Inner Ear Research Articles

The Predictive Value of Preoperative Measurements of Cochlear Nerve Diameters From MRT and Postoperative Speech Perception in Adult Patients With Cochlear Implant.

The current study aims to investigate whether objective measurements of the cochlear nerve (CN), derived from preoperative MRI images, correlate with postoperative speech perception in CI patients. Retrospective cohort study. University Medical Center, tertiary academic referral center. Patients undergoing a cochlear implant surgery including MED-EL (Synchrony 2, FLEX electrode series; MED-EL, Innsbruck, Austria) Cochlear (slim straight electrodes; Cochlear Ltd., Sydney, Australia), Advanced Bionics (HiRes Ultra 3D CI, HiFocus SlimJ electrodes; Sonova, Zürich, Switzerland), and Oticon (Neuro Zti EVO; Oticon A/S, Smørum, Denmark) between 2020 and 2023. Preoperative MRI images were utilized to measure the volume of the modiolus (VM), the cross-sectional areas of the CN (ACN), and for normalization, the area of the facial nerve (AFN) and the area of the internal ear canal (AIEC). Postoperative speech perceptions were assessed through word recognition scores (WRS) at several stages following the first fitting (FF) of the CI processor: immediately after FF, 1 month, 3 months, and 6 months after FF. Sixty-eight patients were enrolled in this study. A statistically significant positive correlation between the ratio between ACN and AFN (ACN/AFN) and WRSFF was identified (R = 0.36, p < 0.003). However, this correlation disappeared in subsequent follow-up tests. Moreover, upon grouping patients based on their degree of asymmetrical hearing loss, it was observed that the correlation was primarily driven by patients with moderate to severe asymmetrical hearing loss (AHLm) on the contralateral side (R = 0.62, p = 0.0003). The present results suggest that assessing the size of the CN through MRI has limited predictive utility for postoperative speech perceptions during CI consultations. This limitation seems to be particularly relevant for AHLm patients and is confined to the initial activation period.

Internal ear morphometry in pediatrics: a comparison between neurosensorial hearing loss population and control group

Internal ear morphometry in pediatrics: a comparison between neurosensorial hearing loss population and control group

Effective management of Meniere’s disease through Ayurveda- A case report

Meneirs disease is inner ear disease characterized by episodic vertigo, fluctuating hearing loss and tinnitus. The pathophysiology of the disease is obscure but theories postulated and stated that, due to decreased absorption or increased secretion of endolymphatic fluid in membranous labyrinth of the inner ear leads to pressure increase thus manifests the disease. There is no promising cure to this disease in conventional science only with life style adjustments, low salt diet, diuretics and surgery are used to manage the condition. The present case study patient with meniers disease was successfully managed with ayurveda treatment. A 55yrs old male patient complained of giddiness, reduced hearing and tinnitus since 9months which was hampering his daily activities was treated with panchakarma procedures and internal medicines. The exact meniers disease is not mentioned in samhitas but on the basis of symptoms and dosha predominance it is considered as vata-pitta pradhana tridoshaja vyadhi. As per dosha predominance it is treated with virechana (Purgation), Pratimarsha nasya (nasal medication) and internal medicines with Dhanadhanyadi kashaya, Cap ksheerabala and cap palsineuron, Tab Kamaduga rasa was administered. On functional scale level the stage 5 was reduced to 1 which shows good improvement. Meniers disease may satisfactory be managed with Ayurveda treatment.

A Case Report Demonstrating Preservation of Vestibular Receptor Function after Transcochlear Removal of an Intracochlear Schwannoma with Extension to the Fundus of the Internal Auditory Canal

Preservation of function is an important goal during surgical management of cochleovestibular schwannomas. We here demonstrate the relief of vertigo and the preservation of function of all five vestibular receptors after removal of an intracochlear schwannoma with extension to the fundus of the internal auditory canal. A 61-year-old male with a five-year history of left-sided deafness, tinnitus, vertigo attacks, and an MRI consistent with an intracochlear schwannoma with limited extension through the modiolus to the fundus of the internal auditory canal (IAC) underwent transcanal, transcochlear total tumor removal and—due to a cerebrospinal fluid leak from the fundus of the IAC—revision surgery with lateral petrosectomy and blind sac closure of the external auditory canal. Despite complete removal of the cochlear partition of the inner ear (total cochlectomy), the patient’s vestibular receptors remained functional, and the vertigo symptoms disappeared. These results show that vestibular labyrinthine function may not only be preserved after partial or subtotal cochlectomy but also after complete cochlear removal. This further confirms the vestibular labyrinth’s robustness and encourages surgical management of transmodiolar schwannomas with limited extension to the fundus of the IAC.

The inner ear and stapes of the basal mammaliaform Morganucodon revisited: new information on labyrinth morphology and promontorial vascularization

Abstract Based on high-resolution computed tomography scanning, we provide new insights into the inner ear and stapedial morphology of Morganucodon from the Early Jurassic of St Brides. At the base of mammaliaforms, Morganucodon plays a pivotal role in understanding the sequence of character acquisition from basal cynodonts to mammals, including the detachment of the middle ear and the evolution of high-frequency hearing. Advancements in imaging technology enabled us to revise or newly describe crucial anatomy that was not accessible for the original description of Morganucodon. Based on 37 petrosals, we can confirm that the apex of the cochlear canal is expanded in Morganucodon, suggestive of a lagena macula. A gently raised crest along the abneural margin is reminiscent of (although much shallower than) the secondary lamina base of other Mesozoic mammaliaforms. The venous circum-promontorial plexus, which surrounded the inner ear in several basal mammaliaforms, was connected to the cochlear labyrinth in Morganucodon through numerous openings along the secondary lamina base. Two petrosals contain fragmentary stapes, which differ substantially from previously described isolated stapes attributed to Morganucodon in having peripherally placed crura and an oval and bullate footplate. Based on the revised stapedial morphology, we question the traditional view of an asymmetrical bicrural stapes as the plesiomorphic condition for Mammaliaformes.

The six most frequent peripheral vestibular syndromes

Three forms of peripheral vestibular disorders, each with its typical symptoms and clinical signs, can be differentiated functionally, anatomically and pathophysiologically: 1. inadequate unilateral paroxysmal stimulation or rarely inhibition of the peripheral vestibular system, e. g., BPPV, Menière's disease, vestibular paroxysmia or syndrome of the third mobile windows; 2. acute unilateral vestibulopathy leading to an acute vestibular tone imbalance manifesting as an acute peripheral vestibular syndrome; and 3. loss or impairment of function of the vestibular nerve and/or labyrinth: bilateral vestibulopathy. For all of these diseases, current diagnostic criteria by the Bárány-Society are available with a high clinical and scientific impact, also for clinical trials. The treatment depends on the underlying disease. It basically consists of 5 principles: 1. Explaining the symptoms and signs, pathophysiology, aetiology and treatment options to the patient; this is important for compliance, adherence and persistence. 2. Physical therapy: A) For BPPV specific liberatory maneuvers, depending on canal involved. Posterior canal: The new SémontPLUS maneuver is superior to the regular Sémont and Epley maneuvers; horizontal canal: the modified roll-maneuver; anterior canal the modified Yacovino-maneuver; 3. Symptomatic or causative drug therapy. There is still a deficit of placebo-controlled clinical trials so that the level of evidence for pharmacotherapy is most often low. 4. Surgery, mainly for the syndrome of the third mobile windows. 5. Psychotherapeutic measures for secondary functional dizziness.

Effects of radiotherapy for tumors of the larynx and hypopharynx in hearing levels

The head and neck oncological patients are susceptible, either because of tumor location or the treatments performed, to changes of their ear structures. Due to close proximity of radiation field to the ear, radiotherapy induces short and long-term toxicities to the external, middle and internal ear. The aim of this study was to evaluate the impact of radiotherapy on the inner ear. We conducted a cross-sectional retrospective study of patients with cancer of the larynx and hypopharynx undergoing radiotherapy alone or adjuvant to surgery. The follow-up period was 1 year. Relevant clinical and audiological variables were analyzed. We included 15 patients, mostly males, with a median age of 66 years. Average hearing threshold (AHT) deterioration was found in 13 ears, with a median of 8.1dB. Mean bone conduction threshold at 4000 Hz, air conduction threshold at 8000 Hz at 12 months and the median of the final air conduction threshold at 10,000 Hz was significantly higher than the pre-treatment. A correlation was observed between final AHT and dosage of radiation per fraction. Thus, for each increase of 1 Gy per fraction there was an increase of 22.13 dB in the final AHT. About half of the patients had deterioration of the final AHT, proving, on the one hand, the sensorineural hearing loss associated with radiotherapy, while emphasizing the need to perform long-term follow-up protocols for early auditory rehabilitation of these patients.

Transmembrane Channel-Like (Tmc) Subunits Contribute to Frequency Sensitivity in the Zebrafish Utricle.

Information about dynamic head motion is conveyed by a central "striolar" zone of vestibular hair cells and afferent neurons in the inner ear. How vestibular hair cells are tuned to transduce dynamic stimuli at the molecular level is not well understood. Here we take advantage of the differential expression pattern of tmc1, tmc2a, and tmc2b, which encode channel subunits of the mechanotransduction complex in zebrafish vestibular hair cells. To test the role of various combinations of Tmc subunits in transducing dynamic head movements, we measured reflexive eye movements induced by high-frequency stimuli in single versus double tmc mutants. Wefound that Tmc2a function correlates with the broadest range of frequency sensitivity, whereas Tmc2b mainly contributes to lower-frequency responses. Tmc1, which is largely excluded from the striolar zone, plays a minor role in sensing lower-frequency stimuli. Our study suggests that the Tmc subunits impart functional differences to the mechanotransduction of dynamic stimuli.Significance Statement Information about dynamic head movements is transmitted by sensory receptors, known as hair cells, in the labyrinth of the inner ear. The sensitivity of hair cells to fast or slow movements of the head differs according to cell type. Whether the mechanotransduction complex that converts mechanical stimuli into electrical signals in hair cells participates in conveying frequency information is not clear. Here we find that the transmembrane channel-like 1/2 genes, which encode a central component of the complex, are differentially expressed in the utricle and contribute to frequency sensitivity in zebrafish.

Model Problems on Oscillations of Mechanical and Biological Membranes

Various models of membrane oscillations emerging in the theory of elasticity of mechanical systems, biomechanics of the internal ear of vertebrata, and in the theory of electrical circuits are discussed in the article. The considered oscillations have different natures, but their mathematical models are described using similar initial boundary value problems for the second-order hyperbolic equation with the nontrivial boundary condition. The differential equations in these problems are the same. Thus, for example, the model of voltage distribution in the telegraph line emerges for the one-dimensional equation of oscillations. The model of oscillations of a circular homogeneous solid membrane, a membrane with a hole, and the model of gas oscillations in a sphere and spherical region emerge for the two-dimensional and three-dimensional operators, but take into account the radial symmetry of oscillations. The model problem on membrane oscillation can be considered as the problem on ear drum membrane oscillations. The unified approach to reducing the corresponding problems to the initial boundary value problem with zero boundary conditions is suggested. The technique of formulating the solution in the form of a Fourier series using eigenfunctions of the corresponding Sturm–Liouville problem is described.

Angular Head Velocity Cells within Brainstem Nuclei Projecting to the Head Direction Circuit.

The sense of orientation of an animal is derived from the head direction (HD) system found in several limbic structures and depends on an intact vestibular labyrinth. However, how the vestibular system influences the generation and updating of the HD signal remains poorly understood. Anatomical and lesion studies point toward three key brainstem nuclei as key components for generating the HD signal-nucleus prepositus hypoglossi, supragenual nucleus, and dorsal paragigantocellularis reticular nuclei. Collectively, these nuclei are situated between the vestibular nuclei and the dorsal tegmental and lateral mammillary nuclei, which are thought to serve as the origin of the HD signal. To determine the types of information these brain areas convey to the HD network, we recorded neurons from these regions while female rats actively foraged in a cylindrical enclosure or were restrained and rotated passively. During foraging, a large subset of cells in all three nuclei exhibited activity that correlated with the angular head velocity (AHV) of the rat. Two fundamental types of AHV cells were observed; (1) symmetrical AHV cells increased or decreased their firing with increases in AHV regardless of the direction of rotation, and (2) asymmetrical AHV cells responded differentially to clockwise and counterclockwise head rotations. When rats were passively rotated, some AHV cells remained sensitive to AHV, whereas firing was attenuated in other cells. In addition, a large number of AHV cells were modulated by linear head velocity. These results indicate the types of information conveyed from the vestibular nuclei that are responsible for generating the HD signal.SIGNIFICANCE STATEMENT Extracellular recording of brainstem nuclei (nucleus prepositus hypoglossi, supragenual nucleus, and dorsal paragigantocellularis reticular nucleus) that project to the head direction circuit identified different types of AHV cells while rats freely foraged in a cylindrical environment. The firing of many cells was also modulated by linear velocity. When rats were restrained and passively rotated, some cells remained sensitive to AHV, whereas others had attenuated firing. These brainstem nuclei provide critical information about the rotational movement of the head of the rat in the azimuthal plane.

Vestibulo-ocular Reflex – A Narrative Review

The vestibulo-ocular reflex (VOR) causes movements of the eye that are intended to compensate for head and body movements so that vision remains stable on the retina. VOR helps to stabilize the retinal image by rotating the eyes to compensate for movements of the head. The VOR keeps us steady and balanced even though our eyes and head are continuously moving during the performance of actions. The VORs are driven by signals coming from vestibular labyrinths and use subcortical, short-latency pathways from vestibular afferents to the extraocular motor neurons. The relatively simple neural architecture of these reflexive responses, coupled with their stereotyped but adaptable nature, makes them ideal to understand simple sensorineural transformations. Without VOR, when an individual walks down the street, it is difficult to read signs or even recognize faces. Even an inaccurate VOR can result in a slip of visual image concerning photoreceptors, causing blurring of the images. If the VOR is injured, the retinal slip occurs which causes instability in gaze during rapid head movements. The disruption of the VOR results in oscillopsia and abnormal nystagmus. Oscillopsia causes blurred vision when the head is in motion and objects appear to jiggle and bounce as this object does not fix at one point in the retina. The objective of this review article is to discuss the anatomy of VOR with its bedside examinations, clinical implications, and management of VOR failure.

Finite-element modeling on noise impacts and hearing in marine fauna

Despite increasing interest in the effects of anthropogenic noise on marine fauna, relevant research is limited, particularly in those inaccessible species. Unfortunately, some of these inaccessible species are endangered, such as the little penguins (Eudyptula minor) and Australian sealions (Neophoca cinerea). In this study, we collected freshly deceased bight redfish (Centroberyx gerrardi), little penguins, and Australian sealion for medical computed tomography (CT)/microCT scans. Ear structures were reconstructed based on high-resolution imaging data for the three species. Moreover, 3D finite-element models were built to simulate the sound reception processes and ear responses to the incident planar waves from various directions toward the heads. The received sound pressure levels and motion (e.g., displacement and acceleration) of the internal ear related structures were computed. The data was used to predict the absolute hearing curves of the little penguins and Australian sealions. Our results also indicate that the motion difference plus the geometry of the otoliths plays an important role in the fish otoliths' response to incident sounds from different directions, resulting in different levels of damage to the hair cells. This study may potentially aid researchers in investigating the hearing of some other marine animals.

Isolation and Culture of Primary Cochlear Hair Cells from Neonatal Mice.

Cochlear hair cells are the sensory receptors of the auditory system. These cells are located in the organ of Corti, the sensory organ responsible for hearing, within the osseous labyrinth of the inner ear. Cochlear hair cells consist of two anatomically and functionally distinct types: outer and inner hair cells. Damage to either of them results in hearing loss. Notably, as inner hair cells cannot regenerate, and damage to them is permanent. Hence, in vitro cultivation of primary hair cells is indispensable for investigating the protective or regenerative effects of cochlear hair cells. This study aimed to discover a method for isolating and cultivating mouse hair cells. After manual removal of the cochlear lateral wall, the auditory epithelium was meticulously dissected from the cochlear modiolus under a microscope, incubated in a mixture consisting of 0.25% trypsin-EDTA for 10 min at 37 °C, and gently suspended in culture medium using a 200 µL pipette tip. The cell suspension was passed through a cell filter, the filtrate was centrifuged, and cells were cultured in 24-well plates. Hair cells were identified based on their capacity to express a mechanotransduction complex, myosin-VIIa, which is involved in motor tensions, and via selective labeling of F-actin using phalloidin. Cells reached >90% confluence after 4 d in culture. This method can enhance our understanding of the biological characteristics of in vitro cultured hair cells and demonstrate the efficiency of cochlear hair cell cultures, establishing a solid methodological foundation for further auditory research.

Treating Sensorineural Hearing Loss: Recent Advances in Inner Ear Drug Delivery

Abstract: This review aims to provide historical, present, and future drug deliveries for treating in-ner ear disorders. Systemic delivery, such as antibiotics and steroids for the inner ear, was the basis on which current drug delivery systems and devices have been researched and developed. Re-searchers and clinicians had to develop and deliver drugs locally due to adverse effects caused by drugs systemically. Intratympanic method of antibiotics and steroid delivery has been common; however, newer techniques such as microcatheter implantation, hydrogels, nanoparticles, and intra-cochlear implants are being investigated successfully. Recently advances in microfluidic and mi-crosystems technology have applied medications directly into the inner ear. This technology will also be adopted to deliver gene therapy, RNA interference technology, and stem cell therapy by cli-nicians in the future.

Potential biomarkers in peripheral blood mononuclear cells of patients with sporadic Ménière’s disease based on proteomics

Background Ménière’s disease (MD) mainly refers to the endolymphatic hydrops in membranous labyrinth of the inner ear. Application of the mass spectrometry-based proteomics techniques has not been applied in the field of MD. Objectives To search for potential differential proteins to identify the disease biomarkers and reveal disease bioinformatics-related mechanisms through applying protein technology to analyze the expression changes of peripheral blood mononuclear cells (PBMCs) in sporadic MD patients. Material and Methods 15 MD patients and 15 healthy individuals were enrolled. PBMCs from them were extracted, and their protein expression was identified and compared by LC-MS/MS and spectra analysis. Results There was significant difference in protein expression between MD patients and the control group. GO and KEGG analysis showed that endocytosis was involved in MD patients. Western blot results of CHMP1A and MMP9 protein showed that the expression of CHMP1A was higher in the MD group than that in the control group, while MMP9 was down-regulated. Immunohistochemistry confirmed that CHMP1A and MMP9 were expressed in the endolymphatic sacs of MD patients and in the inner ear of adult mice. Conclusions and Significance Endocytosis may be involved in the pathogenesis of sporadic MD, furthermore CHMP1A, VPS4A, FCN3 and MMP9 could be considered as potential biomarkers.

Age-dependent structural reorganization of utricular ribbon synapses.

In mammals, spatial orientation is synaptically-encoded by sensory hair cells of the vestibular labyrinth. Vestibular hair cells (VHCs) harbor synaptic ribbons at their presynaptic active zones (AZs), which play a critical role in molecular scaffolding and facilitate synaptic release and vesicular replenishment. With advancing age, the prevalence of vestibular deficits increases; yet, the underlying mechanisms are not well understood and the possible accompanying morphological changes in the VHC synapses have not yet been systematically examined. We investigated the effects of maturation and aging on the ultrastructure of the ribbon-type AZs in murine utricles using various electron microscopic techniques and combined them with confocal and super-resolution light microscopy as well as metabolic imaging up to 1year of age. In older animals, we detected predominantly in type I VHCs the formation of floating ribbon clusters, mostly consisting of newly synthesized ribbon material. Our findings suggest that VHC ribbon-type AZs undergo dramatic structural alterations upon aging.

Universal Repositioning Maneuver: A New Treatment for Single Canal and Multi-Canal Benign Paroxysmal Positional Vertigo by 3-Dimensional Model Analysis.

Benign paroxysmal positional vertigo is the most common peripheral vestibular disorder and is currently treated by many types of repositioning maneuvers. A simplification of this procedure would be desirable. A new, anatomically realistic, 3-dimensional computational simulator of the human labyrinth provides a novel insight to evaluate the viability of any new maneuver. The purpose of this study is to propose a single maneuver with potential to treat canalolithiasis-type benign paroxysmal positional vertigo of any individual canal, or even multiple canals on the same side, based on a 3-dimensional model. The benign paroxysmal positional vertigo Viewer, a 3-dimensional model of the human labyrinth, was used to analyze a "Universal Repositioning Maneuver." Through the gravity vector, the expected position of the otoliths was demonstrated by moving the model through a single sequence of head positions, successfully promoting otolith migration from the three semicircular canals to the utricular cavity, either individually or together. The analysis with the 3-dimensional model predicts the effectiveness of the Universal Repositioning Maneuver for the resolution of each single canal or multiple-canal benign paroxysmal positional vertigo canalolithiasis, making treatment much more straightforward.

The Biophysical Modelling of the Equilibrium Receptors

The receiver or the analyser’s peripheral segment, the afferent pathway which takes the excitation to the cerebral cortex and the cortical segment. The simplest equilibrium takes place then two forces of equal size and directly opposed act simultaneously. If several forces act on different directions on an object, the object can be in equilibrium only if the effect of one is cancelled by the others. The equilibrium analyser is situated in the internal ear. The receptors of the macula are stimulated mechanically by the otolithes. Their stimulation takes place in static and dynamic conditions. This way, correcting motor reaction of the position of body and head are triggered at the level of the nervous centres, in order to maintain the equilibrium for the entire duration of movement. The vestibular sense is not a proper equilibrium sense, but an important component of the mechanisms which contribute to the adjustment of equilibrium, next to the kinaesthetic, visual, tactile analysers and cerebellum. The relative change of the stimulus is proportional with the relative change of the stimulus. They found that the so-called method of amplitude estimation resulted in values with very dispersed intervals, therefore, they applied the correlation of the analyzers.

Menière's Syndrome Associated With Fibrous Dysplasia of the Temporal Bone.

Menière's Syndrome Associated With Fibrous Dysplasia of the Temporal Bone.

A study of auditory brainstem response in vitiligo patients

Introduction and Aim: Vitiligo is a hypomelanotic, idiopathic disease influencing entire pigmentary system which includes stria vascularis of internal ear described by depigmented patches in the skin because of absence of melanin and functioning melanocytes in the epidermis. The aim of this study was to assess the audiological irregularities by assessing the brain stem auditory evoked potential in vitiligo patients and comparing with the healthy controls. Materials and Methods: Forty clinically confirmed vitiligo patients of 20 to 40 years of both genders, with or without therapy were enlisted from the Dermatology and cosmetology outpatient clinics, Government Stanley Hospital. Forty controls with similar ages and genders were chosen. The Neuro perfect Medicaid polyrite instrument was used in recording Brainstem Evoked Reaction Audiometry (BERA) in both vitiligo individuals and controls. Inter-Peak Latencies (IPL) and Absolute Wave Latencies (AWL)were measured and analysed by using SPSS version 17. Student's independent 't' test was done for comparing the groups. Results: AWL and IPL of the two ears were measured and both were compared in the study and control groups. In the left ear, AWL III of study subjects had a significant increase 3.34+0.16 than that of controls 3.27+0.19; IPL I-III also significantly increased in the study subjects 1.91+0.16 than the controls 1.77+0.17. In the right ear, AWL III of study subjects had a significant increase 3.18+0.17 than the controls 3.06+0.15; IPL I-III also significantly increased in the study subjects 1.79+0.17 than the controls 1.64+0.16. Conclusion: BERA findings were abnormal in clinically asymptomatic research subjects, suggesting that this test should be included in the routine follow-up of vitiligo patients to detect audiological subclinical involvement.