra:_maulana azad medical college
best 6 of 16 channels, 250 Hz pulserate, 16 kHz sampling H/U filterbank
General specification of cochlear implant device:
Length of electrode array:25mm 2 Gnd electrode No of channels: 20 Electrode impedence:2K
General features
Surgical features
Electrode array features
Stimulation features
MEDICAL
APPROACH
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
R
C.I.
Pre surgical requirement:
Check the impedance of ear it should not be more
CT findings
Check BP
No anatomical disorders in ear
No psychological complain history
Surgical steps:
Step 1: provide anesthesia to patient before 10 min (subjected)
Step 2 : marking of area where incision would be given by methyl blue
Step3: surgeon should initiate the process mastoidtomy, posterior
tympanotomy by giving surface incision(temporal fasica graft) by using
surgical blade or electric cut.
Now temporal bone dissection : use drill bit of 1mm at 18000 to 20000 rpm not
above .some time 3mm drill bit is also used.
Facial nerve preservation is crucial part of the surgery
1st Landmark incus
stapes
Incision in round
window
insertion of electrode
Cochlear receiver setting
Bed arrangement
Screw arrangement
Complication rate only 5%
Wound infection/breakdown Yu, et al showed good response to Abx, I&D
Facial nerve injury/stimulation, CSF leak, Meningitis CDC recommendations
Vertigo (Steenerson reported 75%)
Device failure—re-implantation usually successful
Avoid MRI
Necessary part of implantation
Different focus depends on patient’s previous experience with sound
Goal is to enable children to be able to learn passively from the environment
Program addresses receptive as well as expressive language skills
Multidisciplinary, dedicated group necessary
Partial implants with hearing aid Those with residual low-frequency hearing
Intraoperative mapping
Bilateral implantation One vs. two speech processors
Implantation for asymmetric SNHL
“Softip” array
Minimally invasive implantation