Round Window Stimulation Research Articles

Tinnitus Suppression with Electrical Stimulation at the Most Basal Contact of the Cochlear Implant Electrode as a Model for Round Window Stimulation.

The objective of this research was to test whether efficient tinnitus suppression could be achieved by electrical stimulation of the single most basal electrode contact of a cochlear implant. This approach simulates the effects of electrical stimulation using a round-window electrode. The study was performed in 10 adult cochlear implant patients showing complete or almost complete tinnitus suppression during electrical stimulation with their standard fitting-MAP. In all patients, tinnitus appeared again when the implant was switched off. Five Nucleus implant (1 CI532, 4 CI24RE CA) users and 5 Mi12xx series with FLEX28 electrodes with at least 6 months of CI experience were included. Two types of stimulation were presented at the most basal CI contact: a constant pulse train and a modulated pulse train. The variation in pulse rates was low rate (100-300 pps) and high (≥900 pps), and the current level ranged from the C-level to less than the T-level for both stimulation types. The effect of acute electrical stimulation at the most basal electrode contact was compared to the effect obtained with multichannel stimulation with the patient's current fitting MAP. Electrical stimulation was paused between tests with different stimulation types until tinnitus returned to baseline intensity. Patients reported Visual Analog Scale (VAS) scores for tinnitus loudness and intrusiveness during normal CI use and for each single contact stimulation type. Eight participants perceived complete suppression with one or more stimulation patterns. In 2 patients, suppression was less efficient than full-band CI stimulation. Louder stimuli are generally perceived as annoying and less effective in reducing tinnitus. In FLEX28 patients, it was also possible to obtain full tinnitus suppression with current amplitudes under the thresholds for auditory perception (this was not tested in patients with the Nucleus device). In 8 of the 10 included patients, we were able to obtain complete or almost complete tinnitus suppression with electrical stimulation at only 1 most basal electrode contact. Therefore, round-window stimulation with a single electrode may be a potential treatment for tinnitus in patients with significant residual hearing. The long-term effects of this therapy should be confirmed in future studies.

Using Stapes Velocity to Estimate the Efficacy of Mechanical Stimulation of the Round Window With an Active Middle Ear Implant.

To test a method to measure the efficacy of active middle ear implants when coupled to the round window. Data previously published in Koka et al. ( Hear Res 2010;263:128-137) were used in this study. Simultaneous measurements of cochlear microphonics (CM) and stapes velocity in response to both acoustic stimulation (forward direction) and round window (RW) stimulation (reverse direction) with an active middle ear implant (AMEI) were made in seven ears in five chinchillas. For each stimulus frequency, the amplitude of the CM was measured separately as a function of intensity (dB SPL or dB mV). Equivalent vibrational input to the cochlea was determined by equating the acoustic and AMEI-generated CM amplitudes for a given intensity. In the condition of equivalent CM amplitude between acoustic and RW stimulation-generated output, we assume that the same vibrational input to the cochlea was present regardless of the route of stimulation. The measured stapes velocities for equivalent CM output from the two types of input were not significantly different for low and medium frequencies (0.25-4 kHz); however, the velocities for AMEI-RW drive were significantly lower for higher frequencies (4-14 kHz). Thus, for RM stimulation with an AMEI, stapes velocities can underestimate the mechanical input to the cochlea by ~20 dB for frequencies greater than ~4 kHz. This study confirms that stapes velocity (with the assumption of equivalent stapes velocity for forward and reverse stimulation) cannot be used as a proxy for effective input to the cochlea when it is stimulated in the reverse direction. Future research on application of intraoperative electrophysiological measurements during surgery (CM, compound action potential, or auditory brainstem response) for estimating efficacy and optimizing device coupling and performance is warranted.

Round window stimulation with an interface coupler demonstrates proof of concept

HypothesisTo mechanically stimulate the round window (RW) membrane, an actuator with an interface coupler (IC) has the potential to improve sound transmission to the cochlea as compared to the most used RW stimulation device implanted today. If a proof-of-concept IC prototype shows promise as compared the most common method for RW stimulation, there is potential that future design development of an IC will be worthwhile. BackgroundA variety of hearing pathologies resulting in mixed and conductive hearing loss can be addressed by mechanically stimulating the RW to transmit sound to the cochlea. The most common method for RW stimulation is with the floating mass transducer (FMT, Med-El). However, the FMT suffers poor sound transmission and unreliable device positioning. The dynamic range and bandwidth of the FMT as a RW stimulator is limited because the entire FMT needs freedom to vibrate. Thus the FMT has difficulty overcoming its own inertia and it cannot be stabilized in a manner that may limit its motion. Here we test an idea of using a generic actuator that vibrates on one side while stationary and held stable on the other (unlike the FMT), and coupling the actuator vibration to the RW membrane with a proof-of-concept IC designed to safely transmit sound to the cochlea. We determine if this proof-of-concept IC can perform as well or better than the FMT in one specimen. If so, further developments of the IC would be worthwhile. MethodsRW sound transmission comparison was made between an ideally implanted FMT and a proof-of-concept IC prototype driven by a piezoelectric stack actuator with vibrating tip in a fresh human temporal bone. Velocities of stapes, FMT, and IC actuator were measured with laser Doppler vibrometry to determine bandwidth, linearity, and dynamic range of cochlear sound transmission. ResultsStimulation with proof-of-concept prototype of the IC provided increased sound transmission, more linear output for larger dynamic range, and wider frequency range as compared to the FMT. This experiment demonstrates the potential of the IC concept to improve performance, and that it merits further development. However, it was challenging to stabilize the coupling between an external actuator and the proof-of-concept IC prototype. Thus, although we were successful in showing that this IC concept has promise, major design improvements and developments are required in the future. ConclusionsWe demonstrated that the proof-of-concept IC prototype driven with a tip connected to a piezoelectric stack actuator can stimulate the RW membrane with improved acoustic performance as compared to the FMT in one specimen. This study demonstrated proof of concept: that the idea of an IC for sound transmission to the cochlea through the RW has potential, and that it would be worthwhile to pursue the IC idea with further developments. This idea has the potential to provide robust sound transmission to the cochlea via the RW while preventing possible trauma to the cochlea. We also learned that critical design improvements are necessary because coupling the generic external actuator to the IC was challenging. A possible future IC design is to integrate a piezoelectric actuator permanently to the IC, allowing only the soft balloon membrane of the IC to vibrate the RW while the rest of the exterior housing of the combined IC (with actuator) would not vibrate and would be stabilized in a fixed manner.

Effects of design and coupling parameters on the performance of electromagnetic transducers in round-window stimulation.

Many studies have investigated factors contributing to large variations in the outcomes of round-window (RW) stimulation but most have focused on the floating mass transducer (FMT). To determine whether results for the FMT hold for a fixed-type transducer (FTT), this study constructs two coupled finite element models of the transducer and the human ear that incorporate the cochlear third windows and inner structures of these two electromagnetic transducers. We use these FE models of the human ear and transducers to investigate the influence of four design parameters and coupling conditions for the transducers, i.e., the support's Young's modulus, the coupling layer's cross sectional area and Young's modulus, and the transducer's cross sectional area. The results show that an increase in the support's Young's modulus reduces the output of the FMT but increases that of the FTT. Reducing the cross sectional area and Young's modulus of the coupling layer significantly increases the low-frequency response of the FMT but slightly reduces that of the FTT. Reducing the cross sectional area of the transducer increases the output of the FMT but reduces that of the FTT. This shows that inner structures of electromagnetic transducers should be considered in the optimal design parameters and coupling conditions for RW stimulation.

Analysis of design parameters of round-window stimulating type electromagnetic transducer by a nonlinear lumped parameter model of implanted human ear.

Round-window stimulating transducer is a new solution to treat mixed hearing loss. To uncover the factors affecting the round-window stimulation's performance, we investigated the influence of four main design parameters of round-window stimulating type electromagnetic transducer. Firstly, we constructed a human ear nonlinear lumped parameter model and confirmed its validity by comparing the stapes responses predicted by the model with the experimental data. Following this, an electromagnetic transducer's mechanical model, which simulates the floating mass transducer, was built and coupled to the human ear model; thereby, we established a nonlinear lumped parameter model of implanted human ear under round-window stimulation and verified its reliability. Finally, based on this model, the influences of the four main design parameters, i.e., the excitation voltage, the electromechanical coupling coefficient, the support stiffness, and the preload force, were analyzed. The results show that the change of excitation voltage does not alter the system's natural frequency. Chaotic motion occurs when the electromechanical coupling coefficient is small. Meanwhile, the stapes displacement appears to increase firstly and then decrease with the increase of the electromechanical coupling coefficient. The increase of the support stiffness enlarges the resonance frequency of the stapes displacement and reduces the stapes displacement near the resonance frequency, deteriorating the transducer's hearing compensation at low frequency. The preload force can improve the transducer's hearing compensation performance in mid-high frequency region.

Round Window Stimulation of the Cochlea.

Mixed hearing loss associated with a sensorineural component and an impaired conductive mechanism for sound from the external ear canal to the cochlea represents a challenge for rehabilitation using either surgery or traditional hearing amplification. Direct stimulations of the ossicular chain and the round window (RW) membrane have allowed an improved hearing in this population. The authors review the developments in basic and clinical research that have allowed the exploration of new routes for inner ear stimulation. Similar changes occur in the electrophysiological measures in response to auditory stimulation through the traditional route and direct mechanical stimulation of the RW. The latter has proven to be very effective as a means of hearing rehabilitation in a group of patients with significant difficulties with hearing and communication.

Prognostic Value of Trial Round Window Stimulation for Selection of Candidates for Cochlear Implantation as Treatment for Tinnitus.

Electrical stimulation with cochlear implants is able to significantly suppress the tinnitus sensations in 25–72% of implanted patients. Up to this point, no clear predictors for the effectiveness of tinnitus suppression with cochlear implants have been found and this substantially limits the possibility of the application of cochlear implants for this purpose. The objective of the study was to investigate if a trial electrical round window stimulation (RWS) could be used as a diagnostic tool for identifying candidates in whom electrical stimulation would be successful as treatment for tinnitus. Thirty-four patients with unilateral severe tinnitus and ipsilateral moderate to severe sensorineural hearing loss underwent a trial RWS under local anesthesia. Thirteen patients received a cochlear implant. All patients qualified for cochlear implantation on the basis of the trial RWS showed tinnitus suppression with the implant switched on. Complete or almost complete tinnitus suppression was obtained in 77% and partial in 23%. The mean tinnitus loudness reduction was 68% (VAS score reduction from 7.7 to 2.5). False negative results are estimated not to exceed 10–15%. We conclude that significant tinnitus suppression achieved during trial RWS under local anesthesia is a simple procedure allowing the efficient identification of candidates in whom electrical stimulation with a cochlear implant would be successful as treatment for intractable tinnitus.

Comparative study of efficiency and characteristics of FMT and DRT installed in human cadavers for round-window stimulation

Acoustic hearing aids generate amplified sound in the ear canal, and they are the standard of care for patients with mild to moderate sensorineural hearing loss. However, because of their limited frequency bandwidth, gain, and feedback, there is substantial room for improvement. Active middle ear implants, which directly vibrate the middle ear and cochlea, are an alternative approach to conventional acoustic hearing aids. They provide an opportunity to improve sound quality and speech understanding with amplification rehabilitation. For floating-mass type and direct-rod type (DRT) middle ear transducers, a differential floating-mass transducer (DFMT) and a tri-coil bellows transducer (TCBT), respectively, were fabricated to measure the output characteristics in four human temporal bones. Both were fabricated to have similar output forces per unit input and were placed in four human temporal bones to measure their output performances. The TCBT resulted in higher output than did the DFMT throughout the audible frequency range, and the output was more prominent at lower frequency ranges. In this study, we showed that DRT was a more effective method for round window stimulation. Because of its frequency characteristics and vibration efficiency, this implantation method can be utilized as a driving solution for middle ear implants.

The design of a lumped parameter model considering the stimulus path of round window

BACKGROUND: Sound normally enters the ear canal, passes through the middle ear, and stimulates the cochlea through the oval window. Alternatively, the cochlea can be stimulated in a reverse manner, namely round window stimulation. The reverse stimulation is not well understood, partly because in classic lumped-parameter models the path of reverse drive during the round window stimulation is usually not considered.OBJECTIVE: The study goal is to gain a better understanding of the hearing mechanism during round window stimulation.METHODS: A piezo actuator was coupled to the oval and round window of the guinea pigs. The auditory brainstem response produced by the forward and reverse stimulation at four frequencies was recorded.RESULTS: The results show that the input voltage of the actuator required at the hearing threshold in the round window drive was higher than that in the oval window drive. In order to understand the data, we designed a lumped-parameter cochlear model that can simulate both forward and reverse drive. The model-predicted results were consistent with the experimental results.CONCLUSIONS: The response of the auditory system to stimulus of oval window and round window was quantified through animal experimentation, and guinea pigs were used as experimental animals. When the same stimulus was applied to the oval window and round window of the cochlea, the ABR signals were compared. A lumped parameter model was designed to incorporate the sound transmission paths in both oval and round window stimulation. The simulated results are consistent with those of animal experiments. This model will be useful in understanding the inner-ear response in round window.

Effect of stimulation sites on the performance of electromagnetic middle ear implant: A finite element analysis

Electromagnetic middle ear implants (MEIs), which use the mechanical vibration of their implanted transducers to treat hearing loss, have emerged to overcome the limitations of conventional hearing aids. Several reports have indicated that the electromagnetic MEI's performance changed with different stimulation sites of the transducer. The aim of this study was to analyze the influence of the transducers' stimulation sites on the electromagnetic MEIs' performance. To aid this investigation, a human ear finite-element model was developed from micro-CT images of an adult's right ear. The validity of the model was confirmed by comparing the model-derived results with experimental data. Then, stimulation forces, which simulate ideal electromagnetic transducers, were respectively applied at five typical coupling sites: the umbo, incus body, incus long process, the round window, and the stapes. The stimulation sites' influence on the electromagnetic MEI's performance was studied by analyzing their corresponding basilar membrane displacements. The results show that stimulation of the round window with a force produces more cochlear stimulation than equal force stimulation of the umbo, incus body, incus long process and the stapes, though the superiority of the round window depends on its smaller area compared to the stapes footplate. Among the forward stimulation, the stapes is the optimal stimulation site for the electromagnetic transducer regarding its hearing compensation's efficiency. The performance of the umbo stimulation is comparable to that of the incus-long-process stimulation. Driving the incus body is less efficient than stimulating the other forward driving sites. Additional, using the stapes response to evaluate the forward stimulation gives results similar to those deduced by the basilar membrane response; in contrast, for the round-window stimulation, the evaluation result based on the stapes response is prominently less than the one calculated by the basilar membrane response, especially in the mid-high frequency range.

Finite element analysis of round-window stimulation of the cochlea in patients with stapedial otosclerosis.

An active actuator coupled to the round window (RW) can transmit mechanical vibrations into the cochlea and has become a therapeutic option of hearing rehabilitation for patients with stapedial otosclerosis. A finite-element model of the human ear that includes sound transmission effects of the vestibular and cochlear aqueducts of the inner ear is adopted in this study for investigating the cochlear response to RW stimulation under stapes fixation. There are two effects due to otosclerosis of the stapes: the fixation of the stapedial annular ligament (SAL) and the increase of the stapes mass. The frequency responses of the middle ear and cochlea with normal and otosclerotic stapes are calculated under sound and RW stimulations. The results show that changes in the material property of the stapes have different effects on the cochlear responses under sound and RW stimulations. Because of the vestibuli aqueduct, the reduction in the low-frequency magnitude of the pressure difference across the cochlear partition due to SAL fixation is much smaller under RW stimulation than under sound stimulation. The results of this study help understand sound transmission during RW stimulation in patients with stapedial otosclerosis.

Numerical analysis of the influence of otitis media on the hearing compensation performance of round-window stimulation

In order to study the influence of tympanic membrane lesion and ossicular erosion caused by otitis media on the hearing compensation performance of round-window stimulation, a human ear finite element model including cochlear asymmetric structure was established by computed tomography (CT) technique and reverse engineering technique. The reliability of the model was verified by comparing with the published experimental data. Based on this model, the tympanic membrane lesion and ossicular erosion caused by otitis media were simulated by changing the corresponding tissue structure. Besides, these simulated diseases' effects on the round-window stimulation were studied by comparing the corresponding basilar-membrane's displacement at the frequency-dependent characteristic position. The results show that the thickening and the hardening of the tympanic membrane mainly deteriorated the hearing compensation performance of round-window stimulation in the low frequency; tympanic membrane perforation and the minor erosion of ossicle with ossicular chain connected slightly effected the hearing compensation performance of round-window stimulation. Whereas, different from the influence of the aforementioned lesions, the ossicular erosion involving the ossicular chain detachment increased its influence on performance of round-window stimulation at the low frequency. Therefore, the effect of otitis media on the hearing compensation performance of round-window stimulation should be considered comprehensively when designing its actuator, especially the low-frequency deterioration caused by the thickening and the hardening of the tympanic membrane; the actuator's low-frequency output should be enhanced accordingly to ensure its postoperative hearing compensation performance.

Influence of ossicular chain malformation on the performance of round-window stimulation: A finite element approach.

As a novel application of implantable middle ear hearing device, round-window stimulation is widely used to treat hearing loss with middle ear disease, such as ossicular chain malformation. To evaluate the influence of ossicular chain malformations on the efficiency of the round-window stimulation, a human ear finite element model, which incorporates cochlear asymmetric structure, was constructed. Five groups of comparison with experimental data confirmed the model's validity. Based on this model, we investigated the influence of three categories of ossicular chain malformations, that is, incudostapedial disconnection, incus and malleus fixation, and fixation of the stapes. These malformations' effects were evaluated by comparing the equivalent sound pressures derived from the basilar membrane displacement. Results show that the studied ossicular chain malformations mainly affected the round-window simulation's performance at low frequencies. In contrast to the fixation of the ossicles, which mainly deteriorates round-window simulation's low-frequency performance, incudostapedial disconnection increases this performance, especially in the absence of incus process and stapes superstructure. Among the studied ossicular chain malformations, the stapes fixation has a much more severe impact on the round-window stimulation's efficiency. Thus, the influence of the patients' ossicular chain malformations should be considered in the design of the round-window stimulation's actuator. The low-frequency output of the round-window simulation's actuator should be enhanced, especially for treating the patients with stapes fixation.

Numerical Study and Optimization of a Novel Piezoelectric Transducer for a Round-Window Stimulating Type Middle-Ear Implant.

Round window (RW) stimulation is a new application of middle ear implants for treating hearing loss, especially for those with middle ear disease. However, most reports on it are based on the use of the floating mass transducer (FMT), which was not originally designed for round window stimulation. The mismatch of the FMT’s diameter and the round window membrane’s diameter and the uncontrollable preload of the transducer, leads to a high variability in its clinical outcomes. Accordingly, a new piezoelectric transducer for the round-window-stimulating-type middle ear implant is proposed in this paper. The transducer consists of a piezoelectric stack, a flextensional amplifier, a coupling rod, a salver, a plate, a titanium housing and a supporting spring. Based on a constructed coupling finite element model of the human ear and the transducer, the influences of the transducer design parameters on its performance were analyzed. The optimal structure of the supporting spring, which determines the transducer’s resonance frequency, was ascertained. The results demonstrate that our designed transducer generates better output than the FMT, especially at low frequency. Besides this, the power consumption of the transducer was significantly decreased compared with a recently reported RW-stimulating piezoelectric transducer.

Intracochlear Sound Pressure Measurements in Normal Human Temporal Bones During Bone Conduction Stimulation

Bone conduction (BC) is heavily relied upon in the diagnosis and treatment of hearing loss, but is poorly understood. For example, the relative importance and frequency dependence of various identified BC sound transmission mechanisms that contribute to activate the cochlear partition remain unknown. Recently, we have developed techniques in fresh human cadaveric specimens to directly measure scalae pressures with micro-fiberoptic sensors, enabling us to monitor the input pressure drive across the cochlear partition that triggers the cochlear traveling wave during air conduction (AC) and round-window stimulation. However, BC stimulation poses challenges that can result in inaccurate intracochlear pressure measurements. Therefore, we have developed a new technique described here that allows for precise measurements during BC. Using this new technique, we found that BC stimulation resulted in pressure in scala vestibuli that was significantly higher in magnitude than in scala tympani for most frequencies, such that the differential pressure across the partition-the input pressure drive-was similar to scala vestibuli pressure. BC (stimulated by a Bone Anchored Hearing Aid [Baha]) showed that the mechanisms of sound transmission in BC differ from AC, and also showed the limitations of the Baha bandwidth. Certain kinematic measurements were generally proportional to the cochlear pressure input drive: for AC, velocity of the stapes, and for BC, low-frequency acceleration and high-frequency velocity of the cochlear promontory. Therefore, our data show that to estimate cochlear input drive in normal ears during AC, stapes velocity is a good measure. During BC, cochlear input drive can be estimated for low frequencies by promontory acceleration (though variable across ears), and for high frequencies by promontory velocity.

Impedances of the inner and middle ear estimated from intracochlear sound pressures in normal human temporal bones

For almost a decade, we have measured intracochlear sound pressures evoked by air conducted (AC) sound presented to the ear canal in many fresh human cadaveric specimens. Similar measurements were also obtained during round window (RW) mechanical stimulation in multiple specimens. In the present study, we use our accumulated data of intracochlear pressures and simultaneous velocity measurements of the stapes or RW to determine acoustic impedances of the cochlear partition, RW, and the leakage paths from scala vestibuli and scala tympani, as well as the reverse middle ear impedance. With these impedances, we develop a computational lumped-element model of the normal ear that illuminates fundamental mechanisms of sound transmission.To calculate the impedances for our model, we use data that passes strict inclusion criteria of: (a) normal middle-ear transfer function defined as the ratio of stapes velocity to ear-canal sound pressure, (b) no evidence of air within the inner ear, and (c) tight control of the pressure sensor sensitivity. After this strict screening, updated normal means, as well as individual representative data, of ossicular velocities and intracochlear pressures for AC and RW stimulation are used to calculate impedances. This work demonstrates the existence and the value of physiological acoustic leak impedances that can sometimes contribute significantly to sound transmission for some stimulation modalities. This model allows understanding of human sound transmission mechanisms for various sound stimulation methods such as AC, RW, and bone conduction, as well as sound transmission related to otoacoustic emissions.

Acoustic stimulation on the round window for active middle ear implants

Many clinical reports have discussed the effectiveness of stimulating the ear's round window (RW) with a tool to mitigate conductive and mixed hearing loss. The RW is one of the two openings from the middle ear into the inner ear. Various methods have been proposed to construct a highly efficient, easily implanted, and reliable RW transducer. Devices, however, such as floating mass transducers, have difficulty establishing proper contact without some degree of bone incision around the RW. Additionally, vibration energy may not be fully transmitted to the cochlea, but instead will be spread through the soft tissue around the transducer. We propose a more direct RW stimulation with very high acoustical impedance using a receiver that is a volume velocity source. We expect this source to overcome large acoustic impedance by maximizing sound pressure in a confined space, the RW niche. To verify the effectiveness of the proposed method, ear canal pressure, RW pressure, and stapes velocity are measured by acoustic RW stimulation of human temporal bones.

The effect of preload and support's stiffness on the performance of round window stimulation: a numerical analysis

To investigate the influence of the preload and supporting stiffness on the hearing compensation performance of round window stimulation, a coupling finite model composed of a human ear, an actuator and a support was established. This model was constructed based on a complete set of micro-computed tomography (Micro-CT) images of a healthy adult's right ear by reverse engineering technology. The validity of the model was verified by comparing the model's calculated results with experimental data. Based on this model, we applied different amplitude preloads on the actuator, and changed the support's stiffness. Then, the influences of the actuator's preload and the support's stiffness were analyzed by comparing the corresponding displacements of the basilar membrane. The results show that after applying a preload on the actuator, its hearing compensation performance was increased at the middle and high frequencies, but was deteriorated at low frequencies; besides, compared with using the fascia as the actuator's support in clinical practice, utilizing the titanium alloy to fabricate the support would enhance the hearing compensation performance of the round window stimulation in the whole frequency range.

Excitation of the Auditory System as a Result of Non-invasive Extra-Cochlear Stimulation in Normal Subjects and Tinnitus Patients.

One of possible approach that may suppress tinnitus is electrical stimulation of the ear. At first invasive techniques were used (promontory or round window stimulation), nowadays a non-invasive method, namely hydrotransmissive electric stimulation (ES) through external acoustic canal, has been developed. The aim of the study is to investigate the effect of applying ES with positive and negative current polarities on the ears of healthy subjects and on the tinnitus ears of patients with tinnitus. This comparison further clarifies the mechanisms of operation of non-invasive extra-cochlear ear ES. A second aim is to assess the effects of ES on tinnitus in tinnitus patients. The material was composed of two groups: tinnitus group—49 patients suffering from tinnitus, and healthy students group—34 healthy individuals. ES was performed with the use of a custom-made apparatus. The active, silver probe–was immersed inside saline filling external ear canal. The passive electrode was placed on the forehead. Positive and next negative DC stimulation was provided with the use following frequencies: 0.25, 1, 2, 3, 4, 5, 6, 7, 8 kHz. We checked for the presence of the auditory percept (AP) and, if AP was present, the minimum current amplitude necessary to produce AP was measured. In our research both positive and negative polarities were efficient to evoke AP in the participants. This effect, however, was more pronounced for positive polarity in no tinnitus and normal hearing individuals (healthy students group). In the tinnitus group, current intensity needed to evoke AP was higher than in the healthy students group. However, comparing normal hearing vs. hearing loss patients within the tinnitus group, we did not observe the relationship between hearing threshold and current intensity evoking AP. Afterwards, we analyzed the effect of multi-frequency ES on tinnitus. It appeared to be effective in 75% of tinnitus ears (with a high score of disappearance–22%). Our study proved that extracochlear ES with positive and negative current was efficient to stimulate the auditory system. Stimulating tinnitus ears with two polarities we obtained a higher ratio of improvement (75%) comparing to positive stimulations.

Redesign of the Hannover Coupler: Optimized Vibration Transfer from Floating Mass Transducer to Round Window.

Introduction In order to reduce the large variations in clinical outcomes of patients with implanted MED-EL Floating Mass Transducer (FMT) at the round window (RW), several approaches were proposed to optimize FMT-RW coupling. Our previous study showed improved FMT-RW coupling by applying static RW loads utilizing the “Hannover Coupler” (HC) FMT-prosthesis but also demonstrated insufficient low frequency performance. Hence, a redesigned HC version (HCv2) was investigated in this study. Methods Experiments were performed in ASTM F2504-05 compliant fresh human temporal bones. The HCv2 is a FMT-prosthesis redesigned from a previous prototype to specifically improve low frequency performance. Stapes footplate (SFP) displacements in response to acoustic stimulation of the tympanic membrane and to FMT-RW stimulation at varying static force (0–100 mN) were measured by Laser-Doppler vibrometry. Results SFP displacements were highly dependent on the applied RW load and had a global maximum at 15 mN when averaged at speech relevant frequencies (0.5–4 kHz). SFP responses at frequencies ≤ 1 kHz were up to 25 dB higher than responses achieved with the previous HC version. Conclusion Optimizing the HC prosthesis design resulted in improved SFP responses to RW stimulation especially at lower frequencies (≤1 kHz).