Effects of conductive hearing loss on temporal aspects of sound transmission through the ear

Effects of conductive hearing loss on level and spectrum are well known. However, little is known about possible additional effects on temporal aspects of sound transmission. This study investigated effects of earplugs and middle ear effusions on amplitude and timing of cochlear microphonic (CM) responses in gerbils. Bilateral CM responses to pure tones (1-16 kHz) were monitored before and after (i). unilateral earplug insertion or (ii). injection of silicone oil, of various viscosities, into one middle ear. Earplugs produced flat hearing losses (mean 13 dB) and delayed CMs more at lower (mean 80 micros, 1-6 kHz) than at higher (20 micros, 8-16 kHz) frequencies. Effusions also produced flat hearing loss. On average, high viscosity effusions produced larger hearing losses (36 dB) than medium (25 dB) or low (20 dB) viscosity effusions. Low and medium viscosity effusions delayed responses to lower (mean 82 and 65 micros respectively, 1-6 kHz) more than to higher (mean 20 and 10 micros respectively, 8-16 kHz) frequencies. High viscosity effusions produced smaller delays across all frequencies (mean 31 micros, 1-16 kHz). In normal animals, CM responses were not delayed over a wide range of stimulus levels. Therefore, in addition to attenuation, conductive loss distorts acoustic temporal cues important for hearing.     

Proximal symphalangism and congenital conductive hearing loss: otologic aspects.

OBJECTIVE: Results of stapedectomy are reported in a Belgian 26-year-old woman and two Dutch brothers having the proximal symphalangism syndrome (McKusick 18580). STUDY DESIGN: Case reports are presented. A review of the results of ear surgery for congenital conductive hearing loss in this syndrome is given. SETTING: The Belgian patient was treated in a general hospital. The Dutch patients were treated in a university hospital, which was a tertiary referral center. PATIENTS: Patients were referred to have an evaluation of their hearing impairment. INTERVENTION: Based on the syndromal diagnosis and based on routine audiometric tests, a congenital ossicular fixation was considered to be the cause of the hearing loss. By exploratory tympanotomies, this was confirmed. Reconstructive procedures including stapedotomy were performed. MAIN OUTCOME MEASURES/RESULTS: Long-term audiometric data are presented to evaluate the outcome of the surgical interventions. CONCLUSIONS: Congenital stapes ankylosis eventually combined with a congenital fixation of the short process of the incus in the fossa incudis, causing the congenital conductive hearing loss. Surgical intervention is very successful in most reported cases, but negative side effects are incidentally found as well.     

The neonate has a temporary conductive hearing loss due to fluid in the middle ear

Postnatal functional changes in the activity of the ear and auditory pathway in neonatal guinea pigs [from day of birth (postnatal day, PND = 0), PNDs 1-4, 7 and then weekly up to 7 weeks] were studied as a model of maturation of hearing in human neonates. On the day of birth there were signs of a conductive hearing loss: negative middle ear pressure, auditory nerve brainstem evoked response (ABR) threshold elevation, ABR wave 1 latency prolongation and low amplitude otoacoustic emissions. The conductive hearing loss is probably a result of the (amniotic) fluid found in the neonatal middle-ear cavity. Over the next PNDs, this conductive hearing loss was resolved. In order to confirm this neonatal conductive hearing loss and its resolution, saline was instilled into the middle ear of guinea pigs. This induced signs of a conductive hearing loss similar to those seen in the neonatal guinea pigs which disappeared with clearance of this fluid. Therefore it may be concluded that most of the changes in auditory function seen over the first PNDs are due to absorption of amniotic fluid from the middle-ear cavity.     

Contralateral occlusion test: The effect of external ear canal occlusion on predicting conductive hearing loss

Introduction and objectivesThe contralateral occlusion test (COT) has the potential to allow the quantitative evaluation of unilateral conductive hearing loss. The purpose of this study was to determine the accuracy of the test in predicting the degree of hearing loss.Materials and methodsFifty-three subjects with unilateral conductive hearing loss were recruited from an otolaryngology department of a tertiary hospital. The COT was performed using 128, 256, 512, 1024 and 2048 Hz tuning forks with the non-affected ear canal totally occluded to determine lateralization. Pure-tone audiometry was performed to establish the presence and degree of the air-bone gap (ABG) and the pure-tone average (PTA). The tuning fork responses were correlated with the ABG and the PTA to determine their accuracy.ResultsThe COT showed a better association between hearing loss and the lateralization response using the 512 Hz tuning fork (p = 0.001). The sensitivity of the 512 Hz fork in detecting a PTA of at least 35.6 dB was 94.6% and the specificity was 75.0% for a positive predictive value of 89.7% and a negative predictive value of 85.7%, assuming a pretest prevalence of 69.8%.ConclusionsThe overall accuracy of the COT in predicting the degree of unilateral conductive hearing loss was significant. The COT had significant power in one direction: if lateralization to the affected ear occurred, it was almost certain evidence of a moderate or severe conductive hearing loss.     

DPOAE增长曲线在中耳和耳蜗病变中的应用

DPOAE输入输出函数曲线可以了解耳蜗的非线性,耳蜗障碍输入输出函数曲线陡峭.由于中耳在传导声音过程中是线性的,可以假设DPOAE增长曲线在传导性聋中无改变,而耳蜗损伤发现陡峭的DPOAE输入输出函数曲线,反映了耳蜗感音功能的丧失.     

Middle ear and cochlear disorders result in different DPOAE growth behaviour: implications for the differentiation of sound conductive and cochlear hearing loss

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.     

Effect of conductive hearing loss on the vestibulo-collic reflex

The vestibulo-collic reflex represents a promising test for evaluating the integrity of otolith function. We have investigated the threshold of this response in a group of normal subjects, and the effect of a conductive hearing loss. A positive response was recorded in 31 of 32 normal subjects. The threshold of the vestibulo-collic reflex varied from 80 to 97 dBHL in these subjects with a 95% response rate at a threshold at96 dBHL. A total of 23 ears with a conductive hearing loss in 17 patients were also investigated. The average conductive hearing loss (at 0.5, 1, 2 and 4 kHz) ranged from 8.75 to 40 dBHL (average24.46 dBHL). A positive response was recorded in only two ears. Therefore, the vestibulo-collic reflex has a high stimulus threshold which is dependant on reliable transmission of the click stimulus to the inner ear thus limiting is clinical use.     

Audiological evaluation and self-assessed hearing problems in subjects with single-sided congenital external ear malformations and associated conductive hearing loss

Previously, unilateral hearing impairment (UHI) has been considered of little consequence. However, a recent meta-analysis of children with UHI displayed educational and behavioural problems and possible delays of speech and language development. Further, patients with UHI consequently report hearing difficulties. Our study investigated hearing function, possible inner ear protection, and self-assessed hearing problems in 57 subjects aged between 3–80 years with single-sided congenital ear malformations and conductive UHI. Pure-tone thresholds and speech recognition (quiet, noise) were measured, and all patients completed a self-assessment questionnaire. Pure-tone thresholds corresponding to sensorineural function did not significantly differ between the normal (air conduction) and affected ear (bone conduction). However, speech recognition in both quiet and in noise was normal on the non-affected side but significantly worse on the malformed side. A moderate to high degree of self-assessed hearing problems were reported. In conclusion, hearing function in the affected ear was found to be subnormal in terms of supra threshold signal processing. Furthermore, a high degree of hearing difficulty was reported. Therefore, active treatment, surgery, or hearing amplification, might be considered.     

Audiological evaluation and self-assessed hearing problems in subjects with single-sided congenital external ear malformations and associated conductive hearing loss

Previously, unilateral hearing impairment (UHI) has been considered of little consequence. However, a recent meta-analysis of children with UHI displayed educational and behavioural problems and possible delays of speech and language development. Further, patients with UHI consequently report hearing difficulties. Our study investigated hearing function, possible inner ear protection, and self-assessed hearing problems in 57 subjects aged between 3-80 years with single-sided congenital ear malformations and conductive UHI. Pure-tone thresholds and speech recognition (quiet, noise) were measured, and all patients completed a self-assessment questionnaire. Pure-tone thresholds corresponding to sensorineural function did not significantly differ between the normal (air conduction) and affected ear (bone conduction). However, speech recognition in both quiet and in noise was normal on the non-affected side but significantly worse on the malformed side. A moderate to high degree of self-assessed hearing problems were reported. In conclusion, hearing function in the affected ear was found to be subnormal in terms of supra threshold signal processing. Furthermore, a high degree of hearing difficulty was reported. Therefore, active treatment, surgery, or hearing amplification, might be considered.     

水杨酸钠对噪声性听力损失影响的实验观察

目的　观察水杨酸钠能否减轻噪声引起的听力损失。方法　将 3 6只健康且耳廓反射正常的花色豚鼠随机分为水杨酸钠实验组、生理盐水对照组、水杨酸钠对照组和噪声暴露组。噪声暴露采用 10 5dBSPL的 4kHz窄带噪声下暴露 2h ,连续 5d。水杨酸钠给药为每天 0 5g/kg体重连续10d。由短声诱发听性脑干反应 (auditorybrainstemresponse ,ABR) ,连续测试其阈值 ;而后取动物双侧耳蜗荧光染色后光镜下行毛细胞计数和形态学观察。结果　ABR阈值测试显示 ,实验组动物在噪声暴露结束后 2 4h的听力略好于对照组 ;形态学观察表明 ,实验组细胞核异常数据低于对照组。结论　水杨酸钠可能在一定程度上具有拮抗噪声引起的听力损失及保护耳蜗毛细胞的作用     

Sound amplification negates central effects of a neonatal conductive hearing loss

Neonatal CBA/J mice with external auditory meati removed were raised in a sound-amplified environment. If amplification continued until sacrifice at 24 or 45 days of age, both cochlear nuclear volumes and cross-sectional areas of VCN globular cells were of normal size; without amplification both measurements were significantly reduced.     

Effects of user training with electronically-modulated sound transmission hearing protectors and the open ear on horizontal localization ability

Abstract

Objective: To determine if training with electronically-modulated hearing protection (EMHP) and the open ear results in auditory learning on a horizontal localization task. Design: Baseline localization testing was conducted in three listening conditions (open-ear, in-the-ear (ITE) EMHP, and over-the-ear (OTE) EMHP). Participants then wore either an ITE or OTE EMHP for 12, almost daily, one-hour training sessions. After training was complete, participants again underwent localization testing in all three listening conditions. A computer with a custom software and hardware interface presented localization sounds and collected participant responses. Study sample: Twelve participants were recruited from the student population at Virginia Tech. Audiometric requirements were 35 dBHL at 500, 1000, and 2000 Hz bilaterally, and 55 dBHL at 4000 Hz in at least one ear. Results: Pre-training localization performance with an ITE or OTE EMHP was worse than open-ear performance. After training with any given listening condition, including open-ear, performance in that listening condition improved, in part from a practice effect. However, post-training localization performance showed near equal performance between the open-ear and training EMHP. Auditory learning occurred for the training EMHP, but not for the non-training EMHP; that is, there was no significant training crossover effect between the ITE and the OTE devices. Conclusion: It is evident from this study that auditory learning (improved horizontal localization performance) occurred with the EMHP for which training was performed. However, performance improvements found with the training EMHP were not realized in the non-training EMHP. Furthermore, localization performance in the open-ear condition also benefitted from training on the task.     

Selective aspects of human pathology in high-tone hearing loss of the aging inner ear

Accompanied with aging, the thresholds for high frequency sounds may elevate and result in a progressive hearing loss described as presbycusis. Based on correlations between audiometric measures of aged patients and histologic findings garnered from postmortem examinations, four types of presbycusis have been characterized: sensory-neural, neural, strial, and conductive [Schuknecht, H.F., Gacek, M.R., 1993. Ann. Otol. Rhinol. Laryngol. 102, 1--16]. Otopathologic changes to the inner ear as a direct function of age, however, remain controversial. The focus of this investigation involves the pathological impact on remaining sensory structures in patients having sensory--neural degeneration. The current study presents seven human temporal bones extracted from patients aged 53--67 years with high-tone hearing loss and with no known history of extraordinary environmental events involving head or noise trauma, acoustic overstimulation, or ototoxicity. In previously published findings of these specimens, all but one temporal bone failed to demonstrate a meaningful correlation between audiometric measurements and loss of functional hair cell populations with secondary retrograde degeneration of nerve fibers. Using the block surface method, electron microscopic micrographs demonstrate ultrastructural changes in the cuticular plate, stereocilia, pillar cells, stria vascularis, and the spiral ligament. In all pathological specimens, the greatest incidence of degeneration was seen at the cuticular plate. Conclusively, our findings present three implications in the aging human cochlea: firstly, audiometric measures that represent a high-tone hearing loss may take various forms with respect to ultrastructural patterns of degeneration and surviving structures; secondly, the incidence of lipofuscin and lysosome granules does not correlate with the degree of hearing loss and; thirdly, as shown only in guinea pigs [Anniko, M., 1988. Scanning Microsc. 2, 1035--1041], high-tone hearing loss can be associated with deformation of the cuticular plate.     

Middle ear osteoma: a rare cause of conductive hearing loss with normal tympanic membrane

Osteomas of the temporal bone are benign osseous tumors usually located to the external auditory canal. Osteomas involving the middle ear are very rare. We report the case of a patient presenting with a progressive hearing loss caused by a middle ear osteoma involving the incus and contiguous to the tympanic segment of the facial nerve. This report highlights the value of CT scan in the work-up of conductive or mixed hearing loss with normal tympanic membrane. The management of middle ear osteoma is discussed.