Ultrastructural study of the human utricular macula and vestibular nerve in meniére's disease.

The authors have carried out an ultrastructural study of the human utricular macula and the vestibular nerve in the internal acoustic meatus of four patients suffering from Meniere's disease. They confirm the presence of degenerative alterations in the utricular sensory epithelium. The nervous fibers situated in the supporting connective tissue of the neuro-epithelium showed modifications in the Schwann cell cytoplasm and in the arrangement of the myelin sheaths. The same alterations appear in the vestibular nerve in the internal acoustic meatus in 2 of our cases. In the other 2, the vestibular nerve was formed by a granular matrix with several myelin figures in the proximity of possible Schwann cell nucleus debris.     

Light and electron microscopic study of vestibular sensory epithelia in 17 cases with acoustic neurinoma.

Vestibular sensory epithelia were studied histologically and ultrastructurally in 17 cases with acoustic neurinoma (AN). The superior vestibular nerve (SVN) near the fundus was also histologically studied in 5 of these 17 cases. Histologically, severe fibrotic change of the vestibular sensory epithelia was found in 1 case, and severe fibrotic change of the SVN was also found in this case. Intra-epithelial cysts were found at the edge of the utricular sensory epithelia in 2 cases. The cysts consisted of the transitional epithelium and were filled with the darkly stained substances. Ultrastructurally, abnormal accumulation of darkly stained masses within the nerve ending and abnormal accumulation of the fibrillar material below the normal basal lamina were frequently observed. These morphological changes described above were regarded as the pathological changes due to AN. In addition, the relationship among the histologic changes, ultrastructural changes and clinical data were fully investigated, and some histologic and ultrastructural changes were regarded as artifacts or age-related changes.     

Ultrastructure of the vestibular sensory organs in delayed endolymphatic hydrops

Vestibular sensory organs were examined ultrastructurally in two cases of delayed endolymphatic hydrops. The patients, two women, 27 and 16 years of age, suffered profound sensory hearing loss in childhood and experienced severe, recurrent vertigo. Specimens were obtained by a translabyrinthial vestibular nerve transection. We studied the utricular macula and the lateral and posterior cristae in one case, and the utricular macula, the anterior and posterior cristae, and the vestibular ganglion in the other. The otoconia and the otoconial membrane, the sensory epithelia, and the vestibular ganglion appeared fairly normal. Although the entire vestibular end organs were not studied in these cases, it was surprising that the ultrastructural findings did not conclusively identify vestibular end organ pathology as the cause of the vertigo attacks.     

Vestibular sensory epithelium in Meniere's disease.

Utricle and horizontal semicircular canal ampulla removed during labyrinthectomy from 11 patients with advanced Meniere's disease were studied under light and electron microscope. In light microscopy the epithelium of both sensory areas appeared fairly normal. Many sensory cells revealed fluid-filled crescents at the nucleus and many cells were extensively vacuolated. Ultrastructurally, a part of the observations were apparently artifacts due to specimen handling; some were normal, age-related findings. Some changes were considered secondary to dilation of the endolymphatic space. True signs of degeneration, seldom seen in these specimens were intraepithelial cysts, necrotic cells, and dark homogeneous masses in the sensory epithelium and dilated nerve fibers in the subepithelial tissue. No general degeneration of the utricular macula or ampullar crista seems to occur in Meniere's disease.     

Ultrastructural findings of the macula utriculi in a case of a petrous apex cholesteatoma: a comparison with findings in a patient with an acoustic neuroma

The morphological characteristics of the vestibular sensory cells of the macula utriculi obtained during surgery in a patient with a petrous apex cholesteatoma were examined using scanning and transmission electron microscopy. Findings were compared to cells studied in a patient with acoustic neuroma. Scanning electron microscopy showed that compared to the apparently normal cells in the acoustic neuroma case, most sensory cells in the cholesteatoma case had large cuticular plates, irregular locations of cilia and no clear polarizations. Supporting cells showed profuse short microvilli on the whole surface. With transmission electron photomicrographs, type I hair cells were not seen and certain morphological changes were observed in type-1I-like cells and supporting cells. We presume that the degenerative changes in the vestibular epithelia were due to circulatory disturbances and/or direct pressure applied to the vestibular nerve at the internal auditory canal, with subsequent involvement of the macula utriculi.     

Morphological and morphometric characteristics of vestibular hair cells and support cells in long term cultures of rat utricle explants

A method for long term culture of utricular macula explants is demonstrated to be stable and reproducible over a period of 28 days in vitro (DIV). This culture system for four-day-old rat utricular maculae is potentially suitable for studies of hair cell loss, repair and regeneration processes as they occur in post-natal mammalian inner ear sensory epithelia. The cellular events that occur within utricular macula hair cell epithelia during 28 days of culture are documented from serial sections. Vestibular hair cells (HCs) and supporting cells (SCs) were systematically counted using light microscopy (LM) and the assistance of morphometric computer software. Ultrastructural observations were made with transmission electron microscopy (TEM) for describing the changes in the fine detailed morphological characteristics that occurred in the explants related to time in vitro. After 2 DIV the density of HCs was 77%, at 21 DIV it was 69%, and at 28 DIV it was 52% of HCs present at explantation. Between 2 DIV and 28 DIV there was a 1.7% decrease of the vestibular macula HC density per DIV. The corresponding decrease of SC density within the utricular explants was less than 1% per DIV. The overall morphology of the epithelia, i.e. relationship of HCs to SCs, was well preserved during the first two weeks in culture. After this time a slight deterioration of the epithelia was observed and although type I and type II HCs were identified by TEM observations, these two HC types could no longer be distinguished from one another by LM observations. In preparations cultured for 21 DIV, SC nuclei were located more apical and further away from the basal membrane compared to their position in macula explants fixed immediately after dissection. The loss of cells that occurred was probably due to expulsion from the apical (i.e. luminal) surface of the sensory epithelia, but no lesions of the apical lining or ruptures of the basal membrane were observed. There were no significant changes in the volume of the vestibular HC comprising macular epithelium during the observation period of 28 DIV.     

Vestibular sympathetic nervous system in guinea pig

The vestibular sympathetic fibers were examined in 20 guinea pigs by the immunohistochemical demonstration of tyrosine hydroxylase and dopamine B-hydroxylase. The vestibular sympathetics originated in the ipsilateral superior cervical ganglion and entered the internal auditory meatus along the labyrinthine artery. At the Schwann-glial border, some of the sympathetic fibers left the artery and went into the superior and inferior divisions of the vestibular nerve and formed a loose meshwork among the Scarpa's ganglion cells, while other fibers continued to follow the labyrinthine artery. Both groups of fibers entered the cristae ampullares and saccular and utricular maculas after several bifurcations in the cribrose areas and terminated either near the capillaries beneath the sensory epithelia or among the vestibular nerve fibers. These fibers traveled freely in the vestibular labyrinth without being restricted to following blood vessels or vestibular nerve fibers. Some sympathetic fibers made direct contact with the vestibular efferent fibers or the vestibular afferent fibers at the node of Ranvier. Sympathetic fibers were not observed in the sensory epithelia or semicircular canals, and were rarely found in the vicinity of the dark cells.     

Menière's disease: morphological findings in eighth nerve and vestibular end organs.

37 patients with advanced Menière's disease were operated on by translabyrinthine 8th nerve neurectomy or middle fossa vestibular neurectomy. Cochlear and vestibular nerves, epithelia of the utricular macula and ampullar crista of horizontal canal were studied. All specimens were fairly well preserved and the microscopic studies suggested that there is no general deterioration of these structures even in long-standing, advanced Menière's disease, but some minor deviations from normal are present in individual cells.     

Histopathology of the vestibular end organs after intratympanic gentamicin failure for Meniere's disease

CONCLUSION: To our knowledge, this is the first report of the histopathology of the vestibular end organs following intratympanic gentamicin for intractable Meniere's disease. There was relative sparing of the utricular macula, compared with the cristae ampullares. However, the utricular macula exhibited severe hair cell loss. Clinically, the patient has been free from vertigo spells for 3 years following labyrinthectomy. Objective: To describe the histopathology and morphometry of the vestibular end organs from a 59-year-old Meniere's patient who underwent transmastoid labyrinthectomy for recurrent vertigo after failed intratympanic gentamicin. MATERIALS AND METHODS: Light and transmission electron microscopy were utilized; with unbiased stereology-physical fractionator for type I, type II hair cell, and supporting cell counts. Comparison with end organ histopathology in a 56-year-old with Meniere's disease without gentamicin treatment was carried out. RESULTS: Histopathological analysis of the semicircular canal cristae ampullares showed severe atrophy of the neuroepithelium with undifferentiated cells, and fibrosis and edema of the stroma. The utricular macula had some remaining type I and type II vestibular hair cells, and nerve fibers and terminals within the underlying stroma. Morphometric measures were obtained from the utricular macula: 2000 type I and 500 type II hair cells, representing 7.3% of type I hair cells and 4.9% of type II hair cells compared with normative controls, and 24 000 supporting cells were obtained.     

Sodium- and potassium-activated ATPase in the mammalian vestibular system

Autoradiographic and cytochemical procedures were employed to determine the cellular distribution of the Na,K-ATPase enzyme in the mammalian vestibular system. A light-microscope survey of vestibular tissues incubated with [(3)H]ouabain shows high densities of ouabain binding sites within the dark cell epithelium (DC) of the ampullae of the semi-circular canals, and to a lesser extent, the DC of the utricular macula. A moderate number of binding sites was found in nerve fibers penetrating the connective tissue beneath the sensory epithelium (SE) of the ampullae and the maculae. A small number of binding sites is distributed in the deep portion of the SE, both in the ampullae and in the maculae. These latter binding sites seem to be associated with nerve terminals and receptor cells. At the ultrastructural level, the vestibular dark cells exhibit extensive basolateral membrane infolding, a morphological hallmark of cells engaged in trans-epithelial ion transport. The cytochemical reaction product is K(+)-dependent, ouabain inhibitable, and is restricted to the basolateral membrane extensions, with little or no product on the luminal membrane. The extent of membrane infolding in dark cells of the utricle is less pronounced than that of the ampullar dark cells and the intensity of the cytochemical reaction appears to correlate with the extent of membrane infolding. The results support the widely held hypothesis that the vestibular dark cells play a role in endolymph production. They also suggest that the vestibular sensory epithelia may be a site of ion exchange.     

Quantitative study of the vestibular sensory epithelium in cochleosaccular dysplasia.

BACKGROUND: Cochleosaccular dysplasia is the most common pathologic finding seen in children with profound congenital sensorineural hearing loss. There has been no quantitative study on the peripheral vestibular system in cochleosaccular dysplasia. OBJECTIVE: To investigate quantitatively the extent of pathologic changes of the vestibular sensory epithelium in cochleosaccular dysplasia. SUBJECTS AND METHODS: Thirteen temporal bones with congenital deafness from 10 individuals were selected for this study from the temporal bone collection of University of Minnesota that showed suitable pathologic findings for the histopathologic criteria of cochleosaccular dysplasia. Age-matched normal control temporal bones were also selected. The vestibular hair cells including types I and II hair cells were counted separately in the saccular macula, utricular macula, and three cristae of the semicircular canals using Nomarski microscopy. RESULTS: The hair cell densities of types I and II hair cells in the macula of the saccule in cochleosaccular dysplasia were significantly decreased compared with the data of normal subjects. Both types I and II hair cells in the utricular macula and the cristae of the three semicircular canals in cochleosaccular dysplasia were well preserved, and no significant difference was observed between findings of cochleosaccular dysplasia and normal controls in the utricle and the three semicircular canals. CONCLUSIONS: In cases with cochleosaccular dysplasia, the neurosensorial hair cells of the saccule were affected; however, the osseous labyrinth, the membranous utricle, and the semicircular canals were normal. Further studies should be performed to establish the pathogenesis of cochleosaccular dysplasia in humans.     

Three-dimensional structures of the vestibular sensory epithelia

Vestibular neurosensory epithelia of the guinea pig and the bull frog were investigated by scanning electron microscopy. The crista ampullaris or macula were freeze fractured followed by maceration with 0.1% OsO4 solution for 24-60 h (osmium-DMSO-osmium method). Following this, three-dimensional intracellular structures were observed. The mitochondria which exist in the nerve chalice surrounding the type I cell were various in shape, globular, long and slender. Golgi apparatus, endoplasmic reticulum and thin fibrous structures of the sensory cells or supporting cells were clearly demonstrated. Concerning nervous system, nerve fibre, afferent and efferent nerve endings, further synaptic structures were also observed stereoscopically.     

An experimental study demonstrating the physiological polarity of the frog's utricle

The frog Rana nigromaculata was used as an experimental model. The utricle and its nerve were isolated with the anterior and the lateral semicircular canal ampullae in frog Ringer's solution. The utricular otoconia and the otoconial membrane were then carefully removed. The halved anterior canal cupula was next placed in the tip of a glass microelectrode, which was mounted on a micromanipulator. The cupula was placed in the center of either the medial or the lateral part of the macula and was moved toward or away from the striola along the axis vertical to the striola. When the medial part of the macula was stimulated, 5 micron of striolapetal cupular movement elicited an excitatory nerve discharge. When the lateral part of the macula was stimulated, the striolapetal stimulus likewise induced an excitatory response. These results indicate the existence of physiological polarity on the utricular macula.     

Modeling the relation between head orientations and otolith responses in humans

We have performed a finite element simulation of realistic displacements of otolith membranes by static linear accelerations. The simulations were based on accurate measurements of the surfaces of human utricular and saccular maculae, which indicate a clear curvature of these surfaces. The results show that this curvature, a feature probably found in all mammals, has no effect on the mechanics of the structure as a whole since the elastic coupling in the otolith membrane is insufficient. Hair cell excitations on any place of the macula are only affected by the local orientation of the macula with respect to acceleration. Based on the displacements of the otolith membrane, we also calculated the induced activation patterns on the otolith epithelia. These patterns provide for the first time a complete image of peripheral otolith activity. The individual activation patterns at selected locations on the macula correspond well with single cell recordings of actual peripheral otolith neurons.     

Projection of afferents from individual vestibular sense organs to the vestibular nuclei in the pigeon

The projection of individual labyrinthine sensory organs to the brain stem was studied by autoradiography, employing discrete [3H]leucine injections into the sensory epithelia. Within the vestibular nuclei, separate partly overlapping termination areas for each end organ were found in the superior and descending vestibular nuclei, whereas projection territories in the medial, ventrolateral and tangential nuclei overlapped extensively. A few lagenar fibres terminated in the external cuneate nucleus. Semicircular canals and utricular macula also project to the lateral cerebellar nucleus and the reticular formation. For each semicircular canal a projection system could be traced to distinct subgroups of the extraocular motoneuron pools.     

Model experiments of BPPV using isolated utricle and posterior semicircular canal

OBJECTIVES: This study was aimed to experimentally investigate the effect of returned otoconia on the utricular using isolated utricles. The effect of interposed otoconia in models of canalolithiasis and cupulolithiasis were also investigated using isolated posterior semicircular canal (PSC). METHODS: Bullfrogs were used. The utricles (Experiment I) and PSC (Experiment II) were removed in Ringer solution. Experiment I-a: The otoconia were carefully removed from the utricular macula with gentle flush of Ringer solution. Before and after the otoconial removal, sinusoidal rotatory stimulation (0.1 Hz, 135 degrees ) was given to record utricular compound action potentials (CAPs). Experiment I-b: (1) Instantaneous changes in the utricular potentials when the otoconial mass was positioned on the macula were recorded. (2) Utricular CAP changes in response to sinusoidal rotation immediately and 10 min after the otoconial positioning were recorded. Experiment II: PSC CAPs due to sinusoidal rotatory stimulation in normal specimen, canalolithiasis and cupulolithiasis models were recorded. RESULTS: Experiment I-a: The utricular CAPs in response to sinusoidal rotation showed sinusoidal oscillation. However, this oscillation disappeared after the otoconial removal. Experiment I-b: (1) The utricular potentials transiently increased for 3-4 s after positioning the otoconial mass. (2) The utricular CAPs increased in seven specimens and decreased in four. Ten minutes after the CAPs were almost the same as immediately after otoconial positioning. Experiment II: In cupulolithiasis model, the PSC CAPs decreased in all specimens. CONCLUSIONS: The otoconia played an essential role as a transducer of acceleration to the utricular macula. Otoconia returned to the utricular macula change utricular reactivity and hence are the possible cause of dizziness after physical therapy. PSC responses to sinusoidal rotation were suppressed in cupulolithiasis model.     

An experimental study demonstrating the physiological polarity of the frog's utricle

Summary The frog Rana nigromaculata was used as an experimental model. The utricle and its nerve were isolated with the anterior and the lateral semicircular canal ampullae in frog Ringer's solution. The utricular otoconia and the otoconial membrane were then carefully removed. The halved anterior canal cupula was next placed in the tip of a glass microelectrode, which was mounted on a micromanipulator. The cupula was placed in the center of either the medial or the lateral part of the macula and was moved toward or away from the striola along the axis vertical to the striola. When the medial part of the macula was stimulated, 5 m of striolapetal cupular movement elicited an excitatory nerve discharge. When the lateral part of the macula was stimulated, the striolapetal stimulus likewise induced an excitatory response. These results indicate the existence of physiological polarity on the utricular macula.     

X-ray microanalytic studies on developing otoconia

The onset of otoconial development in the macula utriculi in CBA/CBA mice occurs on the fifteenth and sixteenth gestational days. Our study was concentrated on the early secretion of calcium in the areas of otoconial formation. The epithelial origin of otoconia is documented. Protrusions from supporting cells in the utricular and saccular epithelia contain very large quantities of calcium in addition to the normal cytoplasmic content of elements. The cell protrusions have an elemental composition clearly differing from that of otoconia as well as from neighbouring utricular cells with protrusions. A directed flow of calcium to developing otoconia from the supporting cells of the maculae is suggested.     

Distribution of calcitonin gene-related peptide nerve fibers in the canine larynx

Summary Immunohistochemistry was used to investigate the distribution pattern of calcitonin gene-related peptide (CGRP) nerve fibers in the laryngeal mucosa, glands and intrinsic muscles of the dog. CGRP immunoreactive nerve fibers were found more frequently than substance P immunoreative nerve fibers in every region of the larynx. In the epithelia, CGRP nerve fibers were mainly found in the epiglottis, arytenoid region and subglottis. Many taste buds were observed in the arytenoid region and were densely innervated by the CGRP nerve fibers. In the lamina propria, the plexus of CGRP nerve fibers was present, with some of these fibers associated with blood vessels. Laryngeal glands were also innervated by a few CGRP nerve fibers. In the intrinsic laryngeal muscles, abundant immunoreactivity was observed and many motor end-plate-like structures were found with CGRP immunoreactivity. These findings strongly suggest that CGRP plays an important role in all of the sensory, motor and autonomic nervous systems of the larynx.     

Temporal bone study of trisomy 13 syndrome

The temporal bones of a 23-week-old female who had multiple congenital anomalies and bilateral hearing loss with trisomy 13 syndrome were evaluated under light microscopy.In the left cochlea, spiral ganglion cells and cochlear nerve fibers are absent. In the right ear, an abnormal branch of the singular nerve passes between the utricle and lateral semicircular canals and separates the two portions, one to the flattened crista of the lateral semicircular canal, the other to the utricular macula. This is a rare report describing a patient with abnormalities in three nerves, including the facial, vestibular, and cochlear nerves.