Anatomy Of Ear Research Articles

Comprehensive Review of Inner Ear Anatomy on Photon-Counting CT.

The inner ear contains many fissures and canals that can mimic pathology. Photon-counting CT allows greater spatial and contrast resolution of these structures over traditional energy-integrating CT detectors. Small channels containing nerves, arteries, and normal anatomy such as the cochlear cleft and cochlear and vestibular aqueducts are commonly encountered on temporal bone imaging. The improved visualization of these structures poses challenges for radiologists who are new to photon-counting CT. This article updates the existing temporal bone anatomy literature with a detailed anatomic review of the inner ear and major nerves frequently encountered when reviewing temporal bone imaging.

The specialized inner ear labyrinth of worm-lizards (Amphisbaenia: Squamata).

High-resolution computed tomography (HRCT) has become a widely used tool for studying the inner ear morphology of vertebrates. Amphisbaenians are one of the most specialized groups of fossorial reptiles but are poorly understood relative to other squamate reptile. In this paper we survey the anatomy of the inner and middle ear of these fossorial reptiles using HRCT models and we describe qualitatively and quantitatively (using 3D morphometrics) the anatomy of the inner ear. Amphisbaenians are diverse in skull anatomy, especially in the configuration of the snout, which correlates with digging modes. We demonstrate that the ear also exhibits a diversity of configurations, which are independent of phylogenetic relationships. Results from morphological analyses also allow us to describe 11 new potentially informative phylogenetic characters including some that help to diagnose amphisbaenians, such as: 1) the globular vestibule, ii) semicircular canals arranged in a circular trajectory, and iii) an extensive area of interaction between the columella footplate and the lagenar recess. Among extant amphisbaenians, Rhineura floridana has the most unusual inner ear configuration, including a horizontal semicircular canal that is in the same orientation as the inclined snout. The new morphological information helps us to better understand the morphology of headfirst-burrowing fossorial reptiles and contributes new data for resolution of phylogenetic relationships among amphisbaenians.

Artificial hearing systems based on functional cochlea models

Abstract The cochlea is one of the most complex organs in the human body, exhibiting a complex interplay of characteristics in acoustic, mechanical, electrical, and biological functions. Functional cochlea models are an essential platform for studying hearing mechanics and are crucial for developing next-generation auditory prostheses and artificial hearing systems for sensorineural hearing restoration. Recent advances in additive manufacturing, organ-on-a-chip models, drug delivery platforms, and artificial intelligence have provided valuable insights into how to manufacture artificial cochlea models that more accurately replicate the complex anatomy and physiology of the inner ear. This paper reviews recent advancements in the applications of advanced manufacturing techniques in reproducing the physical, biological, and intelligent functions of the cochlea. It also outlines the current challenges to developing mechanically, electrically, and anatomically accurate functional models of the inner ear. Finally, this review identifies the major requirements and outlook for impactful research in this field going forward. Through interdisciplinary collaboration and innovation, these functional cochlea models are poised to drive significant advancements in hearing treatments, and ultimately enhance the quality of life for individuals with hearing loss.

Improved radiological imaging of congenital aural atresia using flat-panel volume CT.

Precise preoperative radiological evaluation of aural atresia is of utmost importance for surgical planning. Until now, multislice computed tomography (MSCT) has been used but it cannot adequately visualize small structures such as the stapes. Flat-panel volume CT (fpVCT) with its secondary reconstructions (fpVCTSECO) offers ahigh-resolution visualization of the middle ear. New otosurgical planning software also enables detailed 3D reconstruction of the middle ear anatomy. Evaluation of the use of fpVCTSECO in combination with an otosurgical planning software for amore accurate diagnosis and treatment of congenital aural atresia. Sevenpatients with congenital aural atresia underwent preoperative MSCT (600 µm slice thickness) and corresponding fpVCT (466 µm slice thickness). In addition, fpVCTSECO (99 µm slice thickness) were reconstructed. The Jahrsdoerfer and Siegert grading scores were determined and their applicability in the abovementioned imaging modalities was evaluated. In addition, the malleus incus complex was analyzed in 3D rendering. Imaging with fpVCTSECO enabled reliable visualization of the abnormalities, in particular the ossicular chain. Asignificant difference in the Siegert grading score was found. In addition, the malleus-incus complex could be visualized better in 3D. The introduction of new imaging techniques and surgical planning techniques into the diagnostic concept of aural atresia facilitates the identification of malformed anatomy and enables systematic analysis. This combination can also help to more accurately classify the pathology and thus increase the safety and success of the surgical procedure.

Middle Ear Malformations

Middle ear malformations (MEMs) represent a diverse group of congenital anomalies with significant implications for auditory function. These malformations, which occur in approximately 0.5 to 3% of conductive hearing loss cases, can arise from various genetic and environmental factors. They often manifest unilaterally and may occur in isolation or as part of a syndromic condition. MEMs are closely associated with abnormalities of the external ear and less frequently with inner ear anomalies.Embryologically, the middle ear develops from the first and second pharyngeal arches, with interactions between the ectoderm and endoderm contributing to the formation of essential structures such as the tympanic membrane, ossicles and Eustachian tube. Disruptions in these developmental processes can lead to a spectrum of MEMs, ranging from minor defects to severe malformations affecting multiple middle ear components.Clinical management of MEMs requires a multidisciplinary approach, involving otolaryngologists, pediatricians, and audiologists. Early intervention with appropriate hearing aids, including conventional hearing aids and bone conduction devices, is essential to mitigate the impact of conductive hearing loss on speech and language development, particularly in children.Surgical planning involves comprehensive preoperative assessment, including high-resolution computed tomography imaging to evaluate middle ear anatomy, the facial nerve course, and vascular anomalies. Traditional surgical approaches such as stapesplasty and tympanoplasty remain mainstays for correcting specific middle ear defects, while advances in technology have expanded the role of active middle ear implants in treating special cases.In conclusion, MEMs represent a heterogeneous group of congenital anomalies with diverse etiologies and clinical implications. A thorough understanding of their embryological basis, genetic underpinnings, and surgical management strategies is crucial for optimizing outcomes in affected individuals.

First photon-counting detector computed tomography in the living crocodile: a 3D-Imaging study with special reference to amphibious hearing.

Crocodiles are semi-aquatic animals well adapted to hear both on land and under water. Currently, there is limited information on how their amphibious hearing is accomplished. Here, we describe, for the first time, the ear anatomy in the living crocodile using photon-counting detector computed tomography (PCD-CT) and 3D rendering. We speculate on how crocodiles, despite their closed ear canals, can use tympanic hearing in water that also provides directional hearing. A Cuban crocodile (Crocodylus rhombifer) underwent photon-counting detector computed tomography (PCD-CT), under anesthesia and spontaneous respiration. In addition two seven-month-old C. rhombifer and a juvenile Morelet´s crocodile (Crocodylus moreletii) underwent micro-computed tomography (µCT) and endoscopy. One adult Cuviérs dwarf caiman (Paleosuchus palpebrosus) was micro-dissected and video-recorded. Aeration, earflap, and middle ear morphology were evaluated and compared after 3D modeling. PCD-CT and µCT with 3D rendering and segmentation demonstrated the anatomy of the external and middle ears with high resolution in both living and expired crocodiles. Based on the findings and comparative examinations, we suggest that the superior earflap, by modulating the meatal recess together with local bone conduction, may implement tympanic hearing in submerged crocodiles, including directional hearing.

Lessons learned in delayed identification of a misplaced electrode array in the vestibule

To report a case of cochlear implantation with a misplaced electrode array in the vestibule and the causes for the delay in identification. A 23-year-old male with left single-sided deafness underwent cochlear implantation. The intraoperative assessment did not reveal any major red flags of electrode array misplacement. He did not display any vestibular symptoms postoperatively but showed poor speech performance, even though the aided tone audiometry revealed good sound detection thresholds. High-resolution computed tomography (HRCT) showed that the entire perimodiolar electrode array was situated within the vestibule, and a revision surgery was conducted. Retrospective analysis of the neural response telemetry (NRT) revealed subtle differences in responses between the misplaced and correctly placed electrode arrays. Unlike previously reported cases, the patient did not display vestibular symptoms despite the misplacement of the electrode in the vestibule due to existing weakness in otolithic function. Further investigation is warranted when a motivated patient with normal inner ear anatomy does not show benefit with the cochlear implant post-operatively.

A Step-by-Step Surgical Technique to the Posterior Auricular "Revolving Door" Flap for Conchal Tumor Excision: A Guide for the Surgical and Dermatological Trainee.

Skin cancer is the most common malignancy worldwide and the auricle is particularly vulnerable to the effects of cumulative sun exposure. Reconstruction of auricular defects after skin cancer excision remains a vexing surgical challenge owing to the complex three-dimensional- anatomy of the external ear, particularly in the conchal bowl. The postauricular island "revolving door" flap is a reliable single-stage method for reconstructing anterior auricular and conchal defects. While the revolving door flap is well known in the literature, a clear description of how to use the flap to reconstruct an anterior auricular conchal bowl defect is lacking. Herein, we present a step-by-step description of the surgical technique, using surgical photos of a patient who presented with basal cell carcinoma on their anterior auricular concha.

Improved radiological imaging of congenital aural atresia using flat-panel volume CT. German version

Precise preoperative radiological evaluation of aural atresia is of utmost importance for surgical planning. Until now, multislice computed tomography (MSCT) has been used but it cannot adequately visualize small structures such as the stapes. Flat-panel volume CT (fpVCT) with its secondary reconstructions (fpVCTSECO) offers ahigh-resolution visualization of the middle ear. New otosurgical planning software also enables detailed 3D reconstruction of the middle ear anatomy. Evaluation of the use of fpVCTSECO in combination with an otosurgical planning software for amore accurate diagnosis and treatment of congenital aural atresia. Sevenpatients with congenital aural atresia underwent preoperative MSCT (600 µm slice thickness) and corresponding fpVCT (466 µm slice thickness). In addition, fpVCTSECO (99 µm slice thickness) were reconstructed. The Jahrsdoerfer and Siegert grading scores were determined and their applicability in the abovementioned imaging modalities was evaluated. In addition, the malleus incus complex was analyzed in 3D rendering. Imaging with fpVCTSECO enabled reliable visualization of the abnormalities, in particular the ossicular chain. Asignificant difference in the Siegert grading score was found. In addition, the malleus-incus complex could be visualized better in 3D. The introduction of new imaging techniques and surgical planning techniques into the diagnostic concept of aural atresia facilitates the identification of malformed anatomy and enables systematic analysis. This combination can also help to more accurately classify the pathology and thus increase the safety and success of the surgical procedure.

Training and validation of a deep learning U-net architecture general model for automated segmentation of inner ear from CT

BackgroundThe intricate three-dimensional anatomy of the inner ear presents significant challenges in diagnostic procedures and critical surgical interventions. Recent advancements in deep learning (DL), particularly convolutional neural networks (CNN), have shown promise for segmenting specific structures in medical imaging. This study aimed to train and externally validate an open-source U-net DL general model for automated segmentation of the inner ear from computed tomography (CT) scans, using quantitative and qualitative assessments.MethodsIn this multicenter study, we retrospectively collected a dataset of 271 CT scans to train an open-source U-net CNN model. An external set of 70 CT scans was used to evaluate the performance of the trained model. The model’s efficacy was quantitatively assessed using the Dice similarity coefficient (DSC) and qualitatively assessed using a 4-level Likert score. For comparative analysis, manual segmentation served as the reference standard, with assessments made on both training and validation datasets, as well as stratified analysis of normal and pathological subgroups.ResultsThe optimized model yielded a mean DSC of 0.83 and achieved a Likert score of 1 in 42% of the cases, in conjunction with a significantly reduced processing time. Nevertheless, 27% of the patients received an indeterminate Likert score of 4. Overall, the mean DSCs were notably higher in the validation dataset than in the training dataset.ConclusionThis study supports the external validation of an open-source U-net model for the automated segmentation of the inner ear from CT scans.Relevance statementThis study optimized and assessed an open-source general deep learning model for automated segmentation of the inner ear using temporal CT scans, offering perspectives for application in clinical routine. The model weights, study datasets, and baseline model are worldwide accessible.Key PointsA general open-source deep learning model was trained for CT automated inner ear segmentation.The Dice similarity coefficient was 0.83 and a Likert score of 1 was attributed to 42% of automated segmentations.The influence of scanning protocols on the model performances remains to be assessed.Graphical

Which Environmental Pollutants Are Toxic to Our Ears?-Evidence of the Ototoxicity of Common Substances.

Ototoxicity refers to the adverse effects of substances on auditory or vestibular functions. This study examines the evidence of ototoxicity's association with exposure to common environmental pollutants, as documented in toxicological profiles by the Agency for Toxic Substances and Disease Registry. Our aim was to evaluate whether the evidence supports modifying the charting of ototoxic effects in the summary tables of these toxicological profiles and providing a guide for scientists to access these data. Health outcomes of interest included hearing loss, vestibular effects, cochlear lesions, tonal alterations, cellular damage, and ototoxicity-related outcomes (neurological, nephrotoxic, hepatic, and developmental effects). We obtained ototoxicity information for 62 substances. Hearing-related effects were reported, along with neurological effects. Overall, 26 profiles reported strong evidence of ototoxicity, including 13 substances previously designated as ototoxic by other health and safety agencies. Commonly studied outcomes included hearing loss, damage to ear anatomy, and auditory dysfunction. Vestibular dysfunction and tinnitus are rarely studied. Our findings highlight the lack of conclusive evidence of ototoxic properties for many substances, especially for pesticides and herbicides. This review supports charting the evidence of ototoxicity separately in toxicological profiles' summary tables. Improving the communication of ototoxicity-related health effects might impact their recognition and prompt further research. A stronger evidence base could support improved prevention efforts in terms of serious health outcomes.

A postmortem high-resolution MRI study of the development of cochlear nerve-related structures in the second and third trimesters of pregnancy.

Magnetic resonance imaging (MRI) is used to determine whether cochlear nerve development is normal in infants and adults, but it has not yet been used to evaluate cochlear nerve development or measure cochlear nerve-related structures in the fetus. This study sought to provide imaging data for clinical evaluations concerning cochlear nerve development in the fetus using MRI. Postmortem 3.0-Tesla MRI of inner ear was performed in 51 fetuses with normal temporal bones at 25 to 40 weeks of gestation. The continuous scanning protocol incorporated axial three-dimensional (3D) sampling perfection with application-specific contrasts using different flip angle evolution sequences. The images were evaluated to measure the structures of the cochlear aperture (CA), internal auditory canal (IAC), and vestibulocochlear and facial nerves in the cerebellopontine angle (CPA), which have been reported to be associated with cochlear nerve development. We also calculated the ratio between the diameters of the vestibulocochlear and facial nerves. The measurable parameters were compared between the right and left sides. The threshold for statistical significance was set at P<0.05. The inner ear anatomy was discernible on MRI in all the fetal specimens, and growth of the CA, IAC, vestibulocochlear nerve, and facial nerve in the CPA was observed as fetal age increased. There was no significant difference in the measurements of these structures between the right and left sides (all P>0.05). MRI can be used to help evaluate the anatomy and development of the cochlear nerve in the fetus. These normative measurements could be valuable for clinical evaluations of the cochlear nerve.

Speech intelligibility prediction based on a physiological model of the human ear and a hierarchical spiking neural network.

A speech intelligibility (SI) prediction model is proposed that includes an auditory preprocessing component based on the physiological anatomy and activity of the human ear, a hierarchical spiking neural network, and a decision back-end processing based on correlation analysis. The auditory preprocessing component effectively captures advanced physiological details of the auditory system, such as retrograde traveling waves, longitudinal coupling, and cochlear nonlinearity. The ability of the model to predict data from normal-hearing listeners under various additive noise conditions was considered. The predictions closely matched the experimental test data under all conditions. Furthermore, we developed a lumped mass model of a McGee stainless-steel piston with the middle-ear to study the recovery of individuals with otosclerosis. We show that the proposed SI model accurately simulates the effect of middle-ear intervention on SI. Consequently, the model establishes a model-based relationship between objective measures of human ear damage, like distortion product otoacoustic emissions, and speech perception. Moreover, the SI model can serve as a robust tool for optimizing parameters and for preoperative assessment of artificial stimuli, providing a valuable reference for clinical treatments of conductive hearing loss.

Morphometric evaluation of middle ear anatomical structures using full volume (12 × 9) CBCT scans: A retrospective study in Navi Mumbai

Introduction: The tympanic cavity contains three tiny bones, the malleus, incus, and stapes, which have a fundamental role in the transmission of sound. Recent research emphasizes the use of CBCT for the anatomic study of the temporal bone. The information about middle ear anatomy on CBCT scans is meager; hence, this retrospective study was conducted to identify and determine the various morphometrical parameters of the malleus using CBCT which can be helpful during reconstructive procedures for the otologic surgeon. Materials and Methods: The retrospective study was performed on 200 subjects (101 M and 99 F) in the Department of Oral and Maxillofacial Radiology. CBCT images of 200 subjects were studied in all planes to identify ossicular chain and the malleus to investigate the morphometric parameters in Indian Subjects. Result: The average of morphometric parameters shows that the mean length of the malleus is 7.2 mm, the mean width of the head of the malleus is 3.02 mm, length of superior semicircular canal is 4.90 mm, and length of external auditory canal is 19.15 mm in Navi Mumbai population. Conclusion: The obtained morphometric data of the malleus through our study will help the prosthesis maker in the formation of various implants and grafts required to treat various ear diseases.

Barriers to auditory brainstem response testing under anesthesia

ObjectiveAuditory brainstem response (ABR) testing is the gold standard for diagnosis of hearing loss in children who cannot complete behavioral audiometry. Testing under general anesthesia is often recommended when natural sleep ABR and/or behavioral audiometry are unsuccessful. This study aims to determine which demographic and patient factors serve as barriers to receiving this diagnostic testing. MethodsA retrospective chart review from an internal database of patients who underwent ABR testing under anesthesia from 2017 to 2023 was completed. Patient demographics, clinical diagnoses, dates of initial recommendation, and dates of testing were recorded. ResultsA total of 395 patients met inclusion criteria, with a median time from initial evaluation to successful ABR under anesthesia of 5.1 months (range 0.1–209 months). This time was significantly higher in patients with public insurance compared to private insurance and in patients with the following medical complexities: cardiac disease, developmental delay, neurologic disease, eye disease, and genetic syndromes not associated with hearing loss. The interval was significantly shorter in patients with abnormal ear anatomy. ConclusionPatient factors, such as insurance type and certain medical diagnoses, may lead to delayed ABR testing under anesthesia and thus delayed diagnosis and management of hearing loss. This has implications for the timely care and treatment of children with hearing loss.

Educational endoscopic videos improve teaching of middle ear anatomy.

Videos and images are becoming an educational tool in every domain. The objective was to assess the contribution of short educational endoscopic videos in learning the complex anatomy of the tympanic cavity. We conducted a prospective study amongst all the otolaryngology residents in 2021 in the greater Paris area (n = 74), from the first year to fifth year. We divided the residents into two groups who had the same 30-min anatomy class based on anatomical drawings. The second group had a 4-min endoscopic educational video at the end, whereas the first group did not. A video test of 10 surgical situations with each time 5 anatomic structures to identify was created. All the residents took the test just after the class, and 1 month later to assess long-term memory. The MERSQI score (design to assess the quality of educational studies) applied to our study was calculated. The two groups were comparable in terms of training. The "video" group had significantly better results in the first test, mean score 24.40/50 (± 11.7) versus 16.74/50 (± 11.1) (p = 0.005) and also at 1month, mean score 23.25/50 (± 12.3) versus 18.01/50 (± 11.3) (p = 0.035). The score in each group, and the difference between both groups, increased with resident seniority. The MERSQI score of our study was 14.5/18. This study highlights the educational value of videos to help memorise complex 3D anatomy such as in the tympanic cavity.

Corrigendum: Middle ear anatomy and implant sizes: correlates and the need for uniform implant dimensions

Corrigendum: Middle ear anatomy and implant sizes: correlates and the need for uniform implant dimensions

Characterization of PLGA versus PEG-PLGA intracochlear drug delivery implants: Degradation kinetics, morphological changes, and pH alterations

Drug delivery to the inner ear presents a unique challenge due to the complex inner ear anatomy and its tight physiological barriers. This study investigates the degradation behavior of intracochlear drug delivery implants (IDDI) composed of dexamethasone and poly(lactic-co-glycolic acid) (PLGA) or polyethylene glycol–poly(lactic-co-glycolic acid) (PEG-PLGA), respectively. IDDI were incubated in artificial perilymph and implants' degradation kinetics, morphological changes, water uptake behavior, and pH alterations were assessed. Microscopy revealed significant changes in appearance, with PLGA IDDI exhibiting rapid expansion, reaching up to 183 % in diameter and 185 % in length. PEG-PLGA implants showed gradual expansion, reaching a maximum of 178 % in diameter and 144 % in length. Despite these morphological changes, the IDDIs could still be applicable in terms of cochlear dimensions in combination with cochlear implants (CI) in humans or in a domestic pig animal model. Scanning electron microscopy analysis demonstrated surface alterations of PLGA implants, while PEG-PLGA implants remained shape-stable. Gravimetric analysis and gel permeation chromatography revealed distinct degradation profiles, with PLGA implants displaying rapid water uptake and mass loss, while PEG-PLGA implants showed delayed water uptake and minimal mass reduction. pH measurements using the pH-sensitive fluorescent dye SNARF™-1 showed initial pH reduction in artificial perilymph for PLGA implants while PEG-PLGA implants maintained pH stability.

Clinical High-Resolution Imaging of the Inner Ear by Using Magnetic Resonance Imaging (MRI) and Cone Beam Computed Tomography (CBCT).

Imaging of the delicate inner ear morphology has become more and more precise owing to the rapid progress in magnetic resonance imaging (MRI). However, in clinical practice, the interpretation of imaging findings is hampered by a limited knowledge of anatomical details which are frequently obscured by artifacts. Corresponding review articles are as rare in journals as they are in reference books. This shortness prompted us to perform a direct comparison of imaging with anatomical whole-mount sections as a reference. It was the intention of this paper to compare the microscopic anatomy of a human inner ear as shown on anatomical whole-mount sections with high-resolution MRI and cone beam computed tomography (CBCT). Both are available in clinical routine and depict the structures with maximum spatial resolution. It was also a goal of this work to clarify if structures that were observed on MRI in a regular manner correlate with factual inner ear anatomy or correspond with artifacts typical for imaging. A fresh human anatomical specimen was examined on a clinical 3-Tesla MRI scanner using a dedicated surface coil. The same specimen was then studied with CBCT. In each imaging modality, high-resolution 3D data sets which enabled multiplanar reformatting were created. In the second step, anatomical whole-mount sections of the specimen were cut and stained. This process enabled a direct comparison of imaging with anatomical conditions. Clinical MRI was able to depict the inner ear with remarkable anatomical precision. Strongly T2-weighted imaging protocols are exquisitely capable of showing the fluid-filled components of the inner ear. The macular organs, ampullar crests and cochlear aqueduct were clearly visible. Truncation artifacts are prone to be confused with the delicate membrane separating the endolymphatic from the perilymphatic compartment. However, it was not possible to directly depict this borderline. With the maximum resolution of magnetic resonance tomography, commonly used in everyday clinical practice, even the smallest details of the inner ear structures can be reliably displayed. However, it is important to distinguish between truncation artifacts and true anatomical structures. Therefore, this study can be useful as a reference for image analysis.

Considerations for the value of three-dimensional printed (3DP) versus cadaveric specimens for anatomy education.

We enjoyed reading the Brumpt et al. paper, which showed that a three-dimensional printed model (3DPM) of the ear was more effective than conventional cadaveric models for teaching anatomy. We would like to comment on the findings of this exciting study. In this case, the 3DPM of the ear was compared with dried bone models but not with a cadaveric specimen (with all adjacent soft tissues). The better results after the first test of students who used the 3DPMs were probably attributed to the optimized 3D representation of the ear anatomy. Also, the educational outcomes will likely be better if a more complex 3DPM is used, as it permits better visualization of the structures compared to the dried bone specimens. We certainly agree that 3DPMs have a remarkable ability to represent anatomy. Still, their effectiveness has not been proven superior to cadaveric specimens teaching complex anatomy. In conclusion, although we agree that 3DPMs have a high educational potential and can contribute to complex anatomy teaching, those models were not proven significantly more effective than cadaveric specimens in the Brumpt et al. study. The better effectiveness of 3DPMs compared to dried bone specimens (at the first test) does not mean those models are superior to specimens with retained soft tissues. Such cadaveric specimens permit visualization of complex structures and have proven valuable for teaching complex anatomy. Currently, the literature does not support the educational superiority of 3DPMs to those cadaveric specimens.