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A Pilot Study of the Safety and Performance of the Otologics Fully Implantable Hearing Device: Transducing Sounds via the Round Window Membrane to the Inner Ear

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The safety and performance of the Otologics fully implantable hearing device were assessed in adult patients with mixed conductive and sensorineural hearing loss. The subcutaneous microphone of this fully implantable device picks up ambient sounds,
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  Fax +41 61 306 12 34E-Mail karger@karger.chwww.karger.com  Original Paper Audiol Neurotol 2009;14:172–180 DOI: 10.1159/000171479 A Pilot Study of the Safety and Performance of the Otologics Fully Implantable Hearing Device: Transducing Sounds via the Round Window Membrane to the Inner Ear P.P. Lefebvre a  C. Martin c  C. Dubreuil d  M. Decat b  A. Yazbeck e  J. Kasic e  S. Tringali d   a  Department of Otorhinolaryngology, University of Liège, Liège , and b  Department of Otorhinolaryngology, Catholic University of Louvain, Brussels , Belgium; c  Department of Otorhinolaryngology, Hôpital Bellevue, Saint Etienne , and d  Department of Otorhinolaryngology, Lyon Sud Hospital, Lyon , France; e  Otologics LLC, Boulder, Colo. , USA   hearing loss were implanted with the Otologics fully im-plantable hearing device. Pre- and postoperative air con-duction, bone conduction, as well as aided and unaided thresholds and speech scores were measured. Results:  No significant differences between preoperative and postop-erative pure-tone averages were noted. Average improve-ment ranged from 19.16 to 35.8 dB of functional gain across audiometric frequencies with a mean of 26.17 8  5.15 dB. Long-term average functional gain at 12 months was 20.83 8  6.22 dB. Word recognition scores demonstrated signifi-cant differences between unaided and implant-aided condi-tions. Conclusions:  Preliminary results of this trial of the Oto-logics fully implantable hearing device provide evidence that this fully implantable device is capable of efficiently transferring the sound to the inner ear via the round window membrane in patients with mixed hearing loss. Copyright © 2008 S. Karger AG, Basel Key Words Round window membrane   Conductive and sensorineural hearing loss   Fully implantable hearing aid Abstract Objectives:  The safety and performance of the Otologics fully implantable hearing device were assessed in adult pa-tients with mixed conductive and sensorineural hearing loss. Methods:  The subcutaneous microphone of this fully im-plantable device picks up ambient sounds, converts them into an electrical signal, amplifies the signal according to the user’s needs, and sends it to an electromechanical transduc-er. The transducer tip is customized with a prosthesis in order to be in contact with the round window membrane and is protected by fascia; this translates the electrical signal into a mechanical motion that directly stimulates the round win-dow membrane and enables the user to perceive sound. The implanted battery is recharged daily via an external charger and the user can turn the implant on and off as well as adjust the volume with a hand-held remote control. In this pilot study, 6 patients with mixed conductive and sensorineural Received: August 15, 2007 Accepted after revision: July 9, 2008 Published online: November 13, 2008  NeurotologyAudiology  Philippe P. Lefebvre, MD, PhD Department of Otorhinolaryngology CHU de Liège BE–4000 Liège (Belgium) Tel. +32 4366 8891, Fax +32 4366 7525, E-Mail pp.lefebvre@ulg.ac.be © 2008 S. Karger AG, Basel1420–3030/09/0143–0172$26.00/0 Accessible online at:www.karger.com/aud J. Kasic and A. Yazbeck are employees of Otologics LLC.   Fully Implantable Hearing Aid on the Round Window Membrane Audiol Neurotol 2009;14:172–180  173  Introduction Over the last decades, despite ongoing advances in speech processing technology and miniaturization of hardware, researchers have continued to examine alter-native methods to conventional hearing aids to stimulate and provide amplified sound to the impaired hearing sensory organ [Suzuki et al., 1985; Ko et al., 1995; Mani-glia et al., 1997; Fisch et al., 2001]. Implantation of middle ear devices for the rehabilitation of sensorineural hearing losses has become part of routine clinical practice in Eu-rope and more recently in the United States [Snik et al., 2001]. The Vibrant Soundbridge was the first device to be used routinely after commercial release in February 1998 in Europe and August 2000 in the United States. The Vi-brant Soundbridge possesses an external auditory pro-cessor which transfers information to the implant which in turn transfers energy to the long process of the incus by a vibrating floating mass [Fisch et al., 2001]. The Mid-dle Ear Transducer (MET) from Otologics LLC is also available on the market in the European Union as a semi-implantable device. It is similarly composed of an exter-nal part containing the microphone, the battery and the sound processor, and of an internal part implanted in the middle ear whose vibrator is connected to the body of the incus [Kasic and Fredrickson, 2001]. Over the past 10 years, these semi-implantable devices have proven their efficacy and safety. However, the ultimate goal is to pro- vide the patient with a fully implantable device to simul-taneously meet the patient’s needs for comfort, cosmetics and hearing [Zenner et al., 2004]. A fully implantable hearing aid consists of a sound receptor (microphone), an electronic amplifier including active audiosignal pro-cessing, an electromechanical transducer (actuator) for stimulating the ear by vibration, and an energy source. The energy source may be either a primary cell or a re-chargeable (secondary) cell. Until recently, the transducers of the various devices have been attached to the various parts of the ossicular chain. It has therefore been mandatory to implant a rath-er normal middle ear with a normally functioning os-sicular chain. Animal experiments have demonstrated the potential of delivering sounds directly to the inner ear  via the round window membrane. Wever and Lawrence [1992] have shown that the acoustic stimulation of the oval window and round window has equivalent effects on cochlear potentials when sound was delivered at either entrance to the cochlea. Dumon et al. [1995] have con-firmed the utility of round window stimulation by the measurement of acoustically evoked potentials compared to auditory evoked potentials induced by piezoelectric vi-brators implanted on the round window of guinea pigs. Recently, Colletti et al. [2006] have reported successful direct sound transfer to the inner ear through the round window membrane using the floating mass of the Vi-brant Soundbridge. The first fully implantable device available for senso-rineural and mixed hearing loss patients has the CE mark and has been launched by Otologics, LLC across Europe. This device can be placed in the middle ear space in a number of configurations to allow contact with either the ossicular chain, if there is a mobile footplate, or the round window membrane. This paper reports the first results of performance and safety of the pilot clinical trial of the Otologics fully implantable hearing device with place-ment of the transducer on the round window mem-brane.  Materials and Methods Subjects Six patients were implanted in this pilot study in 4 European centers (2 in France and 2 in Belgium); centers with experience in implanting the fully implantable device for sensorineural hearing loss were chosen, in order to ensure a good placement of the trans-ducer. Only adults (18 years old) with stable mixed conductive and sensorineural hearing loss and no signs or symptoms of retroco-chlear, central auditory or functional components were included. Patients with medical contraindications to surgery or middle ear implantation or unrealistic expectations of device benefit were also excluded. This study was approved by the local ethics com-mittees. Pure-tone averages were derived by averaging the preop-erative air conduction pure-tone thresholds at 500, 1000, 2000 and 4000 Hz. Surgical Procedure The patients entering the study were implanted directly after identification. Implantation of the MET ossicular stimulator was performed through a postauricular incision with a posterior tym-panotomy to expose the round window niche. The superior and external ridge of the niche was drilled using a skeeter drill to ex-pose the round window membrane. The round window mem-brane movement was checked by the mobilization of the stapes or of the long process of the incus when a stapedotomy piston was in place. The tip of the transducer was adapted by clipping a modi-fied TORP to the end of the transducer, the other end of the TORP being placed on a fascia graft protecting the round window mem-brane. Intraoperative auditory brainstem response was recorded to ensure the correct placement of the prosthesis tip. A plain X-ray of the skull was taken after surgery to check the positioning of the  various components of the implant ( fig. 1 ). The implant was acti- vated 8 weeks after surgery. The internal audio processor was pro-grammed according to the patients’ needs, using a fitting algo-rithm based on implant thresholds and uncomfortable loudness levels and the desired sensation level (DSL i/o) targets.   Lefebvre /Martin /Dubreuil /Decat /Yazbeck /Kasic /Tringali Audiol Neurotol 2009;14:172–180 174   Audiological Tests Air and bone conduction thresholds were obtained pre- and postoperatively, with the last preoperative measurement being made no more than 2 weeks prior to surgery. Follow-up testing was performed 3–6 months after surgery and again at 12 months after surgery. Additionally, sound field thresholds (aided and un-aided) and monaural speech recognition scores using disyllabic word lists were measured.   APHAB Scores APHAB questionnaires [Cox and Alexander, 1995] were ad-ministered at 12 months of follow-up in order to assess the pa-tients’ satisfaction with the device. The APHAB score was as-sessed for situations with the implant switched on and off. Results Intraoperative Auditory Evoked Potentials After the placement of the transducer with its TORP-like prosthesis tip on the round window membrane and fascia, the implant was connected to a stimulator and au-ditory brainstem responses were recorded. Figure 2 shows an example of the auditory brainstem response waves re-corded during surgery obtained for decreasing stimuli, indicating that the coupling of the vibrator to the inner ear was efficient.  Safety Figures 3 and 4 show the pre- and postoperative air and bone conduction for each patient evaluated in this study. No significant change was observed in air or in bone conduction, indicating minimal trauma to the mid-dle and to the inner ear. Placement of the transducer in contact with the round window membrane appears to be safe in all individual patients. Air and bone conduction levels remained constant at 12 months of follow-up.   Fig. 1.   a  Diagram of a peroperative view of the positioning of the transducer at the level of the round window membrane.  b  Plain X-ray of the skull showing the  various components of the Carina device: microphone, capsule containing the elec-tronic and the battery, and the trans-ducer.     C   o    l   o   r   v   e   r   s    i   o   n    a   v   a    i    l   a    b    l   e   o   n    l    i   n   e 0.24 µV60 dBV60 dB60 dB60 dB60 dB50 dB50 dB50 dB40 dBVVV40 dB30 dB2.00 ms   Fig. 2.  Example of peroperative auditory brainstem response re-corded during surgery with the energy transmitted to the inner ear by the transducer whose tip is placed against the round win-dow membrane. ab   Fully Implantable Hearing Aid on the Round Window Membrane Audiol Neurotol 2009;14:172–180  175 Patient 5250 500 750 1k 1.5k 2k 3k 4k 6k 8k Hz0102030405060708090100110120         d        B Patient 6250 500 750 1k 1.5k 2k 3k 4k 6k 8k Hz 0102030405060708090100110120         d        B ACBC0102030405060708090100110120250 500 750 1k 1.5k 2k 3k 4k 6k 8k Hz         d        B Patient 40102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 20102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 30102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 1   Fig. 3.  Air and bone conduction threshold (dB HL) measured preoperatively for the 6 patients. AC = Air con-duction; BC = bone conduction. Fig. 4.  Air and bone conduction threshold (dB HL) measured postoperatively for the 6 patients. AC = Air con-duction; BC = bone conduction. 250 500 750 1k 1.5k 2k 3k 4k 6k 8k Hz0102030405060708090100110120         d        B Patient 1ACBC0102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 60102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 30102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 20102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 40102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 5 3 4   Lefebvre /Martin /Dubreuil /Decat /Yazbeck /Kasic /Tringali Audiol Neurotol 2009;14:172–180 176   Aided Thresholds and Functional Gain Although patients in the study had varying degrees of hearing loss, they demonstrated essentially the same aid-ed thresholds, i.e. 37.50 8  7.29 dB HL (n = 6) at frequen-cies up to 3000 Hz ( fig. 5 ). A gain at threshold (function-al gain) may be calculated by determining the difference between the aided postoperative and unaided preopera-tive sound field thresholds. Average improvement ranged from 19.16 to 35.8 dB of functional gain across audiomet-ric frequencies with a mean of 26.17 8  5.15 dB. At 12 months, the average gain dropped to 20.83 8  6.22 dB.  Speech Recognition Speech recognition scores using disyllabic word lists in French obtained for the 6 patients are shown in figure 6 . The 6 patients show a drastic increase in speech percep-tion of 63.33 8  32.04% (n = 6) at 65 dB SPL ( fig. 6 , 7 ) postoperatively. Long-term results show that at 12 months of follow-up, the speech perception scores average at 36.25 8  46.07%.   APHAB Scores Figure 8 shows the summary of the long-term follow-up APHAB scores for 5 patients. A difference of 10% or more in any of the 3 subscales Ease of Communication, Reverberation and Background Noise is considered a sig-nificant difference between different conditions at the 95% confidence level [Cox and Alexander, 1995]. For the last subscale, Aversiveness to Sound, only a small or no difference is expected. Lower values denote more favor-able assessments in all subscales. Patient No. 1 reported improvement of communica-tion in 3 subscales by 29–63 percent points but deteriora-tion in the Aversiveness to Sound subscale, when using the Carina device. In patient No. 2, there is an improve-ment by 44 percent points in the Ease of Communication subscale, but only a small improvement in Reverberation and a deterioration in Background Noise and Aversive-ness to Sound scores. Patient No. 3 exhibits little im-provement with the implant, however patients 4 and 5 show good improvement in at least 3 scores.   Fig. 5.  Free-field pure-tone threshold (dB HL) measured postoperatively in unaided (filled square) and aided conditions (open square) for the 6 patients. 0102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 10102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 60102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 20102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 40102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 3UnaidedAided0102030405060708090100110120         d        B 250 500 750 1k 1.5k 2k 3k 4k 6k 8k HzPatient 5
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