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Liu Y, Jolly C, Braun S, Janssen T, Scherer E, Steinhoff J, Ebenhoch H, Lohner A, Stark T, Kiefer J. Effects of a dexamethasone-releasing implant on cochleae: A functional, morphological and pharmacokinetic study. Hear Res 2015; 327:89-101. [PMID: 25987502 DOI: 10.1016/j.heares.2015.04.019] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 04/22/2015] [Accepted: 04/24/2015] [Indexed: 01/12/2023]
Abstract
AIM This study evaluated the impact of a dexamethasone-releasing silicone implant on hearing function preservation, cochlear morphology and perilymph pharmacokinetics after cochlear implantation. METHODS Guinea pigs were implanted unilaterally with silicone rods containing either 2% dexamethasone (DEXA group, n = 18) or no dexamethasone (control group, n = 17). Auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs) were measured preoperatively and over 6 months postoperatively. Cochlear histology using standard hematoxylin and eosin (H&E) staining and tumor necrosis factor (TNF)-alpha staining was performed 1 month postoperatively. Twenty-two guinea pigs were involved in the pharmacokinetic study, and real-time drug concentrations in perilymph were investigated using high-performance liquid chromatography (HPLC). The Mann-Whitney U test (1-tailed) was used for statistical analyses. RESULTS ABR and DPOAE testing demonstrated decreased hearing function immediately postoperatively followed by a progressive hearing loss within the first day postoperatively. There was almost no observable hearing improvement in the control group from 1 week to 6 months postoperatively, but hearing levels in the DEXA group improved gradually from 1 week to 12 weeks. Hearing loss in the DEXA and control group was 5.0 ± 3.4 dB and 21.7 ± 5.3 dB, respectively at a 16-kHz stimulus frequency 6 months postoperatively. The difference in threshold shifts was present throughout all measured frequencies, and it was significant at 4-24 kHz. The morphological study revealed new fibrosis formation in the scala tympani, which encapsulated the implanted electrode. TNF-alpha positive staining in the cochleae of the DEXA group was less evident than the control group. The pharmacokinetic study revealed a peak perilymph concentration 30 min postoperatively and sustained dexamethasone release at least 1 week postoperatively. CONCLUSION Cochlear implants that incorporate dexamethasone can release drug chronically in the inner ear and induce significant long-term recovery and preservation of auditory function after implantation.
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Affiliation(s)
- Ya Liu
- Department of Otolaryngology-Head and Neck Surgery, Beijing Naval General Hospital, Beijing 100048, PR China
| | - Claude Jolly
- Electrode Research Section, MED-EL Medical Electronics, Innsbruck, Austria
| | | | - Thomas Janssen
- Clinic for Otorhinolaryngology, Head- and Neck Surgery, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Elias Scherer
- Clinic for Otorhinolaryngology, Head- and Neck Surgery, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Jochen Steinhoff
- Clinic for Otorhinolaryngology, Head- and Neck Surgery, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Harald Ebenhoch
- Clinic for Otorhinolaryngology, Head- and Neck Surgery, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Andrea Lohner
- Clinic for Otorhinolaryngology, Head- and Neck Surgery, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Thomas Stark
- Clinic for Otorhinolaryngology, Head- and Neck Surgery, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Jan Kiefer
- HNO-Zentrum Neupfarrplatz, 12/II, 93047 Regensburg, Germany.
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Dalhoff E, Turcanu D, Gummer AW. Forward and reverse transfer functions of the middle ear based on pressure and velocity DPOAEs with implications for differential hearing diagnosis. Hear Res 2011; 280:86-99. [PMID: 21624450 DOI: 10.1016/j.heares.2011.04.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 04/06/2011] [Accepted: 04/23/2011] [Indexed: 11/17/2022]
Abstract
Recently it was shown that distortion product otoacoustic emissions (DPOAEs) can be measured as vibration of the human tympanic membrane in vivo, and proposed to use these vibration DPOAEs to support a differential diagnosis of middle-ear and cochlear pathologies. Here, we investigate how the reverse transfer function (r-TF), defined as the ratio of DPOAE-velocity of the umbo to DPOAE-pressure in the ear canal, can be used to diagnose the state of the middle ear. Anaesthetized guinea pigs served as the experimental animal. Sound was delivered free-field and the vibration of the umbo measured with a laser Doppler vibrometer (LDV). Sound pressure was measured 2-3 mm from the tympanic membrane with a probe-tube microphone. The forward transfer function (f-TF) of umbo velocity relative to ear-canal pressure was obtained by stimulating with multi-tone pressure. The r-TF was assembled from DPOAE components generated in response to acoustic stimulation with two stimulus tones of frequencies f(1) and f(2); f(2)/f(1) was constant at 1.2. The r-TF was plotted as function of DPOAE frequencies; they ranged from 1.7 kHz to 23 kHz. The r-TF showed a characteristic shape with an anti-resonance around 8 kHz as its most salient feature. The data were interpreted with the aid of a middle-ear transmission-line model taken from the literature for the cat and adapted to the guinea pig. Parameters were estimated with a three-step fitting algorithm. Importantly, the r-TF is governed by only half of the 15 independent, free parameters of the model. The parameters estimated from the r-TF were used to estimate the other half of the parameters from the f-TF. The use of r-TF data - in addition to f-TF data - allowed robust estimates of the middle-ear parameters to be obtained. The results highlight the potential of using vibration DPOAEs for ascertaining the functionality of the middle ear and, therefore, for supporting a differential diagnosis of middle-ear and cochlear pathologies.
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Affiliation(s)
- Ernst Dalhoff
- Eberhard-Karls-University Tübingen, Department Otolaryngology, Section of Physiological Acoustics and Communication, Elfriede-Aulhorn-Straße 5, Tübingen, Germany.
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Olzowy B, Deppe C, Arpornchayanon W, Canis M, Strieth S, Kummer P. Quantitative estimation of minor conductive hearing loss with distortion product otoacoustic emissions in the guinea pig. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2010; 128:1845-1852. [PMID: 20968357 DOI: 10.1121/1.3474898] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Subclinical conductive hearing losses (CHLs) can affect otoacoustic emissions and therefore limit their potential in the assessment of the cochlear function. Theoretical considerations to estimate a minor CHL from DPOAE measurements [Kummer et al. (2006). HNO 54, 457-467] are evaluated experimentally. They are based on the fact, that the level difference of the stimulus tones L(1) and L(2) for optimal excitation of the inner ear is given by L(1)=aL(2)+b. A CHL is presumed to attenuate both L(1) and L(2) to the same extent such that excitation of the inner ear is no longer optimal. From the change of L(1) that is necessary to restore optimal excitation of the inner ear and thus to produce maximal DPOAE levels, the CHL can be estimated. In 10 guinea pig ears an experimental CHL was produced, quantified by determination of compound action potential (CAP) thresholds at 8 kHz (CHL(CAP)) and estimated from DPOAE measurements at 8 kHz (CHL(DPOAE)). CHLs up to 12 dB could be assessed. CHL(DPOAE) correlated well with CHL(CAP) (R=0.741, p=0.0142). Mean difference between CHL(DPOAE) and CHL(CAP) was 4.2±2.6 dB. Estimation of minor CHL from DPOAE measurements might help to increase the diagnostic value of DPOAEs.
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Affiliation(s)
- Bernhard Olzowy
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig Maximilians University of Munich Medical Center, Marchioninistr. 15, 81377 Munich, Germany.
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Level alterations of the 2f 1–f 2 distortion product due to hypoxia in the guinea pig depend on the stimulus frequency. Eur Arch Otorhinolaryngol 2009; 267:351-5. [DOI: 10.1007/s00405-009-1052-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2009] [Accepted: 07/07/2009] [Indexed: 11/26/2022]
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Turcanu D, Dalhoff E, Müller M, Zenner HP, Gummer AW. Accuracy of velocity distortion product otoacoustic emissions for estimating mechanically based hearing loss. Hear Res 2009; 251:17-28. [PMID: 19233253 DOI: 10.1016/j.heares.2009.02.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 02/02/2009] [Accepted: 02/02/2009] [Indexed: 10/21/2022]
Abstract
Distortion product otoacoustic emissions (DPOAEs) measured as vibration of the human eardrum have been successfully used to estimate hearing threshold. The estimates have proved more accurate than similar methods using sound-pressure DPOAEs. Nevertheless, the estimation accuracy of the new technique might have been influenced by endogenous noise, such as heart beat, breathing and swallowing. Here, we investigate in an animal model to what extent the accuracy of the threshold estimation technique using velocity-DPOAEs might be improved by reducing noise sources. Velocity-DPOAE I/O functions were measured in normal and hearing-impaired anaesthetized guinea pigs. Hearing loss was either conductive or induced by furosemide injection. The estimated distortion product threshold (EDPT) obtained by extrapolation of the I/O function to the abscissa was found to linearly correlate with the compound action potential threshold at the f(2) frequency, provided that furosemide data were excluded. The standard deviation of the linear regression fit was 6 dB as opposed to 8 dB in humans, suggesting that this accuracy should be achievable in humans with appropriate improvement of signal-to-noise ratio. For the furosemide animals, the CAP threshold relative to the regression line provided an estimate of the functional loss of the inner hair cell system. For mechanical losses in the middle ear and/or cochlear amplifier, DPOAEs measured as velocity of the umbo promise an accuracy of hearing threshold estimation comparable to classical audiometry.
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Affiliation(s)
- Diana Turcanu
- Eberhard-Karls-University Tübingen, Department Otolaryngology, Section of Physiological Acoustics and Communication, Elfriede-Aulhorn-Strasse 5, Tübingen 72076, Germany.
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Long-term administration of magnesium after acoustic trauma caused by gunshot noise in guinea pigs. Hear Res 2008; 247:137-45. [PMID: 19084059 DOI: 10.1016/j.heares.2008.11.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Revised: 10/23/2008] [Accepted: 11/05/2008] [Indexed: 12/20/2022]
Abstract
In a previous study we observed that a 7-day post-trauma magnesium treatment significantly reduced auditory threshold shifts measured 7 days after gunshot noise exposure. However this improvement was only temporary, suggesting that it could be potentially beneficial to prolong this treatment. The aim of the present study was to evaluate the efficacy of a long-term (1 month) magnesium treatment after an impulse noise trauma, in comparison with either a 7-day magnesium treatment, an administration of methylprednisolone (conventional treatment), or a placebo (NaCl). Guinea pigs were exposed to impulse noise (three blank gunshots, 170 dB SPL peak). They received one of the four treatments, 1 h after the noise exposure. Auditory function was explored by recording the auditory brainstem response (ABR) and measuring the distortion product otoacoustic emissions (DPOAE) over a 3-month recovery period after the gunshot exposure. The functional hearing study was supplemented by a histological analysis. The results showed that a 1-month treatment with magnesium was the most effective treatment in terms of hair cell preservation. The DPOAE confirmed this effectiveness. Methylprednisolone accelerated recovery but its final efficacy remained moderate. It is probable that magnesium acts on the later metabolic processes that occur after noise exposure. Multiple mechanisms could be involved: calcium antagonism, anti-ischaemic effect or NMDA channel blockage. Regardless of the specific mechanism, a 1-month treatment with magnesium clearly attenuates NIHL, and presents the advantage of being safe for use in humans.
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Bian L, Chen S. Comparing the optimal signal conditions for recording cubic and quadratic distortion product otoacoustic emissions. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2008; 124:3739-3750. [PMID: 19206801 PMCID: PMC2676628 DOI: 10.1121/1.3001706] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Revised: 09/24/2008] [Accepted: 09/24/2008] [Indexed: 05/27/2023]
Abstract
Odd- and even-order distortion products (DPs), evoked by two primary tones (f(1),f(2),f(1)<f(2)), represent different aspects of cochlear nonlinearity. The cubic and quadratic difference tones (CDT 2f(1)-f(2) and QDT f(2)-f(1)) are prominent representatives of the odd and even DPs. Distortion product otoacoustic emissions (DPOAEs) were measured within a primary level (L(1),L(2)) space over a wide range of f(2)f(1) ratios to compare the optimal signal conditions for these DPs. For CDT, the primary level difference decreased as L(1) increased with a rate proportional to the f(2)f(1) ratio. Moreover, the optimal ratio increased with L(1). A set of two formulas is proposed to describe the optimal signal conditions. However, for a given level of a primary, increasing the other tone level could maximize the QDT amplitude. The frequency ratio at the maximal QDT was about 1.3 and quite constant across different primary levels. A notch was found in the QDT amplitude at the f(2)f(1) ratio of about 1.22-1.25. These opposite behaviors suggest that the optimal recording conditions are different for CDT and QDT due to the different aspects in the cochlear nonlinearity. Optimizing the DPOAE recordings could improve the reliability in clinical or research practices.
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Affiliation(s)
- Lin Bian
- Department of Speech and Hearing Science, Auditory Physiology Lab, Arizona State University, Tempe, Arizona 85287-0102, USA.
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Gehr DD, Janssen T, Michaelis CE, Deingruber K, Lamm K. Middle ear and cochlear disorders result in different DPOAE growth behaviour: implications for the differentiation of sound conductive and cochlear hearing loss. Hear Res 2004; 193:9-19. [PMID: 15219315 DOI: 10.1016/j.heares.2004.03.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2003] [Accepted: 03/30/2004] [Indexed: 10/26/2022]
Abstract
Input/output functions of distortion product otoacoustic emissions (DPOAE I/O-functions) give an insight into the compressive, non-linear sound processing of the cochlea. With an inner ear dysfunction a steeper I/O-function is observed. Due to the linear sound processing of the middle ear, one can assume that the DPOAE growth behaviour remains unaltered with a sound conduction dysfunction. If that is true, a differentiation between middle and inner ear dysfunction will be possible by using the slope of DPOAE I/O-functions as a means for assessing cochlear compression. In order to test that hypothesis, DPOAE I/O-functions were recorded in a wide primary tone level range at up to 8 f2 frequencies between 2.0 and 8.0 kHz (15 dB SPL < L2< 60 dB SPL; L1=0.46 L2 + 41 dB SPL; f2/f1=1.2) in guinea pigs in which middle (saline solution in the bulla) and inner ear (exposure to loud broadband noise) disorders were induced. Middle ear dysfunction resulted in a reduction of the DPOAE amplitude independent of the primary tone level. Consequently, DPOAE growth behaviour was not affected. In contrast to that, during cochlear impairment, steepened DPOAE I/O-functions were observed reflecting loss of compression of the cochlear amplifier. Accordingly, DPOAE I/O-functions allow a differentiation between middle and inner ear dysfunction. Further studies will have to show the usability of this method for clinical diagnostics, e.g. for detecting sound conduction disturbances in newborn hearing screening due to amniotic fluid or Eustachian tube dysfunctions during the early postnatal period.
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Affiliation(s)
- Daniel D Gehr
- ENT Department, Technische Universität München, Clinic Rechts der Isar, Ismaninger Strasse 22, D-81675 Munich, Germany
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