Middle Ear Transfer Function Research Articles

Influence of inner ear impedance on middle ear sound transfer functions

IntroductionFor experimental studies on sound transfer in the middle ear, it may be advantageous to perform the measurements without the inner ear. In this case, it is important to know the influence of inner ear impedance on the middle ear transfer function (METF). Previous studies provide contradictory results in this regard. With the current study, we investigate the influence of inner ear impedance in more detail and find possible reasons for deviations in the previous studies. Methods11 fresh frozen temporal bones were prepared in our study. The factors related to inner ear impedance, including round window membrane stiffness, cochleostomy, cochlea fluid and cochlea destruction were involved in the experimental design. After measuring in the intact specimen as a reference (step 1), the round window membrane was punctured (step 2), then completely removed (step 3). The cochleostomy was performed (step 4) before the cochlear fluid was carefully suctioned through scala tympani (step 5) and scala vestibuli (step 6). Finally, cochlea was destroyed by drilling (step 7). Translational and rotational movement of the stapes footplate were measured and calculated at each step. The results of the steps were compared to quantify the effect of inner ear impedance changing related to the process of cochlear drainage. ResultsAs the inner ear impedance decreases from step 1 to 7, the amplitudes of the METF curves at each frequency gradually increase in general. From step 6 on, the measured METF are significantly different with respect to the intact group at high frequencies above 3 kHz. The differences are frequency dependent. However, the significant decrement of rotational motion appears at the frequencies above 4.5 kHz from the step 5. ConclusionThis study confirms the influence of inner ear impedance on METF only at higher frequencies (≥3 kHz). The rotational motions are more sensitive to the drainage of fluid at the higher frequency. Study results that found no influence of cochlea impedance may be due to incomplete drainage of the cochlea.

Cetacean audiogram models

Modelling is an established alternative to in vivo audiometry. We produced finite element models (FEM) of hearing in minke (Balaenoptera acutorostrata) and humpback (Megaptera novaeangliae) whales and frequency place maps (FPMs; total hearing ranges) for these species plus right (Eubalaeglacialis) and blue (Balaenoptera musculus) whales with control data for bottlenose dolphins (Tursiops truncatus) and harbor porpoises (Phocoena phocoena) Anatomically derived FPMs were obtained from microCT scans, basilar membrane histology, and nanoindentation stiffness measurements. FEM simulations of frequency response peak sensitivities used middle ear transfer function (METF) and laser Doppler measurements of stapes footplate velocities. Frequency responses were measured for stimuli at bone versus tympanic membrane/glove finger sites to assess most sensitive input locations. Odontocetes had a high pass response with corner frequencies from 10 kHz to 30 kHz. Response frequencies extended to 125 kHz, the limit of our measurement capability. Mysticetes had a bandpass response characterized by peak sensitivity from 0.5 kHz to 2 kHz for stimuli at the glove finger. Preliminary audiograms show peak responses differ among baleen whale species but were generally between 20 Hz and 5 kHz with functional hearing ranges of 50 Hz–35 kHz for tested species. [Work supported by the Joint Industry Programme on Sound and Marine Life.]

Lumped element models of sound conduction in the human ear: A systematic review.

Lumped element models facilitate investigating the fundamental mechanisms of human ear sound conduction. This systematic review aims to guide researchers to the optimal model for the investigated parameters. For this purpose, the literature was reviewed up to 12 July 2023, according to the PRISMA guidelines. Seven models are included via database searching, and another 19 via cross-referencing. The quality of the models is assessed by comparing the predicted middle ear transfer function, the tympanic membrane impedance, the energy reflectance, and the intracochlear pressures (ICPs) (scala vestibuli, scala tympani, and differential) with experimental data. Regarding air conduction (AC), the models characterize the pathway from the outer to the inner ear and accurately predict all six aforementioned parameters. This contrasts with the few existing bone conduction (BC) models that simulate only a part of the ear. In addition, these models excel at predicting one observable parameter, namely, ICP. Thus, a model that simulates BC from the coupling site to the inner ear is still lacking and would increase insights into the human ear sound conduction. Last, this review provides insights and recommendations to determine the appropriate model for AC and BC implants, which is highly relevant for future clinical applications.

Real-time monitoring of middle ear prosthesis coupling

IntroductionIn reconstructive middle ear surgery, acoustic quality has received a high level of attention in recent years. Careful intraoperative selection and positioning of passive middle ear prostheses during tympanoplasty with ossiculoplasty is essential to ensure satisfactory sound transmission and postoperative hearing outcome. The reconstruction quality of the ossicular chain (OC) can be evaluated intraoperatively using a surgical assistance system which is based on a real-time monitoring system (RTM system) that acquires the transmission (middle ear transfer function (METF)) with electromagnetic excitation of the OC. In this experimental study, the METF with electromagnetic excitation of the (reconstructed) OC was compared to usual acoustic excitation and the benefit of the RTM system was investigated for the implantation of partial (PORP) and total (TORP) prostheses. MethodsLaser Doppler vibrometry (LDV) was used to measure the middle ear transfer function (METF) in 18 human temporal bones (TB). The RTM system uses electromagnetic excitation of the OC with a magnet placed on the umbo. Comparatively, measurements with the usual acoustical excitation, using an earphone in the external auditory canal, were performed. The measurements began with the intact OC, followed by real-time monitoring guided OC reconstruction with PORP and TORP. In addition, during the simulation of an intraoperative setting, the influence of the influence of opening (tympanomeatal flap lifted and pushed anteriorly) and closing (tympanomeatal flap folded back) the tympanic membrane on the measurements with the RTM system was determined. ResultsElectromagnetic and acoustic excitation of the intact and the reconstructed OC provided comparable METF. The application of the RTM system significantly improved the quality of the OC reconstruction. The METF increased by up to 10 dB over the entire frequency range during implantation of the PORP with positioning control by the RTM system. When using the TORP, the METF could be improved by up to 15 dB. The opening of the tympanomeatal flap did not affect the measurements with the RTM system at the reconstructed OC. ConclusionIn this TB study, we demonstrated that the quality of OC reconstruction (improved METF as a benchmark for improved transmission) could be significantly increased by means of a RTM system. Intraoperative studies should now be conducted to investigate to which quantitative extent the intraoperative reconstruction quality can be improved and whether or not this improvement also manifests in an increased (long-term) hearing outcome. This will enable conclusions to be drawn about the contribution of the intraoperative reconstruction quality to the (long-term) hearing outcome in the context of the conglomerate of various factors influencing the postoperative hearing outcome.

Effects of preloads on middle-ear transfer function and acoustic reflex in ossiculoplasty with PORP

IntroductionSurgical outcomes in ossiculoplasty with partial ossicular replacement prostheses (PORPs) are greatly influenced by the amount of preload imposed on the PORP. In this study, the attenuation of the middle-ear transfer function (METF) was experimentally investigated for prosthesis-related preloads in different directions, with and without concurrent application of stapedial muscle tension. Different PORP designs were assessed to determine functional benefits of specific design features under preload conditions. MethodsThe experiments were performed on fresh-frozen human cadaveric temporal bones. The effect of preloads along different directions were experimentally assessed by simulating anatomical variance and postoperative position changes in a controlled setup. The assessments were performed for three different PORP designs featuring either a fixed shaft or ball joint and a Bell-type or Clip-interface. Further, the combined effect of the preloads towards the medial direction with tensional forces of the stapedial muscle was assessed. The METF was obtained via laser-Doppler vibrometry for each measurement condition. ResultsThe preloads as well as the stapedial muscle tension primarily attenuated the METF between 0.5 and 4 kHz. The largest attenuations resulted from the preload towards the medial direction. The attenuation of the METF with stapedial muscle tension was reduced with concurrent PORP preloads. PORPs with a ball joint resulted in reduced attenuation only for preloads along the long axis of the stapes footplate. In contrast to the clip interface, the Bell-type interface was prone to lose coupling with the stapes head for preloads in the medial direction. ConclusionsThe experimental study of the preload effects indicates a direction-dependent attenuation of the METF, with the most pronounced effects resulting from preloads towards the medial direction. Based on the obtained results, the ball joint offers tolerance for angular positioning while the clip interface prevents PORP dislocations for preloads in lateral direction. At high preloads, the attenuation of the METF with stapedial muscle tension is reduced, which should be considered for the interpretation of postoperative acoustic reflex tests.

Assessment of Middle Ear Function Using Wideband Acoustic Immittance: Current Practices and Future Prospects.

Acoustic immittance tests have been used in clinical practice for the assessment of middle ear function since the 1960s. In the following decades, single-frequency admittance tympanometry has become a staple test of middle ear function in routine audiological practice, and to a lesser extent, multifrequency tympanometry. The acoustic properties of middle ear are best understood through physiological assays of its gain spectrum, tested over a wide range of frequencies; i.e., the middle ear transfer function. Yet, clinical assessment with multi-frequency tympanometry has been limited to frequencies below 2000 Hz. Thanks to advances in probe characterization techniques, measurements of impedance at frequencies beyond 2,000 Hz have become possible. These advances ushered in a new frontier for acoustic immittance research and paved the way for a host of new wideband acoustic immittance (WAI) measures that promised improved clinical assessments through better approximation of the transfer function and acoustic mechanics of the middle ear. Translational and clinical research further developed and refined WAI for clinical use through establishment of clinical norms, emergence of data in ears with conductive disorders, and demonstrated improvements in test accuracy of WAI over single-frequency tympanometry for a variety of clinical populations. Together with emergence of commercially available systems, since the mid-2000s, these developments signal the emergence of WAI testing as a standard audiological tool for the assessment of the middle-ear function. Although clinical adoption of this promising diagnostic technology is lagging, widespread adoption is expected with further refinement of WAI measures, and as updated clinical practice guidelines recommend the incorporation of WAI testing into clinical test batteries (e.g., JCIH, 2019).[1]

Fundamental Concepts for Assessment and Interpretation of Wideband Acoustic Immittance Measurements.

Assessment of middle ear impedance using noninvasive electroacoustic measurements has undergone successive developments since its first clinical application in the 1940s, and gained widespread adoption since the 1970s in the form of 226-Hz tympanometry, and applications in multifrequency tympanometry. More recently, wideband acoustic immittance (WAI) is allowing unprecedented assessments of the middle ear acoustic mechanics thanks to the ability to record responses over a wide range of frequencies. The purpose of this article is to present fundamental concepts for the assessment and interpretation of wideband measures, including a review of acoustic impedance and its relation to the mass, stiffness, and resistance components of the middle ear. Additionally, an understanding of the middle ear transfer function reveals the relationship between impedance and middle-ear gain as a function of frequency. Wideband power absorbance, a WAI measure, quantifies the efficiency of sound conduction through the middle ear over a wide range of frequencies, and can serve as an analogous clinical measure to the transfer function. The interpretation of absorbance measures in ears with or without a conductive condition using absorbance measured at ambient pressure and pressurized conditions (wideband tympanometry) is described using clinical case examples. This article serves as an introduction to the fundamental principles of WAI measurements.

Methods and reference data for middle ear transfer functions

Human temporal bone specimens are used in experiments measuring the sound transfer of the middle ear, which is the standard method used in the development of active and passive middle ear implants. Statistical analyses of these experiments usually require that the TB samples are representative of the population of non-pathological middle ears. Specifically, this means that the specimens must be mechanically well-characterized. We present an in-depth statistical analysis of 478 data sets of middle ear transfer functions (METFs) from different laboratories. The data sets are preprocessed and various contributions to the variance of the data are evaluated. We then derive a statistical range as a reference against which individual METF measurements may be validated. The range is calculated as the two-sided 95% tolerance interval at audiological frequencies. In addition, the mean and 95% confidence interval of the mean are given as references for assessing the validity of a sample group. Finally, we provide a suggested procedure for measuring METFs using the methods described herein.

Exploring Mechanisms Underlying Unexplained Air-Bone Gaps Post-Myringoplasty: Temporal Bone Model and Finite Element Analysis.

Air-bone gap (ABG) is an essential indicator of middle ear transfer function after myringoplasty. However, there is still uncertainty about the mechanisms behind unexplained ABGs in patients post-myringoplasty. The present study investigated these mechanisms using cadaveric temporal bone (TB) measurement and finite element (FE) modeling. Three conditions of tympanic membrane (TM) perforation were modeled with a perforated area of 6%, 24%, and 50% of the total TM area to simulate a small, medium, or large TM perforation of TB model. A piece of paper was used to patch the TM perforation to simulate the situation post-myringoplasty. In the FE model for post-operation, the material properties at the perforation area were changed. Measurement of TM vibration at the umbo was undertaken with a laser Doppler vibrometer (LDV). As the perforated area increased vibration of the TM at the umbo decreased in both the TB and FE models. But the reduction of TM vibration is more minor in the FE model than in the TB model. After the perforation was repaired, the displacement of TM at the umbo could not be recovered totally in the TB and FE models. In the FE model, the displacement of TM at the umbo decreased markedly when the cone shape of TM flattened, and the reduction was almost the same as that in the TB model in the condition of large perforation. The material properties and the anatomical shape of the repaired TM could influence the TM's modal motion and wave motion. Except for appearance and shape current clinical instruments are unable to resolve factors that affect TM motion. Consequently the ABG seen post-myringoplasty remains unexplained.

Creation of an incus recess for a middle-ear microphone using a drill or laser ablation: a comparison of equivalent noise level and middle ear transfer function

PurposeStudies have assessed the trauma and change in hearing function from the use of otological drills on the ossicular chain, but not the effects of partial laser ablation of the incus. A study of the effectiveness of a novel middle-ear microphone for a cochlear implant, which required an incus recess for the microphone balltip, provided an opportunity to compare methods and inform a feasibility study of the microphone with patients.MethodsWe used laser Doppler vibrometry with an insert earphone and probe microphone in 23 ears from 14 fresh-frozen cadavers to measure the equivalent noise level at the tympanic membrane that would have led to the same stapes velocity as the creation of the incus recess.ResultsDrilling on the incus with a diamond burr created peak noise levels equivalent to 125.1–155.0 dB SPL at the tympanic membrane, whilst using the laser generated equivalent noise levels barely above the baseline level. The change in middle ear transfer function following drilling showed greater variability at high frequencies, but the change was not statistically significant in the three frequency bands tested.ConclusionsWhilst drilling resulted in substantially higher equivalent noise, we considered that the recess created by laser ablation was more likely to lead to movement of the microphone balltip, and therefore decrease performance or result in malfunction over time. For patients with greatly reduced residual hearing, the greater consistency from drilling the incus recess may outweigh the potential benefits of hearing preservation with laser ablation.

Cartilaginous bending spring tympanoplasty: a temporal bone study and first clinical results

ObjectiveAnchoring grafts for tympanic membrane (TM) reconstruction in anterior and subtotal TM defects is essential to prevent medialisation and can be facilitated by cartilaginous bending spring tympanoplasty (CBST). The purpose of this study was to analyse the impact of spring cartilages on middle ear transfer functions and patient hearing levels.MethodsIn six fresh-frozen human temporal bones a cartilage graft (measuring 6 × 2 mm with a thickness of 0.1–0.2 mm) was formed into a ‘U’-shaped bending spring, to be placed between the medial tympanic wall and the tympanic underlay grafts. The stapes velocity for excitation by exponential sweeps from 400 to 10,000 Hz was measured with a laser Doppler vibrometer. The resulting middle ear transfer functions were compared with the reconstructed middle ear. For clinical evaluation, 23 ears in 21 patients with chronic otitis media and an intact ossicular chain were operated using CBST. At each follow-up visit, the patients underwent pure-tone audiometry and the Freiburg monosyllabic speech test at a presentation level of 65 dB SPL for the word recognition score (WRS).ResultsThe measured stapes velocities at one-third octave midband frequencies averaged 3.56 × 10–2 ± 9.46 × 10–3 (mm/s/Pa) compared to 3.06 × 10–2 ± 6.86 × 10–3 (mm/s/Pa) with the bending and underlay cartilage in place (p = 0.319; r = 0.32). The bending spring tympanoplasty reduced the transfer function by 1.41 ± 0.98 dB on average. In the clinical part of the study, the graft success rate was 96% (22 out of 23 patients) after a mean follow-up of 5.8 ± 2.4 months (min. 3.5 months, max. 12.0 months). The air–bone gap improved significantly by 6.2 dB (± 6.6 dB; p < 0.001; r = 0.69), as well as the WRS from 61.8 ± 33.3% preoperatively to 80.0 ± 20.9% postoperatively (p = 0.031; r = 0.35).ConclusionExperimental data as well as initial clinical results suggest that CBST is an effective method for reconstructing anterior or subtotal defects of the tympanic membrane with satisfactory audiologic results and graft success rates comparable to previously described methods. It can, therefore, be added to the arsenal of tympanoplasty techniques for anterior and subtotal TM perforations.

The impact of tympanic membrane perforations on middle ear transfer function

PurposeInjury or inflammation of the middle ear often results in the persistent tympanic membrane (TM) perforations, leading to conductive hearing loss (HL). However, in some cases the magnitude of HL exceeds that attributable by the TM perforation alone. The aim of the study is to better understand the effects of location and size of TM perforations on the sound transmission properties of the middle ear.MethodsThe middle ear transfer functions (METF) of six human temporal bones (TB) were compared before and after perforating the TM at different locations (anterior or posterior lower quadrant) and to different degrees (1 mm, ¼ of the TM, ½ of the TM, and full ablation). The sound-induced velocity of the stapes footplate was measured using single-point laser-Doppler-vibrometry (LDV). The METF were correlated with a Finite Element (FE) model of the middle ear, in which similar alterations were simulated.ResultsThe measured and calculated METF showed frequency and perforation size dependent losses at all perforation locations. Starting at low frequencies, the loss expanded to higher frequencies with increased perforation size. In direct comparison, posterior TM perforations affected the transmission properties to a larger degree than anterior perforations. The asymmetry of the TM causes the malleus-incus complex to rotate and results in larger deflections in the posterior TM quadrants than in the anterior TM quadrants. Simulations in the FE model with a sealed cavity show that small perforations lead to a decrease in TM rigidity and thus to an increase in oscillation amplitude of the TM mainly above 1 kHz.ConclusionSize and location of TM perforations have a characteristic influence on the METF. The correlation of the experimental LDV measurements with an FE model contributes to a better understanding of the pathologic mechanisms of middle-ear diseases. If small perforations with significant HL are observed in daily clinical practice, additional middle ear pathologies should be considered. Further investigations on the loss of TM pretension due to perforations may be informative.

The Effect of Ossicular Chain Disorders on Sound Transmission and Tinnitus Perception using Electrical Model

Human middle ear ensures sound transfer due its ossicular chain, any disorder or abnormalities in this structure leads to a conductive hearing loss (CHL). Tinnitus is a health problem, associated with hearing loss, it remains a devastating symptom. In this work, we present an electrical model of the human middle ear including middle ear cavities (ZMEC), tympanic membrane with ossicular chain (ZTOC), and stapes complex with cochlea load (ZSC). This model is modified to represent more closely the related pathologies affecting the middle ear. We will focus our analysis on ossicular chain disorder by studying the effect of increasing ossicular chain (OC) stiffness and mass in both normal middle ear structures and disconnected stapes superstructure. The change in middle ear structures and impedance allows us to simulate ossicular chain disorder effects and analyze their impact on sound transmission. This analysis allowed us to know if this disorder can eventually cause tinnitus. The results showed that the effect of ossicular chain anomalies can be studied based on frequency response of middle ear transfer function by applying only the principle of mass and stiffness, and demonstrate compared to clinical results the efficiency and simplicity of using the electrical model.

Measurement of middle ear transfer function in temporal bones using electromagnetic excitation: Comparison to sound excitation and evaluation of influencing factors

Hearing a sound produces vibrations of the ossicles in the middle ear, which can be measured in the micrometer to nanometer range. Destruction of middle ear structures results most commonly from chronic inflammatory diseases. In these cases, passive and active middle ear implants are used for reconstruction of the ossicular chain. The positioning of the implants depends primarily on the surgeon's experience. So far, no objective assessment has been conducted to affirm if the chosen positioning is the best in each specific case.We have established a new method, allowing us to measure the middle ear transfer function (METF) intraoperatively. Using the new method, a magnet is placed on the umbo of the malleus handle and is stimulated by a coil positioned underneath the head. The resulting vibration is measured on the stapes footplate using Laser Doppler vibrometry (LDV).Acoustic and electromagnetic excitation show comparable METF in lower frequencies, which differ up to 10 dB in frequencies over 1 kHz. The position of the coil does not play a relevant part in the METF, whereas the location of the magnet on the tympanic membrane highly impacts the METF. This technique demonstrates reproducible results.Electromagnetic excitation is comparable to sound excitation and is suited for measuring the METF. A stable positioning of the magnet on the umbo is essential in order to acquire valid data.

Significance of middle ear model for prediction of metabolic exhaustion of the auditory system

Modern day military noise is complex, involving irregular impulses riding on top of moderate continuous background noise. An accurate prediction of injury from complex noise exposure requires both a cochlear metabolic exhaustion (ME) model and an accurate middle ear model (MEM), accounting for acoustic reflex (AR) and annular ligament (AL) nonlinearities. An end-to-end biomechanical model including a ME model was developed that established a good correlation between the outer hair cell energy deficit (OHC-D) outcomes and the temporary threshold shift (TTS) data from chinchilla complex noise exposure, explained the data collected, and provided insights on the effect of complex noise exposure on outcomes, including the effect of inter-pulse Interval (IPI), shot sequence, and background noise. Literature data were used to derive the open ear and middle ear transfer functions (TF). In this paper, the model results are discussed with an emphasis on the MEM component. The differences in the end-to-end model results are compared between the new MEM and a MEM adopted from the improved AHAAH-ICE model that includes the AR and AL nonlinearities, with model parameters adjusted for chinchilla. The results show that the TFs from the two MEMs cannot be matched using mere parametric optimization, due mainly to the fact that the chinchilla middle ear is rather tuned to the higher frequencies compared to that of human. There is a need for an improved MEM for the chinchilla middle ear TF including AR effects.

A comparative study of avian middle ear mechanics

Sound and hearing play an important role in the lives of many birds, and studies have been published on the acoustic habitat of various species, as well as on various aspects of their hearing system. However the function of the middle ear remains largely unexplored, with existing studies focusing on either single species, or a very narrow range of species. In this article we report measurements of the middle ear transfer function in 39 taxonomically diverse avian species. We used laser vibrometry to measure the vibrations of the columellar footplate in response to tones played in each animal’s ear canal, and calculated the middle ear transfer functions.Transfer functions varied substantially across species, but appeared to follow common trends. Comparisons between the peak frequency in the transfer function and length/mass of the columella reveal a correlation between the three, however statistical analysis suggests that columellar length is a primary indicator of the peak frequency. These results provide a broad survey of avian middle ear function, and the observed trends provide a method with which to begin to predict the response of single ossicle middle ear systems.

Experimental investigation of the effect of middle ear in bone conduction

ObjectivesExperimental investigation of the contribution of the middle ear to bone conduction (BC) hearing sensation. MethodsExperiments were conducted on 6 fresh cadaver whole head specimens. The electromagnetic actuators from a commercial bone conduction hearing aid (BCHA), Baha® 5 SuperPower and BoneBridge (BB), were used to provide stepped sine stimulus in the range of 0.1–10 kHz. The middle ear transfer function (METF) of each cadaver head was checked against the ASTM F2504-05 standard. In a first step, the stapes stimulus into the cochlea, under BC, was estimated based on the differential velocity between the stapes footplate and the promontory. This was based on sequential measurements of the 3D velocity of the stapes footplate and the promontory. In parallel, the differential tympanic membrane (TM) pressure was recorded by measuring sound pressure in the middle ear and in the external auditory canal each measured 1–2 mm from the TM. The measurement procedure was then sequentially repeated, after: a) opening the middle ear cavity; b) ISJ interruption; c) closing the middle ear cavity. At the end, the velocity at each actuator is measured for comparison purposes. Stapes footplate and promontory motion was quantified as the 3D motion at a single measurement point via a three-dimensional laser Doppler vibrometer (3D LDV) system. The combined motion was used for all motion parameters. ResultsThe METF, based on the combined motion, matches better to the ASTM standard, making the measurements resilient to oblique measurement directions. The Baha actuator produced ∼10 dB SPL more output than the BB above 2 kHz. This resulted in 2–5 dB increase in the differential pressure across the TM, after middle ear cavity opening, for Baha stimulation, and up to 9 dB drop (around 2 kHz) for BB stimulation. The differential stapes motion follows linearly the level of motion of the stimulation area, however, it is affected by actuator resonances in a more complex way. Interruption of the ISJ, reduces the differential motion of the stapes with 1–5 dB, only at 1–3 kHz. ConclusionCombined velocity more objectively describes the stapes and skull motion, than any individual motion component. The state of the ME cavity and the ISJ affect the cochlear input of the stapes, however, the effect is limited in frequency and magnitude.

Wideband tympanometry findings in inner ear malformations

ObjectiveThe deficits in the cochlea which is at the one end of the ear sound transfer system, may effect middle ear functions. Wideband typanometry (WBT) is frequently used to evaluate these transfer functions which play a crucial role in setting the impedance matching between the external ear and the cochlea. To this end, the aim of this study was to investigate the ear transfer functions in inner ear malformations via WBT, and to question whether these functions change depending on the types of inner ear malformation. MethodsThis prospective case-control study was conducted in a university hospital. One hundered-fifty-seven ears (aged 3–37 years) under the groups of cochlear hypoplasia, incomplete partition I, incomplete partition II, cochlear aplasia and complete labyrinthine aplasia were evaluated. In the control group, 30 ears with normal hearing were enrolled and WBT was carried out. Tympanometric peak pressure, equivalent middle ear volume, static admittance, tympanogram width, resonance frequency, average wideband tympanometry and absorbance measurements were analyzed. ResultsThe inner ear malformation groups demonstrated statistically significant differences than the control group and from each other in terms of traditional tympanometric parameters and WBT test parameters (p<0.05). The most remarkable difference was between the group of complete labyrinthine aplasia and the control group, most probably because of complete labyrinthine aplasia’s structural effects. However, on some parameters, incomplete partition II and the control group showed similarities. In absorbance measurements, there was significant difference between all patient groups and the control group, especially at high frequencies (p<0.05). The largest difference was between the control group and the group of complete labyrinthine aplasia which has revealed the lowest absorbance values (p<0.05). In averaged-wideband tympanogram analysis, all patient groups obtained a lower amplitude peak than the control group; complete labyrinthine aplasia group had the flattest peaked amplitude, while the incomplete partition II group had a near-normal curve. ConclusionThe results of the study revealed the distinctive effects of inner ear malformations in middle ear transfer functions. It is concluded that the absence of inner ear structures causes negative effects on energy absorbance and the other transfer functions of the middle ear. WBT may provide additional information on diagnosis of patients with inner ear malformations.

Study of age-related changes in Middle ear transfer function

Osteoporosis (OP) is common with advancing age. Several studies have shown a strong correlation between OP and otosclerosis. However, no studies have investigated OP of the malleus, incus or stapes in the human middle ear, its effect on middle ear transfer function. Here, we investigate whether these three ossicles develop OP, and how this affects middle ear transfer function. The effect of OP on middle ear transfer function was investigated in simulations based on a finite element (FE) method. First, the FE model used in our previous study was refined, and optimized by introducing viscoelastic properties to selected soft tissues of the middle ear. Then, the FE model was used to simulate OP of the three ossicles and assess its influence on middle ear transfer function. Other possible age-related changes, such as stiffness of the joints or ligaments in the middle ear, were also investigated. The results indicated that OP of the ossicles could increase the high frequency displacement of both the umbo and stapes footplate (FP). However, the stiffness of the middle ear soft tissue can lead to the decrease of middle ear gain at lower frequencies. Furthermore, loosening of these joints or ligaments could increase displacement of the umbo and stapes FP. In conclusion, although age-related hearing loss is most commonly conceived of as sensorineural hearing loss (SNHL), we found that age-related changes may also include OP and changes in joint stiffness, but these will have little effect on middle ear transfer function in elderly people.

A lumped-element model of the chinchilla middle ear.

An air-conduction circuit model was developed for the chinchilla middle ear and cochlea. The lumped-element model is based on the classic Zwislocki model of the same structures in human. Model parameters were fit to various measurements of chinchilla middle-ear transfer functions and impedances, using a combination of error-minimization-driven computer-automated and manual fitting methods. The measurements used to fit the model comprise a newer, more-extensive data set than previously used, and include measurements of stapes velocity and inner-ear sound pressure within the vestibule and the scala tympani near the round window. The model is in agreement with studies of the effects of middle-ear cavity holes in experiments that require access to the middle-ear air space. The structure of the model allows easy addition of other sources of auditory stimulation, e.g., the multiple sources of bone-conducted sound-the long-term goal for the model's development-and mechanical stimulation of the ossicles and round window.