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