Some aspects of temporal coding by single cochlear fibres from regions of cochlear hair cell degeneration in the guinea pig.

Some temporal coding properties of cochlear nerve fibers are investigated in kanamycin-treated guinea pigs (GPs) with various degrees of outer hair cell (OHC) degeneration. In particular, the phase locking ability of fibres from pathological cochleas, and also their adaptation properties are compared with the properties of normal cochlear fibres. No systematic effects of OHC loss on these properties have so far been found. These preliminary results therefore suggest (in so far as these animals can be regarded as models of sensorineural hearing loss of cochlear origin in man) that little deterioration should be expected in functions purely dependent upon faithful temporal coding of the stimulus waveform.     

脑膜炎后耳蜗骨化患者人工耳蜗植入的临床分析

目的总结因脑膜炎而致严重感音神经性听力损失的人工耳蜗植入经验,探讨其诊疗策略。方法回顾性分析2010年9月—2020年9月于首都医科大学附属北京同仁医院耳鼻咽喉头颈外科因脑膜炎致重度及极重度感音神经性听力损失进行人工耳蜗植入的22例患者资料,其中成人13例,儿童9例。对其术前影像学、手术所见进行分析。结果颞骨HRCT检查中16例(72.7%)诊断耳蜗骨化;6例(27.3%)未诊断,但经手术探查证实存在耳蜗骨化。18例内耳MRI检查中,3例(16.7%)未发现耳蜗信号改变,而经手术探查存在耳蜗骨化。两者结合后检出率为90.9%(20/22),20例(90.9%)可见合并半规管等其他迷路病变。术中未见耳蜗骨化者1例(4.5%),圆窗骨化7例(31.8%),耳蜗底转骨化14例(63.6%)。电极完全植入者18例(81.8%),部分植入者4例（18.2%）。结论脑膜炎后耳蜗骨化可致严重感音神经性听力损失,人工耳蜗是理想的治疗策略,建议尽早植入。术前颞骨HRCT和MRI对确定是否适合耳蜗植入和术前计划至关重要,诊断存在假阴性,但联合检查可大大提高耳蜗骨化的术前诊断阳性率。     

Relation between outer hair cell loss and hearing loss in rats exposed to styrene

The relationship between outer hair cell (OHC) loss and cochlear sensitivity is still unclear, because in many animal models there exist surviving but dysfunctional OHCs and also injured/dead inner hair cells (IHC). Styrene is an ototoxic agent, which targets and destroys OHCs starting from the third row to the second and first rows depending on the exposure level. The remaining cells may be less affected. In this experiment, rats were exposed to styrene by gavage at different doses (200-800mg/kg/day) for varying periods (5 days/week for 3-12 weeks). An interesting finding was that the cochlear sensitivity was not affected in a few rats with all OHCs in the third row being destroyed by styrene. A further loss of OHCs was usually accompanied with a linear input/output (I/O) function of cochlear compound action potentials (CAP), indicating the loss of cochlear amplification. However, normal CAP amplitudes at the highest stimulation level of 90dB SPL were often observed when all OHCs were destroyed, indicating normal function of the remaining IHCs. The OHC-loss/hearing-loss relation appeared to be a sigmoid-type function. Initially, styrene-induced OHC losses (<33%) did not result in a significant threshold shift. Then CAP threshold shift increased dramatically with OHC loss from 33% to 66%. Then, CAP threshold changed less with OHC loss. The data suggest a tri-modal relationship between OHC loss and cochlear amplification. That is, under the condition that all surviving OHCs are ideally functioning, the cochlear amplifier is not affected until 33% of OHCs are absent, then the gain of the amplifier decreases proportionally with the OHC loss, and at last the amplifier may fail completely when more than 67% of OHCs are lost.     

Successful cochlear implantation in Langerhans cell histiocytosis: A rare case

An 8-year-old girl presented with a 1-year history of bilateral progressive hearing loss and vertigo for 6 months. High-resolution computed tomography of the temporal bones demonstrated multiple lytic lesions. Histopathology examination confirmed a diagnosis of Langerhans cell histiocytosis (LCH). She underwent chemotherapy for 12 months. Following treatment, she was in remission. However, the bilateral profound sensorineural hearing loss persisted. She underwent right cochlear implantation with very good functional audiological outcomes. This is the first known reported case of successful auditory rehabilitation through cochlear implantation in a patient with bilateral profound hearing loss due to isolated bilateral temporal bone LCH.     

The Sharpening of cochlear frequency selectivity in the normal and abnormal cochlea

In the normal (anaesthetized) animal cochlea, the frequency threshold curves for single primary fibres are up to an order of magnitude sharper than the analogous functions derived from various reported measurements of the basilar membrane amplitude of vibration. This enhanced neural frequency selectivity is found in the same species and under conditions similar to those in which the mechanical measurements are taken. The sharpening process (at least near threshold) appears to be linear and is not dependent upon lateral inhibitory mechanisms. The variability of the neural frequency selectivity and its vulnerability to metabolic, chemical and pathological influences suggests the hypothesis that the sharpening is due to some form of ‘second filter’ subsequent to the relatively broadly tuned basilar membrane.

All fibres recorded from in the cochlear nerve in the normal cochlea show this enhanced frequency selectivity; in contrast, in pathological cochleas, all fibres, or a substantial proportion, have high-threshold, broadly tuned characteristics, approximating to those of the basilar membrane.

The frequency selectivity of normal cochlear fibres is adequate to account for the analogous psychophysical measures of hearing. It is proposed that loss of this normal frequency selectivity occurs in deafness of cochlear origin, accounting for widening of the critical band. A new hypothesis for recruitment is proposed on this basis.

Finally, invetigations of the cochlear nerve fibre frequency responses under conditions of hypoxia give grounds for the speculation that more than one mechanism is involved in the excitation of a single fibre, related to the separate functioning of the inner and outer hair cells.     

Bilateral cochlear implantation in bilateral Langerhans cell histiocytosis

Abstract

Background

Langerhans’ cell histiocytosis (LCH) is a rare proliferative disorder that can have otologic manifestations in up to 30% of patients. Treatment of local and systemic disease may include medical, surgical, and radiation therapies. Involvement of the temporal bone can lead to conductive and, rarely, sensorineural hearing loss. Post-labyrinthectomy cochlear implantation can be an effective treatment option for sensorineural hearing loss in the setting of persistent LCH.

Methods

A retrospective case review at a tertiary academic medical center. Hearing in Noise Test (HINT) performed before and after bilateral cochlear implantation was examined.

Results

Following bilateral partial labyrinthectomy, post-operative testing showed a HINT in quiet of 17%. Left-sided cochlear implant followed by immunosuppressive therapy for persistent disease showed marked improvement with post-operative HINT in a quiet room of 80% and 63% at 1 and 2 years. Fifty-five months after left implantation, and 10 months after right cochlear implantation, binaural post-operative HINT in quiet was 81%.

Conclusion

Surgical excision of LCH lesion remains a mainstay of treatment for temporal bone involvement. Bilateral cochlear implant with adjuvant immunosuppression in our patient demonstrated both immediate and delayed improvement in auditory function after staged cochlear implantation in the setting of persistent disease.     

人工耳蜗植入术后改良耳蜗位平片的探讨

目的 探讨改良后耳蜗位平片摄影位的临床应用价值。方法 21例人工耳蜗植入术后患儿(年龄30d～4岁)分别摄许氏提倡的耳蜗位平片摄影位和我们改良后的许氏耳蜗位平片摄影位,用Cohen(c)方法测出蜗管内电极数,将术中得数与2种片所得共3组数据行统计处理t检验。结果 2种平片均能清晰地显示蜗管内电极的位置和形态,2组X片结果与手术结果基本吻合,3组数据比较差异无统计学意义。结论 改良后耳蜗位平片摄影位方法简便,易使4岁以下患儿接受,且能满足了解人工耳蜗植入术后精确状态的需要。     

人工耳蜗植入术前的影像学检查

目的 :探讨CT和MRI检查对人工耳蜗植入术前评估的价值。方法 :对 2 6例感音性耳聋患者均采用颞骨轴位高分辨率CT螺旋扫描、MR水成像及内耳三维重建。结果 :1 8例先天性感音性耳聋患儿中检出Mondini畸形Ⅰ型 1例 (2耳 ) ,Ⅱ型 1例 (2耳 ) ,内耳纤维化 1例 (2耳 ) ;5例语后聋患者中检出慢性化脓性中耳炎 1例 (2耳 ) ,内耳骨化 1例 (2耳 )。结论 :对于人工耳蜗植入术的术前评估 ,CT检查具有重要价值 ,必不可少 ,MRI检查是必要的补充。对内耳的三维重建 ,MRI优于CT。     

Mechanisms of noise-induced hearing loss potentiation by hypoxia

Potentiation of noise-induced permanent threshold shift (PTS) by hypoxia has been reported [Hear. Res. 172 (1–2) (2002) 186]. In this study in rats, effects of noise (110 dB SPL), hypoxia (10% O₂), and their combination have been determined on different cochlear potentials and on the expression of genes coding proteins in the outer hair cell (OHC) membrane skeleton (β-actin) and in the mitochondrial respiratory chain (SDHa & b). The noise exposure alone caused CAP threshold shift only in the noise-band. The combined exposure to noise and hypoxia caused an about 40-dB PTS at all frequencies within and above the noise band. Loss of the cochlear amplification was not always related to the CM-suppression. SP was only affected at high frequencies by the combined exposure. Gene expression of β-actin was up-regulated by the noise exposure, which was blocked by hypoxia. Gene expression of SDHa was also up-regulated by the noise and the combined exposure. The data suggest that loss of the cochlear active process, due to damage to the OHC membrane skeleton and to the cellular energy generation system, is related to the noise-induced hearing loss potentiation by hypoxia. Inner hair cell damage may also be involved in the hypoxia potentiation in the basal turn.     

共同腔畸形人工耳蜗手术适应证及手术方法的探讨

目的：探讨共同腔畸形人工耳蜗手术适应证以及人工耳蜗电极植入人路的选择。方法：在对重度或全聋患者进行人工耳蜗植入术前影像掌检查中,发现了6例耳蜗、前庭、外半规管呈共同腔畸形,其中5例有残留听力,1例未查到残留听力。结果：6例影像学检查呈共同腔畸形患者中,对5例有残留听力患者进行了人工耳蜗植入,其中3例选择了常规入路植入电极,2例选择了经乳突侧入路植入电极,术后均建立了人工耳蜗的听觉反应。1例因未查到残留听力,放弃了人工耳蜗手术治疗。结论：有残留听力的共同腔畸形患者,如果能够接受术后听觉言语识别效果差的事实,可以进行人工耳蜗手术。无残留听力或无法了解到有听觉反应的共同腔畸形患者,在现有技术条件下应放弃人工耳蜗植入手术。     

语前聋成人人工耳蜗植入者嗓音的声学分析

目的观察成人语前聋人工耳蜗植入者嗓音的特点,为这类患者的植入及嗓音矫治提供依据。方法分别对28例语前聋成人人工耳蜗植入者、18例语前聋者和10例正常听力者的元音[a ]3s稳定段进行声学分析,分析内容包括基频、第一、第二共振峰、嗓音声学参数频率微扰商、振幅微扰商、谐噪比。对3组结果进行比较。结果人工耳蜗组的基频为(175 42±25 31)Hz,较耳聋组的(210 84±54 30)Hz有下降(P=0 02)。人工耳蜗组共振峰位置[F2 =(1264 64±152 19)Hz]比耳聋组[F2=(1422 44±232 37)Hz]更接近于正常听力组(P=0 02)。频率微扰商在人工耳蜗组(2 09±1 15)较耳聋组(5 32±4 29)更接近于正常听力组(P=0 006)。人工耳蜗组和耳聋组的嗓音表现出较大的个体差异。结论从嗓音声学特点的角度而言,成人语前聋人工耳蜗植入者可以有限地获益于人工耳蜗植入。由于他们的语言识别能力远远差于儿童和成人语后聋人工耳蜗植入者,其总体效果有限,对这类患者的植入应该慎重开展。     

Challenging aspects of contemporary cochlear implant electrode array design

ObjectiveA design comparison of current perimodiolar and lateral wall electrode arrays of the cochlear implant (CI) is provided. The focus is on functional features such as acoustic frequency coverage and tonotopic mapping, battery consumption and dynamic range. A traumacity of their insertion is also evaluated.MethodsReview of up-to-date literature.ResultsPerimodiolar electrode arrays are positioned in the basal turn of the cochlea near the modiolus. They are designed to initiate the action potential in the proximity to the neural soma located in spiral ganglion. On the other hand, lateral wall electrode arrays can be inserted deeper inside the cochlea, as they are located along the lateral wall and such insertion trajectory is less traumatic. This class of arrays targets primarily surviving neural peripheral processes. Due to their larger insertion depth, lateral wall arrays can deliver lower acoustic frequencies in manner better corresponding to cochlear tonotopicity. In fact, spiral ganglion sections containing auditory nerve fibres tuned to low acoustic frequencies are located deeper than 1 and half turn inside the cochlea. For this reason, a significant frequency mismatch might be occurring for apical electrodes in perimodiolar arrays, detrimental to speech perception. Tonal languages such as Mandarin might be therefore better treated with lateral wall arrays. On the other hand, closer proximity to target tissue results in lower psychophysical threshold levels for perimodiolar arrays. However, the maximal comfort level is also lower, paradoxically resulting in narrower dynamic range than that of lateral wall arrays. Battery consumption is comparable for both types of arrays.ConclusionsLateral wall arrays are less likely to cause trauma to cochlear structures. As the current trend in cochlear implantation is the maximal protection of residual acoustic hearing, the lateral wall arrays seem more suitable for hearing preservation CI surgeries. Future development could focus on combining the advantages of both types: perimodiolar location in the basal turn extended to lateral wall location for higher turn locations.     

Tinnitus modifications after cochlear implantation

Tinnitus can be defined as a phantom sensation in the absence of an external sound. In our study, we evaluated the effect of cochlear implant on tinnitus evolution. Among adult, postlingually deaf patients who underwent cochlear implantation at our clinic, we selected 20 subjects with pre-implantation tinnitus (group A) and 10 subjects without pre-implantation tinnitus (group B). Pre- and post-surgery tinnitus was assessed through two questionnaires: the first one dealing with tinnitus characteristics and psychosocial impact, and the second one represented by THI, an internationally validated score of evaluation of the effects of tinnitus on patient’s emotions and activities of daily living. None of the patients belonging to group B developed tinnitus after surgery. As for group A, 40% of patients declared suppression of tinnitus, 30% attenuation of tinnitus after surgery, 25% reported tinnitus was unchanged and 5% reported worsening of tinnitus. In the nine patients with bilateral tinnitus (45%), after implantation tinnitus disappeared from both sides in four patients and attenuated bilaterally in four patients. A comparison between pre- and post-implantation THI scores showed decreased score in 65% of cases, unchanged score in 30% and increased score in 5%. The beneficial effect of cochlear implant on tinnitus, reported by a majority of patients, could be due to acoustic masking, to direct electrical stimulation of the acoustic nerve, and above all to a possible cochlear implantation dependent reorganization of the central auditory pathways and associative cerebral areas. In the light of these results, the authors propose (1) to include tinnitus in the selection criteria of which ear to implant; (2) to consider implantation eligibility for patients with bilateral severe hearing loss associated with severe tinnitus; and (3) to inform patients about the small risk of post-operative tinnitus worsening.     

Monitoring of cochlear function during cochlear implantation

OBJECTIVE: To report the feasibility of monitoring cochlear function during cochlear implantation. STUDY DESIGN: Case report. SETTING: Tertiary care referral center. METHODS: A child with audiologic features typical of bilateral auditory neuropathy underwent cochlear implantation. The scala tympani was entered inferior and slightly anterior to the round window membrane margin and smooth electrode insertion was achieved. Using single polarity click stimuli, the cochlear microphonic was measured at several steps during surgery. RESULTS: Cochlear microphonics were present at all stages during the implantation process and were clearly distinguished from neural responses by stimulus polarity inversion and constant latencies, despite changes in stimulus level. With the electrode in situ, amplitudes were smaller but persisted until the final measurement at 10 minutes after insertion. At follow-up 2 weeks after surgery, behavioral audiometry results indicated profound hearing loss in the operated ear. CONCLUSIONS: This paper demonstrates the feasibility of monitoring cochlear function during cochlear implantation. The routine surgical approach did not appear to adversely affect the functional measurements. Standard size, full electrode insertion did diminish the amplitude of the cochlear microphonics, possibly as a result of intracochlear mechanical impairment. Ultimately, profound hearing loss was documented, indicating that factors other than immediate changes induced by electrode insertion were likely responsible for the loss of cochlear function.     

Cochlear implantation in children with cochlear nerve deficiency

Objective

The aim of this study was to report on auditory performance after cochlear implantation in children with cochlear nerve deficiency.

Methods

A retrospective case review was performed. Five patients with pre-lingual profound sensorineural hearing loss implanted in an ear with cochlear nerve deficiency participated in the study. Postoperative auditory and speech performance was assessed using warble tone average threshold with cochlear implant, speech perception categories, and speech intelligibility ratings. All patients underwent high resolution computed tomography and magnetic resonance imaging.

Results

According to Govaerts classification, three children had a type IIb and two a type IIa cochlear nerve deficiency. Preoperatively, four patients were placed into speech perception category 1 and one into category 2. All patients had an improvement in hearing threshold with the cochlear implant. Despite this, at the last follow-up (range 18–81 months, average 45 months), only one girl benefited from cochlear implantation; she moved from speech perception category 2 to 6 and developed spoken language. Another child developed closed set speech perception and had connected speech that was unintelligible. The other 3 children showed little benefit from the cochlear implant and obtained only an improved access to environmental sounds and improved lipreading skills. None of these 4 children developed a spoken language, but they were all full-time users of their implants.

Conclusions

The outcomes of cochlear implantation in these five children with cochlear nerve deficiency are extremely variable, ranging from sporadic cases in which open set speech perception and acquisition of a spoken language are achieved, to most cases in which only an improved access to environmental sound develops. Regardless of these limited outcomes, all patients in our series use their device on a daily basis and derive benefits in everyday life. In our opinion, cochlear implantation can be a viable option in children with cochlear nerve deficiency, but careful counseling to the family on possible restricted benefit is needed.     

卡铂导致毛细胞及其传出神经损害的耳蜗分析图

目的：介绍一种同时评估耳蜗传出神经和毛细胞的简便的组织化学技术。方法：首先应用脱氢酶染色选择性标记毛细胞,再用乙酰胆碱醌酶染色标记传出神经纤维,双重染色的耳蜗铺片样品在光学显微镜下沿着耳蜗基底膜的全长分别对毛细胞和穿越Ｃｏｒｔｉ隧道的传出神经纤维计数,根据卡铂耳中毒灰鼠的毛细胞及其传出神经纤维损伤的百分比制备耳蜗图。结果：耳蜗分析图充分显示;当绝大多数内毛细胞坏死以及部分外毛细胞坏死时,越隧道的传     

耳蜗内镜在共同腔畸形人工耳蜗植入的应用

目的 内耳共同腔畸形极重度感音性聋患者在人工耳蜗植入中，使用耳蜗内镜检查腔内畸形状态，了解共同腔畸形的内部形态结构，探讨在耳蜗内镜监视下人工耳蜗植入的手术方法和电极摆放的最佳位置。方法 为5例内耳共同腔畸形患者行人工耳蜗植入手术，在打开共同腔后，使用1mm直径耳蜗内镜深入腔内进行探查．选择电极植入的方向和位置。结果 对5例患者进行共同腔内耳蜗内镜检查．见4例腔内充满液体．吸出后腔壁有扉薄黏膜附着，腔呈不规则圆形，直径平均约为6．5mm，中央区贴近内听道底部位见马蹄形或肾形囊腔．约3mm^3大小，为内耳球囊、椭圆囊和中阶畸形融合的结构；1例腔内淋巴液较少，共同腔壁附着软组织和肉芽，约1．5mm厚，无法将腔壁上的软组织与中阶、球囊、椭圆囊的结构区分。结论 （1）共同腔畸形极重度聋患者不仅前庭、外半规管和耳蜗的骨性结构形态发生了变化，而且腔内耳蜗中阶与前庭的球囊、椭圆囊的膜迷路结构形态也发生了变化；（2）微窥镜下分辨不出基底膜或听神经细胞的形态结构，可见畸形前庭的球囊、椭圆囊的囊性结构；（3）进行共同腔畸形人工耳蜗植入手术时，应在耳蜗内镜的监视下，将电极摆放到准确位置，尽可能贴近共同腔的前壁，不应损伤前庭器官。     

Use of MRI to determine cochlear duct length in patients undergoing cochlear implantation

Objectives: It is recognised that CT can be used to determine the cochlear duct length (CDL) when selecting an electrode for cochlear implantation. It is the practice of our institution to routinely use MRI as the sole modality of pre-operative imaging in the assessment of children referred for consideration of cochlear implantation. We therefore wanted to determine whether MRI could be reliably used to determine cochlear duct length.

Methods: An analysis of 40 ears that had undergone MRI and CT of the temporal bones was undertaken. The diameter of the basal turn was independently measured for each ear using the two modalities, and CDL was then calculated.

Results: The mean error of measurement was 0.26?mm (range 0–0.8?mm), leading to a difference in calculated CDL of 0.96?mm (range 0–2.92?mm). CDL did not predict full insertion of 28?mm cochlear implant electrodes in 30 ears.

Conclusions: MRI can be used to reliably determine cochlear duct length.     

Assessment of cochlear implant candidacy in patients with cochlear nerve deficiency using the P1 CAEP biomarker

Abstract

Objective

The goal of this report was to ascertain the efficacy of the P1 cortical auditory evoked potential (CAEP) biomarker as an objective tool to assist in the evaluation of cochlear implant (CI) candidacy in children with a radiological diagnosis of cochlear nerve deficiency (CND).

Methods

Retrospective case study review of audiological and radiological findings was performed in four pediatric patients identified with CND and severe-to-profound sensorineural hearing loss. Cortical auditory evoked potential testing was conducted, and the presence and latency of the P1 component were analyzed.

Results

Three out of four children demonstrated robust P1 CAEP responses, indicating activation of the central auditory pathways by auditory stimulation, despite the diagnosis of CND. These children were considered good candidates for cochlear implantation.

Discussion

Although cochlear implantation in children is a fairly routine procedure, cases exist for which implant candidacy is questionable. Among these cases are children with CND. In these children, cochlear implantation may be contraindicated due to the likelihood that the implant electrodes may not stimulate the VIII nerve adequately. Magnetic resonance imaging (MRI) is considered the gold standard in the assessment of CND, but this measure is not always sufficient to determine CI candidacy in cases of CND. The addition of the P1 CAEP measurement to the usual electrophysiological, audiometric, and radiological test battery may prove to be useful in determining CI options for children with CND.     

内听道斜矢状位磁共振成像在人工耳蜗置入术前评估中的初步应用

目的:探讨内听道(IAC)斜矢状位MRI在人工耳蜗置入术前评估中的应用价值。方法:应用斜矢状位三维快速自旋回波T2加权MRI技术对15例(30耳)拟行人工耳蜗置入术患者的IAC进行扫描。结果:所有患者顺利完成检查,IAC内神经结构显示清楚。13例蜗神经正常的患者行人工耳蜗置入术并已成功开机,2例双侧蜗神经异常者未行耳蜗置入。结论:IAC斜矢状位MRI能清晰显示IAC内蜗神经的形态、大小及IAC的大小,是人工耳蜗置入术前判断蜗神经发育状况的良好方法。