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Stiepan S, Shera CA, Abdala C. Characterizing a Joint Reflection-Distortion OAE Profile in Humans With Endolymphatic Hydrops. Ear Hear 2023; 44:1437-1450. [PMID: 37450653 PMCID: PMC10593104 DOI: 10.1097/aud.0000000000001387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
OBJECTIVES Endolymphatic hydrops (EH), a hallmark of Meniere disease, is an inner-ear disorder where the membranes bounding the scala media are distended outward due to an abnormally increased volume of endolymph. In this study, we characterize the joint-otoacoustic emission (OAE) profile, a results profile including both distortion- and reflection-class emissions from the same ear, in individuals with EH and speculate on its potential utility in clinical assessment and monitoring. DESIGN Subjects were 16 adults with diagnosed EH and 18 adults with normal hearing (N) matched for age. Both the cubic distortion product (DP) OAE, a distortion-type emission, and the stimulus-frequency (SF) OAE, a reflection-type emission, were measured and analyzed as a joint OAE profile. OAE level, level growth (input/output functions), and phase-gradient delays were measured at frequencies corresponding to the apical half of the human cochlea and compared between groups. RESULTS Normal hearers and individuals with EH shared some common OAE patterns, such as the reflection emissions being generally higher in level than distortion emissions and showing more linear growth than the more strongly compressed distortion emissions. However, significant differences were noted between the EH and N groups as well. OAE source strength (a metric based on OAE amplitude re: stimulus level) was significantly reduced, as was OAE level, at low frequencies in the EH group. These reductions were more marked for distortion than reflection emissions. Furthermore, two significant changes in the configuration of OAE input/output functions were observed in ears with EH: a steepened growth slope for reflection emissions and an elevated compression knee for distortion emissions. SFOAE phase-gradient delays at 40 dB forward-pressure level were slightly shorter in the group with EH compared with the normal group. CONCLUSIONS The underlying pathology associated with EH impacts the generation of both emission types, reflection and distortion, as shown by significant group differences in OAE level, growth, and delay. However, hydrops impacts reflection and distortion emissions differently. Most notably, DPOAEs were more reduced by EH than were SFOAEs, suggesting that pathologies associated with the hydropic state do not act identically on the generation of nonlinear distortion at the hair bundle and intracochlear reflection emissions near the peak of the traveling wave. This differential effect underscores the value of applying a joint OAE approach to access both intracochlear generation processes concurrently.
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Affiliation(s)
- Samantha Stiepan
- Auditory Research Center, Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA 90033, USA
| | - Christopher A Shera
- Auditory Research Center, Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA 90033, USA
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA
| | - Carolina Abdala
- Auditory Research Center, Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA 90033, USA
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Abdala C, Luo P, Shera CA. Characterizing the Relationship Between Reflection and Distortion Otoacoustic Emissions in Normal-Hearing Adults. J Assoc Res Otolaryngol 2022; 23:647-664. [PMID: 35804277 PMCID: PMC9613820 DOI: 10.1007/s10162-022-00857-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 06/24/2022] [Indexed: 11/28/2022] Open
Abstract
Otoacoustic emissions (OAEs) arise from one (or a combination) of two basic generation mechanisms in the cochlea: nonlinear distortion and linear reflection. As a result of having distinct generation processes, these two classes of emissions may provide non-redundant information about hair-cell integrity and show distinct sensitivities to cochlear pathology. Here, we characterize the relationship between reflection and distortion emissions in normal hearers across a broad frequency and stimulus-level space using novel analysis techniques. Furthermore, we illustrate the promise of this approach in a small group of individuals with mild-moderate hearing loss. A "joint-OAE profile" was created by measuring interleaved swept-tone stimulus-frequency OAEs (SFOAEs) and 2f1-f2 distortion-product OAEs (DPOAEs) in the same ears using well-considered parameters. OAE spectra and input/output functions were calculated across five octaves. Using our specific recording protocol and analysis scheme, SFOAEs in normal hearers had higher levels than did DPOAEs, with the most pronounced differences occurring at the highest stimulus levels. Also, SFOAE compression occurred at higher stimulus levels (than did DPOAE compression) and its growth in the compressed region was steeper. The diagnostic implications of these findings and the influence of the measurement protocol on both OAEs (and on their relationship) are discussed.
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Affiliation(s)
- Carolina Abdala
- Auditory Research Center, Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA, 90033, USA.
| | - Ping Luo
- Auditory Research Center, Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Christopher A Shera
- Auditory Research Center, Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA, 90033, USA
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, 90089, USA
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Salt AN, Hirose K. Communication pathways to and from the inner ear and their contributions to drug delivery. Hear Res 2018; 362:25-37. [PMID: 29277248 PMCID: PMC5911243 DOI: 10.1016/j.heares.2017.12.010] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Revised: 11/08/2017] [Accepted: 12/05/2017] [Indexed: 01/04/2023]
Abstract
The environment of the inner ear is highly regulated in a manner that some solutes are permitted to enter while others are excluded or transported out. Drug therapies targeting the sensory and supporting cells of the auditory and vestibular systems require the agent to gain entry to the fluid spaces of the inner ear, perilymph or endolymph, which surround the sensory organs. Access to the inner ear fluids from the vasculature is limited by the blood-labyrinth barriers, which include the blood-perilymph and blood-strial barriers. Intratympanic applications provide an alternative approach in which drugs are applied locally. Drug from the applied solution enters perilymph through the round window membrane, through the stapes, and under some circumstances, through thin bone in the otic capsule. The amount of drug applied to the middle ear is always substantially more than the amount entering perilymph. As a result, significant amounts of the applied drug can pass to the digestive system, to the vasculature, and to the brain. Drugs in perilymph pass to the vasculature and to cerebrospinal fluid via the cochlear aqueduct. Conversely, drugs applied to cerebrospinal fluid, including those given intrathecally, can enter perilymph through the cochlear aqueduct. Other possible routes in or out of the ear include passage by neuronal pathways, passage via endolymph and the endolymphatic sac, and possibly via lymphatic pathways. A better understanding of the pathways for drug movements in and out of the ear will enable better intervention strategies.
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Affiliation(s)
- Alec N Salt
- Department of Otolaryngology, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO, USA.
| | - Keiko Hirose
- Department of Otolaryngology, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO, USA
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Auditory and vestibular hair cell stereocilia: relationship between functionality and inner ear disease. The Journal of Laryngology & Otology 2011; 125:991-1003. [PMID: 21774850 DOI: 10.1017/s0022215111001459] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The stereocilia of the inner ear are unique cellular structures which correlate anatomically with distinct cochlear functions, including mechanoelectrical transduction, cochlear amplification, adaptation, frequency selectivity and tuning. Their function is impaired by inner ear stressors, by various types of hereditary deafness, syndromic hearing loss and inner ear disease (e.g. Ménière's disease). The anatomical and physiological characteristics of stereocilia are discussed in relation to inner ear malfunctions.
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Sun GH, Leung R, Samy RN, McAfee JS, Hearst MJ, Savage CR, Choo DI, Pensak ML. Analysis of hearing preservation after endolymphatic mastoid sac surgery for Meniere's disease. Laryngoscope 2010; 120:591-7. [DOI: 10.1002/lary.20787] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Salt AN, Brown DJ, Hartsock JJ, Plontke SK. Displacements of the organ of Corti by gel injections into the cochlear apex. Hear Res 2009; 250:63-75. [PMID: 19217935 DOI: 10.1016/j.heares.2009.02.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 01/16/2009] [Accepted: 02/05/2009] [Indexed: 11/20/2022]
Abstract
In order to transduce sounds efficiently, the stereocilia of hair cells in the organ of Corti must be positioned optimally. Mechanical displacements, such as pressure differentials across the organ caused by endolymphatic hydrops, may impair sensitivity. Studying this phenomenon has been limited by the technical difficulty of inducing sustained displacements of stereocilia in vivo. We have found that small injections (0.5-2 microL) of Healon gel into the cochlear apex of guinea pigs produced sustained changes of endocochlear potential (EP), summating potential (SP) and transducer operating point (OP) in a manner consistent with a mechanically-induced position change of the organ of Corti in the basal turn. Induced changes immediately recovered when injection ceased. In addition, effects of low-frequency bias tones on EP, SP and OP were enhanced during the injection of gel and remained hypersensitive after injection ceased. This is thought to result from the viscous gel mechanically limiting pressure shunting through the helicotrema. Cochlear microphonics measured as frequency was varied showed enhancement below 100 Hz but most notably in the sub-auditory range. Sensitivity to low-frequency biasing was also enhanced in animals with surgically-induced endolymphatic hydrops, suggesting that obstruction of the perilymphatic space by hydrops could contribute to the pathophysiology of this condition.
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Affiliation(s)
- Alec N Salt
- Department of Otolaryngology, Box 8115, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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Horner KC, Cazals Y, Guieu R, Lenoir M, Sauze N. Experimental estrogen-induced hyperprolactinemia results in bone-related hearing loss in the guinea pig. Am J Physiol Endocrinol Metab 2007; 293:E1224-32. [PMID: 17711987 DOI: 10.1152/ajpendo.00279.2007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Our group (Horner KC, Guieu R, Magnan J, Chays A, Cazals Y. Neuropsychopharmacology 26: 135-138, 2002) has earlier described hyperprolactinemia in some patients presenting inner ear dysfunction. However, in that study, it was not possible to determine whether hyperprolactinemia was a cause or an effect of the symptoms. To investigate the effect of hyperprolactinemia on inner ear function, we first developed a model of hyperprolactinemia in estrogen-primed Fischer 344 rats and then performed functional studies on pigmented guinea pigs. Hyperprolactinemia induced, after 2 mo, a hearing loss of approximately 30-40 dB across all frequencies, as indicated by the compound action potential audiogram. During the 3rd mo, the hearing loss continued to deteriorate. The threshold shifts were more substantial in males than in females. Observations under a dissection microscope revealed bone dysmorphology of the bulla and the cochlea. Light microscopy observations of cryostat sections confirmed bone-related pathology of the bony cochlear bulla and the cochlear wall and revealed morphopathology of the stria vascularis and spiral ligament. Scanning electron microscopy revealed loss of hair cells and stereocilia damage, in particular in the upper three cochlear turns and the two outermost hair cell rows. The data provide the first evidence of otic capsule and hair cell pathology associated with estrogen-induced prolonged hyperprolactinemia and suggest that conditions such as pregnancy, anti-psychotic drug treatment, aging, and/or stress might lead to similar ear dysfunctions.
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Affiliation(s)
- Kathleen C Horner
- CNRS UMR 6153-1147 INRA, Université Paul Cézanne, Faculté des Sciences et Techniques, Campus St Jérôme, Cases 351 352, Ave Escadrille Normandie Niémen, 13397, Marseille Cedex 20, France.
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Wang J, Pignol B, Chabrier PE, Saido T, Lloyd R, Tang Y, Lenoir M, Puel JL. A novel dual inhibitor of calpains and lipid peroxidation (BN82270) rescues the cochlea from sound trauma. Neuropharmacology 2007; 52:1426-37. [PMID: 17449343 DOI: 10.1016/j.neuropharm.2007.02.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Revised: 01/24/2007] [Accepted: 02/08/2007] [Indexed: 10/23/2022]
Abstract
Free radical and calcium buffering mechanisms are implicated in cochlear cell damage that has been induced by sound trauma. Thus in this study we evaluated the therapeutic effect of a novel dual inhibitor of calpains and of lipid peroxidation (BN 82270) on the permanent hearing and hair cell loss induced by sound trauma. Perfusion of BN 82270 into the scala tympani of the guinea pig cochlea prevented the formation of calpain-cleaved fodrin, translocation of cytochrome c, DNA fragmentation and hair cell degeneration caused by sound trauma. This was confirmed by functional tests in vivo, showing a clear dose-dependent reduction of permanent hearing loss (ED50 = 4.07 microM) with almost complete protection at 100 microM. Furthermore, BN82270 still remained effective even when applied onto the round window membrane after sound trauma had occurred, within a therapeutic window of 24 h. This indicates that BN 82270 may be of potential therapeutic value in treating the cochlea after sound trauma.
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MESH Headings
- Action Potentials/drug effects
- Action Potentials/physiology
- Animals
- Apoptosis/drug effects
- Calpain/antagonists & inhibitors
- Carrier Proteins/metabolism
- Cochlea/enzymology
- Cochlea/injuries
- Cochlea/pathology
- Cysteine Proteinase Inhibitors/pharmacology
- Cytochromes c/metabolism
- DNA Fragmentation/drug effects
- Dipeptides/pharmacology
- Electrophysiology
- Female
- Guinea Pigs
- Hair Cells, Auditory/drug effects
- Hair Cells, Auditory/pathology
- Hair Cells, Auditory/physiology
- Hearing Loss, Noise-Induced/pathology
- Hearing Loss, Noise-Induced/prevention & control
- Immunohistochemistry
- Lipid Peroxidation/drug effects
- Microfilament Proteins/metabolism
- Microscopy, Electron, Scanning
- Microscopy, Electron, Transmission
- Round Window, Ear/pathology
- Tympanic Membrane/drug effects
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Affiliation(s)
- Jing Wang
- INSERM U583, Laboratoire de Physiopathologie et Thérapie des Déficits Sensoriels et Moteurs, Montpellier, France
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Ikino CMY, Bittar RSM, Sato KM, Capella NM. Effects of a Nitric Oxide Synthase Type II Inhibitor on Compound Action Potential Thresholds in Experimental Endolymphatic Hydrops. Otol Neurotol 2007; 28:111-5. [PMID: 17031325 DOI: 10.1097/01.mao.0000231591.64972.80] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
HYPOTHESIS Nitric oxide (NO) is likely to be synthesized by nitric oxide synthase Type II (NOS II) action and may partake in the origin of changes of compound action potential (CAP) threshold observed in guinea pigs with induced endolymphatic hydrops. This study aimed to assess the action of a NOS II inhibitor on CAP thresholds in these experimental samples. BACKGROUND In guinea pigs with experimental endolymphatic hydrops, there are lesions on the cochlea and progressive increase of CAP threshold. NOS II was found in the cochlea of this animal model, and it was inferred that NO can contribute by such alterations. METHODS The animals were divided into two groups, in which eight received an intake of a NOS II inhibitor, aminoguanidine, and another eight served as a control group. During 16 weeks, CAP thresholds at 1,000, 2,000, 4,000 and 6,000 on electrocochleography were compared between the groups. RESULTS The group that had an intake of aminoguanidine showed a lower increase on CAP thresholds at 2,000 (p < 0.05) and 6,000 Hz (p < 0.05) at the 12th postoperative week, and at 1,000 (p < 0.05), 2,000 (p < 0.001), 4,000 (p < 0.001), > and 6,000 Hz (p < 0.001) at the 16th week. CONCLUSION We conclude that NOS II inhibitor reduced the elevation of CAP thresholds in experimentally induced endolymphatic hydrops.
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Klar J, Frykholm C, Friberg U, Dahl N. A Meniere's disease gene linked to chromosome 12p12.3. Am J Med Genet B Neuropsychiatr Genet 2006; 141B:463-7. [PMID: 16741942 DOI: 10.1002/ajmg.b.30347] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Meniere's disease (MD) is characterized by spontaneous attacks of vertigo, fluctuating sensorineural hearing loss, tinnitus, and aural fullness. The majority of patients with MD appear sporadic but 5%-13% of the cases have a family history for the disease. The cause of both the sporadic and inherited forms of MD remains unclear despite a number of candidate genes defined from their association with hearing loss. We have performed a genome wide linkage scan on a large Swedish family segregating MD in five generations. Five candidate regions with a lod score of >1 were identified. Two additional families with autosomal dominant MD were analyzed for linkage to these regions and a cumulative Z(max) of 3.46 was obtained for a single region on chromosome 12p. In two of the three families, a shared haplotype was found to extend over 1.7 Mb which suggests a common ancestral origin. Within this region, a single recombination event restricts the candidate region to 463 kb.
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Affiliation(s)
- Joakim Klar
- Department of Genetics and Pathology, Uppsala University, Uppsala, Sweden
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Dunnebier EA, Segenhout JM, Dijk F, Albers FW. Sensory cell damage in two-phase endolymphatic hydrops: a morphologic evaluation of a new experimental model by low-voltage scanning techniques. Otol Neurotol 2001; 22:655-61. [PMID: 11568675 DOI: 10.1097/00129492-200109000-00017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
HYPOTHESIS The aim of this study was to create a more dynamic animal model of Ménière's disease combining multiple causes, such as the role of endocrine factors and endolymphatic sac dysfunction, that may mimic the fluctuant characteristics of Ménière's disease. BACKGROUND Endolymphatic hydrops remains to be considered a pathologic substrate in the etiology of Ménière's disease. The classic guinea pig model of inducing hydrops by total destruction of the endolymphatic sac is a nonphysiologic rigid model of Ménière's disease. METHODS The authors developed the two-phase endolymphatic hydrops model by inducing hydrops by mild chronic endolymphatic sac dysfunction, in combination with increased endolymph production by aldosterone. Sensory cell damage was evaluated by low-voltage field emission scanning microscopy. RESULTS This study describes a wide spectrum of morphologic effects of the outer hair cells in radial gradients, in which most effects were observed in the third to second row of outer hair cells, and longitudinal gradients in which the most severe effects were observed in the apical turns. Most affected were the ears that underwent distal endolymphatic sac dissection followed by the administration of aldosterone. Damaging effects proceeded from degeneration and absence of short stereocilia of outer hair cells and even some inner hair cells in the apical turns, to stereociliary disarrangement and atrophy, followed by degeneration and absence of outer hair cells, which were replaced by supporting cells. CONCLUSION The two-phase endolymphatic hydrops model seems to represent a functional model that may mimic the fluctuant characteristics of Ménière's disease and emphasizes the influence of multiple and coexisting hydrops-inducing influences.
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Affiliation(s)
- E A Dunnebier
- Department of Otorhinolaryngology, University Hospital Groningen, The Netherlands
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Danckwardt-Lillieström N, Friberg U, Kinnefors A, Rask-Andersen H. "Endolymphatic sacitis" in a case of active Menière's disease. An ultrastructural histopathologic investigation. Ann Otol Rhinol Laryngol 1997; 106:190-8. [PMID: 9078930 DOI: 10.1177/000348949710600303] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
An ultrastructural analysis of an entire intraosseous endolymphatic sac (ES) from a patient with active, well-documented Menière's disease was performed for the first time. The results were compared with those obtained from ES biopsy material from patients with acoustic neuromas. The ES was small in size and showed signs of focal inflammation with intraepithelial invasion by mononuclear cells. At these places the normal fine structure, including the vascular anatomy, was altered. The possible relationship between these changes and Meniere's disease is discussed.
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Braun M. Impediment of basilar membrane motion reduces overload protection but not threshold sensitivity: evidence from clinical and experimental hydrops. Hear Res 1996. [DOI: 10.1016/s0378-5955(96)80002-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Abstract
Transmission electron microscopy of the cochlear organ of Corti in experimental endolymphatic hydrops revealed two principal features. Starting 1 month after induction of hydrops, osmiophilic inclusions thought to represent lipofuscin accumulation were frequently observed in the subcuticular cytoplasm of the outer hair cells along the length of the cochlea. Starting 3 months after induction of hydrops the efferent terminals on the outer hair cells appeared to be vacuolated. These data suggest that oxidative insult is likely to contribute to the pathology associated with endolymphatic hydrops and thus that free radical scavengers might be useful in the treatment of Menière's disease patients. In addition the early modification of the efferent innervation of the hydropic cochlea might underlie the known hypersensitivity to various insults, including noise stimulation, glycerol administration and hypoxia.
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Affiliation(s)
- K C Horner
- INSERM XR229 and Université Bordeaux II, Hôpital Pellegrin, France
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Abstract
The cause(s) of the hearing impairment associated with Menière's disease are not understood but are undoubtedly associated with the inner ear endolymphatic hydrops. Two major hypotheses have been proposed and widely received: endolymphatic overpressure followed by leaky membranes and subsequently the mixing of high K+ endolymph with perilymph. Our recent data on an experimental model of endolymphatic hydrops have provided grounds for renewed reflections on the pathology. Indeed our data might be interpreted without involving either of the above hypotheses and suggests that the symptoms of Menière's disease might be accounted for by a flow of perilymph from scala vestibuli towards scala tympani with the mixing of the two perilymphs which are similar but not identical in composition. The higher K+ concentration arriving from the scala vestibuli into the scala tympani at the apex of the cochlea via the helicotrema is likely to be toxic to hair cell and auditory nerve fiber function. The mixing of the two perilymphs could result in deterioration of low frequency sensitivity, provoke low frequency tinnitus and in the long term cause spiral ganglion cell degeneration at the apex of the cochlea. The feeling of fullness in the ear might be the result of the decreasing perilymph volume in the scala vestibuli which could give rise to inner ear conductive losses. The patency of the cochlear aqueduct might play a role in determining the high risk group of individuals likely to manifest the symptoms of endolymphatic hydrops.
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Affiliation(s)
- K C Horner
- Laboratoire d'Audiologie Expérimental, Inserm U229, Hôpital Pellegrin, Bordeaux, France
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