Cochlear receptor (microphonic and summating potentials, otoacoustic emissions) and auditory pathway (auditory brain stem potentials) activity in auditory neuropathy

OBJECTIVE: To define both auditory nerve and cochlear receptor functions in subjects with auditory neuropathy (AN). DESIGN: We tested 33 AN subjects (66 ears) and compared them with 21 healthy subjects (28 ears). In AN subjects, the average pure-tone (1, 2, and 4 kHz) threshold loss was 57 dB HL. Click stimuli were used to elicit transient evoked otoacoustic emissions (TEOAEs), cochlear microphonics (CMs), and auditory brain stem responses (ABRs). Both cochlear and ABR potentials were recorded from surface electrodes (vertex-ipsilateral mastoid) using averaging procedures. The amplitudes and latencies of CMs and ABRs and the amplitude of the TEOAEs were analyzed. RESULTS: CM amplitudes recorded from normal ears decreased as a function of subject age. CMs recorded from AN subjects fell within the normal age-adjusted range in 60% of the subjects and were >2 SEEs (standard error of estimate) above the age-adjusted normal regression in 40% of the subjects. TEOAEs were absent in 19 (30%) AN ears (bilaterally in eight, and unilaterally in three subjects) and were present in 44 ears. In AN subjects, correlations among CM amplitude, TEOAE amplitude, and pure-tone average thresholds were not significantly related. CM amplitudes were not significantly different whether TEOAEs or ABRs were present or absent. The ABR was present in 21% of AN subjects and consisted of a low-amplitude Wave V without a preceding Wave I. Measures of CM amplitude and PTA hearing loss were not significantly different in those AN ears with a preserved ABR compared with ears with absent ABRs. Summating potentials to transient click stimuli were of small amplitude (<0.1 microV) and detectable in approximately 50% of the AN and healthy control subjects limiting formal analysis of summating potentials. CONCLUSIONS: In a significant proportion of AN subjects, we found abnormalities of cochlear receptor function, including elevated CM amplitudes and absence of TEOAEs. These two abnormalities occurred independently of each other. A low amplitude Wave V of the ABR was found in approximately one-fifth of AN subjects, evidence that neural synchrony can be partially preserved in some subjects with this disorder.     

Internal auditory canal morphology in children with cochlear nerve deficiency.

OBJECTIVE: To describe the internal auditory canal (IAC) and inner ear morphologic characteristics of children with cochlear nerve (CN) deficiency. STUDY DESIGN: Retrospective case series. SETTING: Tertiary referral center. PATIENTS: Fourteen children with small or absent (deficient) CNs have been identified by means of high-resolution magnetic resonance imaging (MRI). INTERVENTIONS: MRI of the brain. Clinical evaluation. MAIN OUTCOME MEASURES: Review of medical records, audiological testing results, and imaging studies. Images were evaluated for the structure of the cochlear, vestibular and facial nerves, IACs and inner ears. Audiometric thresholds were evaluated in all subjects. METHODS: Fourteen children with small or absent (deficient) CNs have been identified by means of high-resolution MRI. A review of the medical records, audiologic testing results, and imaging studies was undertaken. The images were evaluated for the structure of the cochlear, vestibular and facial nerves, IACs, and inner ears. The audiometric thresholds were evaluated in all subjects. RESULTS: Among the 14 patients, 5 had known syndromes. MRI allowed an exact specification of the nervous structures within all ears with normal-size IACs. Precise characterization of the nerves in ears with small IACs was more difficult, requiring a consideration of both imaging findings and functional parameters. Five children had bilateral deficient CNs, whereas the remaining 9 subjects were affected unilaterally. Thus, 19 ears had CN deficiency (absent CN, 16; small CN, 3). Eleven ears had normal-size IACs and deficient CNs. Of the 9 ears with small IACs, 8 had deficient CNs (absent, 7; small, 1) on the basis of both MRI and functional assessments. Two ears with small IACs had clear morphologic and/or functional evidence for the presence of a CN: one had a small-size CN on MRI, whereas another had a single nerve in a small IAC with present facial and auditory functions. CONCLUSION: The findings of this study suggest that CN deficiency is not an uncommon cause of congenital hearing loss. The findings that most ears with CN deficiency had normal IAC morphology and that two ears with small IACs had CNs present indicate that IAC morphology is an unreliable surrogate marker of CN integrity. On the basis of these findings, we think that high-resolution MRI, rather than CT imaging, should be performed in all cases of pediatric hearing loss, especially in those cases where profound hearing loss has been documented. For ears with small IACs, the resolution of MRI currently remains limiting. In these cases, the determination of CN status frequently requires a variety of anatomic (CT and MRI) and functional tests (auditory brainstem response, otoacoustic emissions, behavioral audiometry, and physical examination).     

蜗神经发育不良患者的听力学特征分析

目的探讨蜗神经发育不良(cochlear nerve deficiency,CND)患者的听力学特征。方法以30例(54耳)(男14例,女16例,年龄6月~29岁,平均4.9岁)内听道斜矢状位磁共振成像示蜗神经发育不良的患者为研究对象,回顾性分析患者的纯音测听或行为测听、声导抗、耳声发射、听性脑干反应(ABR)、听性稳态反应等听力学检测结果及颞骨高分辨CT(HRCT)结果,分析蜗神经发育异常者的听力学特征。结果 30例54耳蜗神经发育不良患者中,双侧24例(80%),单侧6例(20%),其中蜗神经缺如33耳,蜗神经细小21耳。54耳中,共有25耳(46.29%)伴内耳畸形,而单侧蜗神经发育不良者的对侧6耳中,50%(3耳)伴内耳畸形。纯音测听或行为测听和听性稳态反应结果均提示蜗神经发育不良患耳呈重度-极重度听力损失,且蜗神经缺如耳较蜗神经细小耳的听力损失程度更重。11耳(20.37%,11/54)蜗神经发育不良耳可在80~100 dB nHL高强度声刺激下引出听性脑干反应;6例双侧蜗神经发育不良者(20.0%,6/30)中7耳(1例双耳,5例单耳)全部频率或部分频率引出DPOAE,但其中5耳未引出ABR,2耳分别于100和90 dB nHL刺激声强下引出ABR。结论蜗神经发育不良患者常表现为重度-极重度听力损失,近一半伴内耳畸形,部分患耳可引出DPOAE,而ABR严重异常或缺失。     

Predicting cochlear implant outcomes in children with auditory neuropathy

OBJECTIVE: To examine the outcome of cochlear implantation in children with auditory neuropathy (AN) and cochlear nerve deficiency (Group A). Results are compared with a cohort of children with AN and normal cochlear nerves (Group B). STUDY DESIGN: Retrospective cohort study. SETTING: The Sydney Cochlear Implant Centre and the Children's Hospital at Westmead. PATIENTS: Children younger than 15 years with bilateral profound sensorineural hearing loss and the diagnosis of AN confirmed on electrophysiologic testing. All children underwent cochlear implantation with Nucleus 24 cochlear implants from 1997 to 2006. INTERVENTIONS: Magnetic resonance imaging was examined for deficiency of the vestibulocochlear nerve. Brain and inner ear abnormalities were recorded. Cochlear implant outcomes and demographic variables were compared. MAIN OUTCOME MEASURES: Melbourne speech perception score (MSPS) at 1 year and implant evoked electric auditory brainstem response (EABR). RESULTS: Group A performed significantly worse on both parameters than Group B. In Group A, median MSPS was 1, compared with a median score of 4 in Group B (z = -3.010; p = 0.003). EABR was abnormal in 13 of 15 (87%) children in Group A, compared with 9 of 39 (23%) in Group B. Children in both groups with abnormal EABR had significantly worse MSPS (z = -2.780; p = 0.005). Fourteen of 15 children with cochlear nerve deficiency had associated inner ear abnormalities. CONCLUSION: Children with AN can have associated cochlear nerve deficiency. These patients have worse speech perception scores at 1 year post cochlear implantation, higher rates of abnormal EABR, and more associated inner ear abnormalities than children with AN and normal cochlear nerves.     

Auditory sensitivity in children using the auditory steady-state response

OBJECTIVE: To determine the effectiveness of auditory steady-state response (ASSR) as a measure of hearing sensitivity in young children suspect for significant hearing loss. DESIGN: Within-subject comparisons of click auditory brainstem response (ABR) thresholds and ASSR thresholds. SUBJECTS: The study population comprised 42 children suspect for hearing loss and subsequently referred for hearing assessment using electrophysiologic techniques. MAIN OUTCOME MEASURES: Electrophysiologic threshold responses for click ABR and ASSR stimuli (0.5, 1, 2, and 4 kHz) for right and left ears. RESULTS: Based on ABR and ASSR thresholds, 50% of the subjects demonstrated significant hearing loss in the severe to profound range. In some subjects, ASSRs were present at higher stimulus levels when click ABRs were absent. Significant correlations (P<.05) were found between high-frequency ASSR and click ABR thresholds for this study sample. For some subjects, ASSR findings suggested differences between ears that were not observable from the no-response click ABR results. CONCLUSIONS: Auditory steady-state response testing may provide additional information for children who demonstrate hearing levels in the severe to profound range. This information may be helpful when selecting the ear for cochlear implantation for a young hearing-impaired child. Multiple objective methods, such as ABR and ASSR testing, may be needed to determine accurate hearing sensitivity for young children being considered for sensory devices, and in particular, cochlear implants.     

Diverse etiologies manifesting auditory neuropathy characteristics from infants with profound hearing loss and clinical implications

ObjectiveAuditory neuropathy spectrum disorder (ANSD) is a hearing disorder with impaired signal transmission from the inner ear to the brain. The electrophysiological characteristics of auditory neuropathy (AN characteristics) are marked with presence of otoacoustic emissions (OAE) or cochlear microphonics (CM) in the absence of auditory brainstem response (ABR). This study aimed to review etiologies related to AN characteristics from infants with profound hearing loss (HL), either unilaterally or bilaterally.Study designProspective cohort study for thirty infants with prelingual profound HL.MethodsABR, OAE, and/or CM were analyzed to identify electrophysiological characteristics. Temporal bone computed tomography and/or internal acoustic canal magnetic resonance imaging were reviewed to identify anatomical abnormalities. The electrophysiological characteristics and cochlear nerve status were analyzed according to the laterality of deafness (unilateral vs bilateral).ResultsAmong the total 41 ears (from 30 infants) with profound HL, 13 ears (7 (36.8%) of 19 ears with unilateral HL and 6 (27.3%) of 22 ears associated with bilateral HL) showed AN characteristics (37.1%), and 21 ears showed cochlear nerve deficiency (CND) (51.2%). AN characteristics was detected about two times more frequently in cases with CND (38.1%) than with anatomically normal cochlear nerve (20.0%), the difference not reaching a statistical significance probably due to a small sample size. Detection of AN characteristics did not differ between unilateral and bilateral profound HL, even though presence of CND was more frequently detected in cases with unilateral profound HL than with bilateral cases. There were at least five types of etiologies related to AN characteristics in 13 ears (from 10 infants) in our series depending on the laterality of deafness and presence of CND.ConclusionsThis study demonstrates that there were diverse etiologies related to AN characteristics from infants with unilateral or bilateral profound HL. Association between CND and AN characteristics is suggestive but not solid at this moment and AN characteristics is not a fully penetrant feature of CND.     

听神经瘤致聋机理——14例(16耳)听神经瘤病人听力测试结果分析

目的 :探讨听神经瘤听力损失的病理生理机制。方法 :对 14例 (16耳 )听神经瘤患者行纯音听阈、阻抗、听性脑干反应 (ABR)、诱发耳声发射测试 (EOAE)及 CT和 (或 ) MRI扫描。 EOAE能引出的 4耳还检测其传出抑制功能 ,ABR不能检测且 EOAE不能引出的重度聋 (听力损失大于 80 d B)有 5耳行鼓岬刺激试验 (PST)。结果 :16耳听神经瘤中2耳 (12 .5 0 % )听力损失源于神经性损害 ;6耳 (37.5 0 % )蜗性损害 ;8耳 (5 0 % )蜗 -神经性损害。能引出 EOAE的 4耳均有传出功能障碍。结论 :EOAE可评价听神经瘤的耳蜗功能状态 ;ABR结合 PST能分析听神经瘤的蜗后神经功能。听神经瘤的听觉病理可同时或单独发生于听外周的耳蜗水平、第 对颅神经 (传入神经 )水平和橄榄核耳蜗传出神经水平。     

Value of computed tomography in the evaluation of children with cochlear nerve deficiency.

OBJECTIVE: To assess the predictive value of high-resolution computed tomography (HRCT) in the evaluation of children with cochlear nerve deficiency (CND). STUDY DESIGN: Retrospective review of medical records. SETTING:: Tertiary referral center, hospital setting. PATIENTS: Nineteen children (31 ears) with CND. INTERVENTIONS: Magnetic resonance imaging (MRI), HRCT, and audiologic evaluation. MAIN OUTCOME MEASURES: Comparisons of the morphology of the internal auditory canal (IAC), the bony cochlear nerve canal (BCNC) as seen on HRCT, and audiologic data. RESULTS: Of 12 ears with MRI evidence of an absent cochlear nerve (CN) and a normal-size IAC, all had a patent BCNC as revealed by HRCT. Four of these ears failed auditory stimulation after cochlear implantation, confirming clinically significant CND. Of 15 ears with a narrow IAC and a single nerve visible on MRI, 2 (13.3%) had a normal-size BCNC, 4 (26.7%) were narrow, and 9 (60.0%) were absent. One ear with a narrow IAC, normal BCNC, and a single nerve as revealed by MRI has benefited from cochlear implantation. CONCLUSION: Using BCNC patency, as revealed by HRCT, as a means of identifying CND would miss all cases of absent CNs in the setting of a normal-size IAC. Thus, MRI should be the primary modality for imaging children with severe to profound sensorineural hearing loss. When MRI demonstrates a single nerve within a narrow IAC, the addition of HRCT can further identify more than half of these cases as involving absent CNs because of an absent BCNC. In a subset of patients, CN status remains indeterminate.     

Profound hearing loss attributable to cochlear nerve disease: diagnosis with combination of otoacoustic emission and magnetic resonance imaging

OBJECTIVE: To detect the causes of deafness based on the combined findings of auditory brainstem response (ABR), distortion product otoacoustic emissions (DPOAEs), and three-dimensional Fourier transformation-constructive interference in steady state (3DFT-CISS) magnetic resonance imaging (MRI). STUDY DESIGN: Retrospective review of the medical records of 13 patients with unilateral profound hearing loss since childhood. METHODS: Subjects were tested with pure-tone audiometry, ABR, DPOAEs, and 3DFT-CISS imaging. RESULTS: No significant components of ABR were observable in any of the deaf ears. In 10 cases, the cochlear nerves of the deaf ears were found to be as normal as the healthy sides by 3DFT-CISS imaging, and no significant levels of DPOAEs were recorded. In the other three cases, no apparent cochlear nerves were identified by 3DFT-CISS imaging. Although no significant levels of DPOAEs were observable in two cases with cochlear nerves invisible by the MRI study, almost the same level of DPOAEs as that in the healthy side was recorded in the last case. CONCLUSIONS: In the last particular case, the cochlear nerve seemed to be mainly responsible for the profound deafness. 3DFT-CISS imaging in combination with preexisting audiological measures may provide direct evidence for the cochlear nerve disease. steady state, internal auditory canal, cochlear nerve disease.     

Prevalence of auditory neuropathy/synaptopathy in a population of children with profound hearing loss

OBJECTIVE: To examine the prevalence of auditory neuropathy/synaptopathy (AN/AS) in a cohort of children with profound hearing loss. METHODS: From 1997 until 2004, 5190 children, aged 1-15 years, whose hearing ability was uncertain or who had risk factors for hearing impairment were investigated with subjective and objective hearing tests. Three thousand four hundred and fifteen from these children were screened for AN/AS using pure-tone audiometry, impedance measurement, transient evoked otoacoustic emissions (TEOAE) and click-evoked auditory brainstem responses (ABR). RESULTS: From 3415 patients who participated in an ABR and TEOAE assessment, 379 children showed absent or elevated (> or = 80 dB nHL) ABR thresholds. Within this group we found 32 cases with evidence of AN/AS via visible TEOAE and/or cochlear microphonics (CM) coupled with absent ABR. In the remaining 3036 children, AN/AS, could be ruled out by means of detectable ABR-thresholds and coherent findings in pure-tone audiometry and TEOAE assessment. This results in a prevalence of AN/AS of 0.94% within the group at risk for hearing loss, compared to 8.44% among profoundly hearing impaired children. CONCLUSION: This study shows that AN/AS is a common finding in the population of hearing impaired infants. In the majority of our AN/AS children (50%, n=16), an early audiological diagnosis was made under the age of 12 months. Therefore, clinicians and other health care professionals should generally be sensitised for AN/AS in infants, so that an appropriate treatment can promptly be initiated. Further research on clinical and pathophysiological aspects is necessary to better identify and manage patients suffering from AN/AS.     

Ipsilateral and contralateral vestibular schwannomas in unilateral long-term deaf ears

In the past decade, we have encountered two patients with unilateral long-term deaf ear having vestibular schwannoma. One was on the deaf ear in a 53 years’ woman and the other was on the contralateral hearing ear in a 62 years’ woman. These two patients had total deafness on the right ear since childhood, associated with absent auditory brainstem response (ABR) and caloric responses, whereas normal ABR and caloric responses were shown on the left ear. Although similar physiological findings were disclosed on the deaf ears, MRI scan demonstrated vestibular schwannoma on the different side, that is, one in deaf ear and the other in hearing ear. For the former, absent ABR and caloric results indicate that the tumor originates from the superior vestibular nerve. In contrast with the latter, normal ABR and caloric responses, but absent vestibular-evoked myogenic potentials on the hearing ear imply that the tumor originates from the inferior vestibular nerve. The ipsilateral tumor on the deaf ear underwent intracranial surgical excision, followed by radiosurgery due to tumor recurrence 10 years later, while the contralateral one on the only hearing ear received radiosurgery only. Both patients were rather well, 3 years after last treatment.     

蜗神经发育不良儿童的临床特征分析

目的探讨蜗神经发育不良(cochlear nerve deficiency,CND)儿童的临床特征。方法以43例(60耳)CND患儿(4个月~10岁,平均2.6±2.8岁)为研究对象,总结分析其是否存在听力损失高危因素、影像学检查及听性脑干反应(ABR)、畸变产物耳声发射(DPOAE)、Chirp声诱发听性稳态反应(Chirp-ASSR)检测等结果。结果43例患儿中,26例(60.5%,26/43)为单侧病变,17例(39.5%,17/43)为双侧病变;仅7例患儿有听力损失高危因素。50耳(83.3%,50/60)为蜗神经缺如,10耳(16.7%,10/60)为蜗神经细小;16耳(26.7%,16/60)伴面神经细小,8耳(13.3%,8/60)伴前庭神经异常。4耳(6.7%,4/60)仅伴前庭畸形为第一组,21耳(35%,21/60)合并耳蜗畸形或同时合并前庭畸形为第二组,35耳(58.3%,35/60)不伴内耳畸形为第三组。26耳(43.3%,26/60)ABR仅见波Ⅲ以前波形分化,随后波形消失;23耳(38.3%,23/60)ABR无波形分化;11耳(18.3%,11/60)可见分化不良的波V,其反应阈值为75~100 dB nHL。24耳(40%,24/60)DPOAE或/和CM引出,且第三组CND患儿DPOAE的信噪比(SNR)值和引出率均明显高于CND合并内耳畸形的第一、二组患儿。49耳ABR最大声输出时未引出波V的CND患儿中,41耳(83.7%,41/49)Chirp-ASSR可在不同频率不同程度引出,500、1000、2000和4000 Hz Chirp-ASSR平均反应阈分别为87.14±21.33、89.27±16.09、89.37±15.85和91.10±15.77 dB corHL。结论本组CND患儿多无明确听力损失高危因素或病因,多表现为重度或极重度感音神经性聋,高发于先天性单侧感音神经性聋婴幼儿,可表现出听神经病的特征,ABR仅见波III以前波形分化,随后波形消失,Chirp-ASSR测得残余听力明显优于ABR检测结果。     

听神经病106例听力学分析

目的 分析106例听神经病患者的临床特点和听力学测试结果.探讨听神经病纯音听力图和听性脑干反应(ABR)的特点.方法 回顾性分析2001年12月至2007年5月就诊的106例(212耳)听神经病患者的症状及纯音听阈、声导抗图及镫骨肌反射、ABR、畸变产物耳声发射(DPOAE)和颅脑影像学检查的结果.结果 患者中男54例,女52例;年龄11～37岁,以青少年居多(75例,70.8%).伴有其他外周神经病者8例,伴视神经病者4例,未查出明确病因者94例.患者均为双耳发病.在212耳中,有173耳(81.6%)听力下降最多的频率为0.25 kHz和0.5 kHz.轻至中度听力损失共209耳(98.6%),均为感音神经性听力损失.按WHO(1997)听阈的均值计算法统计,本组有49耳(23.1%)的听阈≤25 dB,按WHO推荐的听力减退分级标准,使这些有听力障碍的病耳列入了正常范围.212耳听性脑干反应的测试中,各波形皆未引出者124耳(58.5%),余88耳有1或2个波未引出,而可引出的波的波幅很小,但有重复性.在1或2个可引出小波病例中,有23例其另1侧耳各波皆缺失.另有2例伴其他周围神经病和1例伴视神经病的患者,其双耳均有1或2个小波可引出.畸变产物耳声发射除1例左侧3～6 kHz,右侧5～6 kHz未引出外,余均可引出.结论 听神经病在青少年中并不罕见.因听神经病大多以低频听力下降为主,对听神经病患者平均听阈的计算方法值得讨论.     

儿童单侧听神经病附三例分析

目的 探讨儿童单侧听神经病的听力学特征。方法 对3例单侧听神经病患儿进行纯音听阈(PTT)、声反射(AR)、听性脑干反应(ABR)和畸变产物耳声发射(DPOAE)检查，并对其结果进行综合分析。结果 3例患儿的PTT均呈1侧耳听力正常，另1侧耳听力丧失。健耳的同侧和交叉AR能引出，患耳的同侧和交叉AR未能引出。健耳的ABR各波潜伏期正常，患耳的ABR各波未能引出。双耳DPOAE各频率反应幅值正常。结论：DPOAE正常或基本正常，PTT、AR和ABR异常是听神经病的重要特征。单侧听神经病的听力学特征与双侧听神经病基本一致。对儿童表现为单侧感音神经性聋者宜进行系统的听力学检查，以期作出正确的诊断。     

Electrocochleography in auditory neuropathy

Auditory neuropathy (AN) is a disorder characterized by the absence or the severe impairment of the auditory brainstem responses (ABRs) together with the preservation of otoacoustic emissions and/or cochlear microphonic (CM). We recorded transtympanic electrocochleography (ECohG) evoked by 0.1 ms clicks in one young adult and in four children having distortion product otoacoustic emissions and absent ABRs. In all but one patient CM and summating potential (SP) were present with normal threshold, and their amplitudes appeared comparable to or higher than the values obtained from subjects with normal hearing. The compound action potential (CAP) was absent in two patients while in one subject CM and SP were followed by a highly desynchronized neural activity. A broad CAP was found in two children and the threshold appeared clearly elevated in one of them, while it showed only a mild elevation in the other. No correlation was found between CAP and behavioral thresholds. These results suggest that ECohG can be useful in AN diagnoses since it is the only reliable tool in evaluating the auditory peripheral function in the presence of a desynchronized ABR.     

Abnormal Cochlear Potentials from Deaf Patients with Mutations in the Otoferlin Gene

Otoferlin is involved in neurotransmitter release at the synapse between inner hair cells (IHCs) and auditory nerve fibres, and mutations in the OTOF gene result in severe to profound hearing loss. Abnormal sound-evoked cochlear potentials were recorded with transtympanic electrocochleography from four children with otoferlin (OTOF) mutations to evaluate physiological effects in humans of abnormal neurotransmitter release from IHCs. The subjects were profoundly deaf with absent auditory brainstem responses and preserved otoacoustic emissions consistent with auditory neuropathy. Two children were compound heterozygotes for mutations c.2732_2735dupAGCT and p.Ala964Glu; one subject was homozygous for mutation p.Phe1795Cys, and one was compound heterozygote for two novel mutations c.1609delG in exon 16 and c.1966delC in exon 18. Cochlear potentials evoked by clicks from 60 to 120 dB peak equivalent sound pressure level were compared to recordings obtained from 16 normally hearing children. Cochlear microphonic (CM) was recorded with normal amplitudes from all but one ear. After cancelling CM, cochlear potentials were of negative polarity with reduced amplitude and prolonged duration compared to controls. These cochlear potentials were recorded as low as 50–90 dB below behavioural thresholds in contrast to the close correlation in controls between cochlear potentials and behavioural threshold. Summating potential was identified in five out of eight ears with normal latency whilst auditory nerve compound action potentials were either absent or of low amplitude. Stimulation at high rates reduced amplitude and duration of the prolonged potentials, consistent with neural generation. This study suggests that mechano-electrical transduction and cochlear amplification are normal in patients with OTOF mutations. The low-amplitude prolonged negative potentials are consistent with decreased neurotransmitter release resulting in abnormal dendritic activation and impairment of auditory nerve firing.     

Fluctuating corticosteroid-responsive auditory neuropathy/dyssynchrony is suggestive of central nervous system pathology.

OBJECTIVE: To highlight diagnostic and management features of auditory neuropathy/auditory dyssynchrony (AN/DS) due to central demyelinating disorder. PATIENTS: A child with AN/DS due to central nervous system pathologic findings. INTERVENTIONS: Audiometry, auditory brainstem response (ABR) test, otoacoustic emission test, magnetic resonance imaging (MRI) with gadolinium contrast, intravenous corticosteroid treatment, antiviral treatment, stereotactic biopsy, and cyclophosphamide immunomodulation. MAIN OUTCOME MEASURES: Pure-tone audiometry, speech discrimination testing, ABR, and MRI. RESULTS: A 12-year-old girl presented with acute sensorineural hearing loss, abnormal ABR, and normal otoacoustic emissions consistent with AN/DS. The hearing loss demonstrated fluctuation and corticosteroid responsiveness. Magnetic resonance imaging and stereotactic biopsy revealed brainstem demyelination consistent with multiple sclerosis. Definitive treatment consisted of cyclophosphamide immunomodulation. CONCLUSION: Although recent focus on pathophysiology of AN/DS has shifted from auditory nerve abnormalities to dyssynchrony within the cochlea, cases associated with fluctuating sensorineural hearing loss and responsiveness to corticosteroid therapy should raise the suspicion of central nervous system pathologic findings. Therefore, it is crucial to obtain brain MRI with contrast enhancement in all patients with AN/DS. This is critical in patients undergoing cochlear implantation because MRI may be contraindicated postoperatively.     

听神经瘤的耳声发射观察

目的 观察和分析听神经瘤的耳声发射特点,为评估听神经瘤患者的耳蜗功能和选择保护听力的术式提供参考依据.方法 对20例（22耳）听神经瘤患者行纯音听阈、阻抗、听性脑干反应（auditory brainstem response,ABR）、诱发性耳声发射（evoked otoacoustic emissions,EOAE）测试及CT和（或）MRI扫描,能引出EOAE的瘤耳检测其自发性耳声发射（spontaneous otoacoustic emissions,SOAE）和传出抑制功能.结果 28.57%听神经瘤耳能引出EOAE,按其畸变产物耳声发射（distortion product otoacoustic emissions,DPOAE）特点分为三型：①“耳蜗型”3耳;②“非耳蜗型”2耳;③“混合型”1耳;“非耳蜗型”耳能引出强大的SOAE;能引出EOAE的6耳均有内侧橄榄耳蜗传出系统功能障碍.结论 EOAE可精确分析听神经瘤患者的耳蜗（外毛细胞）功能,部分听神经瘤病人存在“离断耳”现象.耳声发射（otoacousticemissions,OAE）在诊断重度感音神经性聋（包括听神经瘤病人）方面有一定潜能.     

小儿蜗神经发育不良

目的报道一组蜗神经发育不良(cochlear nerve deficiency,CND)小儿的临床特征,以提高对本病的认识。方法回顾性分析2007年1月到2008年4月就诊的、内耳MRI及听力学资料完整的20例(37耳)CND小儿(其中男13例,女7例,年龄10个月到4岁)的影像学、听力学表现及人工耳蜗植入效果。结果 85%(17/20)的患儿为双侧发病,15%(3/20)为单侧发病;16.22%(6/37)合并前庭神经发育异常,8.11%(3/37)合并面神经发育异常。根据是否伴有内耳畸形分为三组:32.43%(12/37)伴耳蜗畸形或同时伴有前庭畸形(第一组);13.51%(5/37)仅伴前庭畸形(第二组);54.05%(20/37)独立发病,不伴内耳畸形(第三组)。听力学测试结果:86.49%(32/37)ABR最大输出(100 dB nHL)无反应,13.51%(5/37)在非常高的刺激强度仅有分化不良的波Ⅴ;9耳有行为听阈结果者均为极重度感音神经性聋;第一组12耳DPOAE和CM均未引出,第二组60%(3/5)DPOAE和CM均未引出,40%(2/5)DPOAE和/或CM引出;第三组45%(9/20耳)DPOAE和CM均未引出,55%(11/20耳)DPOAE和/或CM引出。人工耳蜗植入效果:2例术前、术后资料完整者中1例术后开机一年婴幼儿有意义听觉整合量表(infant and toddler meaningful auditory integration scale,IT-MAIS)评估得分与蜗性聋儿相当,另1例无效。结论 CND患儿多无特殊病史,根据是否伴有内耳畸形及内耳畸形的种类,其听力学表现多样,诊断主要依据影像学检查,应注意鉴别诊断,以便制定合理有效的干预措施。     

Case report: "auditory neuropathy" in a newborn caused by a cerebellopontine angle arachnoid cyst

We present a 6-week-old girl, referred because of failed newborn hearing screening in the right ear. Click-evoked oto-acoustic emissions were present in both ears, auditory brainstem responses (ABR) were present in the left but totally absent in the right ear. A magnetic resonance imaging (MRI) study revealed a large arachnoid cyst in the right cerebellopontine angle (CPA) and a diagnosis of “auditory neuropathy/auditory dyssynchrony” was established. A microsurgical resection of the cyst wall and fenestration was performed by a retro sigmoid approach. This is the first case in the literature of auditory neuropathy (AN) in an infant caused by a cerebellopontine angle arachnoid cyst.