Human Temporal Bone Specimens Research Articles

Relationship Between Cochlear Lateral Wall Changes and Endolymphatic Hydrops in Otitis Media.

Despite otitis media and various disease processes being associated with endolymphatic hydrops (EH), an exact explanation of the pathophysiology has yet to be reported. This study aimed to investigate the changes in the cochlear lateral wall structures and their potential correlation with the presence and severity of cochlear EH in acute and chronic otitis media cases. The investigations were conducted in both chinchilla animal model and human temporal bone specimens. We studied a total of 15 chinchilla and 25 human temporal bones from our collection, which were categorized into acute otitis media, chronic otitis media (COM), and control groups. Through quantitative analysis, we measured the area of cochlear lateral wall structures and observed the presence and the degree of EH using light microscopy. No significant changes were determined in the area of the spiral ligament (p > 0.05) across the species. However, a significant (p < 0.05) decrease in the mean area of the stria vascularis in the basal turn was identified in COM groups compared to controls of both species. Chinchilla model additionally exhibited pathology extending to the lower mid turn. A negative correlation was found between the mean strial area and the severity of EH in both the animal model and human samples. COM associated with significant changes in the stria vascularis that may lead to significant increase in the degree of EH. The presented animal model exhibited parallel findings with human samples, suggesting its viability as a valuable model for future studies. N/A Laryngoscope, 2024.

Development of an Algorithm for Correct Placement of the Basal Electrode Contact in the Context of Anatomy-Based Cochlear Implantation: A Proof of Concept

Plain Language SummaryTonotopic-matched stimulation of the cochlea is important in the context of anatomy-based cochlear implantation. The basal cochlear implant electrode contact is often placed in a frequency range higher than 10 kHz – when a normal insertion depth is reached – and can therefore be difficult to fit since current audio processors only stimulate for frequencies up to 8.5 kHz. This leads to a mismatch of high frequencies. This study represents a proof of concept for a tonotopic correct insertion and aims to develop an algorithm for a placement of the basal electrode below 8.5 kHz in an experimental setting. Therefore, pre- and postoperative CT scans were performed on 10 human temporal bone specimens. Tonotopic information about the aimed position of basal electrode contact was extracted from the imaging dataset by using 3D-curved multiplanar reconstruction and a newly developed mathematical approach. A specially designed cochlear implant electrode array was inserted in all specimens based on the individually calculated insertion depths. Positioning of the basal electrode contact was reached with only a small mean deviation of 37 ± 399 Hz and 0.06 ± 0.37 mm from the planned frequency of 8.25 kHz. In addition, the inserted electrode array adequately covered the apical regions of the cochleae. Using this algorithm, it was possible to position the basal electrode array contact in an area of the cochlea that can be correctly stimulated by the existing speech processors in the context of tonotopic correct fitting.

Numerical Simulations of the Epley Maneuver With Clinical Implications.

Canalith repositioning procedures to treat benign paroxysmal positional vertigo are often applied following standardized criteria, without considering the possible anatomical singularities of the membranous labyrinth for each individual. As a result, certain patients may become refractory to the treatment due to significant deviations from the ideal membranous labyrinth, that was considered when the maneuvers were designed. This study aims to understand the dynamics of the endolymphatic fluid and otoconia, within the membranous labyrinth geometry, which may contribute to the ineffectiveness of the Epley maneuver. Simultaneously, the study seeks to explore methods to avoid or reduce treatment failure. We conducted a study on the Epley maneuver using numerical simulations based on a three-dimensional medical image reconstruction of the human left membranous labyrinth. A high-quality micro-computed tomography of a human temporal bone specimen was utilized for the image reconstruction, and a mathematical model for the endolymphatic fluid was developed and coupled with a spherical particle model representing otoconia inside the fluid. This allowed us to measure the position and time of each particle throughout all the steps of the maneuver, using equations that describe the physics behind benign paroxysmal positional vertigo. Numerical simulations of the standard Epley maneuver applied to this membranous labyrinth model yielded unsatisfactory results, as otoconia do not reach the frontside of the utricle, which in this study is used as the measure of success. The resting times between subsequent steps indicated that longer intervals are required for smaller otoconia. Using different angles of rotation can prevent otoconia from entering the superior semicircular canal or the posterior ampulla. Steps 3, 4, and 5 exhibited a heightened susceptibility to failure, as otoconia could be accidentally displaced into these regions. We demonstrate that modifying the Epley maneuver based on the numerical results obtained in the membranous labyrinth of the human specimen under study can have a significant effect on the success or failure of the treatment. The use of numerical simulations appears to be a useful tool for future canalith repositioning procedures that aim to personalize the treatment by modifying the rotation planes currently defined as the standard criteria.

Pull-Out Strength of Orthodontic Miniscrews in the Temporal Bone.

Minimally invasive cochlear implant surgery by using a microstereotactic frame demands solid connection to the bone. We aimed to determine the stability of commercially available orthodontic miniscrews to evaluate their feasibility for frame's fixation. In addition, which substitute material most closely resembles the mechanical properties of the human temporal bone was evaluated. Pull-out tests were carried out with five different types of orthodontic miniscrews in human temporal bone specimens. Furthermore, short fiber filled epoxy (SFFE), solid rigid polyurethane (SRPU50), bovine femur, and porcine iliac bone were evaluated as substitute materials. In total, 57 tests in human specimens and 180 tests in the substitute materials were performed. In human temporal bone, average pull-out forces ranged from 220 N to 285 N between screws. Joint stiffness in human temporal bone ranged between 14 N/mm and 358 N/mm. Statistically significant differences between the tested screws were measured in terms of stiffness and elastic energy. One screw type failed insertion due to tip breakage. No significant differences occurred between screws in maximum pull-out force. The average pull-out values of SFFE were 14.1 N higher compared to human specimen. Orthodontic miniscrews provided rigid fixation when partially inserted in human temporal bone, as evidenced by pull-out forces and joint stiffness. Average values exceeded requirements despite variations between screws. Differences in stiffness and elastic energy indicate screw-specific interface mechanics. With proper insertion, orthodontic miniscrews appear suitable for microstereotactic frame anchoring during minimally invasive cochlear implant surgery. However, testing under more complex loading is needed to better predict clinical performance. For further pull-out tests, the most suitable substitute material is SFFE.

Emerging Mechanisms in the Pathogenesis of Menière's Disease: Evidence for the Involvement of Ion Homeostatic or Blood-Labyrinthine Barrier Dysfunction in Human Temporal Bones.

Analysis of human temporal bone specimens of patients with Menière's disease (MD) may demonstrate altered expression of gene products related to barrier formation and ionic homeostasis within cochlear structures compared with control specimens. MD represents a challenging otologic disorder for investigation. Despite attempts to define the pathogenesis of MD, there remain many gaps in our understanding, including differences in protein expression within the inner ear. Understanding these changes may facilitate the identification of more targeted therapies for MD. Human temporal bones from patients with MD (n = 8) and age-matched control patients (n = 8) were processed with immunohistochemistry stains to detect known protein expression related to ionic homeostasis and barrier function in the cochlea, including CLDN11, CLU, KCNJ10, and SLC12A2. Immunofluorescence intensity analysis was performed to quantify protein expression in the stria vascularis, organ of Corti, and spiral ganglion neuron (SGN). Expression of KCNJ10 was significantly reduced in all cochlear regions, including the stria vascularis (9.23 vs 17.52, p = 0.011), OC (14.93 vs 29.16, p = 0.014), and SGN (7.69 vs 18.85, p = 0.0048) in human temporal bone specimens from patients with MD compared with control, respectively. CLDN11 (7.40 vs 10.88, p = 0.049) and CLU (7.80 vs 17.51, p = 0.0051) expression was significantly reduced in the SGN. The results of this study support that there may be differences in the expression of proteins related to ionic homeostasis and barrier function within the cochlea, potentially supporting the role of targeted therapies to treat MD.

Temporal bone phantom for decoupled cochlear implant electrode insertion force measurement

Abstract In research on cochlear implants, preclinical testing of newly developed electrode arrays and surgical tools is an essential procedure, which requires the availability of a suitable testing environment. For this purpose, human temporal bone specimens are most realistic, but their availability is limited and additional parameters such as insertion forces are hardly measurable. Therefore, the aim of this study was to develop a temporal bone phantom with realistic anatomical structures for intracochlear force measurement. The temporal bone was segmented from CBCT data of a human cadaver head. The segmented model was 3D printed with an additional artificial skin layer to enable the simulated use of surgical instruments such as a self-retaining retractor. A mechanically decoupled artificial cochlear model was realistically positioned within the temporal bone and was furthermore attached to a force sensor. The usability of the phantom was evaluated by performing automated EA insertions using an automated hydraulic insertion device. The experiments showed that the insertion forces within the cochlea could be measured without interferences from surrounding structures. Moreover, the artificial skin provided a rigid interface for the insertion tool. The new phantom is a realistic testing and training platform for cochlear implant electrode insertions with the advantage of measureable insertion forces.

Morphometric Analysis and Linear Measurements of the Scala Tympani and Implications in Cochlear Implant Electrodes.

The objective of this study was to perform detailed height and cross-sectional area measurements of the scala tympani in histologic sections of nondiseased human temporal bones and correlate them with cochlear implant electrode dimensions. Previous investigations in scala tympani dimensions have used microcomputed tomography or casting modalities, which cannot be correlated directly with microanatomy visible on histologic specimens. Three-dimensional reconstructions of 10 archival human temporal bone specimens with no history of middle or inner ear disease were generated using hematoxylin and eosin histopathologic slides. At 90-degree intervals, the heights of the scala tympani at lateral wall, midscala, and perimodiolar locations were measured, along with cross-sectional area. The vertical height of the scala tympani at its lateral wall significantly decreased from 1.28 to 0.88 mm from 0 to 180 degrees, and the perimodiolar height decreased from 1.20 to 0.85 mm. The cross-sectional area decreased from 2.29 (standard deviation, 0.60) mm 2 to 1.38 (standard deviation, 0.13) mm 2 from 0 to 180 degrees ( p = 0.001). After 360 degrees, the scala tympani shape transitioned from an ovoid to triangular shape, corresponding with a significantly decreased lateral height relative to perimodiolar height. Wide variability was observed among the cochlear implant electrode sizes relative to scala tympani measurements. The present study is the first to conduct detailed measurements of heights and cross-sectional area of the scala tympani and the first to statistically characterize the change in its shape after the basal turn. These measurements have important implications in understanding locations of intracochlear trauma during insertion and electrode design.

Methods and reference data for middle ear transfer functions

Human temporal bone specimens are used in experiments measuring the sound transfer of the middle ear, which is the standard method used in the development of active and passive middle ear implants. Statistical analyses of these experiments usually require that the TB samples are representative of the population of non-pathological middle ears. Specifically, this means that the specimens must be mechanically well-characterized. We present an in-depth statistical analysis of 478 data sets of middle ear transfer functions (METFs) from different laboratories. The data sets are preprocessed and various contributions to the variance of the data are evaluated. We then derive a statistical range as a reference against which individual METF measurements may be validated. The range is calculated as the two-sided 95% tolerance interval at audiological frequencies. In addition, the mean and 95% confidence interval of the mean are given as references for assessing the validity of a sample group. Finally, we provide a suggested procedure for measuring METFs using the methods described herein.

Computed Tomography Density as a Bio-marker for Histologic Grade of Otosclerosis: A Human Temporal Bone Pathology Study.

Computed tomography (CT) density measurement can be used to objectively distinguish otosclerosis from normal bone and to determine histologic grades of otosclerosis. Otosclerosis can be seen on CT as subtle radiolucent areas. An objective radiologic measurement that corresponds to known otosclerosis pathology may improve diagnostic accuracy, and could be used as a radiologic biomarker for otosclerosis grade. A blinded, randomized evaluation of both histologic grade on histopathology slides and CT density measurement was performed on 78 human temporal bone specimens (31 with otosclerosis and 47 controls) that had undergone high-resolution multi-detector CT before histologic processing. Assessments were performed at 11 regions of interest (ROIs) in the otic capsule for each specimen. The CT density measurement mean (Hounsfield Units) ± standard deviation for all ROIs (Nos. 1-9) was 2245 ± 854 for grade 0 (no otosclerosis, n = 711), 1896 ± 317 for grade 1 (inactive otosclerosis, n = 109), and 1632 ± 255 for grades 2 and 3 combined (mixed/active otosclerosis, n 35). There was a strong inverse correlation of CT density to histologic grade at ROIs Nos. 1-5 (ANOVA, p < 0.0001). The inter-rater reliability for CT density was very good (correlation coefficient 0.87, p < 0.05). ROC curves suggested a cut-off of 2,150HU to distinguish otosclerosis from normal bone, and 1,811HU to distinguish low grade from mixed/high grade otosclerosis. In human temporal bone specimens, CT density may be used to distinguish normal bone from bone involved by otosclerosis. A higher histologic grade (i.e., indicating a more active otosclerotic focus) correlated with lower density.

Vibration of Tympanic Membrane Influenced by Middle Ear Fluid.

The amount and viscosity of middle ear fluid probably influences the vibration function of the tympanic membrane (TM). There has been much research into the mechanisms of hearing loss resulting from middle ear fluid in the previous study. However, further study is required to understand how the middle ear fluid affects the vibration function of the TM. Tests on a TM in a fresh cadaveric human temporal bone specimen under different simulated conditions were carried out. Saline (1 cSt) and silicone oil (100 cSt, 1 000 cSt, 12 500 cSt) were used to simulate middle ear fluid. The fluid approximately contacted 50% or 100% of TM, which was proportional to the fluid amount. Induced by stimulus signal with frequency domain from 0.25 to 8 kHz, the vibration at 6 points of the TM was measured by laser Doppler vibrometer (LDV), respectively. Data acquisition and processing were accomplished by self-developed software. With the increase of the fluid amount, the magnitude of velocity transfer function reduced across all frequencies. The effect of fluid viscosity on the TM vibration varied and reduced in a complicated way when the fluid viscosity changed. Increasing fluid amount will significantly reduce the TM movement. The effect of fluid viscosity on the TM vibration was nonlinear and related to the fluid amount. The vibration at each point on the TM is frequency-dependent.

Transeustachian Middle Ear Endoscopy Using a Steerable Distal-Camera Tipped Endoscope.

Demonstrate the ability of a novel steerable distal chip endoscope to traverse the Eustachian tube and provide diagnostic quality images of the human middle ear. Three cadaveric temporal bone specimens were used in this work. Diagnostic transeustachian endoscopy of the middle ear was performed. Diagnostic image quality. A novel 1.62 mm steerable endoscope successfully cannulated the Eustachian tube of three human cadaveric temporal bone specimens to reveal intact middle ear anatomy with high optical clarity. A steerable endoscope can be designed to traverse the human Eustachian tube and provide diagnostic quality images of middle ear anatomy.

Three dimensional printing of a low-cost middle-ear training model for surgical management of otosclerosis.

BackgroundSurgical management of otosclerosis is technically challenging with studies demonstrating that outcomes are commensurate with surgical experience. Moreover, experts apply less force on the ossicular chain during prosthesis placement than their novice counterparts. Given the predicted decreasing patient pool and the rising cost of human temporal bone specimens it has become more challenging for trainees to receive adequate intraoperative or laboratory‐based experience in this procedure. As such, there is a need for a low‐cost training model for the procedure. Here we describe such a model.MethodsA surgical model of the middle ear was designed using computer aided design (CAD) software. The model consists of four components, the superior three dimensional (3D)‐printed component representing the external auditory canal, a 90° torsion spring representing the incus, a 3D‐printed base with a stapedotomy underlying the torsion spring, and a 3D‐printed phone holder to facilitate video‐recording of trials and subsequent calculation of the force applied on the modeled incus. Force applied on the incus is calculated based on Hooke's Law from post‐trial computer‐vision analysis of recorded video following experimental determination of the spring constant of the modeled incus.ResultsThe described model was manufactured with a total cost of $56.50. The spring constant was experimentally determined to be 97.0 mN mm/deg, resulting in an ability to detect force applied to the modeled incus across a range of 1.2 to 5200 mN.ConclusionsWe have created a low‐cost middle‐ear training model with measurable objective performance outcomes. The range of detectable force exceeds expected values for the task.Level of Evidence: IV.

Aeration of the Human Prussak's Space: A 3D Synchrotron Imaging Study.

Prussak's space (PS) is an intricate middle ear region which may play an essential role in the development of middle ear disease. The three-dimensional (3D) anatomy of the human PS and its drainage routes remain relatively unknown. Earlier studies have histologically analyzed PS, by micro-dissection and endoscopy. Here, we used synchrotron-radiation phase-contrast imaging (SR-PCI), 3D reconstructions, and modeling to study the framework of the human PS, including aeration pathways. It may lead to increased understanding of development of middle ear pathology. Nine human temporal bone specimens underwent in-line SR-PCI at the Canadian Light Source in Saskatoon, Saskatchewan, Canada. Data were processed with volume-rendering software to create 3D reconstructions using scalar opacity mapping and segmentations to visualize its walls in fixed, undecalcified human temporal bones. The PS was found to be an irregular, variably shaped chamber with different aeration systems. Three different drainage pathways were found: 1) via the posterior malleolar pouch of von Tröltsch in seven of nine ears; 2) directly posterior-inferior into the mesotympanum medial to the posterior malleolar pouch in one ear; and 3) anteriorly in another. The posterior-inferior communications depended on the anatomy of the posterior malleolar fold. In one bilateral case, the aeration differed between the ears. Earlier descriptions of upper ventilation routes between the PS and the epitympanic spaces could not be substantiated. The 3D anatomy of the membrane folds organizing the PS in humans was demonstrated for the first time using in-line SR-PCI. The PS was always aerated into the mesotympanum, suggesting its relative independence of attic ventilation. The impact of its various drainage routes on middle ear ventilation and disease were discussed.

Insertion trauma of a new cochlear implant electrode: evaluated by histology in fresh human temporal bone specimens

Background Combining acoustic and electrical stimulation has been successfully used in patients with low-frequency residual hearing. Electrode insertion trauma, such as electrode translocation could result in loss of residual hearing. Objectives The aim of the study is to evaluate the LCI-20PI electrode array insertion trauma to the intra-cochlear structures in fresh human temporal bone specimens. Materials and methods The LCI-20PI electrode arrays were inserted into scalae tympani through round window membrane in 10 cochleae from ten fresh human cadavers. The intracochlear trauma was evaluated histologically by a scale of 0–4: 0 – no observable trauma, 1 – elevation of basilar membrane, 2 – rupture of basilar membrane or spiral ligament, 3–dislocation into scala vestibuli and 4 – fracture of modiolus or osseous spiral lamina. The insertion depth was measured by radiography. Results Histological results revealed no observable trauma in seven specimens; basal membrane elevation and rupture in two specimens; the electrode array misled into scala vestibuli in one specimen. The insertion depth varied from 228° to 288°. Conclusions and significance The insertion of the LCI-20PI electrode arrays caused no trauma in the majority of the fresh temporal bone specimens. No translocation of the electrode arrays from the scala tympani to the scala vestibuli was observed.

Automatic segmentation of inner ear on CT-scan using auto-context convolutional neural network

Temporal bone CT-scan is a prerequisite in most surgical procedures concerning the ear such as cochlear implants. The 3D vision of inner ear structures is crucial for diagnostic and surgical preplanning purposes. Since clinical CT-scans are acquired at relatively low resolutions, improved performance can be achieved by registering patient-specific CT images to a high-resolution inner ear model built from accurate 3D segmentations based on micro-CT of human temporal bone specimens. This paper presents a framework based on convolutional neural network for human inner ear segmentation from micro-CT images which can be used to build such a model from an extensive database. The proposed approach employs an auto-context based cascaded 2D U-net architecture with 3D connected component refinement to segment the cochlear scalae, semicircular canals, and the vestibule. The system was formulated on a data set composed of 17 micro-CT from public Hear-EU dataset. A Dice coefficient of 0.90 and Hausdorff distance of 0.74 mm were obtained. The system yielded precise and fast automatic inner-ear segmentations.

Access to the Apical Cochlear Modiolus for Possible Stem Cell-based and Gene Therapy of the Auditory Nerve.

Loss of spiral ganglion neurons (SGN) is permanent and responsible for a substantial number of patients suffering from hearing impairment. It can derive from the degeneration of SGNs due to the death of sensory hair cells as well as from auditory neuropathy. Utilizing stem cells to recover lost SGNs increasingly emerges as a possible therapeutic option, but access to human SGNs is difficult due to their protected location within the bony impacted cochlea. Aim of this study was to establish a reliable and practicable approach to access SGNs in the human temporal bone for possible stem cell and gene therapies. In seven human temporal bone specimen a transcanal approach was used to carefully drill a cochleostomy in the lateral second turn followed by insertion of a tungsten needle into the apical modiolus to indicate the spot for intramodiolar injections. Subsequent cone beam computed tomography (CBCT) served as evaluation for positioning of the marker and cochleostomy size. The apical modiolus could be exposed in all cases by a cochleostomy (1.6 mm2, standard deviation ±0.23 mm2) in the lateral second turn. 3D reconstructions and analysis of CBCT revealed reliable positioning of the marker in the apical modiolus, deviating on average 0.9 mm (standard deviation ±0.49 mm) from the targeted center of the second cochlear turn. We established a reliable, minimally invasive, transcanal surgical approach to the apical cochlear modiolus in the human temporal bone in foresight to stem cell-based and gene therapy of the auditory nerve.

Characterizing the size of the target region for atraumatic opening of the cochlea through the facial recess

Surgical treatment with a cochlear implant (CI) for hearing rehabilitation requires a highly accurate and personalized opening of the inner ear (cochlea) to protect the delicate intra-cochlear fine structures, whose functional integrity needs to be maintained to preserve residual hearing. Spatial orientation within the complex anatomy of the lateral skull base during the procedure is a highly demanding task for the surgeon. In order to reduce risk of facial nerve palsy and loss of residual hearing as well as to establish minimally invasive CI surgery (minCIS), image-guided procedures incorporating surgical assistance systems are under development. However, there is a lack of an accuracy threshold value or range that such a system needs to fulfill to be considered sufficiently accurate for atraumatic opening of the inner ear.In this study, high resolution three-dimensional (3D) morphological images of eight human temporal bone specimens were manually segmented to build anatomical models of the human inner ear including all surgically relevant intra-cochlear structures as well as the facial recess. These 3D models were used to plan the surgical access path to the basal turn of the cochlea using the mastoidectomy posterior tympanotomy approach (MPTA). Therefore, custom-made image-processing software was developed to perform both path planning and identification of the valid target region— i.e., the largest possible region for atraumatic opening of the scala tympani.The developed 3D models provide visualization of the complex and variable anatomy of the basal portion of the human cochlear duct (also known as cochlear “hook region”) as well as its spatial relationship to the facial recess. Their spatial arrangement directly impacts the accessibility of the hook region and limits the entry direction into scala tympani. The average diameter of the target region was found to be 1.56 mm ± 0.10 mm (range: 1.43 to 1.72 mm). The anatomic variability and the need for a high safety level of at least 95% for hearing preservation CI surgery lead to a remaining safety margin of approximately 0.3 mm. In the future, this accuracy threshold value can serve as benchmark during the pre-clinical evaluation of image-guidance technologies to allow for highly accurate CI surgery.

Noninvasive Registration Strategies and Advanced Image Guidance Technology for Submillimeter Surgical Navigation Accuracy in the Lateral Skull Base.

Combining novel registration strategies and advanced image guidance technology enable submillimeter accurate and noninvasive navigation for middle ear and lateral skull base surgery. Surgery in the internal auditory canal and the petrous apex present a cognitive and motoric challenge for the surgeon. To date, image guidance rarely assists these procedures, mainly due to the lack of navigation solutions providing submillimeter accuracy associated with low cost in terms of invasiveness, radiation, and time. This study proposes an approach to clinically viable image guidance by using a combination of advanced image guidance technology and noninvasive registration strategies. Based on accuracy-optimized optical tracking hardware (accuracy: 0.05 ± 0.025 mm), 14 novel registration strategies were investigated. In human cadaveric temporal bone specimens n = 36 registration attempts per strategy were conducted. Target registration errors at 10 anatomical targets were measured. The most accurate registration strategies were identified as paired-point-matching using eight landmarks located in the external auditory canal and middle ear and surface matching using combined surfaces of the middle ear, the external auditory canal and the mastoid cortex yielding target registration errors of 0.51 ± 0.28 mm and 0.36 ± 0.13 mm respectively. This study demonstrates submillimeter TREs achieved with noninvasive, anatomy-based registration strategies in combination with advanced image guidance technology. Clinically viable LSB and ME navigation is realized without additional invasiveness, radiation and time associated with artificial fiducials. The appropriate registration strategy can be chosen by the surgeon depending on the pathology and surgical approach.

Quantitative assessment of vestibular otopathology in granulomatosis with polyangitis: A temporal bone study.

ObjectiveTo investigate the temporal bone histopathology of vasculitis, especially in the vestibular organs, in granulomatosis with polyangitis (GPA).MethodsUsing light and differential interference contrast microscopy, we examined 12 human temporal bones from six deceased GPA patients and 12 histopathologically normal human temporal bones from six deceased age‐matched patients.ResultsIn the GPA group, three patients had undergone tympanostomy tube placement. Two of them had suffered mixed hearing loss; one, sensorineural hearing loss; and one, conductive hearing loss. Of the 12 specimens in the GPA group, the granulation tissue invaded the round window niche in seven; cochlear hair cells were not preserved in five. Hemosiderin was deposited in the stria vascularis in eight specimens, in the ampulla or semicircular duct in 10, and in the vestibule in three. The spiral ligament showed severe loss of cellularity in two specimens. In the GPA group, type I vestibular hair cell density was significantly decreased; however, type II vestibular hair cell density did not significantly differ between the GPA group and the control group.ConclusionOur histopathologic findings in human temporal bone specimens of GPA patients delineated changes in the tympanic membrane, middle ear cavity, round window membrane, organ of Corti, stria vascularis, spiral ligament, ampulla, semicircular duct, and vestibule. Type I vestibular hair cell density significantly decreased in the GPA group, as compared with the control group.Level of EvidenceN/A

Histological evaluation of a cochlear implant electrode array with electrically activated shape change for perimodiolar positioning

Abstract For the treatment of deafness or severe hearing loss cochlear implants (CI) are used to stimulate the auditory nerve of the inner ear. In order to produce an electrode array which is both atraumatic and reaches a perimodiolar final position a design featuring shape memory effect was proposed. A Nitinol wire with a diameter of 100 μm was integrated in a state of the art lateral wall electrode array. The wire serves as an actuator after it has been ‘trained’ to adopt the spiral shape of an average human cochlea. Three small diameter platinum-iridium wires (each 20 μm) were crimped to the Nitinol wire in order to produce thermal energy. An insertion test was pursued using a human temporal bone specimen. The prototype electrode array was cooled down by means of immersion in ice water and freeze spray to enable sufficient straightening. Thereafter, insertion into the cochlea through the round window as performed. Insertion was feasible but difficult as premature curling of the electrode occurred during the movement towards the inner ear while passing the middle ear cavity. Therefore, the insertion had to be performed faster than usual. The shape memory actuator was subsequently activated with 450mA current at 5V for 3 seconds. After insertion the specimen was embedded in epoxy resin, microgrinded and all histological slices were assessed for trauma. Perimodiolar position was achieved. No insertion trauma was observed and there were no indications of thermal damage caused by the electrical heating. To the best of our knowledge, this is the first histological evaluation of the insertion trauma caused by an electrically activated shape memory electrode array. These promising results support further research on shape memory CI electrode arrays.