Diagnosis Of Auditory Neuropathy Research Articles

Study on the clinical characteristics of auditory neuropathy patients with normal pure tone average or mild hearing loss

Objective: The purpose of this study was to analyze the clinical characteristics of auditory neuropathy (AN) patients with normal hearing or mild hearing loss. Methods: Data from Multicenter Study on Clinical Diagnosis and Intervention of Acoustic Neuropathy (registration number: ChiCTR2100050125). According to the Chinese clinical practice guideline of auditory neuropathy (version 2022), these patients divided into two groups: the normal hearing group (PTA Normal, PTAN group, the average hearing threshold<20 dB HL) and the mild hearing loss group (PTA Mild hearing loss, PTAM group, the average hearing threshold between 20-35 dBHL). The audiology characteristics, clinical features, and follow-up were analyzed. Data analysis was conducted using GraphPad Prism 8 and SPSS 20.0 software. Results: A total of 75 AN with normal hearing or mild hearing loss were included in this study. The PTAN group consisted of 19 patients (38 ears), including 12 males and 7 females. The average onset age was (16.9±4.5) years old, while the test age was (22.1±5.8) years old for PTAN group. The PTAM group consisted of 56 patients (112 ears), including 29 males and 27 females. The average onset age was (16.2±7.9) years old, while the test age was (23.9±9.0) yeas old for PTAM group. The average hearing threshold of low frequency (0.125-0.5 kHz) was significantly decreased. ABR disappeared in 86.00% (126/150) of the patients. The speech recognition rate was 71.80±22.44% in the PTAN group and 58.08±29.28% in the PTAM group.-SP/AP was 0.98±0.47 in the PTAN and 1.07±0.63 in PTAM group; 40 (53.33%) patients had tinnitus. 29 patients (58 ears) were followed up, including 10 patients (20 ears) in the PTAN group and 19 patients (38 ears) in the PTAM group. There was no significant change in hearing threshold in short-term follow-up (<3 years). With the extension of the disease duration (>3 years), the PTAN group tended to decrease at low frequency, and the PTAM group decreased at high frequency first. The hearing threshold at 0.25 kHz in the PTAN group and 4 kHz in the PTAM group decreased significantly. Conclusions: AN patients with normal hearing or mild hearing loss exhibit abnormal results in audiological examination results, including ABR, electrocochleography and speech discrimination score. A combination of audiological tests should be used to make the diagnosis of AN. With the progression of the disease, AN with normal hearing or mild hearing loss tends to decrease.

Auditory neuropathy in patients with features of tropical ataxic neuropathy in Tanzania

Objective This study aimed to describe the diagnosis of auditory neuropathy (AN) in patients with features of tropical ataxic neuropathy (TAN) at a private audiology facility in Dar es Salaam, Tanzania. Method A retrospective chart review of thirty-two patients with suspected AN and features of TAN seen in 2019. Results The 32 patients complained of hearing impairment and all were diagnosed with AN (100%) via audiometry, otoacoustic emissions (OAE), and auditory brainstem response (ABR). The mean age was 24.8 ± 7.7 years, between 10.3 and 47.0 years. Sixteen (50%) reported tinnitus, eight (25%) reported imbalance while walking, 10 (31.3%) reported vertigo/dizziness, 13 (40.6%) had visual problems, and 19 (59.4%) reported peripheral neuropathy/weakness. Audiometric thresholds ranged from normal to profound, with the most common degree of severity being moderate (59.4%, n = 19). All except one patient had present OAEs, regardless of the severity of hearing loss. ABR was examined in 10 patients and found to be abnormal at 90 dB nHL in all of them. Conclusion The investigation of hearing impairments requires more than tuning fork or audiometry to understand the true nature of the patient’s hearing loss. Awareness of AN pattern in TAN among audiologists and other professionals within the hearing care field in low-and-middle-income countries, such as Tanzania should be strengthened.

Isolated auditory neuropathy at birth in congenital cytomegalovirus infection

BackgroundCongenital cytomegalovirus (cCMV) infection is the most frequent non-genetic cause of sensorineural hearing-loss (SNHL) (i.e., hearing loss due to a cochlear and/or auditory nerve damage). It is widely accepted that SNHL at birth, when associated to cCMV symptomatic infection involving the central nervous system, benefits from antiviral therapy started in the neonatal period. Conversely, there is no consensus for antiviral treatment in congenitally infected infants diagnosed with isolated SNHL (i.e., SNHL in an otherwise asymptomatic infant) at birth.Our aim was to assess the frequency and the auditory outcome of isolated SNHL at birth due to auditory neuropathy (AN) (i.e., SNHL in a patient with normal cochlear function and auditory nerve dysfunction) in infants with cCMV infection.MethodsWe retrospectively reviewed the clinical history of 60 infants, born at term, with cCMV asymptomatic infection, without additional risk factors for SNHL, and exhibiting bilateral “pass” otoacustic emissions (OAE). None of them underwent antiviral therapy.Hearing thresholds were assessed by means of Auditory Brainstem Responses (ABR). AN affected children were followed up until possible normalization of the hearing thresholds or definitive diagnosis of AN. Each infant diagnosed with monolateral or bilateral AN was classified according to the worst ear threshold.ResultsIn our population, the first ABR was performed at a mean age of 5.00 ± 2.79 (SD) months and AN was diagnosed in 16/60 (26.67%) infants; in 4 infants the AN was defined as mild (4/4 monolateral), moderate in 11 (5/11 bilateral), and severe in 1 (bilateral). The mean age at first ABR was 3.69 ± 2.80 (SD) months in the 16 babies with AN and 5.48 ± 2.66 (SD) months in the 44 infants with normal hearing (p = 0.007). All AN cases spontaneously recovered a normal auditory threshold over time. The mean length of the audiological follow-up was 32.44 ± 17.58 (SD) months (range 5–60 months).ConclusionA delayed maturation of the auditory pathways should be considered when a mild/moderate isolated AN at birth is detected in cCMV infected infants. Prospective studies conducted on larger populations, and with a longer audiological follow-up, are needed to confirm our findings.

Auditory Neuropathy: A Case of Near Misdiagnosis

Auditory neuropathy is a type of hearing loss. This is a case study that describes an 18 months old child presenting with hearing loss reported by his parents. The parents reported that although he exhibited signs of hearing loss, they were told by multiple experts that tests confirmed that he was not deaf. The child sometimes acted as if he was deaf and sometimes did not, which lead to confusion about additional diagnoses that might be included in the diagnosis. An early diagnosis of auditory neuropathy is time sensitive as early development of learning and language is more beneficial for the child. Listening to parents and understanding the subtleties that segregate the diagnosis of auditory neuropathy from auditory processing disorder, autism or other similar presentations is important in the diagnosis and treatment of auditory neuropathy in children.

Clinical presentation and audiologic findings in pediatric auditory neuropathy

Aim: of the study was to rule out audiologic findings, related etiologies and its effect in pediatric patients having hearing deficits that are most likely due to a neuropathy of the eighth nerve. Study Design: Retrospective neo-natal hearing screening programme based. Subject and Methods: Subjects include 30 children aged from 0 yrs to 12 yrs, were tested with pure tone audiometry, behavioral observation audiometry, free-filed audiometry, speech audiometry, auditory brainstem response, and click evoked otoacoustic emissions. Results: Pure tone and free-field testing revealed 40 ears (66.67%, n = 60) with sloping type, sensorineural hearing loss, 20 ears (33.3%, n = 60) had flat configuration. Out of this 18 (6%, n = 30) subject showed bilateral similar configuration (either bilateral sloping type/ flat type of audiogram). Rest 12 (40%, n = 30) subject showed bilateral different pattern. 10 (33.3%, n = 30 children demonstrated fair to poor word discrimination scores and the other 2 (6.67%, n = 30) had fair to good word discrimination. For other rest of 18 (60%, n = 30) children speech test couldn't be performed because of age limit and poor speech and language development. Out of 30 subjects 28 (93.3%, n = 30) showed normal distortion product Otoacoustic emissions and 2(6.67%, n = 30) subjects showed absent emissions. Conclusions: All thirty children demonstrated absent or marked abnormalities of brainstem auditory evoked potentials which suggest cochlear outer hair cell function is normal; mostly lesion is located at the eighth nerve or beyond. Generally auditory neuropathy is associated with different etiologies and it is difficult to diagnose auditory neuropathy with single audiological test; sufficient test of battery is required for complete assessment and diagnosis of auditory neuropathy

Speech and Language Outcomes of Cochlear Implantation in Children With Isolated Auditory Neuropathy Versus Cochlear Hearing Loss

Children with auditory neuropathy (AN) have variable hearing on pure tone testing, and the presence of speech and language delays often play a major role in the decision to offer cochlear implantation (CI) in this population. Despite this fact, the speech and language outcomes in this group after CI are not well described. This study compares speech and language outcomes after CI in a subset of the pediatric AN population that does not have a confounding cognitive disorder with those of their peers with cochlear hearing loss (CoHL). Retrospective chart review. Tertiary referral center. Seventeen pediatric patients with AN who received a CI and a group of children with CoHL who received a CI were the subjects of this study. The 2 groups demonstrated similar ages at implant. Children with cognitive delays were excluded from each group. Cochlear implantation. All subjects were evaluated preoperatively and postoperatively with standardized age appropriate speech and language measures, including the Expressive Vocabulary Test (EVT), Peabody Picture Vocabulary Test (PPVT), and Preschool Language Scale (PLS). There was no significant difference between the groups on age of activation of the CI. Children with a diagnosis of AN had a significantly lower unaided pure tone average preoperatively as compared with children with cochlear hearing loss; however, there was no significant difference between the groups on either their preimplantation or postimplantation speech and language scores. Children with a diagnosis of AN without associated cognitive or developmental disorders have speech and language outcomes comparable to other children who received a CI.

Outcomes of Cochlear Implantation in Children With Isolated Auditory Neuropathy Versus Cochlear Hearing Loss

Auditory neuropathy (AN) is a heterogeneous clinical entity for which the optimal method of auditory rehabilitation has been a matter of some debate. Such patients often do not receive sufficient benefit from hearing aids. Previous studies have shown that select AN patients may benefit from cochlear implantation (CI), but reported outcomes are variable and likely are a reflection of the heterogeneous patient population included under the umbrella diagnosis of AN. This study compares CI outcomes in a subset of the pediatric AN population who do not have a confounding cognitive disorder with their cochlear hearing loss peers. Additionally, it examines the impact of a confounding cognitive or developmental disorder on CI outcomes within the AN population. Retrospective chart review. Tertiary referral center. Twenty-six pediatric patients with AN who received a CI were the subjects of this study. Seventeen of these children had a diagnosis of AN alone, and their CI outcomes were compared with those of a similar group of children with cochlear hearing loss. The remaining 9 children had a diagnosis of AN in association with a confounding cognitive or developmental disorder, and their CI outcomes were compared with those of children with isolated AN. Cochlear implantation. All subjects were evaluated preoperatively and postoperatively with age-appropriate speech perception testing. Children with a diagnosis of AN alone performed comparably to their peers with cochlear hearing loss. The presence of a confounding cognitive or developmental disorder within the AN population was correlated with significantly poorer CI outcomes as compared with those of children with isolated AN. Children with a diagnosis of AN without associated cognitive or developmental disorders perform at a level comparable to other children requiring a CI. Children with a diagnosis of AN associated with other developmental anomalies derive some benefit from CI but are significantly more likely to continue to rely on nonoral/aural methods of communication after implantation.

Characteristics of cochlear microphonics in infants and young children with auditory neuropathy

Conclusions: Cochlear microphonics (CMs) play an important role in the diagnosis of auditory neuropathy (AN). It is necessary and helpful to diagnose the sites-of-lesion in infants and children with AN by analyzing the patterns of CM amplitudes and I/O functions together. Objectives: To investigate the characteristics and clinical significance of CMs in the diagnosis of AN among infants and children. Methods: A total of 36 infants and children (16 males and 20 females) were divided into two groups. Group A included 15 children (30 ears) with auditory brainstem response (ABR) absent and distortion product otoacoustic emissions (DPOAEs) present and group B included 21 children (30 ears) with ABR absent and DPOAEs absent. Fifteen normal-hearing infants (30 ears) made up the control group. Click eliciting CMs were recorded at stimulus levels of 100, 90, 80, and 70 dB nHL for each ear using a button electrode placed at the top of the forehead. A tube-clamping method was used to distinguish CMs from artifacts, and an averaging algorithm was used to obtain a clear CM waveform. The time delay and amplitude of CMs were measured in both children with AN and normal-hearing infants on (C–R)/2 waveforms, and an I/O function curve for each group was plotted with the stimulating level as input and the CM amplitude as output. Results: The largest identifiable CMs were generally found between 0.5 and 0.8 ms after stimulation with mean delay of 0.63 ± 0.04 ms in both group A and the control group, and 0.63 ± 0.07 ms in group B. There was no significant difference between the AN group and the control group in CM time delay. There was no significant difference (p > 0.05) between group A (AN with OAEs present, 0.47 ± 0.15 μV) and the control group (0.45 ± 0.13 μV) in CM amplitude, while CM amplitudes in children with AN with DPOAEs absent (0.24 ± 0.08 μV) were significantly lower than those in either the control group or group A (p < 0.01). The amplitude of CMs reduced with stimulus intensity in all the subjects. There was obvious nonlinearity in group A and the control group, while there was a more linear tendency in amplitude increasing on the I/O function curve in group B.

Analysis of improper pattern of Mandarin monosyllable recognition test among the patients with auditory neuropathy

To analyze the improper pattern in mandarin monosyllable recognition test among the patients with Auditory Neuropathy (AN) in order to work out the common characteristics in speech recognition which might be suitable for diagnosis of AN. Sixteen AN patients (32 ears) were studied and 22 patients (32 ears) with sensorineural hearing loss (SNHL) were set for control. In accordance with audiogram pattern, all subjects were then divided into the up-type hearing (15 ears) and non up-type hearing (17 ears) groups. All 64 ears were tested in high intensity by mandarin monosyllable test material which we have developed before. Monosyllable performance scores from testing ears and improper patterns were recorded respectively. Eight improper patterns were then defined as follows: consonant only, vowel only, tone only, consonant and vowel, consonant and tone, vowel and tone, all phonemes and no response. The score of patients with AN was lower than those patients with SNHL in monosyllable recognition test (P < 0.001). No significant difference was found between subgroup of up-type hearing loss and SNHL group in percentage correct scores of monosyllables, consonants, vowels, and tones statistically (P > 0.05), but significant lower score was found in subgroup of non up-type hearing loss compared with SNHL group in these 4 percentage scores concerned (P < 0.001). Chi square test presented a significant difference in improper pattern proportion between AN and SNHL groups (P < 0.001), which could be related to more proportional tone recognition in the former's incorrect items. Improper pattern proportions between two AN subgroups presented a significant difference statistically (P < 0.001), which could be related to a larger proportional recognition of tones and vowels in subgroup of up-type hearing loss compared with subgroup of non up-type hearing loss. A poor performance might be a major clinical feature identified AN from SNHL in mandarin tone recognition. There are significant differences between AN patients with up-type hearing loss and patients with non up-type hearing loss in performance of monosyllable recognition and improper pattern proportion of tones and vowels. A psychophysical testing may be a key potential in diagnosis of AN in further clinical application.

Predicting Cochlear Implant Outcomes in Children With Auditory Neuropathy

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). Retrospective cohort study. The Sydney Cochlear Implant Centre and the Children's Hospital at Westmead. 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. 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. Melbourne speech perception score (MSPS) at 1 year and implant evoked electric auditory brainstem response (EABR). 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. 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.

A multicenter study on the prevalence and spectrum of mutations in the otoferlin gene (OTOF) in subjects with nonsyndromic hearing impairment and auditory neuropathy

Autosomal recessive nonsyndromic hearing impairment (NSHI) is a heterogeneous condition, for which 53 genetic loci have been reported, and 29 genes have been identified to date. One of these, OTOF, encodes otoferlin, a membrane-anchored calcium-binding protein that plays a role in the exocytosis of synaptic vesicles at the auditory inner hair cell ribbon synapse. We have investigated the prevalence and spectrum of deafness-causing mutations in the OTOF gene. Cohorts of 708 Spanish, 83 Colombian, and 30 Argentinean unrelated subjects with autosomal recessive NSHI were screened for the common p.Gln829X mutation. In compound heterozygotes, the second mutant allele was identified by DNA sequencing. In total, 23 Spanish, two Colombian and two Argentinean subjects were shown to carry two mutant alleles of OTOF. Of these, one Colombian and 13 Spanish subjects presented with auditory neuropathy. In addition, a cohort of 20 unrelated subjects with a diagnosis of auditory neuropathy, from several countries, was screened for mutations in OTOF by DNA sequencing. A total of 11 of these subjects were shown to carry two mutant alleles of OTOF. In total, 18 pathogenic and four neutral novel alleles of the OTOF gene were identified. Haplotype analysis for markers close to OTOF suggests a common founder for the novel c.2905_2923delinsCTCCGAGCGCA mutation, frequently found in Argentina. Our results confirm that mutation of the OTOF gene correlates with a phenotype of prelingual, profound NSHI, and indicate that OTOF mutations are a major cause of inherited auditory neuropathy.

Observations on Mastoid versus Ear Canal Recorded Cochlear Microphonic in Newborns and Adults

The cochlear microphonic (CM) may play an important role in the diagnosis of auditory neuropathy (AN) in newborns. However, since the CM tends to mirror the waveform of the acoustic stimulus, conscientious recording methodology must be applied to separate true response from artifact. The difficulty in achieving this separation has limited the clinical usefulness of the CM. In an effort to call attention to the importance of recording protocol when measuring the CM, the present study was designed to optimize CM recordings in humans by investigating the following parameters: (1) secondary minus electrode recording site (mastoid versus ear canal [EC]), (2) stimulus parameters, and (3) grounding and shielding conditions. Normative data were collected in full-term newborns (n = 7) and adults (n = 4) with no known risk factors for cochlear or retrocochlear pathology. Results suggest that the CM is easier to separate from stimulus artifact using an EC electrode and toneburst stimuli. In addition, electromagnetic shielding and grounding of the electrode cables and the acoustic transducer were effective in reducing and/or eliminating stimulus artifact. Results from this normative study may be helpful in improving the diagnostic utility of the CM in AN and other hearing-related disorders.

Vestibular nerve functions in children with auditory neuropathy

In disorders affecting the cochlear nerve it is highly probable that the vestibular nerve is involved as well. The caloric test and VEMP (vestibular evoked myogenic potentials) enable a separate evaluation of the inferior and superior vestibular nerve. In the present study we evaluated the inferior and superior vestibular nerves in three children with auditory neuropathy. Electrophysiological tests, VEMP and caloric tests were carried out in these three cases with the preliminary diagnosis of auditory neuropathy. Magnetic resonance imaging was obtained which revealed an intact cochlear nerve in all three patients. The caloric tests were all normal, while in two out of the three cases the VEMP test yielded abnormal results. Since the caloric test may prove abnormal as well, as reported in the literature, it would be valuable to carry out both of the tests in the vestibular evaluation of children with auditory neuropathy, in our opinion.

Potenciales evocados auditivos de estado estable en el estudio de dos pacientes con neuropatía auditiva

IntroductionWe described the results of the auditory multiple steady state response (MSSR) technique in the assessment of two patients with auditory neuropathy (AN). The aim of this study was to corroborate the correspondence between the MSSR generators elicited by amplitude modulated tones ranging between 80-100 Hz, with the generators of auditory brain stem response (ABR). Moreover, we would also try to demonstrate the validity of the MSSR in the diagnosis of AN in children. Material and MethodsTwo children diagnosed of hyperbilirrubinemia, aged, 18 months and 10 years have been studied with MSSR (500, 1000, 2000 and 4000Hz); ABR with clicks; OAE; behavioural audiometry; MRI and acoustic reflexes. ResultsA difference between electrophysiological and behavioural audiogram in both cases diagnosed with auditory neuropathy have been found. The auditory thresholds were similar using the two types of evoked potentials (MSSR and ABR). Both techniques showed an increment of auditory threshold congruous with a severe auditory impairment, while behavioural audiometry showed only a mild elevation of auditory threshold. We can also see how the threshold differed between frequencies using behavioral audiometry and MSSR. ConclusionIt is concluded that our findings are in agreement with previous studies and they sustain the theory about the coincidence of MSSR at fast rate (80-110 Hz) and ABR generators. Also, we demonstrate the usefulness of the MSSR as an objetive electroaudiometric tool in patients with auditory neuropathy as ABR. This technique is thus a recommendable test to complete the audiological study in infants with AN, to establish a more precise treatment.

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.

The Importance of Establishing a Protocol for Diagnosis of Auditory Neuropathy

The Importance of Establishing a Protocol for Diagnosis of Auditory Neuropathy

Pediatric cochlear implantation in auditory neuropathy.

Auditory neuropathy (AN) is characterized by varying degrees of sensorineural hearing loss, an absent or severely abnormal auditory brainstem response, and normal otoacoustic emissions. The nomenclature for this condition reflects the concept that the site of lesion is proximal to the cochlea (e.g., cochlear nerve). Given this hypothesis, it is reasonable to expect limited benefit from cochlear implantation in patients with AN. However, a growing body of evidence shows the striking benefits of cochlear implantation in AN. To explore this topic, we reviewed our population of children with AN and, specifically, the performance results in those children having undergone cochlear implantation. A retrospective case review of those patients diagnosed with AN from 1993 to 2001. A tertiary pediatric referral center. A diagnosis of AN reported from the Center for Hearing and Deafness Research, Cincinnati, OH, database. Eighteen patients were diagnosed with AN (11 girls, 7 boys), with 3 sets of siblings, including 1 set of identical twins. Four patients with AN underwent implantation in the previous 5 years. Twelve out of the 18 patients had classic risk factors for AN (e.g., prematurity and hyperbilirubinemia). The degree of hearing loss varied in our patients, with a majority showing severe to profound deficits. All children with implants showed improvement in auditory and verbal development, but this improvement was variable. The success of cochlear implantation in these patients suggests that some children with AN have an auditory system lesion that can be compensated for by cochlear implantation. This implies either an inner hair cell or inner hair cell-cochlear nerve junctional pathology that can be overcome by direct electrical stimulation.

Brief Report: The Cochlear Microphonic as an Indication of Outer Hair Cell Function

The extra-cellular cochlear microphonic is believed to be generated predominantly by outer hair cells and therefore it would seem reasonable to assume that the presence of a cochlear microphonic excludes outer hair cell dysfunction. Indeed, a diagnosis of auditory neuropathy might be, and has been, made on the basis of a cochlear microphonic present with an abnormal auditory brainstem response. Animal studies, however, have shown that the cochlear microphonic recorded from the round window is dominated by cellular generators located in the base of the cochlea. Primarily on this basis, it is argued that the presence of a cochlear microphonic does not exclude outer hair cell pathology and so outer hair cell integrity should not necessarily be inferred from the presence of the cochlear microphonic alone. In contrast, the absence of an otoacoustic emission in such cases is consistent with outer hair cell dysfunction.