Coupled membranes: a mechanism of frequency filtering and transmission in the field cricket ear evidenced by micro-computed tomography, laser Doppler vibrometry and finite element analysis.

Many animals employ a second frequency filter beyond the initial filtering of the eardrum (or tympanal membrane). In the field cricket ear, both the filtering mechanism and the transmission path from the posterior tympanal membrane (PTM) have remained unclear. A mismatch between PTM vibrations and sensilla tuning has prompted speculations of a second filter. PTM coupling to the tracheal branches is suggested to support a transmission pathway. Here, we present three independent lines of evidence converging on the same conclusion: the existence of a series of linked membranes with distinct resonant frequencies serving both filtering and transmission functions. Micro-computed tomography (µ-CT) highlighted the 'dividing membrane (DivM)', separating the tracheal branches and connected to the PTM via the dorsal membrane of the posterior tracheal branch (DM-PTB). Thickness analysis showed the DivM to share significant thinness similarity with the PTM. Laser Doppler vibrometry indicated the first of two PTM vibrational peaks, at 6 and 14 kHz, originates not from the PTM but from the coupled DM-PTB. This result was corroborated by µ-CT-based finite element analysis. These findings clarify further the biophysical source of neuroethological pathways in what is an important model of behavioural neuroscience. Tuned microscale coupled membranes may also hold biomimetic relevance.

Semi-automatic algorithm to build finite element numerical models of the human hearing system from Micro-CT data.

Finite Element modeling has been an extended methodology to build numerical model to simulate the behavior of the hearing system. Due to the complexity of the system and the difficulties to reduce the uncertainties of the geometric data, they result in computationally expensive models, sometimes generic, representative of average geometries. It makes it difficult to validate the model with direct experimental data from the same specimen or to establish a patient-oriented modeling strategy. In the present paper, a first attempt to automatize the process of model building is made. The source information is geometrical information obtained from CT of the different elements that compose the system. Importing that data, we have designed the complete procedure to build a model including tympanic membrane, ossicular chain and cavities. The methodology includes the proper coupling of all the elements and the generation of the corresponding finite element model. The whole automatic procedure is not complete, as we need to make some human-assisted decisions; however, the model development time is reduced from 4 weeks to approximately 3 days. The goal of the modeling algorithm is to build a Finite Element Model with a limited computational cost. Several tasks as contour identification or model decimation are designed and integrated in order to follow a semi-automated process that allows generating a patient-oriented model.

Tympanic membrane perforations cannot be reliably detected using computed tomography based on 15 cadaver dogs.

The integrity of the tympanic membrane is an important factor when deciding treatment and therapeutic recommendations for dogs with ear disease; however, otoscopic examination may be difficult to perform due to features of external ear canal disease or patient compliance. CT is useful for the evaluation of middle ear disease, including cases in which middle ear disease is detected incidentally. The tympanic membrane is detectable using CT, but anecdotally, apparent focal defects or discontinuities of the tympanic membrane are often seen in patients with and without ear disease. The purpose of this prospective, observer agreement study was to determine if perforations of the tympanic membrane are reliably detectable on CT. Fifteen cadaver dogs underwent CT and video otoscopy to verify the integrity of each tympanic membrane. Cadavers were randomly assigned to have the tympanic membranes left intact or to undergo a myringotomy on either the left, the right, or both sides. CT was performed immediately following the myringotomies. Four blinded evaluators evaluated the pre- and post-myringotomy scans for a total of 30 scans (60 tympanic membranes). Average accuracy was low (44%), and interobserver agreement for all four evaluators was fair. Although the tympanic membrane is visible on CT, perforations of the tympanic membrane are unlikely to be accurately detected or excluded. The appearance of an intact tympanic membrane or defect in the membrane on CT should not be used as criteria to guide clinical treatment recommendations based on this cadaver model.

Registration of preoperative temporal bone CT-scan to otoendoscopic video for augmented-reality based on convolutional neural networks.

PURPOSE: Patient-to-image registration is a preliminary step required in surgical navigation based on preoperative images. Human intervention and fiducial markers hamper this task as they are time-consuming and introduce potential errors. We aimed to develop a fully automatic 2D registration system for augmented reality in ear surgery. METHODS: CT-scans and corresponding oto-endoscopic videos were collected from 41 patients (58 ears) undergoing ear examination (vestibular schwannoma before surgery, profound hearing loss requiring cochlear implant, suspicion of perilymphatic fistula, contralateral ears in cases of unilateral chronic otitis media). Two to four images were selected from each case. For the training phase, data from patients (75% of the dataset) and 11 cadaveric specimens were used. Tympanic membranes and malleus handles were contoured on both video images and CT-scans by expert surgeons. The algorithm used a U-Net network for detecting the contours of the tympanic membrane and the malleus on both preoperative CT-scans and endoscopic video frames. Then, contours were processed and registered through an iterative closest point algorithm. Validation was performed on 4 cases and testing on 6 cases. Registration error was measured by overlaying both images and measuring the average and Hausdorff distances. RESULTS: The proposed registration method yielded a precision compatible with ear surgery with a 2D mean overlay error of 0.65 ± 0.60 mm for the incus and 0.48 ± 0.32 mm for the round window. The average Hausdorff distance for these 2 targets was 0.98 ± 0.60 mm and 0.78 ± 0.34 mm respectively. An outlier case with higher errors (2.3 mm and 1.5 mm average Hausdorff distance for incus and round window respectively) was observed in relation to a high discrepancy between the projection angle of the reconstructed CT-scan and the video image. The maximum duration for the overall process was 18 s. CONCLUSIONS: A fully automatic 2D registration method based on a convolutional neural network and applied to ear surgery was developed. The method did not rely on any external fiducial markers nor human intervention for landmark recognition. The method was fast and its precision was compatible with ear surgery.

Remote paediatric ear examination comparing video-otoscopy and still otoscopy clinician rated outcomes.

OBJECTIVE: Telemedicine, particularly real time video-otoscopy in rural and remote Australia holds great potential in assessing and managing otology conditions. There is good evidence of store and forward images for assessment, however limited evidence exists for the use of real-time video-otoscopy. The objective of this study was to assess the validity of using real time video-otoscopy, compared to standard store and forward still image otoscopy, in a paediatric population. METHOD: Fifty-two paediatric tympanic membranes in 27 patients were examined and photographed by a telehealth facilitator with prior otoscope training. This occurred at two rural Western Australian health centre sites. These images were stored and forwarded to a tertiary paediatric hospital for otolaryngology department assessment on the day of real-time video-otoscopy consultation. During this consultation the same twenty-seven patients underwent real-time video-otoscopy assessment, which was recorded. Across six domains including, image quality, focus, light, cerumen amount, field of view and tympanic membrane landmarks, real-time video-otoscopy was compared against still image capture. The recording of each real-time video-otoscopy and still image tympanic membrane was assessed by two otology specialists for the ability to diagnose each as either normal or abnormal. An inter-rater reliability agreement was then calculated. RESULTS: There was greater image adequacy across five of the six domains for real time video-otoscopy compared to standard store and forward otoscopy images. Substantial agreement in diagnosing each tympanic membrane as either normal or abnormal between each rater was evident. CONCLUSION: This study supports the use of real time video-otoscopy during telemedicine consultation. With greater image quality, focus, light, field of view and identification of tympanic membrane landmarks video-otoscopy compared to still images has broad clinical applications. This includes primary assessment of the tympanic membrane and post operative follow-up clinical settings. Video-otoscopy offers a promising new way to over-come barriers in delivering ear health care in rural populations.

Assessment of tympanic membrane perforation size using ImageJ software by ENT clinicians of different grades.

OBJECTIVE: To compare visual estimation versus ImageJ calculation of tympanic membrane perforation size in the paediatric population between clinicians of different experience. METHODS: Five images of tympanic membrane perforations in children, captured using an otoendoscope, were selected. The gold standard was the ImageJ results by one consultant otologist. Consultants, registrars and Senior House Officers or equivalent were asked to visually estimate and calculate the perforation size using ImageJ software. RESULTS: The mean difference in variation from gold standard between visual estimation and ImageJ calculation was 12.16 per cent, 95 per cent CI (10.55, 13.78) p < 0.05, with ImageJ providing a more accurate estimation of perforation. Registrars were significantly more accurate at visual estimation than senior house officers. There was no statistically significant difference in ImageJ results between the different grades. CONCLUSION: Using ImageJ software is more accurate at estimating tympanic membrane perforation size than visual assessment for all ENT clinicians regardless of experience.

Assessment of middle ear structure and function with optical coherence tomography.

BACKGROUND: Current clinical tests for middle ear (ME) injuries and related conductive hearing loss (CHL) are lengthy and costly, lacking the ability to noninvasively evaluate both structure and function in real time. Optical coherence tomography (OCT) provides both, but its application to the audiological clinic is currently limited. OBJECTIVE: Adapt and use a commercial Spectral-Domain OCT (SD-OCT) to evaluate anatomy and sound-evoked vibrations of the tympanic membrane (TM) and ossicles in the human ME. MATERIALS AND METHODS: SD-OCT was used to capture high-resolution three-dimensional (3D) ME images and measure sound-induced vibrations of the TM and ossicles in fresh human temporal bones. RESULTS: The 3D images provided thickness maps of the TM. The system was, with some software adaptations, also capable of phase-sensitive vibrometry. Measurements revealed several modes of TM vibration that became more complex with frequency. Vibrations were also measured from the incus, through the TM. This quantified ME sound transmission, which is the essential measure to assess CHL. CONCLUSION AND SIGNIFICANCE: We adapted a commercial SD-OCT to visualize the anatomy and function of the human ME. OCT has the potential to revolutionize point-of-care assessment of ME disruptions that lead to CHL which are otherwise indistinguishable via otoscopy.

[Imaging evaluation of cerebrospinal fluid otorrhea associated with inner ear malformation in children].

Objective: To explore the imaging evaluation of cerebrospinal fluid (CSF) otorrhea associated with inner ear malformation (IEM) in children. Methods: The clinical data of 28 children with CSF otorrhea associated with IEM confirmed by surgical exploration in Beijing Children's Hospital, from Nov, 2016 to Jan, 2021, were analyzed retrospectively,including 16 boys and 12 girls, aged from 8-month to 15-year and 8-month old, with a median age of 4-year old. The shapes of stapes were observed during the exploration surgery, and the imaging features of temporal bone high resolution CT(HRCT) and inner ear MRI pre- and post-operation were analyzed. Results: In 28 children with CSF otorrhea, 89.3%(25/28) had stapes footplates defect during exploration. Preoperative CT showed indirect signs such as IEM, tympanic membrane bulging, soft tissue in the tympanum and mastoid cavity. IEM included four kinds: incomplete partition type I (IP-Ⅰ), common cavity (CC), incomplete partition type Ⅱ (IP-Ⅱ), and cochlear aplasia (CA); 100%(28/28) presented with vestibule dilation; 85.7%(24/28) with a defect in the lamina cribrosa of the internal auditory canal. The direct diagnostic sign of CSF otorrrhea could be seen in 73.9%(17/23) pre-operative MRI: two T2-weighted hyperintense signals between vestibule and middle ear cavity were connected by slightly lower or mixed intense T2-weighted signals, and obvious in the coronal-plane; 100%(23/23) hyperintense T2-weighted signals in the tympanum connected with those in the Eustachian tube.In post-operative CT, the soft tissues in the tympanum and mastoid cavity decreased or disappeared as early as one week. In post-operative MRI, the hyperintense T2-weighted signals of tympanum and mastoid decreased or disappeared in 3 days to 1 month,soft tissues tamponade with moderate intense T2-weighted signal were seen in the vestibule in 1-4 months. Conclusions: IP-Ⅰ, CC, IP-Ⅱ and CA with dilated vestibule can lead to CSF otorrhea. Combined with special medical history, T2-weighted signal of inner ear MRI can provide diagnostic basie for most children with IEM and CSF otorrhea.HRCT and MRI of inner ear can also be used to evaluate the effect of surgery.

In vivo microstructural investigation of the human tympanic membrane by endoscopic polarization-sensitive optical coherence tomography.

Significance: Endoscopic optical coherence tomography (OCT) is of growing interest for in vivo diagnostics of the tympanic membrane (TM) and the middle ear but generally lacks a tissue-specific contrast. Aim: To assess the collagen fiber layer within the in vivo TM, an endoscopic imaging method utilizing the polarization changes induced by the birefringent connective tissue was developed. Approach: An endoscopic swept-source OCT setup was redesigned and extended by a polarization-diverse balanced detection unit. Polarization-sensitive OCT (PS-OCT) data were visualized by a differential Stokes-based processing and the derived local retardation. The left and right ears of a healthy volunteer were examined. Results: Distinct retardation signals in the annulus region of the TM and near the umbo revealed the layered structure of the TM. Due to the TM's conical shape and orientation in the ear canal, high incident angles onto the TM's surface, and low thicknesses compared to the axial resolution limit of the system, other regions of the TM were more difficult to evaluate. Conclusions: The use of endoscopic PS-OCT is feasible to differentiate birefringent and nonbirefringent tissue of the human TM in vivo. Further investigations on healthy as well as pathologically altered TMs are required to validate the diagnostic potential of this technique.

Making Use of Artificial Intelligence-Generated Synthetic Tympanic Membrane Images.

This diagnostic study examines the application of generative artificial intelligence in clinical tool research and development.

Rabbit tympanic membrane thickness distribution obtained via optical coherence tomography.

Knowing the precise tympanic membrane (TM) thickness variation is crucial in understanding the functional properties of the TM and has a significant effect on the accuracy of computational models. Using optical coherence tomography, we imaged five left and five right TMs of domestic New Zealand rabbits. From these data, ten thickness distribution maps were computed. Although inter-specimen variability is present, similar features could be observed in all samples: The rabbit TM is thickest around the umbo, with values of 150 ± 32 µm. From the umbo towards the TM annulus, the thickness gradually decreases down to 38 ± 7 µm around the midway location, but increases up to 54 ± 19 µm at the TM annulus. The thickness values at the umbo are comparable to literature data for humans, but the rabbit TM is thinner at the TM annulus and in-between the umbo and annulus. Moreover, the rabbit TM thickness distribution is highly symmetrical, which is not the case for the human TM. The results improve our general understanding of TM structure in rabbits and may improve numerical models of TM dynamical behavior.

Smartphone-enabled otoscopy: method evaluation in clinical practice.

OBJECTIVE: To assess the diagnostic agreement between smartphone-enabled otoscopy and rigid otoendoscopy in tympanic membrane and middle ear diseases. METHODS: A cross-sectional study was carried out to analyze otoscopies in patients seen at a general otorhinolaryngology (ORL) outpatient clinic, from June to December 2019. Eighty-three images of patients obtained from otoscopies performed through a smartphone device and a rigid endoscope were included, recorded, and stored for further analysis. The images were first analyzed by an experienced otologist, who assigned his diagnostic impression (defined as the gold standard) on each of the images. After this analysis, the images were displayed to a group of secondary raters (an experienced otorhinolaryngologist, a second-year resident in ORL, and a general practitioner). A questionnaire was applied related to each image. RESULTS: There was high agreement between the smartphone device and the otoendoscopy images for all professionals, with a Kappa coefficient of 0.97 (p < 0.001). The smartphone device showed a diagnostic sensitivity of 81.1% and a specificity of 71.1%. As for the otoendoscopy, it showed a sensitivity of 84.7% and a specificity of 72.4%. The image classification as "2 = Good" was the most frequent one, with 34.9% for otoendoscopy and 31.6% for the smartphone device. CONCLUSION: There was a high diagnostic agreement between smartphone device-guided otoscopy and the rigid otoendoscopy, demonstrating the feasibility of using this device in clinical practice.

Machine Learning in Diagnosing Middle Ear Disorders Using Tympanic Membrane Images: A Meta-Analysis.

OBJECTIVE: To systematically evaluate the development of Machine Learning (ML) models and compare their diagnostic accuracy for the classification of Middle Ear Disorders (MED) using Tympanic Membrane (TM) images. METHODS: PubMed, EMBASE, CINAHL, and CENTRAL were searched up until November 30, 2021. Studies on the development of ML approaches for diagnosing MED using TM images were selected according to the inclusion criteria. PRISMA guidelines were followed with study design, analysis method, and outcomes extracted. Sensitivity, specificity, and area under the curve (AUC) were used to summarize the performance metrics of the meta-analysis. Risk of Bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool in combination with the Prediction Model Risk of Bias Assessment Tool. RESULTS: Sixteen studies were included, encompassing 20254 TM images (7025 normal TM and 13229 MED). The sample size ranged from 45 to 6066 per study. The accuracy of the 25 included ML approaches ranged from 76.00% to 98.26%. Eleven studies (68.8%) were rated as having a low risk of bias, with the reference standard as the major domain of high risk of bias (37.5%). Sensitivity and specificity were 93% (95% CI, 90%-95%) and 85% (95% CI, 82%-88%), respectively. The AUC of total TM images was 94% (95% CI, 91%-96%). The greater AUC was found using otoendoscopic images than otoscopic images. CONCLUSIONS: ML approaches perform robustly in distinguishing between normal ears and MED, however, it is proposed that a standardized TM image acquisition and annotation protocol should be developed. LEVEL OF EVIDENCE: NA Laryngoscope, 133:732-741, 2023.

Sinus tympani revisited for planning retrofacial approach-radiologic study in pneumatized temporal bones and its surgical implications.

BACKGROUND AND PURPOSE: Retrofacial approach (RFA) is an access route to sinus tympani (ST) and it is used in cholesteatoma surgery, especially when type C ST is encountered. It may also be used to gain an access to stapedius muscle to assess the evoked stapedius reflex threshold. The primary object of this study was to evaluate the morphology of sinus tympani and its relationship to facial nerve (FN) and posterior semicircular canal (PSC) in context of planning retrofacial approach in pneumatized temporal bones. METHODS: CBCT of 130 adults were reviewed. The type of sinus tympani was assessed according to Marchioni's classification. Width of entrance to sinus tympani (STW), depth of ST (STD), distance between the posterior semicircular canal and facial nerve (F-PSC), distance between the latter plane to the floor of ST at the right angle (P-ST) were measured at level of round window (RW) and pyramidal ridge (PR). RESULTS: All of the bones were well-aerated and classified in Dexian Tan pneumatization group 3 or 4. Type B of ST is dominant (70.8%) in adult population with no history of inflammatory otologic diseases, followed by type C (22.7%) and then type A (6.5%). The depth of ST (STD) presented significant deviations (ANOVA, p < 0.05) among all three types. STW reaches greater values on the level of PR. F-PSC does not correlate with type of ST. In over 75% of examined type C sinus tympani the distance P-ST was less than 1 mm. CONCLUSIONS: The qualitative classification of the sinus tympani into types A, B and C, introduced by Marchioni is justified by statistically significant differences of depth between individual types of tympanic sinuses. The STW distance reaches greater values inferiorly-it may suggest that RFA should be performed in infero-superior manner rather than opposite direction. Preoperative assessment of temporal bones CT scans gives very important information about size of sinus tympani and distance between FN and PSC.

Radiological Evaluation of Tympanic Segment of Chorda Tympani Nerve in Normal Ears: An Ultra-High-Resolution Computed Tomography Study.

BACKGROUND: To visualize the course of the tympanic segment of chorda tympani nerve (CTN) using ultra-high-resolution computed tomography. METHODS: A hundred and fourteen ears with no evident otologic pathologies were included. The tympanic segment of CTN was divided into 4 portions as follows: periannular, posteromalleal, malleal, and anteromalleal. The length of the periannular portion running along the tympanic annulus was recorded. Four points of interest (the beginning and end of the posteromalleal and anteromalleal portions) were selected to perform distance measurements relative to the tip of the malleus manubrium. Differences in lengths and distances were compared in terms of ear sides and sexes. RESULTS: The length of the periannular portion was 2.49 ± 1.16 mm. The beginning of the posteromalleal portion was located more laterally on the right side than on the left side (mean: 4.09 mm vs. 3.92 mm;, P = 0.016). The end of the posteromalleal portion was located more inferiorly on the right (mean: 2.11 mm vs. 2.26 mm; P = 0.018). The beginning of the anteromalleal portion on the right was located more laterally than that on the left (mean: 2.60 mm vs. 2.45 mm; P = 0.027). The start and end of the anteromalleal portion were more posteriorly located in women than in men (both Ps < 0.001). CONCLUSIONS: The course of the tympanic segment of normal CTN was comprehensively visualized by ultra-high-resolution computed tomography. Preoperative evaluation of the tympanic segment of CTN might be helpful in avoiding iatrogenic injury during middle ear surgery.

Radiological and Audiological Prediction for Ossicular Fixation in Chronic Otitis Media and Tympanic Membrane Perforation.

OBJECTIVES: Recurrent middle-ear infection can lead to ossicular fixation, adversely affecting post-tympanoplasty hearing outcomes. Preoperative prediction of ossicular fixation remains challenging. We aimed to investigate potential predictors of ossicular fixation in patients with chronic otitis media. STUDY DESIGN: Retrospective. SETTING: Tertiary academic medical center. PATIENTS: Patients with noncholesteatomatous chronic otitis media and tympanic membrane perforation, without ossicular discontinuities. INTERVENTIONS: Diagnostic. MAIN OUTCOME MEASURES: The fixation of each ossicle was assessed during tympanoplasty. The impact of preoperative otoscopic findings, computed tomography (CT) features, and hearing levels on the prediction of ossicular fixation was evaluated using uni- and multivariable logistic regression analyses. RESULTS: One hundred thirty-five patients were included. Soft-tissue density between the malleus head and the anterior wall (odds ratio, 3.789 [95% confidence interval, 1.177-12.196]; p = 0.0255) and poor development of mastoid cells (16.826 [2.015-134.520]; p = 0.0078) were independent predictors of malleus fixation. In addition, ≥50% tympanic membrane perforation (5.412 [1.908-15.353]; p = 0.0015), poor development of mastoid cells (3.386 [1.039-11.034]; p = 0.0431), and a ≥40-dB preoperative air-bone gap (ABG) at 500 Hz (4.970 [1.732-14.261]; p = 0.0029) were independent predictors of incus fixation. Soft-tissue density surrounding the stapes (18.833 [1.856-191.104]; p = 0.0119) and a ≥40-dB preoperative ABG at 500 Hz (13.452 [1.640-∞]; p = 0.0138) were correlated with stapes fixation. CONCLUSIONS: The accurate prediction of ossicular fixation in patients with chronic otitis media based on CT features and the ABG may facilitate decision-making regarding the need for ossiculoplasty, possibly avoiding unnecessary manipulation or overlooking of fixation.

Analysis of tympanic sinus shape for purposes of intraoperative hearing monitoring: a microCT study.

PURPOSE: Sinus tympani is the space in the retrotympanum, with variable morphology. Computed tomography is a common tool to investigate sinus tympani anatomy. During cochlear implantation or tympanoplasty, electrocochleography can be used for hearing monitoring. In such a surgical strategy the electrode is placed in the round window's region throughout posterior tympanotomy. Common accessible needle-shaped electrodes using is difficult in achieving intraoperative stabilization. The aim of the study is to assess the dimensions and shape of sinus tympani, basing on the micro computed tomography scans for purposes of establishing the possible new electrocochleography electrode shape. MATERIALS AND METHODS: Sixteen fresh frozen cadaveric temporal bones were dissected. MicroCT measurements included the depth and the width of sinus tympani, width of facial canal with stapedius muscle chamber. Obtained data were analyzed statistically with the use of RStudio 1.3.959 software. RESULTS: The highest average width of sinus tympani amounted for 2.68 mm, depth measured at the round window plane for 3.19 mm. Width of facial canal with stapedius muscle chamber highest average values at the round window plane- 3.32 mm. The lowest average minimum and maximum values were calculated at the 1 mm above the round window plane. The highest average posterior tympanotomy width was 2.91 mm. CONCLUSIONS: The shape of the tympanic sinus is like a trough with the narrowest and deepest dimensions in the middle part. The ST shape and dimensions should be taken into account in constructing the ECochG electrode, designed for optimal placement through posterior tympanotomy approach.

Prestrain in the rabbit eardrum measured by digital image correlation and micro-incisions.

Prestrain in the absence of external loads can have an important effect on the vibrational behavior of mechanical systems such as the middle ear. Studies that measure tympanic membrane (TM) prestrain are scarce, however, and provide no conclusive answer on the existence and nature of the prestrain. In this study, prestrain is measured in the TM of cadaveric rabbit ears by stereo digital image correlation. To release the prestrain, straight incisions of 0.33 mm are made on different locations in the TM with a direction parallel to either the radial or circular fibers in the membrane. The effect of sample dehydration during different stages in the experimental procedure is assessed and eliminated by rehydrating the samples directly before each measurement. The measurements demonstrate average prestrain values around the incisions between 3.52±2.34% and 13.62±7.92% for the different locations, with a noise floor of 0.07%. No clear differences were found between the prestrain values obtained for radial and circular incisions. Observed local variations in TM prestrain could not be clearly related to specific locations on the TM. The results suggest that TM prestrain may need to be considered in future studies of middle-ear function if the findings can be confirmed in human ears.

Analyses of the Tympanic Membrane Impulse Response Measured with High-Speed Holography.

The Tympanic Membrane (TM) transforms acoustic energy to ossicular vibration. The shape and the displacement of the TM play an important role in this process. We developed a High-speed Digital Holography (HDH) system to measure the shape and transient displacements of the TM induced by acoustic clicks. The displacements were further normalized by the measured shape to derive surface normal displacements at over 100,000 points on the TM surface. Frequency and impulse response analyses were performed at each TM point, which enable us to describe 2D surface maps of four new TM mechanical parameters. From frequency domain analyses, we describe the (i) dominant frequencies of the displacement per sound pressure based on Frequency Response Function (FRF) at each surface point. From time domain analyses, we describe the (ii) rising time, (iii) exponential decay time, and the (iv) root-mean-square (rms) displacement of the TM based on Impulse Response Function (IRF) at each surface point. The resultant 2D maps show that a majority of the TM surface has a dominant frequency of around 1.5 kHz. The rising times suggest that much of the TM surface is set into motion within 50 µs of an impulsive stimulus. The maps of the exponential decay time of the IRF illustrate spatial variations in damping, the least known TM mechanical property. The damping ratios at locations with varied dominant frequencies are quantified and compared.

Rare case of ballooning herniation of the tympanic membrane.

Herniation of the tympanic membrane is a rare benign malformation of the tympanic membrane into the external auditory canal. It may be asymptomatic or associated with symptoms such as aural fullness, tinnitus, otalgia or hearing loss. We present a case of a symptomatic herniation of the tympanic membrane and its surgical therapy with hernia excision and tympanoplasty. An internal review board exemption was obtained.