Semi-implantable electromagnetic middle ear hearing device for moderate to severe sensorineural hearing loss

Effects of a particle placed on the ossicles for microphoneless cochlear implant design

In a typical cochlear implant design, the ambient sound is detected via a microphone and the transmission unit of the implant is placed at the back of the auricle. However, this design has several drawbacks. Firstly, the subject cannot bath or swim comfortably with the microphone unit on, and secondly having an external attached unit which may be visible is cosmetically disturbing. Herein, the idea is to explore obtaining the acoustic signals that would directly drive the cochlear nerves, without using a microphone, in which only the vibrations of the ossicles are employed. Thus, the natural filter caused by the anatomy of the ear may be maintained. The proposed method is to place or attach a micro-electro-mechanical-system (MEMS) type of tiny and lightweight accelerometer to sense or detect the vibrations of ossicles, namely malleus, incus and stapes. A quick analysis or first-thought revealed that physically longer extension of the incus is the most suitable and/or convenient place to attach such a sensor. The model adopted has been optimized to match the amplitude and phase response of the human ear from a system analysis point of view. Some simulation experiments had been done to study and understand the possible loading effects of placing a sensor on the incus. Purpose of the simulations is testing the feasibility before the very difficult surgical procedures. Preliminary results indicate that placing a sensor of weight up to 36 mg does not seriously affect the amplitude and the phase response of the ear. This study is yet another example of how simulations of physiological systems can be advantageous and facilitating in the design of biomedical systems.

The development of active middle ear implants: A historical perspective and clinical outcomes

Objective s

Energy emitting, active middle ear implants (aMEI) have taken more than two decades of research to reach technological sophistication, medical safety, and regulatory approval to become a powerful tool in treating sensorineural, conductive, and mixed hearing loss. The present review covers this era.

Data Source

Literature found from searching Pubmed (MEDLINE); EMBASE, SciSearch, German Medical Science Journals and Meetings, and The Cochrane Library; and published as of February 2017. Study bibliographies were hand-searched to find further materials.

Methods

A systematic literature review was conducted to identify studies evaluating the safety, efficacy, effectiveness, and subjective outcomes of partially implantable aMEIs. Data were extracted on systems with regulatory approval and summarized narratively. Meta-analyses were conducted for aMEIs with more than 25 publications. Study selection, data extraction, and quality appraisal for quantitative data synthesis was carried out by two reviewers.

Results

Four hundred thirty-one studies included in narrative synthesis describe that albeit good audiological outcomes, clinical safety and (dis)investment are major barriers to continued market access. The synthesised risk of adverse events was three fold with the MET than with the VIBRANT SOUNDBRIDGE. With the latter system, audiological outcomes were stable and similar for all indications and age groups.

Conclusion

To date, the majority of the literature covers the clinical application of the VIBRANT SOUNDBRIDGE system as it is applicable to a wide range of otologic and audiological conditions, particularly with the introduction of couplers to extend its clinical reach. The MAXUM and MET still have to find their way into surgical routine.Level of Evidence.

The envoy® totally implantable hearing system, st. Croix medical

The Totally Implantable Envoy® System is currently undergoing clinical trials in both the United States and Europe. The fully implantable hearing device is intended for use in patients with sensorineural hearing loss. The device employs piezoelectric transducers to sense ossicle motion and drive the stapes. Programmable signal processing parameters include amplification, compression, and variable frequency response. The fully implantable attribute allows users to take advantage of normal external ear resonances and head-related transfer functions, while avoiding undesirable earmold effects. The high sensitivity, low power consumption, and high fidelity attributes of piezoelectric transducers minimize acoustic feedback and maximize battery life (Gyo, 1996; Yanagihara, (1987) and 2001). The surgical procedure to install the device has been accurately defined and implantation is reversible.

Implantable and semi-implantable hearing AIDS: a review of history, indications, and surgery

Introduction The complaints associated with the use of conventional amplifying hearing aids prompted research at several centers worldwide that ultimately led to the development of implantable devices for aural rehabilitation. Objectives To review the history, indications, and surgical aspects of the implantable middle ear hearing devices. Data Synthesis Implantable hearing aids, such as the Vibrant Soundbridge system (Med-El Corporation, Innsbruck, Austria), the Maxum system (Ototronix LLC, Houston, Texas, United States), the fourth-generation of Carina prosthesis (Otologics LLC, Boulder, Colorado, United States), and the Esteem device (Envoy Medical Corporation - Minnesota, United States), have their own peculiarities on candidacy and surgical procedure. Conclusion Implantable hearing aids, which are currently in the early stages of development, will unquestionably be the major drivers of advancement in otologic practice in the 21st century, improving the quality of life of an increasingly aged population, which will consequently require increased levels of hearing support.

Totally implantable hearing aid surgical technique and the first Indian experience with Envoy esteem

Hearing aids are the principal means of auditory rehabilitation for patients with moderate to severe sensorineural hearing loss. Although technical improvements and modifications have improved the fidelity of conventional aids, hearing aids still have many limitations. Implantable hearing aids offer patients with hearing loss several potential advantages over conventional hearing aids. This presentation will highlight our first experience, the indications, the procedure, the advantages and the current status of totally implantable hearing aids.

Magnetic Resonance Imaging Compatibility and Safety of the SOUNDTEC Direct System

OBJECTIVE/HYPOTHESIS

The purpose of this study was to evaluate magnetic resonance imaging (MRI) compatibility and safety of an electromagnetic implanted hearing device (the SOUNDTEC Direct System; SOUNDTEC, Inc., Oklahoma City, OK) implant during a 0.3-Tesla open MRI imaging examination of the head and neck and to develop an MRI protocol that maximizes patient safety while minimizing the need for implant removal. The current literature regarding MRI compatibility of implantable hearing devices was reviewed.

STUDY DESIGN

Linear and torsional forces, heating, and implant magnetization were evaluated in vitro. Implanted fresh-frozen human temporal bones were used to evaluate image distortion. A prospective study of 11 volunteers previously implanted with the SOUNDTEC Direct System was conducted to evaluate MRI compatibility and safety. A MEDLINE search of the literature between 1980 and July 2005 was reviewed to summarize MRI compatibility testing of implantable hearing devices.

METHODS

Torsional and linear forces experienced by eight implant magnets were measured using calibrated neurologic Von Frey Hairs and compared with finite element analysis predictions as well as forces required to separate the incudostapedial joints of 12 fresh-frozen human temporal bones. Implant heating was determined by measuring the temperature change of eight implant vials compared with saline controls immediately after a head MRI scan. Implant magnetization was evaluated after repeated exposure to a 0.3-Tesla magnetic field. An 11-patient prospective study was performed to evaluate MRI compatibility in a 0.3-Tesla open MRI environment using adult volunteers previously implanted with the SOUNDTEC Direct System. A modified MRI protocol was developed to maximize patient safety. Each individual underwent an audiometric and otologic examination immediately before and after MRI.

RESULTS

Peak linear force at the MRI entry measured 0.5 g +/- 0.2 standard deviation (SD). Maximum torque occurred at isocenter and measured 11.4 g-cm +/- 1.2 SD. The mean torque required to separate the incudostapedial joint was 33.8 g-cm +/- 20.4 SD. The average increase in temperature of the eight implant vials was 0.45 degrees C +/- 0.11 SD, whereas the increase in temperature of the three saline controls measured 0.47 degrees C +/- 0.11 SD. The average change in magnetic flux density of the 14 implant magnets tested was 22.0 gauss. Maximum image distortion occurred during the gradient echo sequence and measured 8.6 cm in diameter with a volume of 5,096 mm. Eleven patients completed a total of 12 head, one shoulder, and three lumbar 0.3-Tesla open MRI scans without patient- or device-related complications other than degradation of the MR image. There was no report of discomfort, tinnitus, dizziness, change in hearing, or change in device performance. All post-MRI changes in pure-tone thresholds, speech discrimination, soundfield thresholds, and aided soundfield thresholds were within the range of test-retest variability.

CONCLUSION

When considering MRI of implantable ferromagnetic hearing devices, issues related to mechanical forces, implant heating, current induction, implant demagnetization, image degradation, and acoustic trauma must be considered. The SOUNDTEC Direct System is both MRI-compatible and safe in a 0.3-Tesla open MRI environment when a modified protocol is used. Degradation of the head MRI image may impair visualization of the ipsilateral temporal bone and adjacent structures within a 2.5- to 4.3-cm radius of the implant and is minimized by using a fast spin echo sequence.

Safe and Reliable Sound Threshold Measures with Direct Vibration of the Ossicular Chain

OBJECTIVES

The aim of the study was to evaluate the safety and feasibility of piezoelectric malleus vibration audiometer (MVA), which presents micromechanical vibrations to the umbo membranae tympani.

STUDY DESIGN

Phase I study performed in a tertiary referral center (University Hospital).

METHODS

The coupling rod of the MVA was moved slowly through the outer ear canal toward the eardrum with a micromanipulator. Coupling was completed when the rod tip touched the umbo membranae tympani. Basic audiologic measures of sound threshold obtained with direct stimulation of the malleus are presented. We used MANOVA (multivariate repeated measures ANOVA) to investigate the repeatability of MVA thresholds from one day to the other and when decoupling and retracting the coupling rod 2 mm off the umbo. We also selected the MANOVA to test for unwanted bone-conduction threshold shifts after MVA application. We assessed normality of the data by quantile-quantile plots of the residuals.

RESULTS

Twenty-eight male and 10 female subjects with normal hearing, 22.2 to 34.6 years old (median age, 27.2 yr) underwent an examination. Thirty-six subjects underwent MVA, because 2 of the 38 subjects who volunteered for the study have not undergone the procedure due to the external auditory canal anatomy preventing application of the MVA. The results show that it is possible to safely and reliably measure thresholds of direct vibration of the ossicular chain. Using pure tone audiograms, no pure tone bone- and/or air-conduction threshold shifts occurred after the procedure. None of the subjects reported any other ear-related symptoms such as vertigo, tinnitus, or dizziness. Geometric mean vibratory displacements at threshold ranged from 0.55 nm at 250 Hz to 0.03 nm at 6 kHz. MANOVA demonstrated a repeatability of MVA thresholds.

CONCLUSION

Malleus vibration audiometry will not allow exact linkage of actual implantable hearing aid. But the present study demonstrates that MVA can provide an audiometric tool for assessing ossicular function and integrity prior to implantation of an electronic hearing amplifier.

Comparison of the implantability of electronic hearing devices in a virtual reality planning environment and in human temporal bones

OBJECTIVE

To develop a procedure using a virtual reality (VR) environment that permitted us to simulate the preoperative fitting of an electronic implantable hearing device (IHD) and assess its implantability.

MATERIAL AND METHODS

This was an experimental, prospective study based on VR simulations involving the pre- and postoperative comparison of the implantability of an IHD. The preoperative possibility of implanting an IHD in a VR environment was compared with the postoperative implantability of the device in the temporal bones of human cadavers and patients. Study groups were analyzed according to the criteria "VR implantation" and "real surgery" using contingency tables.

RESULTS

A computer simulation method based on CT images was developed for the preoperative planning of the implantation. The VR simulation proved feasible in all cases (15 temporal bones and 24 patients). There was no significant difference between the process of implanting the IHD in patients or in the VR environment. These results indicate that VR-based test fittings of an IHD allow prediction of the implantability of an IHD prior to actual surgery.

CONCLUSION

We have described the development of a novel VR procedure for predicting the implantability of hearing devices in otoneurosurgical applications. The VR procedure can be applied universally and may also be used for other parts of the body.

In vivo characterization of piezoelectric transducers for implantable hearing AIDS

BACKGROUND

Piezoelectric bimorph transducers may be used at the input stage of implantable hearing aids to convert ossicle vibrations into electrical waveforms, and at the output stage to convert electrical signals into mechanical motion that drives the ossicles. This study assessed transducer performance in anesthetized, acutely implanted cats using computer-averaged, laser-Doppler vibrometer measures and cochlear potentials.

METHODS

Measures of output linearity and distortion for a transducer placed on the umbo were obtained from averaged laser-Doppler vibrometer outputs. Frequency response and equivalent sound pressure level for transducers placed against the stapes were estimated by comparing compound action potentials and cochlear microphonics elicited preoperatively by acoustic signals with responses elicited postoperatively by signals presented through transducers.

RESULTS

The transducer placed on the umbo exhibited an effective bandwidth that exceeded 8 kHz, linear response behavior for driving voltages up to 2 Vrms, and harmonic distortion of -40 dB or better at all frequencies greater than 250 Hz. Except for a shorter latency, transducer-elicited cochlear potentials were indistinguishable from acoustically elicited responses. Frequency response varied widely across transducers, ranging from reasonably flat to possessing a bandpass characteristic with a peak at 2 to 4 kHz; 1-Vrms signals applied to transducers with various geometries yielded equivalent intensities of 62 to 108 dB sound pressure level at 4 kHz, 51 to 98 dB sound pressure level at 2 kHz, and 55 to 80 dB sound pressure level at 1 kHz. Differences in frequency response and equivalent sound pressure level stemmed from different resonance frequencies in transducers with dissimilar lengths and, more importantly, from variation in transducer-stapes contact force.

CONCLUSIONS

Appropriately designed piezoelectric transducers can provide the cochlea with high-fidelity, wide-bandwidth signals. However, using them in implantable hearing aids requires that geometry and contact force be optimized to reduce variability in output level. Recording cochlear potentials is a cost-effective means of assessing transducer performance intraoperatively, but care must be exercised to take into account any temporary, drill-induced sensitivity loss.

Medical and surgical considerations for implantable hearing prosthetic devices

Today, technology allows us the opportunity to make a substantial difference in the quality of life for individuals who have been unsuccessful with traditional amplification. This article examines the medical and surgical aspects of four types of implantable hearing devices: bone-anchored hearing aid (BAHA), middle ear implants, cochlear implants, and auditory brainstem implants.

Biomechanical influences of magnetic resonance imaging on the SOUNDTEC Direct System implant

OBJECTIVE

The purpose of this study was to measure the forces experienced by the SOUNDTEC Direct System magnetic implant during 0.3-T MRI.

STUDY DESIGN

Torsional and linear forces imposed on 8 implants were measured by using calibrated neurologic Von Frey hairs and were compared with finite-element analysis predictions and the forces required to separate the incudostapedial joints of unpreserved temporal bones. An implanted embalmed autopsy specimen was also examined before and after 1.5-T MRI.

RESULTS

Peak linear force at the orifice of the MRI core measured 0.51g (+/-0.2 SD). Maximum torque occurred at the MRI core center and measured 11.4g-cm (+/-1.2 SD). The mean torque required to separate the incudostapedial joints of 12 unpreserved temporal bones was 33.8g-cm (+/-20.4 SD). The autopsy specimen sustained a 1.5-T MRI scan without disruption of the ossicular chain or explantation.

CONCLUSIONS

Physical and mechanical testing of the SOUNDTEC implant indicates that the structural integrity of the ossicles will be maintained during 0.3-T MRI of the human head.

Middle ear electromagnetic semi-implantable hearing device: results of the phase II SOUNDTEC direct system clinical trial

OBJECTIVE

To assess the safety and efficacy of the SOUNDTEC Direct System, a partially implantable electromagnetic middle ear hearing device.

STUDY DESIGN

Food and Drug Administration Phase II clinical trial of 103 patients at 10 sites across the United States.

SETTING

Tertiary referral medical centers.

PATIENTS

Individuals with bilateral moderate to moderately severe sensorineural hearing impairment who had worn optimally fit hearing aids for at least 45 days.

INTERVENTIONS

Therapeutic intervention included implantation of a 27-mg neodymium iron boron magnet encased in a laser-welded titanium canister onto the incudostapedial joint, followed, after a 10-week healing period, by fitting with a deep earmold coil assembly and activation of the sound processor.

MAIN OUTCOME MEASURES

Functional gain, speech recognition in quiet and noise, articulation index scores, perceived aided benefit, sound quality judgments, satisfaction, and presence of feedback and occlusion with the Direct System were compared with those of the patients' optimally fit hearing aid.

RESULTS

The results of this multicenter clinical trial were submitted to the Food and Drug Administration on April 13, 2001, and are presented here. The results with the use of the SOUNDTEC Direct System compared with an optimally fit hearing aid provided an average 7.9-dB increase in functional gain in the speech frequencies (500-4,000 Hz) and a 9.6 dB gain in high frequencies (2,000, 3,000, and 4,000 Hz). There was a statistically significant average increase of 5.3% in speech discrimination. The mean speech perception in noise test score was improved, but the improvement was not statistically significant. Subjective tests using abbreviated profile of hearing aid benefit and the Hough Ear Institute Profile demonstrated scores statistically improved over the hearing aid condition. These subjective tests measured areas such as the presence of occlusion and feedback, speech quality judgments, device preference, and perceived aided benefit.

CONCLUSIONS

The results of this Phase II clinical trial demonstrate that the SOUNDTEC Direct System provided statistically significant reduction in feedback and occlusive effect as well as a statistically significant improvement in all the following categories: functional gain, articulation index scores, speech discrimination in quiet, perceived aided benefit, patient satisfaction and device preference over the patient's optimally fit hearing aid.