Association Between the Air-Bone Gap and Vibration of the Tympanic Membrane After Myringoplasty.

Air-bone gap (ABG) is an important indicator of hearing status after myringoplasty. A number of factors have been associated with ABG, but some patients still have ABG without identifiable cause. This study aimed to evaluate the relationship between tympanic membrane (TM) vibration using laser Doppler vibrometry (LDV) and ABG after myringoplasty. Between January 2013 and January 2015, 24 patients with ABG of unknown cause after myringoplasty were enrolled at the Beijing Tongren Hospital. Thirty normal controls were recruited from the hospital staff. All patients underwent primary overlay myringoplasty. Pre- and postoperative air conduction (AC) and bone-conduction (BC) thresholds, and ABG were measured. Umbo velocity transfer function (UVTF) for vibration of TM was measured with LDV. Air conduction thresholds were significantly reduced after myringoplasty (all P < .05), while BC thresholds were not significantly changed (all P > .05). ABG was significantly reduced after myringoplasty (all P < .05). Air-bone gap was correlated with UVTF at 1.0 kHz (r = -0.46; P = .024). For patients with UVTF >0.08 mm/s/Pa, ABG was correlated with UVTF (r = -0.56; P = .029). For post-myringoplasty ABG without readily observable causes, there was a significant relationship between ABG and TM vibration. These results provide new insights in the understanding of this relationship and may help explain ABG after myringoplasty when there are no clear contributing factors.

A bench-top model of middle ear effusion diagnosed with optical tympanometry.

OBJECTIVES: To assess the validity of a bench-top model of an optical tympanometry device to diagnose in vitro model of middle ear effusion (MEE). METHODS AND MATERIALS: We illuminated an in vitro model of ear canal and tympanic membrane with broadband light and relayed remitted light to a spectrometer system. We then used our proprietary algorithm to extract spectral features that, together with our logistic regression classifiers, led us to calculate a set of simplified indices related to different middle ear states. Our model included a glass vial covered with a porcine submucosa (representing the tympanic membrane) and filled with air, water, or milk solution (representing different MEE), and a set of cover-glass slips filled with either blood (representing erythema) or cerumen. By interchanging fluid types and cover-glass slips, we made measurements on combinations corresponding to normal healthy ear and purulent or serous MEE. RESULTS: Each simulated condition had a distinct spectral profile, which was then employed by our algorithm to discriminate clean and cerumen-covered purulent and serous MEE. Two logistic purulent and serous MEE classifiers correctly classified all in vitro middle ear states with 100% accuracy assessed by leave-one-out and k-fold cross validation. CONCLUSIONS: This proof-of-concept in vitro study addressed an unmet need by introducing a device that easily and accurately can assess middle ear effusion. Future in vivo studies aimed at collecting data from clinical settings are warranted to further elucidate the validity of the technology in diagnosing pediatric acute otitis media.

Endoscopic Assessment of the Isthmus Tympanicum and Tensor Tympani Fold and their Relationship with Mastoid Pneumatization in Chronic Otitis Media.

OBJECTIVES: To endoscopically evaluate the patency of the isthmus tympanicum and integrity of the tensor tympani fold as routes of ventilation of the attic and mastoid in chronic otitis media (COM) and to assess their effects on mastoid pneumatization. MATERIALS AND METHODS: Sixty patients with COM were categorized into two groups: (1) Group A: 36 patients with tympanic membrane perforation (2) Group B: 24 patients with limited attic disease of whom 14 patients had attic retraction pockets and 10 with limited attic cholesteatoma. A multislice computed tomography scan of the temporal bone was performed for each patient to assess the degree of mastoid pneumatization. Notably, either myringoplasty or tympanomastoid surgery was performed in all patients. An endoscope was inserted into the middle ear for evaluation of the isthmus tympanicum and tensor fold area. RESULTS: The isthmus tympanicum was patent in most ears (83.3%) of group A, whereas it was blocked in most ears (83.3%) of group B. The tensor fold was complete in 77.8% of ears in group A and 83.3% of ears in group B. It was observed that 94.1% of ears with patent isthmus in both groups had normal mastoid pneumatization and 5.9% of ears had poorly pneumatized mastoid. By contrast, 7.7% of ears with blocked isthmus tympanicum had normal mastoid pneumatization and 92.3% had poor mastoid pneumatization. Normal mastoid pneumatization was observed in 50% of ears in both groups with complete tensor fold, and 83.3% of ears with an incomplete tensor fold. CONCLUSION: A significant correlation was observed between COM with limited attic disease and obstruction of the isthmus tympanicum. Obstruction of isthmus tympanicum was associated with poor mastoid pneumatization. Furthermore, an incomplete tensor fold was associated with well pneumatized mastoid.

Physiological Basis of Noise-Induced Hearing Loss in a Tympanal Ear.

Acoustic overexposure, such as listening to loud music too often, results in noise-induced hearing loss. The pathologies of this prevalent sensory disorder begin within the ear at synapses of the primary auditory receptors, their postsynaptic partners and their supporting cells. The extent of noise-induced damage, however, is determined by overstimulation of primary auditory receptors, upstream of where the pathologies manifest. A systematic characterization of the electrophysiological function of the upstream primary auditory receptors is warranted to understand how noise exposure impacts on downstream targets, where the pathologies of hearing loss begin. Here, we used the experimentally-accessible locust ear (male, Schistocerca gregaria) to characterize a decrease in the auditory receptor's ability to respond to sound after noise exposure. Surprisingly, after noise exposure, the electrophysiological properties of the auditory receptors remain unchanged, despite a decrease in the ability to transduce sound. This auditory deficit stems from changes in a specialized receptor lymph that bathes the auditory receptors, revealing striking parallels with the mammalian auditory system.SIGNIFICANCE STATEMENT Noise exposure is the largest preventable cause of hearing loss. It is the auditory receptors that bear the initial brunt of excessive acoustic stimulation, because they must convert excessive sound-induced movements into electrical signals, but remain functional afterward. Here we use the accessible ear of an invertebrate to, for the first time in any animal, characterize changes in auditory receptors after noise overexposure. We find that their decreased ability to transduce sound into electrical signals is, most probably, due to changes in supporting (scolopale) cells that maintain the ionic composition of the ear. An emerging doctrine in hearing research is that vertebrate primary auditory receptors are surprisingly robust, something that we show rings true for invertebrate ears too.

[Clinical analysis of missed diagnostic congenital cholesteatoma].

Objective:The clinical symptoms, imaging features and surgical treatment of congenital cholesteatoma are reported. Method:The clinical data of 20 patients with congenital cholesteatoma diagnosed and treated in our hospital from January 2016 to May 2018 were retrospectively analyzed, including the age of onset, clinical symptoms, signs, audiology, HRCT of temporal bone, surgical methods and so on. Result:In 20 patients with congenital cholesteatoma, the clinical manifestations were hearing loss in the affected ears, including 5 cases with ear fullness and 4 cases with tinnitus. There were 13 cases of local yellow-white shadow of tympanic membrane, 5 cases of normal tympanic membrane and 2 cases of tympanic membrane bombe. Pure tone audiometry showed conductive deafness in 14 cases and mixed deafness in 6 cases. CT scan of temporal bone showed that 15 cases had pneumatic type of mastoid, 4 cases had diploectic type and 1 case had sclerostic type. There were 15 cases of interspersed flocculent shadow and 5 cases of mass shadow. Among the 20 cases of chronic otitis media with cholesteatoma, 6 have cholesteatoma in epitympanum, 4 in tympanic cavity, 3 in tympanic cavity and epitympanum, 2 in mastoid and tympanic antrum, 1 in mastoid, tympanic antrum and tympanic cavity, 1 in tympanic antrum, tympanic cavity and petrous apex, 1 in tympanic cavity, hypotympanum, posterior tympanum and ostium tympanicum tubae auditivae, 1 in aditus ad antrum, epitympanum and posterior tympanum, 1 in tympanic cavity, epitympanum and posterior tympanum. Intact canal wall mastoidectomy and tympanoplasty were performed in 7 cases, open mastoidectomy and tympanoplasty in 5 cases, middle ear exploration and tympanoplasty in 4 cases, atticotomy with reconstruction and tympanoplasty in 3 cases and subtotal temporal bone resection in 1 case. Conclusion:For patients with intact tympanic membrane presenting with hearing loss, the tympanic membranes should be carefully examined, and thin-section CT and MRI of temporal bone should be performed in time to avoid missed diagnosis of congenital cholesteatoma. Once diagnosed, surgery should be performed as soon as possible.

The Development of a Tympanic Membrane Model and Probabilistic Dose-Response Risk Assessment of Rupture Because of Blast.

INTRODUCTION: There is no dose-response model available for the assessment of the risk of tympanic membrane rupture (TMR), commonly known as eardrum rupture, from exposures to blast from nonlethal flashbangs, which can occur concurrently with temporary threshold shift. Therefore, the objective of this work was to develop a fast-running, lumped parameter model of the tympanic membrane (TM) with probabilistic dose-dependent prediction of injury risk. MATERIALS AND METHODS: The lumped parameter model was first benchmarked with a finite element model of the middle ear. To develop the dose-response curves, TMR data from a historic cadaver study were utilized. From these data, the binary probability response was constructed and logistic regression was applied to generate the respective dose-response curves at moderate and severe eardrum rupture severity. RESULTS: Hosmer-Lemeshow statistical and receiver operation characteristic analyses showed that maximum stored TM energy was the overall best dose metric or injury correlate when compared with total work and peak TM pressure. CONCLUSIONS: Dose-response curves are needed for probabilistic risk assessments of unintended effects like TMR. For increased functionality, the lumped parameter model was packaged as a software library that predicts eardrum rupture for a given blast loading condition.

Hearing Damage Induced by Blast Overpressure at Mild TBI Level in a Chinchilla Model.

INTRODUCTION: The peripheral auditory system and various structures within the central auditory system are vulnerable to blast injuries, and even blast overpressure is at relatively mild traumatic brain injury (TBI) level. However, the extent of hearing loss in relation to blast number and time course of post-blast is not well understood. This study reports the progressive hearing damage measured in chinchillas after multiple blast exposures at mild TBI levels (103-138 kPa or 15-20 psi). MATERIALS AND METHODS: Sixteen animals (two controls) were exposed to two blasts and three blasts, respectively, in two groups with both ears plugged with foam earplugs to prevent the eardrum from rupturing. Auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) were measured in pre- and post-blasts. Immunohistochemical study of chinchilla brains were performed at the end of experiment. RESULTS: Results show that the ABR threshold and DPOAE level shifts in 2-blast animals were recovered after 7 days. In 3-blast animals, the ABR and DPOAE shifts remained at 26 and 23 dB, respectively after 14 days. Variation of auditory cortex damage between 2-blast and 3-blast was also observed in immunofluorescence images. CONCLUSIONS: This study demonstrates that the number of blasts causing mild TBI critically affects hearing damage.

Eustachian tube dysfunction in children with cleft palate: A tympanometric time-to-event analysis.

OBJECTIVES: To characterize the duration of Eustachian tube dysfunction in children with cleft palate compared to those without cleft palate by performing time-to-event analysis on tympanometric data. To determine predictive characteristics of earlier achievement of normal tympanograms in children with cleft palate. METHODS: Longitudinal tympanometric data from a minimum of 10 years at a single center were reviewed for children with cleft palate born in the years 2003 through 2007. Children with cleft lip without cleft palate born in the same years were used as a reference group to compare children with similar length of follow-up. The association between time to sustained normal (type A) tympanograms with patient demographics, clinical characteristics, and otologic history was evaluated using time-to-event analysis and compared with log rank tests. Adjusted and unadjusted hazard ratios were estimated using Cox proportional hazard models. RESULTS: The median age of achieving a type A tympanogram in children with cleft palate was 9.9 years for one and 12.1 years for both ears, compared to 7.1 and 7.4 years in children with cleft lip only (P < 0.0001). On multivariate analysis, clinical characteristics such as the severity of palatal clefting or the presence of a cleft-associated syndrome/sequence were not predictors of a longer time to a type A tympanogram. CONCLUSION: Our results help characterize the observation that there is delayed time to normal Eustachian tube function in children with cleft palate, which is not associated with the degree of palatal clefting. LEVEL OF EVIDENCE: 3b Laryngoscope, 130:1044-1050, 2020.

Recovery from tympanic membrane perforation: Effects on membrane thickness, auditory thresholds, and middle ear transmission.

Sounds delivered to the ear move the tympanic membrane (TM), which drives the middle-ear (ME) ossicles and transfers the acoustic energy to the cochlea. Perforations of the TM result in hearing loss because of less efficient sound conduction through the ME. The patterns of TM motions, and thus ME sound transmission, vary with frequency and depend on many factors, including the TM thickness. In this study, we measured TM thickness, auditory brainstem responses (ABR), and ME transmission immediately following a controlled pars tensa perforation and after 4 weeks of spontaneous recovery in a gerbil model. It is found that after recovery, the hearing thresholds showed a sloping pattern across frequencies: almost back to normal levels at frequencies between 2 and 8 kHz, sloping loss in the low (<2 kHz) and mid-frequency (8-30 kHz) range, and little restoration at frequencies above 30 kHz. This pattern was confirmed by the measured ME pressure gains. The thickness of the healed TM did not return to normal but was 2-3 times thicker over a significant portion of the membrane. The increased thickness was not limited to the perforated area but expanded into intact regions adjacent to the perforation, which led to an increased thickness in general. Combined, these results suggest that TM thickness is an important factor in determining its vibration patterns and efficiency to transfer sounds to the ossicles and thus influencing ME sound transmission, especially for high-frequency sounds. The results provided both structural and functional observations to explain the conductive hearing loss seen in patients with abnormal TMs, e.g., caused by otitis media, spontaneously healed post-perforation, or repaired via tympanoplasty in the clinic.

Repair of subtotal tympanic membrane perforations: A temporal bone study of several tympanoplasty materials.

The aim of this project was to investigate the effects of different types of graft material, and different remaining segments of the native TM on its motion. In twelve human temporal bones, controlled TM perforations were made to simulate three different conditions. (1) Central perforation leaving both annular and umbo rims of native TM. (2) Central perforation leaving only a malleal rim of native TM. (3) Central perforation leaving only an annular rim of native TM. Five different graft materials (1) perichondrium (2) silastic (3) thin cartilage (4) thick cartilage (5) Lotriderm® cream were used to reconstruct each perforation condition. Umbo and stapes vibrations to acoustic stimuli from 250 to 6349 Hz were measured using a scanning laser Doppler vibrometer. Results showed that at low frequencies: in the Two Rims condition, all grafting materials except thick cartilage and Lotriderm cream showed no significant difference in umbo velocity from the Normal TM, while only Lotriderm cream showed a significant decrease in stapes velocity; in the Malleal Rim condition, all materials showed a significant decrease in both umbo and stapes velocities; in the Annular Rim condition, all grafting materials except Lotriderm and perichondrium showed no significant difference from the Normal TM in stapes velocity. Umbo data might not be reliable in some conditions because of coverage by the graft. At middle and high frequencies: all materials showed a significant difference from the Normal TM in both umbo and stapes velocities for all perforation conditions except in the Annular Rim condition, in which silastic and perichondrium showed no significant difference from the Normal TM at umbo velocity in the middle frequencies. In the low frequencies, the choice of repair material does not seem to have a large effect on sound transfer. Our data also suggests that the annular rim could be important for low frequency sound transfer.

The effect of blast overpressure on the mechanical properties of the human tympanic membrane.

The rupture of the tympanic membrane (TM) is one of the major indicators for blast injuries due to the vulnerability of TM under exposure to blast overpressure. The mechanical properties of the human TM exhibit a significant change after it is exposed to such a high intensity blast. To date, the published data were obtained from measurement on TM strips cut from a TM following an exposure to blast overpressure. The dissection of a TM for preparation of strip samples can induce secondary damage to the TM and thus potentially lead to data not representative of the blast damage. In this paper, we conduct mechanical testing on the full TM in a human temporal bone. A bulging experiment on the entire TM is carried out on each sample prepared from a temporal bone following the exposure to blast three times at a pressure level slightly below the TM rupture threshold. Using a micro-fringe projection method, the volume displacement is obtained as a function of pressure, and their relationship is modeled in the finite element analysis to determine the mechanical properties of the post-blast human TMs, the results of which are compared with the control TMs without an exposure to the blast. It is found that Young's modulus of human TM decreases by approximately 20% after exposure to multiple blast waves. The results can be used in the human ear simulation models to assist the understanding of the effect of blast overpressure on hearing loss.

Long-term Outcomes of Balloon Dilation for Persistent Eustachian Tube Dysfunction.

OBJECTIVE: To gather long-term follow-up data on the efficacy of balloon dilation for treating patients with persistent Eustachian tube dysfunction (ETD). STUDY DESIGN: Extended follow-up study of the treatment arm of a prospective, multicenter, randomized controlled trial. SETTING: Tertiary care academic center and private practice. PATIENTS: Patients diagnosed with medically refractory persistent ETD. INTERVENTIONS: Balloon dilation of the Eustachian tube. MAIN OUTCOME MEASURES: The endpoints were the mean change from baseline in the 7-item Eustachian Tube Dysfunction Questionnaire (ETDQ-7) score, revision dilation rate, changes in assessments of middle ear function, and patient satisfaction. RESULTS: A total of 47 participants enrolled in the extended follow-up study. Mean follow-up was 29.4 months (range, 18-42 mo). There was a statistically significant mean (SD) change from baseline in the overall ETDQ-7 score (-2.5 ±â€Š1.2; p < 0.0001). A reduction of one or more in their overall ETDQ-7 score was observed by 93.6% (44/47) participants. The revision dilation rate was 2.1% (1/47). Among participants with abnormal baseline middle ear assessments, 76.0% had normalized tympanic membrane position (p < 0.0001), 62.5% had normalization of tympanogram type (p < 0.001), and 66.7% had positive Valsalva maneuvers (p < 0.0001). Participant satisfaction was 83.0% at long-term follow-up. CONCLUSIONS: Balloon dilation results in durable improvements in symptoms and middle ear assessments for patients with persistent Eustachian tube dysfunction at mean follow-up of longer than 2 years.

The effect of adenoid hypertrophy on hearing thresholds in children with otitis media with effusion.

INTRODUCTION: Otitis media with effusion is common middle ear mucosa disease that can cause hearing loss in children. Adenoid hypertrophy can cause recurrent acute otitis media in addition to otitis media with effusion as a result of eustachian tube dysfunction and primary infection focus. The aim of this study was to investigate the effect of adenoid hypertrophy on the hearing threshold in children suffering from otitis media with effusion. METHODS: Children of school age with otitis media with effusion were included in the study. The size and location of the adenoid tissue were determined by examination with a flexible endoscope. Four adenoid size groups were determined according to the percentage of choanal closure. The coverage was 0-25% in the first group, 26-50% in the second group, 51-75% in the third group and 76-100% in the 4th group. The location of the adenoid tissue in the nasopharynx was divided into three groups. In group A, the adenoid tissue was not in contact with torus tubarius. In group B, the adenoid tissue was in contact with the torus tubarius but did not cover it. In group C, the adenoid tissue covered the torus tubarius completely. Bone and air conduction thresholds were determined using standard procedures. The statistical relationship between the size and location of adenoid tissue and the hearing thresholds was investigated. RESULTS: The study was conducted with the 88 ears of 50 children aged 5-15 years. The median values of mean air conduction thresholds at 500 Hz, 1000 Hz, and 2000 Hz in the adenoid tissue size groups 1-4 were 22 dB HL, 20 dB HL, 15 dB HL, and 20 dB HL respectively. The median values of the mean air conduction thresholds were 20 dB HL, 20 dBHL and 18 dB HL in the adenoid location group A-C, respectively. No significant correlation was found between the groups (p:0.213) and the relevant hearing values (p:0.670). Type B tympanogram was identified in 46 ears and type C tympanogram in 42 ears. The mean hearing thresholds were significantly higher in the ears with a type B tympanogram in the otitis media with effusion cases. (P < 0.001).There was no significant correlation between the duration of effusion and the adenoid size (p:0.931), adenoid location (p:0.626) and hearing threshold (p:0.815). CONCLUSION: We concluded that adenoid tissue size and location have no effect on hearing thresholds and the duration of effusion in otitis media with effusion. We suggest caution before deciding on adenoidectomy in otitis media with effusion cases. Adenoidectomy should not be performed in children over 4 years of age unless there is a definite indication such as nasal obstruction or chronic adenitis.

[Progress in middle ear dysventilation research].

Disfunction of Eustachian tube will cause negative pressure of middle ear, which may result in tympanic membrane retraction pocket. Severe pocket can consequently cause cholesteatoma. In clinical practice it is not uncommon to find a cholesteatoma limited to epitympanum, with an otherwise normal pars tensa and mesotympanum. This review explains the theory of "selective epitympanic dysventilation syndrome" developed by endoscopic technique. In the majority of the patients, the only ventilation pathway to the epitympanum is through the tympanic isthmus. Even if Eustachian tube function has recovered, an isthmus blockage with selective epitympanic dysventilation may lead to common attic cholesteatoma.

Pars tensa and tympanicomalleal joint: proposal for a new anatomic classification.

PURPOSE: The tympanic membrane (TM) belongs to the ear. Despite its place in the ear anatomy, can we give it also a different anatomic classification? The main objective is to clarify the nature of TM, tympanic bone and malleus to propose a new anatomic classification. METHODS: This cadaveric study was performed in two human heads and six fresh temporal bones. A study of the temporomandibular joint, external acoustic meatus (EAM), TM and middle ear structures was conducted. A medical literature review englobing anatomy, embryology, histology and phylogeny of the ear was performed and the results were compared with the results of the dissection. RESULTS: The external ear is constituted by the auricle and the EAM. This last segment is made by a cartilaginous and an osseous portion. The osseous portion of the EAM is constituted mainly by tympanic bone. The external ear is separated from the middle ear by the TM. Inside the middle ear, there are three ossicles: malleus, incus and stapes, which allow the conduction of sound to the cochlea. Based on the anatomic dissection and medical literature review of the tympanic bone, malleus and TM, we propose that these structures are interconnected like a joint, and named it "Tympanicomalleal joint". CONCLUSIONS: It seems that the TM can be part of a joint that evolved to improve sound transmission and middle ear protection. Thinking TM has part of a joint may help in the development of more efficient reconstructive surgical techniques.

Model-based hearing diagnostics based on wideband tympanometry measurements utilizing fuzzy arithmetic.

Today's audiometric methods for the diagnosis of middle ear disease are often based on a comparison of measurements with standard curves, that represent the statistical range of normal hearing responses. Because of large inter-individual variances in the middle ear, especially in wideband tympanometry (WBT), specificity and quantitative evaluation are greatly restricted. A new model-based approach could transform today's predominantly qualitative hearing diagnostics into a quantitative and tailored, patient-specific diagnosis, by evaluating WBT measurements with the aid of a middle-ear model. For this particular investigation, a finite element model of a human ear was used. It consisted of an acoustic ear canal and a tympanic cavity model, a middle-ear with detailed nonlinear models of the tympanic membrane and annular ligament, and a simplified inner-ear model. This model has made it possible for us to simulate pathologies like the stiffening of ligaments or joints, because we can simply change the corresponding mechanical parameters of the model. On the other hand, it is also possible to identify pathologies from measurements, by analyzing the parameters obtained by a system identification procedure. This reduces the number of required model parameters through sensitivity studies and parameter clustering. Uncertainties due to the lack of knowledge, subjectivity in numerical implementation and model simplification are taken into account by the application of fuzzy arithmetic. The most confident parameter set can be determined by applying an inverse fuzzy method on the measurement data. The principle and the benefits of this model-based approach are illustrated by the example of a two-mass oscillator, and also by the simulation of the energy absorbance of an ear with malleus fixation, where the parameter changes that are introduced can be determined quantitatively through the system identification.

Vibroplasty combined with tympanic membrane reconstruction in middle ear ventilation disorders.

Although the Vibrant Soundbridge is one of the most frequently used active middle ear implants, data regarding how middle ear ventilation disorders may affect the transmission behavior of its floating mass transducer are still insufficient. Studies involving coupling the floating mass transducer to the stapes head are particularly lacking. This temporal bone study evaluated the influence of simulated middle ear ventilation disorders on the middle ear transfer function in the reconstructed middle ear. The middle ear transfer function was measured using Laser Doppler Vibrometry after vibroplasty onto the stapes head, with or without tympanic membrane reconstruction. Middle ear ventilation disorders were simulated through changes in static pressure via the external ear channel with a maximum pressure of +3 kPa. Slice thickness of tympanic membrane reconstruction material was measured using micro-CT. When the reconstructed ossicular chain and the reconstructed tympanic membrane were mechanically excited by the floating mass transducer under conditions of ambient static pressure, the transmission behavior was found to be independent of the type of tissue used. Increase in static pressure up to +3 kPa caused maximum low frequency transmission loss of 15 dB when elastic grafts were used and 5 dB when stiff tissue was inserted. At high frequencies, measured loss of up to 5 dB was relatively independent of the tissue stiffness. Increase in static pressure led to displacement of the tissues towards the vestibulum and caused stiffening, especially of the annular ligament. Stiffening-induced transmission losses were mainly found at low frequencies and could not be compensated by the floating mass transducer in this range. Above 1300 Hz, the continuous force spectrum of the actuator sufficiently protected against loss of amplitude. To minimize postoperative transmission loss due to persisting ventilation disorders, choosing a very stiff tympanic membrane reconstruction material seems to be appropriate.

Distortion product otoacoustic emissions: Sensitive measures of tympanic -membrane perforation and healing processes in a gerbil model.

Distortion product otoacoustic emissions (DPOAEs) evoked by two pure tones carry information about the mechanisms that generate and shape them. Thus, DPOAEs hold promise for providing powerful noninvasive diagnostic details of cochlear operations, middle ear (ME) transmission, and impairments. DPOAEs are sensitive to ME function because they are influenced by ME transmission twice, i.e., by the inward-going primary tones in the forward direction and the outward traveling DPOAEs in the reverse direction. However, the effects of ME injuries on DPOAEs have not been systematically characterized. The current study focused on exploring the utility of DPOAEs for examining ME function by methodically characterizing DPOAEs and ME transmission under pathological ME conditions, specifically under conditions of tympanic-membrane (TM) perforation and spontaneous healing. Results indicated that DPOAEs were measurable with TM perforations up to ∼50%, and DPOAE reductions increased with increasing size of the TM perforation. DPOAE reductions were approximately flat across test frequencies when the TM was perforated about 10% (<1/8 of pars tensa) or less. However, with perforations greater than 10%, DPOAEs decreased further with a low-pass filter shape, with ∼30 dB loss at frequencies below 10 kHz and a quick downward sloping pattern at higher frequencies. The reduction pattern of DPOAEs across frequencies was similar to but much greater than, the directly measured ME pressure gain in the forward direction, which suggested that reduction in the DPOAE was a summation of losses of ME ear transmission in both the forward and reverse directions. Following 50% TM perforations, DPOAEs recovered over a 4-week spontaneously healing interval, and these recoveries were confirmed by improvements in auditory brainstem response (ABR) thresholds. However, up to 4-week post-perforation, DPOAEs never fully recovered to the levels obtained with normal intact TM, consistent with the incomplete recovery of ABR thresholds and ME transmission, especially at high-frequency regions, which could be explained by an irregularly dense and thickened healed TM. Since TM perforations in patients are commonly caused by either trauma or infection, the present results contribute towards providing insight into understanding ME transmission under pathological conditions as well as promoting the application of DPOAEs in the evaluation and diagnosis of deficits in the ME-transmission system.

Dual-laser measurement and finite element modeling of human tympanic membrane motion under blast exposure.

Hearing damage is one of most prevalent injuries in military personnel and civilians exposed to a blast. However, the mechanism of how the blast overpressure interacts with the tympanic membrane (TM) and impairs the peripheral auditory system still remains unclear. A 3D finite element (FE) model of the human ear has been developed to predict the blast overpressure transmission through the ear (Leckness et al., 2018), but the model needs to be further validated in TM response to blast pressure. This paper reports the first-ever approach using two laser Doppler vibrometers (LDVs) to measure the motion of the TM when the ear was exposed to a blast. Five fresh human temporal bones were used in this study with a pressure sensor inserted near the TM to measure the pressure reaching the TM (P1). The temporal bone was mounted in a "head block" and exposed to blast at the overpressure around 35 kPa measured at the entrance of the ear canal (P0). The movements of the TM at the umbo and the "head block" were measured simultaneously by two LDVs and the exact motion of the TM was determined by subtracting the head block motion from the TM data. Results include that the maximum TM velocity was 12.62 ±â€¯3.63 m/s (mean ±â€¯SD) and the displacement was 0.78 ±â€¯0.26 mm. The peak-to-peak displacement normalized by the P0 pressure was 22.9 ±â€¯6.6 µm/kPa. The frequency domain analysis indicated that the spectrum peaks were located at frequencies below 3 kHz. The TM motion was then compared with that calculated from the FE model of the human ear with the measured P0 pressure wave applied at the ear canal entrance. The FE model-derived TM displacement under blast overpressure was consistent with the experimental results. This study provides a new methodology to determine the behavior of the middle ear in response to blast overpressure. The experimental data are critical for validating the FE model of the human ear for blast wave transduction and understanding the TM damage induced by blast exposure.

Tympanogram Findings in Hemodialysis Patients.

BACKGROUND: The aim of this study is to investigate whether changes in cerebrospinal fluid (CSF) pressure during the hemodialysis (HD) treatment are reflected on tympanometric measurements. METHODS: The study was performed on 24 HD patients. The static compliance and absorbance values of the patients before and after HD were measured using a wideband tympanometry. The tympanogram tests were performed immediately before and at the end of the HD session. RESULTS: The static compliance values of the patients after HD were significantly lower than those before HD. This decrease significantly correlated with the adequacy of dialysis determined by urea reduction rate and Kt/V. The absorbance values showed a decrease in the band 343 and 727 Hz, but no significant difference was found in other frequencies. The static admittance and absorbance values were influenced by the HD process. DISCUSSION: This influence might be due to the increase in CSF pressure as a result of the removal of urea from blood during HD session.