Cochlear findings in the white spotting (Ws) rat

White spotting (Ws) rats possess a c-kit gene mutation at the W locus, resulting in a variety of characteristics including a lack of intermediate cells of the stria vascularis. The present study employs a light microscope (LM), scanning (SEM) and transmission electron microscopes (TEM), diaminobenzidine (DAB) staining techniques and auditory brainstem response (ABR) to investigate the structure and function of the cochlea in 26 homozygous Ws/Ws rats aged 1–6 months. A slight thinning of the stria vascularis and moderate elevation of ABR threshold were about the only defects noted in 1 month animals, while older animals displayed various defects that tended to worsen with age. At 3 months LM revealed pigment granules in the basal turn of most animals, with a loss of pigmentation in the upper turns. The stria vascularis and organ of Corti tended to be well preserved in the lower, pigmented portion, while the upper, unpigmented portion showed severe strial degeneration and some outer hair cell loss. DAB staining revealed a well developed strial capillary net throughout the pigmented portion of the cochlea, with severe degradation in the unpigmented apical portion. ABR thresholds were slightly elevated over 1 month values. At 6 months great differences in degeneration were noted between right and left ears of the same animal.     

Cochlear morphology from Würzburg (1951) to Turin (1987): old and new aspects

A review is given of the methods employed in human temporal bone pathology, from the camera lucida drawings of the last century to the sophisticated techniques of today.     

Cochlear nerve demyelination causes prolongation of wave I latency in ABR of the myelin deficient (md) rat

In this study, we examined the auditory brainstem responses (ABRs), distortion product of otoacoustic emissions (DPOAEs) and cochlear morphology of the myelin deficient (md) rat, which completely lacks central myelin but not peripheral myelin. ABRs showed a marked prolongation not only wave II-IV latencies but also wave I latency. Cochlear nerve fibers near the modiolus lost their myelin halfway into the internal auditory canal. DPOAEs also decreased at a lower frequency of the combined tone. Since nerve fibers ending at the apical turn of the cochlea passed through central portion of the cochlear nerve, wave I prolongation of ABRs and decrease of DPOAEs at a lower frequency might originate mainly from the demyelinated CNS part of the cochlear nerve and efferent olivocochlear bundle in the internal auditory canal.     

Cochlear mechanics: coiling effects (I, II) and the absorption equation (III)

Mechanical effects of cochlear coiling are examined by comparing wave propagation in straight and coiled two-dimensional models. (1) Compressional waves PC speed up in the coiled system and PC lambda/4 resonance frequencies differ between models by about 1/2 octave. (2) For transpartitional waves PT, there exists a condition of complete model equivalence. (3) Straight models with equal, instead of equivalent depths underestimate coiled PT speed in the long wave limit. (4) Straight model theory alone fails to predict that there is a special radius relation for maximum coiled PT speed at long wave lengths. (5) The case of near-zero modiolar radius is interesting in connection with responses to the stapes near-field. It is suggested that the simple physical assumption implicit to most PT integration procedures has been, that the longitudinal power flow drops at twice the relative rate of the local fields. Two new equations are obtained: the 'absorption equation' and the equation for 'absorption tonotopy'.     

The University of Melbourne/Cochlear Corporation (Nucleus) program

The Nucleus multichannel cochlear prosthesis has been implanted in over 100 patients. Speech discrimination improved greatly in most patients. Overall, the results with this type of implant are very satisfactory.     

The Auditory Nerve Overlapped Waveform (ANOW) Originates in the Cochlear Apex

Measurements of cochlear function with compound action potentials (CAPs), auditory brainstem responses, and otoacoustic emissions work well with high-frequency sounds but are problematic at low frequencies. We have recently shown that the auditory nerve overlapped waveform (ANOW) can objectively quantify low-frequency (<1 kHz) auditory sensitivity, as thresholds for ANOW at low frequencies and for CAP at high frequencies relate similarly to single auditory nerve fiber thresholds. This favorable relationship, however, does not necessarily mean that ANOW originates from auditory nerve fibers innervating low-frequency regions of the cochlear apex. In the present study, we recorded the cochlear response to tone bursts of low frequency (353, 500, and 707 Hz) and high frequency (2 to 16 kHz) during administration of tetrodotoxin (TTX) to block neural function. TTX was injected using a novel method of slow administration from a pipette sealed into the cochlear apex, allowing real-time measurements of systematic neural blocking from apex to base. The amplitude of phase-locked (ANOW) and onset (CAP) neural firing to moderate-level, low-frequency sounds were markedly suppressed before thresholds and responses to moderate-level, high-frequency sounds were affected. These results demonstrate that the ANOW originates from responses of auditory nerve fibers innervating cochlear apex, confirming that ANOW provides a valid physiological measure of low-frequency auditory nerve function.     

Cochlear and vestibular functions of the rat after obliteration of the endolymphatic sac

A combined morphological and physiological study on the effect of saccus obliteration on the cochlea and the vestibular labyrinth of the rat is presented. Endolymphatic hydrops was successfully induced in 49% of the animals. It was frequently associated with fistulae of the membranous wall and degenerative changes in the organ of Corti and spiral ganglion. In hydropic ears electrocochleography revealed a CAP threshold increase only in those cases where hydrops was associated with loss of hair cells and ganglion cells. In two of these animals also an increased negative SP was present. Static otolith reflexes were found to be normal in all hydropic ears despite severe lesions of the saccule in some of these. Abnormal canal reflexes measured by electronystagmography and cupulometry were established in animals with hydrops of the semicircular canals and in one animal with a fistula of the saccule.     

人工耳蜗技术报告( Ⅳ):手术及术后调试

1人工耳蜗手术与许多外科术式一样,手术医生在人工耳蜗植入术中采用的技巧和方式不尽相同。但人工耳蜗术式有一些基本原则。主要有:①尽可能地将电极无创地插入到鼓阶中;②将装置安放在头的外侧,并避免日后的创伤;③确保装置和电极阵列位置牢固,防止移位。目的是在不损伤周围组     

Functional morphology of stria vascularis after treatment with ethacrynic acid or atoxyl (author's transl)

Surface alterations of the stria vascularis and Reissner's membrane were studied in guinea pigs following intravenous or intraperitoneal administration of ethacrynic acid or atoxyl. DC-potential was measured in the same animals during intoxication. In addition we studied changements in potassium concentration (perilymph, endolymph) of the atoxyl-treated animals.     

L-型钙通道阻滞药尼福地平对耳蜗功能的影响

目的　探讨L -型钙通道阻滞药尼福地平对豚鼠耳蜗功能的影响。方法　 4 6只健康杂色豚鼠随机分为四组 ,分别全耳蜗灌注含 0 .15、0 .5、3μmol L尼福地平的人工外淋巴液及不含尼福地平的人工外淋巴液 (对照组 ) ,灌流前及灌流 12 0min后圆窗记录耳蜗微音电位 (cochlearmicrophonics ,CM)和耳蜗听神经复合动作电位 (com poundactionpotential,CAP)。比较各组相同时间点的CM振幅和CAP阈值。结果　人工外淋巴液组 (对照组 )灌流后CAP阈值无改变 (P >0 .0 5 ) ,其余组灌流后CAP阈值均升高 (P <0 .0 5 ) ,并随浓度增加阈移增大。灌流后各组CM振幅与 10 0dB声强度时CM振幅比较的相对振幅均下降 ,随浓度增加CM振幅下降更明显。 6只灌流 3μmol L尼福地平的豚鼠 30min后CAP阈值升高 ,CM振幅下降 ,改为单纯人工外淋巴液灌流 90min后 ,CAP阈值及CM振幅有部分恢复。结论　尼福地平对耳蜗功能有抑制作用且有剂量依赖性和部分可逆性 ,间接证明耳蜗毛细胞上存在L-型Ca2 + 通道     

Cochlear blood flow in the rat. A methodological evaluation of the microsphere method

With the microsphere method it is possible to quantify the blood flow in various organs. The blood flow in the cochlea is only a very small part of the cardiac output and only relatively few microspheres are caught in this organ, which necessitates large groups of animals for such studies. The method has, however, not been fully evaluated for studies of small organs in small animals. In this study, 130 rats of various ages with normal or arterial hypertension were investigated. The blood flows of 97 animals were possible to evaluate. It was found that physiological parameters, such as PCO3, pH, PO2 and mean arterial blood pressure within the rather wide limits usually present in the anesthetized animal did not affect the cochlear blood flow to any great extent and that the method is feasible for studies of the blood flow through the inner ear in small animals.     

表没食子儿茶素没食子酸酯对噪声性耳蜗损伤的影响

目的 探讨表没食子儿茶素没食子酸酯(epigallocatechin-3-gallate,EGCG)对噪声性耳蜗损伤的影响.方法 45只豚鼠随机分为EGCG+噪声组、生理盐水+噪声组、正常对照组,每组15只.EGCG+噪声组和生理盐水+噪声组豚鼠在接受噪声暴露(120 dB SPL, 4 h)前一日及每次暴露前1 h分别腹腔注射EGCG(25 mg/1 000 g)和等量生理盐水,正常对照组不予任何处理.噪声暴露后即刻和第1、3、7、14天检测三组豚鼠听性脑干反应(ABR),第14天分离各组豚鼠耳蜗,行耳蜗基底膜、血管纹铺片及免疫组化染色,观察各组豚鼠耳蜗基底膜、血管纹细胞形态及外毛细胞运动蛋白(Prestin)、3-硝基酪氨酸(3-NT)分布的变化.结果 噪声暴露后,EGCG+噪声组各时间点的ABR反应阈均高于对照组,但低于生理盐水+噪声组,从第3天开始,与两组间ABR反应阈差异缩小,但差异仍有统计学意义(均为P<0.05).免疫组织化学染色显示,正常对照组Prestin蛋白显绿染的耳蜗三排外毛细胞排列整齐,无细胞缺失,3-NT主要分布于毛细胞胞质及表皮板;与生理盐水+噪声组相比,噪声暴露后,EGCG+噪声组豚鼠外毛细胞形态较好,Prestin染色清晰;基底膜、血管纹处损伤轻,细胞排列规则,3-NT分布减少.结论 预防性腹腔注射EGCG可减轻噪声引起的耳蜗损伤,对噪声性听力损伤有一定的防护作用.     

Cochlear developmental defect and background-dependent hearing thresholds in the Jackson circler (jc) mutant mouse

Jackson circler (jc) is a spontaneous, recessive mouse mutation that results in circling behavior and an impaired acoustic startle response. In this study, we refined the phenotypic and genetic parameters of the original jc mutation and characterized a new mutant allele, jc(2J). In open-field behavior tests, homozygous jc mutants exhibited abnormal circling and ambulatory behavior that was indistinguishable from that of phenotypically similar mutants with defects in the vestibule of the inner ear. The jc/jc and jc(2J)/jc(2J) mice had stable elevated auditory-evoked brainstem response (ABR) thresholds at the 16kHz stimulus of 88+/-9dB sound pressure levels (SPL) and 43+/-11dB SPL, respectively. Peak latencies and peak time intervals were normal in jc mutants. The jc mice showed no measurable distortion-product otoacoustic emissions (DPOAEs) above the system noise floor. In the mutant cochlea, the apical turn failed to form due to the developmental growth arrest of the cochlear duct at the level of the first turn at gestational day 13.5. In a large intrasubspecific intercross, jc localized to a 0.2cM interval at position 25cM on chromosome 10, which is homologous to the human 6q21 region. On CZECHII/Ei and CAST/Ei backgrounds jc/jc mutant hearing thresholds at the 16kHz stimulus were significantly lower than those observed on the C57BL/6J background, with means of 62+/-22dB SPL and 55+/-18dB SPL, respectively. Genome-wide linkage scans of backcross, intercross, and congenic progeny revealed a complex pattern of genetic and stochastic effects.     

Cochlear administration of adenosine triphosphate facilitates recovery from acoustic trauma (temporary threshold shift)

BACKGROUND: Adenosine triphosphate (ATP) has often been used in the treatment of acoustic trauma although evidence supporting its clinical use was lacking. The aim of this study was to evaluate the chronic effects of ATP on acoustic trauma in guinea pigs. METHODS: We infused ATP into the perilymph of the guinea pig cochlea concurrently with intense noise exposure to investigate the effect of ATP on the process of recovery after acoustic trauma. We assessed auditory brainstem response (ABR) thresholds to evaluate cochlear function. RESULTS: After noise exposure (120 dB SPL, 5 h), ABR thresholds showed an increase of approximately 50 dB SPL that returned to normal after 14 days. Cochlear function in ATP-treated ears recovered more quickly than in control ears. The effect of ATP was inhibited by the administration of the ATP receptor antagonist: pyridoxal- phosphate-6-azophenyl-2',4'-disulfonic acid. CONCLUSION: These results suggest that ATP mitigates the effects of noise trauma through the ATP receptor.     

The use of the Cochlear Mini Microphone (MM) as a personal radio system (FM) with young children who are deaf

Objectives: This paper describes the background, organization and findings of a project undertaken in 2016-2017, to examine the benefits and challenges of the use of the Cochlear Mini Microphone (MM) by the families of pre-school children with cochlear implants on the Nottingham Auditory Implant Programme.

Methods: The experiences and views of 25 families who used the equipment were obtained and analysed. The information informed subsequent advice, patient literature and professional training.

Results: The MM was viewed to be of benefit by just under half of the families. The attitudes and technical competence of families and local professionals, alongside the age and lifestyle of the children, were identified as the key factors affecting the amount of use.

Conclusion: The insights gained into the challenges and benefits of the MM for this population offered explanations for the limited take-up of the equipment and informed ways to encourage appropriate use

Discussion: Equipment issued to very young children works best alongside specific advice and training, targeted at both families and local professionals. Despite some technical limitations, the availability of a personal radio system was found to be of benefit by some families. It encouraged consideration by both families and professionals, of the potential benefits of early introduction of a personal radio system into pre-school group activities and educational settings.     

Significance of Auditory Evoked Responses (EABR and P300) in Cochlear Implant Subjects

An electrically derived auditory brainstem response (EABR) was recorded intra-operatively, and the event-related potential (P300) postoperatively in post-lingually deaf adult cochlear implantees. EABR and P300 were recorded from two groups of 25 subjects each. All subjects had a cochlear mini-22 system implanted at our center between 1994 and 1998. Two parameters of EABR, threshold (T) and the gradient of the amplitude-growth (AG) curve, were used for correlation with postoperative speech reception scores. The consonant recognition score (CRS) measured 1 month postoperatively showed a significant correlation with the AG curve of EABR (Spearman rank order test, p=0.004), but not at later points in time. No correlation was found between the T and CRS at any time postoperatively. As the AG curve reflects the number of remaining spiral ganglion cells in the inner ear, a large number of surviving neurons is thought to be advantageous only for initial speech learning. The latency of P300 was measured for correlation with the speech reception score. The division of the cochlear implant subjects into a fair and a good hearing group according to their CRS showed that the average latency of P300 was significantly longer for the fair hearing group than for the good hearing group. A follow-up study showed that P300 latency significantly correlated with CRS measured at 6 months, 1 year and at a later time. As the latency of P300 is thought to reflect the time for sound processing in the central auditory system, our results indicate that plasticity of the central auditory system is more important than that of the peripheral auditory system for speech learning in cochlear implant subjects.     

使用人工耳蜗和助听器的语前聋儿童言语识别能力的研究

目的 通过对使用人工耳蜗和助听器的语前聋儿童的言语识别能力的比较研究,为人工耳蜗植入适应证提供参考.方法实验对象包括18例人工耳蜗植入和40例配戴助听器的先天性语前聋儿童,先在自由声场测试双耳裸耳听阈,根据装置使用时间和平均裸耳听阈值分组,测试并比较使用人工耳蜗和助听器的语前聋儿童封闭项的声母、韵母、单音节词识别率.结果人工耳蜗植入时间≥2年组儿童的韵母、声母和单音节词识别率明显高于＜2年组患者.助听器使用时间≥2年组的各测试项识别率与＜2年组差异无统计学意义.装置使用时间＜2年的语前聋儿童,人工耳蜗植入者的各测试项识别率均明显高于平均裸耳听阈＞100 dB HL的助听器使用者,与平均裸耳听阈≤100 dB HL的助听器使用者的各测试项识别率差异均无统计学意义.装置使用时间≥2年的语前聋儿童,人工耳蜗植入者的各测试项识别率均明显高于平均裸耳听阈＞90 dB HL的助听器使用者,但与平均裸耳听阈＞70 dB HL但≤90 dB HL的助听器使用者差异无统计学意义.结论极重度语前聋儿童人工耳蜗植入后能获得比助听器使用者更好的言语识别能力.     

Cochlear blood flow in the rat. A comparison of 10- and 15-micron spheres

The microsphere method combined with surface preparation dissection is described for measuring cochlear blood flow in the rat. Two sphere sizes, 10 and 15 micron, were compared. No difference between the two sizes was found for measuring total cochlear blood flow. Shunting of the 10-micron spheres appeared to be similar to shunting of the 15-micron spheres and thus was minimal. However, the 15-micron spheres distributed poorly to the apical cochlea, especially the spiral portion. The 10-micron sphere was less toxic, allowing larger numbers of spheres to be infused. Consequently, more 10-micron spheres lodged in the cochlea, which is important for reducing random error. For these reasons, we recommend the 10-micron sphere, as opposed to the 15-micron sphere, for studying cochlear blood flow in the rat.