Download - Electro Acoustic Stimulation ( EAS )
ELECTRO ACOUSTIC STIMULATION
- Dr. Satya Kiran Avvaru
EAS
Nomenclature
IntroductionExpanding criteria of CI
Why cant hearing aids be used ?
Problem of high freq HL
Concept of preservation (? residual
hearing) in CI
1. residual hair cells2. neural tissues3. endocochlear potentials4. the travelling wave5. inner ear & middle ear transformer mech.6. vestibular system
What is to be preserved?
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
- 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..
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(190200)Cochleostomy
Cochlear Hybrid L 24 16 mm (22 ch) Short electrode CochleostomyRW (270)
Cochlear CI 422 Slim 25 mm (0.3-0.6 mm dia, 22 + 2 el)
Thin electrode(straight, lateral wall
electrode)
CochleostomyRW(270450 )
Med El FLEX EAS 2124 mm (19 el = 7 pairs + 5)
Shorter, thin electrode
Cochleostomy RW (CCC)
Advanced Bionics
Mid scala 18.5 mm Shorter, thin( mid scala)
RWCochleostomy
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
MethodsAlternate methods
“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
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.
Electric + Acoustic stimulation
= CI (i) + HA (c)
= CI (i) + HA (i) + HA (c)
Effects :
1. Improved SDS
2. Improved SNR
3. Music appreciation
Bimodal hearingCombined hearing
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
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
EAS Vs Electric only stimulation
EAS benefits :
- in music with pitch discrimination
- interval perception
- song recognition
- in overall quality of life
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 EASMED EL
Internal implantis 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
Synchrony features
Unparalleled MRI Safety Smallest Titanium Implant
Proven Stability Choice for Any Cochlea
FREEDOM HYBRIDis the ideal choice for EAS
shorter electrode avoids potential for trauma to apical end of cochlea
HYBRIDCOCHLEAR
Hybrid L 24 peri-scalar electrode
How to select EAS device?
How to select EAS device?
Do off an ASSR ; Radio imaging
Anticipate the insertion depth angle required
Select the most suitable electrode
AccessoriesWired accessories
• Audio cable
• TV / Hi-Fi cable
• Ear phones
• Lapel microphone
• FM cable
Wireless accessories
• Mic lock
Hybrid acoustic component
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 ?
How safe ?- FDA approved the Cochlear Nucleus Hybrid L24
Cochlear Implant System for commercial release
- on 21 March, 2014
Pitfalls
o Patient related inability to take the advantage of combined stimulus
o Lack of long term results
o Need for revision implants
In children (1-2 yr) – use of u/l short electrode in situations tested
Unilateral deafness + intractable debilitating tinnitus
SSD
Electrode Vs hearing threshold
• 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
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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- Dr. SATYA KIRAN