Brainstem auditory evoked potentials in children with lead exposure

IntroductionEarlier studies have demonstrated an auditory effect of lead exposure in children, but information on the effects of low chronic exposures needs to be further elucidated.ObjectiveTo investigate the effect of low chronic exposures of the auditory system in children with a history of low blood lead levels, using an auditory electrophysiological test.MethodsContemporary cross-sectional cohort. Study participants underwent tympanometry, pure tone and speech audiometry, transient evoked otoacoustic emissions, and brainstem auditory evoked potentials, with blood lead monitoring over a period of 35.5 months. The study included 130 children, with ages ranging from 18 months to 14 years, 5 months (mean age 6 years, 8 months ± 3 years, 2 months).ResultsThe mean time-integrated cumulative blood lead index was 12 μg/dL (SD ± 5.7, range: 2.433). All participants had hearing thresholds equal to or below 20 dBHL and normal amplitudes of transient evoked otoacoustic emissions. No association was found between the absolute latencies of waves I, III, and V, the interpeak latencies I–III, III–V, and I–V, and the cumulative lead values.ConclusionNo evidence of toxic effects from chronic low lead exposures was observed on the auditory function of children living in a lead contaminated area.     

Prediction of hearing thresholds: Comparison of cortical evoked response audiometry and auditory steady state response audiometry techniques

The present study evaluated how well auditory steady state response (ASSR) and tone burst cortical evoked response audiometry (CERA) thresholds predict behavioral thresholds in the same participants. A total of 63 ears were evaluated. For ASSR testing, 100% amplitude modulated and 10% frequency modulated tone stimuli at a modulation frequency of 40Hz were used. Behavioral thresholds were closer to CERA thresholds than ASSR thresholds. ASSR and CERA thresholds were closer to behavioral thresholds at higher frequencies than at lower frequencies. Although predictions based on CERA thresholds are slightly more accurate than ASSR thresholds, the differences may not be clinically significant, particularly when the degree of individual variations is considered. Prediction of hearing thresholds became more accurate when hearing loss increased. Due to variations in prediction across participants, a single correction factor cannot be used. Other factors must be considered in selecting whether to use CERA or ASSR in predicting behavioral thresholds.     

Middle ear impedance studies in elderly patients implications on age-related hearing loss

IntroductionControversies arise with respect to functioning of the middle ear over time.ObjectiveTo assess changes in middle ear impedance that may be related to aging, and/or if there was an association of these changes with those of the inner ear in the elderly patients.MethodsCross-sectional, comparative study of elderly patients managed in ear, nose and throat clinics. A structured questionnaire was administered to obtain clinical information. Pure tone audiometry, tympanometry, and acoustic reflexes were performed. Comparative analyses were performed to detect intergroup differences between clinico-audiometric findings and middle ear measures, viz. tympanograms and acoustic reflexes.ResultsOne hundred and three elderly patients participated in the study; 52.4% were male, averagely 70.0 ± 6.3 years old, age-related hearing loss in 59.2%, abnormal tympanograms in 39.3%, absent acoustic reflex in 37.9%. There was no association between age and gender in patients with abnormal tympanograms and absent acoustic reflex. Significantly more patients with different forms and grades of age-related hearing loss had abnormal tympanometry and absent acoustic reflex.ConclusionSome abnormalities were observed in the impedance audiometric measures of elderly patients, which were significantly associated with parameters connected to age-related hearing loss.     

Relative contributions of auditory and cognitive functions on speech recognition in quiet and in noise among older adults

IntroductionHearing acuity, central auditory processing and cognition contribute to the speech recognition difficulty experienced by older adults. Therefore, quantifying the contribution of these factors on speech recognition problem is important in order to formulate a holistic and effective rehabilitation.ObjectiveTo examine the relative contributions of auditory functioning and cognition status to speech recognition in quiet and in noise.MethodsWe measured speech recognition in quiet and in composite noise using the Malay Hearing in noise test on 72 native Malay speakers (60–82 years) older adults with normal to mild hearing loss. Auditory function included pure tone audiogram, gaps-in-noise, and dichotic digit tests. Cognitive function was assessed using the Malay Montreal cognitive assessment.ResultsLinear regression analyses using backward elimination technique revealed that had the better ear four frequency average (0.5–4 kHz) (4FA), high frequency average and Malay Montreal cognitive assessment attributed to speech perception in quiet (total r² = 0.499). On the other hand, high frequency average, Malay Montreal cognitive assessment and dichotic digit tests contributed significantly to speech recognition in noise (total r² = 0.307). Whereas the better ear high frequency average primarily measured the speech recognition in quiet, the speech recognition in noise was mainly measured by cognitive function.ConclusionsThese findings highlight the fact that besides hearing sensitivity, cognition plays an important role in speech recognition ability among older adults, especially in noisy environments. Therefore, in addition to hearing aids, rehabilitation, which trains cognition, may have a role in improving speech recognition in noise ability of older adults.     

Cortical auditory evoked potential in assessment of neonates: a study about minimum level of responses in term and preterm newborns

IntroductionThe study of the threshold level of cortical auditory response in adults has been investigated in previous studies. Due to maturational issues, little is known about these responses in neonates. Technological advances with automatic analysis devices now allow investigation in specific populations. Thus, new studies are needed to establish the feasibility of using this auditory potential to identify the lowest levels of responses in children.ObjectiveVerify and compare latency and amplitude in 80 dBnNA and the minimum level of cortical auditory response in term and preterm neonates.MethodsA cross-sectional, comparative study involving 59 neonates, 35 full-term births and 24 preterm births, with positive results in the Neonatal Hearing Screening. The Hearlab system was used to investigate the P1i auditory potential with tone burst stimulus at frequencies of 500, 1000, 2000 and 4000 Hz. The minimum response level search ranged from 80 to 0 dBNA and was detected automatically. The results were compared between groups, evaluating the latency and amplitude in 80 dBNA and the minimum level of cortical auditory response.ResultsThe mean values obtained for the minimum level of cortical auditory response in term group were 26 ± 8.81; 26.14 ± 6.97; 29 ± 7.65 and 29.43 ± 7.04 dBNA and for preterm neonates of 31.96 ± 10.41; 34.13 ± 11.34; 33.64 ± 11.03 and 37.73 ± 11.92 dBNA, for the frequencies of 500, 1000, 2000 and 4000 Hz, respectively. There was a difference between groups for the latency of P1i at 4000 Hz and the minimum response levels at 500, 1000 and 4000 Hz, with higher values for preterm infants.ConclusionIt was possible to obtain latency and amplitude values at 80 dBnNA and the minimum level of cortical response in term and preterm newborns, with different results between groups, with higher values in those born preterm.     

感音神经性聋儿多频稳态诱发电位及短纯音听性脑干反应与行为测听的相关性

目的 比较多频稳态诱发电位（MASSR）、短纯音听性脑干反应（Tb—ABR）与感音神经性聋儿行为测试听阈的差值．研究MASSR和Tb—ABR反应阈与行为听阈之间是否存在相关性以及在不同听力损失聋儿、不同的频率之间的差异。方法 对60名感音神经性聋儿分别测试MASSR和Tb—ABR反应阈和行为听阈，评价MASSR反应阈、Tb—ABR反应阈与行为听阈的相关性。结果 MASSR反应阈、Tb—ABR反应阈和行为听阈之间均有较高的相关性。二者在频率为2、4kHz时，对行为听阈的预测具有相似的、较高的准确性；但在频率为0．5、1kHz时，MASSR的准确性较Tb—ABR高。结论 MASSR和Tb—ABR均可用作感音神经性聋儿言语频率客观听阈的预测，为低龄儿童及难以检测行为听力的患儿提供诊断依据。     

Auditory steady-state responses (ASSR): effects of modulation and carrier frequencies

Presented are results relevant to extending the utility of the auditory steady-state response (ASSR) in threshold estimation at high-frequency carriers and to the accuracy of thresholds estimated using modulation frequencies near 40 versus 80?Hz. Initially, efforts were directed at confirming various findings reported in the literature apropos effects of several basic ASSR parameters. Results supplement others’ observations suggesting that ASSR detection limits overestimate behavioral thresholds for conventional audiometric (carrier) frequencies from 500 to 4000?Hz. Further investigation revealed even greater errors of threshold estimates for 8000 and 12?000?Hz, by about 14 and 22?dB on average, respectively. Although suggesting high-frequency ASSR testing to be efficacious, technical advances and additional work is needed to establish clinical utility. Comparison of effects of modulation frequency suggested ASSR thresholds with 40?Hz modulation to fall closer to behavioral threshold than those estimated at 80?Hz. Consequently, when circumstances permit, 40?Hz ASSR testing may be the method of choice (e.g. in the assessment of malingers, who may be tested awake/alert).     

多频稳态诱发电位和听性脑干反应对感音神经性聋儿童客观听阈的评估

目的比较多频稳态诱发电位(MASSR)与短纯音听性脑干反应(Tb-ABR)对感音神经性聋儿童客观听阈的评估。方法对37名感音神经性聋儿童分别测试MASSR反应阈、Tb-ABR反应阈和行为听阈,参照行为听阈,比较MASSR反应阈和Tb ABR反应阈对行为听阈评估的准确性。结果MASSR反应阈、Tb-ABR反应阈和行为听阈之间均有较高的相关性。二者在频率为2、4kHz时,对行为听阈的评估具有相似的准确性;但在频率为0.5、1kHz时,MASSR的准确性较Tb ABR的准确性高。结论MASSR和Tb-ABR均可用作感音神经性聋儿童言语频率客观听阈的评估,但MASSR在低频(0.5、1kHz)时较Tb-ABR的准确性高。     

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.     

Hearing assessment by recording multiple auditory steady-state responses: the influence of test duration

The influence of test duration on the precision of hearing thresholds estimated by recording multiple auditory steady-state responses (ASSRs) was investigated. ASSR thresholds at four frequencies in both ears were assessed in 10 normal-hearing and 10 hearing-impaired subjects. The precision of the estimated hearing thresholds was compared for ASSR recordings of 5, 10 and 15 min per intensity level, corresponding to total test durations of approximately 30, 55 and 70 min for hearing-impaired ears. Furthermore, an intensity step size of 10 dB was compared to a step size of 5 dB. The mean difference scores averaged over the four frequencies were 15±10, 12±9 and 11±8 dB after recordings of 5, 10 and 15 min respectively. The corresponding Pearson correlation coefficients were 0.93, 0.95 and 0.96. Increasing the length of the separate recordings increases the precision of the estimates, independent of tested frequency. A compromise between both will have to be made. With a total test duration of approximately 1 h, four hearing thresholds in both ears can be estimated with a standard error of the estimate of 8dB.     

High levels of sound pressure: acoustic reflex thresholds and auditory complaints of workers with noise exposure

IntroductionThe clinical evaluation of subjects with occupational noise exposure has been difficult due to the discrepancy between auditory complaints and auditory test results. This study aimed to evaluate the contralateral acoustic reflex thresholds of workers exposed to high levels of noise, and to compare these results to the subjects’ auditory complaints.MethodsThis clinical retrospective study evaluated 364 workers between 1998 and 2005; their contralateral acoustic reflexes were compared to auditory complaints, age, and noise exposure time by chi-squared, Fisher's, and Spearman's tests.ResultsThe workers’ age ranged from 18 to 50 years (mean = 39.6), and noise exposure time from one to 38 years (mean = 17.3). We found that 15.1% (55) of the workers had bilateral hearing loss, 38.5% (140) had bilateral tinnitus, 52.8% (192) had abnormal sensitivity to loud sounds, and 47.2% (172) had speech recognition impairment. The variables hearing loss, speech recognition impairment, tinnitus, age group, and noise exposure time did not show relationship with acoustic reflex thresholds; however, all complaints demonstrated a statistically significant relationship with Metz recruitment at 3000 and 4000 Hz bilaterally.ConclusionThere was no significance relationship between auditory complaints and acoustic reflexes.     

Habituation and rate effect in the auditory cortical potentials evoked by trains of stimuli

Summary The effects of the stimulus repetition rate over the habituated auditory cortical evoked responses were studied. The stimulation pattern consisted of trains of pure tone bursts with interstimulus interval (ISI) of 1 s, and intertrain interval (ITI) of 5 s, delivered with constant time and intensity parameters during 93 min. The analysis of the responses was based upon across averaging of the trains, each single response being evaluated in the latency and amplitude parameters. Two time-dependent factors affected the responses in a distinct way: the habituation throughout the whole stimulation and the rate effect within the train. The linear regressions of the time/amplitude functions of the responses were calculated in relation to the duration of ISI and ITI. By introducing a correction factor depending on the repetition rate it was possible to evaluate the relationships between habituation and repetition rate. Changes in the repetition rate do not have any effect on the habituation process. The two phenomena are completely distinct, and they probably have neurophysiologic substrates corresponding to different levels in the central nervous system (CNS).     

Threshold prediction in children with sensorioneural hearing loss using the auditory steady-state responses and tone-evoked auditory brain stem response

Objective

The purpose of this study was to compare ASSRs to tone-evoked ABR and to behavioral thresholds obtained on follow-up audiometry at 500, 1000, 2000, and 4000 Hz in infants and young children.

Methods

The study included 17 infants and young children ages between 2 months and 3 years old, with sensorineural hearing loss. The ASSRs thresholds were compared with the tone-evoked ABR thresholds, and with the behavioral thresholds obtained on follow-up audiometry.

Results

The correlation of tone-evoked ABR and ASSRs thresholds at 500, 1000, 2000 and 4000 Hz was 0.91, 0.76, 0.81, 0.89, respectively. ASSRs and behavioral hearing thresholds obtained on follow-up were highly correlated, with Pearson r values exceeding 0.94 at each of the test frequencies.

Conclusions

Multiple ASSRs have strong correlations to tone-evoked ABR and to behavioral thresholds obtained during follow-up in hearing impaired infants and young children. These results might be useful in order to provide further evidence for the use of multiple ASSRs, as an alternative tool to tone-evoked ABR, although further data are still required.     

听觉事件相关电位汉语言语测试信号的编制与初步应用

目的编制一套符合言语测试要求和适合我国国情的以汉语普通话为刺激声的听觉事件相关电位（auditory event--related potentiaI,AERP）言语测试信号。方法根据汉语语言特点及言语测听的要求筛选出汉语字表,将字表通过立体录音、剪辑、转换,编辑成言语测试信号与现行设备兼容。结果编制出包含有韵母识别表和声母识别表的言语刺激信号,经使用符合AERP测试和言语测试要求,并获得了满意的测试结果。结论AERP的汉语言语测试信号软件可以很好地应用于AERP测试并符合中国国情。     

Frequency and age-dependent auditory evoked potential thresholds in infants

Auditory evoked-potential thresholds to 0.5, 4.0 and 10.0 kHz tone pips were measured in 40 normal infants 2–28 wks old and 14 normal hearing adults. Thresholds to 500 Hz tone pips were based upon the steady-state, 40 Hz. evoked potential. Thresholds to 4.0 and 10.0 kHz tone pips were based upon the brainstem response. Stimulus intensity was varied in 5-dB steps for threshold search. The greatest difference between infant and adult thresholds occurred at 4.0 kHz. The magnitude of this difference decreased with age; however, differences were still significant up to 28 wks of age. No significant differences were seen at 500 Hz. To the 10.0 kHz stimulus only the youngest (2–4 wk) infants had thresholds that were significantly higher than adults. The reasons proposed to explain these results are complex interactions between immaturity of the conductive mechanism, brainstem pathways, and possibly the cochlea.     

Steady-state response audiometry in a group of patients with steeply sloping sensorineural hearing loss

OBJECTIVES: The purpose of this study was to examine the predictive value of auditory steady-state response (ASSR) evoked potential thresholds and predicted behavioral thresholds in a group of children with steeply sloping sensorineural hearing loss (HL). STUDY DESIGN: Case series. METHODS: Twenty-nine children with sloping sensorineural HL underwent behavioral audiometric evaluation, impedance testing, distortion product otoacoustic emissions, and steady-state response testing. A t test was performed to compare the means of ASSR predicted behavioral thresholds and behavioral responses. Pearson correlation coefficients were calculated at each tested frequency, 500 Hz, 1,000 Hz, 2,000 Hz, and 4,000 Hz, using the same data. RESULTS: Bracketed thresholds were obtained at 500 Hz, 1,000 Hz, 2,000 Hz, and 4,000 Hz. Nineteen ears were used in this evaluation. A comparison of threshold difference as a function of bracketing revealed that the means were statistically different (P < .05). The mean threshold differences were calculated, and Pearson r values were determined between the behavioral thresholds and the predicted thresholds using the Rance 95 algorithm. The results revealed no difference of means at 500 Hz between predicted and measured behavioral thresholds. Linear regression analysis revealed strong correlation at 500 Hz, 1,000 Hz, and 2,000 Hz. CONCLUSIONS: The GSI Audera appears to predict the configuration of HL in children with steeply sloping sensorineural HLs and over-predicts the severity of the loss by 15 to 20 dB above 500 Hz at each test frequency (1,000, 2,000, and 4,000 Hz). Correlation coefficients display a strong correlation at 500 Hz, 1,000 Hz, and 2,000 Hz.     

声场中记录的听性稳态助听反应阈与行为测试助听听阈的相关性

目的 应用多频听觉稳态反应(ASSR)Chirp刺激信号在声场中测试助听反应阈,观察其阈值与行为测试助听听阈的相关性,探讨多频听觉稳态反应Chirp刺激信号声场测试评估助听器补偿效果的临床意义.方法 选取22例(39耳)重度感音神经性听力损失、已配戴助听器的患儿(听障组)和16例(32耳)听力正常儿童(对照组)为研究对象.应用国际听力Eclipse EP25型多频稳态诱发电位仪及美国GSI-61型听力计,分别对听障组在声场中使用两种仪器测试助听听阈;对对照组进行裸耳行为听阈与声场中听觉稳态反应阈测试.结果 在0.5、1、2、4 kHz处,听障组ASSR助听反应阈与行为助听听阈的相关系数分别为0.65、0.68、0.77和0.82,P值均<0.01,显示两种测试结果有相关性;对照组裸耳行为听阈与声场中记录的听觉稳态反应阈在0.5、1、2、4 kHz配对t检验均呈显著差异(P<0.01),ASSR声场反应阈高于行为听阈20～30 dB HL.结论 应用多频听觉稳态反应Chirp刺激信号声场测试进行助听器补偿效果评估在临床上具有可行性.     

Developmental changes of susceptibility to auditory fatigue in young hamsters

Susceptibility to auditory fatigue was studied in young hamsters by using an evoked-potential criterion of sound-induced threshold shift. Animals aged 15, 28, 40, 54 and 85 days were anesthetized and stimulated with a continuous tone (3 kHz, 110 dB SPL) for 10 min. Threshold shifts 1 min post-exposure were highest in animals aged 40 days, and lowest in animals aged 15 or 85 days. Threshold shifts recovered within 100 min in 15- and 85-day-old animals, but required considerably longer to recover in the other age-groups. The data suggest that young hamsters pass through a critical period of susceptibility to auditory fatigue. Comparison of this critical period with various indices of the development of hearing in the hamster suggests that the developmental events under-lying the critical period do not occur in the middle ear.     

Chronological changes of auditory brainstem responses in Cockayne''s syndrome

Cockayne's syndrome (CS) is a rare autosomal recessive premature-aging disorder which is clinically characterized by physical and mental retardation, retinal pigmentation, sensorineural deafness and other neurological abnormalities. Auditory brainstem responses (ABRs) and behavioral audiometry were studied in 4 cases of confirmed CS chronologically. In one case, ABRs were normal at first but became abnormal. Initially, ABRs revealed only wave I with prolonged latency and thereafter no response. In another case, ABRs revealed the absence of all waves beyond wave III and then revealed the disappearance of all waves. In 2 other cases, ABRs were absent from the first testing. Behavioral levels were elevated in all 4 cases. In 2 cases, behavioral levels did not change in spite of partial disappearance of ABR waves, but they had elevated severely since all waves including wave I disappeared. Our findings suggest that the disease spreads from the upper brainstem to the cochlear nerve and that the site of the lesion causing hearing loss in CS is in the brainstem lesion as well as the peripheral one.