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Studying the insertion process of cochlear implant (CI) electrode array (EA) is important to ensure successful, sufficient, and safe implantation. A three-dimensional finite element (FE) model was developed to simulate the insertion process. The cochlear structures were reconstructed from an average statistical shape model (SSM) of human cochlea. The electrode is simplified as a long and tapered beam of homogeneous elastic materials, contacting and interacting with the stiff cochlear structures. A quasi-static insertion simulation was conducted, the insertion force and the contact pressure between the electrode and the cochlear wall, were calculated to evaluate the smoothness of insertion and the risk of potential cochlear trauma. Based on this model, different EA designs were analyzed, including the Young's modulus, the straight or bended shape, the normal or a more tapped section size. The influence of the insertion angle was also discussed. Our simulations indicate that reducing the EA Young's modulus, tapering and pre-bending are effective ways to ensure safe and successful EA implantation. This model is beneficial for optimizing EA designs and is potentially useful for designing patient-specific CI surgery.

Objectives To quantify the progression of otosclerosis in the unoperated ear between two stapedotomy procedures for patients with bilateral otosclerosis which can help to determine whether a HRCT scan should be re-performed before the second surgery for patients who already received HRCT imaging before the initial surgery. Methods 35 patients who underwent bilateral stapedotomy were included. Two rounds of HRCT examination and audiometry were performed at the time of the first surgery and second surgery on the ear that was not operated on during the initial surgery. The relationship between the changes in HRCT densitometry and audiometry over time was analyzed. Results The second round of HRCT did not add significant information about the changes to the otosclerosis lesions in either the imaging diagnosis or the HRCT density values except for small changes in the HRCT densitometry readings at the area anterior to the inner auditory (P = 0.01). While the changes in HRCT manifestation are small, changes near the fissula ante fenestram (FAF) were still positively correlated with the air bone gap (ABG) of patients (p=0.031, r=0.388). Conclusions The progression of lesions in otosclerosis is slow resulting in small and insignificant changes to the HRCT features. Therefore, a repeat HRCT evaluations prior to surgery is not necessary for patients who have had a previous HRCT evaluation within 2 years of the operation. The small changes in HRCT manifestation near the FAF were still correlated with negative effects on the ABG which could cause worsened hearing thresholds over this timeframe.

The Baha® Attract system can provide effective and stable hearing amplification for patients with microtia. Concurrent surgeries of auricle reconstruction and Baha® Attract implantation do not result in more soft tissue complications. The number of adverse events increased with the duration of implantation, even one year postoperatively. Benign skin evolutions, including skin thinning and erythema at the implant side, are commonly seen in Baha® Attract users. Implants are not necessarily removed when skin necrosis occurs in Baha® Attract users.

Purposes: To evaluate the instant auditory benefit of an adhesive bone conduction hearing aid (ADHEAR) on children with bilateral congenital microtia, especially the sound localization ability under unilateral and bilateral fitting. Methods: Twelve patients with bilateral congenital microtia aged from 6 to 17 were included in this study. Pure tone threshold under sound field, speech recognition threshold in quiet and sound localization abilities were tested and compared before and after wearing the device. The pure tone threshold test was additionally repeated for two different wearing method – adhesive or fixed with softband; the sound localization test was repeated for both unilateral and bilateral fitting. Correlation analysis was then conducted to find the influencing factors of sound localization improvement. Results: Significant auditory improvement were found: the average pure tone threshold (PTA) reduced by 24.8 (adhesive) and 27.3 dB HL (softband), with no significant difference between the two wearing methods. The speech recognition threshold also improved by 29.0 dB. As for sound localization abilities, no significant improvement was found under unilateral fitting; but half (6 of 12) of the patients were notably benefited from bilateral fitting. The improvement was found to be strong correlated with the patients’ unaided sound localization ability – those with poorer localization abilities tends to benefit more. Moreover, it was found that the sound localization improvement was also negatively related with the malformation degrees of the patients’ head. Summary: ADHEAR affords significant auditory benefits for children with bilateral congenital microtia, in terms of sound and speech perception. The sound localization abilities could be partly improved instantly by bilateral fitting, and the improvement is related with factors such as adaption and skull malformations.

The aims of this article are: (1) is there an ideal incudostapedial joint (ISJ) angle after stapedotomy? (2) is there any difference between pre- and postoperative ISJ angle? and (3) what is the significance of the ISJ angle in postoperative hearing outcomes? Forty six ears from 39 different adult patients (28 women and 11 men; 21 left and 25 right ears) with a mean age of 39 years with clinical otosclerosis who underwent stapedotomy between May 2017 and May 2019 were retrospectively registered, including seven bilateral surgery cases. ISJ angle and intravestibular depth of the stapes prosthesis were measured from multiple planar reconstruction-computed tomography images and the length of the prosthesis was measured during surgery. Relationships between the ISJ angle parameters and postoperative hearing outcomes and parameters of the prosthesis were analyzed. The mean ISJ angle was 93.3° ± 8.8° preoperatively and 101.9° ± 6.3° postoperatively, increasing by 8.6° during stapedotomy (p

Bone conduction (BC) hearing devices have been used to improve hearing in patients with unilateral conductive hearing loss; however, the clinical results of improvement in the sound localization ability are still controversial. Transcranial transmission in BC may be an important factor affecting sound localization abilities. Transcranial or interaural attenuation, derived from energy attenuation during the BC process, is determined by the different transfer functions of multiple pathways and affected by the whole-head vibration modes. The purpose of this study is to analyze the frequency dependence of BC vibration modes of the whole head, the contribution of middle and inner ear pathways to BC hearing, and the relationship between transcranial attenuation results by dynamics measurement and hearing thresholds. Experimental studies of vibration modes and transcranial attenuation characteristics in BC are performed using scanning laser Doppler vibrometry (LDV) measurements on human cadaver heads. Differences in vibration modes between the excitation and contralateral sides are observed. Additionally, a multiscale human whole-head FE model, including the skull, bony outer ear, ossicular chains, and bony inner ear structures, is proposed to study the mechanism of BC in the human hearing system. After verifying the rationality of the FE model using mechanical impedance and frequency response data, the transcranial attenuation on the temporal bone surfaces and the middle ear structure is calculated in the FE model. Moreover, the vibration characteristics of bilateral ossicular chains and the cochlear bony wall are observed in the whole-head FM model to study their contributions to BC hearing. By analyzing the experimental and numerical results of the vibration modes and the frequency response of the whole head incorporating the ossicular chain and cochlear bony wall, the intrinsic relationship between the results of transcranial attenuation by 1D LDV, 3D LDV, and hearing threshold measurements is further investigated.

： Background: Baha Attract System was designed as non-skin penetrating bone conduction implant to minimize skin complication. However, there were insufficient studies on its long-time acoustic outcome and safety in microtia patients with auricle reconstruction surgeries, who have thinner retroauricular subcutaneous layer and theoretically vulnerable skin at the implant side. Objectives: To analysis the long-term hearing performance and soft tissue complications of Baha@ Attract System in microtia population. Study Design & setting: A prospective cohort study at single tertiary referral center. Patients: Twenty Mandarin-speaking patients with congenital bilateral microtia who were underwent Baha@ Attract implantation with or without auricle reconstruction surgeries simultaneously. Main Outcome Measure(s): Comparative analysis of audiological test results including hearing thresholds and speech recognition in quiet and in noise were pre- and post-operatively performed. subjective benefit as measured with the SSQ Scale. Soft tissue outcomes were monitored and documented. Results: The mean follow-up time was 36.11±3.30 months. Significant and stable improvements in hearing threshold and speech understanding in noise and quiet were demonstrated with aided condition. Subject evaluation revealed high level of patients’ satisfaction with the amplification in all the subscales. Adverse events including skin necrosis increased after one year post-operatively. Soft tissue evolution including sin thinning, erythema, epidermis atrophy, soft tissue atrophy, skin necrosis was seen or once developed in most of the participants. However, prevalence of severe soft tissue complication was not higher to non-microtia population. Conclusions: Baha@ Attract System provides favorable and stable hearing improvements for microtia patients. Combining plastic surgeries with implantation will not increase the prevalence of soft tissue complication. However, long-term soft tissue problems should be highly aware of even after one year post implantation. Key words: Baha Attract, microtia, hearing, soft tissue, skin necrosis

The synovial stapedio-vestibular joint (SVJ), which serves as a bridge between the stape and oval window, can be found in guinea pigs and most human adults. Unlike the fibrous SVJs in other animals, the contribution of the synovial SVJ to middle ear sound transmission remains unknown.In this study, we investigate whether sclerosis of the synovial SVJ contributes to frequency-dependent vibration of the ossicular chain and round window membrane (RWM).A model of SVJ sclerosis model was established in the guinea pig using 75% ethanol. A laser Doppler vibrometer was then used to measure vibrations of the RWM and the long process of the incus (LPI) under pure tone sound stimulations of 0.25-16 kHz. The influence of SVJ sclerosis was analysed by comparing structural vibration displacement between the normal and sclerosis groups.Both LPI and RWM vibrations significantly decreased at low frequencies after infiltration of ethanol, which caused SVJ sclerosis.SVJ sclerosis reduces low-frequency vibration of the ossicular chain and RWM in the guinea pig, which indicates that the synovial SVJ is vital to low-frequency sound transmission in the middle ear.Providing useful data for further research regarding middle ear biomechanics.

Besides the normal hearing pathway known as air conduction (AC), sound can also transmit to the cochlea through the skull, known as bone conduction (BC). During BC stimulation, the cochlear walls demonstrate rigid body motion (RBM) and compressional motion (CPM), both inducing the basilar membrane traveling wave (TW). Despite numerous measuring and modeling efforts for the TW phenomenon, the mechanism remains unclear, especially in the case of BC. This paper proposes a 3D finite element cochlea model mimicking the TW under BC. The model uses a traditional “box model” form, but in a spiral shape, with two fluid chambers separated by the long and flexible BM. The cochlear fluid was enclosed by bony walls, the oval and round window membranes. Contingent boundary conditions and stimulations are introduced according to the physical basis of AC and BC. Particularly for BC, both RBM and CPM of the cochlea walls are simulated. Harmonic numerical solutions are obtained at multiple frequencies among the hearing range. The BM vibration amplitude ( $$U_{{{\text{BM}}}}$$ ) and its relation with volume displacement difference between the oval and round windows $$(\Delta {\text{Vol}})$$ , as well as the pressure difference at the base of the cochlea ( $$P_{{{\text{SV}}}} \left( 0 \right) - P_{{{\text{ST}}}} \left( 0 \right)$$ ), are analyzed. The simulated BM response at 12 mm from the base is peaked at about 3 k Hz, which is consistent with published experimental data. The TW properties under AC and BC are the same and have a common mechanism. (1) $$U_{{{\text{BM}}}}$$ is proportional to $${\Delta }Vol$$ at low frequencies. (2) $$U_{{{\text{BM}}}}$$ is also proportional to $$P_{{{\text{SV}}}} \left( 0 \right) - P_{{{\text{ST}}}} \left( 0 \right)$$ , within 5 dB error at high frequencies such as 16 k Hz. This study partly reveals the common quantitative relations between the TW and related factors under AC and BC hearing.

The basilar membrane (BM) is the key infrastructure that supports the microstructure of cochlear acoustic function, and its interaction with lymph in the cochlea involves a complex, highly nonlinear coupling motion and energy conversion. In 1928, Nobel Laureate Gordon von Bekesy experimented and first discovered the traveling wave motion of the BM, thus uncovering the mystery of BM motion. However, with the further development of experimental technology in recent years, scientists have discovered that the traveling wave motion does not explain many experimental observations and phenomena associated with the detection of low-frequency sounds by the cochlea. Because the cochlea is very small and complex, Bekesy could only obtain medium- and high-frequency motion data for the BM but not low-frequency motion data. Based on a theory of mathematical physics and biology combined with data from medical and modern light source imaging experiments, a theoretical model of the spiral cochlea and a numerical model that conforms to the real human ear were established. The results reproduce the known traveling wave motion of the BM. Meanwhile, an exciting new finding has revealed a standing wave motion pattern at low frequencies. This newly discovered motion pattern intrinsically explains many experimental observations that could not be explained by the traveling wave theory. These results not only complement the low-frequency motion characteristics of the BM, but also probably reveal the mechanism of active phonoreceptive amplification in the cochlea, which has been a difficult problem to unravel in otology medicine.

Mast cells (MCs) play important roles in multiple pathologies, including fibrosis; however, their behaviors in different extracellular matrix (ECM) environments have not been fully elucidated. Accordingly, in this study, the migration of MCs on substrates with different stiffnesses was investigated using time-lapse video microscopy. Our results showed that MCs could appear in round, spindle, and star-like shapes; spindle-shaped cells accounted for 80-90 % of the total observed cells. The migration speed of round cells was significantly lower than that of cells with other shapes. Interestingly, spindle-shaped MCs migrated in a jiggling and wiggling motion between protrusions. The persistence index of MC migration was slightly higher on stiffer substrates. Moreover, we found that there was an intermediate optimal stiffness at which the migration efficiency was the highest. These findings may help to improve our understanding of MC-induced pathologies and the roles of MC migration in the immune system.

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.

Objective To investigate the effects of long-term moderate noise on hearing functions, MOCR, and MEMR. Methods Mice were exposed to the moderate noise (11.2 – 22.4 kHz, 80 dB SPL, 6 h/day, 4 weeks). Subsequently, the hearing functions, including threshold and input-output roles of ABR (auditory brainstem response) and cubic (2f1–f2) DPOAEs (distortion product otoacoustic emissions) were evaluated. Also, MEMR and MOCR were assessed shortly after or at four weeks following the termination of exposure to the noise. Results The mice's acoustic suppression reflex was strengthened, hearing functions and MEMR were unaffected four weeks after the moderate noise. For primary tones of 16, 20 and 24 kHz, the strengths of contralateral and ipsilateral suppression in the noise group were about double those recorded in the control group. In order to further determine whether the functional changes of the afferent or efferent nerves increased the strengths of acoustic suppression, the mouse's left ear was inserted the earplug, and then exposed the moderate noise for four weeks. The strengths of contralateral suppression at 16, 20 and 24 kHz were increased for the noise + earplug than for the control group and were indistinguishable between the noise + earplug and the noise group. While no significant changes were found in the strengths of ipsilateral suppression at all frequencies for the noise + earplug group compared with the control group. Under ketamine/xylazine anesthesia, the broadband suppressor noise did not stimulate the MEMR by 20 min post-induction at all frequencies in three groups. Conclusion Our data demonstrated that the long-term moderate noise-exposure strengthened mice's MOCR by changing its afferent nerves, and unaffected cochlear hair cells and type I spiral ganglion neurons.

Background As an alternative pathway to air conduction, bone conduction is a multipathway process that transmits sound energy to the inner ear through the skull in general. Based on this mechanism, bone conduction devices (BCDs) have been used widely in the rehabilitation of hearing loss. Although great efforts have been devoted to improving BCDs, drawbacks still exist in most categories of BCDs due to the complicated process of bone conduction. We hypothesized that if a bone conduction transducer was placed on the cochlea to stimulate it directly, the attenuation would be minimized, and the frequency dependency would be different from that of the vibratory response induced by traditional BCDs. This study aimed to explore the feasibility of direct promontory stimulation and to investigate its frequency-response characteristics. Methods Measurements were conducted in twelve cat ears. To stimulate the promontory directly, the floating mass transducer (FMT) of the Vibrant Soundbridge© (VSB) implant was glued to the promontory coupled with an oval window (OW) coupler. Auditory brainstem response (ABR) and laser Doppler vibrometry (LDV) measurements were used to evaluate the auditory response induced by the FMT. In both measurements, the FMT was driven by direct voltage stimuli. Results ABR waves could be induced under direct promontory stimulation by the FMT. In the frequency range of 1–12 kHz, the variation in the voltage threshold level were limited to 16 dB SPL with a maximum of 0.2 V at 1 kHz and a minimum of 0.04 V at 10 kHz. In the LDV measurements and the relative motion of the round window membrane (RWM) and the promontory were used to evaluate the cochlear response. The LDV results indicated a weak frequency dependency from 1 to 12 kHz. Conclusion Different from traditional stimulation via transcranial bone conduction, direct promontory stimulation is a new method in which a small bone conduction transducer stimulates the cochlear shell directly. The current experimental data demonstrate that it is feasible to generate sensations through bone conduction by stimulating the cochlea directly. Furthermore, the cochlear response induced by this type of stimulus in cats was weakly frequency dependent at frequencies ranging from 1 to 12 kHz. This study may provide a basis for the design of new transducers that can perform well over a wide range of frequencies.

Cochlear inner hair cell (IHC) ribbon synapses play an important role in sound encoding and neurotransmitter release. Previous reports show that both noise and aminoglycoside exposures lead to reduced numbers and morphologic changes of synaptic ribbons. In this work, we determined the distribution of N-methyl-D-aspartate receptors (NMDARs) and their role in the gentamicin-induced pathological changes of cochlear IHC ribbon synaptic elements. In normal mature mouse cochleae, the majority of NMDARs were distributed on the modiolar side of IHCs and close to the IHC nuclei region, while most of synaptic ribbons and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) were located on neural terminals closer to the IHC basal poles. After gentamicin exposure, the NMDARs increased and moved towards the IHC basal poles. At the same time, synaptic ribbons and AMPARs moved toward the IHC bundle poles on the afferent dendrites. The number of ribbon synapse decreased, and this was accompanied by increased auditory brainstem response thresholds and reduced wave I amplitudes. NMDAR antagonist MK801 treatment reduced the gentamicin-induced hearing loss and the pathological changes of IHC ribbon synapse, suggesting that NMDARs were involved in gentamicin-induced ototoxicity by regulating the number and distribution of IHC ribbon synapses.

A stabilized finite element scheme for the 3D cochlear fluid-structure interaction (FSI) problem is proposed. The FSI involves the interaction between the cochlear basilar membrane (BM) and its surrounding fluid. The BM is assumed to be an orthotropic membrane, governed by Mindlin plate theory. Since the cochlear fluid is an incompressible viscous fluid, mixed displacement/pressure element with Galerkin/Least-Square(GLS) stabilization is adopted. The fluid domain and solid domain are coupled between the interface with continuous displacement, and the fluid traction applies normal pressure load on the BM, causing the BM traveling wave. Based on this scheme, numerical simulations for the traveling wave are conducted on straight and spiral 3D cochlear models. The spiral effects are discussed by comparison between straight and spiral models. There is no significant difference for the traveling motion (both the BM magnitude and phase) at the middle-line of BM. A radial pressure tilt is found in the spiral model. The fluid pressure at inner areas is relatively lower than that at outer areas. This pressure tilt becomes especially obvious near the CF (characteristic frequency) location. Nevertheless, no obvious variation of the BM displacement in the radial direction is found in the current model.

The cochlea is an important structure in the hearing system of humanity. Its unique structure enables the sensibility to the sound waves of varied frequencies. The widely accepted model of the cochlea is expressed as a long tube longitudinally divided by a membrane named the Basilar Membrane (BM), into two fluid-filled channels. Based on various assumptions for the cochlear fluid and structure, simplified mathematical and mechanical cochlear models were developed to help to understand the mechanism of the complex coupled system in the past decades. This paper proposes a hydrodynamic numerical cochlear model with consideration of the Fluid-Structure Interaction (FSI). In this model, the cochlear lymph is considered as in a Newtonian viscous fluid, and the basilar membrane is modeled as a composite structure. The traveling wave is simulated. Also focusing on the pressure in the fluid field, the results are compared with studies of Peterson and Bogert, where it was assumed that the slow compressive waves are traveling along the BM. Furthermore, the transmitting time of the cochlear traveling wave is also discussed.

The traveling wave is the most important phenomenon in cochlear macromechanics. The behaviors of the traveling wave that greatly alter the auditory discrimination, are tightly related with the mechanical properties of the basilar membrane (BM) and its surrounding lymph. As an addition to the blanks of related researches, this paper focuses on some of the key parameters that affect the cochlear response most: the BM stiffness, damping parameters and the fluid viscosity. The influence of these parameters on the traveling wave is discussed, based on our former developed 2D finite element hydrodynamic cochlear model. Moreover, the traveling wave velocity and its transmitting time are calculated based on the simulating results. Although generally a rapid fall of the velocity from the cochlear base to the characteristic frequency (CF) location is confirmed, our quantitative analysis also indicates the traveling wave velocity may be both location and frequency dependent.