Plasticity of the auditory system: theoretical considerations

Auditory plasticity refers to the possibility of anatomical and/or functional changes in the system where transmission of auditory information takes place. The auditory system is often required in communication; it is important to learn how the auditory system reacts to stimuli in order to improve performance in individual communication of subjects with impaired hearing.AimTo review the literature on auditory plasticity and the possibility and ability of plastic responses in the auditory system; also to review the evidence of auditory plasticity.MethodologyA review of the Brazilian and international literature (journals, books, and graduate studies) was carried out. The MEDLINE, SCIELO, BIREME, PUBMED, and LILACS data bases were consulted, as well as 24 papers from the 1990s to the present date; each paper was assessed for relevance to the topic.ConclusionThe findings showed that the auditory system is able to reorganize itself if there is variation, whether by by reducing, increasing, or conditioning of sound stimuli. This is evidence of plasticity in the auditory system.     

Role of auditory stimulation in maturation of the auditory pathway

Objective To compare the maturation of the auditory pathway, as shown by electrical brainstem auditory potentials (EABRs), in ears with and without prior auditory stimulation.

Material and Methods Electrophysiological data were collected prospectively from ears which had received cochlear implants. Implant-evoked (Imp)EABRs were recorded. Thirty children, implanted after January 2000, were selected according to a strict inclusion/exclusion protocol. All the children had received a 22-channel Nucleus cochlear implant (CI24 series). Intraoperatively, ImpEABRs were recorded using the Medelec Synergy® Evoked Response system in conjunction with Nucleus Neural Response Telemetry® software. The ImpEABR latencies of waves eII, eIII and eV and the morphology of wave eV were assessed.

Results ImpEABRs alter during the first 12 months of life. The latency becomes shorter during this period and the morphology of wave eV alters from a broad shape to a more distinct waveform. This appears to occur independently, even in the absence of auditory stimulation.

Conclusion The development of electrical brainstem auditory potentials is not dependent on auditory stimulation.     

Electro acoustic stimulation of the auditory system: UNICAMP's surgical approach

A new era has arrived in auditory rehabilitation with the introduction of new technologies such as electroacoustic stimulation (EAS). EAS is indicated for patients with residual hearing at low frequencies and severe or profound hearing loss at high frequencies. These patients have no indication for conventional cochlear implant and have difficulties in adapting to individual sound amplification devices. Preservation of hearing is vital in this process; the surgical technique must be based on this concept.ObjectivesTo present the cochlear implant surgical technique with MED-EL Mand FlexEAS to preserve hearing in patients with hearing loss at high frequencies and to maintain low frequency hearing. We are the first institution to carry out this treatment in Brazil.MethodsA case report of the surgical technique carried out in four patients; the procedure was carried out by the cochlear implant group of a specialized clinical hospital.ResultsThe procedures were successful and uneventful.ConclusionWe described the technique used at our institution for implants using EAS; the surgical technique is complex and includes steps for preservation of hearing.     

Comparison of auditory steady-state response and click-evoked auditory brain response in infants with different types and degrees of hearing loss

Abstract

Background: Auditory steady-state response (ASSR) and click-evoked auditory brain response (c-ABR) have been used for hearing assessment for decades years, the correlation of the two methods and the effects of type and degree of hearing loss (HL) to the correlation in infants younger than 6?months of age are unclear.

Objectives: To compare the correlation of ASSR and c-ABR and then to analyse the effects of type and degree of HL on the correlation in infants younger than 6?months of age.

Material and methods: Retrospective study comparing ASSR thresholds at various frequencies with c-ABR thresholds. 182 ears from 96 infants were assessed and classified according to types and degrees of HL.

Results: The correlation coefficients were: 0.823, 0.864, 0.891, 0.871, 0.908, 0.915 and 0.913 between ASSR thresholds at 0.5, 1, 2, 4, 2–4, 1–2–4, 0.5–1–2–4?kHz and c-ABR thresholds respectively. The correlation coefficients in the group of sensorineural HL (SHL) (r?=?0.763–0.900) were higher than conductive HL (r?=?0.309–0.619) across all frequencies. The coefficients of severe-profound SHL (r?=?0.595–0.790) were higher than mild-moderate SHL (r?=?0.434–0.687) across all frequencies.

Conclusions and significance: ASSR was one valuable cross-check measure by providing frequency specific information in auditory assessment.     

听神经病病损部位分析

目的：探讨一组以言语听力下降为主的听力损失的命名、临床特点、病损部位。方法：分析１１例低频或以低频为主的感音神经性听力损失患者的临床症状、纯音测听、声导抗测试、听性脑干反应、耳蜗电图、畸变产物耳声发射～ＣＴ和（或）ＭＲＩ资料。结果：本组病例具有下列矛盾现象;主诉进行性听力闰退,尤其听不清语言,纯音听阈呈上升型听力图,听性脑干反应引不同或明显异常,甚经４０００Ｈｚ纯音听琢怕主观阈严重镫骨肌反引不出;     

豚鼠听觉脑干电反应信号小波变换分析

目的：将小波变换这种时频域信号分析方法用于豚鼠听觉脑干电位分析,以了解小波变换是否适用于ＡＢＲ信号分析,较之传统法有否优越之处。方法 雄性纯白豚鼠３０只分成正常,传导性聋,感音性聋三组,每组１０只,要集各组７５ｄＢｎＨＬ短声诱发的ＡＢＲ,用小波处理软件进行变换,将变换前后信号的时域值作配对统计处理,结果 小波２尺度变换使原信号失真,４尺度变换增加原信号的背景噪声,３尺度变换可保持原信号的时域特征,     

LittlEARS auditory questionnaire as an infant hearing screening in Germany after the newborn hearing screening

Objective: To investigate the feasibility of using the LittlEARS® Auditory Questionnaire (LEAQ®) as part of the infant hearing screening programme in Germany.

Design: LEAQ®s were distributed to 47 paediatric practices and were completed by the parents/guardians of the infants (aged between 9-14?months) involved in the study (= LEAQ^® screening). The infants who failed the LEAQ^® screening were invited to a LEAQ rescreening. Infants who failed the LEAQ^® rescreening were sent to a paediatric ENT specialist. After 3?years, a follow-up was performed on two groups: the first group comprised infants who failed the LEAQ screening; the second group (control group) comprised 200 infants who passed the LEAQ screening.

Study Sample: 5316 questionnaires were returned.

Results: Six infants with permanent hearing loss were identified using the LEAQ^® as a screening tool.

Conclusions: An infant hearing screening using the LEAQ^® is easily implementable in paediatric practices and may be a good alternative in countries where no objective screening instruments are available. The LEAQ^® was suitable for monitoring hearing development in infants in general and could help to identify a late-onset or progressive hearing loss in infants.     

Auditory steady-state response and auditory brainstem response thresholds in children

The inclusion of the auditory steady-state response (ASSR) into test-batteries for objective audiometry has allowed for clinical comparisons with the most widely used procedure, the auditory brainstem response (ABR). The current study describes ASSR and ABR thresholds for a group of infants and young children with various types and degrees of hearing loss. A sample of 48 subjects (23 female) with a mean age of 2.8 ± 1.9 years SD were assessed with a comprehensive test-battery and classified according to type and degree of hearing loss. Thresholds were determined with a broadband click-evoked ABR and single frequency ASSR evoked with continuous tones (0.25–4 kHz) amplitude modulated (67–95 Hz). Mean difference scores (±SD) between the ABR and high frequency ASSR thresholds were 9.8 (±11), 3.6 (±12) and 10.5 (±12) dB at 1, 2 and 4 kHz, respectively. An ASSR mean threshold for 2–4 and 1–4 kHz compared to the ABR threshold revealed an average difference of 7 (±9) and 7.9 (±8) dB, respectively. The overall correlation between the ABR and ASSR thresholds was highest for the mean ASSR thresholds of 2–4 and 1–4 kHz (r = 0.92 for both conditions). Correlations between the ABR and individual ASSR frequencies were slightly less (0.82–0.86). The average of the 2–4 kHz ASSR thresholds correlated best with the click-evoked ABR for all categories of hearing loss except for the sensorineural hearing loss category for which the 1–4 kHz ASSR average was better correlated to ABR thresholds. Findings demonstrate the reliability of verifying high frequency ASSR thresholds with a click-evoked ABR as an important cross-check in infants for whom behavioural audiometry may not be possible.     

An auditory health program for neonates in ICU and/or intermediate care settings

Auditory screening and early identification and management of patients with hearing loss improve the development prospects of infants.ObjectiveTo analyze the outcomes produced by an Auditory Health Program in neonates managed in an intensive care unit.MethodThis prospective cross-sectional study enrolled neonates referred to the neonatal care unit at hospital CAISM/Unicamp with stays lasting for 48 hours and more within a period of 13 months.Automated monitoring of brainstem auditory evoked potentials was used in the auditory screening of neonates at the time of discharge. Children with poor BAEPs were sent to undergo audiological, otorhinolaryngological, and genetic tests.ResultsAuditory screening was performed for 84.7% of the live births; 39.7% were screened at 30 days or more of age. Diagnostic tests revealed that 63.8% of the children had normal hearing. Incidence of hearing loss was 4%; sensorineural hearing loss was observed in 1.4% of the subjects; 0.24% had auditory neuropathy spectrum disorder; and 2.2% had conductive hearing loss.ConclusionNeonatal auditory screening was not offered universally, and nor was it carried out, in many cases, within the child's first month of life. Screening must be performed before neonates are discharged and in more than one stage. A high incidence of hearing loss was observed.     

对乙酰氨基酚致小鼠听觉损伤的实验研究

目的：研究对乙酰氨基酚对小鼠听觉的影响。方法：健康7周龄C57小鼠40只，雌雄不分，随机分为4组：对乙酰氨基酚低剂量组（150mg／kg）、中剂量组（300mg／kg）、高剂量组（600mg／kg）及空白对照组（2ml生理盐水）。每组10只。观察每组于喂药第0、2、4、9天ABR反应阈，通过免疫荧光法观测耳蜗基膜毛细胞形态学改变，用高效液相色谱法测定小鼠耳蜗内淋巴液中对乙酰氨基酚浓度。结果：对乙酰氨基酚灌胃30min后，检测小鼠耳蜗内淋巴中对乙酰氨基酚的浓度，内淋巴中药物浓度与灌服剂量相关。对乙酰氨基酚各组随给药时间延长ABR听阈增高，中、高剂量组给药后9d的平均阈值分别为（44．75±16）dB、（50．00±11．00）dB，与对照组比较差异均有统计学意义（均P〈0．05）；随着灌服时间的延长，对乙酰氨基酚各组的免疫荧光镜显示内、外毛细胞出现不同程度的缺失。结论：对乙酰氨基酚可通过血迷路屏障进入内耳，服用一定剂量的对乙酰氨基酚可造成小鼠听力损伤。     

Central auditory dysfunction associated with exposure to a mixture of solvents

Abstract

Objective: The aim of the present research was to investigate central auditory functioning in normal-hearing, solvent-exposed subjects compared to normal-hearing subjects without solvent exposure, with a comprehensive test battery of behavioural central auditory functioning procedures. Study sample: Forty-six normal-hearing, solvent-exposed subjects and 46 normal-hearing, control subjects were selected to participate in the study. Design: All subjects must present with normal hearing thresholds and absence of history of variables related to the onset of auditory dysfunction. Subjects were evaluated with a test battery comprising pure-tone audiometry (PTA), dichotic digits (DD), pitch pattern sequence (PPS), filtered speech (FS), random gap detection (RGD), masking level difference (MLD), and hearing-in-noise (HINT) tests. Results: Analyses of covariance (ANCOVA) were performed to compare the mean values of the dependent variables (results for DD, PPS, FS, RGD, MLD, and HINT) between solvent-exposed and control subjects. Age and average hearing thresholds (500–8000 Hz) were included in the analyses as covariates. Significant differences for DD, PPS, FS, and RGD results were found between groups. Conclusion: This study provides further evidence of the central auditory dysfunction associated with solvent exposure.

Sumario

Objetivo: El objetivo de este trabajo fue investigar el funcionamiento auditivo central en personas con audición normal expuestas a solventes, comparados con sujetos normales sin exposición a solventes, por medio de una batería integral de procesos de funcionamiento comportamental auditivo central. Muestra de estudio: Se seleccionaron cuarenta y seis sujetos normo-oyentes expuestos a solventes y 46 sujetos normales como grupo control, para participar en este estudio. Diseño: Todos los sujetos deb an presentar umbrales auditivos normales y ausencia de datos de variables relacionadas con el inicio de disfunción auditiva. Los sujetos fueron evaluados con una batería de pruebas que comprendió la audiometr a por tonos puros (PTA), Digitos dicóticos (DD), Secuencia de patrones de frecuencia (PPS), Lenguaje filtrado (FS), Detección de intervalos al azar (RGD), diferencia de niveles de enmascaramiento (MLD) y Audición en ruido (HINT). Resultados: se realizó el análisis de covarianza (ANCOVA) para comparar los valores de las variables dependientes (resultados de DD, PPS, FS, RGD, MLD y HINT) entre los sujetos expuestos a solventes y los del grupo control. La edad y los umbrales auditivos promedio (500–8000 Hz) se incluyeron en el análisis como covariables. Se encontraron diferencias significativas con los resultados para DD, PPS, FS y RGD entre ambos grupos. Conclusión: Este estudio proporciona evidencias adicionales de disfunción audtiva central asociada a la exposición a solventes.     

Prevalence of auditory neuropathy spectrum disorder in an auditory health care service

Auditory neuropathy spectrum disorder (ANSD) is characterized by impairment of the auditory nerve associated with preservation of outer hair cell function.ObjectiveTo establish the prevalence of ANSD in subjects with sensorineural hearing loss (SNHL).MethodThis retrospective study was carried out between 2010 and 2012 and included the charts of 2,292 individuals with SNHL. Data from otolaryngological and audiological examinations based on pure-tone and speech audiometry, impedance tests, otoacoustic emissions (OAEs), and brainstem auditory evoked potentials (BAEPs) were collected. Inclusion criteria: presence of OAEs and/or cochlear microphonic (CM); absent or altered BAEPs, and normal MRI scans of the brain.ResultsTwenty-seven (1.2%) of the 2,292 subjects with SNHL had ANSD (37% males; 63% females). Mild SNHL was seen in 29.6% of the individuals with ANSD; 55.5% had moderate SNHL; 7.4% had severe SNHL; and 7.5% had profound SNHL. In terms of age, 14.8% were aged between zero and 20 years, 44.1% were 41 to 60 years old, and 7.4% were above the age of 60.ConclusionANSD was seen in 1.2% of the individuals with SNHL included in this study.