Electro Acoustic Stimulation ( EAS )

1. ELECTRO ACOUSTIC STIMULATION
- Dr. Satya Kiran Avvaru

2. EAS

3. Nomenclature

4. Introduction
Expanding criteria of CI
Why cant hearing aids be used ?
Problem of high freq HL
Concept of preservation (? residual
hearing) in CI

5. 1. residual hair cells
2. neural tissues
3. endocochlear potentials
4. the travelling wave
5. inner ear & middle ear transformer mech.
6. vestibular system
What is to be preserved?

6. Hearing preservation
- post op PTA (250,500,750,1000 Hz) within 10dB of pre op PTA
- post op PTA (250,500,1000,2000 Hz) within 10dB of pre op PTA
% of HP = [PTA post op – PTA pre op ] / [120 – PTA pre op] X 100

7. - Standard CI technique – residual hearing is lost in
50% of recipients
- Hearing conservation – increasingly realistic &
desired goal in CI surgery
- Lesser traumatic insertion achieved in several ways..

8. Hearing preservation - Devices
Manufacturer Electrode Electrode length HP principle Route &
Degree of
insertion
Cochlear Hybrid S 8
Hybrid S 12
6 mm (0.2-0.4 dia, 6 ch)
10 mm
10 mm (10 ch)
Short electrode Cochleostomy
(190200)
Cochleostomy
Cochlear Hybrid L 24 16 mm (22 ch) Short electrode Cochleostomy
RW (270)
Cochlear CI 422 Slim 25 mm (0.3-0.6 mm dia,
22 + 2 el)
Thin electrode
(straight, lateral wall
electrode)
Cochleostomy
RW(270450 )
Med El FLEX EAS 2124 mm (19 el = 7
pairs + 5)
Shorter, thin
electrode
Cochleostomy
RW (CCC)
Advanced
Bionics
Mid scala 18.5 mm Shorter, thin
( mid scala)
RW
Cochleostomy

9. Hearing preservation techniques
• Optimal electrode length
controversy
• Partially inserted standard
electrodes
• Softer & thinner electrodes
• Preservation with full insertion of
standard electrode
• Optimal insertion depth angle
• Minimized forces on outer
cochlear wall
• Minimized drilling
Methods
Alternate
methods

10. “Soft surgery” features
- identify RW membrane
- site, size & seal of cochleostomy
- elimination of bone dust & blood (? lubricant)
- low speed drilling while cochleostomy
- no suctioning of perilymph
- perioperative steroids
- careful insertion of electrode array
- ? cochleostomy / RW / Extended or peri RW technique

11. What is EAS ?
EAS – a combination of 2 technologies :
cochlear implant for high frequencies
acoustic amplification for low frequencies
Together, they cover full range of hearing for children & adults.

12. Electric + Acoustic stimulation
= CI (i) + HA (c)
= CI (i) + HA (i) + HA (c)
Effects :
1. Improved SDS
2. Improved SNR
3. Music appreciation
Bimodal hearing
Combined hearing

13. Restoring the hearing potential
EAS – can help to regain hearing in
both high and low frequencies
electric stimulation improve
hearing in high-frequency
acoustic amplification can
improve your residual hearing in the
low frequencies

14. HA Vs EAS
monosyllable speech score
test.
HA users score – 21%
EAS users score – 71%
an average of 50% points higher in speech
understanding & sound quality

15. EAS Vs Electric only stimulation
EAS benefits :
- in music with pitch discrimination
- interval perception
- song recognition
- in overall quality of life

16. Audio processor
3rd
generation AP
acoustic unit & customized ear mould
acoustic stimulation across low freq
electric stimulation in high freq
with 48dB acoustic amplification
across low freq
the ideal solution for candidates
with partial deafness
SONNET EAS
MED EL

17. Internal implant
is the ideal choice for EAS
soft, flexible (FLEX EAS)
electrodes to help preserve your
residual natural hearing
MRI Safe at 3.0 Tesla - Without Magnet
removalSYNCHRONY
MED EL

18. Synchrony features
Unparalleled MRI Safety Smallest Titanium Implant
Proven Stability Choice for Any Cochlea

19. FREEDOM HYBRID
is the ideal choice for EAS
shorter electrode avoids
potential for trauma to apical
end of cochlea
HYBRID
COCHLEAR

20. Hybrid L 24
peri-scalar electrode

21. How to select EAS device?

22. How to select EAS device?
Do off an ASSR ; Radio imaging
Anticipate the insertion depth
angle required
Select the most suitable electrode

23. Accessories
Wired accessories
• Audio cable
• TV / Hi-Fi cable
• Ear phones
• Lapel microphone
• FM cable
Wireless accessories
• Mic lock
Hybrid acoustic component

24. Activation
b/w 2-6 wk post implantation
both electric stimulation & acoustic
amplification are activated
initial period of adaptation to combined
stimulation is common as expected.
When ?
What ?
Why ?

25. How safe ?
- FDA approved the Cochlear Nucleus Hybrid L24
Cochlear Implant System for commercial release
- on 21 March, 2014

26. Pitfalls
o Patient related inability to take the advantage of
combined stimulus
o Lack of long term results
o Need for revision implants

27.  In children (1-2 yr) – use of u/l short electrode in
situations tested
 Unilateral deafness + intractable debilitating
tinnitus
 SSD
 Electrode Vs hearing threshold

28. • EAS – benefit of improved SD, hearing in noise, music
appreciation
• Residual hearing preservation – desirable & achievable
• Aspects of electrode design & surgical technique
• Ongoing investigations of strategies & programming post
implantation

29. References
- Cochlear implants 3rd
edition – Susan B. Waltzman
- Peter Luke Santa Maria, Michael Brian Gluth, Yongqing Yuan, et al. Hearing preservation
surgery for cochlear implantation: A Meta-analysis. Otology & Neurotology 2014; 35:e256-
e269.
- Nneka Eze, Dan Jiang, Alec Fitzgerald O’Connor. Inner ear energy exposure while drilling a
cochleostomy. Acta Oto-Laryngologica 2014; 134: 1109-1113.
- Ling Zhou, MD; David R. Friedmann, MD; Claudiu Treaba, Meng, MBA et al. Does
cochleostomy location influence electrode trajectory and intracochlear trauma? The
Laryngoscope 2014.
- www.medel.com
- www.cochlear.com
- Talks @ ISOCON 2014, Chennai
- Talks @ CIGICON 2014, AIIMS, New Delhi

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31. - Dr. SATYA KIRAN