Electric acoustic stimulation (EAS) combines acoustic hearing preservation with electric stimulation from a cochlear implant. EAS aims to preserve residual low-frequency hearing while providing stimulation for high frequencies not heard. The history of cochlear implants led to the development of EAS. EAS surgery techniques aim to insert the electrode array atraumatically to avoid hearing loss. Outcomes of EAS include successful hearing preservation in 75% of subjects long-term and significantly improved speech perception compared to acoustic hearing alone. EAS also provides benefits for music appreciation and subjective hearing benefits.

1. Electric Acoustic Stimulation
and Hearing Preservation :
Atraumatic Surgical
Techniques and Outcome
Dr Zeeshan Ahmad Department of ENT,
M.S.(ENT,PGY1) NMCH,Patna.
18-10-2012

2. Cochlear Implant History
#Pre-1960’s
- beginning studies of
electrical stimulation
on humans
#1960’s
- active research of
electrical stimulation in
human ears
#1970’s
- first wearable
implants designed for
long-term stimulation
#1980’s
- commercial
development of the
cochlear implant
device began

3. #1985
…continued
- United States Food &
Drug Administration
(FDA) granted the first
approval for implantation
in adults
#1990
- FDA granted approval
for cochlear implants in
children
#1999
- Electric Acoustic stimulation
first described by C. Von
Ilberg & J Kiefer of
Frankfurt University. Same
year first EAS implant
was done.

4. Something
beyond
“JUST
COCHLEAR
IMPLANT”

5. From CI to EAS : Basis
Feasibility to preserve
preoperative low frequency
hearing when performing CI
in the Scala Tympani(ST)
gave rise to the concept of
ELECTRIC ACOUSTIC
STIMULATION.

8. An EAS
System
(External
components)

9. ELECTRIC STIMULATION:
 A cochlear implant converts everyday
sounds into coded electrical pulses.
These pulses stimulate the auditory
nerve. The brain interprets these
signals as sound.
 Mid and high frequency sounds are
picked up by the microphone of
theDUET 2 Audio Processor and are
converted into a special code.

10. ELECTRIC
STIMULATION:
 This code is sent to the coil and is
transmitted across the skin.
 The implant interprets the code and
sends electrical pulses to the electrodes
in the cochlea.
 The auditory nerve relays these signals
to the brain

11. ACOUSTIC STIMULATION:
 Acoustic amplification turns up the
volume on the sounds that the cochlea
is still able to hear. For EAS, only the
low frequencies are amplified.
 Low frequency sounds are picked up
by the microphone and are digitally
processed.
 Sounds are amplified by the
loudspeaker located in the ear hook
and are relayed via the ear mould to
the ear canal.

12. ACOUSTIC STIMULATION:
 Sounds reach the undamaged areas of
the cochlea responsible for processing
low-frequency sound.
 The auditory nerve sends the signals to
the brain.

13. The importance of high
frequency hearing
 Our brain relies extensively on high
frequency sounds to clearly decipher and
understand spoken words, especially at a
distance or in noisy places.
 High frequencies deliver the additional vital
details of sound – making the sounds you
hear richer, fuller and crisper in every way.
 Hearing high frequency sounds clearly can
enrich your awareness and enhance your
experience.

14. High frequency hearing loss
 Did you know that many words begin and
end with high frequency sounds?
 That explains why, when you lose high
frequency hearing, words seem to merge
together and become indistinguishable
from one to the next.
 In addition to human speech, your
environment is full of many other high
frequency sounds, without which you
can’t get a complete sense of a situation.

15. Let’s see a typical audiogram
for an individual with high
frequency hearing loss.
Someone with severe to profound high
The red line shows a person's hearing
frequency hearing loss would strugglethe
of to
The closer the line is to the bottom hear at
profile - how much sound they can
hear the sounds above the hearing loss.
audiogram, the greater red line
different frequencies.
(speech, birdsong, music, telephone

16. Indications and Criteria for
EAS
(a)Audiological criteria
◦ below 1.5 kHz – No or moderate HL
◦ above 1.5 kHz – Severe to profound SNHL

17. Indications and Criteria for
EAS
(b)Speech recognition
• The patient's monosyllable word score
should be ≤ 60% at 65dB SPL in the
best aided condition.

18. Indications and Criteria for
EAS
(c)Additional criteria
 No progressive hearing loss(10/2, 15/1 in
1yr)
 No autoimmune inner-ear disease
 No hearing loss as a result of
meningitis, otosclerosis or ossification
 No malformation or obstruction of the
cochlea
 Maximum air–bone gap 15dB HL
 No external ear contraindications to

19. SURGERY :-
The EAS surgeries are aimed at
preserving the anatomical structures and
preserving the cochlear function. Steps
are as follows:-
 Pre-incision measures
◦ Antibiotic prophylaxis
◦ Systemic corticosteroids
 Posterior tympanotomy
◦ A standard mastoidectomy is done
◦ Anatomy identified

20. SURGERY :-
 Endosteum or Round Window
exposure at the Cochleostomy site
◦ Currently, RW approach is mostly used
 Topical steroid application
◦ Dexamethasone 1mg/ml or Triamcinolone
40 mg/ml
◦ Allowed for minimum 30 minutes

21. SURGERY :-
 Placing the Implant
◦ Subperiosteal pocket created
◦ Well for Implant created
◦ Bone dust and blood removed
◦ New gloves
◦ Subcutaneous fat autografts taken
◦ Implant inserted into the implant well
◦ Electrode array is coated with Hyaluronic
acid and Steroid

23. SURGERY :-
 Inserting the Electrode Array
◦ Electrode tip is placed in the opening(RW or
Cochleostomy) and introduced into the Scala
Tympani supero-posterior to antero-inferior
◦ Slowly to prevent intracochlear pressure
build-up
◦ Inserion is stopped when predefined length
is reached or resistance is felt
◦ tip touching the ST Modiolar wall avoided
◦ Opening closed with previously taken
antibiotic soaked Fat Autografts.

24. SURGERY :-
 Securing the Electrode and Closing the
Retroauricular Incision in Three Layers
◦ Care is taken that Ossicular Chain is not
touching with any component

25. Electrode design for HP
 For hearing preservation the
Electrodes are designed to create least
trauma to intracochlear structures
◦ Thinner caliber 0.25mm at tip and 0.8mm
at entry site
◦ More flexible Tip regions
◦ Tailoring the insertion depth

27. Outcome of EAS
 HEARING PRESERVATION
◦ The success of EAS Implant depends upon
the RLFH(Residual Low Frequency
Hearing).
◦ The cochlear hybrid implant using 6mm and
10mm elctrodes resulted in long term
hearing preservation in 75% of subjects.
◦ Studies using Med-El elctrodes showed a
successful HP in 12/18 subjects with
complete hearing loss in 3/18 subjects.

28. Outcome of EAS
 SPEECH PERCEPTION with EAS
◦ EAS significantly improves speech
perception in quiet and in noise compared to
acoustic hearing only.
◦ In a study by Gstoettner et al EAS treatment
yielded an improvement in speech
perception in quiet from 24% preoperatively
to 71% after 12 months.

29. Outcome of EAS
 Music appreciation and Subjective
benefit with EAS
◦ EAS users perform better on melody and
instrument recognition than CI users.
◦ Subjective benefit of EAS was assessed
with APHAB(Abbreviated Profile of Hearing Aid
Benefit).
◦ Observed with EAS fitting and improved
gradually with experience.

30. THANK
YOU
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