CT-scanning of the cochlea in Pendred's syndrome

The inner ears of 5 adult patients with Pendred's syndrome were investigated using a Siemens SOMATOM DRG. Five normal hearing adults participated in the investigation as a control group. The CT-scanning comprised 10-15 consecutive scans of the cochlea. The CT evaluation was performed using both a special bone setting and a soft tissue setting. The cochlear content was quantitatively evaluated by drawing an irregular region of interest on the bone pictures. The region of interest was then transferred to the soft tissue pictures by means of the standard program of the CT-scanner. The resulting mean values of attenuation expressed in Hounsfield Units were significantly lower in the Pendred cochleas than in the normal cochleas. At the same time a typical Mondini malformed cochlea was demonstrated in all patients with Pendred's syndrome. The lower values of attenuation of the cochlea in Pendred's syndrome reflect the rudimentarily developed infra-cochlear osseous structures in this disease. We conclude that CT-scanning of the cochlea using this procedure is reliable enough to replace the conventional axial-pyramidal tomography when a Mondini cochlea is suspected.     

Deep-water waves in the cochlea

In order to obtain physical insight from a mathematical solution of the cochlear mechanics problem, a delicate balance is required between and refinements in modelling. For the study of the transition of long to short waves (deep-water waves) a closed-form solution is advantageous; this can, however, only be obtained at the cost of further simplification. In previous work the course of the impedance function z(x) was, therefore, reduced to the extreme; in the neighbourhood of the resonance location z(x) was assumed to be a linear function of x - the so-called ‘straight-line approximation’.This restriction is removed in the present paper. A ‘hyperbolical approximation’ of the impedance function z(x) is introduced and it is shown that with this function the two-dimensional cochlea model can be solved in closed form. The computation results show that, for not too large values of the damping parameters δ, the response in the neighbourhood of the resonance location is almost as well represented by the formerly used ‘straight-line approximation’ as by the ‘hyperbolic approximation’. Hence the principal aspects of cochlear resonance are well brought to light with the ‘straight-line approximation’. This implies that in the case under consideration the dominant part played by short waves is confirmed.When a larger range of x values is to be considered, the hyperbolic approximation is advantageous. The computed response functions agree better with experimental data from the literature. However, it is clear that really satisfactory agreement seems not possible with a two-dimensional model.     

Relationship of Pathology to Function in Congenital Hearing Loss: II. The Auditory Function in Congenital Hearing Loss

The pathological entities are of value to audiologists because the hearing function of each individual represented is known. Such knowledge permits us to make prediction in similar cases as to what can be expected auditorally of other young children. From this information a more rational selection of therapeutic techniques can be made for the child. In the cases of the polytomograms shown previously, standard audiometric tests reveal the amount of hearing present or absent; in the cases of the histo-pathological studies, hearing tests using observations of responses were taken shortly after birth, before the infants expired. Logical extrapolation to other children can be made, and a system of assigning each child to the appropriate habilitation procedure is described. Manual, oral, and auditory approaches – or some combinations of these – must all be considered, in view of the findings reported.     

鸟纲蜗管微血管的比较解剖学观察

目的：了解鸡内耳蜗管微血管的超微结构，为相关研究提供资料。方法：分别应用透射电镜和扫描电镜对10只成年鸡内耳蜗管微血管的超微结构进行观察。结果：鸡内耳蜗管组织中末见典型的薄壁毛细血管，基底膜中末见微血管分布；鸡耳蜗组织中的微血管管壁较厚，从内皮细胞至周边基膜问有呈交替排列的多层纤维、周细胞及其胞突；血管盖的每条皱签中都含有1条微血管，螺旋神经节内微血管与蜗管内的微血管结构相似；扫描电镜下，微血管表面周细胞胞突交织成网状。结论：鸡内耳蜗管微血管与哺乳纲动物内耳蜗管微血管的超微结构及分布有较大差别，其意义尚待进一步探讨。     

Distribution of canalicular reticulum in Deiters cells and pillar cells of gerbil cochlea

Postfixation with an osmium tetroxide-potassium ferrocyanide solution revealed in supporting cells in the organ of Corti a network of canaliculi termed canalicular reticulum (CR). In Deiters cells (DCs), the CR filled cytosol at the base of the phalanx and under plasmalemma apposed to either the outer hair cells' (HCs) basal surface or nerve terminals. From these locations the CR, accompanied by dense fibrillar substance, descended along microtubule bundles and terminated by surrounding the rosette complex in the apical cytosol. Canalicular profiles protruding from the reticulum penetrated the loose meshwork comprising the periphery of the rosette complex to contact at intervals branches of the dense trabeculae that make up the core of the complex. This arrangement disclosed a structural and presumably functional relationship between outer HCs and the CR and rosette complex. Inner pillar cells (PCs) exhibited moderately abundant to sparse profiles of CR interspersed between microtubule bundles of the microtubule stalk that connected head and foot regions. More elaborate CR extended as a network upward from the top of the microtubule stalk part way into the head body and downward into a conical expansion of the stalk at the base of the cell. Cytosol on the medial side of the basal microtubule expansion contained abundant CR which in conjunction with CR between basal microtubule bundles lay situated for possible uptake of ions or neurotransmitter released from numerous adjoining nerves. CR in outer PCs resembled that in inner PCs but appeared less prevalent in the head and foot regions and did not occur in cytosol beside the basal microtubule stalk. Characteristically small Golgi complexes accompanied the reticulum in DCs and were prevalent in the upper regions but absent in the mid and lower part of inner PCs. Short cisternae in the Golgi stacks associated with CR contrasted with the lengthier cisternae in the complexes infrequently observed in cytosol outside the microtubule stalk of inner PCs.     

Cytokeratin expression in the epithelia of the adult human cochlea

Summary Epithelia can be characterized by the specific expression pattern of their cytokeratin components. Therefore, we investigated the immunohistochemical expression of different cytokeratin subunits in frozen sections of chemically fixed, non-decalcified, adult human cochleas. The organ of Corti and the marginal cells of the stria vascularis showed reactivity for cytokeratin subunits 8, 18 and 19, whereas the other cochlear epithelia in addition expressed cytokeratin 7. The expression of cytokeratins 7, 8, 18 and 19 by the epithelia of the adult human cochlea is typical of simple epithelia. The deviant cytokeratin pattern of the organ of Corti and marginal cells of the stria vascularis may well reflect their differences in functional state and/or differentiation as compared to the other cochlear epithelia.This work was presented in part at the 25th Workshop on Inner Ear Biology, 4–7 September 1988, London, UK     

Wave propagation and dispersion in the cochlea

Insight into cochlear mechanics can be obtained from semi-analytical and asymptotic solution methods of which the Liouville-Green (LG) method — in another context known as the WKB method — is the most important one. This paper describes the dispersion properties of fluid waves in general terms and develops the LG formulation on that basis. The eikonal equation of the LG method is shown to be identical to the dispersion relation in dispersive-wave theory. Consideration of the group velocity then leads to the derivation of the central LG formula as it has been used in an earlier paper on the LG method (Boer E. and Viergever M.A. (1982): Hearing Res. 8, 131–155). The formulation appears to apply as well to dissipative and active (i.e., energy-producing) systems. Of the many possible collateral subjects two are selected for a deeper discussion: amplification, concentration and expansion of energy, and the problem of reflection of cochlear waves. In the latter context, it is shown why — and under which conditions — cochlear waves are not reflected, despite the large degree of dispersion that they show. The analysis brings to light a fundamental asymmetry of the model regarding the direction of wave travel: waves travelling in the direction opposite to the normal one are likely to undergo reflection, while waves in the normal direction are not reflected.     

Electron microscopic atlas of the simian cochlea

An electron microscopic atlas of simian cochlear duct structures is presented with the hope that it may help to clarify certain questions of structural-functional relationships. Emphasis is placed on structures directly involved in sensory transduction and in synaptic transmission, at afferent and efferent nerve fiber terminals. A brief discussion is included as an introduction to the possibilities of interpretation of electron microscopic data. Orientation of electron micrographs is assisted by means of numerical coding on light microscopic photographs, and by means of a diagram which combines electron microscopic and light microscopic data.     

Anatomical correlates of impulse noise-induced mechanical damage in the cochlea

Changes in the surface morphology of the organ of Corti in the chinchilla were studied following exposure to blast waves at 160 dB peak SPL. The generation and development of a mechanically induced lesion on the organ of Corti was followed over a period of 30 days using scanning electron microscopy. The most prominent feature of the lesion was the complete separation of a 5–7 mm strip of the sensory epithelia consisting of outer hair cells, Deiter cells and Hensen cells from the reticular lamina and the basilar membrane. The inner hair cells in this same area survived for several days in a remarkably normal condition. A spectrum of ciliary changes was observed on the inner and outer hair cells that differ somewhat from those commonly reported following continuous noise exposure. Some of the observed changes in morphology can be related to a variety of inferred mechanical events on the basilar membrane.     

High-resolution magnetic resonance imaging of human cochlea

OBJECTIVES: High-resolution MRI (MRI) of human inner ear structures provides several advantages over other imaging modalities. High-resolution visualization of inner ear ultrastructure in a noninvasive manner may provide important information about inner ear disease that is not obtainable in other ways. The study was performed to demonstrate the capabilities of MRI at high resolution on the human cochlea, vestibular structures, and facial nerve. Comparative analyses of MRI anatomy with that seen on histological dissection were made. The aim of the study was to define the anatomy of human cadaveric cochlea using a 9.4-Tesla magnetic resonance scanner, currently the most powerful magnetic resonance magnet available. STUDY DESIGN: Experimental pilot study of cadaveric human cochleae. METHODS: Serial scanning using a 9.4-Tesla magnetic resonance imager on normal preserved and fresh cadaveric inner ears was performed in different planes. RESULTS: The images revealed detailed anatomy of the modiolus, utricle, saccule, semicircular canals, and facial nerve. Specifically, identifiable structures within the cochlea included the osseous spiral lamina, Reissner's membrane, membranous spiral lamina, spiral ligament, and others. CONCLUSIONS: Data established through the acquisition of images from cadaver cochlea, facial nerve, and vestibular complex provide a foundation for developing steps for testing temporal bones and, eventually, patients with Meniere's disease and other inner ear disease. The present ongoing project will provide information on baseline images of the inner ear using high-resolution MRI.     

Anomalous myelinated nerve fibers in the spiral ligament of the chinchilla cochlea

Summary A fascicle of myelinated nerve fibers has been found within spiral ligament tissue of the chinchilla cochlea. The presence of nerve fibers in this region of the cochlea has not been previously reported in any species and its occurrence in the chinchilla is thought to be anomalous.This research was supported by the National Institutes of Neurological and Communicative Disorders and Stroke, Grants NSO4615 and NS12125     

Point-impedance characterization of the basilar membrane in a three-dimensional cochlea model

In this paper we derive which impedance definition appropriately represents the basilar membrane in a simple three-dimensional model (de Boer's 'block model') of the cochlea. The starting point of our considerations is a system of parallel visco-elastic beams as characterization of the basilar membrane. It is possible to transform this representation into an impedance concept by observing that the membrane velocity is to a very good approximation distributed over the width as a centred half cosine function, independent of the pressure distribution. The ensuing impedance definition is more accurate than the one proposed by de Boer (Hearing Res. 4, 53-77, 1981). The improvement to the model solutions is moderate, however, as appears from numerical calculations of the basilar membrane velocity.     

Optical coherence tomography of the cochlea in the porcine model

Objectives/Hypothesis: To demonstrate the feasibility of optical coherence tomography in microstructural imaging of the porcine cochlea. Study Design: Ex vivo, porcine model. Methods: Optical coherence tomographic images of the porcine cochlea were obtained by thinning the bone from the basal turn of the cochlea leaving the endosteum intact. The images were compared with the corresponding histological sections. Results: In the areas of thinned bone, images were obtained of the stria vascularis, Reissner's membrane, basilar membrane, tectorial membrane, scala media, scala tympani, and scala vestibuli. The bone was too thick for adequate light penetration in the areas where it was not thinned. Good histological correlation was obtained. Conclusions: Cochlear and vestibular microanatomic structures of the pig cochlea were clearly identified with histological confirmation, suggesting the potential application of this noninvasive imaging modality for in vivo imaging of the human cochlea.     

Microtubules in the cochlea of the hypothyroid developing rat

In order to study the effects of hypothyroidism on the development of microtubules in the cochlea, rat pups were rendered hypothyroid by daily administration of propylthiouracil. Microtubules were studied by immunofluorescence and electron microscopy. The absence of immunostaining of pillar cells with antimicrotubule or antitubulin antibodies was correlated with a retarded morphological development of microtubules within these same structures. The above alterations induced an abnormal development of pillar cells, non-appearance of the tunnel of Corti, and stunted epithelial growth. In contrast, a distinct immunoreaction was observed under the outer hair cells. This was attributed to abnormal persistence of afferent dendrites containing microtubules. The results suggest that, while the effect of thyroid hormone on microtubules in afferent cochlear dendrites could not be demonstrated, thyroid hormone is necessary for the normal development of microtubules in epithelial structures.     

鸡耳蜗神经再生的超微结构观察

用庆大霉素损害鸡耳蜗后，间隔１￣１２ｄ处死动物，透射电镜下观察耳蜗神经再生的过程。发现ＧＭ损害后有神经鞘膜松散、溃变及肿胀较明显。     

Immunohistochemical localization of histamine receptors in rat cochlea

OBJECTIVE: Histamine may have physiologic functions in the inner ear. The locations of histamine receptors, however, have not yet been identified in the mammalian cochlea. The aim of this study was to investigate the localization of histamine receptor subtypes (H1, H2, and H3 receptors) in rat cochlea. METHODS: Immunohistochemistry was performed with antibodies specific for each of the histamine receptors (H1, H2, and H3). To identify the type I and II spiral ganglion cells in the cochlea, some cryostat sections were double stained with antibodies to both a histamine receptor and neurofilament 200 kD, which predominantly stains type II spiral ganglion cells in the cochlea. RESULTS: All H1, H2, and H3 receptor immunoreactive staining was limited to the spiral ganglion cells of the cochlea. Spiral ganglion cells with positive immunoreactivity to the neurofilament 200 kD antibody were stained only slightly by histamine H1, H2, and H3 receptor antibodies, indicating that histamine receptor immunoreactivity is specific to type I ganglion cells. CONCLUSIONS: These findings indicate that histamine receptors are present in the cochlea and support the hypothesis that histamine plays a physiologic role in the cochlea.     

Brainstem location of efferent neurones projecting to the guinea pig cochlea

Retrograde transport of horseradish peroxidase using tetramethylbenzidine as a chromagen was used to map the cell bodies of origin of the efferent projection to the cochlea in the guinea pig. Large numbers of small labelled neurones were found within the body of the lateral superior olivary nucleus (LSO) ipsi-lateral to the injected cochlea. Labelled cells within the contra-lateral LSO were extremely rare (1% or less). Large labelled neurones were found both ipsi-laterally and contra-laterally in the dorsomedial periolivary region, including the medial nucleus of trapezoid body and in the ventral and lateral nuclei of the trapezoid body and the ventral nucleus of lateral lemniscus. It was concluded that some aspects of the distribution of these efferent neurones in the guinea pig are similar to the situation in the rat, whilst others resemble more closely the arrangement found in cat.