Active Middle Ear Implants (Advances in Oto-Rhino-Laryngology, Vol. 69)

Active Middle Ear Implants

Advances in Oto-Rhino-Laryngology Vol. 69

Series Editor

W. Arnold Munich

Active Middle Ear Implants Volume Editor

Klaus Böheim

St. Pölten

25 figures, 4 in color, and 1 table, 2010

Basel • Freiburg • Paris • London • New York • Bangalore Bangkok • Shanghai • Singapore • Tokyo • Sydney

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Klaus Böheim Department of Otorhinolaryngology Head and Neck Surgery Landesklinikum St. Pölten Propst Führerstrasse 4 3100 St. Pölten (Austria)

Library of Congress Cataloging-in-Publication Data Active middle ear implants / volume editor, Klaus Böheim. p. ; cm. -- (Advances in oto-rhino-laryngology, ISSN 0065-3071 ; v. 69) Includes bibliographical references and indexes. ISBN 978-3-8055-9470-7 (hard cover : alk. paper) -- ISBN 978-3-8055-9471-4 (e-ISBN) 1. Hearing aids. 2. Implants, Artificial. 3. Middle ear--Surgery. I. Böheim, Klaus. II. Series: Advances in oto-rhino-laryngology, v. 69. 0065-3071 ; [DNLM: 1. Ossicular Prosthesis. 2. Hearing Loss--surgery. 3. Ossicular Replacement. W1 AD701 v.69 2010 / WV 230 A188 2010] RF305.A28 2010 617.8’9--dc22 2010017165

Bibliographic Indices. This publication is listed in bibliographic services, including Current Contents쏐. Disclaimer. The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publisher and the editor(s). The appearance of advertisements in the book is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements. Drug Dosage. The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any change in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. © Copyright 2010 by S. Karger AG, P.O. Box, CH–4009 Basel (Switzerland) www.karger.com Printed in Switzerland on acid-free and non-aging paper (ISO 9706) by Reinhardt Druck, Basel ISSN 0065–3071 ISBN 978–3–8055–9470–7 e-ISBN 978–3–8055–9471–4

Contents

VII 1

Preface Böheim, K. (St. Pölten) The Vibrant Soundbridge: Design and Development Ball, G.R. (Innsbruck)

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Cost-Effectiveness of Implantable Middle Ear Hearing Devices Snik, A.; Verhaegen, V.; Mulder, J.; Cremers, C. (Nijmegen)

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Indications and Candidacy for Active Middle Ear Implants Wagner, F.; Todt, I.; Wagner, J.; Ernst, A. (Berlin)

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Clinical Results with an Active Middle Ear Implant in the Oval Window Hüttenbrink, K.B.; Beutner, D. (Cologne); Zahnert, T. (Dresden)

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Experiments on the Coupling of an Active Middle Ear Implant to the Stapes Footplate Zahnert, T.; Bornitz, M. (Dresden); Hüttenbrink, K.B. (Cologne)

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The Vibrant Soundbridge for Conductive and Mixed Hearing Losses: European Multicenter Study Results Baumgartner, W.-D. (Wien); Böheim, K. (St. Pölten); Hagen, R.; Müller, J. (Würzburg); Lenarz, T. (Hannover); Reiss, S. (Wien); Schlögel, M. (St. Pölten); Mlynski, R. (Würzburg); Mojallal, H. (Hannover); Colletti, V. ( Verona); Opie, J. (Innsbruck)

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Clinical Experience with the Active Middle Ear Implant Vibrant Soundbridge in Sensorineural Hearing Loss Pok, S.M.; Schlögel, M.; Böheim, K. (St. Pölten)

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The Esteem System: A Totally Implantable Hearing Device Maurer, J.; Savvas, E. (Koblenz)

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Totally Implantable Active Middle Ear Implants: Ten Years’ Experience at the University of Tübingen Zenner, H.P.; Rodriguez Jorge, J. (Tübingen)

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Author Index Subject Index

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Preface

I would like to sincerely thank the editor of Advances in Oto-Rhino-Laryngology, Prof. Wolfgang Arnold, for asking me to be guest editor for a book on active middle ear implants. It was a delightful undertaking for me to organize this anthology and to invite the authors who were selected from the many experts in the various topics of this broad field. The publication of this book is very timely considering the recently expanded methods for coupling active middle ear implants to the middle ear – to the round window or in combination with passive middle ear prostheses. It is also an opportunity to review the currently marketed systems and to evaluate how they can be used to help hearing impaired patients. Over the past decade, we have witnessed a continuous evolution in the expansion of the patient selection criteria from purely sensorineural hearing losses to conductive and mixed hearing losses in difficult-to-treat ears. This book begins with a fascinating and authentic history of active middle ear implants, written by one of the main pioneers in this field. In the following chapters, the currently marketed devices and their application are described. Technical improvements have resulted not only in better speech processing but also in fully implantable middle ear implants using electromagnetic stimulators. An additional development is the launch of a new, fully implantable device with a piezoelectric stimulator. Clinical experiences and results from a large group of patients, using the range of devices, are presented in this book. I would like to extend my gratitude to all authors who prepared exceptionable manuscripts to share their experience. I am particularly thankful to Stefan-Marcel Pok for his hard work and long hours over many nights and weekends. His assistance contributed to the success of this publication. Klaus Böheim, St. Pölten

Böheim K (ed): Active Middle Ear Implants. Adv Otorhinolaryngol. Basel, Karger, 2010, vol 69, pp 1–13

The Vibrant Soundbridge: Design and Development Geoffrey R. Ball CTO Vibrant Med-El, Innsbruck , Austria

Abstract This chapter is a condensed history of the design and development of the Vibrant Soundbridge that introduces and discusses the origins of the Floating Mass Transducer and the Vibrant Soundbridge and the design philosophy that led to the invention and realization of the system. The Vibrant Soundbridge has been worked on and studied by a large group of engineers, researchers, physicians and formal advisory boards whose combined efforts have led to approval for the system as it stands today. The system and operation as well as the possible future applications for middle ear implant technology are discussed. The author also thanks the many people that have contributed to the use Copyright © 2010 S. Karger AG, Basel and increasing adoption of the Vibrant Soundbridge to date.

The goal to develop a superior electronic hearing system for the hearing impaired has had quite a history. Collins patented his first ‘electronic hearing aid’ in 1899 that featured a battery supply, amplifier and crude signal processing circuitry that drove a speaker (receiver) positioned in the ear canal. His device was crude; however, it possessed all the primary functional blocks of modern hearing aids in use today. Edison, arguably one of the greatest inventors of all time who suffered from severe hearing loss, also worked on improving the hearing aid and despite his successful work on microphones, electronics, amplifiers and batteries never commercialized a product and had to settle for founding the recording industry and many other feats. Work from the early 1900s through the 1980s was utilized to improve the packaging and function of components and then came the pioneering work of Villchur and Waldhaur that facilitated the introduction of active compression circuits that were the key breakthrough in hearing aid design [1, 2]. By recognizing that the hearing impaired had not only a loss in threshold levels, but also a decrease in dynamic range, the Villchur/Waldhaur technology was able to

provide a compressed signal into the range that was most useful for the hearing impaired. For patients suffering from sensorineural hearing loss, this was a huge improvement. This technology was first introduced by ReSound Corporation. Today, almost all modern hearing systems utilize advanced signal compression. However, though a tremendous technical and clinical success, the introduction of advanced ‘smart’ hearing aid circuitry did not significantly alter hearing aid adoption patterns. Since the 1970s, the number of hearing aid ‘owners’ as a percentage of hearing impaired has varied between 21 and 23% [3]. This means that more than 75% of hearing loss sufferers that could and should benefit from amplification do not even own an instrument. A large portion of hearing aid ‘owners’ do not even utilize their hearing aid even once a year. The number of truly active hearing aid owners that use their devices four or more hours every day is 10% or less of the total hearing impaired population that could benefit. The reason for rejection of hearing instruments by a clear majority of hearing loss sufferers is complicated and multifaceted. There is the stigma of hearing loss and wearing a hearing aid. There is the perceived lack of technology benefit; there are the many cases of unscrupulous hearing aid dispensing agents that have taken advantage by offering inferior technology at superior prices. There are the many patients that often have appropriate technology but have been unable to benefit due to inappropriate instrument fitting and/or programming of the unit to its full potential. Today, leading hearing aid companies are striving to increase adoption of amplification via educational awareness and marketing of their devices in the hope of improving adoption rates further than they have been historically. Although there have been significant improvements in total unit numbers for devices sold each year, frustratingly only incremental changes to the adoption rate as a percentage of total of sufferers have been made. A majority of cases that should be treated with amplification remain untreated despite technological improvement [3]. The field of direct-drive middle ear implant development has had quite a long history. The original theory behind middle ear development was that the primary Achilles’ heel of acoustic hearing aids was that utilizing a speaker positioned near or about the ear canal introduced signal quality losses and the opportunity to imitate a feedback path. By introducing a device that was surgically implanted, patients could have the transducer positioned in much closer proximity to the ultimate target structure, the cochlea. Such a device could in theory deliver a superior signal without feedback and could offer improvements in cosmetics and ease of use for patients. Perhaps most importantly, for patients that have tried acoustic hearing aids and returned them who have utilized these devices for multiple years and desire an alternative, middle ear implants can offer an ‘alternative’ for long-term treatment, at least for some of them. There are hundreds of thousand of patients that can not actively wear acoustic hearing aids due to medical or anatomic reasons for which middle ear implants can and often do offer the best chance of hearing remediation. Acoustic hearing aids often offer limited benefit for many patients suffering form conductive or ‘mixed’ types of

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hearing deafness. Middle ear implants have been shown in many ‘mixed’ and conductive cases to have significant objective benefit and exceptional clinical utility. With 80% or so of hearing impaired rejecting amplification, hearing loss is the single largest chronic sensory condition that typically remains untreated in medicine today. The need and demand for alternatives will only increase as the population grows and we will live longer, more productive lives. Proponents for alternative treatment options such as middle ear implants suggest that the many improvements and gains that can be achieved with this technology have been proven to benefit patients. They also argue that with a majority of sufferers with hearing loss remaining untreated there is a ‘clear and obvious’ need for alternatives for at least some patient categories. In contrast, the field of ophthalmology offers a host of alternative products and treatment options including prescription eyewear, contact lenses, corrective surgery and surgical options. The point is that for a majority of the visual impairments, more than one treatment option exists for most patients and there is a host of available products and service variants. The referral model and treatment pattern for vision impairments has been well tried and tested resulting in millions of surgical vision corrections each year. Certainly, a hearing implant or real technological or medical alternative to acoustic hearing aids can bring benefit to some portion of the population that forgoes treatment for their hearing loss. Interest in alternative treatments has brought many patients to audiology centers that may otherwise not have come and who ended up trying and adopting hearing aids. This is a good thing in my view. More than USD 1 billion have been spent to date on the development of middle ear implants. The first serious well-funded attempts began with the early research work of Drs. Suzuki and Yanigihara in Japan, who were working in collaboration with the Rion hearing aid company. Though the early results were successful and quite promising, this piezo-electric device was never approved for commercialization and the device was applied in approximately 100 subjects in clinical investigations. A snapshot of other developments include Richards Medical (now Smith and Nephew) that worked on Jorgen Heide’s middle ear electromagnetic total ossicular replacement prosthesis (TORP) device, the efforts of Perkins and Goode with the ReSound Earlens, the Implex TICA (totally implantable cochlea amplifier) and the work of many others including Maniglia, Hough, Spindel, Huettenbrink, etc. Though many of these devices and projects were significant technical achievements, in many events even stunning, for whatever reason, they have not been able to translate research and clinical achievements into commercial devices or achieve wide adoption in the field. On the one hand, this should not be a surprise as it is difficult to raise the capital required to develop an implant into form even for limited clinical trial use, and once this has been achieved to translate the research and clinical trials work into a commercially successful enterprise. The result is that today the approved devices are the Envoy Esteem (formerly St. Croix Medical), the Carina (Otologics) and the Vibrant Soundbridge (Vibrant Med-

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El). All three devices are approved and are in use within the EU and other countries. The Vibrant Soundbridge is unfortunately the only platform at the time of publishing that has been approved and is available for use in the US by the FDA since 2000. The other platforms are presently undergoing US clinical trials and we can hope to look forward to a future where several devices and designs are available. The good news is that although the number of devices that are in active use is small, the number of patients that are benefiting from these platforms continues to increase and interest is growing due to new indications and success with patients that need them.

Invention

Any good device requires a good invention. And good invention always has its share of good stories along the way. There have been many interesting moments in the development of the Vibrant Soundbridge and the invention of the FMT (Floating Mass Transducer). I can vividly recall the first time I thought about hearing implants. I was in Dr. Rodney Perkins’ chair as a patient, and we were finishing the examination and reviewing my test results and so I asked him ‘What about surgery, is there anything that you can do to fix me up?’ ‘No, not that would help your loss’ he replied. And so I said ‘What about a hearing implant, an implanted device like one of those cochlear implants.’ And he replied ‘No, those won’t help you but we are working on something, so in a couple years it could be a possibility.’ I could not have envisioned that only a few short years later I would be employed by his colleague Dr. Richard Goode and working on that very project. I could have had no idea that hearing implants and the sciences surrounding this field would become my life’s work. Noninventors often seem to think that the process of invention involves and leads to a ‘Eureka!’ moment. A moment where the light bulb of the brain fires big and the idea presents itself and one thinks ‘by Jove I’ve got it!’ Well for the FMT this was not the way that it happened. There was no true ‘Eureka!’ moment. It was a process that took many years. First, I had to understand the problem, study the ear, carry out countless dissections and engage in basic research studies. We had to perform live human studies to identify the vibrational patterns and use cadavers to try different ideas and concepts. Along the way, I had to adapt and perfect several test methods and measurement devices for basic and applied research, and then eventually develop bench testing and ultimately manufacturing tests for the incredibly small and sensitive devices required for direct drive of the middle ear. I had to design and build, often by hand in my father’s workshop late at night, new transducers. Hundreds of variants were tried and all failed for one reason or the other. All had one or more shortcomings or did not work at all. In graduate school at USC, I had taken a class in the rather obscure field of linear programming. I tried to set up the problem of middle ear implants into a linear programming model to maximize the variants that needed to be maximized (output,

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force, etc.) and to minimize the features that needed to be minimized (power consumption, size, complexity, etc.) and attempted to work out the problem. One of the key outputs of linear programming is not the actual quantitative result in itself, in fact there is often none. The output is the key learning that comes during the exercise of setting up the problem. Linear programming forces one to clearly think and re-think constraints, the desired inputs and outputs and design maximization and minimization parameters, and to constantly re-think and re-evaluate the inputs relative to the desired outputs. When done well, the nonobvious can become obvious and the new avenues for solution sets can be identified. I wish I could say that I packed all the equations into a linear programming software package and it spat out a picture of the FMT. No. That is not how it worked. I did, however, gain keen insight into the fact that there were many solution sets that were possible beyond what had previously been tried and beyond what I had tried, and that they could work. And this was the result. With this new understanding in mind I went back and evaluated all the previously tried ideas. By this time I had an absolute benefit of clearly understanding how little force and how small the displacement required to drive a vibratory structure of an ear truly was (1 ␮m = 120 dB at 1.0 kHz at the stapes footplate [4]). I absolutely understood how truly small a micron really is. And that in my view was the key. I also understood that I was involved in a strange arena of microphysics at the cellular level. I started trying new ideas, and I tried to discard everything I had previously read regarding middle ear device design and to start as much as I could ‘with a clean slate’. I began the process of building and evaluating radically different and new designs. It was not long before I built the first FMT. At first, when I started building the first of this new class of devices, I was surprised to say the least and I could not understand why they worked at all. On paper, many or most of the first units, per conventional theory, could not work, because the AC field operating on the opposite poles of the magnet should have canceled out any derived motion, and yet they did work. How could something that could not work on paper and in theory keep on working when constructed? It made no sense. It was almost like these devices were laughing at the electromagenetic principles. So at this point, I did the most illogical thing, I started trying to make these FMTs not work. And they got better. What? And then I really, really tried to build them so that they absolutely could not work. And the high frequencies got so loud that even I could hear them ringing out across the room. So I was sure it was an anomaly. These early devices did have one thing going for them, and that was that they could be made very small and biocompatible in a reliable design and with a small number of parts. I talked to my colleagues at Stanford and tried to explain this new thing and they came up with even more reasons than I had as to why the devices would not work, again I heard ‘they would cancel out’, the ‘fields were not optimized’, ‘mass was not right’, if they were made smaller the ‘anomaly would go away’. My favorite was ‘you are just wasting your time!’ And what they said sure made a certain degree of sense to me at the time. So one evening while I was making more devices out in my father’s

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garage (my father was a senior engineer with several years of experience in the electronics industry and at the time worked at National Semi-conductor; he is quite an inventor himself) and I told him what I was seeing and how I could not understand it. I explained that however I made these new transducers, they always worked, even though we all understood that they shouldn’t. Then I said ‘Dad, you know, there is something really strange about these devices, they behave like little floating mass transducers’. When I said that, it was immediately clear to both of us what these devices were. And then I said ‘It’s the FMT!’ We then went out in to the laboratory and worked into the wee hours making device after device after device. They all worked, and now that I knew what I was doing and why they were working, they all kept getting better and better and smaller and smaller. We figured out how to solve the coil/ pole position problem and now they even made sense from a physics standpoint. The next day I disclosed to Dr. Goode several optimized FMT device designs and he agreed to help me have the United States Technology Transfer Office sign over the rights of the invention to me. It took about a year for the Technology Transfer Office to assign the rights to the technology that was issued by the United States Government as I was working under a federally funded grant at the time. On the day that the final documents for the FMT technology transfer papers arrived on my desk I had another one of those memorable moments. Dr. Timothy Wild, who was working with me in the laboratory at the time, said to me ‘Geoff! What about the middle ear!’ and I said ‘Tim! It is for the middle ear!’ And then he said ‘I know, I just wanted to be the one that said that to you!’ And you know, it may sound strange, but it was at that moment that I fully recognized that the FMT was a pretty good idea. In Silicon Valley it is the highest honor to be elbowed by your colleagues about your idea or your project. I knew then that the device was going to be around for a while.

The Vibrant Soundbridge

The purpose of the Vibrant Soundbridge is to provide therapy for hearing loss for patients who, for medical reasons, cannot use or are dissatisfied with conventional acoustic hearing aids. The Vibrant Soundbridge is a direct-drive middle ear implant that amplifies the mechanical vibrations of the middle ear ossicular chain, thereby providing an amplified signal to the cochlea. Utilizing mechanical energy instead of acoustic sound presents the opportunity to deliver a more accurate and higher quality signal to the inner ear. Direct-drive devices can provide this signal without feedback and occlusion as well as offer the user significant benefit that may contribute to a significantly enhanced life quality. The development of an alternative treatment option for sensorineural hearing loss has been sought for by many investigators and hoped for by the hearing impaired for many years. This paper describes the technical aspects of the Vibrant Soundbridge.

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Introduction of the Floating Mass Transducer

We believe that the first order of the day from a device design standpoint is to ‘do no harm’ to the patient’s residual hearing. It is our opinion that a developer of directdrive devices intended for general use for the remediation of sensorineural hearing loss should strive to (1) have minimal effect on a patient’s postsurgical residual hearing, (2) minimize surgical complexity, (3) be able to operate at high functional output levels in the speech and high-frequency bands, and (4) that the systems vibratory output should mimic the response of the native middle ear. We have sought a system that utilizes a new class of transducer that works in concert with the normal biomedical function of the middle ear by enhancing its vibratory motion. Our design platform utilizes a concept called ‘inertial drive’. The principal advantage of inertial drive transducers is that they offer the opportunity to drive the ossicular chain or other middle ear structures without the requirement of additional support armatures. In theory, inertial drive devices can be designed into a system that solves the majority of the drawbacks of previous design concepts. The device that utilizes the inertial drive concept is the FMT. This transducer is a key component in the Vibrant Soundbridge. The FMT was conceived as a transducer, which will ultimately produce vibrations of the fluid that have sufficient force with which to stimulate hearing perception with minimal distortion. When sound waves strike the tympanic membrane, the middle ear structures vibrate in response to the intensity and frequency of the sound. Experimental data have shown that the biomechanics of the middle ear require less than a micron of motion to deliver significantly high sound levels to the cochlea. The experimental data also show that the middle ear vibration pattern is linear in response to sound. Therefore, a small inertial drive transducer can supply the mechanical force necessary to stimulate the middle ear with sufficient amplified signal to provide therapy for many hearing impaired. The FMT is the core technology of the Vibrant Soundbridge. Its principal function is to mechanically drive the ossicular chain while not impeding normal middle ear function(s). The FMT is defined as a transducer that includes a housing that is mounted to a vibratory structure of an ear (nominally the ossicular chain), i.e. a mass mechanically coupled to the housing vibrates in direct response to an externally generated electric signal. The vibration of the mass causes inertial vibration of the housing in order to stimulate the vibratory structure of an ear. The current embodiment of the FMT utilized is an electromagnetic configuration where the mass is a rare earth magnet held within titanium housing on a set of biasing elements. The housing supports a coil, which generates an electromagnetic field when alternating current is supplied. The field interacts with the magnetic field of the magnet, which causes the magnet and the coil/housing to vibrate relative to one another. The vibration of the housing is translated into vibrations and when attached to a vibratory structure of an ear, these vibrations are translated ultimately to the cochlea. The user then perceives sound.

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Fig. 1. Amadé AP.

This type of transducer drive is termed inertial drive. The advantage of this type of drive is that it obviates the need for additional support armature and requires only a single anchor point to the middle ear. This facilitates surgical placement of the device. In the electromagnetic configuration, utilized in the current version of the FMT, the coil and magnet are in close physical proximity to one another, which maximizes electromagnetic coupling. Displacements of 1 ␮m in the middle ear are equivalent to approximately 120 dB sound pressure level [4]; such displacement levels can be readily achieved with very small electromagnetic FMTs. The FMT is pictured in figure 1. The device is approximately 2.3 mm in length and 1.6 mm in diameter. It has a total mass weight of 25 mg. The FMT is a solenoid comprised of two coils wound around a hermetically sealed titanium alloy bobbin-shaped housing. The hermetically sealed titanium transducer housing contains a samarium cobalt rare earth magnet and a set of silicone elastomer springs. The coil wire is polymide-coated gold and has a secondary layer of mechanical protection provided by a thin coating of medical-grade epoxy. The FMT is installed by a surgeon during a 1- to 2-hour outpatient/short stay procedure. The transducer’s vibrational response has been tuned to mimic the frequency response of the middle ear.

Description of the Vibrant Soundbridge System

The Vibrant Soundbridge is comprised of two primary components. The first is the external unit called the audio processor (AP) (fig. 1). The second primary component is called surgically implanted VORP (vibrating ossicular prosthesis; fig. 2). The function of the AP is to receive and process incoming acoustical signals and to process the resultant signal and to deliver power and signal to the implanted VORP. The AP consists of a microphone, signal processing electronics, telemetry coil and a battery that

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Fig. 2. Vibrating ossicular prosthesis.

supplies power to the system. The AP sends an amplitude modulated signal across the skin to the receiver coil of the VORP. The AP is held in position postauricularly on the outside of the head during normal use by magnetic attraction. The VORP is implanted during the surgical procedure and consists of three functional components. These units are: (a) Implanted receiver unit: the implanted receiver unit receives the electromagnetic signal from the external amplification system. A demodulator circuit filters the modulated signal to the appropriate drive signal for the FMT. (b) Conductor link: the conductor link functions as the electrical conduit that connects the FMT to the implanted receiver unit. (c) Floating mass transducer: the FMT drives a vibratory structure of an ear. The important components of the VORP include the receiver coil; a polymidecoated gold wire that is inductively matched to the telemetry coil of the AP. The magnet attachment assembly, located in the center of the receiver coil, functions as the attachment magnet that holds the AP in its proper external position. An additional component of the VORP is the demodulation electronic package which contains an array of passive electronic components (resistors, capacitors and diodes) assembled on a ceramic substrate. The demodulation electronics package provides three functions: (1) it demodulates the drive signal transmitted to the VORP by the AP, (2) it protects the transducer from any potential interference sources, and (3) it limits the output of the FMT to obviate any opportunity for overstimulation.

Vibrant Soundbridge Theory of Operation

When an acoustic signal reaches the microphone (or microphones) of the AP, it is converted into an electronic signal. This signal is then processed by the signal-processing electronics and the resultant signal is then amplified and modulated into the

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appropriate drive signal, which is then transmitted across the skin to the VORP. The receiver coil of the VORP picks up the modulated signal broadcasted by the AP and sends it to the demodulation electronics package where the signal is demodulated and sent down the conductor link to the FMT. The FMT then mechanically vibrates the ossicular chain with amplified motion, ultimately stimulating the fluid of the inner ear. The user then experiences amplified sound. Rather than using acoustic sound as the drive force, the Vibrant Soundbridge delivers mechanical energy to the ossicular chain. In the partially implantable Soundbridge, the microphone of the externally worn AP picks up sound. The AP is held in position under a patient’s hair by magnetic attraction. The AP’s microphone picks up sound (note: the latest AP has two microphones) and the resultant electronic signal is amplified and sent to the internally located receiver portion of the VORP. The signal is passed down the conductor link to the FMT located on the most distal portion of the VORP. The FMT then delivers mechanical motion to the ear. To date, several thousands of subjects have been implanted with the Vibrant Soundbridge for sensorineural, conductive and mixed hearing loss. The benefits of the direct-drive devices for the majority of patients have been reported in over 50 publications to date. The AP has been continuously upgraded to take advantage of improvements in signal processing technology and to accommodate other design changes that have resulted in improved patient performance. The advantage of a system that has a minimal effect on patient’s residual hearing cannot be overstated. For any medical technology, no matter how well tested in advance, a thorough clinical study will reveal the true strengths and weaknesses of a device’s design. Studies on the Vibrant Soundbridge reveal a device that is appropriate for the prescribed indication range for sensori-neural, mixed and conductive hearing loss. The strengths, merits and areas for future improvement for the Vibrant Soundbridge have been illustrated well in many peer-reviewed publications and clinical trial reports that describe the function, performance and limits of the Vibrant Soundbridge. These will be continually augmented and updated and as I write this (October, 2009) we have just got back the first reports for the latest Amadé AP which were much better than we anticipated including much higher gain in the entire audiofrequency range (including the low frequencies) and impressive speech improvements in quiet and in noise settings. The ability for hearing improvement from improved signal processing is key to any hearing system in my view and is a key advantage of the present version of the Vibrant Soundbridge.

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The Future

Since 1999, all the basic technology has existed for us to construct a totally implantable system. In my view, the main stumbling block has always been and will continue to be the battery. Rechargeable batteries have been long overdue for a major breakthrough that affords a truly significant increase in cell capacity. TI (totally implantable) devices have arrived on the scene and are taking their first steps in the field as commercial products. I believe that a TI device really has to be more or less ‘perfect’ because the signal processing and upgrades cannot be readily changed as we can do with externally worn APs. As a hearing impaired person, I struggle with the question as to how often does the average person truly need a TI? I really don’t want to hear or need to hear acoustic sound when I am underwater or swimming laps. And when showering for a few minutes, well yes, I cannot wear an AP in the shower either, but I think this is a minor inconvenience, not a strong rational for a TI. I do, however, believe that the TI will become a good option one day in the future, especially once the batteries have improved and the devices can be made even smaller than they are now and offer specific human-factor advantages and cosmetics for patients that do not have enough hair. I also think that in the future they could be particularly well suited for children and exceptionally for athletic individuals. However, there are also benefits for transcutaneous partially implanted systems that are undeniable and so I reckon there will be a need for both in the foreseeable future. The main benefit for TI design at present appears to be and do with cosmetic and perceptual issues. So far, increased performance from the TI configuration above partially implantable systems has not been proven. However, I am quite certain that there is a lot more to the TI riddle that we need to and will come to understand better. What design components do we maximize, what do we need to minimize and what are the right trade-offs from a design perspective? What are the right inputs and deliverables? What human factors improvements can be made and what are the performance benefits? It is my view that a TI device should ideally work at least as well and preferably better than a transcutaneous system in terms of gain and output and speech improvement scores. My guess would be that the TI concept will be most relevant and perhaps most important for cochlear implant users, but we shall see how the topic develops. At present, many new implant designs are being worked on and are speeding down the development pipeline. There is much to be excited about! My personal view is that I now think that the ‘Holy Grail’ for hearing devices may not be one specific device or one specific design permutation, but rather the ability to support and deliver a complete family of devices for the treatment of differing hearing loss types and degrees. In other words, instead of one perfect ‘stand alone’ system, perfection is likely to rather be in the arrival of a plurality of implant designs and configurations with different stimulation types, or a combination of operational modes that, when taken together, can remediate the majority of hearing loss cases in need of alternative treatment with an arsenal of approaches that can be deployed in the surgical theater.

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Conclusion

We believe that the device that is now approved for use today is the realization and culmination of several disciplines working together towards a common goal, i.e. the development of a surgical treatment for hearing loss. This arena offers hope and help for many hearing-impaired patients and for many expanded indications. As research in this area continues, we expect to see new developments that continue to improve direct-drive technology and expand the ability of the technology to address additional hearing loss categories.

Acknowledgements There is no letter ‘I’ in the word ‘team’. Dr. Goode approved the appropriate rights to the FMT to be assigned to me by applying to the ‘Technology Transfer Office’ for transfer of my inventions. I also need to extend Ugo Fisch unending gratitude for his help with the input into the basic design concept and in particular work on the lead, size and developmental work on the surgical method for the VORP and for his participation in the original SAB meetings. In addition to Ugo Fisch as the PI of the EU VSB clinical trial, key participants include Cor Cremers, Thomas Lenarz, Benno Weber, Gregorio Babighian, Alain Uziel, David Proops, Alec F. O’Connor, Robert Charchon, Jan Helms and Bernard Fraysse. Anders Tjellstrom published the results of our first ‘Acute Trial of the Vibrant Soundbridge’ in 1997 and was the first to publish the observation that the VSB could ‘also be used to treat conductive hearing loss’. The first patient was implanted by Ugo Fisch in 1996. The first known use of the Vibrant Soundbridge to clinically treat conductive and mixed loss was by Thibaud DuMon in France, Vittorio Colletti pioneered the use of the FMT in alternative locations on the RW beginning in 2005. Key breakthrough! There were so many others with so many ‘firsts’ that helped us along the way that to come up with a complete list without leaving someone off that should be on it would be quite an impossible task! In the USA, Dr. Hough was the ‘Principal Investigator’ for the Vibrant Soundbridge clinical trials and he and his team including Dr. Stan Baker, Dr. Dormer and Dr. Gan helped tremendously with the development of our original surgical development along with the help from all their team members. The invaluable work of other surgeons that participated in the SAB and clinical trials included (but are not limited to) Charlie Luetje, Derald Brackman, Thomas Balkany, Jennifer Maw, David Kelsall, Douglas Backous, Richard Miyamoto, Simon Parisier and Alexander Arts. There were also many USA audiologists that helped with our clinical trial work including Deborah Arthur, Christine Menapace, Pamela Mathews, Darcy Benson, Theresa Clarke, Charles Berlin and many more. The attachment clip project was completed by Chris Julian with the help of the SAB input. The implant attachment magnet concept for the VORP we licensed from the University of Oklahoma, the original size for the FMT (same as it is today) was again arrived at with Ugo Fisch and others and in T-bone studies conducted by me and Stan Baker. The surgery was developed again with the SAB members in the EU and USA and the original implant telemetry scheme was based on the work that Erwin and Ingeborg Hochmair used for cochlear implants. Hans Camenzind was my original ‘Angel’ investor, followed by B.J. Cassin, Peter McNerney and Karen Bozie. Ron Antipa helped me with the original business plans and to arrange the funding for Symphonix and to him I am eternally grateful. On the Symphonix design team, we had Bob Katz, Craig Mar, Dan Wallace, Chris Julian, Tim Dietz, Eric Jaeger, Duane Tumlinson and Frank Fellenz on the implant side. On the AP development side, there was Bruce Arthur, Jim Culp, John Salsbury, Steve Trebotich, Wyn Robertson and

12

Ball

several other engineers. Manufacturing the tiny FMTs was developed by Pat Rimroth, Ahn Troung and Sue Clarke. Many of these people are listed on the patents where they had made appropriate contributions resulting in issued claims. Bruce Maxfield and I developed the original detailed mathematics that describe how FMTs work. Special thanks to Peter Hertzman, Alf Merriweather, Beth Anne McDonald, Jeff Rydin, Mike Arendt, the Symphonix sales and clinical support staff, and the many other key support personnel from Symphonix times. Today, the VSB is supported by our R&D staff including Peter Lampbacher, Marcus Shmidt, Klaus Holzer, Ali Mayr, Markus Nagl, Michael Santek, Klaus Triendl, Bernd Gerhardter and many others on the RA, QA and clinical sides and of course Ingeborg Hochmair as CEO. She saved the Vibrant Soundbridge and has been the greatest! I would also like to thank all the people that helped on the ‘save the Vibrant Soundbridge project’ by moving the operating assets from San Jose, Calif. to our new home in Austria. Especially Alexander Mayr, Linda Ferner, Martin Kerber, Walter Fimml, Klaus Holzer and the Med-El transfer team. Then of course there are the many others that have helped me out personally including Joe Roberson, Klaus Boeheim, Wolfgang Baumgartner, Alex Huber, Norbert Dillier, Timothy Wild, Thomas Lenarz, Jon Spindel, Michel Beliaff, Bill Perry, Joachim Mueller and Harry Robbins. Special thanks also go to Jan Helms for his willingness to spend extra time with me over the years. Invaluable all! For the many researchers that have contributed original work I thank you! I think there are too many to list again and I applaud the many people that have earned higher academic PhDs and other degrees for ‘original work’ for the Vibrant Soundbridge, FMT and related topics. Thanks to the entire Japanese team at Ehime for working with me all these years! Again, thanks to Dr. Goode, who imprinted his view of hearing and the world of all things otology, engineering, medical, philosophical, design and invention wise upon me and my paltry inferior brain comparatively. He was a great teacher and mentor, and I thank him so much for believing in and taking a chance on me. And sorry for the days when the Goode maxim ‘When the surf is good the lab ain’t doing what it should!’ was sometimes correct. Be assured those were epic days! We always say we are treating hearing loss, we are doing so much more for so many, we are really giving people new and better lives and enjoyment of the world of sound and helping to reduce hearing loss as a barrier to communication with others. As for me. I’m not yet finished. I assure you.

References 1 Villchur E: Signal processing to improve speech intelligibility in perceptive deafness. J Acoust Soc Am 1973;53:1646–1657. 2 Villchur E: Simulation of the effect of recruitment on loudness relationships in speech (demonstration disk bound in with article). J Acoust Soc Am 1974; 56:1601–1611.

3 Kochkin S: Hearing Review – July 2005. MarkeTrak VII: Hearing Loss Population Tops 31 Million (available online at www.hearingreview.com). 4 Goode RL, Ball G, Nishihara S, Nakamura K: Laser Doppler vibrometer (LDV) – a new clinical tool for the otologist. Am J Otol 1996; 17:813–822.

Geoffrey R. Ball CTO Vibrant Med-El Fürstenweg 77 AT–6020 Innsbruck (Austria) Tel. +43 0 512 28 88 89 251, Fax +43 0 512 28 88 89 299, E-Mail geoff.ball @ medel.com  

The Vibrant Soundbridge

 

13

Böheim K (ed): Active Middle Ear Implants. Adv Otorhinolaryngol. Basel, Karger, 2010, vol 69, pp 14–19

Cost-Effectiveness of Implantable Middle Ear Hearing Devices Ad Snik · Veronique Verhaegen · Jef Mulder · Cor Cremers Department of Otorhinolaryngology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands

Abstract Objective: To assess the relation between cost and effectiveness of implantable middle ear hearing devices in patients with pure sensorineural hearing loss. Design: Literature review. Results: Four studies were identified that described the effect of middle ear implantation on quality of life in groups of at least 20 patients. Several different quality of life questionnaires were used. Conclusions: Our review demonstrated that middle ear implantation is a cost-effective health care intervention in patients with sensorineural hearing loss who suffered an additional therapy-resistant chronic exCopyright © 2010 S. Karger AG, Basel ternal otitis.

Middle ear implantation is a relatively new treatment for patients with sensorineural hearing loss who do not benefit from conventional hearing aid fitting. Today’s middle ear hearing aids are still semi-implantable devices. They comprise an audioprocessor with microphone, electronics and FM transmitter, which is worn externally. The audioprocessor is in (magnetic) contact with an implanted receiver unit, placed just below the skin in the mastoid region [1]. This receiver is connected to the output transducer that is coupled to one of the middle ear ossicles. Recently, middle ear implants have been applied to patients with conductive or mixed hearing loss. The transducer is coupled directly to the cochlea via one of the cochlear windows [2]. In contrast to a conventional hearing aid, the application of a middle ear implant involves surgery and much higher financial costs. These features have led to healtheconomic questions regarding treatment effectiveness in relation to the cost. Let us first consider effectiveness. To assess the effect of a medical intervention on a patient’s feeling of well-being, questionnaires are often administered. One option is the use of generic health-related quality of life (HR-QoL) questionnaires, such as the

Short Form 36 (SF-36) [3, 4], the EuroQol [5] or the Health Utility Index [6]. In principle, these HR-QoL questionnaires are not disease-specific and can therefore be applied across the borders of a specific disability. The main outcome of most generic HR-QoL questionnaires is one single measure called utility. It ranges between 1 (perfectly happy) and 0 (death). The change in utility owing to a specific intervention is called the utility gain and it is used to determine the quality-adjusted life-years or QALYs. A QALY is the utility gain in a group of patients multiplied by the life expectancy after the intervention [7, 8]. The second option is to use hearing handicap-specific QoL questionnaires. Several studies that used generic HR-QoL questionnaire scores showed only small changes in utility gain after conventional hearing aid fitting [9]. This is in direct contrast with handicap-specific questionnaires that mostly demonstrated significant improvements [10]. It has been concluded that most generic HR-QoL questionnaires are not sensitive to problems associated with audition and communication [9, 11]. Furthermore, when different HR-QoL questionnaires were used in parallel to assess the benefit of hearing interventions, wide interquestionnaire variability was found [11, 12]. Therefore, handicap-specific questionnaires have been introduced to measure QoL after hearing interventions and they have become very popular. Examples are the Glasgow Benefit Inventory [13], the Nijmegen Cochlear Implant Questionnaire [14, 15] and the International Outcome Inventory for hearing aid provision [16]. These questionnaires have well-described structures and have been validated; however, they do not provide utility scores. Let us take a closer look at these questionnaires. The Glasgow Benefit Inventory (GBI): The GBI is a HR-QoL questionnaire that was specially developed to measure outcomes of otorhinolaryngological interventions; it is a retrospective standardized questionnaire that examines the impact of the treatment on the health status of the patient [13]. Scores can range from –100 (profound deterioration) to +100 (excellent improvement). Twelve of the 18 questions are about general health, 3 questions concern social functioning and 3 concern physical health. The GBI has been used successfully to evaluate the bone-anchored hearing aid [14] and cochlear implants [15]. The Nijmegen Cochlear Implant Questionnaire (NCIQ): The NCIQ is an HR-QoL questionnaire that was specially developed to assess longitudinal health status after cochlear implantation [16, 17]. It addresses three functional domains: physical (communication related), social and psychological functioning. Each subdomain contains at least 10 items. The overall scores per subdomain range from 0 (very poor) to 100 (optimal). The three domains showed acceptable consistency statistics, test-retest coefficients and responsiveness indexes [16, 17]. In a long-term follow-up study on adults with cochlear implants, the NCIQ scores were fairly consistent over time [18]. Nowadays, the NCIQ is being widely used [18–22]. It has been used for example to compare quality of life between cochlear implant users and hearing aid users with severe hearing loss [18, 22].

Cost-Effectiveness of Middle Ear Hearing Devices

15

The International Outcome Inventory for Hearing Aids (IOI-HA): This seven-item, self-report survey has been translated into more than 20 languages [23]. Each of the seven items targets a different field, namely daily use, benefit, residual activity limitation, satisfaction, residual participation restriction, impact on others and quality of life. Scores range from 1 (poor) to 5 (optimal). The psychometric properties have been studied extensively and norms have been established from large groups of conventional hearing aid users [23].

Cost-Utility Ratio of Hearing Intervention

The direct cost of treatment can be divided into the phases of selection, implantation and rehabilitation [7, 8, 24]. To calculate the cost-per-QALY of middle ear implantation, we need to know the direct cost and utility gain. However, owing to the variation in utility scores across generic HR-QoL questionnaires, as referred to above, such calculations are not straightforward. Let us look at the cost-per-QALY determination of conventional hearing aid fitting according to Grutters et al. [12]. They used four different generic HR-QoL questionnaires in parallel to assess a group of 315 patients who had been fitted with hearing aids for the first time. Utility gain values obtained with the four questionnaires differed by a factor of 40 and, as a consequence, the calculated costper-QALY also differed by this unacceptable range of 40. Thus, the cost-per-QALY seems to primarily depend on the generic HR-QoL questionnaire used and not on the effectiveness of the intervention or its cost. Therefore, any health-economic evaluation of hearing interventions based on the cost-per-QALY concept can be questioned. Handicap-specific QoL might form an alternative way to assess cost utility. As cochlear implantation in postlingually deaf adults has an acceptable cost-utility ratio [7, 8, 25], the effectiveness of a new type of implantation might be determined by comparing the outcomes of handicap-specific QoL questionnaires after the new treatment to those of cochlear implantation. Next, the cost of the new intervention must be calculated and compared to that of cochlear implantation. Based on the relative effectiveness and the relative cost, it can be concluded whether or not the new treatment is more or less cost-effective than cochlear implantation [26].

Quality of Life and Middle Ear Implantation: A Review of the Literature

QoL in relation to middle ear implantation was studied in a substantially large group of patients (n 6 20) in four papers [26–29]. Sterkers et al. [27] published the results of a French multicenter trial on patients with pure sensorineural hearing loss, implanted with the Vibrant Soundbridge middle ear hearing device (Med-El, Innsbruck, Austria). They used the inclusion criteria advocated by the manufacturer. Recently, longterm data have been published on the same group [28]. To evaluate patient benefit, the

16

Snik · Verhaegen · Mulder · Cremers

Table 1. Mean GBI data from 3 different studies: total score and mean scores per subdomain are presented Study

Number of patients GBI score Total General score Physical health Social interaction

Snik et al. [26]

Sterkers et al. [27]

Mosnier et al. [28]

Schmuziger et al. [29]

17

57

62

20

32.9 41.5 15.7 17.6

15.4 20.0 0.0 11.5

17.8 22.8 1.7 14.1

14.7 22.1 –5.0 5.0

GBI was used. In 57 patients, the mean overall improvement was 15 points (on a scale from –100 to +100) in the initial study and 18 points in the long-term study [27, 28, respectively]. Table 1 presents the mean scores on each of the three GBI subscales. Schmuziger et al. [29] published their retrospective data on a group of 20 Vibrant Soundbridge users with pure sensorineural hearing loss. They also employed the inclusion criteria advocated by Med-El. The GBI and the IOI-HA were applied to obtain data. Overall improvement on the GBI was 15 points (table 1), while the IOI-HA showed an overall postintervention score of 3.7 (on a scale from 1 to 5). For reference purposes, the authors compared their results to the norm data reported by Cox et al. [23]. After conventional hearing aid fitting, the mean norm score in the latter study was 3.6, which was almost the same as the IOI-HA score from the middle ear implant users. Snik et al. [26] presented the results of a prospective quality of life study on 21 patients with sensorineural hearing loss who received a middle ear implant. The devices comprised either the Vibrant Soundbridge or the Otologics MET (Otologics Company, Boulder, Colo., USA). Treatment cost was determined based on the direct cost of implantation, rehabilitation and 1 year of aftercare. The total cost was EUR 14,354 per middle ear implant, irrespective of the type. To assess effectiveness, the patients filled out the generic SF-36 and NCIQ before and at 6 and 12 months after implantation [26]. The GBI was filled out once, between 6 and 12 months after implantation. In contrast with the other three papers, the patients described by Snik et al. [26] were all suffering from chronic, therapy-resistant external otitis. The SF-36 outcome showed only minimal improvement after the intervention. In agreement with Brazier et al. [4], the mean utility gain on the SF-36 was 0.01 (on a scale from 0 to 1). This small improvement in SF-36 utility is explained by the statement in the Introduction section that most generic HR-QoL questionnaires are too insensitive to hearing problems. Based on this utility gain, the cost-per-QALY was high: it exceeded EUR 70,000. In contrast, all three domains of the NCIQ showed substantial improvement in the scores after middle ear implantation (p ^ 0.01), while the mean GBI score was 33 points, which indicated a highly significant improvement (p ! 0.001).

Cost-Effectiveness of Middle Ear Hearing Devices

17

Next, Snik et al. [26] compared the middle ear implantation NCIQ subscale scores to those obtained in their previous cochlear implant study on postlingually deaf adults [16, 17]. Analyses showed that cochlear implantation was 1.5–2.5 times more effective than middle ear implantation, whereas middle ear implantation was 3.3 times cheaper than cochlear implantation. These findings suggest that middle ear implantation is more cost-effective than cochlear implantation. The GBI score in the study by Snik et al. [26] was considerably higher than that reported in the other studies (table 1). This might have been due to their inclusion criterion of external otitis. Such patients cannot tolerate an ear mould, or they can only tolerate the occlusion for a few hours per day. A middle ear implant enabled these patients to hear again without any pain or itching in the ears. Table 1 shows that this group of patients had higher GBI scores throughout. The most profound difference was seen in the physical health domain. As stated above, all the patients studied by Snik et al. [26] had comorbid external otitis in contrast with Sterkers et al. [27] and Schmuziger et al. [29], whose patients comprised dissatisfied conventional hearing aid users alone. The relatively low GBI scores reported by Sterkers et al. [27], Mosnier et al. [28] and Schmuziger et al. [29] indicate limited benefit. This conclusion is in agreement with the post-intervention IOIHA scores presented by Schmuziger et al. [29]. Their IOI-HA scores showed that middle ear implants did not have a surplus value compared to conventional hearing aids. In conclusion, middle ear implantation seemed to be cost-effective in patients with sensorineural hearing loss and with comorbid chronic external otitis. Our literature review suggested that this conclusion may not apply to patients with pure sensorineural hearing loss who dislike conventional air-conduction devices for whatever reason and are searching for an alternative.

References 1 Miller DA, Fredrickson JM: Implantable hearing aids; in Valente M, Hosford-Dunn H, Roeser RJ (eds): Audiology: Treatment. New York, Thieme Medical Publishers, 2000, pp 489–510. 2 Colletti V, Soli SD, Carner M, Colletti L: Treatment of mixed hearing losses via implantation of a vibratory transducer on the round window. Int J Audiol 2006;45:600–608. 3 Ware JE, Sherbourne CD: The MOS 36-item shortform health survey (SF-36): conceptual framework and item selection. Med Care 1992; 30:473–483. 4 Brazier J, Roberts J, Deverill M: The estimation of a preference-based measure of health from the SF-36. J Health Econ 2002;21:271–292. 5 The EuroQol Group: EuroQol – a new facility for the measurement of health-related quality of life. Health Policy 1990;16:199–208.

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6 Feeny D, Furlong W, Torrance GW, Goldsmith CH, Zhu Z, DePauw S, Denton M, Boyle M: Multi-attribute and single-attribute utility functions for the health utilities index mark 3 system. Med Care 2002; 40:113–128. 7 UKCISG (UK Cochlear Implant Study Group). Criteria of candidacy for unilateral cochlear implantation in postlingually deafened adults. II. Cost-effectiveness analysis. Ear Hear 2004; 25:336–360. 8 Palmer CS, Niparko JK, Wyatt JR, Rothman R, De Lissovoy G: A prospective study of the cost-utility of the multichannel cochlear implant. Arch Otolaryngol Head Neck Surg 1999; 125:1221–1218. 9 Bess FH: The role of generic health-related quality of life measures in establishing audiological rehabilitation outcomes. Ear Hear 2000; 21:74S–79S.

Snik · Verhaegen · Mulder · Cremers

10 Chisolm TH, Johnson CE, Danhauer JL, Potz LJP, Abrams HB, Lesner S, McCarthy PA, Newman CW: A systematic review of health-related quality of life and hearing aids: final report of the American Academy task force on the health-related quality of life benefits of amplification in adults. J Am Acad Audiol 2007; 18:151–183. 11 Barton GR, Bankart J, Davis AC, Summerfield QA: Comparing utility scores before and after hearing aid provision: results to the EQ-5D, HUI3 and SF6D. Appl Health Econ Health Policy 2004;3:103–105. 12 Grutters JPC, Joore MA, van der Horst F, Dreschler WA, Anteunis LJC: Choosing between measures: comparison of EQ-5D, HUI2, HUI3 in persons with hearing complaints. Qual Life Res 2007; 16: 1439–1449. 13 Robinson K, Gatehouse S, Browning GC: Measuring benefit from otorhinolaryngological surgery and therapy. Ann Otol Rhino Laryngol 1996; 105: 415–422. 14 Krabbe PFM, Hinderink JB, Van den Broek P: The effect of cochlear implant use in postlingually deaf adults. Int J Technol Assess Health Care 2000; 16: 864–873. 15 Snik AFM, Mylanus EAM, Proops DW, Wolfaardt JF, Hodgetts WE, Somers T, Niparko JK, Wazen JJ, Sterkers O, Cremers CW, Tjellström A: Consensus statements on the BAHA system: where do we stand at present? Ann Otol Rhinol Laryngol Suppl 2005; 195:2–12. 16 UKCISG (UK Cochlear Implant Study Group). Criteria of candidacy for unilateral cochlear implantation in postlingually deafened adults I: Theory and measures of effectiveness. Ear Hear 2004; 25: 310– 335. 17 Hinderink JB, Krabbe PFM, Van den Broek P: Development and application of a health related quality of life instrument for adults with cochlear implants: the Nijmegen Cochlear Implant Questionnaire. Otolaryngol Head Neck Surg 2000; 123: 756–765. 18 Damen GW, Beynon AJ, Krabbe PF, Mulder JJ, Mylanus EA: Cochlear implantation and quality of life in postlingually deaf adults: long-term followup. Otolaryngol Head Neck Surg 2007;136:597–604. 19 Klop WM, Boermans PP, Ferrier MB, van den Hout WB, Stiggelbout AM, Frijns JH: Clinical relevance of quality of life outcome in cochlear implantation in postlingually deafened adults. Otol Neurotol 2008:29;615–621.

20 Baumgartner WD, Jappel A, Morera C, Gstöttner W, Müller J, Kiefer J, Van De Heyning P, Anderson I, Nielsen SB: Outcomes in adults implanted with the FLEX soft electrode. Acta Otolaryngol 2007; 127:579–586. 21 Hirschfelder A, Gräbel S, Olze H: The impact of cochlear implantation on quality of life: the role of audiologic performance and variables. Otolaryngol Head Neck Surg 2008; 138:357–362 22 Cohen SM, Labadie RF, Dietrich MS, Haynes DS: Quality of life in hearing-impaired adults: the role of cochlear implants and hearing aids. Otolaryngol Head Neck Surg 2004;131:413–422. 23 Cox RM, Alexander GC, Beyer CM: Norms for the International Outcome Inventory for Hearing Aids. J Am Acad Audiol 2003; 14:403–413. 24 Severens JL, Bokx JPL, Van den Broek P: Cost analysis of cochlear implants in deaf children in the Netherlands. Am J Otol 1997; 18:714–718. 25 Cheng AK, Niparko JK: Cost-utility of cochlear implant in adults: a meta-analysis. Arch Otolaryngol Head Neck Surg 1999;125:1214–1218. 26 Snik AF, van Duijnhoven NT, Mylanus EA, Cremers CW: Estimated cost-effectiveness of active middle-ear implantation in hearing-impaired patients with severe external otitis. Arch Otolaryngol Head Neck Surg 2006; 132:1210–1215. 27 Sterkers O, Boucarra D, Labassi S, Bebear J-P, Dubreuil C, Frachet B, Fraysse B, Lavieille J-P, Magnan J, Martin C, Truy E, Uziel A, Vaneecloo FM: A middle ear implant, the Symphonix Vibrant Soundbridge: retrospective study of the first 125 patients implanted in France. Otol Neurotol 2003; 24: 427– 436. 28 Mosnier I, Sterkers O, Bouccara D, Labassi S, Bebear JP, Bordure P, Dubreuil C, Dumon T, Frachet B, Fraysse B, Lavieille JP, Magnan J, Martin C, Meyer B, Mondain M, Portmann D, Robier A, Schmerber S, Thomassin JM, Truy E, Uziel A, Vanecloo FM, Vincent C, Ferrary E: Benefit of the Vibrant Soundbridge device in patients implanted for 5 to 8 years. Ear Hear 2008;29:281–284. 29 Schmuziger N, Schimmann F, àWengen D, Patscheke J, Probst R: Long-term assessment after implantation of the Vibrant Soundbridge device. Otol Neurotol 2006; 27:183–188.

A. Snik ENT Department – 377, Radboud University Nijmegen Medical Centre PO Box 9101 NL–6500 HB Nijmegen (The Netherlands) Tel. +31 243 614 927, E-Mail [email protected]

Cost-Effectiveness of Middle Ear Hearing Devices

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Böheim K (ed): Active Middle Ear Implants. Adv Otorhinolaryngol. Basel, Karger, 2010, vol 69, pp 20–26

Indications and Candidacy for Active Middle Ear Implants F. Wagner · I. Todt · J. Wagner · A. Ernst Department of Otolaryngology, ukb, Hospital of the University of Berlin (Charité Medical School), Berlin, Germany

Abstract Currently, there are two active middle ear implants available commercially: the Vibrant Soundbridge system and the Carina system. A third active middle ear implant, the Esteem, is under clinical evaluation. All devices are indicated for patients with moderate-to-severe hearing loss. Because active middle ear implants are directly coupled to middle ear structures, many of the problems that patients with conventional hearing aids report, such as acoustic feedback, occlusion, and irritation of the outer ear canal, are avoided. In addition, AMEI patients perform well in background noise. However, indications for AMEIs are selective and candidates should be carefully evaluated before surgery. Before considering an AMEI, patients should be provided with conventional hearing aids. Only when benefit is insufficient and audiological selection criteria are met is further candidacy evaluation indicated. Since Colletti described coupling the Vibrant Soundbridge directly onto the round window membrane in 2006, the indications for the Vibrant Soundbridge have expanded and the VSB is implanted in patients with conductive and mixed hearing losses. Patients have often undergone middle ear surgery before. Especially mixed hearing loss cases with 30–60 dB HL sensorineural hearing impairment and 30–40 dB HL air-bone gaps may be helped by this new application. Copyright © 2010 S. Karger AG, Basel

Active middle ear implants (AMEIs) have been implanted for more than 10 years. Today’s commercially available AMEIs are manufactured by MED-EL, Innsbruck, Austria (the Vibrant Soundbridge, VSB [1–4]) and by Otologics LLC, Boulder, Colo., USA (the Carina [2, 5, 6]). The Esteem AMEI from Envoy Medical Corporation, Minneapolis, Minn., USA, has the CE mark as all the other systems above. There have been other systems that were not developed into commercial products and have not been approved [7–12]. The indication for AMEIs is primarily based on audiological criteria. AMEIs are indicated for patients with moderate-to-severe sensorineural hearing loss (SNHL), who have not undergone middle ear surgery before and have been unsuccessfully treated

with conventional hearing aids. However, these indications have recently been extended to include patients with conductive and mixed hearing loss who otherwise meet the selection criteria for the VSB. Patients with previously operated middle ears and mixed hearing loss [13] may particularly benefit. For both groups, an unsuccessful trial of conventional hearing aids is obligatory before considering an implantation, unless hearing aids are medically contraindicted. Although conventional hearing aids have improved tremendously in the last years, high frequency hearing losses of 70–80 dB HL or more are often difficult to fit satisfactorily. Other candidates for AMEIs are patients who have difficulties with or who have rejected conventional or bone anchored/conduction hearing aids. Some patients suffer from recurrent otitis externa when using conventional hearing aids, and others complain of acoustic feedback or of an occlusion effect, resulting from the outer ear canal being plugged by an earmould [14, 15]. Outer ear canal problems such as stenosis, exostosis or excessive cerumen accumulation may also prevent conventional hearing aid use. Physicians using stethoscopes, musicians and singers may require an open outer ear canal. In addition, the sound quality of AMEIs may be better than conventional hearing aids, especially in background noise [16]. In addition to audiological and medical criteria, candidate selection should also include psychological, socioeconomic and clinical assessments. Junker et al. [17] screened a database of 45,350 patients with known SNHL for VSB hearing implant candidacy. Within the greater Berlin area, 0.76% of the patients were potential candidates, based on pure-tone audiograms. Potential candidates were invited for a further evaluation, which was completed in only 0.16% of the patients. A large number of potential candidates where not interested for various reasons. Reasons for disinterest were fear of an operation, satisfaction with current hearing aids, and that the hearing implant could not be tried out before surgery. The VSB includes preoperative demonstration equipment, but this does not deliver sound in exactly the same way as the implant. Potential candidates’ audiologic needs were the major factor, rather than aesthetic or financial reasons, in the decision-making process. Following a second screening, 0.09% of the 45,350 database patients were scheduled for surgery [17]. AMEIs will likely not replace conventional hearing aids because there are fewer candidates. However, candidates are patients who are motivated to try a VSB because they are not satisfied with their hearing aids. As the number of candidates increases, the more necessary it will be to analyze the cost-effectiveness of AMEIs. To date, there are few cost-effectiveness studies in contrast to the large number of studies on cochlear implants and conventional hearing aids [18, 19]. There is one report on patients with chronic otitis externa [20].

The Vibrant Soundbridge AMEI

The VSB AMEI has shown good reliability for more than 10 years, and several thousand patients have been successfully implanted since 1996. The VSB consists of an external audioprocessor including a microphone, a battery and a digital signal pro-

Indications and Candidacy for AMEIs

21

Frequency (kHz)

Hearing eve (dB)

0.1 0.2 0.5 0.7 1 1.5 2

a

0 10 20 30 40 50 60 70 80 90 100 110

3

Frequency (kHz) 4

6

8

0.1 0.2 0.5 0.7 1 1.5 2

3

4

6

8

b

Fig. 1. Audiological indication for the Vibrant Soundbridge system. a Classical approach with coupling of the FMT to the incus for patients with SNHL. b Alternative approach with coupling of the FMT to the round window membrane, remaining ossicular chain structures, oval window or modified total ossicular replacement prosthesis (TORP) for patients with mixed hearing loss (light gray indicates the sensorineural part of hearing loss, dark gray indicates the conductive part of hearing loss).

cessing chip. The internal implant, called the vibrating ossicular prosthesis (VORP), is connected to the implanted floating mass transducer (FMT). Signal transduction via the audioprocessor and the VORP to the FMT causes the FMT to vibrate, which mechanically transfers the signal on to the cochlea. The technical characteristics of the VSB are described in many reports [1, 21, 22]. The VSB was originally intended for patients with moderate-to-severe SNHL, especially SNHL in the high frequencies [4, 23, 24]. For the SNHL indication, the FMT is clipped on to the incus, and an incoming signal induces FMT vibration to the incus, stapes, oval window and the cochlea. Patients with SNHL who can not be satisfactorily fit with conventional hearing aids or who suffer from recurrent otitis externa are candidates for FMT placement on the incus. The VSB is especially helpful when hearing aid benefit is limited for hearing thresholds of 70–80 dB HL. Figure 1a shows the audiological indication area for SNHL with placement of the FMT on the incus. A comprehensive evaluation of patients includes pure-tone audiometry, tympanometry and stapedius reflex testing, as well as otoscopy, to confirm patients’ good middle ear function. Speech intelligibility results should be at least 50% correct words presented at a comfortable listening or conversational speech level. Testing should be done using headphones and standardized tests. There should be no evidence of retrocochlear or central hearing impairment, and hearing thresholds should be stable over at least the past 2 years. The skin of the scalp, where the audioprocessor is placed after VSB implantation, should be free of any skin conditions that could prevent wearing the audioprocessor. The VSB may be implanted in the ear with the worse hearing, but both ears should be thoroughly evaluated. Before considering implantation of an AMEI, the patients’ expectations should be assessed. Successful implantation can only be achieved when expectations are realistic and the patient is motivated.

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In 2006, Colletti et al. [13] describe placing the FMT of the VSB directly onto the round window membrane. Using this technique, they were able to successfully treat seven patients with mixed hearing loss. They showed that, especially in difficult-totreat patients with mixed hearing loss with a 30- to 60-dB HL sensorineural component and a 30- to 40-dB air-bone gap, coupling the FMT directly onto the round window membrane presented a new option for patients with previous, unsuccessful middle ear surgery. Patients with chronic middle ear disease, recurrent cholesteatoma or Eustachian tube dysfunction may be candidates. The motivation to couple the FMT onto the round window membrane is based on research by Wever and Lawrence [25], which showed positive results of acoustically stimulating the round and oval window membranes. Figure 1b shows the audiologic indication area for alternative FMT coupling. Before considering implantation, tympanoplastic surgery should have been performed. As for classic coupling of the FMT to the incus, bone conduction thresholds should be stable over the past two or more years, auditory neuropathy and retrocochlear pathologies should be ruled out, and conventional hearing aids should be tried before implantation (on both ears). Before surgery, a CT scan of the middle ear should be performed. Other potential candidates for FMT coupling on the round window are patients with middle ear malformations. Implantation can be combined with outer ear plastic surgery, if the outer ear is malformed. Wollenberg et al. [26] reported on VSB implantation in combination with outer ear reconstruction in 3 patients with a dysplastic incus or stapes. It was possible to reduce the air-bone gap by about 20 dB so that aided thresholds were about 20–40 dB HL. In addition, direct coupling to the stapes or its remaining suprastructure [27] and a combination of stapes prosthesis and FMT coupling have been described [28]. Recently, Streitberger [29] described directly coupling the FMT to the oval window. In 2008, Hüttenbrink et al. [30] presented a total ossicular replacement prosthesis that can be combined with the vibrating tranducer of an AMEI and placed on the stapes footplate. In an evaluation of potential candidates with mixed hearing loss for the VSB, we found similar results as Junker et al. [17] who screened 45,350 patients with a pure SNHL. From a database of 44,245 patients (Department of Otolaryngology, University of Heidelberg) who met the audiological selection criteria, only 2.2% were interested in further candidacy evaluation. The number of candidates selected from a patient database of previously operated middle ears was also small. Out of 850 patients (database of the Department of Otolaryngology at the ukb, Berlin), only 2.4% met the audiologic selection criteria and were interested in an AMEI [Wagner et al., 2009, in press]. In addition to patients with mixed hearing loss, the alternative round windowplacement of the Vibrant Soundbridge FMT is also indicated for patients with pure conductive hearing loss. For these patients, bone-anchored hearing aids, such as the BAHA, are also an alternative and are less expensive but aesthetically less favorable.

Indications and Candidacy for AMEIs

23

Frequency (kHz)

Hearing eve (dB)

0.1 0.2 0.5 0.7

Fig. 2. Audiological indication range for the Carina system (PTA). Indications, candidate selection for active middle ear implants.

1

1.5

2

3

4

0 10 20 30 40 50 60 70 80 90 100 110

The Carina AMEI

The Carina is a fully implantable AMEI. It consists of an implant body, the programming system, the charging set and the remote control. The implant itself includes electronic components, a microphone and a middle ear transducer. Sound is received by the microphone, amplified and transported as an electronic signal via the transducer to the middle ear. The transducer vibrates and delivers information to the incus. The charging set is used to recharge the implant battery across the patient’s skin. The Carina is indicated for adult patients with moderately severe-to-severe SNHL of 30–85 dB HL, especially in the high frequencies [5, 6] (fig. 2). Candidates should have tried conventional hearing aids to little or no success. Patients with recurrent outer ear canal infections, who cannot wear conventional hearing aids, may also be candidates for the Carina system. Exclusion criteria are a history of recurrent middle ear infections or a known middle ear malformation, inner ear disorders, retrocochlear or central hearing impairment. The Carina system can – due to the TÜV regulatory body in Germany – also be used in patients with conductive hearing loss and a mixed hearing loss.

The Esteem AMEI

The Esteem AMEI has the CE mark – as all the other available AMEI systems described above – and can, thus, be used in otosurgery. Candidates are patients with mild-to-severe SNHL of 35–85 dB HL. As with other AMEIs, conventional hearing aids should have been tried before surgery with little or no success. The system is totally implanted retroauricularly with two connecting wires that are placed in the middle ear. When the tympanic membrane moves in response to sound waves, the device senses tympanic membrane movement via one of the connecting wires and

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delivers energy to the cochlea with the second lead wire. Because tympanic membrane movement is connected to the implant, no microphone is necessary. Patient access to the implant is provided by a remote control device. An additional operation, after about 4 years, is needed to replace the internal battery. Because the implant connects to the ossicles and senses tympanic membrane movement, the candidate should not have had previous middle ear surgery, and unobstructed tympanic membrane and ossicular chain movement is required.

Conclusions

Active middle ear implants have provided an alternative to conventional hearing aids for hearing-impaired patients over the past decade. They are an option for patients who cannot be sufficiently rehabilitated with conventional hearing aids or surgical techniques such as tympanoplasty. The number of candidates for AMEIs is limited and patients should be selected carefully. Patients who are candidates are usually not satisfied with their hearing aids. The alternative treatment, the AMEI, usually results in good patient satisfaction. The new approach for the VSB provides new possibilities for patients with mixed hearing loss and previous middle ear surgeries. Especially for hearing losses with a 30- to 60dB HL sensorineural component and a 30- to 40-dB HL conductive hearing loss, it is now possible to offer a reliable treatment to patients who previously had no alternative to conventional hearing aids.

References 1 Gan RZ, Wood MW, Ball GR, Dietz TG, Dormer KJ: Implantable hearing device performance measured by laser Doppler interferometry. Ear Nose Throat J 1997; 76:297–299, 302, 305–309. 2 Snik A, Noten J, Cremers C: Gain and maximum output of two electromagnetic middle ear implants: are real ear measurements helpful? J Am Acad Audiol 2004; 15:pp 249–257. 3 Snik AF, Cremers CW: Vibrant semi-implantable hearing device with digital sound processing: effective gain and speech perception. Arch Otolaryngol Head Neck Surg 2001;127:1433–1437. 4 Sterkers O, Boucarra D, Labassi S, Bebear JP, Dubreuil C, Frachet B, Fraysse B, Lavieille JP, Magnan J, Martin C, Truy E, Uziel A, Vaneecloo FM: A middle ear implant, the Symphonix Vibrant Soundbridge: retrospective study of the first 125 patients implanted in France. Otol Neurotol 2003;24:427–436.

Indications and Candidacy for AMEIs

5 Jenkins HA, Niparko JK, Slattery WH, Neely JG, Fredrickson JM: Otologics Middle Ear Transducer Ossicular Stimulator: performance results with varying degrees of sensorineural hearing loss. Acta Otolaryngol 2004; 124:391–394. 6 Kasic JF, Fredrickson JM: The Otologics MET ossicular stimulator. Otolaryngol Clin North Am 2001;34:501–513. 7 Perkins R: Earlens tympanic contact transducer: a new method of sound transduction to the human ear. Otolaryngol Head Neck Surg 1996; 114: 720– 728. 8 Yanagihara N, Aritomo H, Yamanaka E, Gyo K: Implantable hearing aid: report of the first human applications. Arch Otolaryngol Head Neck Surg 1987;113:869–872.

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9 Maniglia AJ, Ko WH, Rosenbaum M, Zhu WL, Werning J, Belser R, Drago P, Falk T, Frenz W: A contactless electromagnetic implantable middle ear device for sensorineural hearing loss. Ear Nose Throat J 1994; 73:78–82, 84–88, 90. 10 Hough J, Vernon J, Johnson B, Dormer K, Himelick T: Experiences with implantable hearing devices and a presentation of a new device. Ann Otol Rhinol Laryngol 1986; 95: 60–65. 11 Fredrickson JM, Coticchia JM, Khosla S: Ongoing investigations into an implantable electromagnetic hearing aid for moderate to severe sensorineural hearing loss. Otolaryngol Clin North Am 1995; 28: 107–120. 12 Hausler R, Stieger C, Bernhard H, Kompis M: A novel implantable hearing system with direct acoustic cochlear stimulation. Audiol Neurootol 2008;13:247–256. 13 Colletti V, Soli SD, Carner M, Colletti L: Treatment of mixed hearing losses via implantation of a vibratory transducer on the round window. Int J Audiol 2006;45:600–608. 14 Tjellstrom A, Granstrom G: Long-term follow-up with the bone-anchored hearing aid: a review of the first 100 patients between 1977 and 1985. Ear Nose Throat J 1994; 73:112–114. 15 Niehaus HH, Helms J, Muller J: Are implantable hearing devices really necessary? Ear Nose Throat J 1995; 74:271–274, 276. 16 Todt I, Seidl RO, Gross M, Ernst A: Comparison of different Vibrant Soundbridge audioprocessors with conventional hearing AIDS. Otol Neurotol 2002;23:669–673. 17 Junker R, Gross M, Todt I, Ernst A: Functional gain of already implanted hearing devices in patients with sensorineural hearing loss of varied origin and extent: Berlin experience. Otol Neurotol 2002; 23: 452–456. 18 Wyatt JR, Niparko JK, Rothman M, deLissovoy G: Cost utility of the multichannel cochlear implants in 258 profoundly deaf individuals. Laryngoscope 1996;106:816–821. 19 Lamden KH, St Leger AS, Raveglia J: Hearing aids: value for money and health gain. J Public Health Med 1995;17:445–449.

20 Snik AF, van Duijnhoven NT, Mylanus EA, Cremers CW: Estimated cost-effectiveness of active middle-ear implantation in hearing-impaired patients with severe external otitis. Arch Otolaryngol Head Neck Surg 2006; 132:1210–1215. 21 Ball GR, Huber A, Goode RL: Scanning laser Doppler vibrometry of the middle ear ossicles. Ear Nose Throat J 1997; 76:213–218, 220, 222. 22 Tjellstrom A, Luetje CM, Hough JV, Arthur B, Hertzmann P, Katz B, Wallace P: Acute human trial of the floating mass transducer. Ear Nose Throat J 1997;76:204–206, 209–210. 23 Todt I, Seidl RO, Ernst A: Hearing benefit of patients after Vibrant Soundbridge implantation. ORL J Otorhinolaryngol Relat Spec 2005; 67: 203– 206. 24 Luetje CM, Brackman D, Balkany TJ, Maw J, Baker RS, Kelsall D, Backous D, Miyamoto R, Parisier S, Arts A: Phase III clinical trial results with the Vibrant Soundbridge implantable middle ear hearing device: a prospective controlled multicenter study. Otolaryngol Head Neck Surg 2002; 126:97–107. 25 Wever EG, Lawrence M: The transmission properties of the middle ear. 1950. Ann Otol Rhinol Laryngol 1992; 101:191–204. 26 Wollenberg B, Beltrame M, Schönweiler R, Gehrking E, Nitsch S, Steffen A, Frenzel H: Integration des aktiven Mittelohrimplantates in die plastische Ohrmuschelrekonstruktion. HNO 2007; 55: 349– 356. 27 Hohenhorst W: Classic reconstruction combined with Vibroplasty techniques focused on oval window. International Symposium: Vibroplasty Research, Military Hospital Ulm. September 22nd, 2007. 28 Dumon T: Vibrant Soundbridge middle ear implant in otosclerosis: technique – indication. Adv Otorhinolaryngol 2007; 65: 320–322. 29 Streitberger C: VSB applied to the oval window and in atresia. Advances in Vibroplasty. Berlin, Unfallkrankenhaus Berlin, 2008. 30 Hüttenbrink KB, Zahnert T, Bornitz M, Beutner D: TORP-vibroplasty: a new alternative for the chronically disabled middle ear. Otol Neurotol 2008; 29: 965–971.

Prof. A. Ernst Department of Otolaryngology at ukb Warener Strasse 7 DE–12683 Berlin (Germany) Tel. +49 30 5681 4301, Fax +49 30 5681 4303, E-Mail arneborg.ernst @ ukb.de  

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Böheim K (ed): Active Middle Ear Implants. Adv Otorhinolaryngol. Basel, Karger, 2010, vol 69, pp 27–31

Clinical Results with an Active Middle Ear Implant in the Oval Window K.B. Hüttenbrink a · D. Beutner a · T. Zahnert b a Department b Technical

of Otorhinolaryngology, Head and Neck Surgery, University of Cologne, Cologne, and University of Dresden, Dresden, Germany

Abstract Background: Some patients with chronic middle ear disease and multiple failed revisions, who also need a hearing aid, may benefit from an active middle ear implant. An advantage of an active middle ear implant is that the ear canal is unoccluded. Methods: Following extensive experimental development in temporal bones and investigations of various locations and attachments of a Vibrant Soundbridge transducer, a new titanium clip holder for the vibrant floating mass transducer was developed. This assembly is a total ossicular replacement prosthesis (TORP) that is placed on the stapes footplate. Six patients were implanted with this device. Results: Acoustic results demonstrate significantly improved gain, especially in the high frequencies, which is typically unobtainable by conventional hearing aids. Conclusion: The simple procedure of placing an active TORP assembly on the stapes footplate, similar to the implantation of a passive TORP prosthesis during tympanoplasty, offers promising treatment for cases of incurable middle ear disease. Copyright © 2010 S. Karger AG, Basel

Patients with a long history of chronic otitis media often need a hearing aid for communication. This is not only due to unsuccessful restoration of acoustic function of the middle ear despite several tympanoplasty attempts, but also to an often accompanying inner ear hearing loss. Use of a conventional hearing aid ear mold may be uncomfortable because of surgically modified external ear anatomy. After we developed a hydro-acoustic system that demonstrated the efficiency of direct vibratory stimulation of the inner ear via both round and oval windows [1], we tested the optimal placement of the commercially available Vibrant Soundbridge (VSB) (Vibrant MED-EL, Innsbruck, Austria) in temporal bone experiments. A titanium holder for the floating mass transducer (FMT) was developed in collaboration with the Kurz Company (Dusslingen, Germany). This total ossicular replacement prosthesis (TORP)-FMT assembly was implanted in 6 patients.

a

b

Fig. 1. a Intraoperative view of the assembly with the titanium holder and FMT in its clip, partly covered by the cartilage plate. b Schematic illustration of the TORP vibroplasty assembly in the oval window.

Methods Six patients were implanted, 3 female and 3 male (mean age 67.5 years, range 61–75). The 2 right and 4 left ears had a severely destroyed middle ear with a bare footplate as the sole ossicular remnant, some (4 patients) with a nonfunctional passive TORP lying in the cavity. All patients had bilateral radical cavities with permanent air-bone gaps between 30 and 50 dB and significant (50 dB) inner ear hearing losses. They did not tolerate conventional hearing aids. After cleaning the oval window niche of granulations and scar tissue, we conducted reconstruction surgery. First, we prepared of a full thickness (1-mm) cartilage shoe with a central hole that was placed in the oval window niche. The rod of our new titanium support was inserted into the central hole and was centered on the footplate. The transducer was inserted into the support by gently pressing it down and fixing it between three clips (fig. 1). The top of the assembly was covered by a cartilage plate – the reconstructed tympanic membrane. In prior radical cavity obliteration cases, the cable was directed out behind the cartilage plates of the partial obliteration to the receiver in its separate bed in the temporalis squama.

Results

Audiometric thresholds, measured 4 weeks after surgery and after removal of ear packing, showed unchanged cochlear function. Figure 2 presents unaided bone conduction thresholds. Unaided air conduction thresholds remained nearly unchanged except in 1 patient, in whom it improved by 20 dB because the inactive assembly works as a passive TORP. Despite increased mass load and friction in the cartilage shoe holder, the average air conduction thresholds in the passive mode were comparable with the situation prior to implantation.

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0

0.5

10 20

1

kHz 2

3

4 Functional vibrant Pre and postoperative BC Postoperative AC Preoperative AC

30

dB

40 50 60 70 80 90 100

Fig. 2. Pre- and postoperative hearing thresholds of the first 6 patients demonstrating good gain at the high frequencies.

When the VSB was turned on, we observed an improvement of 20 dB in aided soundfield thresholds for frequencies 2 through 4 kHz as compared with bone conduction thresholds (fig. 2). Good high-frequency gain supported an improvement of monosyllabic word discrimination scores from 0% in the unaided condition to 55% in the VSB-aided condition (average scores, presentation level: 65 dB, Freiburger monosyllabic word discrimination test). According to patients’ reports, the improved high-frequency audibility between 2 and 4 kHz was described as a more natural and very pleasant hearing sensation.

Discussion

Contrary to discussions on indications for implantable hearing aids in sensorineural hearing loss [2], their benefit in patients with permanently defect middle ear and unsatisfactory audiologic results with passive prostheses is demonstrated in an increasing number of successful implantations throughout the world [3–5]. The ear canal remains open, and the conductive component of the hearing loss is bypassed. Improvement in aided hearing thresholds, especially at high frequencies, is an important advantage. The alternative treatment, a bone-anchored hearing aid, is limited in cases of severe cochlear dysfunction because of limited amplification. For our patients, the surgical intervention was accepted because they had tolerated several revision tympanoplasties well in the past and had asked for additional revision tympanoplasty to improve their hearing.

Oval Window Placement

29

We analyzed the optimal position for the VSB FMT in the inner ear in our temporal bone experiments prior to clinical use [6]. Direct contact to the stapes footplate gives better performance, especially for high frequencies between 2 and 4 kHz because of the large vibrating area of the complete footplate. Furthermore, the surgical procedure for the placement on the footplate might be seen as less demanding compared to the round window niche placement. Insertion into the round window niche often requires drilling the bony overhang with the risk of cochlear trauma [7]. This is due to restrictions in the approach, anatomical variations, and the relatively large diameter of the FMT (1.6 mm) as compared to the opening of the round window niche (1.3–1.6 mm) [8, 9]. Furthermore, permanently stable contact with the inner ear fluid, while also avoiding any hard contact to the surrounding bone, is mandatory for efficient coupling. A loose contact between the FMT and the round window membrane/ cochlear fluid results in reduced amplification. Mechanical restriction might explain the variable acoustic results reported in the literature on the round window placement. In some cases, the aided thresholds did not surpass the bone conduction thresholds [10]. Inconsistent contact of the FMT is avoided when the FMT is placed in direct contact with the footplate. Due to limited space in the oval window niche, a titanium holder was required. Secure attachment to the stapes footplate, preventing any lateral displacement, is assured when our cartilage shoe technique for the passive TORP procedure is used [11]. The FMT is attached to the support by modifying the clip design of our Clip-partial ossicular replacement prosthesis (PORP) [12]. In cases of an intact stapes, two clips (one for the FMT and the other for the stapes head) form the PORP design. Therefore, by using the developments for passive prostheses and by closing the tympanic cavity with a thick cartilage plate, stable assembly anchorage to the footplate is established. Our first audiologic results support data gathered in our temporal bone experiments and demonstrate good acoustic benefit of directly coupling the FMT to the stapes footplate. Amplification of 40–60 dB in the high frequencies would not be possible with a conventional air conduction hearing aid. The surgical procedure, about as simple as the placement of a conventional TORP on the footplate, is another advantage over drilling the round window niche and the risk of inconsistent transducer placement in contact with the membrane. Because the TORP also provides hearing benefit when used passively, patients with a moderate hearing loss might use active stimulation only in noisy or demanding listening situations (e.g. parties). Therefore, this TORP- (or future PORP-) supported VSB assembly can be offered to a large group of patients with permanently damaged middle ear function and additional sensorineural hearing loss, who are not candidates for conventional hearing aids or bone-anchored hearing aids. A good hearing prognosis can be offered to these patients with a simple and modified ‘active tympanoplasty procedure’.

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References 1 Hüttenbrink KB: Biomechanical aspects in implantable microphones and hearing aids and development of a concept with a hydroacoustical transmission. Acta Otolarnygol 2001; 121:185–189. 2 Hüttenbrink KB: Current status and critical reflexions on implantable hearing aids. Am J Otol 1999; 20:409–415. 3 Coletti V, Soli SD, Carner M, Colletti L: Treatment of mixed hearing losses via implantation of a vibratory transducer on the round window. Int J Audiol 2006;45:600–608. 4 Kiefer J: Round Window Stimulation with an Implantable Hearing Aid Soundbridge쏐 combined with autogenous reconstruction of the auricle: a new approach. ORL 2006; 68:375–385. 5 Wollenberg B: Integration of the active middle ear implant in total auricular reconstruction (in German). HNO 2007; 55:349–356. 6 Hüttenbrink KB, Zahnert Th, Bornitz M, Beutner D: TORP-vibroplasty: a new alternative for the chronically disabled middle ear. Otol Neurotol 2008;29:965–971.

7 Pau HW, Just T, Bornitz M, Lasurashvilli M, Zahnert Th: Noise exposure of the inner ear during drilling a cochleostomy for cochlear implantation. Laryngoscope 2007; 117:535–540. 8 Nomura Y: Otological significances of the round window. Adv Otorhinolaryngol 1984; 33:11–99. 9 Roland MD: Cochlear implant electrode insertion: the round window revisited. Laryngoscope 2007; 117:1397–1402. 10 Soli S: Comparison of output levels and gains for bone conduction and round window stimulation of the cochlea in patients with conductive hearing loss. Proc 5th Int Symp on Human Sensibility Recovery Systems, Kyungpook National University Daegu, Korea, 2007. 11 Hüttenbrink KB, Zahnert T, Beutner D, Hofmann G: The cartilage guide: a solution for anchoring a columella prosthesis on footplate (in German). Laryngorhinootologie 2004; 83: 450–456. 12 Hüttenbrink KB, Zahnert Th, Wüstenberg E, Hofmann G: Titanium clip prosthesis. Otol Neurotol 2004;25:436–442.

Prof. Dr. K. B. Hüttenbrink HNO-Uniklinik Köln Kerpener Strasse 60 DE–50937 Köln (Germany) Tel. +49 221 478 4750, Fax +49 221 478 4793 E-Mail huettenbrink.k-b @ uni-koeln.de  

Oval Window Placement

 

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Experiments on the Coupling of an Active Middle Ear Implant to the Stapes Footplate T. Zahnert a · M. Bornitz a · K.B. Hüttenbrink b a Department b University

of Otorhinolaryngology, University Clinic of Dresden, Dresden, and Clinic of Cologne, Cologne, Germany

Abstract Background: Although the function of active middle ear implants in cases of intact ossicular chains and ventilated middle ears is well known, information about sound transfer function to the inner ear in cases of chronic middle ear effusion and defective middle ear structures is needed. A temporal bone model was developed to measure (1) the coupling of the active middle ear implant Vibrant Soundbridge in cases of nonventilated radical cavities, and (2) the effect of effusion and cartilage shielding. Methods: Three fresh human temporal bone specimens were studied. After preparation of a radical cavity, the floating mass transducer was coupled to the stapes footplate. The transducer was stimulated with 50 mV multisinus signals and inner ear fluid vibration was measured using a microphone in the round window niche. Several coupling conditions were simulated with mass and stiffness variations and cartilage shielding. Results: Coupling modality and prestress have the most influence on the sound transfer function to the inner ear. Cartilage shielding may ensure better coupling of the FMT to the footplate. The effect of middle ear effusion is negligible. Conclusion: The Vibrant Soundbridge provides good sound transfer to the inner ear not only in cases of coupling onto an intact ossicular chain in a ventilated middle ear but also in cases of coupling to the stapes Copyright © 2010 S. Karger AG, Basel footplate in non-ventilated radical cavities.

Passive middle ear implants provide good hearing results in middle ears that are normally ventilated with healthy tympanic membranes when there is no or only a moderate air-bone gap. Active middle ear implants (AMEIs) are traditionally indicated for persons with moderate-to-severe sensorineural hearing loss, an intact ossicular chain, and normal middle ear ventilation. The electromagnetic transducer of the Vibrant Soundbridge (VSB) has been successfully implanted and good hearing results in a large number of patients have been demonstrated, especially in the high-frequency

range [1]. However, nonventilated middle ears with mixed hearing loss, a frequently observed clinical situation, are problematic for hearing rehabilitation. There is no evidence so far that an AMEI such as the VSB is able to compensate for inner ear hearing loss when coupled to the oval window, when middle ear impedance, due to ventilation problems and chronic effusion, is increased. Because the stapes footplate is an often-used and reliable point to couple middle ear implants to, the present study focuses on placing the floating mass transducer (FMT) of the VSB in the oval niche in ears with radical cavities.

Material and Methods Experiments were performed on three fresh human temporal bones. First, the sound transfer function of the intact middle ear from the external auditory canal to the stapes footplate was measured using laser-Doppler vibrometry [2]. Second, the external and middle ear was removed and a radical cavity was created, using procedures similar to cholesteatoma surgery. The stapes suprastructure was separated from the footplate using a CO2 laser to prevent luxation of the annular ligament. The FMT was coupled to the stapes footplate using a modified TORP (total ossicular replacement prosthesis). The TORP provided a defined contact between the transducer and the footplate without contact to the facial nerve canal or the promontory. The prosthesis was further stabilized in a central position on the footplate by use of a cartilage shoe [3]. A standard FMT, excluding preprocessing electronics, was used in all FMT frequency transfer function measurements. The FMT was stimulated with a multisinus signal (50 mV rms, frequency range 0.2–7.6 kHz; one chirp per measurement frame, 20 averages). The stimulus signal covered the working range of the FMT. At 50 mV at 1 kHz, the FMT produced an equivalent sound pressure level of about 104 dB. Sound pressure measured at the round window niche (KE4 microphone, Sennheiser) served to assess the sound transferred to the inner ear (fig. 1). Sound pressure was also measured in the intact temporal bone specimen to provide a reference to calculate an equivalent sound pressure (at the tympanic membrane) generated by the VSB. Three coupling conditions were simulated: (1) cartilage shield on top of the FMT, no middle ear effusion; (2) cartilage shield on top of the FMT with additional middle ear eff usion; (3) cartilage shield on top of the FMT with additional prestress. The three coupling conditions were compared to the unrestrictedly placed FMT (without cartilage shield). Cartilage shield simulation was performed using a thick piece of concha cartilage (1 mm thickness) that was placed directly over the sound transducer with contact to the promontory and facial nerve canal (fig. 1). In order to simulate tension within the cartilage due to wound healing, the edges of the cartilage were attached at the promontory and at the facial canal with acrylate glue. Middle ear effusion was simulated using ultrasonic gel (TMP Tüshaus), which completely filled the oval niche (fig. 2). In the third experiment, prestress of the footplate via the FMTTORP was simulated by increasing the stress of the cartilage shield. The gradually stretched cartilage was fixed with acrylate glue before starting the measurements.

Oval Window Experiments

33

Cartilage shield

Floating mass transducer of the Vibrant Soundbridge

Prestress

Microphone at round window niche

Fig. 1. Schematic experimental set-up.

Fig. 2. FMT with TORP coupled to the stapes footplate. The FMT is covered by a cartilage shield and the oval niche is filled with gel.

Results

Experiment 1: Effect of Cartilage Shield Figure 3 presents the measurements with and without cartilage shielding. Improved sound transfer of 5–10 dB at low frequencies up to 400 Hz was observed in measurements using cartilage shielding. Without the cartilage shielding, coupling with clearance (between FMT and stapes footplate) may occur, which results in a sound transfer loss of 20–30 dB (fig. 4).

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130

FMT at stapes footplate Without covering Covered with cartilage

120

Equivalent SPL (dB)

110 100 90 80 70 60 50 40 100

1,000 Frequency (Hz)

10,000

Fig. 3. Generated equivalent sound pressure level for 50 mV FMT stimulation over the frequency range. FMT-TORP assembly at stapes footplate with and without cartilage shielding.

130

FMT at stapes footplate Covered with cartilage Coupling with clearance Coupling with prestress Prestress increased

120

Equivalent SPL (dB)

110 100 90 80 70 60 50 40 100

1,000 Frequency (Hz)

10,000

Fig. 4. Generated equivalent sound pressure level for 50 mV FMT stimulation over the frequency range. Transfer function of FMT-TORP assembly in the following conditions with cartilage shielding: no prestress, prestress, increased prestress due to increased tension of the cartilage, and coupling with clearance.

Experiment 2: Effect of Middle Ear Effusion The effect of middle ear effusion on the sound transfer function is demonstrated in figure 5. After filling the oval niche with ultrasonic gel, the transfer function was reduced by only 5–10 dB in the mid- and high-frequency range. There was no influence at low frequencies.

Oval Window Experiments

35

130

FMT at stapes footplate Without gel Oval niche filled with gel

120

Equivalent SPL (dB)

110 100 90 80 70 60 50 40 100

1,000 Frequency (Hz)

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Fig. 5. Generated equivalent sound pressure level for 50 mV FMT stimulation over the frequency range. Simulation of middle ear effusion by filling ultrasonic gel into the oval niche.

Experiment 3: Effect of Prestress Tension of the cartilage shield had the greatest impact on transducer performance. Figure 4 shows a reduction of the equivalent sound pressure level (generated by the FMT) with increasing stress at the cartilage piece. This effect was most prominent in the low- and mid-frequency range (up to 3 kHz) with up to 25 dB loss but was less prominent at higher frequencies.

Discussion

This study, using fresh human temporal bones, was designed to investigate the sound transfer function of the VSB in cases of nonventilated middle ears. The clinical situation is comparable to radical cavities after numerous surgical revisions and poor hearing outcomes, even when cholesteatoma eradication is successful and the tympanic membrane is closed. The temporal bone model with cartilage shielding was suitable to simulate this difficult clinical situation. In contrast to the temporal bone investigation by Huber et al. [4], the VSB was coupled to a TORP implant instead of to a PORP (partial ossicular replacement prosthesis). Furthermore, the FMT was shielded by a piece of cartilage and the effects of prestress variations and middle ear effusion were investigated. In order to ensure proper coupling of the FMT to the footplate, a cartilage shield was very useful in our experiments. When the FMT was placed without cartilage shielding, a transfer loss of about 20 dB was observed between the transducer and the footplate. This is comparable to experiments on passive implants in which loose coupling reduces sound transfer due to a loss of mechanical energy [5]. In contrast, pre-

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stress, due to increased tension in cartilage shielding, can reduce the generated equivalent sound pressure of the VSB by about 25 dB. This might be a result of increased annular ligament tension and transducer damping. A surprising finding was the small influence of fluid on the sound transfer function that was measured after filling the cavity with ultrasonic gel. It is well known from audiological measurements and experiments on temporal bones that middle ear effusion can lead to an air-bone gap of 30 dB. This effect in intact middle ears can be explained by a damping of the tympanic membrane. Due to the much higher mechanical power of the FMT and a direct coupling to the inner ear (via the stapes footplate), the effect of a middle ear effusion is negligible with the VSB.

Conclusions

• • • •

TORP vibroplasty with VSB is suitable for nonventilated radical cavities. Middle ear effusion reduces the FMT transfer function by only 5 dB. Cartilage shielding of the FMT without prestress stabilizes coupling to the footplate. Coupling and prestress have the biggest influence on FMT sound transfer.

References 1 Truy E, Philibert B, Vesson JF, Labassi S, Collet L: Vibrant Soundbridge versus conventional hearing aid in sensorineural high-frequency hearing loss: a prospective study. Otol Neurotol 2008; 29:684–687. 2 Hüttenbrink KB, Zahnert T, Bornitz M, Beutner D: TORP-vibroplasty: a new alternative for the chronically disabled middle ear. Otol Neurotol 2008; 29: 965–971. 3 Beutner D, Luers JC, Hüttenbrink KB: Cartilage ‘shoe’: a new technique for stabilisation of titanium total ossicular replacement prosthesis at centre of stapes footplate. J Laryngol Otol 2008;122:682–686.

4 Huber AM, Ball GR, Veraguth D, Dillier N, Bodmer D, Sequeira D: A new implantable middle ear hearing device for mixed hearing loss: a feasibility study in human temporal bones. Otol Neurotol 2006; 27: 1104–1109. 5 Zahnert T: Hearing disorder: surgical management. Laryngorhinootologie 2005; 84(suppl 1):S37–S50.

Prof. Dr. Th. Zahnert Universitäts-HNO-Klinik Dresden Fetscherstrasse 74 DE–01307 Dresden (Germany) Tel. +49 351 458 4420, Fax +49 351 458 4326 E-Mail orl @ uniklinikum-dresden.de  

 

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Böheim K (ed): Active Middle Ear Implants. Adv Otorhinolaryngol. Basel, Karger, 2010, vol 69, pp 38–50

The Vibrant Soundbridge for Conductive and Mixed Hearing Losses: European Multicenter Study Results W.-D. Baumgartner a · K. Böheim b · R. Hagen d · J. Müller d · T. Lenarz e · S. Reiss a · M. Schlögel b · R. Mlynski d · H. Mojallal e · V. Colletti f · J. Opie c a HNO

Universitätsklinik AKH Wien, Wien, b Landesklinikum St. Pölten, St. Pölten, c MED-EL Medical Electronics, Innsbruck , Österreich; dKlinik und Poliklinik für Hals-, Nasen- und Ohrenkrankheiten Universität Würzburg, Würzburg, eMedizinische Hochschule, Hannover, Deutschland; f Azienda Osepedaliera di Verona, Unità Operativa di Otorinolaringoiatria, Verona, Italia  

 

 

Abstract Background/Aims: The Vibrant Soundbridge (VSB) is an active middle ear implant, ‘direct-drive’ hearing system for the treatment of hearing loss. Recently, the VSB has been applied to conductive and mixed hearing losses. The aim of this study is to evaluate aided benefit, speech recognition in quiet and noise, subjective benefits, changes in residual hearing, and medical and surgical complications in adults with conductive or mixed hearing losses implanted with the VSB using Round Window (RW) Vibroplasty TM . Methods: Twelve German-speaking adults participated in a single-subject, repeated measures study design comparing their performance using the VSB with their own unaided preoperative performance. Hearing performance and changes in residual hearing were assessed using routine audiometric measures, sound field thresholds, and word and sentence recognition in quiet and in noise. Subjective benefits, including subjective hearing performance, device satisfaction, and quality of life were evaluated using the Abbreviated Profile of Hearing Aid Benefit, the Hearing Device Satisfaction Scale, and the Glasgow Benefit Inventory, respectively. Results: Aided hearing thresholds, word recognition at conversational levels, and sentence recognition in quiet and noise were significantly improved without significant changes in residual cochlear hearing and without major medical and surgical complications. One subject required repositioning surgery to improve transducer coupling with the RW membrane. Subjective benefit and device satisfaction were good, as were overall and general quality of life. Conclusion: The VSB, implanted using RW vibroplasty, is a safe and effective treatment for adults with conductive and mixed hearing lossCopyright © 2010 S. Karger AG, Basel es who may have few, if any, other options.

The Vibrant Soundbridge (VSB) is an active middle ear implant (AMEI) for the treatment of hearing loss. Since 1996, the VSB has been implanted in adults with mild-tosevere sensorineural hearing loss. It is for persons who cannot wear conventional acoustic hearing aids for medical reasons and those who are unsuccessful or dissatisfied with their hearing aids. In 2007, the indications for the VSB were extended to include persons with conductive and mixed hearing losses. In those patients, the transducer of the VSB, the floating mass transducer (FMT), is placed in the round window niche bypassing the disordered outer and/or middle ear. Vibrational energy from the FMT is transferred to the round window to stimulate inner ear hearing. The surgical procedure to place the FMT in the round window niche is called Round Window (RW) VibroplastyTM . Conductive and mixed hearing losses typically result from pathologies such as acute and chronic otitis media, cholesteatoma, otitis externa, congenital atresia, otosclerosis, tympanosclerosis, and stenosis of the ear canal. A number of medical and surgical treatment options exist to stabilize the ear and improve hearing. Which is used depends on the severity of the pathology, prognosis for improvement, and hearing status. In mild cases with a good prognosis for quick recovery, medications or simple surgical procedures may be sufficient. In severe cases, more aggressive treatments are needed. If the disease process affects the outer or middle ear structures, perhaps even causing degeneration of the ossicular chain or tympanic membrane, then reconstructive surgery is used to restore the conductive pathway. Various surgical techniques may be applied, possibly including passive prostheses. Often, medical and surgical treatments stabilize the ear and restore hearing function. However, in many cases post-treatment hearing impairment remains. Pathologies of the outer and middle ears may recur, compromising the integrity of the surgical procedure and causing hearing loss. A review of 197 reconstructive surgery cases in the ORL Clinic of the Kantonsspital Zürich revealed that, although results were good in patients with less involved reconstructive surgeries, satisfactory results were obtained in only 50% of patients who underwent more complicated procedures [1]. Long-term results may be poor with postoperative air-bone gaps of less than 30 dB occurring in only about 40–70% of the cases [2]. When hearing is not sufficiently restored to support good communication, a hearing device is indicated. The choice of hearing device depends on the degree of hearing loss and the medical status of the outer and middle ears. Small hearing aids, worn either in or behind the ear, are generally successful for mild and moderate hearing losses. For more severe degrees of hearing loss, even the strongest behind-the-ear hearing aid may not be sufficient. Hearing aids may be particularly limited for mixed hearing losses because they are incapable of delivering sufficient gain and output to overcome the conductive component and amplify sound to the inner ear. Hearing aids of any type that are placed fully or partially in the ear canal may be medically precluded in conditions, such as otitis externa, that affect the external ear canal. Ear canal occlusion may exacerbate some medical conditions, especially otitis media, leading to drainage of the ear, possibly suspending hearing aid use.

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Bone conduction (BC) and bone-anchored hearing aids may be used in conductive and mixed hearing losses. BC hearing aids may provide good hearing augmentation, but their use is complicated by the necessity of consistent placement and sufficient pressure to ensure good coupling between the bone vibrator and the skull. Sound quality may not be optimal, and, when used in young children with soft skulls, pressure from the vibrator may cause a slight skull deformation. The bone-anchored hearing aid (BAHA) is an alternative BC hearing aid for conductive and mixed hearing losses [3]. The BAHA uses an electrodynamic transducer, an osseointegrated titanium screw implanted in the skull, coupled with an external processor via a percutaneous pedestal. Although clinical results are favorable, complications have been reported. These include the need for revision surgery and fixture loss. Common reasons for failure have been head trauma and loss of osseointegration. Skin reactions, including infections, have also complicated use of the BAHA [4]. AMEIs are another treatment option for conductive and mixed hearing losses. The technology for AMEIs first became possible in the 1970s when miniaturization of electronic components, availability of robust biocompatible materials, and improvements in battery technology contributed to the design of small hearing devices, capable of being implanted chronically in the human body. In addition, refinements in auditory brainstem response techniques allowed the responsiveness of the auditory system to mechanical stimulation to be confirmed in preclinical animal studies prior to human clinical use. AMEIs use either piezoelectric or electromagnetic transducers to deliver vibrational energy to the middle ear. The earliest AMEI was available in partially and fully implantable versions and used a piezoelectric transducer attached to the stapes [5]. The device benefited patients, but technical difficulties attributed to piezoelectric technology, including device failure, hermeticity, and limited output occurred. Other AMEIs used electromagnetic transducers. Goode described an AMEI using a magnet implanted on a middle ear structure and driven by an externally worn coil, located either in the ear canal or behind the ear, to induce vibration of an internal magnet [6]. Another device, the EarLens from ReSound, used a small magnet placed on the tympanic membrane with a driver worn around the neck, which was both heavy and prone to picking up clothing noise. One unique AMEI used electromagnetic transduction to drive a magnetic partial or total passive prosthesis used to reconstruct the ossicular chain [7]. When the magnetic prosthesis was stable and the driver was in good proximity to the prosthesis, aided thresholds were good. However, placing the driver close to the tympanic membrane, using a very deep canal fitting, was necessary but particularly problematic in ear canals deformed by previous ear surgery [8]. Early AMEIs established the viability of mechanical stimulation of the middle ear to evoke a sensation of hearing and treat hearing loss. However, their success was limited because of problems either with the durability of piezoelectric materials or with power losses associated with drivers remote from electromagnetic transducers.

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The more recently developed VSB solves many of the problems experienced with previous AMEIs by using an electromagnetic transducer in very close proximity to a driving coil. The two are incorporated in the FMT, making it a very robust and power-efficient transducer. Because of its single-point attachment clip, the FMT can be placed on any of a number of middle ear structures. This is particularly useful in conductive and mixed hearing losses in which middle ear anatomy is abnormal and varies considerably from individual to individual. Flexibility in device attachment means that the FMT can be adapted to the particular needs of each ear. Further, because the VSB uses transcutaneous transmission, problems associated with percutaneous pedestals are avoided. When used to treat sensorineural hearing losses, the FMT is placed on the incus so that the natural movement of the ossicular chain is augmented and sound is amplified. When used to treat conductive and mixed hearing losses, the FMT is typically placed on the reconstructed ossicular chain, on remaining stapes suprastructure or stapes footplate, or in the RW niche (RW vibroplasty). Vibrational energy stimulates residual hearing either with (mixed hearing losses) or without (conductive hearing losses) amplification. RW vibroplasty was studied by Colletti et al. [9] in 7 patients with failed ossiculoplasties and either a conductive or mixed hearing loss (normal to moderately-severely impaired sensorineural hearing). For most subjects, postoperative aided thresholds were 20–30 dB HL, aided speech reception thresholds were 50 dB SPL, and speech intelligibility at conversational levels was 100%. No medical or surgical complications were reported. These early results suggest that the VSB provides good speech recognition at conversational levels and aided thresholds within the expected range for modern amplification systems. The purpose of the present research is to extend previous research to evaluate aided benefit, speech recognition in quiet and noise, subjective benefits, quality of life (QoL), changes in residual hearing, and medical and surgical complications in adults with conductive and mixed hearing losses implanted with the VSB AMEI using RW vibroplasty.

Materials and Methods Subjects Fourteen German-speaking, healthy adult volunteers with conductive or mixed hearing loss were enrolled in the study. One subject died before the first fitting of the audio processor for reasons unrelated to implantation or device use and one was lost to follow-up. The remaining 12 subjects were 5 females and 7 males ranging in age from 31 to 73 years [mean = 51 (SD = 13) years]. Mean preoperative air and BC thresholds for the implanted ear are presented in figure 1a. Etiology of hearing loss included chronic otitis media (3 subjects), cholesteatoma (6 subjects), tympanosclerosis (2 subjects), and unknown reasons (1 subject). The VSB Vibrating Ossicular Prosthesis Model 502 was the AMEI implanted in 9 right and 3 left ears. The investigational plan was approved by local ethics committees, and all subjects signed an information and informed consent document upon enrolment. Subjects were not remunerated or otherwise compensated for their study participation.

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Subject Recruitment and Inclusion Criteria Subjects were recruited from and implanted at ENT clinics in Austria (HNO Universitätsklinik AKH Wien, Landesklinikum St. Pölten) and Germany (Medizinische Hochschule Hannover, Klinik und Poliklinik für Hals-, Nasen- und Ohrenkrankheiten Universität Würzburg). Inclusion criteria specified that subjects have conductive or mixed hearing loss and maximum BC thresholds of 45 dB HL at 500 Hz, 50 dB HL at 1,000 Hz, 55 dB HL at 1,500 Hz, 65 dB HL at 2,000 Hz, and 65 dB HL at 3,000 Hz. Furthermore, subjects were selected to have stable BC thresholds over the previous 12 months, good potential for aided speech recognition, a hearing aid trial within the previous 36 months, and no evidence of retrocochlear or central auditory pathology. Study Design and Statistical Analyses Each subject served as his/her own control in a prospective, single-subject repeated-measures study design. Paired, two-tailed repeated measures t tests were used to test for significant differences at the 0.05 level on pre- and postoperative BC thresholds, sound field thresholds, monosyllabic word recognition, and speech recognition thresholds for 50% correct recognition (SRT50) of words in sentences in quiet and noise. The 3-month postfitting interval was the study endpoint used in statistical analyses. RW Vibroplasty Many of the RW vibroplasty techniques were identical to those for incus vibroplasty [10]: surgical preparation, incision, mastoid drill out, preparation of the device seat and tie-down holes, facial recess and transmeatal routes to the middle ear, fixation of the demodulator, and surgical closure. However, the techniques to place the FMT on the RW were different. A 1.0- to 1.3-mm diamond burr, revolving at a slow speed, was used to enlarge the RW niche, moving from the anterior to the superior section. The fit of the FMT in the RW niche was evaluated. If the FMT could be positioned without obstruction from bone or protuberances, then a 2-mm diameter and 0.1- to 0.2mm thick fascia (or perichondrium or artificial fascia) disk was positioned over the RW membrane. The FMT attachment clip was either removed or bent back over the FMT before the long axis of the FMT was placed perpendicularly with its medial face on top of the fascia at the RW membrane. A second fascia disk was placed on the lateral face of the FMT. Free movement of the FMT was confirmed after each step of its placement. The conductor link was then positioned in the mastoid cavity under the overhangs of the inferior and superior wall without sharp bends but with some slack. Before closure, the position and free movement of the FMT were again evaluated. Surgeons were trained on the surgical procedures via discussion, observation, and practice in a temporal bone laboratory. However, the surgeons had little to no human clinical experience with RW vibroplasty prior to this study. Evaluation Protocol Routine audiometric testing, including air conduction (250 through 8,000 Hz) and BC (250 through 4,000 Hz) thresholds and word recognition testing under headphones, was conducted in audiometric test chambers, using clinical audiometers, and standard audiometric procedures. Unaided and aided warble tone (WT) thresholds (250 through 8,000 Hz) and speech understanding were measured in the sound field with the subject seated at 0° azimuth and 1 m in front of a loudspeaker. The contralateral ear was either plugged or masked, as needed, to eliminate it from testing. Percent correct word recognition ability was evaluated using the Freiburger monosyllabic word test [11] presented at 65 dB SPL (A). Sentence recognition in quiet and noise was evaluated using the Oldenburg Satztest (OLSA) by adaptively varying the presentation level to estimate the SRT50. For testing in noise, OLSA noise was presented at 60 dB SPL (A) and the level of the speech was adapted to obtain a signal-to-noise ratio (SNR) for 50% recognition of words in sentences. OLSA noise is matched to the long-term running average spectrum of the OLSA sentences [12].

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Questionnaires were administered to measure subjective benefit. The Abbreviated Profile of Hearing Aid Benefit (APHAB) [13] was used to assess hearing performance, the Hearing Device Satisfaction Scale (HDSS) [14] to assess device satisfaction, and the Glasgow Benefit Inventory (GBI) [15] to assess changes in QoL attributed to VSB use. The APHAB and the HDSS were administered both pre- and postoperatively and the GBI postoperatively only. Medical and surgical complications were monitored via regular ENT evaluations, which were summarized on written report forms. Postoperative device fitting and assessments occurred 6–8 weeks postsurgery and after 1 and 3 months of device use. Audio Processor Programming Programming of the externally worn Audio Processor Model 404, containing a Siemens digital hearing aid microchip, was carried out using Connexx 4.4 and Symfit 3.0 software. BC thresholds and uncomfortable listening levels were used to calculate initial DSL I/O (modified for VSB programming) settings. Adjustments to gain, output and compression were made based on subjects’ feedback during routine evaluation intervals or sooner, as needed.

Results

Aided Benefit Aided benefit was evaluated by comparing aided with unaided WT thresholds obtained in the sound field at the 3-month postfitting interval. Figure 1b presents mean thresholds for the 12 subjects and shows that aided thresholds were between about 20 and 40 dB HL in the speech frequency range. The observed improvement was significant at all frequencies (p ! 0.001). Mean functional gain, the difference between unaided and aided WT thresholds, is depicted in figure 1c and shows that functional gain varied from about 15 to about 43 dB HL with maximum mean functional gain in the frequency range 1,500–4,000 Hz. Speech Recognition in Quiet and Noise Word recognition was significantly improved as reflected by a change in mean percent correct Freiburger monosyllables from 6% (SD = 16) preoperatively to 67% (SD = 36) postoperatively (p ! 0.001). Figure 2a presents individual subjects’ pre- and

Fig. 2. a Pre- and postoperative word recognition scores (% correct) for Freiburger monosyllables presented at 65 dB SPL (A) in quiet. b Pre- and postoperative speech recognition thresholds in dB SPL (A) for 50% correct recognition of words in sentences. Lower thresholds represent better performance. When preoperative data bars are not present, it is because subjects were unable to complete the task, and the data are labeled as ‘could not test’ (CNT). c Pre- and postoperative SNRs in dB SPL (A) for 50% correct recognition of words in sentences in a background of speech (OLSA) shaped noise presented at 60 dB SPL (A). Smaller, more negative numbers reflect better performance. Subjects were 12 adults with conductive or mixed hearing loss. The FMT of subject 3 was not properly in place in the RW niche at the time of data collection; however, the FMT was later repositioned and performance reportedly improved.

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postoperative data and shows that 11 of 12 subjects were unable to score above 0% preoperatively whereas almost all were able to score better than 0% postoperatively aided with the VSB, with the majority of subjects scoring better than 70% correct. Sentence recognition in quiet showed an improvement in OLSA thresholds for 50% correct recognition from 68 dB SPL (SD = 6) preoperatively to 51 dB SPL (SD = 9) postoperatively. Figure 2b presents individual results and shows that SRT50 ranged from about 38 to 68 dB SPL postoperatively for all subjects, although 5 subjects were unable to complete the test preoperatively. Sentence recognition in noise (mean OLSA SNRs for 50% correct recognition presented in background noise) improved from +12 dB SPL SNR (SD = 8) preoperatively to 3 dB SPL SNR (SD = 5) postoperatively (fig. 2c). Subjective Benefits Significant changes in self-reported hearing performance from the unaided to the VSB-aided condition were observed as reductions in the percentage of problems on ease of communication (mean pre- to postoperative 66 to 28%, p = 0.001), Reverberation (mean pre- to postoperative 72 to 43%, p = 0.005), and background noise (mean pre- to postoperative 73 to 40%, p = 0.002) subscales of the APHAB. The aversiveness subscale showed no significant change (mean pre- to postoperative 30 to 35%, p 1 0.05). Significant improvement in overall device satisfaction was demonstrated in a mean improvement from 43% (SD = 28.7) preoperatively to 74% (SD = 18.5) postoperatively (p = 0.005) on the HDSS. Changes in QoL attributed to VSB use were observed in the areas of overall benefit and general benefit, which showed average positive changes of 17 and 24, respectively. The areas of social benefit and physical benefit showed much less change, changing an average of –6 and 11, respectively. Changes in Residual Hearing Changes in unaided hearing were evaluated by comparing preoperative unaided BC hearing thresholds with postoperative BC thresholds for audiometric test frequencies 500 through 4,000 Hz. There were no significant changes at any frequency (p 1 0.05). Air conduction thresholds were also unchanged (p 1 0.05). Figure 1a presents mean pre- and postoperative air and BC thresholds. Medical and Surgical Complications One subject (No. 3) required surgery to improve coupling between the FMT and the RW membrane. The subject initially experienced device benefit but performance declined rapidly following initial device fitting. Surgery for repositioning took place after the subject concluded study participation and data included here were collected before the second surgery (e.g. the subject’s data, reflecting poorer performance, are included). Audiologic performance and hearing benefit were reportedly good following the repositioning surgery. No other major medical or surgical complications were reported.

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Discussion

The principle findings of this study suggest that the VSB is safe and effective for subjects with conductive and mixed hearing losses implanted with RW vibroplasty. Specifically, subjects enjoy improved hearing performance and subjective benefit without significant changes in residual hearing or major medical or surgical complications. This is evident from data obtained from aided thresholds, functional gain measures, word recognition ability at conversational speech levels, and recognition of words in sentences in quiet and in noise. Subjective benefit measures supported these findings and showed that subjects perceived improved hearing ability in a variety of listening situations, were satisfied with the VSB, and enjoyed overall improved QoL. Hearing performance measures were used to evaluate efficacy. First, measures of aided benefit showed that good audibility was achieved, evident from mean aided thresholds of about 20–45 in the speech frequency range and mean functional gain of 15 dB at 250 Hz up to about 40 dB in the frequencies 1.5–4 kHz. These values agree with functional gain and amplification recommendations to achieve good speech recognition performance even in the presence of background noise [16]. It is important to consider that functional gain is dependent on the fitting parameters used to program the device, as well on the hearing requirements of the individual listener. This study is also in good agreement with previous VSB data from 53 subjects with sensorineural hearing loss in whom the FMT was placed on the ossicular chain [14]. Aided benefit measures support efficacy. The second set of measures used to evaluate efficacy includes speech recognition in quiet and noise. Word recognition improved from a mean of 2% preoperatively to 67% postoperatively. After 3 months of device use, 8 of 12 subjects scored 70% or better, although 10 of 12 scored 0% preoperatively. In terms of day-to-day life, the differences observed represent the difference between not being able to engage in everyday conversation and being able to do so successfully. The results are in good agreement with data for 53 subjects with sensorineural hearing loss using the VSB [14], as well as with data for subjects with mixed hearing loss [9, 17, 18]. Speech recognition thresholds in quiet, averaging 51 dB SPL, were also improved and are consistent with previous reports [19]. Finally, speech recognition in noise, assessed by the SNR required for 50% correct recognition of words in sentences presented in background noise, improved from a mean of +11.6 dB SNR preoperatively to +3 dB SNR postoperatively. This test is a very difficult test and small changes in dB SNR are representative of large changes in performance. Indeed, normal hearing subject data on the OLSA show that the slope of the performance-intensity function in the linear part of the curve is very steep and averages 17%/dB [20]. A comparison of the present data with normative data provided by the test manufacturer suggests that normal hearing subjects score an average of –7.1 dB SNR, which is better than observed here. However, as compared with subjects with mild-to-moderate sensorineural hearing loss wearing hearing aids, the present data are consistent with their performance reported to range from –3 to +10 dB SNR [21].

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That SNRs observed here were not better may also be explained by the background noise level used in this study; a 60-dB SPL noise level means that, in order to achieve SNRs of –5 dB or less, the speech level would have been presented at 55 dB or less. Therefore, the range between minimum and maximum performance may have been too limited to more accurately assess performance. Future research should include additional conditions to evaluate these effects. Nonetheless, improvements from pre- to postoperative conditions suggest that VSB use made communication in noisy backgrounds possible for subjects who would have experienced much difficulty without the device. Because speech recognition in noise is representative of real-world performance, these results are particularly encouraging and important for patients. Taken together, speech recognition measures support the efficacy of the VSB. Subjective benefit was improved as measured by self-report questionnaires. Subjective aided benefit in a variety of everyday listening situations was good as suggested by APHAB results on ease of communication, reverberation and background noise subscales. Only the aversiveness subscale score was not significantly better postoperatively. The lack of significant improvement on the aversiveness subscale is, perhaps, not surprising because, preoperatively, subjects did not report many problems on that subscale; therefore a ceiling effect existed. The results are in good agreement for 53 VSB subjects with sensorineural hearing loss [14] and suggest that subjects perceived aided benefit in their daily lives. Furthermore, they were satisfied with their devices, as suggested by their reports on the HDSS. Improved QoL was measured with the GBI, which measures changes in health status produced by a surgical treatment. Health status refers to a patient’s general self-reported well-being and includes questions on areas of psychological, social, and physical well-being. Subjects reported large changes in general and overall benefit but only small changes in the areas of physical and social benefit. These findings are not surprising, given the nature of the questions. A typical general benefit question is ‘Since your operation, do you have more or less self-confidence?’ In contrast, a typical physical benefit question is ‘Since your operation, do you catch colds or infections more or less often?’ Better hearing provided by the VSB should yield greater self-confidence in daily life but may not influence the frequency of illnesses. Scores of 17 in general benefit and 24 overall (across all areas) represent a good outcome, suggesting that subjects’ QoL improved. The scores are similar to those reported for middle ear surgery [21]. Subjective benefits are consistent with hearing performance results supporting VSB efficacy in the study population. Safety was evaluated by examining hearing thresholds and reports of medical and surgical complications. Comparisons of pre- and postoperative air- and bone-conduction thresholds showed that hearing was unchanged by VSB implantation. Similar findings are reported in the literature [22]. No medical complications and one surgical complication were reported. Specifically, the FMT migrated from its initial position in the round window niche, requiring surgery to reposition the device. This complication has also been reported in a few cases in the literature [23]. Repositioning surgery is relatively easy and may be accomplished by accessing the middle ear using

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a transcanal approach, potentially under local anesthesia. Taken together, the findings suggest that RW vibroplasty is safe with a relatively low medical and surgical complication rate. Although the results reported here are for a relatively small number of subjects who were followed for a relatively short amount of time, the present results extend and agree with previous research. A review of the recent literature on AMEIs for conductive and mixed hearing losses showed similar performance results and medical and complication rates for more than 100 ears, some with more than 12 months of device experience. Nonetheless, it is possible that the short duration of implant use influenced some subjects and that, with more device experience, subjects would have improved. Because data are not available for more than 3 months of device experience, it is not possible to answer that question definitively. However, anecdotal reports from the investigational centers suggest that additional experience may be needed to reach best performance. Future research should include data collection through at least 6 months of implant use. There are two primary implications of the current findings for clinicians. First, establishment of the safety and efficacy of the VSB means that clinicians have a viable treatment option for adults with conductive and mixed hearing losses who may have few, if any, alternatives to improve their functional hearing and communication abilities. Patients suffering from pathologies such as chronic otitis media, cholesteatoma, otitis externa, congenital atresia, otosclerosis, and stenosis of the ear canal have been limited in acoustic amplification benefit or have been unable to wear hearing aids at all. Many have undergone multiple surgeries to improve their middle ear function, often without adequate hearing improvement. Surgeons may decide on RW vibroplasty as a first step in these cases, thereby avoiding repetitive surgeries and sparing patients time lost from work. A second implication of this research is that safety and efficacy of RW vibroplasty for adults allows us to consider its use in children and adolescents. RW vibroplasty may be particularly helpful in cases of congenital middle ear malformations and auditory canal atresia. Initial experience reported in the literature suggests that a combination of RW vibroplasty and facial plastic surgery allows surgeons to treat both cosmetic and functional aspects without complicated reconstructive surgery [24]. Future research is needed to evaluate safety and efficacy in the pediatric population. In conclusion, the findings of this study suggest that the VSB, implanted using RW vibroplasty is a safe and efficacious treatment for adults with conductive and mixed hearing losses. By bypassing disordered parts of the middle and outer ears, the electromagnetic FMT provides vibrational energy to the inner ear either with or without amplification, depending on whether bone conductive thresholds are normal (conductive hearing loss) or impaired (mixed hearing loss). The amount of stimulation is sufficient to improve hearing performance and speech recognition to support everyday communication in a variety of listening situations without risk to residual hearing and with few medical and surgical complications.

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References 1 Fisch U: Reconstruction of the ossicular chain. HNO 1978;26:53–56. 2 Colletti V, Fiorino F, Sittoni V: Minisculpted ossicle grafts versus implants: long-term results. Am J Otol 1987;8:553–559. 3 Tjellström A, Haakansson B: The bone-anchored hearing aid: design principles, indications, and long-term clinical results; in Maniglia AJ (ed): Otolaryngologic Clinics of North America. Philadelphia, Saunders, 1995, vol 28, pp 53–72. 4 Lloyd S, Almeyda J, Srimann KS, Albert DM, Bailey CM: Updated experience with bone-anchored hearing aids in children. J Laryngol Otol 2007; 121: 826–831. 5 Suzuki J-I, Yanagihara N, Toriyama M, Sakabe N: Principle, construction, and indication of the middle ear implant; in Suzuki I-J, Hoke M (eds): Middle Ear Implant: Implantable Hearing Aids. Basel, Karger, 1988, pp 15–21. 6 Goode RL: Electromagenetic implantable hearing aids; in Suzuki I-J, Hoke M (eds): Middle Ear Implant: Implantable Hearing Aids. Basel, Karger, 1988, pp 22–31. 7 Heide H, Tatge G, Sander T, Gooch R, Prescott T: Development of a semi-implantable hearing device; in Suzuki I-J, Hoke M (eds): Middle Ear Implant: Implantable Hearing Aids. Basel, Karger, 1988, pp 32–43. 8 Tos M, Salomon G, Bonding P: Implantation of electro-magnetic ossicular replacement device. Ear Nose Throat J 1994;73:92–103. 9 Colletti V, Soli SD, Carner M, Colletti L: Treatment of mixed hearing losses via implantation of a vibratory transducer on the round window. Int J Audiol 2006;45:600–608. 10 Vibrant Soundbridge: Surgical Guide. Innsbruck, Vibrant MED-EL Hearing Technology GmbH, 2007. 11 Hahlbrock K-H: Sprachaudiometrie, ed 2. Stuttgart, Thieme, 1970. 12 Wagener K, Kühnel V, Kollmeier B: Entwicklung und Evaluation eines Satztests für die deutsche Sprache. I. Design des Oldenburger Satztests. Z Audiol 1999; 1:4–15.

13 Cox RM, Alexander GC: The abbreviated profile of hearing aid benefit (APHAB). Ear Hear 1995; 16: 176–186. 14 Luetje CM, Brackman D, Balkany TJ, Maw J, Baker RS, Kelsall D, Backous D, Miyamoto R, Pariser S, Arts A: Phase III clinical trial results with the Vibrant Soundbridge implantable middle ear hearing device: a prospective controlled multi-center study. Otolaryngol Head Neck Surg 2002; 126:97–107. 15 Gatehouse S: A self-report outcome measure for the evaluation of hearing-aid fittings and services. Health Bull 1999;57:424–436. 16 Killion MC, Fikret-Pasa S: The 3 types of sensorineural hearing loss: Loundess and intelligibility considerations. Hear J 1993; 46:1–4. 17 Streitberger C: New surgical techniques for Vibrant SB in mixed hearing loss. 8th Eur Symp Pediatr Cochlear Implantation, Venice, 2006. 18 Wollenberg B, Beltrame M, Schönweiler R, Gehrking E, Nitch S, Steffen A Frenzl H: Integration des aktiven Mittelohrimplantates in die plastische Ohrmuschelrekonstruktion. HNO 2007;5: 349–356. 19 Lavieille J-P, Deveze A, Venail F, Meller R, Magnan J: Positive results of middle ear implants in mixed hearing loss after failure in otosclerosis surgery of tympanoplasty. 10th Int Conf Cochlear Implants and Other Implantable Auditory Technologies, San Diego, 2008. 20 Oldenburger Satztest: User Manual. Oldenburg, HörTech GmbH, 2006. 21 Stephan K, Welzl-Müller K: Oldenburger Satztest: Verwendung zur Erfolgskontrolle nach Versorgung mit Hörgeräten. DGA Jahrestagung 2004, pp 1–2. 22 Robinson K, Gatehouse S, Browning GG: Measuring patient benefit from otorhinological surgery and therapy. Ann Otol Rhinol Laryngol 1996; 105: 415–422. 23 Godey B, Lavielle J-P, Gamby, R, Lefevre F: Vibrant Soundbridge in mixed hearing loss: comparison with BAHA and conventional hearing aid. 10th Int Conf Cochlear Implants and Other Implantable Auditory Technologies, San Diego, 2008. 24 Kiefer J, Arnold W, and Staudenmaier R: Round window stimulation with an implantable hearing aid (Soundbridge쏐) combined with autogenous reconstruction of the auricle: a new approach. ORL 2006;68:378–385.

Jane M. Opie, PhD MED-EL, Worldwide Headquarters Fürstenweg 77a AT–6020 Innsbruck (Austria) Tel. +43 512 28 88 89 257, Fax +43 512 28 88 89 595, E-Mail jane.opie @ medel.com  

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Böheim K (ed): Active Middle Ear Implants. Adv Otorhinolaryngol. Basel, Karger, 2010, vol 69, pp 51–58

Clinical Experience with the Active Middle Ear Implant Vibrant Soundbridge in Sensorineural Hearing Loss S.M. Pok · M. Schlögel · K. Böheim Department of Otorhinolaryngology, Head and Neck Surgery, Landesklinikum St. Pölten, St. Pölten, Österreich

Abstract Background/Aims: To evaluate gain at threshold level and speech recognition performance of 54 subjects with mild-to-severe symmetrical sensorineural hearing loss (SNHL) that received the active middle ear implant system Vibrant Soundbridge (VSB). Methods: Pre- and postoperative assessments of hearing thresholds and monosyllabic word discrimination were performed in a homogeneous group of 54 adults who received a VSB system (VORP 502/AP 404) in an active middle ear implant (AMEI) program in a tertiary referral hospital. All subjects included in this study had mildto-severe, predominately sloping SNHL. Gain at threshold level and speech recognition results were assessed for unaided and aided conditions using the patient’s walk-in hearing aid (HA) and the VSB in a retrospective study design. Results: A comparison of pre- and postoperative unaided air conduction thresholds revealed a mean decrease in pure tone averages of 3.9 dB (0.25–8 kHz). Gain at threshold level (unaided thresholds minus AMEI-aided thresholds) was, on average, 20.9 dB at 0.5 kHz, 20.5 dB at 1 kHz, 23.8 dB at 2 kHz, 30.2 dB at 3 kHz, 36.1 dB at 4 kHz, 37.6 dB at 6 kHz and 37.9 dB at 8 kHz. Monosyllabic word discrimination at 65 dB SPL improved from a mean of 30% in the unaided condition to 44% for the HA-aided condition (p ! 0.05), with a further increase to 57% for the VSB-aided condition (p ! 0.05, compared to the HA). Conclusion: The AMEI system VSB can be considered as an effective rehabilitation alternative in subjects with mild-to-severe SNHL and unsatisCopyright © 2010 S. Karger AG, Basel fying benefit from conventional hearing aids.

Active middle ear implants (AMEI) have been available to treat sensorineural hearing loss (SNHL) for more than a decade. A number of studies demonstrated the safety and effectiveness of several types of AMEIs in the last years [1–7]. Substantial experience has been gained with the Vibrant Soundbridge (VSB; MED-EL, Innsbruck, Austria) which has been proven to be a safe, appropriate and cost-effective rehabilitation alter-

native for patients with SNHL who are unable to achieve adequate benefit or are medically unable to tolerate conventional hearing aids (HAs) [2, 7, 8]. Previous studies reported improvements in overall sound quality, clarity of sound and tone quality: they also indicated high satisfaction scores with the VSB as a treatment for SNHL [6, 9]. Several comparative studies of the VSB in high-frequency SNHL found better speech recognition scores with the AMEI as compared with several types of conventional HAs [10–13]. In recent years, alternative techniques for coupling for the transducer to the middle ear have been developed. For example, the round-window technique or a floating mass transducer-total ossicular replacement prosthesis (FMT-TORP), which allows the VSB indication to be extended to conductive and mixed hearing losses [14–17]. However, the VSB was originally designed for use in SNHL using an incus coupling of the FMT to the intact ossicular chain. The incus application bypasses both the ear canal and the tympanic membrane and reduces acoustic feedback. In addition, the occlusion effect and ear canal distortions that occur at high acoustic amplification levels are minimized. In the frequency range above 4 kHz, the FMT’s frequency response delivers more maximum amplification as compared with the maximum output that can be realized with conventional HAs. In the HA literature, it is controversially discussed whether or not high-frequency audibility is beneficial to speech recognition [18, 19]. Many studies found no significant improvement or significant benefit only in background noise, whereas other authors found improvements in quiet and noise, as well as in other auditory abilities, such as spatial hearing, HA acceptance, and sound quality. In the AMEI literature, authors have suggested that stable high-frequency amplification via direct drive of the ossicular chain might contribute to improved speech recognition, especially in noise [10, 11, 20]. Unfortunately, AMEI studies only sporadically report on VSB-aided pure tone hearing thresholds for the high-frequency range above 4 kHz; published data in the extended frequency range from 6 to 8 kHz are very rare. Only three studies reported VSB-aided thresholds in the frequency range of 6–8 kHz in a few subjects [10, 12, 20]. The aim of this study is to evaluate gain at the threshold level and speech recognition performance in 54 subjects with mild-to-severe symmetrical SNHL. All subjects received a VSB system at an implant program in an ear-nose-throat clinic in a tertiary referral hospital. We assessed pre- and postoperative hearing thresholds (0.25– 8 kHz) in the unaided and the VSB-aided condition. In addition, speech recognition performance in unaided, HA and VSB conditions was evaluated. Methods Study Design A within-subjects, retrospective study design was used to assess audiologic status and performance before and after implantation of the VSB.

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Subjects All subjects in this study received a VSB system VORP 502/AP 404 between the years 2000 and 2008 at the ear-nose-throat clinic in a tertiary referral hospital (ENT Department, Landesklinikum St. Pölten, Austria). In total, 29 male and 25 female VSB users were included. On average, age at implantation was 52.3 years, with a range from 30 to 75 years. All subjects had a symmetrical pure SNHL that had been stable for at least 2 years before surgery and had normal middle ear impedance (‘type A’ tympanogram) with no air-bone gap. An incus coupling of the FMT to the ossicular chain was performed by a single surgeon. Prior to surgery, 36 subjects used a conventional HA on a daily basis, 18 subjects were HA owners but permanent nonusers despite multiple attempts at HA rehabilitation. Following surgery, all subjects used their implants on a daily basis, including the subjects with preoperative hearing thresholds partly outside the recommended indication field (7 subjects). All subjects had prior experience with or had at least tried conventional HAs with no or unsatisfactory benefit. Figure 1 shows the individual pure tone thresholds prior to surgery and the indication field of the VSB system VORP 502/AP 404 as recommended by the manufacturer. Test Setup All audiologic tests were performed by a speech therapist in a single calibrated and sound-treated, double-walled audiometric test chamber. Hearing threshold measurement was performed with circumaural headphones. In the VSB-aided condition, warble-tone sound field audiometry with a loudspeaker 1 m directly in front of and level with the subject’s head was applied. In free-field measurements, the contralateral ear was plugged. For speech audiometry, prerecorded lists of German monosyllabic words (Freiburger monosyllables) were presented at 65 and 80 dB SPL in the sound field and a percent correct score was calculated [22]. Device Fitting The audioprocessor of the VSB was fitted with Symfit© and Connexx© software. Initial fittings were based on the DSL[i/o] fitting strategy [21], which was then adjusted according to subjective feedback from the patient if necessary. Data Analyses Hearing thresholds are presented in a multiplot figure displaying all 54 individual audiograms and gain at threshold levels (fig. 1). In addition, mean preoperative and postoperative unaided and VSB-aided hearing thresholds are presented. Hearing gain at threshold was calculated by subtracting the VSB-aided thresholds from the unaided postoperative thresholds (fig. 2). Monosyllabic word scores are shown in a boxplot view and include medians (bold vertical lines), the middle 50% range of the scores (25th to 50th percentiles, unfilled or shaded boxes), and the range of the distribution not including outliers (whiskers). Outliers were scores lying 1.5 times above or below the difference between the 75th and 25th percentiles and are indicated as dots (fig. 3). Statistical analyses were performed using the two-sample, paired Wilcoxon signed-rank test and were run on a SPSS 15.0 software platform [23]. The 0.05 level was used to test for significance.

Results

Pure Tone Thresholds and Hearing Gain at Threshold Level Figure 1 shows unaided preoperative and postoperative individual hearing thresholds for audiometric test frequencies of 0.25–8 kHz for all 54 subjects (fig. 1a, b). Aided

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0.25

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Fig. 1. Individual hearing thresholds of 54 patients with SNHL in unaided preoperative (a), unaided postoperative (b) and VSB-aided conditions (c). Mean hearing thresholds for each condition (d). Dashed lines frame the recommended indication field for the VSB (VORP 502/AP 404) system.

free-field, warble-tone thresholds with the VSB are given in figure 1c. Mean values are given in figure 1d. Compared with the unaided preoperative and unaided postoperative condition, hearing thresholds improved significantly for each frequency with the activated VSB (p ! 0.001). The individual gain at threshold level is given in figure 2. Large interindividual differences are seen, reflecting the individual hearing losses, which ranged from mild to severe. Mean gain (dB) averaged 25.7 (0.25 kHz), 20.9 (0.5 kHz), 20.5 (1 kHz), 23.8 (2 kHz), 30.2 (3 kHz), 36.1 (4 kHz), 37.6 (6 kHz) and 37.9 dB (8 kHz). Comparing unaided preoperative pure tone thresholds with thresholds measured 3 months following implantation, a mean decrease in pure tone averages (PTA, 0.25– 8 kHz) by 3.9 dB was observed (fig.1d). However, threshold changes showed large variability and ranged from of –7.5 to +13.7 dB from pre- to postoperative intervals.

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Fig. 2. Individual gain at threshold level provided by the activated VSB system (n = 54). Fig. 3. Monosyllabic word recognition in percent correct at 65 and 80 dB SPL in unaided and aided conditions. UA = Unaided; HA = hearing aid, n = 36; VSB = Vibrant Soundbridge, n = 54.

Monosyllabic Word Recognition in Quiet Figure 3 shows the percent correct scores for monosyllabic words in quiet at 65 and 80 dB SPL in a boxplot view. In the HA condition, only the regular HA users (n = 36) were included in the analyses. No scores were collected for the permanent HA nonusers (n = 18). Percent correct scores improved from a mean of 30% in the unaided condition at a presentation level of 65 dB SPL to 44% in the HA-aided condition (p ! 0.001). Compared with the HA, a further improvement to 57% was achieved in the VSB-aided condition (p ! 0.05). At a presentation level of 80 dB SPL, mean scores of 58% for the unaided condition improved to 67% for the HA-aided condition (p 1 0.05). A further improvement to 80% word recognition was measured for the VSB-aided condition when compared to the HA-aided condition (p ! 0.05). When comparing unaided with VSB-aided conditions, all differences in monosyllabic word scores were significant at both presentation levels of 65 and 80 dB SPL (p ! 0.001).

Discussion

The aim of the present study was to assess the postoperative hearing performance of 54 VSB users with mild-to-severe SNHL and compare it to the preoperative unaided and aided situation with walk-in HAs. In our subjects, substantial gains at the threshold level were measured in all subjects and in the entire frequency range from 250 to 8,000 Hz (fig. 2). Individual gains at threshold showed large variability, reflecting the wide range of individual hearing losses that covered almost the entire indication field of the VSB system.

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Before discussing the results of the present study, we addressed the question of whether or not the fitting of the VSB audioprocessor was adequate. The patients’ everyday fittings were used, which are nonlinear fittings and result in input-output curves that depend on the particular input level. In this setup, the hearing gain can be referred to as gain at threshold level [5]. The clinician can use this information to estimate the appropriateness of the hearing instrument fitting and to determine the extent to which the speech spectrum of the speech banana is made audible by the AMEI compared with the unaided condition. Mean pre- and postoperative hearing thresholds (PTA 0.25–8 kHz) show a small hearing deterioration of 3.9 dB that might be attributed to the surgery, AMEI use, progression of hearing loss or increased load on the middle ear structures by the FMT [24]. By comparing individual pre- to postoperative PTA values, no air-bone gaps but a high variability between pre- and postoperative air conduction thresholds was found: a deterioration of 1 to 5 dB occurred in 26 subjects, a deterioration of more than 5 dB in 17 subjects, no change or an improvement of up to 7.5 dB in 11 subjects. This indicates that individual or surgery-associated factors might be more likely than a systematic massloading effect. In addition, the intrasubject test-retest variability of multisession threshold audiometry should be considered [25]. Despite these considerations, aided thresholds revealed that the activated AMEI easily compensated for hearing deterioration. The greatest gains at threshold in the low frequencies 250 and 500 Hz were 50 and 45 dB, respectively. In the mid frequencies from 1,000 to 3,000 Hz, the greatest gains ranged from 40 to 55 dB. These findings agree well with measurements by Snik et al. [26], who found similar maximum gains of up to 40 dB at 500 Hz. A large gain of 70 dB SPL and more for frequencies between 4 and 8 kHz was measured in single subjects. These observations are surprising because they exceed the technical specifications for the VSB system. Maximum gain curves (equivalent dB) and maximum output curves (equivalent dB SPL) are not available for the VSB configuration VORP 502/AP 404 which was used in our study. However, according to a detailed data sheet for the next generation audio processor, the Amadé processor, the maximum achievable gain is specified with 54 dB [27]. We were surprised that 7 subjects had gain at threshold exceeding the specified limitation. To investigate this, we studied the individual audiograms and found that all 7 subjects had steeply sloping audiograms in the high-frequency region. In addition, the individual gain peak was exactly within the frequency band of the steep slope. Therefore, we suppose that the high-frequency warble-tone stimulus might have been perceived by an adjacent auditory cochlear filter with surviving hair cells in the apex of the cochlea, also called ‘offfrequency listening’. This effect might have been increased by a loss of outer hair cell function, which results in a widening of auditory filters and shallower filter skirts [28]. Whether or not such cochlear artifacts and distortions might have occurred, the results indicate that the VSB is capable of delivering a large amount of high-frequency amplification that is well tolerated by the user, even when the hearing loss configuration is steeply sloping.

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In general, our findings on unaided and aided hearing thresholds show that the VSB system provides substantial and stable amplification up to the high frequencies and allows an adequate treatment in SNHL within the entire recommended indication field. Regarding speech recognition results, an audiologic benefit for both device types, the HA and the AMEI, as compared with the unaided condition, was found. When comparing aided conditions, monosyllabic word recognition with the AMEI was significantly better than with the subjects’ walk-in HA. Subjects with hearing losses near and at the lower limit of the recommended indication field also received benefit from the VSB system. Other authors found similar improvements when comparing the VSB with different types of HAs. Uziel et al. [10] attributed the benefit to superior sound transmission quality via direct-drive stimulation. In that comparative study, the authors assessed the hearing benefit for patients with high-frequency hearing loss obtained from an AMEI and a conventional hearing aid using the same hearing aid processing circuitry. According to their measurements, significant advantages for speech discrimination in quiet and in noise in favor of the AMEI were found, despite similar amounts of gain for the study HA and the VSB. The data demonstrate the potential benefit of vibromechanical stimulation in cases of SNHL with unsatisfactory benefit from conventional HA. This is also reflected in the high rate of device acceptance: in our 54 subjects, 36 used a HA prior to surgery and 18 subjects (or 33%) were HA owners but permanent nonusers despite multiple adequate attempts of conventional HA rehabilitation. In contrast, all of them adopted their AMEI immediately after the first fitting and use their device on a daily basis.

Conclusion

In cases of SNHL with unsatisfying benefit from conventional HAs, the VSB system offers an attractive and effective hearing solution.

References 1 Zenner HP, Leysieffer H: Total implantation of the Implex TICA hearing amplifier implant for high frequency sensorineural hearing loss: the Tübingen University experience. Otolaryngol Clin North Am 2001;34:417–446. 2 Mosnier I, Sterkers O, Bouccara D, et al: Benefit of the Vibrant Soundbridge device in patients implanted for 5 to 8 years. Ear Hear 2008; 29:281–284. 3 Lenarz T, Weber BP, Issing PR, et al: The Vibrant Soundbridge: a new kind of hearing aid for sensorineural hearing loss. 2. Audiological results. Laryngorhinootologie 2001; 80:370–380.

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4 Kasic JF, Fredrickson JM: The Otologics MET ossicular stimulator. Otolaryngol Clin North Am 2001;34:501–513. 5 Snik AF, Mylanus EA, Cremers CW, et al: Multicenter audiometric results with the Vibrant Soundbridge, a semi-implantable hearing device for sensorineural hearing impairment. Otolaryngol Clin North Am 2001;34:373–388. 6 Sterkers O, Boucarra D, Labassi S, et al: A middle ear implant, the Symphonix Vibrant Soundbridge: retrospective study of the first 125 patients implanted in France. Otol Neurotol 2003; 24:427–436.

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7 Schmuziger N, Schimmann F, àWengen D, Patscheke J, Probst R: Long-term assessment after implantation of the Vibrant Soundbridge device. Otol Neurotol 2006; 27:183–188. 8 Snik AF, van Duijnhoven NT, Mylanus EA, Cremers CW: Estimated cost-effectiveness of active middle-ear implantation in hearing-impaired patients with severe external otitis. Arch Otolaryngol Head Neck Surg 2006;132:1210–1215. 9 Luetje CM, Brackman D, Balkany TJ, et al: Phase III clinical trial results with the Vibrant Soundbridge implantable middle ear hearing device: a prospective controlled multicenter study. Otolaryngol Head Neck Surg 2002; 126:97–107. 10 Uziel A, Mondain M, Hagen P, Dejean F, Doucet G: Rehabilitation for high-frequency sensorineural hearing impairment in adults with the Symphonix Vibrant Soundbridge: a comparative study. Otol Neurotol 2003; 24:775–783. 11 Truy E, Philibert B, Vesson JF, Labassi S, Collet L: Vibrant Soundbridge versus conventional hearing aid in sensorineural high-frequency hearing loss: a prospective study. Otol Neurotol 2008; 29:684–687. 12 Todt I, Seidl RO, Gross M, Ernst A: Comparison of different Vibrant Soundbridge audioprocessors with conventional hearing aids. Otol Neurotol 2002;23:669–673. 13 Boeheim K, Pok SM, Schloegel M, Filzmoser P: Active middle ear implant compared with open-fit hearing aid in sloping high-frequency sensorineural hearing loss. Otol Neurotol 2010;31:424–429. 14 Colletti V, Soli SD, Carner M, Colletti L: Treatment of mixed hearing losses via implantation of a vibratory transducer on the round window. Int J Audiol 2006;45:600–608. 15 Huber AM, Ball GR, Veraguth D, Dillier N, Bodmer D, Sequeira D: A new implantable middle ear hearing device for mixed hearing loss: a feasibility study in human temporal bones. Otol Neurotol 2006; 27: 1104–1109. 16 Beltrame A, Martini A, Prosser S, Giarbini N, Streitberger C: Coupling the Vibrant Soundbridge to cochlea round window: auditory results in patients with mixed hearing loss. Otol Neurotol 2009; 30:194–201.

17 Frenzel H, Hanke F, Beltrame M, Steffen A, Schönweiler R, Wollenberg B: Application of the Vibrant Soundbridge to unilateral osseous atresia cases. Laryngoscope 2009; 119:67–74. 18 Amos NE, Humes LE: Contribution of high frequencies to speech recognition in quiet and noise in listeners with varying degrees of high-frequency sensorineural hearing loss. J Speech Lang Hear Res 2007; 50:819–834. 19 Baer T, Moore BC, Kluk K: Effects of low pass filtering on the intelligibility of speech in noise for people with and without dead regions at high frequencies. J Acoust Soc Am 2002; 112:1133–1144. 20 Böheim K, Nahler A, Schlögel M: Rehabilitation of high frequency hearing loss: use of an active middle ear implant. HNO 2007;55:690–695. 21 Sandlin R: Textbook of Hearing Aid Amplification, Technical and Clinical Considerations, ed 2. San Diego, Singular Publishing Group, 2000, pp 82–86. 22 Hahlbrock K-H: Sprachaudiometrie, ed 2. Stuttgart, Thieme, 1970. 23 Hollander M, Wolfe DA: Nonparametric Statistical Inference. New York, Wiley, 1973. 24 Needham AJ, Jiang D, Bibas A, Jeronimidis G, O’Connor P, Fitzgerald A: The effects of mass loading the ossicles with a floating mass transducer on middle ear transfer function. Otol Neurotol 2005; 26:218–224. 25 Schmuziger N, Probst R, Smurzynski J: Test-retest reliability of pure-tone thresholds from 0.5 to 16 kHz using Sennheiser HDA 200 and Etymotic Research ER-2 earphones. Ear Hear 2004;25:127–132. 26 Snik AF, Mylanus EA, Cremers CW, Dillier N, Fisch U, Gnadeberg D, Lenarz T, Mazolli M, Babighian G, Uziel AS, Cooper HR, O’Connor AF, Fraysse B, Charachon R, Shehata-Dieler WE: Multicenter audiometric results with the Vibrant Soundbridge, a semi-implantable hearing device for sensorineural hearing impairment. Otolaryngol Clin North Am 2001;34:373–388. 27 Vibrant Soundbridge, The Middle Ear Implant System: Document No. 28066, Data Sheet p14, printed by Vibrant Med-El Hearing Technology GmbH, Innsbruck, Austria, 2009. 28 Glasberg B, Moore B: Auditory filter shapes in subjects with unilateral and bilateral cochlear impairments. J Acoust Soc Am 1986; 79:1020–1033.

Prof. Klaus Boeheim Department of Otorhinolaryngology, Head and Neck Surgery Landesklinikum St. Pölten Propst Fuehrerstrasse 4 AT–3100 St. Pölten (Austria) Tel. +43 2742 300 12901, Fax +43 2742 300 12919 E-Mail Klaus.Boeheim @ stpoelten.lknoe.at  

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Böheim K (ed): Active Middle Ear Implants. Adv Otorhinolaryngol. Basel, Karger, 2010, vol 69, pp 59–71

The Esteem System: A Totally Implantable Hearing Device J. Maurer · E. Savvas Department for Otorhinolaryngolgy, Head and Neck Surgery, and Center for Hearing and Communication, Katholisches Klinikum Koblenz, Koblenz, Germany

Abstract The Esteem totally implantable active middle ear implant is a new technology to augment hearing in patients suffering from moderate-to-severe and severe sensorineural hearing loss. In contrast to conventional (acoustic) hearing aids, the system uses two piezoelectric transducers (PZTs). PZTs are used as the sensor and driver to replace the function of the middle ear. Sound is received via a PZT sensor that picks up eardrum vibrations, following the piezoelectric principle, and transforms them into an electric signal. This signal is filtered, modified, amplified and transferred to a PZT driver, which mechanically drives the stapes and thereby the inner ear. The sound processor also contains a power source, which is an implantable lithium iodide battery. All components of the hearing restoration system are totally implantable to offer good sound fidelity and reduce hearing aid stigma caused by the visibility of conventional and semi-implantable hearing systems. Our experience shows that this system can provide considerable benefit to patients with sensorineural hearing loss. Copyright © 2010 S. Karger AG, Basel

System Concept and Background

There is accumulating evidence supporting the principle of directly driving the ossicular chain as a means of providing amplification and good sound transmission to hearing impaired patients. The Esteem system concept is based on two piezoelectric transducers (PZTs): one placed on the incus and the other placed on the stapes. The first transducer (the sensor, fig. 1a, b) detects tympanic membrane motion in response to sound via the malleus on the incus. The sound signal is then processed by the processor (fig. 1a, b) to

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Fig. 1. a The Esteem implanted system components. b The Esteem implantable components.

meet the patient’s hearing loss and is used to drive a second PZT (the driver, fig. 1a, b) placed on the stapes. This vibrates the stapes and mechanical vibration is detected as sound in the cochlea. To prevent feedback, the incus is separated from the stapes at the level of the incudostapedial joint and 1–2 mm of the long process is resected during device placement. Success is dependent on two key principles: the reversible electromechanical properties of piezoelectric ceramics and the proven benefits of directly driving the ossicular chain. The Esteem System (Envoy Medical Corporation, St. Paul, Minn., USA) carries the CE marking in Europe since 2006.

PZT Sensor and Driver

Piezoelectric materials have the property of reversible electromechanical transduction. When a force is applied to the material, voltage is generated and, conversely, when voltage is applied, motion is created. This property is most efficient when the ceramic is formed in the shape of a cantilever (diving board) with one end fixed and the other end mobile. This results in the greatest displacement for an applied voltage. Each PZT consists of two internal plates of a PZT crystal aggregate of PbZrxTixO3, and the configuration is known as a bimorph. The plates can be connected in series or in parallel. When the sensor transducer plates are connected in series, a greater voltage is generated; when the driver transducer plates are connected in parallel, a greater displacement for an applied voltage is generated. The sensor PZT is similar to a microphone in a conventional hearing aid. A conventional microphone consists of a diaphragm and a ceramic element. The diaphragm serves to collect sound over a large area. The motion of the diaphragm is detected by the ceramic element and converted to a voltage. In the Esteem, the microphone is replaced by the PZT sensor and is placed on the incus. The tympanic membrane acts as

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the diaphragm, collecting sound over a far greater area than the sensor alone. In addition, the tympanic membrane is situated at the most medial end of the ear canal, which is advantageous. The external auditory canal acts as a filter, giving stronger emphasis to high-frequency than to low-frequency sounds [1]. The amplification provided by the ear canal is as much as 10 ! (20 dB) and is greatest at frequencies 1 through 4 kHz. Low-frequency sounds are amplified minimally or not at all. The relative effect of sound filtration is determined both by the frequency and the incident direction of the sound. Placing any microphone or the Envoy PZT sensor at the tympanic membrane provides a natural filtration benefit. The PZT sensor is fastened to the wall of the mastoid with cement to fix one end, while the motion of the incus vibrates the other end (the sensor tip). Sensor output is relatively constant across frequencies, and around 1,000 Hz it begins to roll off. A similar roll-off is seen in stapes displacement. Because the stapes and malleus/incus displacements roll off at a similar rate, the driver output at any one frequency is a direct function of the sensor input at the same frequency. The processes of amplification, filtration, and compression are adjusted to compensate for the patient’s particular hearing loss. The PZT driver is fastened to the wall of the mastoid with cement to fix one end, while the motion of the PZT driver vibrates the stapes via attachment to the stapes head with a microscopic drop of glass ionomer cement with zero bias. When a voltage is applied to the driver transducer, the tip of the cantilever displaces the stapes. There is a theoretical advantage of directly driving the ossicular chain. This concept has been developed over many years with encouraging results. Wilska, in 1935, placed pieces of soft iron on the tympanic membrane, and, under the influence of an electromagnetic field, subjects were able to perceive tones. In the 1970s and 1980s, magnets were placed on the stapes and speech conduction tested. Yanagihara et al. [2] developed a partially implantable device, which was successfully used in over 60 subjects but suffered from insufficient acoustic output. It consisted of an external microphone and an internal piezoelectric driver placed on the stapes. Implanted patients showed some encouraging trends, especially in speech discrimination results. Kodera et al. [3], in a study of 6 implanted patients, demonstrated improved performance for both speech and music when compared with a conventional hearing aid. Speech discrimination scores were 10% better than with conventional hearing aids in the same patients. Testing in an environment with competing background noise, this difference was statistically significant at the 0.05 level. Similar results were reported by Suzuki et al. [4]. The active middle ear implant was superior to a conventional hearing aid in the perception of speech, music, and environmental sounds. Patients preferred the fidelity of sound, claiming it was more natural sounding than their hearing aids. Active middle ear implant results have been very encouraging; however, the number of patients with speech discrimination data was small and all patients had had only mild or moderate hearing losses. Patients with more severe hearing losses, likely candidates for the Esteem, tend to have greater difficulties with impaired speech

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discrimination and recruitment. The Esteem system increases the efficiency of sound reaching the inner ear, which may aid in improved speech discrimination. However, it does not improve cochlear or eighth nerve function; therefore, the impressive gains of the Japanese device may be less evident in a more compromised population. In a 1973 study of directly driving the ossicular chain, Goode and Glattke [5] noted that patients preferred speech presented through a magnet attached to the ossicular chain to speech presented through a conventional audiometer. No improvement in speech discrimination scores was reported. This may be because only quiet and not noisy background conditions were tested. The Japanese group noted the greatest improvement in a noisy environment. Mahoney and Vernon [6] recorded cochlear microphonics, which can be played through loudspeakers and recognized as sound. Using a hearing impaired guinea pig, they initially presented speech to the animal’s ear through a conventional hearing aid and then by directly driving the ossicular chain with a piezoelectric crystal. The cochlear microphonic was recorded and played back to normal hearing listeners who were asked to identify the words. Discrimination scores were 16% better in normal hearing adults when the ossicular chain was directly driven, which might suggest that the quality of information being received by the inner ear is better when the chain is directly driven. The reason for the possible sound quality improvement with direct-drive stimulation could relate to the impedance of air. A conventional hearing aid detects sound, which is processed, amplified and then played via a loudspeaker. This loudspeaker moves a cushion of air, sitting between the speaker and the ear drum. This is an inefficient process. Transient sounds are not conducted well, and the presence of the hearing aid in the external canal occludes the ear and prevents natural filtering. In newer aids with an open ear canal, some acoustic energy is lost because the open ear canal is open. Directly driving the ossicular chain potentially allows more efficient sound transmission to the ossicles. Transient sounds are more efficiently conducted, and because the ear canal is unoccluded, less acoustic gain is required than with a conventional aid. Studies of the Vibrant Soundbridge demonstrated the benefits of directly driving the ossicular chain. Patients preferred the sound quality and found hearing in noisy environments easier than with conventional hearing aids [7]. The data were supported by the observations of Maassen et al. [8] with direct vibration of the ossicular chain. One can conclude that by directly driving the ossicular chain: (1) mechanically induced sounds have the same characteristics as their acoustic counterparts, (2) in patients with mild-to-moderate hearing losses, there is a possible improvement in speech discrimination compared with a conventional hearing aid, and (3) speech discrimination improvements are most evident for speech in noise, music, and environmental sounds.

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Sound Processor To optimize the PZT sensor input and the PZT driver output, a series of electronic circuits is required. These are contained within a titanium enclosure, the sound processor (fig. 1a, b). The sound processor also contains a battery to power the circuits, which are mostly contained within an application-specific integrated circuit and perform audio signal processing and digital telemetric functions. Sound vibrates the tympanic membrane, which moves the PZT sensor. A small generated voltage is conducted along the lead wires into the header, which is the connector block attached to the sound processor into which the leads connect (similar to a pacemaker). The signal then passes into the application-specific integrated circuit, where it is separated into two channels and filtered. Compression is applied to optimize the available dynamic range. The signal is amplified to achieve acoustic parity and compensate for the patient’s particular hearing impairment. The output signal passes out of the header to the PZT driver lead wire. This signal oscillates the driver, moving the stapes in response to sound. The use of piezoelectric materials and a low-power circuit design allow an expected battery life of 6–9 years, depending on individual patient programming and daily usage. A bi-directional telemetric circuit controls the amplifier circuitry, tones generated, and device programming. Within the titanium can is a loop antenna, which receives and transmits binary control codes. Commands from programmer are downloaded to the device, and changes within the memory are made. Synthesized tones from an internal tone generator are used to measure hearing thresholds, volume setting, program selection, and compression ratio and knee point settings in the channels. Tonal confirmation of any parameter change is provided. The state of the device memory, device serial number and other parameters can also be uploaded to the programmer. Multiple redundant protection mechanisms exist within the telemetric circuitry so that aberrant codes do not alter device performance. Each implanted device has a unique electronic access code, providing a further measure of security. The lead wires within the body may act as an antenna, detecting stray radiofrequency signals generated from cellular telephones, microwaves, and many other electronic devices. These signals can interfere with the signals entering the system, potentially leading to sound degradation or to other unwanted noise. To overcome this effect, the titanium case is laser welded hermetically shut, and all leads entering or exiting the case pass through broadband electromagnetic interference (EMI) discoidal filters. These discoidal filters are continuous with the case and are effective in removing the 10 MHz to 10 GHz signals presented by most appliances and cellular telephones. Indications Patients should have a sensorineural hearing impairment and be 18 years or older at the time of implantation. In addition, they should have had experience with hearing

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0.25

0.5

1

kHz 2

4

6

8

0 20

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40 60 80 100

Fig. 2. Audiological inclusion criteria.

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aids. Hearing thresholds should be stable and between 35 and 85 dB HL for audiometric test frequencies of 500–4,000 Hz with a word recognition score of 40% or greater (unaided, Freiburg monosyllabic word test). The audiometric indication field is shown in figure 2. Retrocochlear hearing loss should be ruled out. A CT scan should show a mastoid large enough to accommodate the sensor and driver. Surgical Procedure The surgical procedure generally follows the techniques used for cochlear implantation, the main difference being that the inner ear remains untouched. The PZT sensor and the PZT driver are attached to the ossicular chain. After incising the skin, subcutaneous and muscle flaps are formed and a mastoidectomy is carried out. A bone bed is then drilled out to accommodate the sound processor, and a tunnel is created for the cable link. The ossicular chain, especially the long process of the incus and the stapes, can be fully exposed via posterior tympanotomy. A CO2 laser is used to remove 2 mm of the long process of the incus, including the lenticular process. The PZT sensor is fixed to the superior edge of the mastoidectomy with the tip positioned onto the incus body. The PZT driver is attached to the inferior edge of the mastoidectomy and its tip positioned onto the exposed stapes head. The sound processor is fixed into the bone bed. The wound is closed after intraoperative testing of the whole system using laser Doppler vibrometry and, optionally, acoustic brainstem audiometry. Preparation of the Patient Surgery is performed with the patient lying in a horizontal position with the head turned to the side contralateral to implantation. After shaving the incision area, local anesthetics with adrenaline are applied, facial nerve monitoring is installed, and the skin is disinfected. The patient’s head is covered with sterile drapes.

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The incision must always be a minimum distance of 1 cm from the implant. It is made at the beginning of the mastoid tip at a distance of 1 cm of the retroauricular fold, which turns craniodorsally approximately 2 cm above the ear. The subcutaneous-muscle-periost flap is prepared dorsally and the pericranium is elevated further to accommodate the processor. Hemostasis must be carefully performed to minimize the use of bipolar cautery after positioning the implant. The mastoid plane, the temporal line, and the mastoid tip are exposed and the external auditory canal identified. The mastoid is drilled out to accommodate the PZT sensor and PZT driver. The bone covering the middle and posterior cranial fossae, the sigmoid sinus up to the mastoid tip, the labyrinth with its horizontal and posterior semicircular duct, the antrum with the incus, and the osseous canal of the facial nerve in the mastoid is thinned out. The posterior wall of the external auditory canal is then thinned until all cells are removed. The surrounding bone at the incus site must be completely removed in order to have wide access to the area around the antrum. The wall of the external auditory canal may be thinned in this process. The osseous cells in the direction of the middle cranial fossa are also drilled out. Approximately 1 cm behind and above the mastoidectomy, a bone bed is created for the sound processor. A plane osseous area on the occipital bone and temporal bone is selected to achieve a flat bone bed. The bone bed is drilled out. Irregularities must be removed in order to prevent the implant from rocking. Usually, it is not necessary to expose the dura. The sound processor is later fixed in the bone bed with crossed resorbable sutures or by tightly suturing the pericranium and the muscle-skin flap over the processor and thereby fixing the implant. A posterior tympanotomy is performed with diamond drills of various sizes between 4 and 1.5 mm under an operating microscope. The tip of the short process of the incus, as well as the osseous course of the facial nerve, can provide orientation. Near the tip of the incus, the bone must be removed carefully while adhering to the course of the facial nerve until the first cells are reached in the direction of the middle ear. The bone of the posterior wall of the external auditory canal must be thinned carefully to expose the course of the chorda tympani. The angle of the chorda tympani and the facial nerve is then enlarged and the bone removed until the posterior tympanotomy is extended as far caudally and cranially as possible. The bone in the direction of the tympanic sinus should also be removed. If possible, the entire stapes should be visible from the footplate to the head. It is important to make sure that the drill does not touch the tip of the incus. This preparation is crucial for positioning and fixation of the driver. The ossicular chain must be interrupted to avoid feedback between the PZT sensor and the PZT driver. Therefore, 1–2 mm of the long process of the incus must be resected. First, the incudo-stapedial joint is carefully separated. Then the distal part of the long process of the incus is separated using a laser. Finally, the mobility of stapes, malleus, and incus body is tested. All of them must be mobile. Adhesions should be removed.

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Insertion of the Implant First the PZT sensor is placed, using Glasscock stabilizers, in the superior edge of the mastoidectomy such that the tip of the PZT sensor can be positioned near and over the incus body. It is fixed by a first layer of cement. The tip is connected to the incus body by a microdrop of glassionomer cement, which, after drying, is separated from the incus. Thus, a ‘neojoint’ is created allowing free and unloaded movement of the incus while moving the tip of the PZT sensor. Then the driver is placed again, using a Glasscock stabilizer, in the inferior edge of the mastoid. Its tip comes through the posterior tympanotomy, touching, without loading, the stapes head. It should produce movements of the stapes in a direction vertical to the stapes footplate. It is fixed in the mastoid with cement and the tip is attached to the stapes head by a small amount of glassionomer cement. A final fixation of driver and sensor in the mastoid using additional cement ensures their stable position. The sound processor and battery are positioned in the bone bed and fixed as described above. The cable links from the sensor and driver are cleaned and connected to the processor. Lastly, the system test is performed and, if satisfactory, the procedure is finished by suturing the muscle, subcutaneous, and skin layers. During surgery, the functioning of the implanted parts and their optimal positioning is measured using laser Doppler vibrometry. Before closure, a system test is performed. Patient Experience We have more than 10 years’ experience with implantable hearing aids. Currently, we are implanting partially implantable systems and fully implantable systems in sensorineural and mixed hearing-loss cases. Since 2002, we have implanted 10 patients with the Envoy/Esteem I system: 7 within the international multicenter phase II trial and 3 with the same inclusion criteria after study closure. There was no surgical complication or early or late wound complications. There was no significant change in cochlear function as measured by bone conduction thresholds after the surgery. Nine of 10 patients achieved or exceeded their preoperative hearing results while enjoying the advantages of a fully implantable middle ear device. Two patients had transcanal revision surgeries to optimize the driver-stapes connection including 1 patient who was explanted after 12 months because of feedback. His stapes arch was high, and the tip of the driver touched the tympanic membrane causing feedback. One patient was explanted after 31 months of successful usage requiring processor replacement due to battery life depletion; however, he refused a new implant fearing further battery changes. Both patients had reconstruction of their ossicular chain with closure of the air bone gap within 10 dB between 0.5 and 4 kHz. One patient who continuously used the device on a 24-hour basis required a battery change after 28 months. Two more patients had battery changes after 37 and 39 months. The remaining patients use their Esteem between 3 and 40 months. All patients implanted would make the same decision again, and two do not use their contralateral hearing aid any longer because of good benefit from the Esteem.

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Hearing Aid

Esteem

% 50 40 30 20 10 0 –10 –20 –30 –40 APHAB average Ease of total benefit communication

Background noise

Reverberation

Aversiveness of sound

Fig. 3. APHAB results with hearing aids and Esteem system from 6 patients 3–6 months after the onset of the system. Ease of communication (EC): Communication under relatively favorable conditions. Background noise (BG): communication in settings with high background noise. Reverberation (RV): communication in reverberant rooms such as classrooms. Aversiveness (AV): unpleasantness of harsh environmental sound.

Hearing aid

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40 30 20 10 0 0.5

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Fig. 4. Average functional gain with Esteem (dark bars) and hearing aids (light bars) 10–14 months after the onset of Esteem (n = 7).

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Two wish to have their second ear implanted. The primary results of the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire for 6 patients are shown in figure 3. There was a considerable difference in functional gain with hearing aids and with the Esteem (fig. 4). Free field monosyllabic word recognition scores presented at 65 dB improved in all patients from a range of 70–90% correct with best-fitted hearing aids to a range of 90–100% correct with the Esteem.

Discussion

Conventional hearing aids, such as completely-in-the-canal hearing aids, are cosmetically acceptable but are appropriate only for mild-to-moderate sensorineural hearing loss. Therefore, cosmetically less acceptable behind-the-ear hearing aids are the option for the vast majority of patients. Conventional hearing aids require an ear mold, thus creating an occlusion effect. Ear molds are uncomfortable and, if the patient has a profound loss, there are often problems with feedback. The occlusion effect may be reduced by ‘open ear’ hearing aids, introduced in the last several years. Although conventional hearing aids have improved, they still have many deficiencies. Conventional hearing aids perform by overdriving the stapes. To do this, a column of air between the speaker and the tympanic membrane must move the ossicular chain. This is an ineffective method to amplify a severe-to-profound hearing loss, and requires a powerful hearing aid using a lot of battery power. High- and low-pass filters, compression circuits, and other programmable features improve sound processing quality in newer hearing aids. However, many of these devices may still not perform adequately in noisy environments. The greatest problem with most hearing aids is poor quality and clarity of sound, particularly for patients with poor speech discrimination. All hearing aid deficiencies can be overcome with a fully implantable hearing device such as the Esteem. In addition to reducing occlusion, feedback, stigma, and poor sound quality found in conventional hearing aids, a totally implantable device allows the patient to carry on with a normal lifestyle. The patient can shower, swim, scuba dive, or parachute out of an airplane. Patients of all ages are not handicapped during their activities. The system can be left on during sleep. Sweating during work or sports does not compromise system function. Patients can also walk through a strong electromagnetic field without worrying that their device will be affected. Its components have been developed and tested since the late 1990s [9–13]. Our preliminary results in a small series of a highly selected group of patients are more encouraging than the first results published from the phase I clinical trial [14]. Since then, the system has been improved in both technical and processing issues, and, with careful surgery, reliable results can be achieved. As with all new technology and surgical methods, there is a learning curve even for the experienced surgeon. The key to success with this system is the accurate positioning and fixation of the sensor

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and driver to the ossicles. Intraoperative monitoring of the implanted parts and their optimal positioning by use of laser Doppler vibrometry allows very accurate testing of each part as well as the system as a whole, and gives a good prediction of postoperative hearing gain. The device positioning and intraoperative monitoring at each step is the most time-consuming part of the surgery. We have not observed device extrusions. Battery life has been the greatest challenge. The current Esteem II has a battery life of 6–9 years, depending on usage, with no recharging required. After that time, a minor surgical procedure is necessary to replace the battery. This is always combined with an update to the latest processor version because both the battery and processor are housed in the sound processor package. Further improvements in power consumption, as well as in battery technology, promise even longer longevity. In order for the Esteem system to work properly, the incus must be disarticulated. For some surgeons, this presents a moral dilemma because the patient will have a sensorineural hearing loss plus a conductive loss in the unaided situation. The question is whether or not one should do this to a ‘normal’ incus. It will improve the patient’s hearing with the functioning implant. If a surgeon is faced with a patient who has otosclerosis, he or she has no qualms about removing the stapes or its suprastructure and even opening the inner ear for the same reason: it will most likely improve the individual’s hearing. If the incus is eroded, surgeons have no difficulty in removing it and replacing it with a prosthesis because it will most likely improve the hearing. Some surgeons point out that the ossicular chain is not normal. However, in many sensorineural hearing losses, the ossicular chain may be normal, but it does not help the patient to hear. To overcome feedback with the Esteem, it is necessary to interrupt the ossicular chain during the surgical procedure. If the Esteem system fails, or if the patient no longer wishes to use it, the additional conductive hearing loss caused by the disarticulated incus has to be restored. If the long process of the incus has been resected, it can be reconnected to the stapes by use of different kinds of prostheses or by cementing it to the stapes. Most scientific reports indicate that hearing can be restored in patients missing an incus to within 10 dB of the cochlear reserve (bone line on the audiogram) in about 65–70% of the cases and to within 20 dB in 80% or more [16, 17]. Reconstruction cases are chronically diseased ears: the tympanic membranes are most likely not normal and there is poor eustachian tube function. There may also be middle ear mucosal problems with chronic inflammatory processes. None of these circumstances should occur in a patient with a sensorineural loss and an otherwise normal ear. For this reason, one would expect closure of the air-bone gap to be as good as one would expect to see in stapes surgery. This would be closure to within 20 dB in 90% of the time [18]. It may not be too radical to disarticulate a ‘normal’ incus, if the normal ossicular chain does not help the patient to overcome problems created by the sensorineural hearing loss.

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Although conductive hearing loss in an explanted patient can be corrected, the question still remains: is the surgery worth the hearing gain? Evaluation of our patients, based on pure tone averages, warble tone averages, and free field speech recognition showed improved results in comparison to the best-fit hearing aid preoperatively. However, even more convincing are the results of the APHAB questionnaire, showing a significant improvement in all subscales; meaning that everyday life problems associated with hearing impairment were reduced. Implanted patients praise the clarity and fidelity of the system in comparison to their former hearing aids. They enjoy not only music more, but also finer sounds such as birds chirping, soap bubbles bursting, or waves hitting the seashore. The improvement in quality of life from a hearing standpoint was substantial in our group of patients. During the surgery, optimal positioning of the driver and the sensor is critical for a good outcome, requiring a very precise surgical technique as well as a sophisticated intraoperative monitoring technology. The fully implantable Esteem system has demonstrated patient satisfaction with benefit in sound quality and clarity, audibility and speech understanding even in difficult settings. For a select group of patients with sensorineural hearing loss, it is a suitable alternative to conventional hearing aids and provides the otolaryngologist with a further therapeutic modality. With the recently launched Esteem II with more amplification capacity in the higher frequency range and technical refinements, further progress in patient satisfaction, even in patients with severe-to-profound sensorineural hearing loss, can be expected.

References 1 Shaw EAG, Stinson MR: The human external and middle ear models and concepts. Modified from: Mechanics of hearing; in de Boer E (ed): Proceedings of the 1UTAM/ICA Symposium. Amsterdam, Martinus Nijhoff, 1983. 2 Yanagihara N, Sato H, Hinohira Y, et al: Long term results using a piezoelectric semi implantable middle ear hearing device: The Rion device E-type. Otorhinolaryngol Clin North Am 2001; 34: 389– 400. 3 Kodera K, Suzuki JJ, Nagai K, Yabe T: Sound evaluation of partially implantable piezoelectric middle ear implant. ENT J 1994;73:108–111. 4 Suzuki JI, Kodera K, Suzuki M, Ashikawa H: Further clinical experiences with middle ear implantable hearing aids: indication and sound quality evaluation. ORL 1989;51:229–234. 5 Goode RL, Glattke TJ: Audition via electromagnetic induction. Arch Otolaryngol 1973; 98:23–26. 6 Mahoney T, Vernon J: Speech induced cochlear potentials. Arch Otolaryngol 1974; 100:403–404.

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7 Snik A, Cremers C: Audiometric evaluation of an attempt to optimize the fixation of the transducer of a middle-ear implant to the ossicular chain with bone cement. Clin Otolaryngol Allied Sci 2004; 29: 5–9. 8 Maassen MM, Rodriguez Jorge J, Herberhold S, et al: Safe and reliable sound threshold measures with direct vibration of the ossicular chain. Laryngoscope 2004;114:20–2020. 9 Grant I, Kroll K, Welling DB, Levine S: Implantable hearing aid issues: optimizing the position and force of a piezoelectric malleus sensor. Association for Research in Otolaryngology (abstract). The Mid-Winter Meeting, February 1998. 10 Kroll K, Grant IL MD, Meyerson S: The effects of physiological pressure extremes on a piezoelectric malleus sensor. Association for Research in Otolaryngology (abstract). The Mid-Winter Meeting, February 1998.

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11 Levine S, Grant IL, Kraus E, Kroll K: Temporary implantation of a piezoelectric malleus sensor and stapes driver: a preliminary report. American Association of Otolaryngology-Head and Neck Surgery (abstract). The Annual Meeting, September 1998. 12 Grant IL, Kroll K, Welling DB, Levine S, Gonzalez JG, Urbanski P: The implantable hearing aid: impedance matching of a piezoelectric malleus sensor. Association for Research in Otolaryngology (abstract). The Mid-Winter Meeting, February 1998. 13 Javel E, Grant IL, Kroll K, Meyerson SA: A totally implantable hearing system: animal evaluation of a piezoelectric stapes transducer. American Academy of Otolaryngology-Head and Neck Surgery (abstract). The Annual Meeting, September 1998.

14 Chen DA, Backous DD, Arriaga MA, Garvin R, Kobylek D, Littman T, Walgren S, Lura D: Phase 1 clinical trial results of the envoy system: a totally implantable middle ear device for sensorineural hearing. Otolaryngol Head Neck Surg 2004; 131: 904–916. 15 Jenkins HA, Atkins JA, Horlbeck D, Hoffer ME, Balough B, Alexiadis G, Gravis W: Otologics fully implantable hearing system: phase I trial 1-year results. Otol Neurotol 2008; 29:534–541. 16 Maassen MM, Zenner HP: Tympanoplasty type II with ionomeric cement and titanium-gold-angle prostheses. Am J Otol 1998; 19:693–699. 17 Hüttenbrink KB, Zahnert T, Wüstenberg EG, Hofmann G: Titanium clip prosthesis. Otol Neurotol 2004;25:436–442. 18 Savvas E, Maurer J: Economic viability of stapes surgery in Germany. J Laryngol Otol 2008; 2:1–4.

J. Maurer Department for Otorhinolaryngolgy Head and Neck Surgery and Center for Hearing and Communication Katholisches Klinikum Koblenz Rudolf-Virchow-Strasse 7 DE–56076 Koblenz (Germany) Tel. +49 261 496 3111, Fax +49 261 496 3112 E-Mail j.maurer @ kk-koblenz.de  

 

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Böheim K (ed): Active Middle Ear Implants. Adv Otorhinolaryngol. Basel, Karger, 2010, vol 69, pp 72–84

Totally Implantable Active Middle Ear Implants: Ten Years’ Experience at the University of Tübingen H.P. Zenner · J. Rodriguez Jorge Department of Otolaryngology, Head and Neck Surgery, University of Tübingen, Tübingen, Germany

Abstract Active middle ear implants do not produce acoustic sounds but, rather, micromechanical vibrations. The stimulating signal does not leave the transducer as sound, but as a mechanical vibration, directly coupled to the auditory system and bypassing the normal route via air. In this paper, we review our experience with the TICA쏐 and the CarinaTM middle ear implants. Both are totally implantable and are coupled to the ossicular chain or to perilymph. The design requirements for electronic hearing implants for patients with conductive hearing loss differ from those for sensorineural hearing loss. Conductive hearing loss requires an implant that replaces impedance transformation and acts as an impedance transforming implant (ITI). In many respects, there are fewer demands on an ITI than on an electronic hearing aid for patients with sensorineural hearing Copyright © 2010 S. Karger AG, Basel loss.

International research efforts have yielded a number of options to improve the hearing of individuals with middle ear problems. These options supplement tympanoplasties and stapes surgery and include external bone anchoring hearing aids, developed by Tjellström and Bränemark [1–5] and the Japanese group of Suzuki and Yanagihara [6–14]. A subcutaneous, bone-anchoring, partially-implantable hearing system was also available for implantation (Audiant쏐) [15, 16]. The pathophysiological demands on such implants used for middle ear hearing loss can easily be overseen: only the lacking ability of the middle ear to adapt for impedance needs to be compensated [17, 18]. This places no particularly great demands on the amplification and electronic processing of the sound signal. For this reason, partially implanted devices (BAHA쏐, the Japanese middle ear implant (MEI) and Audiant) with their uncomplicated signal processing have been clinically available for several years. In addition, research has

led to the development of the TICA쏐 Total Implant for middle ear diseases, which is no more available clinically [19–21]. The situation is different for individuals with hearing loss due to inner ear problems. The demands placed on these implants are much greater. They range from individual frequency-specific amplification to improvement in speech comprehension and discrimination (also in the presence of background noise). Completely different therapeutic approaches may be used depending on whether (1) the outer hair cells are affected with inner hair cells being mostly intact, or (2) the inner hair cells are also affected. For the first and more common situation, the partially implantable electromagnetic floating mass transducer (FMT) system was developed by Ball [6] and is clinically available (MED-EL Vibrant쏐 Soundbridge). The first totally implantable piezoelectric system was developed by Zenner and Leysieffer (TICA쏐 LZ) for sensorineural hearing loss (SNHL) [6, 22–25], and was clinically available until 2000. At present, the Otologics Carina and the Envoy Esteem are totally implantable active middle ear implants (AMEIs) and are available for clinical use. To treat the second situation (inner hair cells also affected), cochlear implants and electric-acoustic implants are used more and more often [26].

Transducers

Leysieffer [27] gave an important overview of fundamental demands on an electromechanical transducer for implantable hearing aids compensating a sensorineural hearing loss. Middle ear implants (MEI) transform sound into amplified electrical signals. Unlike hearing aids, these signals are not reconverted into sound but are transformed into micromechanical vibrations. Instead of using a loudspeaker as conventional hearing aids do, the MEIs use an electromechanical transducer. The audio signal leaves the transducer not as sound (i.e. not as a compression air wave), but as a mechanical vibration (mass movement), which, by bypassing the air, is micromechanically coupled to the auditory system. The transducer is a vibrator rather than a loudspeaker. Benefits of Currently Available, Fully-Implantable MEI Systems • Good sound quality • Open external auditory canal • Low distortion (!0.5%, with hearing aids up to 5%) • Improved speech comprehension • Broad transmission bandwidth from 100 Hz to approximately 10 kHz for better speech comprehension and music appreciation • Risk of feedback is reduced • Unrestricted usage while working (e. g. in a dusty or hot environment), telephoning, showering, sleeping, swimming, and exercising

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• Auditory rehabilitation is possible without any demand on the patient’s manual dexterity; an advantage for persons compromised by motor and degenerative diseases of the hand • Hidden from view, thus preventing stigmatization Piezoelectric transducers (Envoy Esteem, TICA) consist of piezo-sensitive crystals which change their form in response to electrical current and produce vibrations. Electromagnetic devices use a magnet and a coil (Otologics Carina). Two anatomic localizations are used to implant present transducers: the tympanic cavity and the mastoid. The transducer should be placed as close as possible to the calvarium, ossicles, or oval window to ensure that the vibrations are as free as possible from any nearby elements [28, 29]. In the middle ear, about 2–3 mm of space is available for fitting the transducer, as is done with the Envoy 쏐 system. In the mastoid cavity, a space of 1 cm3 is usually available with a maximum diameter of 1 cm (Otologics Carina, TICA) [30, 31]. The advantage of a larger space is weighed against the possible disadvantage that a connector is also required.

Sensors

Depending on technical circumstances, a sound transducer, a microphone, may be implanted in one of several possible locations. These are listed below: (1) In the middle ear (2) At the tympanic membrane and/or the ossicles (3) In the wall of the auditory canal (4) In the mastoid (5) Under the skin of the calvaria The space available in the middle ear and in the mastoid should not be overestimated. Maassen et al. [30, 31] have illustrated quite well how many steps are required to adapt a sensor to the anatomy of the ear, using as an example a membrane sensor (TICA) implanted in the posterior auditory canal wall. For a piezoelectric sensor coupled to an ossicle (Envoy Esteem쏐) and intended for middle ear implantation, Weber et al. [32] discussed surgical problems related to minimally available space.

Acoustic Aspects

Oscillation Vibrational transducers produce no sound: their oscillations must be transformed into physiological oscillations in the middle and inner ear. Low excitation amplitudes

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suffice for middle ear hearing loss in which outer hair cells are intact because the signal can be amplified 100- to 1,000-fold by outer hair cells once the signal arrives in the cochlea [17, 18]. The situation is different with inner ear hearing loss and outer hair cell loss. In that case, the implant must amplify the travelling wave by a substantially greater amount so that the inner hair cells can be stimulated. According to physiological data on implants coupled to the ossicles, in the frequency range up to 1 kHz oscillations between 100 and 1,000 nm correspond to a subjective perception equivalent to 100 to 125 dB SPL in healthy ears. Above 1 kHz, in the octave range from 5 to 10 kHz, 5 to 50 nm suffice for the same auditory perception. At 10 kHz, an oscillation of 50 nm corresponds to a sound level of 140 dB SPL [27]. Dynamic Behavior If an implant is to faithfully reproduce a complex sound signal, it must work rapidly and should not lag in its response times [40]. Otherwise, an acoustic distortion can arise. Attack and decay times are important terms here. Upon biological burdening of the ears the attack and decay times for an excitation of !0.1 ms at 1 kHz should not exceed 1–3 ms if artifacts within the acoustic envelope are to be minimized. At higher frequencies, the starting amplitudes require that, as frequency increases, the speed should also increase rather than the amplitude decrease. At 10 kHz, this means that the maximum attack time should be 100 ␮s [27]. Distortion Distortion disrupts sound transmission and quality. Linear and nonlinear distortion are two different types. Linear distortion refers to the dependency of amplitude and phase-frequency responses on frequency. Because hearing is relatively insensitive to phase shifts, we do not need to consider phase-frequency responses further. However, this is not true for amplitude. A change in amplitude is perceived immediately as a change in volume. Resonances within perceptible ranges lead to amplitude distortions. Amplitude reductions with increasing frequency may be perceived as quiet signals. An optimal transducer should, therefore, ensure a flat profile over the entire frequency range, also when the ear is biologically stressed (e.g. in the case of an acute otitis media) and should show a minimal ripple effect of at most 8 3 dB. Resonances (endogenous frequencies) of more than 3 dB within the perceptible range should be avoided, if possible [27]. Nonlinear distortion refers to sound-level-dependent higher spectral components with sinusoidal input signals (total harmonic distortions), which can disrupt sound quality and speech discrimination. These may require frequent hearing aid adjustments and can amount to between 1 and 5% of the entire signal. Fredrickson et al. [33, 34] aimed for extremely low distortion products for implants, and his implant (Otologics쏐) reached values of between !0.5 and 1.1% (500 Hz to 10 kHz). Low distortion products of no more than 0.5% for frequencies between 50 Hz and 10 kHz are considered appropriate (at a sound level of 120–140 dB SPL).

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Technological Aspects

Power Source Issues regarding power consumption are relatively unimportant for partially implantable MEIs, but this is not the case for totally implantable ones. They must rely on power supplied by the implantable energy source. Their sizes and capacities are restricted. Modular Principle A hermetically sealed, implantable and detachable plug and socket connection between the sensor/convertor and the battery/audioprocessor is required. Therefore, if a defect occurs or an upgrade is required, only a single module need be exchanged without removing the entire implant.

Totally Implantable MEIs in SNHL

Piezoelectric TICA System according to Zenner and Leysieffer Implantation of the fully implantable electronic TICA LZ auditory systems [35] has been carried out from 1998 to 2000 in Europe for the surgical treatment of inner ear hearing loss [24, 25]. Today, a successor implant is under development. The implant allowed hearing improving surgery amongst individuals with SNHL without any external stigma. Due to the implantation of a membrane sensor in the external auditory canal wall an improvement in speech communication in the presence of background noise in some of the patients, and a return of auditory spatial orientation could be observed. This system, which has been developed since 1988, includes a piezoelectric transducer 8 mm in diameter (weight 0.4 g) that can be implanted into the mastoid [23, 29] and a sound sensor (membrane diameter 4.5 mm, weight 0.4 g) that can be implanted in the posterior osseous auditory canal in a transmastoidal and subcutaneous manner [36]. An implantable battery as well as an implantable, digitally programmable 3-channel audio processor [35] are used. Sound is picked up by an implanted membrane sensor, located very close to the tympanum [36]. The signal is coupled via the piezoelectric transducer to the incus. Its frequency response ranges from 50 to 10,000 Hz. Inner ear hearing loss can be compensated by up to 30 dB for frequencies up to 500 Hz, whereas from 2,000 Hz steeply sloping and severe hearing loss can also be compensated for. The TICA implant surgery includes the steps listed below. (1) Mastoidectomy: with coupling to the long side of the incus and a posterior tympanotomy, if necessary with exposure of the facial nerve. (2) Implantation of the microphone: a cavity is drilled in the posterior auditory canal wall for the microphone. After fitting the microphone, the microphone membrane is tightly fit in the posterior auditory canal wall, so that it can be covered by

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replacement of the auditory canal skin or using a fascial or perichondrial graft with subsequent re-epithelialization. (3) Implantation of the processor module: The processor module sits in a flat housing, similar to a cochlear implant housing, and is subcutaneously implanted retroauricularly onto the calvaria in the same way that a cochlear implant housing is. (4) Coupling of the transducer to the incus: Two methods are available for connecting the transducer to the incus: the coupling rod can be guided (a) to the incus body, or (b) through a posterior tympanotomy in the facial recess until it reaches the long process of the incus. If necessary, a bone cement or bone pate can be applied for fixing. A number of papers have been published that have assessed the TICA LZ components [29, 35, 36], performance in acute and chronic animal experiments [37, 38], and performance in a prospective clinical study of 20 patients [21, 24, 25, 38–40]. Audiological measurements revealed an improvement in monosyllable comprehension in 89% of the patients, which in the top 60% produced clear benefits. In all patients who had suffered losses in speech discrimination, this impairment was reduced and in 70% it was completely eliminated. In the background noise tests, the signal-to-noise ratios at the comprehension threshold were between –2 and +1 dB in 72% of the patients. Maximum amplification was frequency-dependent and was 40 dB at 2 kHz, 50 dB at 3 kHz, 55 dB at 4 kHz, whereby, on average, 20 dB were achieved. Spatial orientation was error-free in 89% of cases. Using the standardized Gothenburg profile, uniform values between 80 and 88% of the maximum point score were obtained in all patients for scores relating to comprehension and localization, as well as for social and medical well-being. It was apparent that, unlike wearers of conventional hearing aids, the reduction of social impairment and improvement in subjective well-being were valued just as highly as was the improvement in speech comprehension and spatial orientation. Electromagnetic System Carina according to Fredrickson In 1973, Fredrickson et al. [33, 34] embarked on a path upon which they have continued to this very day. They reported on the development of an electromagnetic system that was coupled to the intact ossicular chain (Otologics쏐). It is currently available as a fully implantable system (Otologics Carina). Upon implantation in the mastoid, similar to the TICA coupling to the ossicular chain occurs via a coupling rod that is attached to the incus body as a coupling element. The coupling element is driven by a co-implanted electromagnetic driver from which the coupling rod emanates. The driver is connected to a retroauricular subcutaneously implanted microphone. The implant is characterized by a distortion-minimized, level frequency response up until 10 kHz and can produce a level of 140 dB SPL, also adequate for severe inner ear hearing loss. Since Fredrickson et al. [33, 34] started in 1973, they have been able to carry out systematic developments on the system involving in vitro experiments, acute animal and chronic primate implantations, and short-term implantations in man. The indication field of CarinaTM system is highlighted in the chart (fig. 1). This graph shows the average of the audiometric profiles and their variability from 50

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adults with symmetric bilateral SNHL that received the Carina implant at the Department of Otolaryngology, Head and Neck Surgery, University of Tübingen. Carina’s middle ear transducer was positioned against the body of the incus; a transducer loading assistant was used during the surgery to ensure that the coupling to the ossicular chain was optimal without compromising normal middle ear function. A comparison of the average pre- and postoperative pure-tone audiograms shows a clinically nonsignificant decrease of 3 dB HL in the low frequencies and of 1 dB HL in the high frequencies (fig. 2). Figures 3 and 4 show the average functional gain achieved by the 50 Carina users. The average functional gain varies by frequency between 25 and 30 dB for audiometric test frequencies of 500–6,000 Hz. A significant improvement, up to 82% correct, in speech discrimination scores was obtained at the final test interval, as shown in figure 5. Piezoelectric System Esteem The Envoy Esteem is a CE-approved, fully implantable piezoelectric system. The main module is subcutaneously implanted behind the ear, and two cables extend into the middle ear. One is linked to a piezoelectric sensor, implanted to collect vibrations from the malleus. The other goes to a similar piezoelectric transducer, coupled to the stapes. The sensor signal is amplified and processed in the main module, which includes a battery. The amplified and processed signal is then transferred to the piezoelectric transducer that drives the stapes. Prospective study results are not yet available. A recent case report by Barbara et al. [41] showed that the surgical procedure is time consuming. Implantation may cause a deterioration in hearing thresholds; however, bone conduction thresholds

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may fully recover after some weeks. The authors reported postoperative hearing gain with the activated implant. The sound quality was described to be better than suggested from the audiologic results. General Indications for Totally Implantable MEIs A general indication for totally implantable MEIs is the treatment of SNHL. This application is particularly useful when a patient cannot be fit with a conventional hearing aid. Conventional hearing aid use can lead to several problems in some patients, as listed below. (1) Medically, earpieces can lead to intolerable • occlusion, • auditory canal inflammation, and • difficult placement of the earpiece in the ear canal for patients with motor disorders of the hand. (2) Audiologically, inadequate auditory rehabilitation can result if there is • unmanageable acoustic feedback (whistling), • intolerable distortion levels, • a surpassing of the comfortable level, or • inadequate speech comprehension, especially in occupational situations. (3) Stigmatization refers not so much to aesthetics but rather to an actual, and sometimes significant, discrimination against a visibly handicapped individual, particularly in occupational settings. This may include the following: • Discrimination at the workplace and when looking for work. • In their private lives, individuals may also become socially withdrawn. (4) Occupational reasons are important. In addition to reasons 1 through 3, which may contribute to occupational disabilities, difficulties experienced by specific occupational groups should also be considered. Doctors and nursing staff (stethoscopes), employees in call centers (ear plugs), and persons working in humid environments (the hearing aid falls out) may have additional difficulties with canal-occluding hearing aids. Working in places where heat and steam are produced may damage hearing aids. Persons with occupations involving sweating (hearing aids fall out), telephone work, speech communications (teachers, interpreters), or customer and negotiation-oriented services may not be successfully rehabilitated using hearing aids. When one or several reasons apply, rehabilitation with conventional hearing aids may be unsatisfying or even impossible in some patients. If specific indications apply, some affected individuals may now be helped using amplifying implants that are appropriate, adequate and indeed necessary. Specific Indications Each implant has its own specific audiologic indications that are described for each implant. Because partially implantable MEIs can provide acoustic advantages over conventional hearing aids, partially implantable implants are indicated for patients

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complaining of inadequate sound quality, feedback and distortion when using conventional hearing aids. For fully implantable systems, there is a wider range of indications. Fully implantable implants offer advantages in everyday life (swimming, showering, wind noise) and for rehabilitation in certain occupational groups (teachers, especially PE teachers, cooks, chairpersons, representatives, call center workers, telephone clerks, etc.). Of particular importance is the absence of stigmatization, which explains the markedly reduced social withdrawal of those fit with fully implantable devices. The often unperceived depression of hard of hearing individuals can be attributed to social withdrawal from human communication, or indeed occupational discrimination. Thus, a successful social reintegration, whether it be at the workplace or in private life, represents the real clinical benchmark. Screening Criteria for a MEI in SNHL The decision to indicate an implant for an adult can be checked against three fundamental criteria listed below: (1) Similar to the National Guidelines of the German Society of Otolaryngology, Head and Neck Surgery (‘AWMF-Leitlinie Hörgeräteversorgung’) for conventional hearing aids, the pure tone audiometric hearing loss may be recommended to be at least 30 dB in the better ear in at least one of the audiological test frequencies between 500 and 3,000 Hz in order for an implantation to be indicated. Until 1 kHz, the hearing loss is suggested not to exceed 30 dB. Furthermore, the comprehension rate for monosyllabic words should not be greater than 80% with the better ear at a sound level of 65 dB. (2) Depending on the implant, there are a number of other specific audiological criteria that should be considered. (3) Rehabilitation with conventional hearing aids should be inappropriate or unsatisfying for medical, psychosocial, audiologic, or occupational reasons. General Contraindications for Fully Implantable MEIs in SNHL • Fully implantable MEIs may not be implanted into children • Fluctuating or rapidly progressing hearing loss • Deafness in one ear • Disorders or malformations of the auditory canal, middle ear, petrous part of the temporal bone, or the cerebellopontine angle that might stand in the way of an implantation • Irregular course of the facial nerve • Previous middle ear surgery • Retrocochlear hearing loss or auditory neuropathy • Organic brain disease • Psychiatric disease • Restrictions on anesthesia or ability to perform surgery • Simultaneous intake of ototoxic medication

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Future Perspectives Clinical results, improved surgical techniques, and further technological developments lead us to expect that the indication for MEIs will be extended to severe inner ear hearing loss in the future. At the same time, further developments in cochlear implants and electric-acoustic implants for treating residual hearing at low frequency ranges cannot be excluded. In the future, the full range of inner ear hearing loss conditions may be treated using electronic implants, whether they are cochlear implants or MEIs. Theoretically, this means that almost all forms of SNHL would be surgically treatable.

Fully Implantable MEI for Inoperable Middle Ears and Mixed Hearing Losses

Fully Implantable Piezoelectric Implant TICA according to Leysieffer-Zenner for Stapes or Perilymph Coupling As early as 2001, the research group of Zenner and Leysieffer [19–21] modified their fully implantable, piezoelectric TICA implant for use in middle ear hearing loss, especially in mixed hearing loss. For this purpose, a coupling rod was guided via a posterior tympanotomy to the oval window niche. Using a coupling element derived from the Tübingen titanium prosthesis (TTP 쏐, Kurz, Dusslingen), attached to the coupling rod of the TICA in the absence of the incus, a signal could be applied directly to the stapes head. If the stapes suprastructures were also missing, the coupling rod served as an artificial incus in the oval niche upon which the piston prosthesis was attached and which activated perilymph through a perforation in the footplate [19, 20]. Because the TICA includes an implantable sensor in the auditory canal, the posterior auditory canal wall must be intact. At present, the TICA is no more clinically available. A successor implant is currently under development. Fully Implantable Electromagnetic Implant Otologics Carina for Round Window, Perilymph and Stapes Coupling Similar to the TICA, the Carina implant may be indicated for patients with middle ear problems or mixed hearing loss. Carina’s coupling rod may be coupled to the round window, to the stapes head, or to the vestibulum via a piston prosthesis. Indications. The main indications are stapes otosclerosis with a substantial involvement of the inner ear (when hearing loss cannot be adequately treated by stapes surgery alone), and severe middle ear conditions, such as tympanic sclerosis.

Closing Remarks

Weighing the benefits and risks of surgery versus rehabilitation with conventional hearing aids is not new for an ENT physician. The option to use surgery and hearing aids has been available to otologists for the last 50 years. This applies particularly to

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stapes fixation and ossicular chain disruptions, both of which can be treated with either surgery or hearing aids. In the future, there will be a growing need to weigh the options of surgery and hearing aids for inner ear hearing loss as well. The introduction of microsurgery to the ENT surgeon’s therapeutic arsenal for inner ear hearing loss nevertheless appears surprising for some, given the perception that hearing aids are a viable option for all patients as an adequate treatment modality. However good current hearing aids are, they can only help a proportion of the patients who need them. There is another group of patients who cannot be helped by hearing aids. Even recommendations from those who benefit audiologically from hearing aids may sometimes be inappropriate. Stigmatization from hearing aids can lead to discrimination and some patients may become socially and occupationally withdrawn. Should doctors and health insurance agencies have the right to dictate that a stigma be tolerated by patients when this stigma may lead to unjustifiable discrimination in the world of the hearing? Therapy with approved electric-acoustic implants represents a treatment option with proven efficacy. They are regulated medical devices, which, as in the pharmaceutical industry, can only be approved by the notified European body or by the US FDA after efficacy and safety have been demonstrated.

References 1 Branemark PI, et al: Osseointegrated implants in the treatment of the edentulous jaw: experience from a 10-year period. Scand J Plast Reconstr Surg Suppl 1977; 16:1–132. 2 Tjellstrom A, Hakansson B: The bone-anchored hearing aid: design principles, indications, and long-term clinical results. Otolaryngol Clin North Am 1995; 28:53–72. 3 Tjellström A, Granstrom G: Long-term follow-up with the bone-anchored hearing aid: a review of the first 100 patients between 1977 and 1985. Ear Nose Throat J 1994; 73:112–114. 4 Tjellström A, Lindström J, Hallén O, Albrektsson T,  Brånemark PI: Osseo-integrated titanium implants in the temporal bone: a clinical study of bone-anchored hearing aids. Am J Otol 1981; 2: 304–310. 5 Tjellström A: Vibratory Stimulation of the Cochlea through a Percutaneous Transducer. Adv Audiol. Basel, Karger, 1988, vol 4, pp 44–50. 6 Ball G, Maxfield B: Floating mass transducer for middle ear applications. Sec Intl Symp Electr Impl 1996;8.

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7 Suzuki J, Kodera K, Akai S, et al: Still further clinical observation of MEI implanted patients; in Yanagihara N, Suzuki J (eds): Transplants and Implants in Otology II. Amsterdam/New York, Kugler, 1992, pp 387–390. 8 Suzuki J,  Kodera K,  Nagai K,  Yabe T: Long-term clinical results of the partially implantable piezoelectric middle ear implant. Ear Nose Throat J 1994; 73:104–107. 9 Suzuki J, Kodera K, Nagai K, Yabe T: Partially implantable piezoelectric middle ear hearing device. Long-term results. Otolaryngol Clin North Am 1995; 28:99–106. 10 Suzuki J,  Kodera K,  Suzuki M,  Ashikawa H: Further clinical experiences with middle-ear implantable hearing aids: indications and sound quality evaluation. ORL J Otorhinolaryngol Relat Spec 1989;51:229–234. 11 Suzuki J, et al: Early Studies and the History of Development of the Middle Ear Implant in Japan. Adv Audiol. Basel, Karger, 1987. 12 Suzuki J, et al: Principle Construction and Indication of the Middle Ear Implant. Adv Audiol. Basel, Karger, 1988.

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13 Yanagihara N, et al: Implantable hearing aid: report of the first human applications. Arch Otolaryngol Head Neck Surg 1987;113:869–872. 14 Yanagihara N, et al: Efficacy of the Partially Implantable Middle Ear Implant in the Middle and Inner Ear Disorders. Adv Audiol. Basel, Karger, 1988. 15 Hough J, Himelick T, Johnson B: Implantable bone conduction hearing device: Audiant bone conductor: update on our experiences. Ann Otol Rhinol Laryngol 1986; 95: 498–504. 16 Hough J, et al: Experiences with implantable hearing devices and a presentation of a new device. Ann Otol Rhinol Laryngol 1986; 95: 60–65. 17 Zenner H: Physiologische und biochemische Grundlagen des normalen und des gestörten Gehörs. Oto-Rhino-Laryngologie in Klinik und Pra xis. Stuttgart, J Helms, 1994. 18 Zenner HP, Leysieffer H: Active electronic cochlear implants for middle and inner ear hearing loss – a new era in ear surgery. I. Basic principles and recommendations on nomenclature. HNO 1997; 45: 749–757. 19 Lehner R, et al: Cold deformation elements for attaching an implantable hearing aid transducer to ear ossicles or perilymph. HNO 1998;46:27–37. 20 Zenner H, et al: Ein implantierbares Hörgerät für Innenohrschwerhörigkeiten. Kurzzeitimplantation von Mikrophon und Wandler. HNO 1998; 45. 21 Zenner HP, Leysieffer H: Total implantation of the Implex TICA hearing amplifier implant for high frequency sensorineural hearing loss: the Tubingen University experience. Otolaryngol Clin North Am 2001;34:417–446. 22 Leysieffer H, et al: A totally implantable hearing aid for inner ear deafness: TICA LZ 3001. HNO 1998; 46:853–863. 23 Leysieffer H, et al: An implantable piezoelectric hearing aid transducer for inner ear hearing loss. I. Development of a prototype. HNO 1997; 45: 792– 800. 24 Zenner HP, Leysieffer H: Totally implantable hearing device for sensorineural hearing loss. Lancet 1998;352:1751. 25 Zenner HP, et al: First implantation of a totally implantable electronic hearing aid in patients with inner ear hearing loss. HNO 1998;46:844–852. 26 Laszig R, Klenzner T: Cochlear implant in residual hearing. HNO 1997; 45:740–741.

27 Leysieffer H: Principle requirements for an electromechanical transducer for implantable hearing aids in inner ear hearing loss. I. Technical and audiologic aspects. HNO 1997; 45:775–786. 28 Lehnhardt E: Intracochlear placement of cochlear implant electrodes in soft surgery technique. HNO 1993;41:356–359. 29 Leysieffer H, et al: An implantable piezoelectric hearing aid transducer for inner ear deafness. II. Clinical implant. HNO 1997; 45:801–815. 30 Maassen MM, et al: Adjusting the geometry of implantable hearing aid components to human temporal bone. I. Electromechanical transducer. HNO 1997;45:840–846. 31 Maassen MM, et al: Adjusting the geometry of implantable hearing aid components to human temporal bone. II. Microphone. HNO 1997;45:847–854. 32 Weber B, et al: Untersuchung zu einem implantierbaren Hörgerät mit piezoelektronischem Aktorund Sensorsystem. HNO 1999; 47. 33 Fredrickson J, Tomlinson D, David E, Odvist M: Evaluation of an electromagnetic implantable hearing aid. Can J Otolaryngol 1973;2:53–62. 34 Fredrickson JM, Coticchia JM, Khosla S: Ongoing investigations into an implantable electromagnetic hearing aid for moderate to severe sensorineural hearing loss. Otolaryngol Clin North Am 1995; 28: 107–120. 35 Maassen MM, et al: Functional long-term results after open cholesteatoma surgery and ossiculoplasty with allogenic ossicles in adulthood. Laryngorhinootologie 1998; 77:74–81. 36 Leysieffer H, Muller G, Zenner HP: An implantable microphone for electronic hearing aids. HNO 1997; 45:816–827. 37 Plinkert PK, et al: In vivo studies of a piezoelectric implantable hearing aid transducer in the cat. HNO 1997;45:828–839. 38 Weber B: Habilitationsschrift, 1997. 39 Zenner H, et al: Patient selection for total implantation of TICA LZ 3001. Am J Otol 2000. 40 Maassen MM, et al: Safe and reliable sound threshold measures with direct vibration of the ossicular chain. Laryngoscope 2004; 114:2012–2020. 41 Barbara M, Manni V, Monini S: Totally implantable middle ear device for rehabilitation of sensorineural hearing loss: preliminary experience with the Esteem, Envoy. Acta Otolaryngol 2009; 129:429–432.

H.P. Zenner Department of Otolaryngology, Head and Neck Surgery, University of Tübingen Elfriede-Aulhorn-Strasse 5 DE–72076 Tübingen (Germany) Tel. +49 7071 29 88001, Fax +49 7071 29 5674 E-Mail hans-peter.zenner @ med.uni-tuebingen.de  

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Author Index

Ball, G.R. 1 Baumgartner, W.-D. 38 Beutner, D. 27 Böheim, K. 38, 51 Bornitz, M. 32 Colletti, V. 38 Cremers, C. 14 Ernst, A. 20 Hagen, R. 38 Hüttenbrink, K.B. 27, 32

Opie, J. 38 Pok, S.M. 51 Reiss, S. 38 Rodriguez Jorge, J. 59 Savvas, E. 59 Schlögel, M. 38, 51 Snik, A. 14 Todt, I. 20 Verhaegen, V. 14

Lenarz, T. 38 Maurer, J. 59 Mlynski, R. 38 Mojallal, H. 38 Mulder, J. 14 Müller, J. 38

Wagner, F. 20 Wagner, J. 20 Zahnert, T. 27, 32 Zenner, H.P. 59

Subject Index

Abbreviated Profile of Hearing Aid Benefit (APHAB), Esteem device assessment  67, 68, 70 AP, see Audio processor APHAB, see Abbreviated Profile of Hearing Aid Benefit Audiant device  72 Audio processor (AP), Soundbridge  8, 9, 44, 53 BAHA, see Bone-anchored hearing aid Bone-anchored hearing aid (BAHA)  47, 72 Bone conduction hearing aid  40 Carina device, see also Totally implantable devices indications  24 inoperable middle ears and mixed hearing loss  82 regulatory approval  3 sensorineural hearing loss  77–79 Cartilage shielding, floating mass transducer  34–36 Clip-partial ossicular replacement prosthesis (PORP)  30 Cost-utility ratio, middle ear implant assessment  16 Esteem device, see also Totally implantable devices battery life  69

implant insertion  66 incus disarticulation  69 indications  24, 25, 63, 64 patient experience  66–70 patient preparation  64, 65 piezoelectric transducers and driver  60–62, 74 principles  59, 60 regulatory approval  3 sensorineural hearing loss  78 sound processor  63 surgical technique  64 EuroQol, middle ear implant assessment  15 Floating mass transducer (FMT) cartilage shielding  34–36 incus placement  22, 52 invention  4–6 oval window placement with titanium holder  27–30 round window placement  23, 41, 43 stapes footplate placement  32–37 technical aspects 7, 8 FMT, see Floating mass transducer Footplate, see Stapes footplate Funding, middle ear implant development  3 GBI, see Glasgow Benefit Inventory Glasgow Benefit Inventory (GBI), middle ear implant assessment  15, 17, 18

Health-related quality of life (HR-QoL), middle ear implants  14–18 Health Utility Index, middle ear implant assessment  15 Hearing aid acceptance  2, 3 historical perspective  1, 2 HR-QoL, see Health-related quality of life Incus disarticulation for Esteem device  69 floating mass transducer placement  22, 52 Indications, active middle ear implants  20–25 International Outcome Inventory for Hearing Aids (IOI-HA), middle ear implant assessment  16–18 IOI-HA, see International Outcome Inventory for Hearing Aids NCIQ, see Nijmegen Cochlear Implant Questionnaire Nijmegen Cochlear Implant Questionnaire (NCIQ), middle ear implant assessment  15, 17, 18 Oval window, floating mass transducer placement with titanium holder  27–30 Patient selection, active middle ear implants  25 Piezoelectric transducer (PZT), Esteem device  60–62, 74 PORP, see Clip-partial ossicular replacement prosthesis PZT, see Piezoelectric transducer QALY, see Quality-adjusted life years QoL, see Quality of life Quality-adjusted life years (QALYs), middle ear implant assessment  15–17 Quality of life (QoL), middle ear implants  14–18 Round window, floating mass transducer placement  23, 41, 42 Sensorineural hearing loss (SNHL) active middle ear implant indications  20–22

Subject Index

totally implantable devices Carina device  77–79 Esteem device  78 indications general  80 specific  80, 81 prospects  82 screening criteria  81 totally implantable cochlea amplifier  76, 77 Vibrant Soundbridge study data analysis  53 device fitting  53 overview  51, 52 study design  52 subjects  53 testing  53–57 SF-36, see Short Form 36 Short Form 36 (SF-36), middle ear implant assessment  15, 17 SNHL, see Sensorineural hearing loss Soundbridge, see Vibrant Soundbridge Sound processor, Esteem device  63 Speech recognition, Vibrant Soundbridge outcomes  22, 44–47, 57 Stapes footplate, floating mass transducer placement  32–37 Stapes incus, see Incus TI devices, see Totally implantable devices TICA, see Totally implantable cochlea amplifier TORP, see Total ossicular replacement prosthesis Total ossicular replacement prosthesis (TORP)  5 Totally implantable cochlea amplifier (TICA)  5, 73, 76, 77, 82 Totally implantable (TI) devices, see also Carina device; Esteem device acoustics distortion  75 dynamic behavior  75 oscillation  74 benefits  73, 74 inoperable middle ears and mixed hearing loss Carina device  82 totally implantable cochlea amplifier  82

87

Totally implantable (TI) devices (continued) modularity  76 overview  72, 73 power source  76 prospects  11, 82, 83 sensorineural hearing loss Carina device  77–79 Esteem device  78 indications general  80 specific  80, 81 prospects  82 screening criteria  81 totally implantable cochlea amplifier  76, 77 sensors  74 transducers  73, 74 Vibrant Soundbridge (VSB) audio processor  8, 9 conductive and mixed hearing loss multicenter study aided benefit  44 audio processor programming  44 complications  46, 48, 49 evaluation  43, 44 residual hearing changes  46

88

round window vibroplasty  43 speech recognition  44–47 study design  43 subjective benefits  46, 48 subjects  41–43 floating mass transducer, see Floating mass transducer indications  20–23 invention  4–6 middle ear effusion effects  35 overview  6 prospects  11 regulatory approval  3–4 sensorineural hearing loss study data analysis  53 device fitting  53 overview  51, 52 study design  52 subjects  53 testing  53–57 speech testing  22 theory of operation  9, 10 vibrating ossicular prosthesis  8, 9, 22 Vibrating ossicular prosthesis (VORP), Soundbridge  8, 9, 22 VORP, see Vibrating ossicular prosthesis VSB, see Vibrant Soundbridge

Subject Index