Differential effects of mass-loading the eardrum and stiffening the middle ear on wideband absorbance.

The current work investigated the effects of mass-loading the eardrum on wideband absorbance in humans. A non-invasive approach to mass-loading the eardrum was utilized in which water was placed on the eardrum via ear canal access. The mass-loaded absorbance was compared to absorbance measured for two alternative middle ear states: normal and stiffened. To stiffen the ear, subjects pressurized the middle ear through either exsufflation or insufflation concurrent with Eustachian tube opening. Mass-loading the eardrum was hypothesized to reduce high-frequency absorbance, whereas pressurizing the middle ear was hypothesized to reduce low- to mid-frequency absorbance. Discriminant linear analysis classification was performed to evaluate the utility of absorbance in differentiating between conditions. Water on the eardrum reduced absorbance over the 0.7- to 6-kHz frequency range and increased absorbance at frequencies below approximately 0.5 kHz; these changes approximated the pattern of changes reported in both hearing thresholds and stapes motion upon mass-loading the eardrum. Pressurizing the middle ear reduced the absorbance over the 0.125- to 4-kHz frequency range. Several classification models based on the absorbance in two- or three-frequency bands had accuracy exceeding 88%.

Reconsidering tympanal-acoustic interactions leads to an improved model of auditory acuity in a parasitoid fly.

Although most binaural organisms locate sound sources using neurological structures to amplify the sounds they hear, some animals use mechanically coupled hearing organs instead. One of these animals, the parasitoid flyOrmia ochracea(O. ochracea), has astoundingly accurate sound localization abilities. It can locate objects in the azimuthal plane with a precision of 2°, equal to that of humans, despite an intertympanal distance of only 0.5 mm, which is less than1/100th of the wavelength of the sound emitted by the crickets that it parasitizes.O. ochraceaaccomplishes this feat via mechanically coupled tympana that interact with incoming acoustic pressure waves to amplify differences in the signals received at the two ears. In 1995, Mileset aldeveloped a model of hearing mechanics inO. ochraceathat represents the tympana as flat, front-facing prosternal membranes, though they lie on a convex surface at an angle from the flies' frontal and transverse planes. The model works well for incoming sound angles less than±30∘but suffers from reduced accuracy (up to 60% error) at higher angles compared to response data acquired fromO. ochraceaspecimens. Despite this limitation, it has been the basis for bio-inspired microphone designs for decades. Here, we present critical improvements to this classic hearing model based on information from three-dimensional reconstructions ofO. ochracea's tympanal organ. We identified the orientation of the tympana with respect to a frontal plane and the azimuthal angle segment between the tympana as morphological features essential to the flies' auditory acuity, and hypothesized a differentiated mechanical response to incoming sound on the ipsi- and contralateral sides that depend on these features. We incorporated spatially-varying model coefficients representing this asymmetric response, making a new quasi-two-dimensional (q2D) model. The q2D model has high accuracy (average errors of under 10%) for all incoming sound angles. This improved biomechanical model may inform the design of new microscale directional microphones and other small-scale acoustic sensor systems.

Shedding light on the tympanic membrane: a brief history of the description and understanding of its anatomy.

OBJECTIVE: For centuries, the tympanum has remained the only visible structure of the organ of hearing. This study aimed to trace the understanding of the tympanic membrane from antiquity to the early twentieth century. METHODS: A review was conducted of primary and secondary historical and scientific literature describing the tympanic membrane anatomy. RESULTS: Although ancient polymaths sensed that sounds were vibrations that could spread in the air and be perceived by the hearing organ, there were numerous misconceptions about the tympanum until human dissections performed during the Renaissance. The tympanum was correctly described only centuries later when technological advances enabled otologists to understand it as a fundamental part of the hearing organ. CONCLUSION: The tympanic membrane history reflects key stages in medical knowledge; limited for centuries, a great technological leap was possible in the nineteenth century, contributing to the emergence of otologists and laying the foundations of modern otology.

A narrow ear canal reduces sound velocity to create additional acoustic inputs in a microscale insect ear.

Located in the forelegs, katydid ears are unique among arthropods in having outer, middle, and inner components, analogous to the mammalian ear. Unlike mammals, sound is received externally via two tympanic membranes in each ear and internally via a narrow ear canal (EC) derived from the respiratory tracheal system. Inside the EC, sound travels slower than in free air, causing temporal and pressure differences between external and internal inputs. The delay was suspected to arise as a consequence of the narrowing EC geometry. If true, a reduction in sound velocity should persist independently of the gas composition in the EC (e.g., air, [Formula: see text]). Integrating laser Doppler vibrometry, microcomputed tomography, and numerical analysis on precise three-dimensional geometries of each experimental animal EC, we demonstrate that the narrowing radius of the EC is the main factor reducing sound velocity. Both experimental and numerical data also show that sound velocity is reduced further when excess [Formula: see text] fills the EC. Likewise, the EC bifurcates at the tympanal level (one branch for each tympanic membrane), creating two additional narrow internal sound paths and imposing different sound velocities for each tympanic membrane. Therefore, external and internal inputs total to four sound paths for each ear (only one for the human ear). Research paths and implication of findings in avian directional hearing are discussed.

Evaluation of the relationship of chronic otitis media with the Körner's septum, auditory tube angle, and tubotympanic angle.

PURPOSE: This study aimed to evaluate the relationships between chronic otitis media (COM) and the characteristics of Auditory tube (Eustachian) angle (ATa), tubotympanic angle (TTa), and Körner's septum (KS). METHODS: A retrospective research was conducted between January 2019 and October 2019. The computed tomography (CT) results and medical files of 210 patients were evaluated. According to CT results and medical files, the patients were evaluated regarding the presence of COM, KS, ATa, and TTa. RESULTS: There were 113 (53.81%) males and 97 (46.19%) females in the study group, and the mean age of the patients was 42.05 ± 10.77 years. The frequency of the KS was significantly higher in patients who were diagnosed with COM (35.66% vs. 7.41%, p < 0.001). The patients diagnosed with COM were found to have a narrower ATa and a wider TTa than the patients who were not diagnosed with COM. ATa was narrower and TTa was wider in patients with KS. The presence of KS and higher TTa value were considered as risk factors for COM (p < 0.001, p < 0.001, respectively) CONCLUSION:  Our findings indicate that ATa was narrower, TTa was wider and KS was more frequent in patients with COM. Analysis of risk factors demonstrated that increased TTa and the presence of KS were associated with increased risk for COM.

Intraspecies variation in ectotympanic tube length and orientation among humans.

Ectotympanic bone morphology is commonly used as a large-scale phylogenetic indicator across primates. Less well-understood is the intraspecies variation in this characteristic and the dynamic ways in which it affects and is affected by overall basicranial shape. This study attempts to clarify relationships between the external ear canal and basicranial shape among humans in a sample of archaeological human crania. The ectotympanic length and orientation were hypothesized to correlate with the shape of the cranial base and particularly with shape variables associated with relative brachycephaly. Basicranial shape in 80 computed tomography (CT) scans of adult humans were quantified using landmark coordinate data, with particular emphasis on the cranial base and auditory structures. Scaled ectotympanic lengths were taken from interlandmark distances and then compared to shape variation of the whole basicranium as summarized by procrustes shape variables and principal components analysis (PCA). The length of the ectotympanic bone was correlated with total cranial base variation. Long ectotympanic bones were found to be associated with brachycephalic individuals and less flexed basicrania. Additionally, long ectotympanic bones were found to be more horizontally oriented, as opposed to inferiorly sloped. We suggest that as brachycephaly increases the distance between the otic capsule and the pinna, the ectotympanic bone lengthens in response.

Comparison of fetal and adult tympanic membrane sizes: a cadaveric study.

OBJECTIVE: The work aimed to compare fetal and adult tympanic membrane (TM) sizes for understanding dimensional development from intrauterine life to adulthood. METHODS: Fifty-six temporal bones (18 fetuses, 10 elderly adults, half male and half female in each group) were included in this study. Using a digital image software, the TM height, width and area were measured. RESULTS: The mean area, height and width of the TM in adults were found as 58.84 ± 22.01 mm2, 9.06 ± 1.33 mm, and 8.10 ± 1.43 mm, respectively. Moreover, the mean area, height and width of the TM in fetuses were measured as 47.62 ± 12.57 mm2, 8.22 ± 1.12 mm, and 7.25 ± 1.15 mm, respectively. The TM dimensions were increasing in fetuses between 20-32 weeks of gestation. However, the TM dimension was statistically similar at the 7th month, the 8th month and adult periods. The TM height was greater than its width in fetuses and adults. CONCLUSION: The calculated regression equations of the TM parameters in fetuses may be used to estimate its size. The TM size did not change from the 7th gestational month, and thus the membrane reached adult diameter in fetal life. The TM height and width showed a very wide range; therefore, we thought that the 12 mm (the height) × 10 mm (the width) graft might be ideal dimension during the repair of the TM perforations.

Sexual dimorphism in external morphology of the American bullfrog Rana (Aquarana) catesbeiana and the possibility of sex determination based on tympanic membrane/eye size ratio.

The American bullfrog Rana (Aquarana) catesbeiana has been reported to show significant sexual dimorphism based on the size ratio between the tympanic membrane and the eye. In males the tympanic membrane is much larger than the eye, but not in females. The ratio has been used as a convenient criterion to discriminate sexes (sexing) in the American bullfrog, though its reliability is unknown. In this study, we examined 86 adult American bullfrogs to clarify whether the tympanic membrane long diameter/eye long diameter (Dtm/De) ratio is a reliable index to discriminate sexes in this species. In addition, we examined the growth of this sexually dimorphic trait. Results indicated that there is a significant difference but there is a small overlap in this ratio Dtm/De between sexes. The allometric comparisons showed the sexual dimorphism of the Dtm/De ratio was increased during growth and the dimorphism is attributable to the difference in the growth rate of the tympanic membrane (Dtm). Therefore, sex determination of American bullfrogs cannot be wholly reliably achieved by the Dtm/De ratio alone; other external morphological features are required in addition.

Artificial intelligence to detect tympanic membrane perforations.

OBJECTIVE: To explore the feasibility of constructing a proof-of-concept artificial intelligence algorithm to detect tympanic membrane perforations, for future application in under-resourced rural settings. METHODS: A retrospective review was conducted of otoscopic images analysed using transfer learning with Google's Inception-V3 convolutional neural network architecture. The 'gold standard' 'ground truth' was defined by otolaryngologists. Perforation size was categorised as less than one-third (small), one-third to two-thirds (medium), or more than two-thirds (large) of the total tympanic membrane diameter. RESULTS: A total of 233 tympanic membrane images were used (183 for training, 50 for testing). The algorithm correctly identified intact and perforated tympanic membranes (overall accuracy = 76.0 per cent, 95 per cent confidence interval = 62.1-86.0 per cent); the area under the curve was 0.867 (95 per cent confidence interval = 0.771-0.963). CONCLUSION: A proof-of-concept image-classification artificial intelligence algorithm can be used to detect tympanic membrane perforations and, with further development, may prove to be a valuable tool for ear disease screening. Future endeavours are warranted to develop a point-of-care tool for healthcare workers in areas distant from otolaryngology.

Tympanoplasty: factors associated with anatomical and audiometric results. / Timpanoplastias: factores asociados al resultado anatómico y auditivo.

INTRODUCTION: Tympanoplasty is a frequent surgery in otolaryngology. Its main indication is tympanic perforation, followed by adhesive otopathy. Its main and (or) anatomic objective is to restore the tympanic membrane's integrity, preventing infections, and its secondary or audiometric objective is to preserve or improve hearing. MATERIAL AND METHOD: Retrospective study of all patients submitted to tympanoplasty at our hospital. Biodemographic, ear pathology and surgery characteristics were registered, and anatomic and audiometric success rates were analyzed. RESULTS: A total of 182 patients were included, most female (57.1%), with average age of 36.1 years. The main surgical indication was tympanic perforation (89.0%), followed by adhesive otopathy (7.1%). Most tympanoplasties were primary surgeries (84.1%), type I (62.6%), performed by endoaural approach (83.5%) using medial or Austin technique (90.1%). Compound cartilage-perichondrium grafts were most frequently used (87.9%). The anatomic success rate was 84.6%, and the audiometric success rate was 66.8%. Patients who underwent myringoplasty (without raising of tympanomeatal flap) presented a better audiometric result (p=.003). No factors associated with better anatomical results were identified. CONCLUSIONS: Our anatomic and audiometric results are comparable to those previously published. Further prospective studies are required to define factors associated with improved anatomic and audiometric results.

Bilateral same-day endoscopic tympanoplasty.

PURPOSE: Although bilateral same-day tympanoplasty is a faster and more comfortable procedure for patients, it is rarely performed due to its theoretical risks. The present study aims to evaluate the results of patients who underwent bilateral same-day endoscopic tympanoplasty. MATERIALS AND METHODS: In this study, 26 patients and 52 ears were evaluated. Postoperative anatomic success rate, pre- and postoperative hearing test results, hearing gains and postoperative complications were recorded. RESULTS: Postoperative anatomic success rate was 92.3% (48/52). Audiological tests revealed the preoperative air-bone gap (ABG) as 19.1 ± 8.8 (7-35) dB and postoperative ABG as 9.8 ± 5.7 (5-25) dB. Postoperative ABG decreased significantly (p: <0.001) and 9.2 ± 4.6 (2-23) dB hearing gain was obtained. We did not observe any significant complications. CONCLUSION: Bilateral same-day endoscopic tympanoplasty is a feasible surgical procedure with good anatomic and functional outcomes, low complication rate and good postoperative patient comfort.

Endoscopic evaluation of middle ear anatomic variations in autopsy series: analyses of 204 ears / Avaliação endoscópica das variações anatômicas da orelha média em uma série de autópsias: análise de 204 orelhas

Abstract Introduction Microsurgery of the ear requires complete evaluation of middle ear surgical anatomy, especially the posterior tympanic cavity anatomy. Preoperative assessment of the middle ear cavity is limited by the permeability of eardrum and temporal bone density. Therefore, middle ear exploration is an extremely useful method to identify structural abnormalities and anatomical variations. Objective The aim of this study is to determine anatomic variations of the middle ear in an autopsy series. Methods All evaluations were performed in the Forensic Medicine Institute Morgue Department. The cases over 18 years of age, with no temporal bone trauma and history of otologic surgery included in this study. Results One hundred and two cadavers were included in the study. The mean age was 49.08 ± 17.76 years. Anterior wall prominence of the external auditory canal was present in 27 of all cadavers (26.4%). The tympanic membrane was normal in 192 ears (94%) while several eardrum pathologies were detected in 12 ears (6%). Agenesis of the pyramidal eminence and stapedial tendon was found in 3 ears. While the ponticulus was bony ridge-shaped in 156 of 204 ears (76.4%), it was bridge-shaped in 25 ears (12.3%). The ponticulus was absent in 23 ears (11.3%). While complete subiculum was present in 136 of all ears (66.7%), incomplete subiculum was present in 21 ears (10.3%). Subiculum was absent in 47 ears (23%). Facial dehiscence was found in 32 ears and the round window niche was covered by a pseudomembrane in 85 ears (41.6%). A fixed footplate was present in 7.4% of all ears, and no persistent stapedial artery was seen in any cases. Conclusion The pseudomembrane frequency covering the round window niche was found different from reports in the literature. In addition, the frequency of the external auditory canal wall prominence has been reported for the first time.

Resumo Introdução A otomicrocirurgia requer avaliação completa da anatomia cirúrgica da orelha média, especialmente da anatomia da cavidade timpânica posterior. A avaliação pré-operatória da cavidade timpânica é limitada pela permeabilidade do tímpano e densidade do osso temporal. Portanto, a exploração da orelha média é um método extremamente útil para identificar anormalidades estruturais e variações anatômicas. Objetivo Determinar as variações anatômicas da orelha média em uma série de autópsias. Método Todas as avaliações foram realizadas no necrotério do Instituto Médico-Legal. Os casos com mais de 18 anos, sem trauma do osso temporal e história de cirurgia otológica foram incluídos neste estudo. Resultados Cento e dois cadáveres foram incluídos no estudo. A média de idade foi de 49,08 ± 17,76 anos. A proeminência da parede anterior do conduto auditivo externo estava presente em 27 de todos os cadáveres (26,4%). A membrana timpânica era normal em 192 orelhas (94%), enquanto várias alterações do tímpano foram detectadas em 12 orelhas (6%). Agenesia da eminência piramidal e do tendão do estapédio foi encontrada em 3 orelhas. Enquanto o pontículo tinha formato de crista óssea em 156 das 204 orelhas (76,4%), tinha o formato de ponte em 25 orelhas (12,3%). O pontículo estava ausente em 23 orelhas (11,3%). Enquanto o subículo completo estava presente em 136 de todas as orelhas (66,7%), encontrava-se incompleto em 21 orelhas (10,3%). O subículo estava ausente em 47 orelhas (23%). Deiscência facial foi encontrada em 32 orelhas e o nicho da janela redonda estava coberto por uma pseudomembrana em 85 orelhas (41,6%). A platina fixa foi observada em 7,4% de todas as orelhas e a artéria estapediana persistente não foi vista. Conclusão A frequência da pseudomembrana que cobre o nicho da janela redonda foi diferente daquela encontrada na literatura. Além disso, a frequência da proeminência da parede do canal auditivo externo foi relatada pela primeira vez.

How flexibility and eardrum cone shape affect sound conduction in single-ossicle ears: a dynamic model study of the chicken middle ear.

It is believed that non-mammals have poor hearing at high frequencies because the sound-conduction performance of their single-ossicle middle ears declines above a certain frequency. To better understand this behavior, a dynamic three-dimensional finite-element model of the chicken middle ear was constructed. The effect of changing the flexibility of the cartilaginous extracolumella on middle-ear sound conduction was simulated from 0.125 to 8 kHz, and the influence of the outward-bulging cone shape of the eardrum was studied by altering the depth and orientation of the eardrum cone in the model. It was found that extracolumella flexibility increases the middle-ear pressure gain at low frequencies due to an enhancement of eardrum motion, but it decreases the pressure gain at high frequencies as the bony columella becomes more resistant to extracolumella movement. Similar to the inward-pointing cone shape of the mammalian eardrum, it was shown that the outward-pointing cone shape of the chicken eardrum enhances the middle-ear pressure gain compared to a flat eardrum shape. When the outward-pointing eardrum was replaced by an inward-pointing eardrum, the pressure gain decreased slightly over the entire frequency range. This decrease was assigned to an increase in bending behavior of the extracolumella and a reduction in piston-like columella motion in the model with an inward-pointing eardrum. Possibly, the single-ossicle middle ear of birds favors an outward-pointing eardrum over an inward-pointing one as it preserves a straight angle between the columella and extrastapedius and a right angle between the columella and suprastapedius, which provides the optimal transmission.

Endoscopic evaluation of middle ear anatomic variations in autopsy series: analyses of 204 ears.

INTRODUCTION: Microsurgery of the ear requires complete evaluation of middle ear surgical anatomy, especially the posterior tympanic cavity anatomy. Preoperative assessment of the middle ear cavity is limited by the permeability of eardrum and temporal bone density. Therefore, middle ear exploration is an extremely useful method to identify structural abnormalities and anatomical variations. OBJECTIVE: The aim of this study is to determine anatomic variations of the middle ear in an autopsy series. METHODS: All evaluations were performed in the Forensic Medicine Institute Morgue Department. The cases over 18 years of age, with no temporal bone trauma and history of otologic surgery included in this study. RESULTS: One hundred and two cadavers were included in the study. The mean age was 49.08±17.76 years. Anterior wall prominence of the external auditory canal was present in 27 of all cadavers (26.4%). The tympanic membrane was normal in 192 ears (94%) while several eardrum pathologies were detected in 12 ears (6%). Agenesis of the pyramidal eminence and stapedial tendon was found in 3 ears. While the ponticulus was bony ridge-shaped in 156 of 204 ears (76.4%), it was bridge-shaped in 25 ears (12.3%). The ponticulus was absent in 23 ears (11.3%). While complete subiculum was present in 136 of all ears (66.7%), incomplete subiculum was present in 21 ears (10.3%). Subiculum was absent in 47 ears (23%). Facial dehiscence was found in 32 ears and the round window niche was covered by a pseudomembrane in 85 ears (41.6%). A fixed footplate was present in 7.4% of all ears, and no persistent stapedial artery was seen in any cases. CONCLUSION: The pseudomembrane frequency covering the round window niche was found different from reports in the literature. In addition, the frequency of the external auditory canal wall prominence has been reported for the first time.

Imaging anatomy of the retrotympanum: variants and their surgical implications.

The retrotympanic anatomy is complex and variable but has received little attention in the radiological literature. With advances in CT technology and the application of cone beam CT to temporal bone imaging, there is now a detailed depiction of the retrotympanic bony structures.With the increasing use of endoscopes in middle ear surgery, it is important for the radiologist to appreciate the nomenclature of the retrotympanic compartments in order to aid communication with the surgeon. For instance, in the context of cholesteatoma, clear imaging descriptions of retrotympanic variability and pathological involvement are valuable in pre-operative planning.The endoscopic anatomy has recently been described and the variants classified. The retrotympanum is divided into medial and lateral compartments with multiple described potential sinuses separated by bony crests.This pictorial review will describe the complex anatomy and variants of the retrotympanum. We will describe optimum reformatting techniques to demonstrate the structures of the retrotympanum and illustrate the associated anatomical landmarks and variants with CT. The implications of anatomical variants with regards to otologic surgery will be discussed.

Occurrence of tympanic bone spicules and bone crests in domestic cats.

Small and hyperostotic tympanic bone spicules (STBS and HTBS) extending from the tympanic wall or from the septum bullae into the tympanic cavity have been described in large feline species such as Siberian tigers or African lions and in canids such as dogs, red foxes and wolves. Detailed descriptions of prevalence, location and orientation were performed for dogs and African lions by means of necropsy and conventional computed tomography (cCT). Aims of the current study were to describe same characteristics for domestic cats by means of microcomputed tomography (µCT) and cCT. A total of 15 cats or rather 30 ears were examined. Furthermore, new bone formations extending into the tympanic cavity shaped like small lamellae were found and named "tympanic bone crests" (TBCs). The registered phenomenon of a thickened tympanic wall in some cats was named "tympanic wall thickening" (TWT). STBS appeared in 43% of the ears being bilateral in 44% of the cases, whereas HTBS appeared in one ear. TBC was present in 33% of the ears with a bilateral prevalence of 67%, and TWT could be detected in 13% of the ears. The mentioned structures are just barely or not at all detectable with cCT; therefore, µCT is necessary for an identification and detailed description. The origin and the factors inducing the development of examined phenomena are unknown, and it is hypothesized that the occurrence can be assessed as anatomical norm variations.

Topography of vibration frequency responses on the bony tympano-periotic complex of the pilot whale Globicephala macrorhynchus.

In modern Cetacea, the ear bone complex comprises the tympanic and periotic bones forming the tympano-periotic complex (TPC), differing from temporal bone complexes of other mammals in form, construction, position, and possibly function. To elucidate its functioning in sound transmission, we studied the vibration response of 32 pairs of formaldehyde-glutaraldehyde-fixed TPCs of Globicephala macrorhynchus, the short-finned pilot whale (legally obtained in Taiji, Japan). A piezoelectric-crystal-based vibrator was surgically attached to a location on the cochlea near the exit of the acoustic nerve. The crystal delivered vibrational pulses through continuous sweeps from 5 to 50 kHz. The vibration response was measured as a function of frequency by Laser Doppler Vibrometry at five points on the TPC. The aim of the experiment was to clarify how the vibration amplitudes produced by different frequencies are distributed on the TPC. At the lowest frequencies (<12 kHz), no clear differential pattern emerged. At higher frequencies the anterolateral lip of the TP responded most sensitively with the highest displacement amplitudes, and response amplitudes decreased in orderly fashion towards the posterior part of the TPC. We propose that this works as a lever: high-frequency sounds are most sensitively received and cause the largest vibration amplitudes at the anterior part of the TP, driving movements with lower amplitude but greater force near the posteriorly located contact to the ossicular chain, which transmits the movements into the inner ear. Although force (pressure) amplification is not needed for impedance matching in water, it may be useful for driving the stiffly connected ossicles at the high frequencies used in echolocation.

Auditory brainstem responses in the red-eared slider Trachemys scripta elegans (Testudoformes: Emydidae) reveal sexually dimorphic hearing sensitivity.

Hearing sensitivity is of general interest from the perspective of understanding the functionality and evolution of vertebrate auditory systems. Sexual dimorphism of auditory systems has been reported in several species of vertebrates, but little is known about this phenomenon in turtles. Some morphological characteristics, such as middle ear and tympanic membrane that influence the hearing sensitivity of animals can result in hearing sexual dimorphism. To examine whether sexual dimorphism in hearing sensitivity occurs in turtles and to compare hearing characteristics with respect to the shape of the tympanic membrane, we measured the hearing sensitivity and tympanum diameter in both sexes of Trachemys scripta elegans. The results showed that, with the exception of 0.9 kHz, auditory brainstem response thresholds were significantly lower in females than in males for frequencies in the 0.2-1.1 kHz range, indicating that the hearing of females shows greater sensitivity. No significant differences were detected in the tympanum diameter of both sexes. These results showed that sexually dimorphic hearing sensitivity has evolved in turtles; however, this difference does not appear to be related to differences in the size of the tympanic membrane. The possible origin and function of the sexual differences in auditory characteristic are discussed.

Anatomical Study of the Facial Recess with Implications in Round Window Visibility for Cochlear Implantation: Personal Observations and Review of the Literature

Abstract Introduction Posterior tympanotomy through facial recess (FR) is the conventional and most preferred approach to facilitate cochlear implantation, especially when the electrode is inserted through the round window. The complications of the FR approach can be minimized by proper understanding of the anatomy of the FR. Objective The present study was undertaken to assess the various parameters of FR and round window visibility, which may be of relevance for cochlear implant surgery. Methods Thirty-five normal wet human cadaveric temporal bones were studied by dissection for anatomy of FR and posterior tympanum. Photographs were taken with an 18megapixels digital camera, which were then imported to a computer to determine various parameters. Results The mean distance from the take-off point/crotch of the chorda tympani nerve (CTN) to the stylomastoid foramen was 4.08 ± 0.8 mm(range of 2.06 - 5.5mm). The variations in the course of the CTN included origin at the level of the lateral semicircular canal. Themean chorda-facial angle in our study was 26.91° ± 1.19°, with a range of 25° to 28.69°. The mean FR length ranged between 9.4 mm and 18.56 mm (mean of 12.41 ± 2.91mm) and varied with the origin of the CTN and pneumatization of temporal bone. The average maximum width of the FR was 2.93 ± 0.4 mm (range 2.24-3.45 mm) and the mean width of the FR at the level of the round window was 2.65 ± 0.41 mm. Conclusion The FR approach provides good access to the round windowmembrane in all cases. In some cases, table adjustment is required.

Strain distribution in rabbit eardrums under static pressure.

Full-field strain maps of intact rabbit eardrums subjected to static pressures are presented. A stochastic intensity pattern was applied to 12 eardrums, and strain maps were measured at the medial site using a stereoscopic digital image correlation setup for pressures between -2 and 2 kPa. Ear canal overpressures induced circumferential orientated positive strains between manubrium and the eardrum border that increased almost linearly with pressure. Radially orientated negative strains were found at the border and manubrium. Ear canal underpressures caused negative circumferential strains between manubrium and the tympanic annulus but radially orientated positive strains at the borders. The magnitudes of these negative strains at underpressures were larger than those of positive strains at overpressures and were nonlinearly proportional to pressure. In three ears, strains were calculated with intact and removed cochlea. The effect of cochlea removal on the peak-to-peak strain was found to be no more than 3%.