Sensorineural hearing loss after vibration: an animal model for evaluating prevention and treatment of inner ear hearing loss

Sensorineural hearing loss following a variety of acoustic trauma, including middle ear surgery, is well known. Current literature, which points to the deleterious influence of noise on the inner ear during surgery, has yet to assess the influence of vibration generated by the burr. The purpose of the study reported here was to establish an animal model that mimics drilling and can be used to explore methods of hearing loss prevention and treatment. A specially developed electromagnetic vibrator was calibrated and used in 59 guinea pigs to induce hearing loss. Both young and old guinea pigs were used. The bony external ear canal of guinea pigs were exposed to vibration or sound of varying duration and intensity. The vibration of the temporal bone and noise level in the middle ear were measured. Electrocochleography was recorded to evaluate the hearing loss. Among the young animals, 90% developed a significant threshold shift (TS > 20 dB), when vibrated with 250 Hz at an intensity of 6.2 m/s2 for 15 min. An average of 42 dB TS was observed. With 10 min exposure 63% showed a TS. The older animals vibrated for 5 min developed the same TS (mean TS 34 dB) as the young animals when vibrated for 10 min. The vibration-induced TS showed no recovery within 3 days of observation. In the contralateral ear 4 out of 5 animals showed TS > 20 dB. When exposed to sound levels exceeding the vibration-generated sound in the middle ear (119 dB at 250 Hz) only 2 out of II animals (18%) showed TS. The frequency of TS and level of TS were significantly greater in the vibrated animals than in sound-only exposed animals (p < 0.01). The degree of vibration-induced TS in the present animal model could be controlled by vibration intensity and duration. The older animals were more susceptible to vibration-induced inner-ear damage than younger animals. This model will be used in further studies to find methods for prevention and treatment of hearing loss during ear surgery.     

Vibration-induced hearing loss: mechanical and physiological aspects.

HYPOTHESIS: The sensorineural hearing loss (HL) after middle ear surgery has been explained by the noise generated by drilling, without considering the vibration generated by the burr. BACKGROUND: The role of temporal bone vibration in the etiology of the HL was evaluated. METHODS: An electromagnetic shaker was used to vibrate the bony external ear canal of guinea pigs at different frequencies ranging from 32 to 1,000 Hz and at intensities ranging from 4.2 to 18.8 m/s for 15 minutes. The hearing threshold was measured with auditory evoked responses. A total of 30 animals were tested. RESULTS: After vibration, 60% of the guinea pigs developed a threshold shift (TS) exceeding 10 dB at two frequencies, with average TS of 8.8 dB across all frequencies and animals. The exposure to vibration at higher frequencies (range, 500-1,000 Hz) produced stronger TS than did the exposure to lower frequencies (range, 32-250 Hz). The vibration-induced TS showed prominent recovery so that after 7 days, TS was 2.4 dB on average and 27 of 30 animals had recovered. After 14 days, the TS was 1.3 dB. The vibration excitation measurements showed that at lower frequencies, the vibration transmission into the skull was significantly greater than at higher frequencies, at which the transmission was heavily attenuated. There were no acoustic resonances detected in the skull. The frequency of vibration and the hearing frequency in auditory brainstem response were significant determinants in the model explaining the vulnerability of vibration on hearing. Hearing loss primarily occurred at higher frequencies. The HL was mostly reversible, consistent with the results observed after human temporal bone surgery. CONCLUSION: We conclude that in the guinea pig model, the temporal bone vibration at higher frequencies produced a more severe HL than did the vibration at lower frequencies, although the vibration at higher frequencies caused less efficient transmission from the vibrating probe to the temporal bone. The guinea pig model may be useful in the development of surgical techniques and in the understanding of temporal bone pathology.     

The medial cochlear efferent system does not appear to contribute to the development of acquired resistance to acoustic trauma

Noise-induced hearing loss (NIHL) was compared between sound conditioned and unconditioned guinea pigs, in which the left ear in both groups had been perfused with strychnine. Animals in the conditioned group were subjected to moderate sound (85 dB SPL broadband, 5 h/day, 10 days) and then exposed to intense sound (110 dB SPL broadband, 5 h). Unconditioned animals were exposed only to the intense sound. Following intense sound exposure, strychnine-treated ears showed greater NIHL than untreated ears in both unconditioned and conditioned animals, demonstrating the role of the medial efferents to reduce NIHL. Conditioned animals, however, showed smaller hearing loss and cochlear damage in both strychnine-treated and untreated ears compared to unconditioned animals; the protective effects given by conditioning were equivalent between the strychnine-treated and untreated ears. These results suggest that, although the medial efferent system acts to attenuate NIHL, it may not be necessary for the acquired resistance to NIHL provided by conditioning.     

KHRI-3 monoclonal antibody-induced damage to the inner ear: antibody staining of nascent scars

Intracochlear infusion of the KHRI-3 monoclonal antibody results in in vivo binding to guinea pig inner ear supporting cells, loss of hair cells and hearing loss. To further characterize the basis for KHRI-3-induced hearing loss, antibody was produced in a bioreactor in serum-free medium, affinity purified, and compared to conventionally prepared antibody by infusion into the scala tympani using mini-osmotic pumps. In vivo antibody binding was observed in 10 of 11 guinea pigs. A previously unreported pattern of KHRI-3 antibody binding to cells involved in scar formation was noted in five guinea pigs. All but one of the KHRI-3-infused animals demonstrated a hearing loss of > 10 dB in the treated ear. In five of 11 animals the threshold shift was 30 dB or more, and all had hair cell losses. In one guinea pig infused with 2 mg/ml of antibody, the organ of Corti was absent in the basal turn of the infused ear. This ear had a 45-50 dB threshold shift but, curiously, no detectable antibody binding in the residual organ of Corti. Organ of Corti tissue was fragile in antibody-infused ears. Breaks within the outer hair cell region occurred in 5/11 infused ears. The contralateral ears were normal except for one noise-exposed animal that demonstrated hair cell loss in the uninfused ear. Three animals were exposed to 6 kHz noise (108 dB) for 30 min on day 7. Antibody access to the organ of Corti may be increased in animals exposed to noise, since the strongest in vivo binding was observed in noise-exposed animals. Loss of integrity of the organ of Corti seems to be the primary mechanism of inner ear damage by KHRI-3 antibody. The binding of KHRI-3 antibody in new scars suggests a role of the antigen in scar formation. Antibodies with binding properties similar to KHRI-3 have been detected in 51% of patients diagnosed with autoimmune sensorineural hearing loss; thus, it seems likely that such autoantibodies also may have pathologic effects resulting in hearing loss in humans.     

Effect of steroids on increased permeability of blood vessels of the stria vascularis after auditory ossicle vibration by a drill in otologic surgery

OBJECTIVES: The vibration caused by drills used for middle ear surgery is considered one of the causes of postoperative sensorineural deafness. Seki et al reported that when drill-induced damage was created in the auditory ossicles of guinea pigs, permeability across the capillary vessels in the stria vascularis increased significantly with the duration of drill-induced vibration. The present study was undertaken to examine changes in permeability across the stria vascularis capillaries following vibration in experimental animals pretreated with steroids, with the goal of developing a method of preventing a vibration-induced increase in permeability across these capillaries. METHODS: After an intravenous dose of hydrocortisone and horseradish peroxidase, the auditory ossicles of guinea pigs were vibrated with a drill for 60 seconds. RESULTS: Intravenous steroid administration before vibration reduced the leakage of horseradish peroxidase from the stria vascularis capillaries after vibration. CONCLUSIONS: The findings suggested that steroids suppress the increase in permeability across the stria vascularis capillaries that results from drill-induced vibration.     

Math1基因内耳导入后噪声性聋豚鼠听功能改变观察

目的观察Math1基因内耳导入对噪声性聋豚鼠听功能的影响,探讨Math1基因过表达对噪声损伤耳蜗的生物学效应,为内耳基因治疗提供实验基础和理论依据。方法经脉冲噪声致聋的豚鼠45只（各频率ABR阈值均≥95dB SPL）,雌雄不限,实验开始时体草250～300g。随机分为3组：Ad—Math1-EGFP组（30只）;Ad—EGFP组（5只）;空白组（10只）。各组豚鼠在基因转导后4周、8周分别测试双耳ABR。测试完毕后处死动物,观察听泡及耳蜗尤炎性病变者记录听阈结果。结果Math1导入后4周,导入耳各频率ABR阈值低于对照耳（右耳）,也低于Ad—EGFP组及空内组,平均达到85dBSPL。Math1导入后8周,导入耳各频率ABR阂值低于对照耳（右耳）,也低于Ad—EGFP组及空白组,与4周时比较,进一步好转,平均达到75dB SPL。结论Math1基因内耳导入可使噪声导致全聋的豚鼠听功能部分恢复,为噪声性聋的治疗打开了新的思路和手段。     

A study on the effect of infrasound

In order to examine the influence of infrasound that is becoming topical in society, human beings and guinea pigs were exposed to infrasound. After exposure, the hearing level, vestibular functions and autonomic nervous functions of human beings were examined, and endocochlear potential (EP) and cochlear microphonics (CM) of guinea pigs were examined. Next, after guinea pigs were exposed to intense audible low frequency sound that was born secondarily from infrasound and/or vibration of whole body concerning about air pressure change of infrasound, their EP and CM were examined. The results obtained were as follows: 1) By exposure of infrasound 10-15Ha 130-135dB LSPL for 30min. to human beings, their hearing level, vestibular functions and autonomic nervous functions were not changed. 2) After exposure of infrasound 15Hz 135-140dB LSPL for 24hrs.-72hrs. to guinea pigs, their EP and CM remained normal. 3) After each exposure of audible low frequency sound 90Hz 120dB SPL for 72hrs., 150Hz 110dB SPL for 72hrs. and 200Hz 100dB SPL for 72hrs. to guinea pigs, their EP became abnormal though their CM remained normal. 4) After exposure of 15Hz 500 mu +/- 30 mu vibration for 72hrs. to guinea pigs, both EP and CM remained normal. 5) After exposure of both audible low frequency sound 150Hz 100dB SPL and vibration 15Hz 500 mu +/- 30 mu for 72hrs. to guinea pigs, their EP became abnormal though their CM remained normal.     

氢气对噪声性聋的有效防护时间及机制研究

目的近年研究表明氢气对噪声性聋具有良好的预防作用,但其对噪声性聋预防作用持续时间尚不明确,本实验通过建立豚鼠噪声性聋模型探索氢气预防作用持续时间及防护机制。方法选用听力正常的豚鼠30只,随机等分为氢气组和噪声组,氢气组在首次脉冲噪声暴露前给予1h氢气吸入,两组动物随后每隔两小时重复施加脉冲噪声(峰值声强为163dB SPL);实验动物每次暴露后即刻行ABR测听,重复相同剂量脉冲声直至ABR听阈≥90dB。所有实验动物在噪声暴露结束后1天、3天、7天、14天行ABR测听,结束后处死动物,取材观察透射电镜及病理组织染色。结果噪声组动物在噪声暴露2h(即2×8次脉冲暴露)后监测听力,半数致聋(听阈≥90 dB SPL);氢气组,此时间推迟至4h左右且基底膜Myosin-7a荧光强度高于噪声组,底回外毛细胞丢失数量少于噪声组(P=0.03<0.05);氢气组豚鼠耳蜗底回基底膜带状突触数量减少但仍高于噪声组(P=0.65>0.05);透射电镜观察氢气组豚鼠半结形态好于噪声组。结论给予1次氢气预防的有效持续时间为2-4h,氢气对脉冲声造成的内耳毛细胞、突触、半节损伤均具有一定的保护效果。     

Hearing loss induced by viscous fluids in the middle ear

Dextran solutions of low viscosity (7.5 centipoise) and high viscosity (2.2 poise) were instilled in turn into the middle ears of guinea pigs, using an open bulla preparation. The degree of conductive hearing loss induced was assessed by measurement of the cochlear microphonic. Both solutions produced a comparable degree of hearing loss which was frequency dependent, ranging from 30 dB at 500 Hz to almost zero at 4000 Hz. The results indicate that the degree of conductive hearing loss produced by a serous effusion in otitis media is due solely to an effect on compliance in the middle ear and is independent of the viscosity of the effusion.     

HDAC2对豚鼠急性听力损失治疗中糖皮质激素抵抗的影响

目的：观察地塞米松（dexamethasone ,DEX）加氨茶碱（amionophylline ,AMI）治疗脂多糖（lipopo‐lysaccharide ,LPS）诱导的豚鼠急性听力损失的疗效及耳蜗组蛋白去乙酰化酶2（histone deacetylase 2,HDAC2）的表达,探讨治疗中 HDAC2对糖皮质激素（glucocorticoid ,GC）抵抗的影响。方法选取50只健康白色豚鼠,其中10只为对照组,仅双耳鼓阶注入5μl人工外淋巴液（artificial perilymph ,AP）（AP组）;其余40只鼓阶注入5μl（5 mg／ml）的LPS后再随机分为4组,每组10只：模型组（LPS组）,无其他处理;LPS＋DEX组：术前30 min及术后24小时腹腔注射DEX 1 mg／kg ;LPS＋AMI组：术前30 min及术后24小时腹腔注射AMI 20 mg／kg ;LPS＋DEX＋AMI组：术前30 min及术后24小时腹腔注射AMI 20 mg／kg及DEX 1 mg／kg。所有动物给药前及鼓阶注射术后48小时行ABR检测后取耳蜗,采用免疫荧光法,观察耳蜗基底膜铺片及耳蜗组织冰冻切片中HDAC2的分布及空间定位,用ELISA法测定耳蜗组织中HDAC2的含量。结果 LPS组鼓阶注射LPS后48小时全频听力损失,由低频向高频逐渐加重;LPS＋DEX组及LPS＋ AMI组16、32 kHz ABR阈移较LPS组改善明显（＜0．05）,LPS＋DEX＋AMI组各频率ABR阈移均低于LPS＋DEX组（P＜0．05）,以16 kHz处最显著（P＜0．01）。耳蜗基底膜铺片及耳蜗冰冻切片免疫染色结果表明HDAC2广泛分布于耳蜗中,且主要存在于胞核内。8、16、32 kHz ABR阈移与耳蜗内HDAC2的含量呈负相关（P＜0．05）。结论 AMI可提高豚鼠耳蜗HDAC2的表达,HDAC2可改善治疗中GC抵抗,对提高GC治疗L PS导致的急性听力损失的敏感性有一定的作用。     

不同强度冲击波负压暴露后豚鼠听力损失特点

目的探讨冲击波负压(blastunderpressure,BUP)暴露引起的豚鼠听力损失特点。方法豚鼠暴露于不同强度BUP之前和暴露后不同时间,检测听性脑干反应(ABR)和40Hz听觉相关电位(AERP)反应阈。结果冲击波负压峰值为-15.6~-18.2kPa时,在BUP暴露后豚鼠ABR阈值大多没有明显变化。当暴露的BUP峰值为-22.4~-78.4kPa时,BUP暴露后2h~30d各组动物的ABR反应阈值均有不同程度升高;ABR阈值升高幅度与负压峰值的大小密切相关,即暴露的负压峰值越强,豚鼠的ABR阈移越严重。负压峰值为-44.5~48.8kPa的中等强度BUP暴露后8h测试,3次暴露的动物ABR阈值升高明显高于1次暴露组(P<0.05),而5次暴露组又明显高于3次暴露组。中强度和高强度BUP(-53.6~63.3kPa)暴露后豚鼠40HzAERP测试发现,0.5~8.0kHz各个频率均有较明显的阈移;压力峰值为-76.4~-78.4kPa的极高强度负压暴露后,豚鼠0.5kHz和1.0kHz处的反应阈上升幅度则明显高于8kHz和4kHz处反应阈值(P<0.05)。结论BUP暴露可以引起豚鼠各个频率的听力损失,但以低频损害更为明显;且听力损失程度随着负压强度的增高而加重;中等强度负压重复暴露后,暴露次数越多听力损失越重。     

内耳色素与爆震性听损伤

目的 探讨内耳色素与爆震性听损伤的关系。方法 选用豚鼠４８只，分为：白化豚鼠爆震组，杂色豚鼠爆震组，正常对照组。爆震前及爆震后６小时、１、２、７、１４、２１天测定Ａ、Ｂ组豚鼠ＡＢＲ阈值。处死豚鼠做耳蜗铺片、耳蜗树脂包埋半薄切片、耳蜗扫描电镜制样，观察耳蜗内色素及耳蜗损伤情况。结果 光镜下杂色豚鼠可见耳蜗内色素颗粒，而白化豚鼠未见。爆震后白化豚鼠听力损伤比杂色豚鼠严重，其听力恢复亦较杂色豚鼠慢。爆震     

The Preyer reflex--an easy estimate of hearing function in guinea pigs

Preyer reflex thresholds elicited monaurally by tone bursts from 0.25 to 8 kHz were determined in more than 150 guinea pig ears. Normal reflex thresholds were between 85 and 95 dB SPL in the low and middle frequencies, decreasing to 75 dB in the higher frequencies. The range of measurements at single frequencies usually did not exceed 10 dB. In unselected populations of adult guinea pigs, about half of the animals had increased reflex thresholds--at least unilaterally, in most cases due to middle ear infections. The Preyer reflex showed parallel threshold increase with compound action potential thresholds in conductive loss and recruitment in cochlear hearing loss. Normal Preyer reflex thresholds do not necessarily mean normal hearing, but increased thresholds do indicate hearing impairment. This technique is valuable in the selection and monitoring of animals for otologic experiments.     

噪声性听觉损害的声反射增长函数

目的　探讨噪声暴露对声反射增长函数 (acousticreflexgrowthfunction ,ARGF )的影响。方法　对有长期噪声暴露史的工人 5 7例 (10 6耳 )及正常听力青年人 2 5例 (5 0耳 )进行ARGF测试 ,观察受试耳对 10 0 0Hz纯音刺激级由声反射阈 (acousticreflexthreshold ,ART)水平增加至 12 5dBHL时声抗量值变化的函数关系。根据纯音平均听阈 (pure-tonethresholdaverage ,PTA)将噪声暴露耳分为三组。结果　噪声暴露组的声反射 (acousticreflex ,AR)动态范围变窄 ,声抗增长量值减小 ,ARGF曲线坡度变缓 ,反射振幅及声抗增长量值与正常青年组相比有显著下降 (P <0 .0 1) ,而听力损失程度不同的三个病变组间的差异不显著 (P >0 .0 5 )。分别用声抗量值及声抗量增幅比随AR刺激级的增加而变化两种方法分析所得数据 ,发现噪声暴露组的ARGF与正常耳有明显差别 (P <0 .0 5 ,P <0 .0 1)。结论　噪声暴露对ARGF有显著影响。ARGF可用作监测早期噪声性听觉损害 (noiseinducedhearingloss,NIHL)的敏感指标     

The Auditory Brainstem Response of Aged Guinea Pigs

The Auditory Brainstem Response (ABR) technique was used to investigate potential dysfunctions in the auditory brainstem of the pigmented guinea pig (Cavia porcellus) associated with biological ageing. Animals aged from 58 days to 4 years 3 months were tested. ABRs were recorded at stimulation intensities from 85 dB HL to 10 dB HL. The auditory thresholds were found to undergo marked elevations in old animals, by an average of 32 dB. From the traces obtained, four positive deflection waves were reliably recorded. The latency of each of the four waves was evaluated at different stimulation intensities in guinea pigs of different ages. Although there was a trend for the latencies to increase in old age, these differences were not statistically significant. Similarly, there were no significant age-related changes in the inter-peak intervals. The latency/intensity functions of the four waves produced parallel curves. However, the curve from the old age group was shifted to the right, by an average of 35 dB, indicative of conductive hearing loss. There was no evidence of retro-cochlear hearing loss. Therefore, it appears that the threshold elevations in the old animals can be accounted for by conductive hearing loss, presumably in the middle ear. In 24% of the old animals tested, no ABR could be elicited. It would appear that these animals had suffered severe sensorineural hearing loss.     

New approach for implantable hearing aids: a feasibility study

The objective of this study was to test the feasibility of a new kind of implantable hearing device based on a cerebrospinal fluid hydroacoustic pathway by which sound waves are conducted from the dura mater to the inner ear by cerebrospinal fluid. In this prospective animal study, a piezoelectric bimorph was implanted into 2 guinea pigs and 1 dog between the skull bone and the dura at the parietal area. The bimorph was connected transdermally by wires to a click generator. The auditory brain stem response was recorded after stimulation of the piezoelectric device by the click generator. In the 3 animals, the auditory brain stem response could be recorded in response to a stimulus intensity of 135 dB peak equivalent (pe) sound pressure level (SPL; instrument setting), corresponding to 3.8 V activating the device. The auditory brain stem response disappeared during white noise masking, proving that the origin of the response was in the inner ear. The threshold was 125 and 115 dB pe SPL in the 2 guinea pigs and 135 dB pe SPL in the dog (instrument setting). We conclude that transmission of sound waves by a cerebrospinal fluid hydroacoustic pathway to the inner ear is possible. Such a device would have advantages over more traditional implantable hearing devices: it would not be necessary to couple it to the ossicular chain, and it could be used in patients with infected middle ears.     

Mechanisms of Tympanic Membrane and Incus Mobility Loss in Acute Otitis Media Model of Guinea Pig

Acute otitis media (AOM) is a rapid infection of middle ear due to bacterial or viral invasion. The infection commonly leads to negative pressure and purulent effusion in the middle ear. To identify how these changes affect tympanic membrane (TM) mobility or sound transmission through the middle ear, we hypothesize that pressure, effusion, and structural changes of the middle ear are the main mechanisms of conductive hearing loss in AOM. To test the hypothesis, a guinea pig AOM model was created by injection of Streptococcus pneumoniae. Three days post inoculation, vibration of the TM at umbo in response to input sound in the ear canal was measured at three experimental stages: intact, pressure-released, and effusion-drained AOM ears. The vibration of the incus tip was also measured after the effusion was removed. Results demonstrate that displacement of the TM increased mainly at low frequencies when pressure was released. As the effusion was removed, the TM mobility increased further but did not reach the level of the normal ear at low frequencies. This was caused by middle ear structural changes or adhesions on ossicles in AOM. The structural changes also affected movement of the incus at low and high frequencies. The results provide new evidence for understanding the mechanism of conductive hearing loss in AOM.     

锌,铁预防豚鼠钻井井场噪声性听力损失的实验观察

为观察给予饲料中添加锌,铁喂养豚鼠,采用听性脑干反应(ABR)和耳蜗电图(EcochG)及扫描和透射电镜技术观察,在钻井井场柴油机旁噪声[102 dB(A)]暴露下豚鼠听功能和耳蜗毛细胞的变化.结果表明,当脱离噪声后听力逐渐恢复,于第7d组可见明显恢复.耳蜗毛细胞改变明显减轻,并逐渐恢复正常.而喂普通饲料组未见恢复.证明锌、铁能有效地防治钻井井场噪声所致的听力损伤.     

Severe acoustic trauma in adult rats induced by short duration high intensity sound

CONCLUSION: Short duration high intensity sound (SDHIS) induced severe functional damage in adult rats. OBJECTIVE: Previous reports showed that SDHIS induced severe histological changes in the cochleae of guinea pigs. This study examined the hearing functions of rats exposed to SDHIS. MATERIALS AND METHODS: Animals were exposed for 1 min to a 137 dB sound pressure level (SPL) broadband noise. Auditory functions of the experimental animals were assessed using an auditory brainstem response (ABR) measurement system at frequencies of 8, 16, and 32 kHz before and 14 days after exposure to SDHIS. RESULTS: After SDHIS, none of the experimental animals showed any response when stimulated by maximum SPLs at all frequencies of our ABR system.     

耳蜗振动创伤后血迷路屏障变化的磁共振成像表现

目的 在动物模型中探讨电钻振动诱导听力减退的机制和可能的血迷路屏障变化。方法 用电磁振荡器在5只豚鼠听泡上产生可重复的振动，其振动频率为250Hz，用复合动作电位评估其听功能，振动后3小时至4天用4．7特斯拉磁共振成像分析其血迷路屏障变化。静脉注射T1增强剂Gadolinium-diethylenetriaminepentaacetate-bismethylamide （Gd-DTPA-BMA）作为血迷路屏障的示踪剂。结果 振动诱导平均听力损失40dBHL，在振动后立即测试的耳蜗中．其中阶摄取Gd-DTPA-BMA，提示血迷路屏障通透性增加。在振动后2天至4天的动物中，其中阶内无Gd-DTPA-BMA摄取。结论 250Hz振动使血路屏障通透性增加是使导致听力减退的原因之一。其通透性的变化为一个可逆的过程。