豚鼠外淋巴瘘对畸变产物耳声发射的影响

为观察豚鼠外淋巴瘘造模后畸变产物耳声发射（ＤＰＯＡＥ）的变化，选用１１只豚鼠右耳为实验耳，手术建立蜗窗外淋巴瘘。在实验前、打开听泡、蜗窗膜造瘘、缝合伤口及外淋巴瘘造后１８天，均以２ｆ１－ｆ２ＤＰＯＡＥ的幅值记录其变化。测试完毕后豚鼠耳蜗行火棉胶包埋切片，观察形态学改变。结果发现在形成蜗窗膜外淋巴瘘前后ＤＰＯＡＥ幅值变化差异有显著性（Ｐ＜０．０１），１８天后蜗窗膜愈合者ＤＰＯＡＥ幅值明显提高，接近实验前，而未愈合者则下降明显。病理检查见Ｃｏｒｔｉ器正常，愈合的蜗窗膜有上皮增生，肉芽及纤维母细胞。豚鼠形成外淋巴瘘后ＤＰＯＡＥ幅值明显下降，愈合后又上升，提示ＤＰＯＡＥ可作为外淋巴瘘辅助诊断的手段之一。     

士的宁阻断橄榄耳蜗束对豚鼠畸变产物耳声发射的影响

为探讨豚鼠听觉中枢对畸变产物耳声发射（ＤＰＯＡＥ）的影响，利用士的宁阻断听觉系统的传出神经，系统观察了阻断前后ＤＰＯＡＥ的变化。结果发现在本实验条件下，所有豚鼠均可引出ＤＰＯＡＥ，在同等刺激强度和Ｌ１＝Ｌ２的情况下，低频ｆ０＝１００６Ｈｚ的ＤＰＯＡＥ强度大，而较高频ｆ０＝２０１１和ｆ０＝４０３３的ＤＯＰＡＥ强度较小。士的宁阻断橄榄耳蜗束对ＤＰＯＡＥ无影响，提示在正常神经张力下中枢不参与、不影响ＤＯ     

卡因酸耳蜗毒性的电生理学研究

目的：观察谷氨酸类受体激动剂卡因酸（ＫＡ）对豚鼠耳蜗的毒性作用。方法：健康杂色豚鼠８只，每只动物经圆膜给予６０ｍＭ ＫＡ１μｌ，于用药前及用药后１２ｈ分别检测听神经复合动作电位（ＣＡＰ），耳蜗微音电位（ＣＭ）和畸变产物耳声发射（ＤＰＯＡＥ）之２ｆ２－ｆ２。结果：用药后ＣＡＰ明显下降或消失（Ｐ〈０．００１），而ＣＭ和ＤＰＯＡＥ无明显变化。结论：ＫＡ对初级听觉传入神经末梢具有选择性毒性作用。     

畸变产物耳声发射临床应用价值的探讨

研究了７３例（１３９耳）纯音听阈正常耳及各种感音神经性聋耳的ＤＰＯＡＥ，发现ＤＰＯＡＥ对耳蜗功能异常的改变早于纯音测听，并可精确地反映耳蜗毛细胞在相关频率上的功能状态；ＤＰＯＡＥ幅值及引出率随纯音听阈的提高而下降，当纯音听阈＞５０ｄＢ（ＨＬ）时，ＤＰＯＡＥ幅值明显降低或缺失；蜗后病变耳ＤＰＯＡＥ正常，当蜗后病变累及耳蜗时，ＤＰＯＡＥ幅值可异常，其异常程度与纯音听阈不平行。认为ＤＰＯＡＥ有广泛临床应用价值。     

畸变产物耳声发射对侧抑制效应的临床应用价值

目的：为观察畸变产物耳声发射（ＤＰＯＡＥ）对侧抑制效应的临床应用价值。方法：研究以白噪声为对侧声刺激,对１７例正常人（３４耳）,１３例蜗性聋（１３耳）,９例蜗后聋（９耳）进行了ＤＰＯＡＥ及其对偶抑制效应测试。结果：蜗性聋耳的ＤＰＯＡＥ幅值较正常耳显著下降（Ｐ〈０．０１）,对偶抑制效应减弱,但与正常人差异无统计学意义（Ｐ〉０．０５）,蜗后聋耳ＤＰＯＡＥ幅值高于正常耳（Ｐ〉０．０５）,对侧抑制效应显著     

外淋巴钙离子对畸为产物耳声发射的影响

目的 研究外毛细胞运动产生畸产产物耳声发射（ＤＰＯＡＥ）的机理。方法 观察９只豚鼠（１１耳）采用无钙和有钙的人工外淋巴灌流外淋巴腔后ＤＰＯＡＥ的变化。结果 用无钙人工外淋巴灌流后ＤＰＯＡＥ的均值从４１．３ｄＢＳＰＬ降至１３．７ｄＢＳＰＬ，再用正常钙浓度的外淋巴灌流后又可回升到３６．７ｄＢＳＰＬ结论 ＤＰＯＡＥ的产生需外淋巴强正常浓度的钼离耿必要条件。提示外毛细胞在产生ＤＰＯＡＥ中并非以毛细胞的电运     

正常清醒豚鼠的畸变产物耳声发射特性

目的 研究正常清醒豚鼠的畸变产物耳声发射（ＤＰＯＡＥ）的特性。方法 采用ＣＥＬＥＳＴＡ ５０３型耳声发射分析仪对２６只正常清醒豚鼠（３５耳）进行ＤＰ图及ＤＰ输入／输出曲线（ＤＰ－Ｉ／Ｏ）的测试，随机选择１１只正常清醒豚鼠（２０耳）进行ＤＰＯＡＥ的重复测试，用ＳＰＳＳ１０．０对数据进行统计分析。结果 在ＤＰ图中，当初始音强度Ｌ１／Ｌ２为 ７０／６５ ｄＢ ＳＰＬ时，正常清醒豚鼠的 ＤＰＯＡＥ幅值随测试频率ｆ０从０．７５－８ｋＨｚ的增加而逐渐升高（２７．９０±１．９６－5０．６５±０．７１）。在 ＤＰ－Ｉ／Ｏ中，当ｆ０分别为４、６、８ ｋＨｚ时，正常清醒豚鼠的ＤＰＯＡＥ幅值随Ｌ１／Ｌ２从７０／６５以５ｄＢ－挡降至１５／１０ ｄＢ ＳＰＬ而呈线性下降（Ｐ＜０．０１），在Ｌ１／Ｌ２为５５／５０或６０／５５ ｄＢ ＳＰＬ处出现饱和或低谷，同一Ｉ／Ｏ曲线上Ｌ１／Ｌ２分别从７０／６５及５５／５０ ｄＢ ＳＰＬ递减至阈值的Ｉ／Ｏ斜率（分别记为ＫＴ及ＫＬ）均接近于１，且ＫＬ大于ＫＴ（Ｐ＜０．０１）。重复测试的ＤＰＯＡＥ幅值差异小（＜ １ｄＢ ＳＰＬ）且无统计学意义（Ｐ＞０．０５）。结论 正常清醒豚鼠ＤＰＯＡＥ测试充分表现了其捡出率高、反应幅值大     

外淋巴钙离子对畸变产物耳声发射的影响

目的研究外毛细胞运动产生畸变产物耳声发射（ＤＰＯＡＥ）的机理。方法观察９只豚鼠（１１耳）采用无钙和有钙的人工外淋巴灌流外淋巴腔后ＤＰＯＡＥ的变化。结果用无钙人工外淋巴灌流后ＤＰＯＡＥ的均值从４１．３ｄＢＳＰＬ降至１３．７ｄＢＳＰＬ，再用正常钙浓度的外淋巴灌流后又可回升到３６．７ｄＢＳＰＬ。结论ＤＰＯＡＥ的产生需外淋巴中正常浓度的钙离子为必要条件。提示外毛细胞在产生ＤＰＯＡＥ中并非以毛细胞的电运动性机制起作用，而是与一般肌纤维相似的收缩机理起作用，需要钙离子的中介。     

豚鼠噪声暴露后畸变产和耳声发射及神经元特异性烯醇化酶表？…

为观察豚鼠暴露于强噪声后畸变产物耳声发射（ＤＰＯＡＥ）及神经元特异性烯醇化酶（ＮＳＥ）的变化，选用１３只Ｐｒｅｙｅｒ’ｓ反射正常的健康豚鼠，分为二组，８只噪声暴露组，５只为ＮＳＥ表达对照组。噪声强度１１５ｄＢ（Ａ），连续暴露４小时，ＤＰＯＡＥ幅值于噪声暴露前后者测试，结果ＤＰＯＡＥ幅值噪声暴露前后差异明显（Ｐ〈０．００１），豚鼠内耳内，外手细胞及螺旋神经细胞胞浆、隧道贯穿纤维ＮＳＥ免疫组化反应均呈     

切断听神经对豚鼠DPOAE的影响

利用手术切断听的方法分离中枢与外周耳蜗的神经联系，观察分离前后ＤＯＡＥ的变化。在本实验条件下，所有豚鼠均可引出ＤＰＯＡＥ，在同等刺激强度和Ｌ１＝Ｌ２的情况下，低频ｆｏ＝１００６Ｈｚ的ＤＰＯＡＥ强度大，而较主频ｆ０＝２０１１和ｆ０－４０３３Ｈｚ的ＤＰＯＡ强度较小，切断听神经对ＤＰＯＡＥ无影响，无噪声状态下中枢不参与、不影响ＤＰＯＡＥ的产生和形成，打开豚鼠骨大泡，可引起ＤＰＯＡＥ明显下降，经分析发现主     

Effects of middle ear application of Cipro HC Otic Suspension in an animal model

The objective of this study was to examine whether ciprofloxacin-containing otic drops (Cipro HC Otic Suspension; 0.2% ciprofloxacin, 0.1% hydrocortisone; Alcon, Ontario, Canada) are cochleotoxic in the chinchilla animal model. Five chinchillas in total underwent these studies. Pretreatment distortion-product otoacoustic emissions (DPOAEs) were measured in each ear, followed by a random injection of Cipro to one ear and normal saline to the other. Injections consisted of 0.2 mL into the middle ear cavity (bulla) for 5 consecutive days. Post-treatment DPOAEs and auditory brainstem responses were measured at 1 month, and cochlear hair cell integrity was assessed by scanning electron microscopy (SEM). All animals had normal pretreatment DPOAEs. One month after Cipro instillation, DPOAE levels decreased in three of the animals. No significant change was seen in the ears treated with saline. On SEM examination, the integrity of the stereocilia of the inner and outer hair cells demonstrated no histologic evidence of significant cochlear damage. The finding of reduced DPOAEs suggests a mild local middle ear inflammation caused by the ciprofloxacin or some other component or property of Cipro.     

Distortion product otoacoustic emmissions in Ménière's disease

Distortion product otoacoustic emissions (DPOAEs) are an objective, non-invasive measure for evaluating outer hair cell (OHC) activity. In this study DPOAEs were measured in 70 patients affected by Meniere's disease (MD). In addition 58 out of 70 patients performed both an audiometric threshold evaluation pre- and postglycerol administration (i.e. glycerol test) and DPOAEs pre- and post-osmotic drug assumption. The purpose of this combined form of testing was to explore the effects of glycerol on the active non-linear mechanisms of the cochlea. More than 60% of the ears with MD emitted DPOAEs despite the presence of an average hearing threshold level above 40 dB (HTL). Changes in the DPOAE baseline measures were observed in 32.4% of cases after glycerol administration. Patients were divided in four groups according to the different pattern of DPOAEs shown after the glycerol test. In particular, three-quarters of cases showed a significant increase in DPOAE amplitude, one-quarter of patients, who initially did not express DPOAEs, eventually did after intake of the osmotic agent, while no decreased DPOAEs were observed in these series. The different expressions of DPOAEs should be associated with the evolutive phases of MD. In addiction, elucidation of the relationship between DPOAEs and the stages of MD was an outcome of this test.     

Hemoconcentration as a possible pathogenic factor of sudden hearing loss

Hemodilution is considered to be a useful therapy for sudden hearing loss by improving cochlear blood flow (COBF) as a result of decreasing viscosity of the whole blood. The purpose of this investigation was to evaluate whether hemoconcentration actually leads to a diminished COBF and impaired function of the cochlea to thus play a role in the pathogenesis of sudden hearing loss. Ten New Zealand White rabbits were anesthetized and ventilated. Cochlear function was evaluated by measuring distortion products of otoacoustic emissions (DPOAEs) at the beginning of each experiment and after 120 min. In the interim, each test animal’s hematocrit was raised by an infusion of packed red cells. Control animals were not infused, so hematocrits were left unchanged. Reproducibility of DPOAE measurements were found to be dependent upon the stimulus level. Correlation coefficients were 0.83 for 65 dB SPL and 0.78 for 45 dB SPL. Although no changes in the absolute level of DPOAEs were observed after raising the hematocrit, correlation coefficients were diminshed to 0.68 at 65 dB SPL and 0.58 at 45 dB SPL. Hemoconcentration caused no apparent changes in the cochlear function in our animals. Although these findings may reflect species differences, hemoconcentration might still be a factor causing sudden hearing loss in older, atherosclerotic patients. Received: 17 July 1996 / Accepted: 12 December 1997     

A model for perilymphatic fistula induced hearing loss in the guinea pig cochlea

In cases of sudden, reversible hearing loss where perilymphatic fistulas are thought to be the cause, a multitude of causes have been postulated. These include perilymphatic pressure changes, Simmons' double-break theory, perilymphatic hemorrhage, pneumolabyrinth, and others. This study was proposed to explore the role pneumolabyrinth may have in this pathology. Guinea pigs were fitted with cochlear perfusion pumps pumping artificial perilymph into the left scala tympani. One group of animals received a bubble ( approximately 1.5-2 microl) introduced into the scala tympani while the other group of animals received continuous infusion of artificial perilymph. The animals' cochlear function was monitored using distortion product otoacoustic emissions (DPOAEs) while the animals' behavior was assessed to evaluate for vestibular dysfunction. While unaffected by pump surgery, animals that received air into the scala tympani had their DPOAEs eliminated by day 2 after pump placement. On day 6, positional changes in the DPOAEs were observed where the left lateral decubitus position showed a sharp demarcation at 4 kHz, where lower DPOAE frequencies were abolished and higher ones minimally affected, with DPOAEs normal in the prone position. By days 8 and 20, DPOAEs recovered to normal amplitudes. Vestibular dysfunction was never detected in any animal that received a pneumolabyrinth. All control animals receiving a continuous perilymph infusion exhibited no loss of cochlear function throughout the testing period. The reversible nature of pneumolabyrinth induced hearing loss and the pneumolabyrinth's sole presence (without other possible causes of hearing loss, such as pressure differentials or round window membrane perforations) are powerful indicators of the role of air in the pathology of perilymphatic fistulas. In addition, the fluctuation of the hearing loss with positional changes supports the use of positional audiometry when evaluating perilymphatic fistulas.     

Effects of industrial noise exposure on distortion product otoacoustic emissions (DPOAEs) and hair cell loss of the cochlea--long term experiments in awake guinea pigs

Distortion product otoacoustic emissions (DPOAEs), a sensitive detector of outer hair cell (OHC) function, cochlear microphonics (CM), and hair cell loss have been monitored in 12 awake guinea pigs before and after 2 h exposure to specific, played-back industrial noise (105 dB SPL maximal intensity). All animals had stable DPOAE levels before noise exposure. In the first hours after noise exposure DPOAE levels were reduced significantly. In about 70% a partial recovery of the DPOAEs was found within 4 months after noise exposure. In 16% of the investigated ears no recovery of DPOAEs was observed. However, in a few ears increased DPOAEs were observed after noise exposure. Exposure to industrial noise caused both morphological changes in the middle turns of the cochlea and electrophysiological changes in the middle frequency range. A close correlation existed between reduced DPOAE levels, loss in CM potentials, and area of damaged or lost OHCs, but not with the numbers of damaged or lost OHCs in the cochlea. It can be concluded that continuous industrial noise causes a damage to OHCs which differs form the damage caused by impulse noise.     

Cochlear ischemia induced by circulating iron particles under magnetic control: an animal model for sudden hearing loss

PURPOSE: To correlate the absence of distortion-product otoacoustic emissions observed in sudden hearing loss (SHL) with a possible thromboembolic vascular cause, using an animal model. BACKGROUND: Distortion-product otoacoustic emissions (DPOAEs) are sensitive to cochlear disorders and are absent in cochlear injury. In a previous study, the authors showed that 75% of patients with SHL who have no measurable emissions do not recover hearing. The underlying cause of the loss of emissions is unknown, but it may be secondary to cochlear ischemia. METHODS: Six New Zealand white rabbits underwent unilateral cochlear embolization through the use of circulating iron particles under magnetic control. Cochlear function was monitored through DPOAE recordings of the experimental and control ears. Results: In all animals, a rapid decrease in emissions was noted, which fluctuated but returned to baseline within 2 hours to 3 weeks after embolization, leaving no measurable residual defects. The DPOAEs were suppressed by 5 to 19 dB within 10 minutes of injection of iron solution and magnet placement. The lowest emissions were obtained at 30 minutes and again at 120 minutes, which were 12 to 37 dB below preembolization levels. Two animals returned to baseline DPOAE levels at 1 to 3 weeks, with no identifiable residual deficits. CONCLUSION: It is likely that the loss of emissions seen in the present study is related to cochlear ischemia. The early suppression of DPOAEs in the rabbit cochlea after embolization may parallel that in SHL patients with absence of DPOAEs on presentation.     

Short-term pathophysiologic changes and histopathologic findings of the auditory pathway after closed head injury, using a rabbit model

Hearing impairment is a well-known consequence of closed head injury (CHI). The aim of this study was to elucidate the pathogenesis of CHI-induced hearing loss, using a rabbit model. Twelve New Zealand white rabbits were divided into two groups of 6. In the first group, CHI was induced mechanically, whereas the rabbits of the second group served as controls. Baseline distortion product otoacoustic emissions (DPOAEs), contralateral suppression (CS) of the DPOAEs and auditory brainstem response (ABR) were obtained. The same measurements were performed in the first group after CHI. Three hours later, the animals were sacrificed and their brain was excised and subjected to histopathologic examination. Mean I-III ABR latencies were increased and DPOAE amplitudes and CS values were reduced in the trauma group after CHI, at a statistically significant level. Histopathologic examination of the temporal lobe and brainstem showed multiple hemorrhagic and necrotic areas, with edema in the surrounding region. The vestibulocochlear nerve was severely damaged at its emerging site at the brainstem. In conclusion, both peripheral and central involvement of the auditory pathway was found after CHI. Otoacoustic emissions in conjunction with ABR may provide significant information on both peripheral and central auditory function.     

水杨酸钠对豚鼠畸变产物耳声发射的影响

本文以10％水杨酸钠400mg／kg经豚鼠腹腔注射2小时和4天后,进行较系统的畸变产物耳声发射（DPOAE）测试,并以自身为对照,探讨用药前后水杨酸钠对豚鼠DPOAE的影响。结果发现,用药2小时和4天后,水杨酸钠具有对DPOAE相似的影响作用;水杨酸钠在低刺激强度下可明显降低DPOAE的测出率;对各频率DPOAE的幅值和阈值分别有降低和升高的作用,前者降低2～6dB,后者升高3～9dB,均以低频为甚;水杨酸钠对DPOAE的潜伏期和增长率无明显影响。提示水杨酸钠主要影响DPOAE的发生过程,而对发生后的DPOAE特性影响不大。通过对水酸钠对耳蜗机械特性影响的分析,认为该结果符合水杨酸钠主要影响耳蜗及毛细胞生理功能的药理学特点,可能为其可逆性耳毒性的耳蜗机制之一,有助于解释耳蜗性聋和耳鸣的发病机制。     

Distortion product otoacoustic emissions and tympanometric measurements in an adult population-based study

OBJECTIVE: Otoacoustic emissions (OAEs) are useful clinical tools that can be used as a test to reflect hearing, especially cochlear function. When OAEs are recorded, the sound energy is conducted inwards and outwards through the middle ear system, but the degree to which the middle ear condition affects the OAEs level remains obscure. The objectives of the present study were to estimate the effect of the condition of the middle ear expressed by multifrequency tympanometry on the distortion product otoacoustic emissions (DPOAEs) adjusting for age and the corresponding pure-tone thresholds. SUBJECTS AND METHODS: The evaluation was conducted using 1,043 subjects without a history of ear disease or occupational noise exposure out of a population-based sample of 2,259 adults aged 40-82 years. Multifrequency tympanometry, DPOAEs, and pure-tone audiometry were administered. The resonance frequency (RF), static admittance (SA) and tympanometric peak pressure (PP) were taken as variables representing middle ear function. Subjects were categorized into three groups of variables < or = 5th percentile, between 5th and 95th percentile, and > or = 95th percentile. The signal-to-noise ratio in DPOAE levels were compared among three groups adjusting for age and the pure-tone threshold level. RESULTS: Both abnormally high and low RF exerted a negative effect on DPOAEs. Smaller RF values were related to smaller DPOAEs for the frequency around 1000 Hz, and greater RF values were related to smaller DPOAEs for the frequency around 4000 Hz. The tendency was similar between genders. Abnormally high SA had a negative influence on DPOAEs, while abnormally low SA had no significant effect on either gender. Smaller PP values were significantly related to smaller DPOAEs. CONCLUSIONS: We interpreted the findings of the present study as verification of the effect of the condition of the middle ear on DPOAEs after adjustment for age and the pure-tone threshold level, although ears out of normal range in tympanometric variables might conceivably include not only middle ear dysfunction but also inner ear abnormality. Tympanometric assessment must always be taken into account when OAEs are analyzed for an estimation of the cochlea function.