cochlear implant

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