Broken chords [cochlear implants]
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Implants can return the senses of hearing but the brain is by far the most important component, as one user discovered. The paper discusses about Michael Chorost's account on the cochlear implant implanted into his skull. The implant would bypass the damaged and recently failed inner ear. What is remarkable about cochlear implants is that the brain can get by with such sparse information. The typical implant stimulates just 16 nerves, a fraction of the number that pass from the ear to the brain in a hearing person. Not only did Chorost, like others with these implants, have to deal with the huge gaps in information passed to the brain, but the new ways that long unused nerves were being stimulated. The surgeons do not find particular neurons $they simply locate those among a bundle that are known to be involved in hearing.We describe the methodology and rationale behind the delivery of therapeutic medicines to the inner ear. The inner ear has long been impervious to pharmacologic manipulation. This is most likely the result of a protective mechanism called the blood-labyrinth barrier, whose function closely resembles that of the blood-brain barrier. This protective barrier impedes the clinician's ability to treat inner ear diseases with systemically administered medications. Since 1935, otolaryngologists have attempted to manipulate the inner ear with transtympanically injected medicines. Success has varied widely, but medicinal ablation of vestibular function can be achieved in this manner. Unfortunately, the auditory system is also at great risk from any medicine that is delivered to the inner ear via the middle ear. Over the past 10 years, significant improvements in drug delivery have allowed for more “titratable” treatment, which has reduced (but not eliminated) the risk of permanent hearing loss. In this article, we discuss both novel and time-tested methods of delivering medicines to the inner ear. We also review the classes of medications that alter inner ear function and the attendant risks of such treatments.
Barrier function
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Abstract The microchemical analysis of human inner ear fluid has not only advanced our knowledge of inner ear function in normal and pathological states, but also has added another dimension to our diagnostic armamentarium in inner ear disease. The purpose of this thesis is To review and evaluate all pertinent literature concerning the chemistry of human inner ear fluids. To determine what percentage of inner ear fluids can be collected without contamination by hemolyzed cells (hemoglobin) or erythrocytes. To study the glucose concentrations in human inner ear fluid in various pathological states. To present the data from uncontaminated endolymph samples in Ménière's disease. To study the correlation between the clinical picture of acoustic neurinoma and the results of inner ear fluid analysis. To evaluate the present status of diagnostic labyrinthotomy (labyrinthine tap).
Human ear
Endolymph
Tissue fluid
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Summary
Genetic inner ear disorders are among the most common congenital abnormalities and lead to hearing loss and balance disorders. Ideally, tissue culture models of the inner ear should contain a functional unit combining otic sensory and nonsensory cell types to recapitulate the varied etiologies of inner ear disorders. Here, we evaluated cell type diversity of late-stage human pluripotent stem cell-derived inner ear organoids using single-cell transcriptomic analysis, electron microscopy and immunohistochemistry. We observed the induction of on-target inner ear-related periotic mesenchymal cells alongside off-target induction of skeletal myocytes, endothelial cells, and ependymal cells. By constructing a single-cell transcriptomic atlas of the human fetal and adult inner ear, we show that epithelium in the inner ear organoids contains cochlear and vestibular identities similar to the developing human inner ear. Moreover, the inner ear organoids contain immature type I and type II vestibular hair cells. Within these putative inner ear cell types, we confirmed the expression of genes and proteins linked to sensorineural hearing loss. This approach using human inner ear organoids would allow for disease modeling of specific genetic inner ear pathologies in the sensory and nonsensory domains of the inner ear.Otic vesicle
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Inner ear sensory cells are very susceptible to injuries and recovery after damage is very difficult. Recently several drugs including neurotrophic factors have been reported to protect against inner ear injury. The purpose of this experimental study is to find new methods for applying drugs to the inner ear that effectively protect against inner ear damage. Biodegradable hydrogel was used as a carrier for application of brain-derived neurotrophic factor (BDNF) into the inner ear of guinea pigs through the round window membrane. After application of BDNF the number of surviving spiral ganglion neurons increased following injury of inner ear hair cells and spiral ganglion neurons by ototoxic treatment. This result indicates that BDNF provides effective protection against inner ear damage and that biodegradable hydrogel is useful for application of drugs to the inner ear.
Spiral ganglion
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Summary Genetic inner ear disorders are among the most common congenital abnormalities and lead to hearing loss and balance disorders. Ideally, tissue culture models of the inner ear should contain a functional unit combining otic sensory and nonsensory cell types to recapitulate the varied etiologies of inner ear disorders. Here, we evaluated cell type diversity of late-stage human pluripotent stem cell-derived inner ear organoids using single-cell transcriptomic analysis, electron microscopy and immunohistochemistry. We observed the induction of on-target inner ear-related periotic mesenchymal cells alongside off-target induction of skeletal myocytes, endothelial cells, and ependymal cells. By constructing a single-cell transcriptomic atlas of the human fetal and adult inner ear, we show that epithelium in the inner ear organoids contains cochlear and vestibular identities similar to the developing human inner ear. Moreover, the inner ear organoids contain immature type I and type II vestibular hair cells. Within these putative inner ear cell types, we confirmed the expression of genes and proteins linked to sensorineural hearing loss. This approach using human inner ear organoids would allow for disease modeling of specific genetic inner ear pathologies in the sensory and nonsensory domains of the inner ear.
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Membranous labyrinth
Ear disease
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Abstract Hearing loss is a common disability affecting the world’s population today. While several studies have shown that inner ear gene therapy can be successfully applied to mouse models of hereditary hearing loss to improve hearing, most of these studies rely on inner ear gene delivery in the neonatal age, when mouse inner ear has not fully developed. However, the human inner ear is fully developed at birth. Therefore, in order for inner ear gene therapy to be successfully applied in patients with hearing loss, one must demonstrate that gene delivery can be safely and reliably performed in the mature mammalian inner ear. The posterior semicircular canal approach has been shown to be an effective gene delivery method in the neonatal mouse inner ear. In this study, we examine the steps involved in posterior semicircular canal gene delivery in the adult mouse inner ear. We observe that the adult mouse inner ear is more susceptible to surgical trauma. We also find that the duration of perilymphatic leakage and injection rate have a significant effect on the post-surgical hearing outcome. Our results show that AAV2.7m8 is capable of transducing the adult mouse inner and outer hair cells with high efficiency.
Outer ear
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Sera from patients with various inner-ear diseases, especially Ménière's disease, were investigated by Western blot against guinea pig inner-ear proteins. Of 45 patients, 24 (53%) with various inner-ear diseases had antibodies against inner-ear proteins, compared with 0 of 10 (0%) in control subjects without inner-ear diseases. Of the 10 proteins that showed a positive reaction with patient sera, the 28-kD band was unique in that it appeared only in the membranous fraction of the inner ear and was highly positive (28%) in reaction with Ménière's disease patient sera. The results in the present study with proteins extracted from guinea pig inner ear were consistent with our previous study using proteins from human inner ear, suggesting that the 28-kD protein may be a candidate for detecting autoimmune inner-ear disease.
Ear disease
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It is well known that the adult mammalian cochlea lacks regenerative capacity, and that the consequence of inner ear damage in humans is permanent sensorineural hearing loss. Since the discovery that hair cells can regenerate in birds, a broad range of studies and research projects has been designed in order to understand this process and to extend it to the mammalian inner ear. The aim of this review is to evaluate the possible future directions and targets of mammalian inner ear regeneration offering an analysis of possible future scenarios.
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Although very little is known about the role of immunologic responses in disorders of the inner ear, including sensorineural hearing loss, data lending support to the possibility of their involvement have recently been published. The present experimental study was undertaken to obtain a better understanding of the fine structures of the inner ear following systemic immune responses. In guinea pigs sensitized with egg albumin, antigen challenge not only evoked bronchospasms, but also induced some pathologic changes in the inner ear, especially in the stria vascularis. These findings lead to the inference that the inner ear may be affected by systemic immune responses in sensitized animals.
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