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

OBJECTIVE: To test a method to measure the efficacy of active middle ear implants when coupled to the round window. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Long-Term Safety and Quality of Life after Vibroplasty in Sensorineural Hearing Loss: Short/Long Incus Process Coupler.

OBJECTIVE: The study shows the long-term effectiveness, safety, and quality of life after Vibrant Soundbridge (VSB) implantation in sensorineural hearing loss (SNHL) using the short process coupler (SP) or the long process coupler (LP). METHODS: This retrospective study evaluated 77 VSB cases. Follow-up (F/U) time-dependent objective measurements (audiological outcomes), subjective data collection (quality-of-life questionnaire), and safety measures are presented. RESULTS: Sixty-two ears were included in the analysis with up to 116 months of postsurgical F/U data (mean 32.15 ± 37.97 months LP and SP coupler). Fifty-three ears (13 bilateral cases) received the LP coupler and 9 subjects the SP coupler. The post-operative bone conduction thresholds remained stable and, in both groups, <10 dB. The benefit in word recognition scores measured at 65 dB SPL and 80 dB SPL showed no significant difference between the couplers (p = 0.559 and p = 0.088, respectively). The functional gain was not significantly different (p > 0.05) with a mean of 20.91 ± 9.77 and 17.19 ± 5.75 for LP and SP coupler, respectively. The utility score deciphered from the Assessment of Quality-of-life Questionnaire-8 dimensions revealed a mean score of 0.75 ± 0.16 which is not significantly different to the age- and sex-matched healthy control group with 0.81 ± 0.02 (p = 0.3547). CONCLUSION: The Incus Vibroplasty utilizing both couplers is a safe and effective method to treat mild-to-severe SNHL. Both fixation methods of the floating mass transducer exhibit good clinical and audiological outcomes with high patient quality of life. The SP coupling method can be a good alternative when the long process is anatomically inaccessible, or the approach is limited due to anatomical reasons.

Are suspensory ligaments important for middle ear reconstruction?

As the resolution of 3D printing techniques improves, the possibility of individualized, 3-ossicle constructions adds a new dimension to middle ear prostheses. In order to optimize these designs, it is essential to understand how the ossicles and ligaments work together to transmit sound, and thus how ligaments should be replicated in a middle ear reconstruction. The middle ear ligaments are thought to play a significant role in maintaining the position of the ossicles and constraining axis of rotation. Paradoxically, investigations of the role of ligaments to date have shown very little impact on middle ear sound transmission. We explored the role of the two attachments in the gerbil middle ear analogous to human ligaments, the posterior incudal ligament and the anterior mallear process, severing both attachments and measuring change in hearing sensitivity. The impact of severing the attachments on the position of the ossicular chain was visualized using synchrotron microtomography imaging of the middle ear. In contrast to previous studies, a threshold change on the order of 20 dB across a wide range of frequencies was found when both ligaments were severed. Concomitantly, a shift in position of the ossicles was observed from the x-ray imaging and 3D renderings of the ossicular chain. These findings contrast with previous studies, demonstrating that these ligaments play a significant role in the transmission of sound through the middle ear. It appears that both mallear and incudal ligaments must be severed in order to impair sound transmission. The results of this study have significance for middle ear reconstructive surgery and the design of 3D-printed three-ossicle biocompatible prostheses.

[Laser Doppler vibrometric measurements on human temporal bones]. / Laser-Doppler-vibrometrische Messungen an humanen Felsenbeinen.

Laser Doppler vibrometric (LDV) measurements on human temporal bones represent the standard method for predicting the performance of active middle ear implants (AMEI) and are used as preclinical tests in the development, approval process, and indication expansion of AMEI. The quality of the coupling of the floating mass transducer to the mobile structures of the middle ear is decisive for the performance of the implant and patients' hearing perception. The cochlea can be stimulated via the oval window (forward stimulation) or the round window (reverse stimulation). For forward stimulation, the ASTM standard F2504-05 defines a method to ensure physiologically normal properties of the temporal bones used in the experiments. For reverse stimulation, which depends even more critically on the quality of the temporal bone, a comparable standard method is lacking. Appropriate preparation and storage of the human petrous bone as well as suitable LDV test setups with respect to calibration and reproducibility of measuring positions and angles provide results that allow a comparison of different types of coupling and also correlate well with clinical data.

Feasibility Study of a Mechanical Real-Time Feedback System for Optimizing the Sound Transfer in the Reconstructed Middle Ear.

OBJECTIVE: To evaluate electromechanical excitation as an alternative excitation mode for middle ear transfer function (METF) measurements as well as real-time feedback in prosthetic ossicular reconstruction. METHOD: In eight human cadaveric temporal bones, the ossicular chain was excited using acoustic and mechanical (floating mass transducer, FMT) stimulation to determine the METF. After disconnecting the ossicular chain and reconstruction with partial or total prosthesis the METFs were measured again. Continuous FMT stimulation was then applied to improve the prosthesis' position using real-time feedback of the METF. RESULTS: Mechanical stimulation of ossicular vibration showed characteristic differences to acoustic excitation resulting from the force characteristics of the FMT. Furthermore, the interspecimen METF variability was greater with electromechanical than acoustic stimulation because of interspecimen variability in the FMT coupling conditions. When the METF with FMT excitation was used as a real-time feedback tool, a measurable improvement in the quality of ossicular reconstruction could be achieved. CONCLUSIONS: Mechanical excitation is an effective and suitable alternative stimulation method in experimental METF measurements. The system provides real-time feedback for ossicular reconstruction in the experimental setting. Some influencing factors still need to be distinguished for reliable measurements. However, the method does not yet meet the requirements for clinical application as an intraoperative, real-time monitoring tool. However, the system could be an excellent model for high-end cadaveric temporal bone training in ossiculoplasty.

Feasibility of Round Window Stimulation by a Novel Electromagnetic Microactuator.

INTRODUCTION: Most implantable hearing aids currently available were developed to compensate the sensorineural hearing loss by driving middle ear structures (e.g., the ossicles). These devices are successfully used in round window (RW) stimulation clinically, although this was initially not the intended use. Here, a novel microactuator, specifically designed for RW stimulation, was tested in human temporal bones to determine actuator performance and applicability. METHODS: Stapes footplate response to RW stimulation was determined experimentally in human temporal bones and the obtained sound pressure output level was estimated. RESULTS: The actuator had a flat displacement response between 0.125 and 4 kHz, a resonance between 4 and 7 kHz, and a roll-off above. At increasing contact force, the stapes footplate displacement decreased by 5-10 dB re µm for forces ≥ 2 mN. The equivalent sound pressure level between 0.125 and 4 kHz amounted to 87-97 eq dB SPL and increased to 117 eq dB SPL for frequencies of 4-7 kHz. The total harmonic distortion (THD) of the actuator ranged within 15-40% for static forces of 5 mN. CONCLUSION: The feasibility of an electromagnetic actuator that may be placed into the RW niche was demonstrated but requires further optimization in terms of THD and static force sensitivity.

Implantable microphones as an alternative to external microphones for cochlear implants.

Totally implantable cochlear implants may be able to address many of the problems cochlear implant users have around cosmetic appearances, discomfort, and restriction of activities. The major technological challenges that need to be solved to develop a totally implantable device relate to implanted microphone performance. Previous attempts at implanting microphones for cochlear implants have not performed as well as conventional cochlear implant microphones, and in addition have struggled with extraneous body or surface contact noise. Microphones can be implanted under the skin or act as sensors in the middle ear; however, evidence from middle ear implants suggest body and contact noise can be overcome by converting ossicular chain movements into digital signals. This article reviews implantable microphone systems and discusses the technology behind them.

A comparative study of MED-EL FMT attachment to the long process of the incus in intact middle ears and its attachment to disarticulated stapes head.

The Vibrant Soundbridge© (VSB) active middle-ear implant provides an effective treatment for mild-to-severe sensorineural hearing loss in the case of normal middle ear anatomy and mixed hearing loss in middle ear malformation. The VSB floating mass transducer (FMT), with proper couplers, can be installed on various structures of the ossicular chain, e.g., the short and long process of the incus, the stapes head, and the stapes footplate. A long process (LP) coupler is most commonly used for FMT attachment to the long process of the incus with intact ossicular chain, while CliP and Bell couplers are two standardized and reliable methods for FMT attachment to the stapes head with missing incus and malleus. However, the difference and relationship of the vibration properties among these three FMT couplers remain unclear. In the present study, the stapes footplate velocity responses of the LP, CliP, and Bell couplers have been investigated in eight fresh temporal bones (TBs) to evaluate the vibration properties of these three couplers. Normal and reconstructed middle ear transfer functions (METFs) were determined from laser Doppler vibrometer (LDV) measurements. A mastoidectomy and a posterior tympanotomy were performed to expose the ossicular chain. The METFs of the normal middle ear and middle ear with LP-FMT-coupler were compared under acoustic stimulation, thus the mass effect of the FMT with LP coupler was evaluated. Additional comparisons were made between the stapes footplate vibrations of the LP-FMT-coupler (with the intact ossicular chain at the long process of the incus), CliP-FMT-coupler and Bell-FMT-coupler on the stapes head (after incus and malleus removed) under active electromechanical stimulation. After the installation of CliP-FMT-coupler and Bell-FMT-coupler to the middle ear, the average velocity amplitude of the stapes footplate, comparing to the LP-FMT-coupler, was about 15 dB higher between 1 and 6 kHz, and 10 dB lower at about 0.5 kHz. Quantitatively, there was no significant difference between the CliP-FMT-coupler and Bell-FMT-coupler. According to our study, installation of CliP-FMT-coupler or Bell-FMT-coupler on the stapes head provides considerable improvement of the middle ear mechanical and functional responses, comparing with the LP-FMT-coupler in the temporal bone experiments. Moreover, the installation of the Bell-FMT-coupler to the stapes head produces essentially the same footplate velocity responses in comparison to the CliP-FMT-coupler.

New chamber stapes prosthesis - A preliminary assessment of the functioning of the prototype.

Piston-stapedotomy is the most common method for hearing restoration in patients with otosclerosis. In this study, we have experimentally examined a prototype of a new chamber stapes prosthesis. The prototype was implanted in a human cadaver temporal bone. The round window vibrations before and after implantation were measured for the acoustic signal (90 dB SPL, 0.8-8 kHz) in the external auditory canal. In comparison with a 0.4-mm piston prosthesis, the chamber prosthesis induced significantly higher vibration of the round window, especially for frequencies above 1.5 kHz. Based on the results, it can be surmised that stapedotomy with a chamber stapes prosthesis could provide better hearing results in comparison with the piston-stapedotomy.

A tri-coil bellows-type round window transducer with improved frequency characteristics for middle-ear implants.

A number of methods to drive the round window (RW) using a floating mass transducer (FMT) have been reported. This method has attracted attention because the FMT is relatively easy to implant in the RW niche. However, the use of an FMT to drive the RW has been proven to produce low outputs at frequencies below approximately 1 kHz. In this study, a new tri-coil bellows-type transducer (TCBT), which has excellent low frequency output and is easy to implant, is proposed. To design the frequency characteristics of the TCBT, mechanical and electrical simulations were performed, and then a comparative analysis was conducted between a floating mass type transducer (like the FMT) and a fixed type transducer (like the TCBT). The features of the proposed TCBT are as follows. First, the TCBT's housing is fixed to the RW niche so that it does not vibrate. Second, the internal end of a tiny bellows is connected to a vibrating three-pole permanent magnet located within three field coils. Finally, the rim of the bellows bottom is attached to the end of the housing that hermetically encloses the three field coils. In this design, the only vibrating element is the bellows itself, which efficiently drives the RW membrane. To evaluate the characteristics of this newly developed TCBT, the transducer was installed in the RW niche of temporal bones and the velocity of the stapes was measured using a laser Doppler vibrometer. The experimental results indicate that the TCBT can produce 100, 111, and 129 dB SPL equivalent pressure outputs at below 1 kHz, 1-3 kHz, and above 3 kHz, respectively. Thus, the TCBT with one side coupled to the RW via a bellows will be easy to implant and offer better performance than an FMT.

[Vibrant Soundbridge®: An Alternative Hearing System for Preschool Children with Aural Atresia]. / Die Vibrant Soundbridge®: Ein alternatives Hörsystem bei Vorschulkindern mit Gehörgangsatresie.

BACKGROUND: The audiological treatment of children with aural atresia makes high demands on physicians and acousticians. Conventional hearing systems are often not tolerated by children and therefore do not meet the needs of the early and efficient therapy of hearing disorders. Aim of the present study was the evaluation of the audiological functional gain in children with uni- and bilateral aural atresia provided with the middle ear implant Vibrant Soundbridge(®) (VSB(®)) below the age of 6 years as well as the analysis of parents' satisfaction assessed with questionnaires. MATERIAL AND METHODS: The VSB(®) was implanted in 16 children, 13 with unilateral and 3 with bilateral aural atresia, with the mean age of 2;11±1;6 years. 3 months after the first fitting of the audio processor, pure-tone audiometry via free field testing with and without the hearing system was performed. Furthermore, parents completed a standardized questionnaire to evaluate their satisfaction with the VSB(®) treatment quality. The questionnaire included items on the acceptance by children, handling, listening effort, behavior, satisfaction, quality of life, aesthetics, and the length of daily use. RESULTS: The use of the VSB(®) resulted in a significantly improved hearing level: 20 dB on average (Z=- 3.06; p=0.002; n=12). The analysis of parents' questionnaire demonstrated high or very high satisfaction with VSB(®) in all subjects. Primarily, the length of daily use of the VSB(®) was significantly higher than that of the hearing system used before with 10.0±2.1 vs. 2.7±2.2 h per day (Z=- 3.06; p=0.002; n=14). CONCLUSION: The VSB(®) presented a good alternative for audiological treatment of uni- and bilateral aural atresia at toddler and pre-school age.

The Effect of Piston Diameter in Stapedotomy for Otosclerosis: A Temporal Bone Model.

HYPOTHESIS: The use of larger-diameter pistons in stapedotomy leads to better hearing outcomes compared with the use of smaller-diameter pistons. There is an interaction between stapes piston diameter and fenestration diameter. BACKGROUND: Otosclerosis can be treated surgically by removing part of the stapes and bypassing the stapes footplate with a prosthesis. Available piston shaft diameters range between 0.3 and 0.8 mm. There has been a tendency toward the use of smaller-diameter pistons, because of a suspected decreased risk of cochlear trauma and subsequent sensorineural hearing loss (SNHL) with smaller pistons. However, mathematical models, temporal bone studies, and clinical studies suggest that the use of larger-diameter pistons is associated with better hearing outcomes. METHODS: Three fresh-frozen, non-pathologic temporal bones were harvested from human cadaveric donors. Acoustic stimuli in the form of pure tones from 250 to 8000 Hz were generated at 110 dB sound pressure level. A total of 16 frequencies in a 1/3-octave series were used. Stapes and round window velocities in response to the acoustic stimuli were measured at multiple equally spaced points covering the stapes footplate and round window using a scanning laser Doppler interferometry system. Eight sets of measurements were performed in each temporal bone: 1) normal condition (mobile stapes), 2) stapes fixation and stapedotomy followed by insertion of 3) a 0.4-mm-diameter piston in a 0.5-mm-diameter fenestration, 4) a 0.4-mm-diameter piston in a 0.7-mm-diameter fenestration, 5) a 0.4-mm-diameter piston in a 0.9-mm-diameter fenestration, 6) a 0.6-mm-diameter piston in a 0.7-mm-diameter fenestration, 7) a 0.6-mm-diameter piston in a 0.9-mm-diameter fenestration, and 8) a 0.8-mm-diameter piston in a 0.9-mm-diameter fenestration. RESULTS: At midrange frequencies, between 500 and 4000 Hz, round window velocities increased by 2 to 3 dB when using a 0.6-mm-diameter piston compared with a 0.4-mm-diameter piston. Using a 0.8-mm-diameter piston led to a further increase in round window velocities by 2 to 4 dB. CONCLUSION: Our results suggest a modest effect of piston diameter on hearing results following stapedotomy.

Intraoperative assessment of ossicular fixation.

Determining the degree of ossicular fixation is a difficult task, with the final assessment often being made with manual palpation during exploratory tympanotomy. A more objective method to evaluate ossicular fixation would be valuable. In this paper we describe a new method which makes use of a magnet and coil to measure ossicular motion through the ear canal with an elevated tympanic membrane. We report measurements of the vibration response at the umbo, the tip of the incus long process and the lateral posterior crus of the stapes before and after artificially fixing the stapes footplate and anterior mallear ligament with luting cement. Results were obtained on temporal bones, but the practicality of the method allows easy clinical implementation. Velocity ratios between different measurement points along the ossicular chain may provide a quantitative indication of the degree of stapes fixation. Isolated anterior mallear ligament fixation was not distinguishable from the unfixed condition.

First results of a novel adjustable-length ossicular reconstruction prosthesis in temporal bones.

OBJECTIVES/HYPOTHESIS: The performance of an ossicular replacement prosthesis (ORP) is influenced by its alignment and appropriate tension between the tympanic membrane and the stapes footplate. A novel ORP with a flexible element that potentially allows for length adjustment in situ is presented and tested for acoustic performance. STUDY DESIGN: Laser Doppler vibrometry in fresh human cadaveric temporal bones was used to test the acoustic performance of the adjustable ORP relative to standard prostheses used for ossiculoplasty. METHODS: The three-dimensional (3D) velocity of the stapes posterior crus was measured in the 0.2- to 20-kHz range using a Polytec CLV-3D laser Doppler vibrometer. The middle ear cavity was accessed through a facial recess approach. After measuring the normal response, the incus was removed and stapes velocity was measured in the disarticulated case, then after insertion of the new prosthesis, a conventional prosthesis (Kurz BELL Dusseldorf type), and a sculpted autologous incus prosthesis in each temporal bone. The 3D stapes velocity transfer function (SVTF) was calculated for each case and compared. RESULTS: The novel ORP design restored stapes velocity to within 6 dB (on average) of the intact response. No significant differences in 3D-SVTF were found between the new, conventional, or autologous ORPs. CONCLUSIONS: The inclusion of an in situ adjustable element into the ORP design did not adversely affect its acoustic performance. The adjustable element may increase the ease of achieving optimal ORP placement, especially through a facial recess approach. LEVEL OF EVIDENCE: NA Laryngoscope, 126:2559-2564, 2016.

3D displacement of the middle ear ossicles in the quasi-static pressure regime using new X-ray stereoscopy technique.

A novel X-ray stereoscopy technique, using greyscale information obtained from moving markers, was used to study the 3D motion in both gerbil and rabbit middle ear ossicles in the quasi-static pressure regime. The motion can be measured without visually exposing the ossicles. The ossicles showed non-linear behaviour as a function of both pressure and frequency. For instance, about 80% of the maximum umbo displacement occurs at a 1 kPa (peak-to-peak) pressure load, while a limited increase of the amplitude is noticed when the pressure goes to 2 kPa. In rabbit the ratio of stapes to umbo motion amplitude was 0.35 for a pressure of 2 kPa (peak-to-peak) at 0.5 Hz. From two stereoscopic projections of the marker paths, 3D motion of the ossicles could be calculated. This motion is demonstrated on high-resolution computer models in order to visualize ossicular chain behaviour.

A single-ossicle ear: Acoustic response and mechanical properties measured in duck.

To date, the single-ossicle avian middle ear (ME) is poorly understood, despite its striking resemblance to the design of many currently used ossicular replacement prostheses. This study aims to improve comprehension of this system. The acoustic response and the mechanical properties of the mallard middle ear were studied by means of optical interferometry experiments and finite element (FE) simulations. A finite element model was constructed based on µCT data and validated using the experimental results. Stroboscopic holography was used to measure the full-field displacement of the tympanic membrane (TM) under acoustic stimulation, and the transfer function was obtained with laser Doppler vibrometry. A sensitivity analysis concluded that the most influential parameters for ME mechanics are the elasticity of the TM, the extracolumella (the cartilaginous part of the columella) and the annular ligament of the columellar footplate. Estimates for the Young's modulus of the TM were obtained by iteratively updating the FE model to match experimental data. A considerable inter-individual variability was found for the TM's elasticity. Comparison of the experimental results and the optimized FE model shows that, similar to the human middle ear, damping needs to be present in the TM to describe the specific spatial and frequency dependent vibrations of the TM. In summary, our results indicate which mechanical parameters are essential to the good functioning of the avian ME and provide a first estimation of their values.

A method to measure sound transmission via the malleus-incus complex.

BACKGROUND: The malleus-incus complex (MIC) plays a crucial role in the hearing process as it transforms and transmits acoustically-induced motion of the tympanic membrane, through the stapes, into the inner-ear. However, the transfer function of the MIC under physiologically-relevant acoustic stimulation is still under debate, especially due to insufficient quantitative data of the vibrational behavior of the MIC. This study focuses on the investigation of the sound transformation through the MIC, based on measurements of three-dimensional motions of the malleus and incus with a full six degrees of freedom (6 DOF). METHODS: The motion of the MIC was measured in two cadaveric human temporal bones with intact middle-ear structures excited via a loudspeaker embedded in an artificial ear canal, in the frequency range of 0.5-5 kHz. Three-dimensional (3D) shapes of the middle-ear ossicles were obtained by sequent micro-CT imaging, and an intrinsic frame based on the middle-ear anatomy was defined. All data were registered into the intrinsic frame, and rigid body motions of the malleus and incus were calculated with full six degrees of freedom. Then, the transfer function of the MIC, defined as velocity of the incus lenticular process relative to velocity of the malleus umbo, was obtained and analyzed. RESULTS: Based on the transfer function of the MIC, the motion of the lenticularis relative to the umbo reduces with frequency, particularly in the 2-5 kHz range. Analysis of the individual motion components of the transfer function indicates a predominant medial-lateral component at frequencies below 1 kHz, with low but considerable anterior-posterior and superior-inferior components that become prominent in the 2-5 kHz range. CONCLUSION: The transfer function of the human MIC, based on motion of the umbo and lenticularis, has been visualized and analyzed. While the magnitude of the transfer function decreases with frequency, its spatio-temporal complexity increases significantly.

Retrospective audiological analysis of bone conduction versus round window vibratory stimulation in patients with mixed hearing loss.

OBJECTIVE: To compare audiological outcomes in mild-to-moderate mixed hearing loss patients treated with a bone-anchored hearing aid or an active middle-ear implant. Analysis aimed to refine criteria used in preoperative selection of implant type. DESIGN: Retrospective comparative analysis of audiological data. Follow-up time ranged between 0.55 and 8.8 years. STUDY SAMPLE: For detailed comparative analysis, 12 patients (six in each group) with comparable bone conduction thresholds and similar clinical characteristics were selected. A larger cohort of 48 patient files were used to evaluate overall audiological indication criteria (24 per group). RESULTS: In free-field tone audiometry, Baha patients showed mean aided thresholds between 40-48 dB, whereas hearing thresholds for VSB patients were 25-43 dB. Baha and VSB users had mean WRS of 56% and 82%, respectively, at 65 dB. Better speech understanding in noise was seen with the VSB. CONCLUSION: Analysis of the main cohort (n = 48) showed that treatment with round window vibroplasty leads to better hearing performance than treatment with a bone-anchored hearing device, if the bone conduction pure-tone average (0.5 to 4 kHz) is poorer than 35 dB HL. Audiological analysis in the smaller comparative analysis showed similar findings.

Regenerative Cell Therapy for the Sensorineural Hearing Loss / 한양의대학술지

Sensorineural hearing loss is the most common disability in the world and nearly one third of all individuals over the age of 65 are affected. For hearing handicapped people, many devices (hearing aid, cochlear implant, middle ear implant etc.) have been developed to reduce or overcome the disability. But these devices do not give perfect benefit to the patients functionally and there are aesthetic problems. That is why researchers have interest in regenerative measures to restore or prevent hearing loss. Recently there were fruitful results from gene and stem cell therapy research for hearing loss. Gene therapy with Atoh 1 gene and transplantation of stem cells into the cochlea regenerate damaged hair cells and morphologically restore spiral ganglion neurons allowing functional hearing in the deaf animal model. Based on these results, many countries including Korea have done clinical trials in deaf patients. The past ten years have shown an incredible advancement in medical biotechnology in the otologic field and this progress may someday substitute the medical devices for the hard of hearing patients.