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.     

The correlation between ECochG parameters and early auditory behavior after cochlear implantation in children

Objective: The individual outcome after cochlear implantation in children with auditory synaptopathy/neuropathy (AS/AN) is difficult to predict. A tool for preoperative assessment would be helpful for counseling parents. This study evaluates the outcome after CI in children with AS/AN and with sensorineural hearing loss (SNHL), and correlates it with the preoperative ECochG results in order to find specific parameters of prognostic value. Design: The improvement of auditory behavior after CI was retrospectively assessed using the LittlEARS questionnaire and quantified in a score (LS). This score was correlated with the CAP/SP ratio in the preoperative ECochG. The score was further correlated with the patient’s age six months following CI. Study sample: Nine children with AS/AN were compared to nine children with SNHL. Results: Both groups showed a significant improvement in LS following CI. There was a significant positive correlation between the CAP/SP ratio and the improvement in LS in all children. The correlation between age and LS was significantly negative in the SNHL group and positive in the AS/AN group. Conclusion: All children with AS/AN and SNHL benefit to a similar extent from CI. The preoperatively assessed CAP/SP ratio has a prognostic value for the development of auditory behavior following CI.     

Incidence of auditory neuropathy among the deaf school students

OBJECTIVE: We aimed to determine the incidence of auditory neuropathy (AN) among the deaf school students that have severe hearing loss. METHOD: All students having severe hearing loss constituting a total of 75 at Deafness school in Afyon Province of Turkey were enrolled in the study. The etiological factors about the hearing loss were determined by performing an individual file survey and by interviewing the teachers and parents. First, all the children were subjected to an otolaryngologic examination. Then, auditory brainstem response (ABR) and transient evoked otoacoustic emissions (TEOAE) tests were done to all students enrolled in the study. RESULTS: The ages of the children were between 6 and 17 (mean age 11.9) and 32 (42.9%) of them were girls and 43 (57.1%) were boys. Three cases (4%) were diagnosed as AN in our study, however, no risk factors were determined in two of them. A history of hearing loss following a vaccination was found in only one patient. CONCLUSION: Our data show that the incidence of AN in the children with severe hearing loss is not negligible. Therefore, our results suggest that automatic ABR should be also used with OAE as a routine application in the neonatal screening programmes, since the solely use of OAE in the neonatal screening programmes may result in the delay of the diagnosis of the children with AN.     

The frequency of auditory neuropathy detected by universal newborn hearing screening program

OBJECTIVE: Auditory neuropathy/auditory dyssynchrony (AN/AD) has become a well-accepted clinical entity. The combined use of oto-acoustic emissions (OAEs) and auditory brainstem response (ABR) testing in the universal newborn hearing screening (UNHS) has led to the easy recognition of this disorder. Although, we are now able to diagnose AN/AD reliably, little is known about its epidemiology, etiology, and especially the frequency of its occurrence. The primary goal of this study was to determine the frequency of AN/AD in the Western Anatolian region of Turkey. The secondary goal was to compare the detection rate of AN/AD before and after the implementation of the UNHS in the audiology department of Dokuz Eylul University Hospital. METHOD: Between 2005 and 2007, among the 23,786 newborns who were screened by automated click evoked oto-acoustic emissions (a-CEOAE) and automated auditory brainstem responses (a-ABRs), 2236 were referred to our department. All necessary audiological tests were performed for all the referred newborns. Among them, babies with deficient or abnormal ABR in combination with normal OAEs were considered as having AN/AD. These babies were evaluated with additional diagnostic audiological tests. Furthermore, comparison of the incidence of children diagnosed with AN/AD before and after the implementation of UNHS in our audiology department was also performed. RESULTS: Among the referred newborns, 65 had abnormal or deficient ABR test results. Ten of these 65 newborn babies (mean diagnostic age: 5.7 months) with hearing impairment showed electrophysiological test results that were consistent with AN/AD. The frequency of AN/AD in these 65 children with hearing loss was 15.38%. Moreover, the frequency of AN/AD within UNHS was found to be 0.044%. Seven of the 10 babies with AN/AD had hyperbilirubinemia as a risk factor, which is a high rate to be emphasized. On the other hand, the retrospective investigation of children diagnosed with AN/AD in the same audiology department between 1999 and 2005 (i.e. before the implementation of UNHS) revealed only 7 children, with an average diagnostic age of 34 months. CONCLUSION: After implementing the UNHS, the incidence of AN/AD in the audiology department increased from 1.16 to 4.13. Furthermore, the age of diagnosis of AN/AD decreased from 34 months to 5.7 months. This study shows that AN/AD, when screened, is a comparatively common disorder in the population of hearing-impaired infants. While newborn hearing screening provides early detection of babies with hearing loss, it also helps to differentiate AN/AD cases when the screening is performed with both a-ABR and automated oto-acoustic emission (a-OAE) tests. Thus, the routine combined use of a-ABR and a-OAE tests in UNHS programs, especially for the high-risk infants, can provide better detection of newborns with AN/AD. Furthermore, hyperbilirubinemia is merely an association and maybe etiologically linked.     

Auditory neuropathy/auditory dys-synchrony in school children with hearing loss: frequency of occurrence

OBJECTIVE: The frequency of occurrence of a recently identified hearing disorder, auditory neuropathy/auditory dys-synchrony (AN/AD), was investigated in children with hearing impairment in Hong Kong. METHODS: In this study, 56 students, aged 7-18 years, attending primary divisions in schools for the hearing impaired were screened using otoacoustic emission procedures. RESULTS: One student in the study group was found to have intact outer hair cell function. A detailed diagnostic assessment of this case strongly suggested AN/AD was involved. Combining the study results with those of a previously conducted survey in Hong Kong, the frequency of occurrence of AN/AD in children attending schools for the hearing impaired was estimated to be 2.44% (3 out of 123 children screened). Estimates of the frequency of occurrence of AN/AD in various other educational settings in Hong Kong were also derived. CONCLUSIONS: The study indicates that AN/AD is not an extremely rare disorder. Educational audiologists and other health care professionals need to be actively involved in the identification and management of AN/AD. Research should be directed at technological innovations that may help to overcome the limitations of present screening procedures, in order to more accurately identify the disorder.     

听神经病/听觉失同步化患者的交替短声诱发耳蜗电图

目的 分析听神经病/听觉失同步化(auditory neuropathy/auditory desynchronization.AN/AD)患者交替短声诱发的耳蜗电图特征,探索耳蜗电图在确定听神经病,听觉失同步化病变部位时的应用价值.方法 AN/AD组患者14人,共28耳,所有患者听性脑干反应(ABR)波形缺失或严重分化异常,耳声发射正常:听力正常对照组28人,共35耳.对两组受试者行耳蜗电图(ECochG)检查,使用交替极性短声作为刺激信号.观测AN/AD组和对照组ECochG的波形,并对比:(1)CAP-N1(复合动作电位N1波)的峰潜伏期;(2)-SP(总和电位)和CAP绝对幅度;(3)-SP和CAP幅度比值;(4)CAP反应周值.结果 对照组全部引出分化良好的CAP和-SP.AN/AD组ECochG波形可分为四种类型:(1)可同时引出-SP、CAP,占60.7%;(2)仅有-SP引出,未见CAP引出,占10.7%;(3)仅有CAP引出,占3.6%;(4)-SP、CAP均未引出,占25%.AN/AD组与对照组的CAP潜伏期(P=0.052)无统计学差异;ANIAD组的CAP绝对幅度低于对照组(P<0.001),-SP(P=0.045)绝对幅度、-SP/CAP幅度比(P<0.001)和阈值(P<0.001)高于对照组.结论 在ABR引不出或分化较差时,耳蜗电图是一种比较可靠的评估外周听觉神经功能的方法,在AN/AD的诊断中能够发挥重要作用.     

Cochlear implantation of auditory neuropathy

Auditory neuropathy (AN) is a hearing disorder that presents with a grossly abnormal or absent neural response as measured by evoked potentials in the presence of normal outer hair cell function evidenced by present otoacoustic emissions or cochlear microphonics. Rehabilitation for patients with AN is challenging due to abnormal temporal encoding at the auditory nerve leading to severely impaired speech perception. Although patients with AN may demonstrate improvement in thresholds with amplification, temporal encoding dysfunction, and consequently speech perception degradation, is not alleviated by amplification. Another issue is the heterogeneity of the AN population in terms of audiologic and neurologic findings, in addition to uncertain etiology and pathophysiology. For children with prelingual onset of AN, development of auditory and oral communication skills is particularly compromised. All children with hearing loss in the severe-to-profound range who do not benefit from conventional amplification can be considered candidates for a cochlear implant (CI). This paper presents a case study of a child with AN who received a CI. Whereas no synchronous neural response auditory brainstem response could be elicited to acoustic stimuli, an electrically evoked auditory nerve action potential was evident following implantation, suggesting restoration to some degree of neural synchrony. Significant improvement in speech perception was found post-CI. Recommendation to implant all patients with AN would be premature, but these findings suggest that electrical stimulation in some cases of auditory neuropathy can be a viable option.     

Sacculo-collic pathway dysfunction accompanying auditory neuropathy

CONCLUSIONS: In a patient with bilateral auditory neuropathy (AN), the vestibular-evoked myogenic potential (VEMP) was probably absent because of a neuropathy involving the inferior vestibular nerve and/or its end organ, the saccule. Our result can therefore be interpreted as a concomitant unilateral sacculo-collic neuropathy. We suggest the use of more precise terms to characterize AN patients with involvement of different parts of the inner ear and its innervations. We encourage detailed vestibular assessment in patients with AN in order to assess the co-existence of any symptomatic or asymptomatic vestibular disorder. Information such as that provided in this report will be valuable for clinicians caring for this group of patients. OBJECTIVE: AN is a disorder characterized by the absence or severe impairment of auditory brainstem responses in the presence of normal cochlear outer hair cell function as revealed by otoacoustic emissions (OAEs) and/or electrocochleography (ECoG). A variety of processes and etiologies are thought to be involved in its pathophysiology. In most literature reports the auditory profile of patients with AN is discussed. However, the extent of vestibular involvement, especially that involving the saccule, is not known. We performed vestibular tests to assess the status of the saccule in a patient with AN. MATERIAL AND METHODS: One patient with AN was studied. The patient was a right-handed 21-year-old female with chief complaints of hearing loss and speech perception difficulty. RESULTS: The auditory test results were consistent with the diagnosis of AN, i.e. absent auditory brainstem responses, moderate hearing loss, an inappropriately profound speech discrimination score and the presence of OAEs and measurable cochlear microphonics on ECoG. On neurological examination, gait and balance tests were normal. Ice-water caloric testing induced a sensation of dizziness in both ears. Short tone-burst VEMPs showed no response on left-ear stimulation and a biphasic response with normal latency and amplitude on right-ear stimulation.     

Autosomal recessive hereditary auditory neuropathy

Objectives: Auditory neuropathy (AN) is a sen-sorineural hearing disorder characterized by absent or abnormal auditory brainstem responses (ABRs) and normal cochlear outer hair cell function as measured by otoacoustic emissions (OAEs). Many risk factors are thought to be involved in its etiology and patho-physiology. Three Chinese pedigrees with familial AN are presented herein to demonstrate involvement of genetic factors in AN etiology. Methods: Probands of the above - mentioned pedigrees, who had been diagnosed with AN, were evaluated and followed up in the Department of Otolaryngology Head and Neck Surgery, China PLA General Hospital. Their family members were studied and the pedigree diagrams were established. History of illness, physical examination, pure tone audiometry, acoustic reflex, ABRs and transient evoked and distortion - product otoacoustic emissions (TEOAEs and DPOAEs) were obtained from members of these families. DPOAE changes under the influence of contralateral sound stimuli were obs     

Auditory neuropathy: clinical characteristics and therapeutic approach

PURPOSE: Auditory neuropathy is characterized by congenital sensorineural hearing loss associated with absent or impaired auditory brainstem evoked responses and preservation of outer hair cell activity. This study describes the recent experience of our tertiary pediatric center with auditory neuropathy (AN). METHODS: The files of all children diagnosed with AN at our center from 2000 to 2005 were reviewed for background data, associated factors, laboratory and audiometry findings, management, and outcome. RESULTS: Mean age at diagnosis was 13 months. Factors known to be associated with AN were found in 18 children, namely, prematurity, hyperbilirubinemia, parental consanguinity, or positive family history. Conception by in vitro fertilization was an additional factor not previously reported. The hearing loss was mostly moderate to severe, and bilateral in all patients but one. Otoacoustic emissions and/or cochlear microphonics were demonstrated in all cases. Hearing improved spontaneously in 4 patients. Management with a hearing aid was successful in 1 of 19 patients. Twelve patients received cochlear implants with good outcome. CONCLUSION: Because neonates with AN have normal otoacoustic emissions and/or cochlear microphonics, screening tests for high-risk neonates should be complemented by auditory brainstem evoked responses to avoid false-negative findings. Because AN is considered a retrocochlear lesion, with normal outer hair cell function, rehabilitation with hearing aids is problematic. Although the level of pathology is apparently at the cochlear nerve, cochlear implantation is often a good solution for failures of conventional rehabilitation. However, our finding of spontaneous improvement in a small subgroup raises questions regarding implantation before age 1 year.     

Clinical and audiological features in auditory neuropathy

OBJECTIVE: To medically and audiologically characterize a population of children diagnosed as having auditory neuropathy (AN). STUDY DESIGN: Retrospective medical chart review. SETTING/SUBJECTS: We identified 22 patients from a pediatric otology clinic in a tertiary care pediatric hospital setting. RESULTS: A genetic factor in AN is suggested by our identification of 3 families with 2 affected children and 2 other children with family histories that were positive for hearing loss. Clinical features common among our population included a history of hyperbilirubinemia (n = 11 [50%]), prematurity (n = 10 [45%]), ototoxic drug exposure (n = 9 [41%]), family history of hearing loss (n = 8 [36%]), neonatal ventilator dependence (n = 8 [36%]), and cerebral palsy (n = 2 [9%]). Full clinical and audiological data were available for 18 of the 22 children, including otoacoustic emissions, auditory brainstem responses with cochlear microphonics, and age-appropriate audiometric findings. Significantly, 9 of these 18 patients showed improvement in behavioral thresholds over time, indicating that a subset of children with AN may recover useful hearing levels. Also significant was the success of cochlear implantation in 4 children. CONCLUSIONS: Management of AN in children requires serial clinical and audiometric evaluations, with a prominent role for behavioral testing. Prematurity, genetics, and hyperbilirubinemia appear to be significant factors in the development of AN; hyperbilirubinemia can be associated with spontaneous improvement of hearing thresholds. For those children not benefiting from amplification or FM systems, cochlear implantation remains a potentially successful method of habilitation.     

Transient infantile auditory neuropathy and its clinical implications

OBJECTIVE: Auditory neuropathy (AN) has been a well-accepted clinical entity during the last years. Though we are able to diagnose AN reliably, little is known concerning its epidemiology, etiology and prognosis. This study is aimed at presenting a particular characteristic of the disease, namely its potential transient behaviour, observed in a group of high risk neonates suffering from AN. The ensuing clinical implications are underlined. METHOD: From 1995 to 2004, 1150 high risk (HR) neonates were subjected consecutively to audiological evaluation by auditory brain stem responses (ABR), participating in a targeted hearing screening program for HR neonates. All neonates with ABR threshold >40 dBnHL and middle ear free from disease underwent otoacoustic emissions (OAEs) testing as well. Children with elevated ABR thresholds were scheduled for re-examination after 4-6 months. Only infants demonstrating considerably elevated thresholds (>70 dBnHL), absent or atypical ABR in combination with normal OAEs were considered as suffering from AN. RESULTS: One hundred and seventy-seven neonates showed elevated ABR thresholds (15.4%). Seventy-nine of them demonstrated ABR thresholds >or=75 dBnHL, absent or strongly atypical waveforms at maximum test intensity and among them 25 displayed findings consistent with AN. Follow-up examination revealed a resolution of AN in 13 out of 20 infants retested, that is a restoration of ABR to normal and typical OAEs recordings. Using multiple logistic regression, we found that low birth weight may represent a reliable predictor for clinical recovery of AN infants. CONCLUSION: This article bring to light the temporary character that AN could show in HR neonates and especially in those with low birth weight. Based on the results of our study, the higher the birth weight, the less likely it is for neonates to recover from AN. From a practical point of view, these findings suggest that hearing screening protocols for HR neonates should be revised in both their methodology and time of application. Finally, the decision for amplification or cochlear implantation in HR infants with AN should be made very carefully and well after the 6th month of age, since the maturation process may still be in progress.     

Speech perception in children with auditory neuropathy/dyssynchrony managed with either hearing AIDS or cochlear implants

OBJECTIVE: To evaluate speech perception skills in children with auditory neuropathy (AN)/auditory dyssynchrony (AD)-type hearing loss managed with either hearing aids or cochlear implants. STUDY DESIGN: Prospective data collection in 3 subject groups: AN/AD children fitted with bilateral amplification, AN/AD children fitted with cochlear implant (in 1 or both ears), and a matched control group of implanted children with sensorineural hearing loss. MAIN OUTCOME MEASURE: Open-set monosyllabic words (consonant-nucleus-consonant). RESULTS: Of the 10 implanted AN/AD children, 9 demonstrated significant speech discrimination (consonant-nucleus-consonant phoneme score > or =55%). Similar results were obtained for the aided AN/AD group. Findings for both AN/AD subject groups were poorer than those of the implanted sensorineural cohort. CONCLUSION: Cochlear implantation can offer useful hearing in subjects with AN/AD-type hearing loss. However, expectations for this group may need to be lower than for patients with peripheral (cochlear) loss.     

Cochlear implantation in a Mandarin Chinese-speaking child with auditory neuropathy

Auditory neuropathy (AN) is a hearing disorder characterized by the preservation of outer hair cell function despite the absence of auditory brainstem responses. The pathophysiology and etiology of this condition remain unknown. Recent studies have shown that some patients with AN benefit significantly from cochlear implantation. These patients have all been native speakers of Western languages. A 3-year-old Mandarin-speaking boy was referred to our center because of speech delay. After a series of audiological surveys, retro-cochlear lesion was impressed. During the 2-year period of rehabilitation, poor speech discrimination out of proportion to aided hearing thresholds led to the diagnosis of auditory neuropathy. Because of the limited benefit from amplification, he received a cochlear implant. Significant improvement of speech perception skills assessed by a Mandarin auditory perception test was noted shortly after implantation. The post-implantation performance in this Mandarin-speaking child was consistent with that of reports for implantees speaking Western languages. For Mandarin-speaking children with AN who fail to benefit from conventional treatment, cochlear implantation may be a good alternative choice.     

Sacculo-collic pathway dysfunction accompanying auditory neuropathy

Conclusions. In a patient with bilateral auditory neuropathy (AN), the vestibular-evoked myogenic potential (VEMP) was probably absent because of a neuropathy involving the inferior vestibular nerve and/or its end organ, the saccule. Our result can therefore be interpreted as a concomitant unilateral sacculo-collic neuropathy. We suggest the use of more precise terms to characterize AN patients with involvement of different parts of the inner ear and its innervations. We encourage detailed vestibular assessment in patients with AN in order to assess the co-existence of any symptomatic or asymptomatic vestibular disorder. Information such as that provided in this report will be valuable for clinicians caring for this group of patients. Objective. AN is a disorder characterized by the absence or severe impairment of auditory brainstem responses in the presence of normal cochlear outer hair cell function as revealed by otoacoustic emissions (OAEs) and/or electrocochleography (ECoG). A variety of processes and etiologies are thought to be involved in its pathophysiology. In most literature reports the auditory profile of patients with AN is discussed. However, the extent of vestibular involvement, especially that involving the saccule, is not known. We performed vestibular tests to assess the status of the saccule in a patient with AN. Material and methods. One patient with AN was studied. The patient was a right-handed 21-year-old female with chief complaints of hearing loss and speech perception difficulty. Results. The auditory test results were consistent with the diagnosis of AN, i.e. absent auditory brainstem responses, moderate hearing loss, an inappropriately profound speech discrimination score and the presence of OAEs and measurable cochlear microphonics on ECoG. On neurological examination, gait and balance tests were normal. Ice-water caloric testing induced a sensation of dizziness in both ears. Short tone-burst VEMPs showed no response on left-ear stimulation and a biphasic response with normal latency and amplitude on right-ear stimulation.     

Receptive language and speech production in children with auditory neuropathy/dyssynchrony type hearing loss

OBJECTIVE: The purpose of this study was to characterize the receptive language and speech production abilities of school-aged children with auditory neuropathy/dyssynchrony (AN/AD) and to compare those abilities to children with sensorineural (SN) hearing loss of similar age and degree of hearing loss. DESIGN: Standardized speech and language tests were carried out on 12 AN/AD children, aged between 57 and 167 mo. Each of these subjects was a full-time hearing aid user or had been just before testing. Receptive language skills were assessed using the Peabody Picture Vocabulary Test (PPVT) and speech production ability was measured using the Diagnostic Evaluation of Articulation and Phonology (DEAP) and a Speech Intelligibility Rating Scale. Data from a matched cohort of children with sensorineural hearing loss were also obtained. RESULTS: Receptive vocabulary and speech production were delayed (to varying degrees) in each of the AN/AD subjects (relative to normally hearing children). The group PPVT Language Quotient score was 0.65 +/- 0.19 and the average number of pronunciation errors was 11 +/- 8.4% higher than expected for age. Results for the AN/AD group were however similar to those obtained for a matched group of children with sensorineural hearing loss on both language and speech production measures. CONCLUSIONS: The findings of this study indicate that while AN/AD type hearing loss can pose a significant developmental risk, at least some children fit with conventional amplification can develop reasonable speech and language abilities.     

听神经病患者最大言语识别率与纯音听阈的相关性分析

目的 分析听神经病患者最大言语识别率与纯音测听之间的相关性,探讨听神经病患者与言语识别率不成比例的临床意义.方法 对106例(212耳)经纯音测听、声导抗、畸变产物耳声发射、听件脑干反应测试确诊为听神经病的患者,行最大言语识别率测试,并与不同程度损失及不同类型听力曲线进行分类、分型比较.依据损失分出轻度、中度、中重度和重度;依据听力曲线分为平坦型、低频上升Ⅰ型、低频上升Ⅱ型、山型、谷型、不典型.统计数据应用SPSS 11.0对不同程度的损失、最大言语识别率采用方差分析和相关性分析.结果 106例(212耳)具有相同听力损失或相同类型听力曲线的听神经病患者,可表现出不同程度的最大言语识别率,在听神经病患者群体水平整体评估,最大言语识别率百分比与全频听力阈值旱负相关(r=-0.602;P<0.01),另外,听力损失程度较接近的听力曲线类型,高频听力损失程度轻者其最大言语识别率也相对较好;106例听神经病患者中有26例(52耳)患者双耳分别记录逐步递增的6个刺激声级的言语识别率曲线,其中平均阈上10 dB出现的最大言语识别率频次最高.结论 听神经病患者最大言语识别率在个体问存在明显差异,相同的听力损失,可以出现不同的最大言语识别率;但在群体水平上最大言语识别率与阈值有一定相关性,即听力阈值越大,言语识别率百分比数值越小,且当听神经病患者听力损失在同一水平时,其最大言语识别率程度与听神经病患者听力曲线类型相关.     

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.