Musculotubal canal approach for stenotic Eustachian tube
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Eustachian tube
Atelectasis
Perforation
Abstract Introduction Retraction pocket is a condition in which the eardrum lies deeper within the middle ear. Its management has no consensus in literature. Objective To assess the role of mastoidectomy in the management of retraction pockets added to a tympanoplasty. Methods Prospective study of patients with retraction pocket and referred to surgery. The patients were randomly assigned to two groups: one managed with tympanoplasty and mastoidectomy and the other group with tympanoplasty only. The minimum follow-up considered was 12 months. The outcomes were: integrity of eardrum, recurrence, and hearing status. Results This study included 43 patients. In 24 cases retraction occurred in the posterior half of the eardrum, and in 19 patients there was clinical evidence of ossicular interruption. The two groups of treatment were composed by: 21 patients that underwent tympanoplasty with mastoidectomy and 22 patients had only tympanoplasty. One case of the first group had a recurrence. In 32 cases patients follow up was longer than 48 months. The average air-bone gap changed from 22.1 dB to 5 dB. The percentage of air-bone gap improvement was assessed at 60% in those patients treated with mastoidectomy, and 64.3% in those without it (p > 0.5). Conclusion Tympanoplasty and ossiculoplasty should be considered to treat atelectatic middle ear and ossicular chain interruption. Mastoidectomy as a way to increase air volume in the ear seems to be a paradox; it does not add favorable prognostic factor to management of retraction pockets.
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Because of Eustachian tube controls middle ear pressure to maintain the best hearing level, we tested the equilibration capacity of the Eustachian tube by measuring hearing levels in a soundproof pressure chamber. The number of swallows to recover normal hearing after the chamber pressure reached -200 mm H2O (an index of equilibration capacity for the static pressure differences across the eardrum) was less than 9 in normal subjects. The worst level of hearing and the time required to recover normal hearing from the beginning of alteration in the chamber pressure to -700 mm H2O (indexes of equilibration capacity for dynamic pressure differences across the eardrum) were 0-17 dB and within 120s in normal subjects. It was difficult to determine definitive normal ranges of the equilibrium capacity of the Eustachian tube when positive pressure was applied.
Eustachian tube
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A study was conducted to describe a probe microphone assembly to monitor sound pressures at the eardrum for hearing conservation. The probe microphone assembly permitted the uncertainty in probe-tip position to be eliminated and the transfer function to the eardrum to be estimated. The device was attached to an ear mold designed to self-locate within the concha and ear canal and position the probe tip reproducibly. The device consisted of a miniature probe microphone and a customized ear-mold. The ear mold was fabricated from an ear impression that was obtained for each subject following established audiological procedures. The ear impression provided the contour of the perimeter of the concha and cymba, which was required to produce the 'C'-structure used to position the ear mold external to the ear canal.
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This publication contains a review of several acoustic investigations in which the effects of probe location on real-ear gain were examined through theoretical models based on acoustic properties of the average human ear and ear simulator studies. The results of these investigations are used to demonstrate the effect of standing waves and eardrum impedance on probe measurements made in the ear canal. Investigations were also conducted in the sound field with a KEMAR manikin. A commercial probe microphone system was used to measure the SPL and real-ear gain at various locations within the KEMAR ear canal. The results emphasize the critical effect of probe location on absolute or relative ear canal measurements and indicate the necessity to establish clinical procedures for probe measurements based on relevant acoustic principles.
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Acoustic impedance
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The 23 known cartilage tympanoplasty methods to reconstruct the eardrum are classified in six main groups. Each method is briefly defined, described, and illustrated: Group A: Cartilage tympanoplasty with palisades, stripes, and slices. The eardrum is reconstructed by several, various, full‐thickness pieces of cartilage with attached perichondrium on the ear canal side. In this group six different methods are described. Group B: Cartilage tympanoplasty with foils, thin plates, and thick plates, not covered with the perichondrium. In this group four methods are included. Group C: Tympanoplasty with cartilage‐perichondrium composite island grafts. The perichondrium flap suspends or fixates the cartilage. In this group four methods are included. Group D: Tympanoplasty with special total pars tensa cartilage‐perichondrium composite grafts. All three methods are used to close a total perforation, but differ from each. Three special methods are included in this group. Group E: Cartilage‐perichondrium composite island grafts tympanoplasty for anterior, inferior, and subtotal perforations. Two on‐lay and two underlay methods are included. Group F: Special cartilage tympanoplasty methods: The cartilage disc is placed under the perforation, the perichondrium onto the denuded eardrum remnant.
Perichondrium
Perforation
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As part of the development of an acoustical manikin, an artificial ear was designed to simulate the mechanical and acoustical properties of the external ear, up to and including the impedance of the eardrum. The sensing element is a B&K 4132 electrostatic microphone terminating a simulated ear canal with an acoustical impedance-matching network that, combined with the microphone, furnishes the eardrum impedance. The canal proper has dimensions approximating those of the real ear and is placed inside a skull of polyester-impregnated fiberglass, provided with a plastisol pinna of realistic dimensions and texture. The head is mounted on a fiber torso. The new artificial ear is suitable for testing all types of receivers and ear enclosures under realistic conditions. The inner portion of the artificial ear is made of reproducible metallic components, making it suitable for consideration as an artificial-ear standard.
Human ear
Acoustic impedance
Pinna
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The response of a hearing aid is affected by many factors which include the head and outer ear, the microphone, amplifier, and receiver used in the hearing aid, the properties of the ear canal and the eardrum, and acoustic feedback through the vent. This article presents a computer simulation of an in-the-ear (ITE) hearing aid that includes all of the above factors. The simulation predicts the pressure at the eardrum for a frontal free-field sound source. The computer model was then used to determine the effects on the hearing aid response due to variations in the size of the ear canal. The simulation indicates that, for an unvented hearing aid, changes in the size of the ear canal shift the overall sound-pressure level at the eardrum but have only small effects on the shape of the frequency response. The situation is more complicated when a vent is present, however, since changes in the size of the ear canal that cause apparently small perturbations in the acoustic feedback signal may, nonetheless, have large effects on the overall system response.
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Outer ear
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Sound pressure distributions in the human ear canal, whether unoccluded or occluded with ear molds, were studied using a probe tube technique. On average, for frequencies below 6 kHz, the measuring probe tube had to be placed within 8 mm of the vertical plane containing the top of the eardrum (TOD), determined optically, in order to obtain sound pressure magnitudes within 6 dB of ‘‘eardrum pressure.’’ To obtain that accuracy in all of the eight subjects studied, the probe had to be within 6 mm of the TOD. Since probe location relative to the drum has to be known, a purely acoustic method was developed which can be conveniently used to localize the probe-tip position, utilizing the standing wave property of the sound pressure in the ear canal. The acoustically estimated ‘‘drum location’’ generally lay between the optically determined vertical planes containing the TOD and the umbo. On average, the ‘‘drum location’’ fell 1 mm medial to the TOD. Of the 32 estimates made acoustically in various occluded and unoccluded conditions in 14 subjects, 30 estimates lay within a ±2-mm range of this average.
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This paper describes central and peripheral eustachian tube function in relation to tympanoplasty. Central obstruction of the eustachian tube at the pharyngeal orifice is frequently correctable and is not a contraindication to tympanoplasty, whereas chronic cicatricial peripheral obstruction of the eustachian tube at the isthmus is a contraindication to tympanoplasty. These findings are based on tubal patency pressure studies measured with a mercurial manometer with the patient performing the Valsalva maneuver, with catheterization of the eustachian tube, and with politzerization. If the patient can autoinflate the middle ear and if the eustachian tube will open with politzerization, then the likelihood exists that there is no peripheral obstruction of the eustachian tube and you have a good candidate for tympanoplasty. When there is a perforation of the ear drum, the best test for eustachian tube function is microscopic examination of the middle ear mucosa. If the middle ear mucosa is perfectly normal, then you know that you have good eustachian tube function and can proceed with the tympanoplasty.
Eustachian tube
Contraindication
Promontory
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