Middle Ear Mechanics in Research and Otology

PREFACE.

CONTENTS.

Using interferometry and micro-tomography in combination, we obtained a gold mine of data, embedding a complete description of the middle ear and its spatial motion, all for the same ear! Studies are performed on fresh temporal bones (5 cat, 4 human) due to the limited in-vivo accessibility. Vibrations of the 3 middle ear ossicles are first measured from different viewing angles. Coordinates of points on the chain are recorded to define the spatial position of the ossicles. Assuming rigid body behavior, 3-D motion parameters for translation and rotation are calculated for each ossicle separately.

In a second step the experimental middle ear is scanned using x-ray tomography and a dedicated 3-D anatomical model for the ossicular chain is constructed.

The data are used to study middle ear vibration in a direct, visual way by animating the 3-D models of the 3 ossicles. For cat the classical “rotation about a fixed axis” mode is only approximately present at low frequencies (below 1.5 kHz). Around 10 kHz, the umbo and the stapes footplate vibrate in phase opposition! The animation clearly shows how this is possible.

In human, large slippage in the malleus-incus joint, even at low frequencies, is most remarkable. Slippage has also been mentioned in studies by other investigators, but we are aware that part may be due to the fact that only bones of persons over 80 could be measured.

The data can be also be used in innumerable quantitative ways. As the motion of every point of the ossicular chain can be calculated we compared umbo motion to footplate motion as a measure of the middle ear transfer, compared motion of the lenticular process and stapes head to study joint slippage. We also calculated the kinetic energy of the ossicles which makes it possible to evaluate transmission losses in the middle ear.

The middle ears of all mammals have the same components, which vary in size and configuration among species. It is generally presumed that some of these structural variations benefit hearing behavior and survival in a species’ niche, but testing specific hypotheses for evolutionary mechanisms is difficult because of multidimensional differences among species. To narrow the variation we have focused on the cat family, Felidae, in which the 36 species are similar in their structure and predatory life style, but vary in size, habitat, and lineage. Our measurements of ear and skull dimensions from 400 museum specimens allow searches for structural relations to ethological variables. Correlations of ear structure with skull “shape” show that species with relatively wide anterior skulls are most likely to have an unusual location of the bony septum that divides the felid middle-ear airspace into two sub-cavities; the 8 species with this ear-skull structural combination all live in relatively open habitiats. The assignment of these 8 species to several different lineages by recent taxomomic studies suggests that this set of features evolved more than once. Speculation about the adaptive value of this arrangement of the septum could suggest testable hypotheses. Habitats with few trees allow a hunting cat to cover a large territory. Open habitats also permit low-frequency sounds to propagate with small attenuation, which allows detection of inter- and intraspecies sounds over large distances. Percepts from the received signal that are important to survival include the direction of the sound source, the nature of the source (e.g. intraspecies or predator) and the signal’s meaning (e.g. kitten alarm call). A general hypothesis is that the unusual septum location provides high sensitivity for low frequency sounds along with preservation of spectral features that provide cues for the percepts. The wide facial skull of these species could be adaptive in improving olfactory sensitivity in detection and identification of conspecifics, e.g. invaders of one’s territory.

Sound transfer in the physiological range can be described by linear mathematical models but for pathological cases, reconstructions or high sound pressure a nonlinear description is necessary. This leads to more complicated equations and additional parameters are to determine from specific measurements and clinical observations. Classical approaches known from frequency domain are no more applicable for the solution and the principle of superposition is not valid. Basic relations for the nonlinearities of ear drum, incudo-malleolar and incudo-stapedial joints, the ligaments and annular ring are taken into account and simulations of dynamical behavior are carried out. Particularly, the case of a subluxed incudo-stapedial joint and the contact between passive or active middle ear implants and the ossicles is considered for moderate and intensive excitation as well as static pressure variations in the ear canal, tympanum or vestibulum. Changes in the dynamical characteristics like shift of natural frequencies, attenuation of amplitudes and appearance of distortion products influence the hearing impression. They can be detected by measurements and interpreted on the base of the stated models.

Laser Doppler vibrometer measurements of the sound induced velocity of the umbo in patients and human subjects can be used to test models of middle-ear function and determine structural variables important to understanding the function of the human middle ear. Three issues are discussed. (1) Quantification of the functional compliances in the human middle ear: umbo-velocity measurements in cases of confirmed ossicular interruptions and fixations are used to localize the sources of middle-ear compliance. Stapes fixation emphasizes the role of any ossicular shunt compliance in the ossicular joints. Ossicular interruption shorts out the annular-ligament joint compliances and helps define the compliance of the tympanic membrane. Measurements in the normal ear reveal the action of all three compliances. (2) Manipulations of middle-ear transformer ratio: Umbo-velocity measurements in patients after successful stapedectomy are used to test and refine a simple transformer model of middle-ear function. The replacement of the stapes footplate with the smaller piston of the prosthesis causes a large decrease in the mechanical load on the middle ear and should produce larger ossicular motion. Comparisons between the increased umbo velocity and the hearing level in post-stapedectomy ears reveal the effect of alterations of the middle-ear transformer and the removal of the annular ligament impedance on hearing function. (3) Manipulations of cochlear load: Umbo-velocity measurements in patients with superior semicircular canal dehiscence are used to test models of the effect of the cochlear load on middle-ear function. Such dehiscences reduce the load on the middle ear in specific frequency ranges. Whether alterations in inner-ear load are apparent in the umbo motion depends on the degree to which the normal load influences middle-ear function.

Studies of the vibration modes of the stapes in response to acoustic stimulation of the normal ear have revealed a complex movement pattern of its footplate. At low frequencies the vibrations are predominantly piston-like, but they become increasing rocking-like at middle and high frequencies. These complex vibrations can be decomposed into a translational displacement and two rotational movements around the long and short axes of the stapes. The rotational components produce no net volume displacement of the cochlear fluid at some distance from the footplate. Therefore, in the classical theory the rotational motion of the stapes is considered as lost energy that is not transformed into a hearing sensation. It was the goal of this ongoing study to test this hypothesis experimentally in guinea pigs. A piezoelectric device was used to stimulate the stapes superstructure at various frequencies and in various directions in order to induce different movement patterns. The movement of the stapes footplate was monitored by means of a scanning laser Doppler interferometer. The evoked response in the cochlea was monitored by measuring the cochlear microphonic potential. These experiments demonstrate that the cochlea is also stimulated by rocking-like motion of the stapes, since when this type of motion was increased, less translational movement was necessary to induce an equal cochlear response.

The forward middle-ear pressure gain, the reverse middle-ear pressure gain, the reverse middle-ear impedance, and the cochlear input impedance from the same human cadaver temporal bone preparations were recently reported (Puria, 2003). These measurements along with impedance measurements of the sound delivery system are used to estimate for the first time the A, B, C, and D parameters of a two-port matrix representing the human middle ear. One advantage of these parameters is that they are independent of the cochlear and ear canal loads. The empirically derived two-port model elements are used to estimate the parameters of a circuit model representing the eardrum as a transmission line previously developed for the cat middle ear. Parameters of the model were adjusted until a improved fit to the two-port data was obtained. The revised circuit model describes forward and reverse middle ear pressure gains and reverse middle ear impedance better than in the previous models.

Acoustic time delay of human middle ear was studied using a laser Doppler vibrometer system. Eleven fresh human temporal bones with intact middle and inner ear were measured the peak to peak displacement and phase on umbo and stapes footplate. The average acoustic time delay in middle ear was 89 µs, which was constant at a measured frequency range from 0.1 to 10 kHz. The 89 µs delay means when malleus moves to inward, stapes footplate moves to outward at 5.6 kHz. After the fixation of ossicular jionts with cyanoacrylate glue, the time delay was reduced to 35 µs for sound transmission between umbo and stapes footplate. The delay seems to be caused by the slippage of the ossicular joints, not only I-S joint but also M-I joint.

The ossicular motion of the incudo-malleolar complex was measured by means of Laser Scanning Doppler Vibrometry (LSDV). A multi-sine signal containing 41 frequencies between 0.5 and 10 kHz served as acoustic stimulus. A common virtual coordinate system was defined for malleus and incus providing three degrees of freedom for each of them, one translation and two rotations. For both ossicles the three motion components were evaluated based on the rigid body motion equation. The transmission from the malleus to incus was calculated for each component. At low frequencies (<1kHz) small transmission losses of about 30% (-3 dB) were observed. Between 1 and 3 kHz these losses rapidly increased and reached values of 90% (-20 dB) at between 3 and 10 kHz. To which degree the mobility of the incudo-malleolar joint (IMJ) was responsible for sound transmission losses was tested by experimentally fixing the joint. The experiment revealed that the IMJ-mobility causes substantial sound transmission losses at higher frequencies (> 2 kHz) but not at low frequencies (< 1.5 kHz).

Three-dimensional motions of the isolated malleus-incus complex driven by a magnet-coil system were studied with measurements and an elastic model, which allowed slippage at the incudo-malleolar joint and bone deformation. Below the first resonance of 550 Hz, the motion was purely rotational, while complicated motions including slippage at the joint, were observed above the first resonance. The measurements show for the first time, that at the incudo-malleolar joint there is rotational motion at both the x-axis and z-axis.

The size and stiffness of the middle ear are different between individuals, and the effects of these differences on middle ear transfer function have not been clarified. In this study, using finite-element middle-ear models, the effects of individual differences in the size and stiffness of the middle ear on its transmission characteristics were analyzed. The individual differences in the size on the middle ear were found to slightly affect the transfer function. The effects of Young’s modulus of the ligaments and incudostapedial joint on the transfer function were significantly large compared to those of the other parts of the middle ear.

In literature, data of eardrum thickness is only available at a small number of measuring points by means of conventional light microscopy. The membrane had to be fixed, dehydrated, stained and decalcified to obtain histological sections. This process induces shrinking and hence influences the thickness measurements.

We have used an optical sectioning technique and developed a procedure that can be applied for quantitative thickness measurements of fresh tissue. By this procedure, measured data is corrected for the effects caused by refractive-index mismatch to obtain exact thickness. We developed a numerical correction procedure to obtain calibrated data from confocal depth measurements.

We present a quantitative comparison of thickness measurement between a fresh eardrum and the same membrane in the successive stages of preparation. On the basis of this analysis it becomes possible to quantify shrinking artifacts on histological sections.

In a first stage, the eardrum was dissected out of the fresh temporal bone and optical depth sections perpendicular to the eardrum’s surface were recorded with a confocal microscope. From adjacent images along anterior-to-posterior lines across the membrane, several thickness profiles were obtained. Next, the tissue was fixed. Thickness was measured along the same lines. In a third stage, the tissue was preserved in Cialit for six days, where after and thickness was measured along the same lines. In the last stage, the tissue was decalcified, dehydrated and stained before slicing it with a microtome. Histological sections were studied with a conventional light microscope to obtain thickness data at the same positions as before.

This study shows no significant difference in thickness between the untreated, fixed and in-Cialit-preserved eardrum. There is, however, a large difference in thickness between the preserved and the prepared eardrum. The preparation method to obtain histological sections does induce a shrinking effect up to 25 %.

The sound transfer of the reconstructed middle ear is influenced by many biological and mechanical factors. One of these factors is the prosthesis coupling to the stapes head and to the tympanic membrane. The Dresden Finite Element model of the middle ear was used to calculate the sound transfer function before and after reconstruction with a PORP (partial ossicular replacement prosthesis). The influence of prosthesis size and position, the influence of interposed cartilage and the contact to the stapes head were studied. The same questions were investigated on fresh temporal bones using a Laser- Doppler-Interferometer.

Prosthesis position at the tympanic membrane and the size of the prosthesis head strongly influenced the middle ear sound transfer, whereas the thickness of a small cartilage island can rather be ignored. A prosthesis head diameter of 3 mm, a prosthesis position near the umbo and a cartilage thickness of 0.5 mm were found to give good results. Variation of the prosthesis design can influence the coupling to the stapes head.

An optimal middle ear sound transfer can be reached for a prosthesis position at the malleus as well as at the tympanic membrane. Hearing results can be improved by prosthesis size and cartilage thickness variations. A new prosthesis design was developed to achieve a better coupling to the stapes head.

Evidence exists for flexibility in the ossicular chain. This evidence includes the observation that patients with otosclerotic lesions sufficient to cause a substantial reduction in stapes mobility and conductive hearing loss show only small reductions in low-frequency umbo velocity. In models of the middle ear, ossicular flexibility has often been assigned to the incudostapedial (I-S) joint – the incudomalleal (I-M) joint is assumed rigid – and this presumed flexibility is generally not well described. We introduce flexibility in the I-M joint in a simple middle-ear model to explain the discrepancy in reductions in umbo and stapes velocity at low frequencies observed in human temporal bones with simulated stapes fixation by Nakajima et al. (2003a,b). We determine the magnitude of I-M joint flexibility from measurements of low-frequency relative rotational velocity (Willi et al., 2002) and assume the I-S joint is rigid. The relationship between umbo and stapes velocities predicted by the model for normal ears and the reduction in umbo velocity predicted for various degrees of stapes fixation (modeled by reductions in annular ligament compliance) are a good match to experimental data in temporal bones and to clinical data in patients with stapes fixation. Reductions in umbo velocity due to stapes fixation are successfully predicted by varying a single model parameter, the annular ligament compliance, at the site of fixation.

Round window movements are often used as proxy measures of stapes footplate movements, when the stapes footplate is not accessible. This assumption, particularly after middle ear reconstruction has been poorly explored. Our aims were 1) to measure round window movements at several sites to determine if they are all equal 2) to examine the stapes/round window movement ratio (SRWR), in both intact and reconstructed ears. We particularly wished to examine how reconstructions that apply tension to the stapes footplate and change its static location in the oval window changed the SRWR. Using fresh unfrozen cadaveric temporal bones, we measured the SRWR and round window movements at several sites. The middle ear was reconstructed with prostheses from the eardrum to the stapes head under 3 different degrees of tension (loose, medium and tight). Our results show that the human round window does not move uniformly. The effects of reconstruction are that the amount of round window movement decreases per unit stapes displacement, but there is no graded effect with increased tension. The stapes exhibits increasing phase lag with respect to the round window with increased tension following reconstruction. There are several possible explanations for this, but the most likely is that the round window breaks up into different vibration modes, and this may explain the apparent SRWR changes.

Conclusions: The human round window membrane is not always a proxy measure of stapes movements. The location of measurement is important. The degree of tension on the stapes will affect the amount of measured round window movement at the center of the round window.

Traditional middle-ear immittance measurements are usually represented as plots depicting how the sound pressure of a probe tone in a sealed ear canal varies with the static air pressure applied by the instrument’s pump to the eardrum. The standard probe tones are low-frequency ones (226 or 660 Hz, typically) but multifrequency immittance instruments extend the measurements up to 2 kHz. Their outcomes are chiefly interpreted in terms of the physiological or pathological response of the tympanic membrane. If, instead of focusing their attention on the tympanic membrane, experimenters wished to study the ear’s impedance, it would be more straightforward to design plots representing what happens to a probe tone as a function of frequency, at a given static pressure in the ear canal. Presumably, such an approach might help to identify other useful characteristics of the ear, such as the possible contribution of the stapes’ annular ligament, or of the cochlea, to the ear’s impedance seen from the ear canal. For this purpose, we present here an attempt at plotting the outputs of a commercially available multifrequency immittance equipment (Grason Stadler GSI 33), that is, the two complex components B –susceptance- and G –conductance- of admittance Y from a sample of 25 ears from healthy normally-hearing young adults, at fixed static pressure (changed stepwise from –400 to +200 daPa) across probe frequency from 0.2 to 2 kHz (11 regularly spaced frequency steps).). A smaller sample of 5 ears from people with pure sensorineural hearing loss due to chronic (occupational) noise exposure was also measured with the same protocols. Differences among normal ears were such that empirically, two subgroups could be defined on the basis of different frequency dependences of B and G at 0 daPa. Other differences between normal and deaf ears are discussed.

The proliferation and differentiation of middle ear epithelial cells are essential in both normal and diseased middle ear. The former is engaged in physiologic growth and renewal of the epithelium and the latter is involved in pathologic changes of the epithelium such as mucous cell metaplasia and ciliated cell proliferation in otitis media. In this study, we used a temperature-sensitive large T-antigen (the SV40 mutant) to transduce and immortalize the primary culture of middle ear epithelial cells. SV40-immortalized middle ear epithelial cells have been cultured for >60 passages and are stable morphologically. Their non-immortalized parent cells died at the second passage. Immortalized middle ear epithelial cells carrying the SV40 mutant show a monolayer, cobblestone-like growth pattern. The cell line expresses characteristic middle ear mucosal molecules such as mucins, keratins, collagens, etc. It also responds to temperature changes, namely, cells proliferate at 33°C, when the SV40 antigen is active, and differentiate at 39°C, when the SV40 antigen is inactive. Therefore, we, conclude that a temperature-sensitive middle ear epithelial cell line has successfully been established.

The present study was carried out to investigate whether BMP-2/ collagen composites are appropriate as a columella material for ossiculoplasty. With a pellet of about 1×1×3 mm recombinant human bone morphogenetic protein-2 (rhBMP-2)/ collagen composites (the experimental group), or collagen only (the control group), was implanted as a columella into the tympanic cavity and was laid between the promontorium and the perforation of the tympanic membrane. All composites were in the process of ossification or have ossified according to their developmental stages and were covered with a single squamous or cuboidal epithelium. Collagen was still seen in the center of the composites at 4weeks, but it was not observed 6 weeks after implantation. At 24 weeks, a large proportion of the formed bone marrow was replaced by adipose tissue. During the observation periods, severe foreign body reaction, carcinogenic reaction or bone distractions were not observed. Columella tissue-engineered by these composites was persistently stable as assessed by histological examination. rhBMP-2/collagen composites are potentially an ideal implant for ossiculoplasty.

Several materials have been used in the application of mastoid cavity obliteration during surgery for cholesteatoma; however, nothing has won universal acceptance. Through the advancement of tissue engineering, bone morphogenetic protein –2 (BMP-2)/collagen composites have been elucidated as inducers of heterogenic bone formation. This study was performed to investigate whether these composites are potentially obliteration materials for use in the mastoid cavity by using an animal experimental study. The composites were implanted in the rat mastoid to investigate whether new bone would be tissue engineered in the mastoid and if so, whether the newly formed bone was stable. The composites were examined histologically over a 24 week period. The composites implanted in the rat mastoid were able to tissue engineer new bone, and the newly formed bone was stable as assessed histologically, with almost normal bone structure, that was not resorbed during the 24 week period. Adverse immunological reactions were not found during our observation. Bone that was tissue engineered by the BMP-2/collagen composites was stable as assessed by histological examination and persisted in the rat mastoid. The present study shows that the composites have the potential to become real materials for use in mastoid obliteration.

Middle-ear behavior interferes with sound transmission to and from the cochlea so that cochlear potentials and otoacoustic emissions (OAE) reflect middle ear status even though the cochlear function itself may remain stable. On the other hand, static intracochlear pressure (ICoP) influences middle ear properties through the mechanical characteristics of its stapes boundary. We present here the outcomes of two experiments in Menière patients with alleged dysregulation of ICoP during an attack, one with glycerol intake, and the other with body tilt and attendant intracranial pressure (ICP) and ICoP modulation. No direct access to ICoP is currently available without opening the bony labyrinth, however, ICP has been shown to induce distinctive changes in OAEs: they could be taken into account simply by assuming that the resulting stapes displacement was accompanied by a stiffness increase of its ligament (Buki et al., 1996, Avan et al., 2000). We show here that glycerol intake as well as body tilt induced OAE changes typical of ICoP change, with a large phase shift peaking around 1 kHz. The fact that meanwhile, almost no magnitude change was observed, and likewise, that pure-tone audiograms remained virtually unaltered, precludes any big change in cochlear function. Intriguingly, the response of symptomatic ears to body tilt was greatly exaggerated in a vast majority of cases with residual OAEs (about half the ears, while the remaining ones obviously had to be discarded). Fine middle ear analysis provides useful, unambiguous hints of ICoP changes, and the present results confirm their abnormality (as far as the statistical meaning is concerned) in the otherwise mysterious Menière disease. Yet the reason for such abnormalities in relation to posture remains elusive.

The present review argues that the performance of the middle ear of amniotic vertebrates approaches that of an ideal pressure transformer over a wide range of frequencies. Firstly, we note that sensitivity at ultrasonic frequencies comparable to sensitivity at lower frequencies has been demonstrated in the gerbil ear for stapes vibration, pressure in scala vestibuli near the stapes, basilar-membrane responses near the round window and compound action potential thresholds. Secondly, we show that the bandwidth of stapes velocity magnitude is greater than that of behavioral thresholds in gerbil, turtle, pigeon, guinea pig, bat and chinchilla. Thirdly, we question the validity of ossicular vibration data from cadaveric temporal bones and suggest that the middle ears of living humans are not exceptionally narrow-band among those of amniotic vertebrates and actually provide an input to the cochlea with bandwidth commensurate to, or exceeding, that of the audiogram. Fourthly, we show that phase-vs.-frequency curves of pressure in scala vestibuli in gerbil, stapes vibration in gerbil and chinchilla have roughly constant slopes, consistent with the idea that middle-ear mechanisms involve spatially distributed components arranged as a transmission line. Such transmission line components apparently act to selectively boost high-frequency vibrations at the incudo-stapedial joint (as shown in chinchilla and guinea pig) and/or at the malleus-incus complex (as seen in cat). The same components may convert the complex motions of the tympanic membrane into the simple, piston-like motion of the stapes.

The aim of this study was to determine the feasibility of an anatomically shaped incus prosthesis for reconstruction of the incus·absent ossicular chain. Conductive hearing loss caused by a damaged or missing incus is typically treated using a columella prosthesis. In the intact middle ear, the natural incus attaches to the malleus head, whereas columella reconstructions normally connect to a point on the malleus handle. An in vitro study and a finite-element model were used to evaluate the acoustic performance of an anatomically shaped incus replacement prosthesis (IRP) made from ionomeric cement, to determine the extent to which it can transmit vibration in a manner similar to that of the original incus. The results were compared with those of a columella reconstruction. The in vitro and computer IRP models gave similar stapes motion to that of the intact incus. The IRP model transmitted much more vibration at all frequencies than a modelled PORP prosthesis, but the performance of the columella reconstruction improved greatly when it was made from a stiffer material.

We often see poor sound transfer characteristics after ossicular chain reconstruction with prostheses. Large static displacements of the remaining middle ear structures lead to tension in the ligaments or dislocation of the prosthesis. The ideal solution is a prosthesis with automatic length adjustment. We did numerical simulations with prostheses with spring, friction, damping and buckling elements and our Finite Element model of the middle ear. The best sound transfer characteristic and length variability was achieved with a prosthesis with a damping element and a small spring.

We have previously demonstrated the feasibility of using a malleus head to stapes head ‘incus replica’ prosthesis (IRP) to replace the incus, The original design required the use of cement to attach the prostheses to the residual ossicular chain. Although this arrangement produced satisfactory hearing, we were concerned that the larger malleus movements generated by changes in static pressure might carry the risk of cochlear damage. We have evaluated a new ‘cementless’ IRP design in fresh human temporal bones. The pressure in the external auditory meatus was varied between + 400 and - 400 daPa using a tympanometer. The pressure delivered was confirmed using a digital pressure gauge. The motion of the normal and reconstructed chain was observed through an anterior approach and recorded as a series of digital video clips. When a conventional malleus handle to stapes head prosthesis is used the stapes moves in and out of the vestibule. However, a motion similar to that observed for the intact ossicular chain occurs when the ‘cementless’ IRP is in situ.

Cochleo-vestibular pressure measurements in human temporal bones show a significant gain difference of 6 dB between the Hydroxlapatite MSH & MFP-PORP designs. This 6 dB difference is also seen in the clinical audiological data of patients fitted with the 2 PORP designs. The MFP-PORP outperformed the MSH-PORP, by 6 dB, across the speech frequencies. Surgeons performing ossiculoplasty may wish to consider using a MFP-PORP design to achieve a better post-operative audiological result, even when the stapes suprastructure is intact.

Many investigators have shown that the three-dimensional movements of the stapes footplate in the intact middle earner ear are a complex mixture of rotational and translational movements. This is particularly true at higher frequencies. The “rocking ratio” (RR) is a measure of the relative rotational and piston-like movements of the stapes footplate. This study examines the rocking ratio in intact ears, and ears in which the incus has been removed and reconstructed with a Malleus Assembly to the Stapes Head (MASH) or Tympanic membrane Assembly to the Stapes Head (TASH) type of prosthesis. Results show that the RR increases with increasing frequency in the intact ear. They also show that the RR is higher than the intact ear in all frequencies for both MASH and TASH reconstructions. MASH reconstructions result in a higher RR than TASH type reconstructions.

No abstract received.

Pathological fixation of the stapes is a common cause of conductive hearing loss. Fixation of the malleus, though less common, is perhaps under diagnosed. Currently, pre-surgical differential diagnosis of the site of ossicular fixation is not definitive because the effects of fixations have not been well characterized. Here we report results from fresh human temporal bones in which we (1) measured the acoustic effects of controlled, simulated fixations of the stapes and malleus, and (2) determined how the changes in umbo velocity and stapes velocity differ between these fixation sites.

Methods: Umbo velocity (V_U) and stapes velocity (V_s) in response to ear-canal sound pressure were measured with a laser Doppler vibrometer. Simulated malleus fixations included fibrous and bony-bar fixation, as well as extensive bony fixation. Simulated stapes fixations included bony footplate fixation and extensive bony stapes fixation. These fixations were simulated using Jeltrate (for fibrous fixation), and dental cement or cyanoacrylate (for bony fixation).

Increased strength of fixation of the malleus head or the stapes results in decreased V_U and V_s magnitudes with extension to higher frequencies of the range in which the system is stiffness dominated. These changes are consistent with an increase in stiffness of the ossicular system. At low frequencies, malleus fixations produce similar reductions in V_U and V_s (approximately 5 dB for fibrous, 15 dB for cement bar, and 30 dB for extensive fixation). Stapes fixations produce small reductions in V_U and larger reductions in V_s (e.g. 3 dB in V_U and 25 dB in V_s for footplate fixation, and 7 dB in V_U and 35 dB in V_s for extensive stapes fixation). Direct comparison of the temporal bone measurements and live human measurements shows strong similarities. These results suggest that pre-surgical differential diagnosis of malleus and stapes fixation is possible with the combination of laser vibrometry at the umbo and audiometry.

Unrecognized partial fixation of the anterior malleal ligament (AML) has been proposed as one of the causes for the requirement of revision surgery after stapedectomy. We studied the effects of stiffening the AML on ossicular responses to sound stimulation in fresh temporal-bone preparations. We stiffened the AML by various methods and measured the effects on umbo velocity (V_U) and stapes velocity (V_s). We found that stiffening the AML, regardless of the method, resulted in only 0-6 dB reductions in ossicular mobility at low frequencies. When we replaced the AML with a very stiff cement bar (a bony-bar simulation), the effects were approximately 8 dB at low frequencies. However, when the malleus was fixed by a similar cement bar applied to the head of the malleus, the effect was between 15-30 dB. Because the AML and the posterior incudal ligament define the axis of rotation, our results are consistent with the physical principle that reducing the rotation of the ossicles by a stiffening force applied at the axis is less effective than the same force applied away from the axis. Furthermore, our results suggest that partial fixation of the malleus by a stiffened AML does not result in significant conductive hearing loss.

The effect on post-operative hearing results of different stapes piston diameters has been reported clinically and in analog circuit models. Generally, larger piston diameters produce better lower frequency post-operative hearing results. However the clinical data are confounded by the difficulties in interpreting results of non-randomized retrospective trials performed by different surgeons. Moreover, mathematical and circuit otosclerosis models are not accurate enough at this time to be reliable predictors of the clinical situation because of inadequate experimental data to validate the assumptions. We used a human temporal bone otosclerosis model to evaluate stapedotomy with pistons of different surface area. The model has the footplate cemented in the oval window with fast drying epoxy cement. The output measure for each pistons evaluation in this model is displacement of the round window membrane before and after piston insertion. The displacement measurement was made with a non-contacting laser Doppler vibrometer(LDV). The input was a constant sound pressure level at the tympanic membrane from 0.125 to 8kHz. In the present study, we evaluated three different size pistons. Two were 0.4mm and 0.8mm diameter commercially available stainless steel wire-Teflon pistons, the third piston was an experimental oval shaped large piston, which was piston whose area (1.3×0.8mm) was equivalent to a 1.05mm diameter round piston. For each piston, twelve temporal bones were studied. Comparison of the 0.4mm and 0.8mm diameter pistons showed slightly better sound transmission (3-8dB) with the larger piston at frequencies below 2kHz. The large experimental piston provided improved transmission from 0.5 to 4kHz, compared to the 0.4mm and 0.8mm diameter pistons. In further experiments, removing the head of the malleus plus sectioning the tensor tympani muscle tendon and removing the incus produced further increases in sound transmission.

Ossicular reconstruction with a prosthesis from the eardrum to the stapes is common. Although the interface between the eardrum and the prosthesis is what determines the delivery of mechanical energy to the prosthesis, and hence to the inner ear, this interface has not been well studied. This interface is often modified by the addition of a cartilage cover over the prosthesis to prevent extrusion, or by scar tissue ingrowth. This study examines the effect of interposing materials of 3 different rigidities in the interface between the prosthesis and eardrum. Effects on the elicited stapes footplate movements to acoustic stimulation are measured. The 3 materials are glass (rigid), cartilage (intermediate) and Merocel® (soft). When compared to the uncovered prosthesis and to each other, none of the materials had a significant effect on transmission of vibrations to the stapes at low frequencies. The Merocel® performed the worst at high frequencies. The rigidity of the material covering the prosthesis under the eardrum is not an important determinant of the mechanical transmission of vibrations from the eardrum to the prosthesis at low frequencies.

The effect of topical application of basic-fibroblast growth factor (b-FGF) on healing of tympanic membrane (TM) after canal wall up tympanoplasty was investigated. B-FGF (100 (µg/ml) was administered on a Gelfoam® pledget over the surface of the grafted fascia and TM. The epithelization over the grafted fascia and full drying of TM surface with b-FGF was completed within 18.3±1.6 days after the surgery, while it was after 36.3±2.5 days without b-FGF. The present study demonstrates that topical application of b-FGF does accelerate the TM healing without any apparent side effects. It is possible that b-FGF will be a powerful tool for the reconstruction of a moderate to large TM defect in canal wall up tympanoplasty.

A new method for closing tympanic membrane (TM) perforations using basic fibroblast growth factor (bFGF) combining with an atelocollagen/silicone bilayer membrane as a patch material was examined. BFGF was used to facilitate the growth of fibroblasts and collagen fibers at the margin of the perforation. Nine patients were treated with bFGF and five were treated with saline. The mean perforation size before treatment was 16.5% in the bFGF group and 9.6% in the control group. Closure of the TM perforation was achieved in all cases in the bFGF group, while only two of five cases in the control group closed. The healing time until complete closure was 3.7 weeks with the bFGF treatment. No complications related to the use of Pelnac or bFGF were noted.

The aim of this study is to compare the availability of the ossicular reconstruction using the autologous cartilage and ossicle. Postoperative hearing results of 84 ears (cartilage: 60 ears, ossicle: 24 ears) which underwent type III tympanoplasty for otitis media with cholesteatoma were analyzed. Postoperative air-bone gap at five frequencies was used for the assessment of hearing results. The rate of ears with a postoperative air-bone gap of less than 10 dB to all operative ears was examined. In ears with the cartilage columella, the rate at 250 Hz, 500 Hz, 1 kHz, 2 kHz and 4 kHz was 38%, 55%, 63%, 81%, 43%, respectively. In ears with the ossicle columella, the rate at 250Hz, 500Hz, 1 kHz, 2 kHz and 4 kHz was 38%, 54%, 67%, 71%, 33%, respectively. There are no significant difference at each frequency between the cartilage and ossicle although ears with the cartilage columella showed a tendency to have a better postoperative hearing at 2 kHz. The study showed no significant difference in the postoperative hearing at 250 Hz to 4 kHz between the ossicular reconstruction using the autologous cartilage and ossicle.

In 1992, we newly designed a cartilage connecting hydroxyapatite prosthesis with a spearhead. The concept of this new prosthesis is to avoid the extrusion and dislocation of hydroxyapatite prostheses. This new prosthesis has a spearhead on the top and the cartilage and prosthesis are connected to each other using this spearhead. In 1995, we established a database for the hearing results of all tympanoplasty cases. From this database we selected 302 cases who underwent tympanoplasty with the cartilage connecting hydroxyapatite prosthesis. When we cannot preserve the tendon of the tensor tympani muscle in a severely diseased middle ear, we use the cartilage connecting hydroxyapatite prosthesis. There are two types of prostheses. We select a partial type of prosthesis when stapes is present, and a total type when stapes is absent. We show the extrusion rate and hearing results. The postoperative hearing levels have remained stable throughout the 7 years observation period.

Superior semicircular canal dehiscence (SSCD) syndrome is primarily associated with vertigo and disequilibrium induced by loud sounds (Tullio’s phenomenon) and middle-ear pressure changes. SSCD syndrome may also cause increased bone-conduction sensitivity and decreased air-conduction sensitivity leading to an air-bone gap. The abnormalities in both air and bone sensitivities are typically greatest at frequencies below 2 kHz. Understanding the mechanisms that cause this air-bone gap may aid in the diagnosis of SSCD syndrome and in understanding the pathology that causes the symptoms. We examined the effects of SSCD on responses to bone-conduction stimuli in a chinchilla model by measuring the motion of the fluid within the dehiscence and the cochlear potential. In surgically induced dehiscences we found differential motion between the inner-ear fluid and the adjacent bone in response to bone-conduction stimuli for frequencies from 569 Hz - 2440 Hz. An increase in sensitivity to bone-conducted stimuli (as measured by cochlear potential) near 500 Hz of 8 dB was also found. The sensitivity to bone-conducted stimuli is dependent on the size of the dehiscence. Increased CP in chinchillas with surgically induced SSCD is consistent with lower bone-conduction thresholds in SSCD syndrome patients suggesting that bone-conduction hypersensitivity is an indicator of a SSCD.

New functional imaging tools, diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) were introduced to evaluate hearing loss resulting from various middle ear lesions. Compared to sensorineural hearing loss, The common finding of DTI measurements in conductive hearing loss cases was that the neural deficits were less likely found on auditory pathway regardless of the origins of conductive hearing loss. From fMRI study, cortical responses of conductive hearing loss patients were that the auditory cortex (primary and secondary), which is contralateral to normal ear, shows strong activation but the auditory cortex, which is contralateral to affected ear, is seldom activated. On the other hand, cortical activation patterns of sensorineural hearing loss patients revealed that primary auditory cortex did not response to sound stimulation. Instead, our preliminary results indicated the broad activation of secondary auditory cortex, which is adjacent to primary cortex. Our results suggest that DTI and fMRI techniques provide very useful functional informations of auditory pathway and auditory cortex, which were not available previously. Therefore, it is believed that these new techniques will make significant contribution on the understanding of middle ear disease such as otitis media.

We introduced diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) to evaluate functional changes of conductive hearing loss and profound sensorineural hearing loss patients. Cortical responses of conductive hearing loss patients were that the auditory cortex (primary and secondary), which is contralateral to normal ear, shows strong activation but the auditory cortex, which is contralateral to affected ear, is seldom activated. However, the cortical activation patterns of profound sensorineural hearing loss patients revealed that primary auditory cortex did not response to sound stimulation. Instead, our preliminary results indicated the broad activation of secondary auditory cortex, which is adjacent to primary cortex. DTI findings of conductive hearing loss patients showed that the neural deficits were less likely seen on auditory pathway. However, the DTI findings of profound sensorineural hearing loss patients revealed that the neural damages were more often seen on auditory pathway. In conclusion, DTI and fMRI technique seem to have a clinical importance in differential diagnosis of CNS for conductive and sensorineural hearing loss patients by providing functional informations of auditory pathway and auditory cortex, which were not available previously.

Conventional studies of the middle ear ossicles give relatively limited information on shape, mechanical strength and 3-dimensional relationship. Recently, micro-CT scanning technology has been applied to analysis of skeletal structure. This study aims to reconstruct the 3-dimensional structure of the ossicles, including the length, strength, and the angle. In this study, the structures of ossicles obtained from 3 cadavers were analyzed through micro-CT(SkyScan, Belgium) by filming the 2-dimensional cross section image running perpendicular to the long axis of the ossicles. The 3-dimensional images were thereby reconstructed for each, and were analyzed by using CT-Analyzer™ and Ant™. Based on the results, the strength, length, and angle of each ossicle were measured.

In this result, the ratio between the handle of the malleus (4.413mm) and the long process of the incus (3.559mm) was 1.24 : 1, which acts as a lever of middle ear impedance transformer. The volume fraction, indicating relative strengths of ossicles, was lower in the portion close to the articular surface.

Our preliminary data of ossicular structure analyzed by micro-CT scan will be helpful for elucidation of ossicle’s structure and further development of artificial prosthesis.

The aim of the present study is to examine the usefulness of multislice computed tomography (MSCT) using multiplanar reconstruction (MPR) in evaluating the ossicular chain of ears with middle ear diseases. MSCT and operative findings were compared in 53 ears of 52 patients whose diseases were cholesteatoma in 24 ears, chronic otitis media in 20 ears, conductive deafness including malformation in 9 ears. In more than 90% of ears with no soft tissue shadow, MPR image findings of the malleus handle, the incus long process, incudostapedial joint and the superstructure of the stapes were in accordance with their operative findings. The similarity rate in ears with soft tissue shadow around the ossicles was decreased by 10-20% in the ossicle parts except the malleus handle. The footplate of the stapes in 7 of 48 ears showed a “sclerosis” finding. Five ears had an “erosion” finding. There was no relationship between MPR image findings and the mobility of the footplate. The present results indicate that the MPR image provides accurate information on the malleus, the incus, the incudostapedial joint and the superstructure of the stapes although the presence of soft tissue shadows around the ossicles diminishes the accurancy, and that the MPR image can provide only limited information on the mobility of the footplate.

In this retrospective study, we analyzed improvements in hearing after stapes surgery, in which a Teflon wire piston was used, and we investigated how the size of the hole in the stapes footplate may affect surgical results. Between 1991 and 2001, 127 ears (98 patients) underwent stapes surgery with the use of a Teflon wire piston by the same experienced surgeon at Nagoya University Hospital and the Japanese Red Cross Nagoya First Hospital. Follow-up was at least 3 months in all cases. Of the 127 ears, 123 (96.9%) had postoperative air-conduction threshold improvements of better than 15 dB at speech frequencies; 119 (93.7%) improved within 15 dB or better between preoperative bone-conduction thresholds and postoperative air-conduction thresholds. However, only 76 ears (59.8%) recovered within 30 dB or better in postoperative air-conduction thresholds. As for the hole in the footplate, only a small hole, 0.8 mm in diameter, was made in the center of the footplate (stapedotomy, 82 cases). In 28 cases, half of the footplate was removed (partial stapedectomy), while in 12 cases it was removed totally (total stapedectomy). The preoperative air and bone-conduction gaps resulting from stapedotomy (STO), partial stapedectomy (PST), and total stapedectomy (TST) at speech frequencies were 35.1, 29.2, and 31.4 dB, respectively. The postoperative air and bone-conduction gaps of STO, PST, and TST were 8.2, 3.6, and 5 dB, respectively. The postoperative A-B gap of STO was significantly larger than that of PST. In addition, closure of the A-B gap after stapedotomy was poor at frequencies lower than 1 kHz. In contrast, the postoperative air-conduction gains of STO, PST, and TST at 8 kHz were 12.4, 6.1, and 1.4 dB, respectively. The postoperative air-conduction gain of STO was significantly larger than that of TST. We conclude that making a large hole in the footplate without total removal is necessary to improve postoperative hearing gain.

We review a series of 6 ears in 5 patients who were operated on for tympanosclerotic stapes fixation and followed up for more than 6 months. A successful hearing gain was achieved in 66.7 percent (4 ears) of cases one year after the surgery. The difference between preoperative and postoperative bone conduction levels at 0.5, 1 and 2 kHz were within 5 dB in all of six ears, though the bone conduction level at 4 kHz was off scale in one patient. These findings suggest that stapedectomy is when the middle ear space is aerated with no perforation of the tympanic membrane and remains stable for more than 1 year. There was marked improvement of hearing levels at 2 kHz.

Simple underlay myringoplasty (SUM) through the ear canal has been developed by Yuasa (1989) [1], which has lower risk of sensorineural hearing loss than conventional myringoplasty or tympanoplasty (CMT). We tried bilateral same day surgery using this technique and compared the present results with those of the previous report [2]. Of 200 cases with bilateral perforated chronic otitis media that we treated during 1999-2002, 17 cases underwent bilateral same day surgery. Bilateral SUMs was performed on 5 patients, and SUM/CMT on 12 patients. Closure of perforation was successful in 12 patients (70.6%) on both sides and in 5 patients (29.4%) on one side. Postoperative A-B gap of less than 20 dB was achieved in 15 cases (88.2%) on both side and in 2 patients (11.8%) on one side. These results are better than those of the previous report. Bilateral same day surgery for bilateral perforated chronic otitis media is possible if the operative indications are considered.

A case suffering from traumatic facial paralysis and surgically treated via combined transmastoid and trans middle cranial fossa (MCF) routes was reported. A 21 year-old man fell onto a concrete floor 16 days before consultation. Left facial paralysis, rated 8/40, was noted after the injury. His left ear was found to be deaf while caloric test revealed symmetric reaction between the ears. High resolution computed tomography indicated that the injured portions of the facial nerve were the labyrinthine, perigeniculate, horizontal, and pyramidal portions. We performed combined transmastoid and trans middle cranial fossa approach for decompression of the nerve 25 days after the injury, and the patient showed an excellent recovery of facial nerve function although minimum degree of synkinesis appeared. Selection for surgical intervention in the management of facial nerve paralysis due to temporal bone fracture depends upon degree of nerve injury, and surgical approach is chosen based on sites of nerve injuries and associated damages including ossicles and otic capsule.

No abstract received.

Restoring better middle ear aeration is required to prevent recurrence of middle ear cholesteatoma. For treatment of middle ear cholesteatoma, we have adopted canal wall down tympanoplasty with canal reconstruction. The primary objective of our study is to evaluate the effectiveness of this method for restoring good middle ear aeration using CT scans before the second-stage operation. In 37 patients with middle ear cholesteatoma treated by staged surgery, we analysed coronal CT scans before the second operation. The restoration of middle ear aeration is classified into groups of grades 0-3 (grade 0: no aeration in middle ear, grade 1: aeration in mesotympanum and hypotympanum, grade 2: aeration in meso and hypo-tympanum and attic, grade 3: aeration in tympanic cavity and antrum). Before the second-stage operation, no group 0 cases, nine group 1 cases, and 28 (75.7%) group 2 and 3 cases were observed. It is our belief that recurrence of middle ear cholesteatoma rarely occurs in cases of grade 2 or grade 3. We therefore confirmed that the method we have adopted is useful for preventing recurrence of middle ear cholesteatoma. We examined the correlation between characteristics of operative findings at the first operation and degrees of aeration. In children, restoration of middle ear aeration before the second-stage operation was better than that in adults. In cases in which the extended area of cholesteatoma is within the attic or aditus, degree of aeration before the second-stage operation was good. In cases in which there is aeration of mastoid cells (peripheral site of cholesteatoma) at the first-stage operation, degree of aeration before the second-stage operation was good. In cases in which the membrane of mesotympanum and hypotympanum was inflammatory and granular, restoration of middle ear aeration before the second-stage operation was poor. In the 14 most difficult cases in which there was no aeration in the mastoid cells (peripheral site of cholesteatoma) with severe change in the meso and hypo-tympanum membrane, the percentage of grade 1 cases was 42.9%. For such cases, improvement of operative procedures (for example, local steroid administration) is necessary.

No abstract received.

The Laser Doppler Interferometer (LDI) is a device which allows contact-free measurements of vibration with a high degree of accuracy. Its potential for analysis of the tympanic membrane and the ossicles has been documented. Although LDI has been widely used in the research of middle ear mechanics, it was not yet introduced as an adjunctive test for otological work-up. Preoperative analysis of manubrium vibration allows evaluating the mobility and the integrity of the ossicular chain with high sensitivity. Thereby it is possible to differentiate middle ear pathologies and better prepare the patient and the surgeon for an intervention. Intraoperative and postoperative LDI could allow quality assurance and may facilitate evaluation of prosthesis placement and fixation or identify the reasons for unexpected failures after surgery. Thereby the LDI may assist in improving hearing results after otosurgery. Possible pre-, intra- and postoperative applications are illustrated on the basis of case presentations and their clinical value is discussed.

It has been desired for checking of the stapes footplate mobility in tympanoplasty and surgery of middle ear implant by surgeons. In this study, an ossicular vibration tester to detect small mechanical impedance such as a stapes footplate is presented. The probe of this tester is constituted by a vibrator and a force sensor built in the vibrator. The vibrator force into vibrating at the resonance frequency, thus the mechanical output impedance of the vibrator is reduced to an extremely small value. Therefore, if the vibrator tip touches a stapes, the motion of the vibrator will be significantly affected. This change of the vibration may be detected from the output of the force sensor. Actually, evaluating the stapes footplate mobility by using the tester in the surgery for both patients having a normal stapes footplate and having a otosclerosis, the tester has found to be useful.

We developed an ossicular vibration tester for evaluation of the ossicular mobility. The device consists of three components: a probe to be attached to the ossicle, a vibrator to activate the probe shaft, and a sensor to detect vibration of the probe. The vibrator is activated with an electric signal at around 2000 Hz, which is supposed to be a resonant frequency of human ossicular chain. These components are encased in a hand-holder for easy manipulation during surgery and are controlled by a computer. Using this device, we measured the ossicular mobility during ear surgery. The results were evaluated by calculating the percentage of resistance in comparison with that of reference. This paper reports the design, principles and measuring procedures of our device, and shows preliminary results of 4 patients.

Confirmation of the conditions of the ossicles is essential for tympanoplasty. Although several methods to measure ossicular mobility have been reported, the quantitative evaluation of ossicular mobility has been difficult to date. We have therefore developed a new system with which it is possible to quantitatively evaluate ossicular mobility during surgery. The apparatus enables us to simultaneously obtain the reaction force from the ossicles and its displacement. Force-displacement curves obtained from otosclerotic ears were clearly different from these obtained from normal subjects. Furthermore, pre- and post-treatment results showed significant differences. With this new apparatus, it is possible to distinguish the differences in mobility of the ossicles between normal and fixed ossicles, as well as estimate the change of the mobility between pre- and post-treatment for ossicular fixation.

Pure tone audiometry, multifrequency tympanometry, audiometric Bing testing, and magnetic resonance imaging (MRI) were performed in patients with large vestibular aqueduct (LVA) syndrome. The air–bone gap always existed. In the Bing test, the threshold of bone conduction did not change significantly upon occlusion of the external auditory meatus. There was a tendency for the resonant frequency to decrease as the volume of the endolymphatic duct and sac increased. The cause of the air–bone gap is discussed using the ‘three windows’ model.

No abstract received.

Although the sound or the pressure change in the pharyngeal space can be transmitted to the middle ear cavity with a low level of attenuation in patients with patulous Eustachian tube, it is sometimes hard to assess the severity of the patulous condition objectively. Recently, we have attempted to assess the acoustic transfer function of the Eustachian tube using audiometric measurement. In the present paper, preliminary results are reported.

The detection thresholds for the tones presented in the nasal cavity were measured in subjects with patulous symptoms. The measurements were conducted before and after treatment for obstruction of the patulous tube (insufflation of Lugol’s solution). In typical cases, the detection thresholds for the tones presented in the nasal cavity were up to about 30 dB lower (often dominant in the low frequency region) in the patulous condition when compared with those obtained after treatment.

The threshold differences between pre- and post-treatment may reflect the degree of greater acoustic patency in patients with a patulous tube. The present method may be another easy objective test to assess the condition of patulous Eustachian tube.

The middle ear should be the ideal position for an implantable microphone, just as nature had conceived it for optimal sound gathering and conduction. We therefore developed two concepts, using a piezoelectric transducer, which is connected to the vibrating ossicular chain. The first concept works via a hydroacoustic transmission with a liquid filled balloon tip, contacting the incus body. The second concept uses a titanium-housed piezo crystal, with contact to the joint surface of the lenticular process. Here the maximal sound pressure is generated due to the hydraulic amplification of the middle ear. Furthermore, ambient air pressure variations, with their excessive displacements of the tympanic membrane are significantly reduced at this location due to the gliding process in the malleus-incus joint. This results in a pure acoustical stimulation and avoids serious loads to the microphone as induced by the atmospheric pressure changes. Our results from temporal bone experiments confirm the function of these principles with a sensitivity comparable to conventional electret microphones. Biology and technology are combined to a true biotechnical implant for an implantable microphone.

Research and development over the past two decades has shown that implantable hearing aids can circumvent some of the problems found in conventional hearing aids, such as feedback, cosmetic problems and so on. However, these hearing aids have not as yet been widely used, because invasive surgery has to be performed to implant them and applying them in children, who are still growing, is difficult.

In this study, a prototype of the non-implantable electromagnetic hearing aid, which can generate a high-excitation force to vibrate the ossicles via the tympanic membrane, was constructed. The hearing aid consists of an electromagnetic transducer and an amplifier. To determine fundamental properties of the hearing aid, excitation force and acoustical gain were evaluated using an artificial middle ear and a human temporal bone, respectively. The experiments showed that the hearing aid was able to generate the maximum excitation force, which is equivalent to a sound pressure of 100 dB SPL at high frequencies.

A middle ear implant (MEI) system that use the differential electromagnetic transducer (DET) was implemented using micro electro mechanical system (MEMS) technology. The DET is designed to have good vibration efficiency and structure that isn’t interfered by external environmental magnetic field. In order to preserve the uniform vibration performance, the MEMS technology was introduced to manufacturing the elastic membrane using polyimide that is tenderer than silicon. Using the finite element method (FEM), vibration characteristics are simulated and designed that the resonance frequency of the membrane is closed to that of human ear. The results of vibration experiments showed distinguished performance of the DET. We implemented the MEI system using a DET and implanted it to a dog, which showed the MEI system had excellent performance and work in a living body.

Laser Doppler vibrometry was used to measure the movements of the ossicles driven by the transducer of the MET™ Ossicular Stimulator in two fresh temporal bones. In addition, probe microphone recordings in the ear canal and measurement of the electrical impedance of the transducer were made at different loading positions.

Optimal transfer of vibrational energy occurred between the initial point of contact between transducer tip and bottom of the laser hole with the incus, and ca. 250µm further down.

During transducer positioning, both ear canal sound pressure level and MET electrical impedance could be used as an indicator for initial contact between the MET transducer and the incus.

Both ear canal probe microphone measurements and transducer electrical impedance can be used to find optimal coupling of the MET Ossicular Stimulator to the ossicular chain. Probe microphone measurements have been successfully used with the current generation semi-implantable device; impedance measurement will be available in the upcoming fully implantable device.

Surgeons and candidates need to be well aware of advantages of implantable middle ear hearing aids (IHA) regarding the sound quality and the word recognition under noises for popularization of the devices.

In this study, the vibration of the stapes footplate (FP) of human temporal bones was measured by using a LASER Doppler vibrometer. Using these measurement data, the impulse responses for displacement on FP responding to electrical inputs to both a vibrator for IHA and an insert earphone for conventional hearing aids (CHA) were calculated. Monosyllabic word recognition tests were conducted for subjects with normal hearing to compare these impulse responses. In these tests, word lists mixed with a multi-talker noise were processed by convolution with the impulse responses and presented.

The result showed that IHA was superior to CHA for word recognition.

In conclusion, this method is helpful to clearly present advantages of IHA because it may simulate responses of both IHA and CHA for any sound sources.

Purpose: Conventional tympanoplasty sometimes fails in patients with adhesive otitis media or acquired stenosis of the external auditory canal, because these diseases tend to recur after surgery and re-operation is sometimes required. When the vibrator of the partially implantable hearing device (RION CO. LTD., E-type) is connected to the stapes, sound vibration is directly transmitted to the inner ear. Therefore, it is not necessary to reconstruct the eardrum in its original position. This study evaluated whether surgery using a partially implantable hearing device, in combination with lateralization of the eardrum, is effective in such cases. Materials and Methods: The eardrum of three patients with bilateral adhesive otitis media and that of one patient with bilateral acquired stenosis of the external auditory canal was intentionally lateralized to a distance of within 1cm from the orifice of the external auditory canal. The hearing device was implanted and the tip of the vibrator was connected to the head or footplate of the stapes in combination with hydroxyapatite tube or a columella. Results: Two to five years later, the depth of the eardrum in four patients was between 2.0 and 2.7cm, and no re-adhesion of the eardrum and no re-stenosis of the external auditory canal were observed. Although these patients showed moderate to severe mixed hearing loss between 50 and 82dB pre-operatively, postimplantation hearing threshold levels afforded by the implanted hearing device were between 18.8 and 41.3 dB. These four patients wore air conduction hearing aids preoperatively and suffered from frequent otorrhea. Postoperatively, they were very satisfied with no otorrhea, no earphone, better hearing, better sound quality, and less noise, etc. Conclusions: From these results, it was concluded that surgery using a partially implantable hearing device, in combination with lateralization of the eardrum, is effective for such patients.

The fact that a vibration of the skull causes a hearing sensation has been known since the 19^th century. This mode of hearing was termed hearing by bone conduction (BC) or BC sound. Although more than a century of research on hearing by BC, its physiology is not completely understood. Recently, the field of BC physiology has gained interest due to the use of the Bone Anchored Hearing Aid (BAHA^®) and the use of BC transmission for communication in noisy environments, where BC transmission offers potential advantages for picking up the sound as well as receiving the sound. The theory identifies several contributing factors to BC hearing of which five are presented here: 1. sound radiated into the external ear canal, 2. middle ear ossicle inertia, 3. inertia of the cochlear fluids, 4. compression of the cochlear walls, and 5. pressure transmission from the cerebrospinal fluid. Of these five, inertia of the cochlear fluid seems to be the most important.

It is also suggested from tone cancellation and model experiments that the stimulation mode of the basilar membrane is identical for air conduction (AC) and BC, i.e. the hydrodynamics in the cochlea always sets up a traveling wave on the basilar membrane in the basal part wherever the stimulation is. However, these theories can sometimes not fully explain clinical BC results. The pressure distribution in the cochlear fluids is very different for BC and AC stimulation; a spatial pressure generation for BC is set up. Inertial effects of the osseous spiral lamina and organ of corti may give stimulation directly on the basilar membrane not considered by classical BC theories.

The transmission of the vibrations in the skull influences the hearing by BC. The stimulation position, resonances and anti-resonances of the skull together with attenuation of vibrations in the skull, result in unequal stimulation of the cochleae and lateralization of the BC sound. Even if BC sound is believed to reflect the true cochlear function, external lesions such as middle ear diseases affect the BC sensitivity. However, a middle ear lesion affects BC sensitivity considerably less than it does AC sensitivity. The BC route can also be used for hearing aids; since the BC route is less efficient than the AC route, BC hearing aids are mainly used with hearing losses where AC hearing aids are contraindicated. Of the BC hearing aids, the Bone Anchored Hearing Aid shows the best result Lately it has been shown that, even if BC sound from one stimulation position is transmitted to both cochleae, a bilateral fitting of BAHAs is beneficial for the patient. Further, BAHA^® is also being used to aid persons with severe unilateral hearing loss or single sided deafness.

Benefit of binaural hearing was evaluated in cochlear implant (CI) users who wore hearing aids (HA) on the opposite ear. Subjects were 3 males and 3 females whose age ranged from 48 to 84 y.o. All of them have used CI and HA for more than six months. Their speech perception was examined in quiet using monosyllable and Japanese-HINT (J-HINT) sentences. J-HINT test in quiet was developed for evaluating speech reception threshold (RTS) of 50 % correct response. In J-HINT under the noise condition, speech sound was given from the front at a constant intensity of 65 dB, while the noise of various intensities was given from the front, right or left. The signal to noise ratio (S/N in dB) was measured when the subject made 50% correct response to speech sounds. Three subjects showed significantly better result in binaural hearing than mono-aural (CI-alone) hearing for monosyllable and HINT sentence (paired t-test, p<0.05). Subjects of better speech reception had a longer time of HA use than poor performance subjects (18.3 vs 4.0 years). Under the noise conditions the binaural hearing showed better performance (i.e. smaller S/N ratio) than mono-aural hearing. The best performance was obtained when the noise came from HA side. Although the hearing with HA alone showed marginal benefit in our CI users, binaural hearing with CI and HA resulted better performance in speech perception under both quiet and noisy circumstances.

The Project on HighQualityLowCostHearingAid is in close relationship with the activity of Hearing International, NGO organized in 1992, working exclusively for prevention and management of hearing impairment and deafness in the world. Hearing-aid is recently very much advanced but is extremely expensive. Because it is now sophisticated, its use would require a lot of efforts in fitting and in follow-ups. The hearing impaired and the deaf have a lot of difficulties, which are invisible and then not understandable for most hearing people. Efforts are requested to make the hearing people understand and support them.

No abstract received.

No abstract received.

We renovated surgical procedures of type 1 tympanoplasty and performing these procedures from September 1999. The purposes of the renovations are for the better postoperative hearing, the shorter period of healing and the shorter days of hospital treatment. The renovated points are as follows. Enlargement of facial recess approach e.g., the buttress is removed to visualize the tympanic cavity as much as we can. Neither the posterior meatal skin nor annulus is elevated to prevent a postoperative swollen of the meatal skin and keep the original position of the tympanic membrane. The repair of perforation of the tympanic membrane is performed via the external auditory canal using underlay method. Our criteria of performing these procedures are as follows. The subjects are patients with simple chronic otitis media. The ossicular chain exists. The condition of otitis media e.g. proliferation of granulation, is independent. As exception, type 3 tympanoplasty will be chosen when there is no malleus handle.

Twenty-six patients with simple chronic otitis media underwent this renovated type 1 tympanoplasty. Postoperative hearing was evaluated according to the criteria proposed by Otological Society of Japan. The hearing result was considered as successful when the postoperative hearing level satisfied with at least one of three conditions as follows: 1) air-bone gap less than 15dB, 2) hearing gain more than 15dB, or 3) hearing level above 30dB. Success rate was 96.2%. The average of postoperative air-bone gap, hearing gain and hearing level were 2.5dB, 11.6dB and 26.2dB, respectively. These results indicate that our renovation of the tympanoplasty is useful for the better postoperative hearing results.

The concept that closing failure of Eustachian tube and habitual sniffing were closely related to pathogenesis of middle ear diseases, such as secretary otitis media, atelectatic ears and cholesteatoma [1–8] . We previously reported that 69.7% of the bilateral cholesteatoma have habitual sniffing and 63.3% had positive sniff test [9] . In this study, we compared the clinical findings of unilateral cholesteatoma with special reference to habitual sniffing. Subjects and methods: One hundred and two fresh cases of unilateral cholesteatoma, which were operated on at Hyogo College of Medicine, were examined. Responses to a detailed questionnaire were obtained from patients concerning about the habit of sniffing to relive the symptoms such as auralfullness, autophonia or hyperacusis. To evaluate the effect of habitual sniffing, we measured the negative the negative middle ear pressure at the time of sniffing by using TTAG (tubo-tympano aerodynamic graphy), and compared the positive percentage of the sniff test of unilateral cholesteatoma and normal controls. We also examined the contralateral ear under the microscope. Results: Habitual sniffing was found 38 ears (37.3%) and devided patients into habitual sniffing group and non-habitual sniffing group. Normal ear drum was 44.7%, pocket formation was 39.5%, adhesion of the ear drum was 7.9% and retraction of the ear drum was 5.3% in habitual sniffing group. In contrast, normal ear drum was 90.8%, pocket formation was 3.1%, adhesion was 3.1% and chronic otitis media was 9.3% in non-habitual sniffing group. The incidence of positive sniff test in unilateral cholesteatoma (8/26, 30.1%) was higher than normal control (3/20, 15%). Conclusion: In habitual sniffing group, abnomality of the contralateral ear was statistically higher in habitual sniffing group than in non-habitual sniffing group. Habitual sniffing supposed play some role to the pathogenesis of cholesteatoma and contralateral ear disease.

No abstract received.

Experimental myringoplasty with collagen sponge, Terudermis^®, was performed to investigate the usefulness of Terudermis^® as a material for tympanic surgery. Under xylazine (16 mg/kg, i.p.)-ketamine (16 mg/kg, i.p.) anesthesia, artificial perforation was made in the guinea pig tympanic membrane followed by closure with saline-soaked Terudermis^®. Changes of the tympanic membrane were observed under a rigid telescope. Histopathological examination was investigated at 3, 7 and 14 days after operation. All perforation healed within 2 weeks. In some animals the Terudermis^® inserted disappeared within 2 weeks. At 7 days after operation, histopathological examination revealed that tympanic membrane extended to outer and inner sides of the inserted Terudermis^®. Terudermis^® may work as a scaffold for the extension of remained tympanic membrane, and may be an appropriate candidate for the closure of the tympanic membrane perforation.

Eustachian tube dysfunctions of patulous eustachian tube frequently cause full sensation of the ear, own breathing heard and/or autophony. However, detailed mechanism of the symptoms is still unknown and little treatment is used for this condition. We develop a new treatment with use of adhesive tape of Steri-Strip, putting it on the eardrum. Ear fullness improved immediately in 86%, own breathing heard in 44% and autophony in 33% of the patients. Long-term relief was achieved in 36 (63%) patients after repeated treatments, but symptoms recurred in 11 (37%) patients whenever the tape peeled off. Our new treatment is effective mostly patients with mild and moderate condition.