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At least 955 records · Page 53Linked to original sources
PubMed1994

Magnetic resonance examination of the inner ear and cerebellopontine angle in patients with vertigo and/or abnormal findings at vestibular testing.

The inner ears of 167 patients with vertigo and/or abnormal findings at vestibular testing were studied using magnetic resonance (MR). Pathology potentially explaining vertigo was found in 54 patients, and was detected in the posterior fossa (28%), the internal auditory canal (28%) and the membranous labyrinth (44%). The overall percentage of pathology and the percentage of pathology found in the membranous labyrinth was high and was probably influenced by the referral pattern in our hospital where high resolution MR of the inner ear (three dimensional Fourier transformation-constructive interference in steady state sequence; 3DFT-CISS sequence) is available. Unenhanced, and especially gadolinium (Gd)-enhanced T1-weighted spin-echo images, are needed to detect most of the pathology inside the internal auditory canal, and some of the lesions inside the membranous labyrinth. 3DFT-CISS images are the only images that can show fibrous obliteration of the intralabyrinthine fluid spaces, and are therefore necessary to recognise most of the intralabyrinthine pathology. Finally, T2-weighted spin-echo images are best suited to demonstrate cerebellar or brain stem infarction. An additional MR-angiography sequence (three dimensional Fourier transformation-fast imaging with steady precession; 3DFT-FISP) is used when vascular compression of the cochleovestibular nerve is suspected. MR is the method of choice to look for pathology in patients with vertigo, and allows detection of pathology that remains invisible with other imaging techniques. However, well adapted sequences are needed to detect these lesions.

Cerebellopontine Angle↗
PubMed2002

Extracellular matrices associated with the apical surfaces of sensory epithelia in the inner ear: molecular and structural diversity.

The ultrastructure and molecular composition of the extracellular matrices that are associated with the apical surfaces of the mechanosensory epithelia in the mouse inner ear are compared. A progressive increase in molecular and structural organization is observed, with the cupula being the simplest, the otoconial membrane exhibiting an intermediate degree of complexity, and the tectorial membrane being the most elaborate of the three matrices. These differences may reflect changes that occurred in the acellular membranes of the inner ear as a mammalian hearing organ arose during evolution from a simple equilibrium receptor. A comparison of the molecular composition of the acellular membranes in the chick inner ear suggests the auditory epithelium and the striolar region of the maculae are homologous, indicating the basilar papilla may have evolved from the striolar region of an otolithic organ. A comparison of the tectorial membranes in the chick cochlear duct and the mouse cochlea reveals differences in the structure of the noncollagenous matrix in the two species that may result from differences in the stochiometry of alpha- and beta-tectorin and/or differences in the post-translational modification of alpha-tectorin. This comparison also indicates that the appearance of collagen in the mammalian tectorial membrane may have been a major step in the evolution of an electromechanically tuned vertebrate hearing organ that operates over an extended frequency range.

Acoustic Maculae↗
PubMed1997

[Imaging of the inner ear].

New computed tomography (CT) and magnetic resonance (MR) techniques allow more detailed anatomic studies of the inner ear. CT is still the best technique to study patients with fractures, congenital malformations and otodystrophies involving the inner ear. During recent years MR imaging has emerged as an excellent method to detect pathology in the internal auditory canal, membranous labyrinth and bony labyrinth and to characterize petrous apex lesions. MR has even proved its value in patients with fractures and congenital malformations making the diagnosis of, for instance, labyrinthine concussion and absence of the vestibulocochlear nerve possible. The diagnosis of acute/chronic labyrinthitis and intralabyrinthine tumors has also became possible. However, MR and CT are often complementary, as is the case in patients with mixed hearing loss, congenital malformations and petrous apex lesions.

Diagnosis, Differential↗
PubMed1996

Retinoic acid-induced embryopathy of the mouse inner ear.

Retinoic acid (RA) is an active metabolite of vitamin A that is teratogenic when present in excess during mammalian embryogenesis. We have investigated the effect of embryonic exposure to nonphysiological levels of all-trans RA on the development of the mouse inner ear. Dysmorphogenesis of both vestibular and auditory portions of the inner ear, and abnormal formation of the surrounding capsule are produced by exposure to teratogenic levels of RA at an embryonic age of 9 days (E9). There was no observable teratogenic effect of RA when administered at earlier (i.e., E7 or E8) or later (i.e., E10) stages of otic morphogenesis. We hypothesize that exposure to high levels of RA during a critical period of early otic morphogenesis interferes with the inductive tissue interactions required for inner ear development.

Abnormalities, Drug-Induced↗
PubMed2005

Hmx homeobox gene function in inner ear and nervous system cell-type specification and development.

The Hmx homeobox gene family is comprised of three members in mammals, Hmx1, Hmx2, and Hmx3, which are conserved across the animal kingdom and are part of the larger NKL clustered family of homeobox genes. Expression domains of Hmx genes in distantly related species such as Drosophila and mouse suggest an ancestral function in rostral central nervous system development. During vertebrate evolution, the Hmx genes appear to have been recruited into additional roles in inner ear morphogenesis and specification of vestibular inner ear sensory and supporting cell types. Being derived from a common ancestor, the vertebrate Hmx gene family is thus a strong candidate to investigate functional overlap versus the unique roles played by multiple genes belonging to the same family. The functions of Hmx2 and Hmx3 were investigated via directed gene mutagenesis and the primary regions where Hmx2 and Hmx3 exert their individual functions are consistent with their expression domains, such as the vestibule and uterus. Meanwhile, it is notable that some tissues where both Hmx2 and Hmx3 are extensively expressed were not severely affected in either of the Hmx2 or Hmx3 single mutant mice, suggesting a possible functional overlap existing between these two genes. Compound Hmx2 and Hmx3 double mutant mice showed more severe defects in the inner ear than those displayed by either single knockout. Furthermore, novel abnormalities in the hypothalamic-neuroendocrine system, which were never observed in either of the single mutant mice, confirmed a hypothesis that Hmx2 and Hmx3 also function redundantly to control embryonic development of the central nervous system.

Animals↗
PubMed1992

Ciprofloxacin and the inner ear--a morphological and round window membrane permeability study.

This study was conducted in order to evaluate ototoxic potential and passage through the round window membrane of ciprofloxacin, a newly developed antimicrobial drug with an antibacterial spectrum well suited for the treatment of suppurative otitis media. Ciprofloxacin was injected intraperitoneally in 40 guinea pigs in doses ranging from 25 to 150 mg/kg body weight for 14 consecutive days. Sixteen inner ears of chinchillas were exposed to ciprofloxacin at a concentration of 0.1 mg/ml applied directly to the intact round window membrane. Despite severe deterioration of the animals injected with the highest doses, no behavioral or definite morphological evidence of inner ear or vestibular damage could be seen. Ciprofloxacin concentrations in the perilymph were determined with high-performance liquid chromatography. Direct passage of ciprofloxacin, presumably via the round window membrane, was demonstrated. After 1 h and 15 min, an arithmetic mean concentration of 0.165 micrograms/ml (95% confidence interval +/- 0.053) could be demonstrated in the perilymph. It can be concluded that ciprofloxacin has no ototoxic effect when administered systemically. Furthermore, when locally applied into the middle ear, it has the capacity to pass into the inner ear.

Animals↗
PubMed1994

Expression of the beta-subunit isoforms of the Na,K-ATPase in rat embryo tissues, inner ear and choroid plexus.

We report evidence of the apical localization of the two Na,K-ATPase beta-subunit isoforms in cells of the inner ear and of the choroid plexus of the rat. To this end, we generated isoform-specific antisera against the human Na,K-ATPase beta 1 and beta 2 subunits. These polyclonal rabbit antisera were raised against truncated beta-isoform proteins that were made in E coli with pET expression vectors. Deglycosylation of the native antigen with N-endoglycosidase F shows four bands in the beta 1 isoform and five bands in the beta 2 isoform immunoblots. In E15 rat embryos, the beta 1 isoform was detected in brain, heart and kidney and the beta 2 isoform only in brain. While beta-subunit mRNA expression (Watts AG, Sanchez-Watts G, Emanuel JR, Levenson R (1991) Proc Natl Acad Sci USA 88, 7425-7429), immunoblotting and enzymatic activity have been determined (Zlokovic BV< mackic JB, Wang L, McComb JG, McDonough A (1993) J Biol Chem 268, 8019-8025), very little is known about the specific localization of each beta-isoform in the epithelia of choroid plexus and inner ear. Immunocytochemical preparations of 15-day-old whole rat embryos and adult rat brain showed an enhanced staining for the beta 1 and beta 2 isoforms in the apical membrane of the ampullary crests of the inner ear's semicircular ducts and in the cuboidal cells of the choroid plexus.

Animals↗
PubMed1989

Localization of the atrial natriuretic peptide binding sites in the inner ear tissue--possibly an additional regulating system.

Specific high affinity atrial natriuretic peptide (ANP) binding sites were identified and localized by autoradiography (125J-ANP 1-28) in the inner ear of guinea pigs. ANP is a cardiac hormone known to mediate increased capillary permeability, vasodilation, and natriuresis. Since specific receptors for ANP exist in both eye and brain, possibly playing a role in regulation of fluid and pressure (14, 15), we hypothetized that ANP might be involved also in inner ear fluid dynamics via interaction with other volume/electrolyte balance regulating hormones including vasopressin, renin, and aldosteron. The distribution of ANP receptor in the inner ear tissue appears unequal, which may play a significant role in view of some functional disturbances such as Meniere's disease.

Animals↗
PubMed1993

Inner ear inflammation and round window otosclerosis.

Recently, it has been suggested that otosclerosis represents the host's ongoing immunologic response to measles or other viral antigens. Documentation of past inflammation within the inner ear would serve as further evidence that this mechanism may be at play in the pathogenesis of the disease. Among the characteristic signs of prior inflammation in the inner ear is the presence of lamellar bone at the site of inflammation. This has been described in the temporal bone of a patient with immune-mediated deafness and with the temporal bones of experimental models of immune-mediated inner ear disease. Review of temporal bones with round window otosclerosis from the Eastern Temporal Bone Bank at the Massachusetts Eye and Ear Infirmary show that in four of ten cases there are characteristic signs of a prior severe inflammatory event centered in the scala tympani adjacent to the otosclerotic lesion. Otosclerosis, therefore, may have an inflammatory stage that is the consequence of a host response to an inciting event.

Autoimmunity↗
PubMed1998

Inner ear damage in guinea pigs exposed to stable and impulse noise.

OBJECTIVE: To investigate the inner ear damage after exposure to stable noise, impulse noise and stable plus impulse noise in guinea pigs. METHODS: Ninety-six healthy guinea pigs were divided into 3 equal groups. (1) Stable noise group: exposed to 110 dBA stable noise for 3 days, 4 hours per day. (2) Impulse noise group: exposed to 165 dBA simulated cannon fire impulse noise 10 times successively at an interval of 10 seconds. (3) stable plus impulse noise group: exposed to the same stable noise as that in the first group, then after a 2-hour rest, the animals were followed with impulse noise exposures as that in the second group. After those exposure, each of the 3 groups was further divided into 4 subgroups according to the time after the noise exposure, namely, the right after, 7 d, 14 d and 30 d groups. The evoked cortical potential responses to click and tone burst stimulation sound were examined. The surface preparation and celloidine embedded serial section of the cochlea were observed under a light microscope. RESULTS: Both the stable and impulse noise could increase the hearing threshold and damage the inner ear hair cells. The damage in the first group was relatively slight, whereas in group 3 the damage was more severe than that in the other 2 groups. CONCLUSION: For seamen who are working in heavy noise environment, corresponding measures should be taken to protect their ears from noise which induces hearing loss.

Animals↗
PubMed1976

Inner ear decompression sickness.

With recent increases in commercial, military, and sport diving to deeper depths, inner ear injuries during such exposures have been encountered more frequently and noted during several phases of diving: during compression, at stable deep depths, with excessive noise exposure in diving, and during decompression. The pathophysiology of these injuries differs, depending upon the phase of diving in which the injuries occur. In this report, 23 cases of hearing loss, tinnitus, and/or vertigo occurring during or shortly after decompression are presented. Thirteen of these cases occurred in helium-oxygen dives involving a change to air during the latter stages of decompression. A significant correlation is present between prompt recompression treatment, relief of symptoms, and lack of residual deficits. Current knowledge indicates that the management of otologic decompression sickness should include: 1. prompt recompression to at least 99 feet deeper than the symptom onset depth; 2. recompression using the previous helium-oxygen mixture when the injuries occur during or shortly after a switch from helium-oxygen to air during the latter stages of decompression; 3. the use of parenteral diazepam for symptom relief and cyclic inhalations of oxygen enriched treatment gases; and 4. the avoidance of further diving by divers who exhibit permanent inner ear injuries after the acute symptoms have subsided.

Adult↗
PubMed2006

Autoantibodies against inner ear proteins in patients with delayed endolymphatic hydrops and unilateral juvenile deafness.

CONCLUSIONS: Patients with the contralateral type of delayed endolymphatic hydrops (DEH) may undergo an autoimmune attack against the other inner ear. As patients with unilateral juvenile deafness show no progression, despite lengthy observation, the autoantibody against the 68-kDa protein may be unrelated to the pathogenesis of DEH. OBJECTIVE: The contralateral type of DEH is believed to have an autoimmune etiology, and sometimes develops from unilateral juvenile deafness. The purpose of this study was to determine whether autoantibodies are pathogenetically important in DEH. MATERIAL AND METHODS: Sera from 9 patients with DEH, 18 patients with profound unilateral juvenile hearing loss and 15 control volunteer without inner ear diseases were investigated by means of Western blot assay against rat inner ear proteins. RESULTS: Among 8 patients with the contralateral type of DEH, 6 (75%) showed at least 1 reactive band on Western blotting. The protein that reacted most frequently had a molecular weight of 28 kDa, which was consistent with our previous results. Among 18 patients with unilateral juvenile deafness, 5 (28%) showed reactive bands, exclusively at 68 kDa.

Adult↗
PubMed1999

Gene expression of P2X-receptors in the developing inner ear of the rat.

Reverse transcription-polymerase chain reaction (RT-PCR) was used to characterize the expression of P2X receptor subunits (P2X1-P2X7) in different inner ear tissues. The present study revealed the presence of P2X2, P2X3, P2X4 and P2X7-mRNA in rat organ of Corti, vestibular organ and spiral ganglion at different postnatal developmental stages (PD1-PD16), with slight differences in the onset of expression. Expression of P2X1, P2X5 and P2X6-mRNA was not detectable in the inner ear tissues. In addition, single cell RT-PCR experiments with outer hair cells (OHC) revealed the expression of either the P2X2 or the P2X2-2 splice variant or coexpression of both isoforms in individual cells. Our data suggest that extracellular adenosine-5'-triphosphate (ATP) may play an important role in signal transduction in the inner ear.

Aging↗
PubMed1984

Immunologic and electrophysiological response to cytomegaloviral inner ear infection in the guinea pig.

We investigated the development of labyrinthitis in animals inoculated with guinea pig cytomegalovirus (GPCMV). These animals all became deaf eight days after inoculation into the perilymphatic compartment and showed severe inflammatory changes within the inner ear. Animals that received inactivated virus maintained their hearing throughout the observation period and exhibited normal cochlear morphology. Neither group had serum or perilymph antibody to GPCMV eight days after viral inoculation. We then investigated the effect of systemic immunity to GPCMV on inner ear viral challenge in animals with high levels of serum antibodies to GPCMV. No significant hearing loss could be detected eight days after inner ear inoculation. Seropositive animals that received live virus demonstrated a significant rise in perilymph antibody titer to GPCMV and showed preservation of normal cochlear morphology. Thus, systemic and inner ear immunity to GPCMV afforded protection against damage caused after direct perilymphatic inoculation of live virus.

Action Potentials↗
PubMedDate not supplied

Growth factor regulation of the cell cycle in developing and mature inner ear sensory epithelia.

Growth factors and other extracellular signals regulate cell division in many tissues. Consequently, growth factors may have therapeutic uses to stimulate the production of replacement sensory hair cells in damaged human inner ears, thereby assisting in alleviating hearing loss and vestibular dysfunction. Assessment of the ability of growth factors to stimulate cell proliferation in inner ear sensory epithelia is at an early stage. This paper provides a brief account of what we know regarding growth factor regulation of cell proliferation in developing and mature inner ear sensory epithelia.

Animals↗
PubMed2005

The zebrafish dog-eared mutation disrupts eya1, a gene required for cell survival and differentiation in the inner ear and lateral line.

To understand the molecular basis of sensory organ development and disease, we have cloned and characterized the zebrafish mutation dog-eared (dog) that is defective in formation of the inner ear and lateral line sensory systems. The dog locus encodes the eyes absent-1 (eya1) gene and single point mutations were found in three independent dog alleles, each prematurely truncating the expressed protein within the Eya domain. Moreover, morpholino-mediated knockdown of eya1 gene function phenocopies the dog-eared mutation. In zebrafish, the eya1 gene is widely expressed in placode-derived sensory organs during embryogenesis but Eya1 function appears to be primarily required for survival of sensory hair cells in the developing ear and lateral line neuromasts. Increased levels of apoptosis occur in the migrating primordia of the posterior lateral line in dog embryos and as well as in regions of the developing otocyst that are mainly fated to give rise to sensory cells of the cristae. Importantly, mutation of the EYA1 or EYA4 gene causes hereditary syndromic deafness in humans. Determination of eya gene function during zebrafish organogenesis will facilitate understanding the molecular etiology of human vestibular and hearing disorders.

Animals↗