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Middle ear transmission characteristics in tympanic membrane perforations: cochlear emission and endoscopic study
International Congress Series 1240 (2003) 263 – 267
Middle ear transmission characteristics in tympanic membrane perforations: cochlear emission and endoscopic study Mona Mourad *, Mohamed Badr-el-dine, Hely Megahed ENT Department, Faculty of Medicine, Alexandria University, 22 Amin Fikry Str. Raml station, Alexandria, Egypt
Abstract The aim of this work was to assess the middle ear status by otoendoscopy and evaluate transmission of cochlear echoes by the middle ear structures and to correlate between hearing, otoendoscopy and transmission characteristics of the middle ear in tympanic membrane perforations. The study included a control group of 20 ears with ventilation tubes. The study group included 80 ears with tympanic membrane perforations with mild to moderate conductive hearing loss. Cases were subjected to full history taking, otoscopic examination, basic audiological evaluation (pure tone audiometry and tympanometry), TOAEs and otoendoscopy. Tympanic membrane perforations were divided into central (n = 44), posterior (n = 17), anterior (n = 11) and subtotal perforations (n = 8) with further subdivisions according to the size of the perforation into small (<2 mm) and big (>2 mm). In the study group, 98% of small perforations in the different study groups had recordable emissions, whilst in only 68% of big perforation emissions were recordable. Recordable emissions represent the presence of an effective antegrade and retrograde transmission of vibrations through the middle ear in the presence of a tympanic membrane perforation. This was explained by the presence of the round window baffling mechanism and an intact ISJ, which had been confirmed both otoendoscopically and operatively. Implications of these results are discussed. D 2003 Published by Elsevier B.V. Keywords: Middle ear transmission; Cochlear echoes; Transient otoacoustic emissions; Otoendoscopy
Abbreviations: TOAEs, transient otoacoustic emissions; OAEs, otoacoustic emission; OHC, outer hair cells; ISJ, incudostapedial joint; ABG, air-bone gap; SPL, sound pressure level. * Corresponding author. Fax: +20-34875459. E-mail addresses: [email protected], [email protected] (M. Mourad). 0531-5131/ D 2003 Published by Elsevier B.V. doi:10.1016/S0531-5131(03)01044-6
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1. Introduction The function of the middle ear is to transfer sound vibrations from the external ear to the inner ear, i.e., antegrade transmission. The middle ear also conveys small basilar membrane vibrations known as cochlear echoes to the external ear, i.e., retrograde transmission. Cochlear echoes are low-level sounds produced by the micromechanical activities of outer hair cells. This could be interpreted as a release of acoustic energy into the ear canal from cochlea through the ossicular chain and eardrum to be recorded by a probe in external auditory canal [1,2]. The level of OAEs is doubly dependent on the characteristics of both the antegrade and retrograde middle ear transmission [3]. This double dependence of OAEs transmission characteristics of the middle ear, i.e., effects of signal received by the cochlea and the cochlear response measured into the external auditory meatus, has been considered to have large influence on the OAEs measured in the external auditory meatus. Thus, the middle ear being intermediate between the inner ear and the external ear will be a vital unavoidable link to OAEs measurement [4]. By recording OAEs, the middle ear transfer function thus entails a mobile ossicular chain and a contained cavity for a build-up of SPL corresponding to cochlear echoes. Any deviation from the normal middle ear function would have serious effects on OAE amplitude. In this study, OAEs are of interest because they were not only used to evaluate cochlear function, i.e., OHC integrity, but also to assess the middle ear transfer function in terms of ossicular chain mobility in the presence of a tympanic membrane perforation.
Fig. 1. Mean wave reproducibility in frequency bands 1, 1.5, 2, 3 and 4 kHz in control, central, posterior, anterior and subtotal groups.
M. Mourad et al. / International Congress Series 1240 (2003) 263–267
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2. Aim of the work The aim of this study was to assess the middle ear status by otoendoscopy, to evaluate the transmission of cochlear echoes through the middle ear and to correlate between hearing, otoendoscopy and transmission characteristics of the middle ear.
3. Materials The control group consisted of 20 ears with ventilation tubes with hearing thresholds within normal. The study group consisted of 80 ears with tympanic membrane perforations and mild to moderate conductive hearing levels.
4. Methods All cases were subjected to good history taking, otological evaluation, basic audiological evaluation (air and bone conduction thresholds and tympanometry), TOAEs recording and otoendoscopy.
5. Results Cases in the control group were all children. The study group was mostly in the 20 –30year age group. By otoscopy, tympanic membrane perforations were divided into central
Fig. 2. Comparison between small and big perforation as regard mean overall wave reproducibility and ABG.
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M. Mourad et al. / International Congress Series 1240 (2003) 263–267
(n= 44), posterior (n = 17), anterior (n =11) and subtotal perforation (n =8). As regards the audiometric results, the control group all had within normal hearing thresholds. The poorest air conduction threshold was recorded at 250 Hz in subtotal perforations with a mean of 60.63 dB. The largest ABG was recorded at 250 Hz in subtotal perforation with a mean of 41.88. The greatest basic volume measured by tympanometry was in posterior perforation with a mean of 3.03 cc (S.D.=1.492). Best visualization of the incudostapedial joint was in posterior perforations (11 ears). The joint could not be visualized at all in anterior perforations. The mucosa was edematous in most of the study group. All control group had recordable emissions with best-recorded band wave reproducibility at 2 kHz with a mean of 90.45 (S.D.=8.99) and overall mean wave reproducibility of 84.35 (S.D.=13). Best-recorded overall wave reproductive was in posterior group with a mean 80.12 (S.D.=15.29). Best band wave reproducibility in study group was recorded in 1.5– 2-kHz band (Fig. 1). Results show that as the perforation size decreases, the mean ABG decreases and the recordable mean overall wave reproducibility increases (Fig. 2).
6. Discussion The properties of OAEs makes them ideal for hearing screening, and the presence of a ventilation tube has been shown not to abolish emissions although their amplitude may be
Fig. 3. Case no. 63 with right central perforation.
M. Mourad et al. / International Congress Series 1240 (2003) 263–267
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reduced [5– 7]. This explains selection of the control group in the present study with ventilation tubes. OAE results were scored as pass if the overall wave reproducibility was of z50% and stability of z75% using a click stimulus. Emissions were present but the amplitude was decreased because the middle and external ear cavities were linked by a small perforation in which the ventilation tube was present thus forming a large cavity with subsequent SPL reduction. Therefore, it was possible to speculate that a perforation behaves in the same manner altering the middle ear mechanism by reducing the surface area of the tympanic membrane, thus, amplification provided by the hydraulic action of the matching transformer mechanisms was decreased dependent on the size of the perforation. Another factor was affection of the ossicular chain mobility and finally affection of the baffling round window mechanism. These three factors all cause the stimulus reaching the cochlea to be attenuated. Therefore, a high stimulus level of 85– 100 dB SPL was used to overcome this attenuation. Recording OAEs in cases of tympanic membrane perforations, in spite of its low amplitude, signified an intact ossicular chain and projected to a normal cochlear status. Otoendoscopic inspection and operative visualization of the middle ear proved the former (Fig. 3). Inability to record OAEs were mostly due to ossicular disruption proved also by otoendoscopic inspection and operative visualization of the middle ear. Reproduction of OAEs with z50% overall wave reproducibility was considered an indication of an intact ISJ. In conclusion, since recording OAEs was a simple, easy to use, quick, noninvasive technique [8,9], its use in tympanic membrane perforations would help study the status of ISJ and also could provide information as regards the cochlear function in children with ventilation tubes.
References [1] H.C. Richardson, C. Elliott, J. Hill, The feasibility of recording transient otoacoustic emissions immediately following grommet insertion, Clin. Otolaryngol. 21 (1996) 445 – 448. [2] H.E. Cullington, B.U. Kumar, L.M. Flood, Feasibility of otoacoustic emissions as a hearing screening following grommet insertion, Br. J. Audiol. 32 (1998) 57 – 62. [3] F. Zhao, H. Wada, T. Koike, The influence of middle ear disorders on acoustic emissions, Clin. Otolaryngol. 25 (2000) 3 – 8. [4] J.W. Hall, Anatomy and physiology, Handbook of Otoacoustic Emissions, Singular Publishing Group, California, 2000, pp. 29 – 65. [5] H. Daya, A.E. Hinton, P. Radomskiej, Otoacoustic emissions: assessment of hearing after tympanostomy tube insertion, Clin. Otolaryngol. 21 (1996) 492 – 494. [6] R.G. Amedee, The effects of chronic otitis media with effusion on the measurement of transiently evoked otoacoustic emissions, Laryngoscope 105 (1995) 589 – 595. [7] J.J. Owens, M.J. McCoy, B.L. Lonsbury-Martin, G.K. Martin, Otoacoustic emissions in children with normal ears, middle ear dysfunction, and ventilating tubes, Am. J. Otol. 14 (1) (1993) 34 – 40. [8] D.T. Kemp, Stimulated acoustic emissions from within the human auditory system, J. Acoust. Soc. Am. 64 (1978) 1386 – 1391. [9] N.J. Johnsen, C. Elberling, Evoked acoustic emissions from the human ear: I. Equipment and response parameters, Scand. Audiol. 11 (1982) 3 – 12.
Middle ear transmission characteristics in tympanic membrane perforations: cochlear emission and endoscopic study Mona Mourad *, Mohamed Badr-el-dine, Hely Megahed ENT Department, Faculty of Medicine, Alexandria University, 22 Amin Fikry Str. Raml station, Alexandria, Egypt
Abstract The aim of this work was to assess the middle ear status by otoendoscopy and evaluate transmission of cochlear echoes by the middle ear structures and to correlate between hearing, otoendoscopy and transmission characteristics of the middle ear in tympanic membrane perforations. The study included a control group of 20 ears with ventilation tubes. The study group included 80 ears with tympanic membrane perforations with mild to moderate conductive hearing loss. Cases were subjected to full history taking, otoscopic examination, basic audiological evaluation (pure tone audiometry and tympanometry), TOAEs and otoendoscopy. Tympanic membrane perforations were divided into central (n = 44), posterior (n = 17), anterior (n = 11) and subtotal perforations (n = 8) with further subdivisions according to the size of the perforation into small (<2 mm) and big (>2 mm). In the study group, 98% of small perforations in the different study groups had recordable emissions, whilst in only 68% of big perforation emissions were recordable. Recordable emissions represent the presence of an effective antegrade and retrograde transmission of vibrations through the middle ear in the presence of a tympanic membrane perforation. This was explained by the presence of the round window baffling mechanism and an intact ISJ, which had been confirmed both otoendoscopically and operatively. Implications of these results are discussed. D 2003 Published by Elsevier B.V. Keywords: Middle ear transmission; Cochlear echoes; Transient otoacoustic emissions; Otoendoscopy
Abbreviations: TOAEs, transient otoacoustic emissions; OAEs, otoacoustic emission; OHC, outer hair cells; ISJ, incudostapedial joint; ABG, air-bone gap; SPL, sound pressure level. * Corresponding author. Fax: +20-34875459. E-mail addresses: [email protected], [email protected] (M. Mourad). 0531-5131/ D 2003 Published by Elsevier B.V. doi:10.1016/S0531-5131(03)01044-6
264
M. Mourad et al. / International Congress Series 1240 (2003) 263–267
1. Introduction The function of the middle ear is to transfer sound vibrations from the external ear to the inner ear, i.e., antegrade transmission. The middle ear also conveys small basilar membrane vibrations known as cochlear echoes to the external ear, i.e., retrograde transmission. Cochlear echoes are low-level sounds produced by the micromechanical activities of outer hair cells. This could be interpreted as a release of acoustic energy into the ear canal from cochlea through the ossicular chain and eardrum to be recorded by a probe in external auditory canal [1,2]. The level of OAEs is doubly dependent on the characteristics of both the antegrade and retrograde middle ear transmission [3]. This double dependence of OAEs transmission characteristics of the middle ear, i.e., effects of signal received by the cochlea and the cochlear response measured into the external auditory meatus, has been considered to have large influence on the OAEs measured in the external auditory meatus. Thus, the middle ear being intermediate between the inner ear and the external ear will be a vital unavoidable link to OAEs measurement [4]. By recording OAEs, the middle ear transfer function thus entails a mobile ossicular chain and a contained cavity for a build-up of SPL corresponding to cochlear echoes. Any deviation from the normal middle ear function would have serious effects on OAE amplitude. In this study, OAEs are of interest because they were not only used to evaluate cochlear function, i.e., OHC integrity, but also to assess the middle ear transfer function in terms of ossicular chain mobility in the presence of a tympanic membrane perforation.
Fig. 1. Mean wave reproducibility in frequency bands 1, 1.5, 2, 3 and 4 kHz in control, central, posterior, anterior and subtotal groups.
M. Mourad et al. / International Congress Series 1240 (2003) 263–267
265
2. Aim of the work The aim of this study was to assess the middle ear status by otoendoscopy, to evaluate the transmission of cochlear echoes through the middle ear and to correlate between hearing, otoendoscopy and transmission characteristics of the middle ear.
3. Materials The control group consisted of 20 ears with ventilation tubes with hearing thresholds within normal. The study group consisted of 80 ears with tympanic membrane perforations and mild to moderate conductive hearing levels.
4. Methods All cases were subjected to good history taking, otological evaluation, basic audiological evaluation (air and bone conduction thresholds and tympanometry), TOAEs recording and otoendoscopy.
5. Results Cases in the control group were all children. The study group was mostly in the 20 –30year age group. By otoscopy, tympanic membrane perforations were divided into central
Fig. 2. Comparison between small and big perforation as regard mean overall wave reproducibility and ABG.
266
M. Mourad et al. / International Congress Series 1240 (2003) 263–267
(n= 44), posterior (n = 17), anterior (n =11) and subtotal perforation (n =8). As regards the audiometric results, the control group all had within normal hearing thresholds. The poorest air conduction threshold was recorded at 250 Hz in subtotal perforations with a mean of 60.63 dB. The largest ABG was recorded at 250 Hz in subtotal perforation with a mean of 41.88. The greatest basic volume measured by tympanometry was in posterior perforation with a mean of 3.03 cc (S.D.=1.492). Best visualization of the incudostapedial joint was in posterior perforations (11 ears). The joint could not be visualized at all in anterior perforations. The mucosa was edematous in most of the study group. All control group had recordable emissions with best-recorded band wave reproducibility at 2 kHz with a mean of 90.45 (S.D.=8.99) and overall mean wave reproducibility of 84.35 (S.D.=13). Best-recorded overall wave reproductive was in posterior group with a mean 80.12 (S.D.=15.29). Best band wave reproducibility in study group was recorded in 1.5– 2-kHz band (Fig. 1). Results show that as the perforation size decreases, the mean ABG decreases and the recordable mean overall wave reproducibility increases (Fig. 2).
6. Discussion The properties of OAEs makes them ideal for hearing screening, and the presence of a ventilation tube has been shown not to abolish emissions although their amplitude may be
Fig. 3. Case no. 63 with right central perforation.
M. Mourad et al. / International Congress Series 1240 (2003) 263–267
267
reduced [5– 7]. This explains selection of the control group in the present study with ventilation tubes. OAE results were scored as pass if the overall wave reproducibility was of z50% and stability of z75% using a click stimulus. Emissions were present but the amplitude was decreased because the middle and external ear cavities were linked by a small perforation in which the ventilation tube was present thus forming a large cavity with subsequent SPL reduction. Therefore, it was possible to speculate that a perforation behaves in the same manner altering the middle ear mechanism by reducing the surface area of the tympanic membrane, thus, amplification provided by the hydraulic action of the matching transformer mechanisms was decreased dependent on the size of the perforation. Another factor was affection of the ossicular chain mobility and finally affection of the baffling round window mechanism. These three factors all cause the stimulus reaching the cochlea to be attenuated. Therefore, a high stimulus level of 85– 100 dB SPL was used to overcome this attenuation. Recording OAEs in cases of tympanic membrane perforations, in spite of its low amplitude, signified an intact ossicular chain and projected to a normal cochlear status. Otoendoscopic inspection and operative visualization of the middle ear proved the former (Fig. 3). Inability to record OAEs were mostly due to ossicular disruption proved also by otoendoscopic inspection and operative visualization of the middle ear. Reproduction of OAEs with z50% overall wave reproducibility was considered an indication of an intact ISJ. In conclusion, since recording OAEs was a simple, easy to use, quick, noninvasive technique [8,9], its use in tympanic membrane perforations would help study the status of ISJ and also could provide information as regards the cochlear function in children with ventilation tubes.
References [1] H.C. Richardson, C. Elliott, J. Hill, The feasibility of recording transient otoacoustic emissions immediately following grommet insertion, Clin. Otolaryngol. 21 (1996) 445 – 448. [2] H.E. Cullington, B.U. Kumar, L.M. Flood, Feasibility of otoacoustic emissions as a hearing screening following grommet insertion, Br. J. Audiol. 32 (1998) 57 – 62. [3] F. Zhao, H. Wada, T. Koike, The influence of middle ear disorders on acoustic emissions, Clin. Otolaryngol. 25 (2000) 3 – 8. [4] J.W. Hall, Anatomy and physiology, Handbook of Otoacoustic Emissions, Singular Publishing Group, California, 2000, pp. 29 – 65. [5] H. Daya, A.E. Hinton, P. Radomskiej, Otoacoustic emissions: assessment of hearing after tympanostomy tube insertion, Clin. Otolaryngol. 21 (1996) 492 – 494. [6] R.G. Amedee, The effects of chronic otitis media with effusion on the measurement of transiently evoked otoacoustic emissions, Laryngoscope 105 (1995) 589 – 595. [7] J.J. Owens, M.J. McCoy, B.L. Lonsbury-Martin, G.K. Martin, Otoacoustic emissions in children with normal ears, middle ear dysfunction, and ventilating tubes, Am. J. Otol. 14 (1) (1993) 34 – 40. [8] D.T. Kemp, Stimulated acoustic emissions from within the human auditory system, J. Acoust. Soc. Am. 64 (1978) 1386 – 1391. [9] N.J. Johnsen, C. Elberling, Evoked acoustic emissions from the human ear: I. Equipment and response parameters, Scand. Audiol. 11 (1982) 3 – 12.