Patients with auditory neuropathy/dys-synchrony lack efferent suppression of transient evoked otoacoustic emissions

Function of the olivocochlear reflex, measured by suppression of transient evoked otoacoustic emissions, is assessed in nine patients with bilateral auditory neuropathy/dys-synchrony and compared to matched control subjects with normal auditory function. TEOAEs were acquired using 65 dB peak sound pressure linear clicks with and without the presence of broad-band noise presented binaurally, ipsilaterally, or contralaterally in a forward masking paradigm. Efferent suppression differed significantly between subject groups (p < .0001). Mean suppression was less than 0.22 dB across all suppressor noise conditions for the auditory neuropathy/dys-synchrony subjects. TEOAE suppression averaged 4.47 (binaural), 2.41 (ipsilateral), and 1.52 (contralateral) dB in the control subjects. Suppression characteristics across the three suppressor conditions were also assessed in one patient with unilateral auditory neuropathy/dys-synchrony. The results suggest that poor efferent responses are related to compromised afferent input to the OCR pathway and support the use of efferent suppression of otoacoustic emissions as a differential measure of auditory function in patients with auditory neuropathy/dys-synchrony.     

Prevalence and audiological characteristics in individuals with auditory neuropathy/auditory dys-synchrony

The objectives of this study were to (a) estimate the prevalence of auditory dys-synchrony in Mysore, a city of one million population in Southern India and, (b) present the results of audiological testing of this clinical population as well as the relationship between these figures. A register-based study design was employed wherein the results of audiological tests of all patients who visited the Department of Audiology, All India Institute of Speech and Hearing between January 2000 and December 2003 were reviewed. Results showed that the prevalence of auditory dys-synchrony was around 1 in 183 in individuals with sensory neural hearing loss. Behavioural thresholds and speech identification scores were variable. Around 60% of the individuals had no measurable speech identification scores. There was no relation between the hearing thresholds and speech identification scores or between otoacoustic emissions and speech identification scores. These results indicate that auditory dys-synchrony is not an extremely rare disorder.     

Prevalence and audiological characteristics in individuals with auditory neuropathy/auditory dys-synchrony

The objectives of this study were to (a) estimate the prevalence of auditory dys-synchrony in Mysore, a city of one million population in Southern India and, (b) present the results of audiological testing of this clinical population as well as the relationship between these figures. A register-based study design was employed wherein the results of audiological tests of all patients who visited the Department of Audiology, All India Institute of Speech and Hearing between January 2000 and December 2003 were reviewed. Results showed that the prevalence of auditory dys-synchrony was around 1 in 183 in individuals with sensory neural hearing loss. Behavioural thresholds and speech identification scores were variable. Around 60% of the individuals had no measurable speech identification scores. There was no relation between the hearing thresholds and speech identification scores or between otoacoustic emissions and speech identification scores. These results indicate that auditory dys-synchrony is not an extremely rare disorder.     

听神经病患者80Hz听觉稳态诱发电位研究

目的:探讨听神经病患者80 Hz听觉稳态诱发电位的特点及与听性脑干诱发电位V波的相关性.方法:以1000 Hz短音95 dBnHL作声刺激,比较听神经病组和正常对照组80 Hz听觉稳态诱发电位及短音听性脑干反应(ABR)的波形差异.结果:听神经病组两种听觉诱发电位波形的同时引出率为85.4%且波幅低或极低,ABR的Ⅰ、Ⅲ波消失;14.6%两种听觉诱发电位波形同时消失.而正常对照组两种波形的同时引出率为100.0%.结论:80 Hz听觉稳态诱发电位与听性脑干反应的V波有明显相关性.     

Auditory neuropathy/auditory dys-synchrony detected by universal newborn hearing screening

The implementation of neonatal hearing screening has enabled early detection and intervention in hearing loss. The use of otoacoustic emissions (OAE) and auditory brainstem response testing in universal screening has led to the recognition of this recently described disorder called auditory neuropathy/auditory dys-synchrony (AN/AD). This diagnosis indicates that the infant has significant hearing loss despite having normal outer hair cells in the cochlea. We reviewed the characteristics and natural history of nine infants detected to have AN/AD from universal newborn hearing screening in a national pediatric hospital. Fifty-two cases of hearing loss were detected from 14,807 consecutively screened cases. Of the 52 cases, 9 had electrophysiological test results consistent with AN/AD. They include both premature infants who had major neonatal complications and term infants with no perinatal complications. Six cases had bilateral and three cases had unilateral findings. We suggest that AN/AD can occur in low-risk infants and hence screening of high-risk cases alone is insufficient. Our findings are discussed with reference to the current literature.     

Speech perception in noise for children with auditory neuropathy/dys-synchrony type hearing loss

OBJECTIVE: To evaluate the effect of background noise on speech perception in children with auditory neuropathy/dys-synchrony (AN/AD) type hearing loss. DESIGN: Open and closed-set speech perception abilities were assessed in 12 school-age children who had been diagnosed with AN/AD in infancy. Data were also obtained from a cohort of subjects with sensorineural (SN) hearing loss and from a group of normal-hearing children. RESULTS: Closed-set speech understanding was more affected by the presence of a competing signal in the hearing impaired than in the normal-hearing subjects. The mean S/N ratio required to identify a spondee in noise was -11.5 +/- 2.0 dB for the normal group, whereas the ratio required for the SN group was -5.4 +/- 5.1 dB and for the AN/AD group was -2.5 +/- 4.7 dB. Closed-set perception in noise was not significantly different for the AN/AD children and their SN counterparts although there was a trend toward poorer performance in the AN/AD group. The effect of background noise on open-set speech perception was also similar across hearing-impaired subjects although again, the AN/AD cohort tended to show greater difficulties in noise than their SN peers. CONCLUSIONS: Listening in background noise was more difficult for our group of children with AN/AD-type hearing loss than for their normal-hearing peers. However, the noise effects were not consistent across subjects and some children demonstrated reasonable perceptual ability at low signal-to-noise ratios. The ways in which speech understanding is affected by competing signals may be different for different types of hearing deficit, but the results of this investigation indicate that significant perceptual disruption occurs both in children with auditory neuropathy/dys-synchrony and sensorineural type hearing loss.     

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.     

小儿听神经病或听同步不良患者耳蜗植入术前的电生理评估

1996年Starr等用听神经病（auditory neuropathy，AN）来描述一组以诱发性耳声发射正常、听性脑干反应（auditory brmnstem response，ABR）缺失或严重异常为特征的听功能障碍。听神经病的命名，直觉上是指神经功能异常，因而一度使得临床听力学家怀疑听神经病患者植入人工耳蜗的可行性。尽管临床医生在手术前对所报道病例的植入效果并没有把握，但2000年以来，陆续有一些关于听神经病患者植入人工耳蜗后获益的报道。然而并非所有的听神经病患者都能从中获益。这似乎提示有一部分听神经病患者的听神经能够传送电脉冲刺激，其病理机制可能是听同步不良（auditory dys-synchrony，AD）而非听神经病变。因而，如何在术前确定患者的病变部位及听神经功能，就成了摆在临床听力学家面前的一道难题。     

Brain stem auditory evoked potentials in patients with hemifacial spasm

Brain stem auditory evoked potentials (BSEP) were elicited and recorded from the spasm side and from the non-spasm side of 39 patients operated upon to relieve hemifacial spasm. Thirty-seven patients were studied before the microvascular decompression surgery at the root entry zone of the facial nerve was performed. Thirty-one patients were studied 4 to 10 days postoperatively, and 7 were evaluated a second time, 6 weeks to 6 months after surgery. The latencies of peaks III and V of the ipsilaterally recorded BSEP were statistically significantly (p<0.05) larger on the spasm side than were those recorded on the non-spasm side. The I to III interwove latencies did not show any statistically significant difference. This implies that the effects of hemifacial spasm are not limited to the facial nerve but extend to other cranial nerves and other parts of the brain stem than those involved in facial motor function. The pure tone thresholds recorded before and after the operations were essentially the same in the majority of the patients, were 10 to 15 dB lower in 13% of the patients postoperatively, and were 10 to 15 dB higher in 13% of the patients postoperatively. One patient suffered a moderate sensorineural low-frequency hearing loss postoperatively.     

Speech and language outcomes in children with auditory neuropathy/dys-synchrony managed with either cochlear implants or hearing aids

The aim of this study was to assess the receptive language and speech production abilities of a group of school-aged children with auditory neuropathy/dys-synchrony-type hearing loss. Ten children who had received a cochlear implant in one or both ears participated. Findings for this group were compared with those for a matched cohort of implanted children with other forms of sensorineural hearing loss and with those for a group of auditory neuropathy/dys-synchrony children who were long-term hearing aid users.

Results for 9 of the ten implanted children with auditory neuropathy/dys-synchrony were similar to those of the general population of paediatric implant recipients. (One child, who gained little perceptual benefit from his device, showed severely delayed spoken language development). Results for the group of aided auditory neuropathy/dys-synchrony subjects were comparable to those for their implanted counterparts suggesting that affected children should not automatically be considered cochlear implant candidates.