Distortion-product otoacoustic emissions in human newborns and adults.

Cubic distortion-product otoacoustic emissions (DPEs) may have clinical and research applications. We reliably recorded DPEs at some frequencies in all of the normal-hearing human adults and newborns tested. Adult and newborn DPEs were of comparable amplitude, with the exception that a prominent dip between 1 and 3 kHz in the adult data was less evident in the newborn data. DPE amplitude was a linear function of the intensity of the eliciting primary stimuli. The slopes of the linear input-output functions increased with increasing frequency. Except at the highest frequencies assessed, adult input-output functions were steeper than newborn input-output functions.     

Distortion-product and click-evoked otoacoustic emissions in healthy newborns.

Distortion-product otoacoustic emissions (DPOEs) are believed to provide frequency-specific information about cochlear function. The DPOEs have been reported in the adult population but have not been reported previously in the neonatal population. We recorded DPOEs from a group of healthy full-term newborn human subjects (35 ears) to establish the characteristics of these emissions in the newborn population. To our knowledge, this is the first study of DPOEs in newborns. The "DPOE audiograms" from the newborns tested revealed characteristics qualitatively similar to those seen in adults with normal hearing. This study demonstrates the feasibility of DPOE measurements among newborns and provides a normal baseline for this age group, thus fulfilling a necessary step toward the development of an objective, noninvasive frequency-specific test of cochlear function. Click-evoked otoacoustic emissions were also recorded from the newborn population and compared with click-evoked otoacoustic emissions from adults. The spectrum of the click-evoked emissions was variable and individualistic, similar to findings previously reported in adult subjects. The click-evoked otoacoustic emissions of the newborns had a higher overall level and contained stronger high-frequency (4.5 to 6 kHz) spectral components than those of the adults. We also found that the low-frequency components of the click stimulus spectrum were attenuated in the neonatal ears exhibiting a high-pass slope below about 2.5 kHz, whereas the stimulus spectrum was nearly flat in this frequency region in adult ears.     

Distortion-product otoacoustic emissions and glycerol testing in endolymphatic hydrops

OBJECTIVES/HYPOTHESIS: Aural fullness is a frequent symptom of endolymphatic hydrops. Its evaluation may provide valuable information on the initial stage of development of endolymphatic hydrops. STUDY DESIGN: The present investigation was specifically designed to ascertain the ability of the glycerol test, combined with pure tone audiometry and distortion product otoacoustic emissions (DPOAEs) testing, to diagnose endolymphatic hydrops early and to identify patients who may evolve toward Meniere's disease. For these purposes, patients who complained about aural fullness as their only audiologic symptom were selected. METHODS: This investigation consisted of 19 consecutive patients with unilateral or bilateral aural fullness who received no treatment. Each patient underwent glycerol testing measured with conventional pure tone audiometry and with both DPOAEs. For the traditional pure-tone glycerol test, a hearing improvement of at least 10 dB, at the lower two or three frequencies (125, 250, and 500 Hz), was judged as a positive result. For the DPOAE glycerol test, a smaller positive difference (5 dB) for at least three frequencies was interpreted as an ameliorative fluctuation. RESULTS: The outcomes of the glycerol tests (24 ears examined) showed variable patterns. Seven ears showed no significant changes of either the pure-tone audiogram or DPOAE. In seven other ears, the comparison of the traditional glycerol test and the DPOAE glycerol test indicated an improvement in both measures. Another seven ears showed negative glycerol tests, whereas DPOAE responses gradually recovered reaching levels significantly higher than those recorded before glycerol administration. The three remaining ears showed contrasting results. CONCLUSIONS: Patients with aural fullness in the absence of other associated symptoms may potentially be in the initial stages of Meniere's disease. This notion is confirmed by the present findings showing a high rate (58%) of positive glycerol tests in the selected patients. The importance of DPOAE testing is supported by their ability to detect minimal dysfunction, possibly representing endolymphatic hydrops that goes undetected by routine pure-tone audiometry.     

Distortion-product otoacoustic emissions in neonates: normative data.

Distortion-product otoacoustic emissions (DPOEs) are otoacoustic emissions evoked by two pure tones and used in order to provide a frequency specific assessment of the mechanical properties of the cochlea. This paper first reports complete input-output DPOE functions for audiometric frequencies between 867 Hertz and 8 kHz in a normal neonate population (normative data). DPOE results were analyzed as a function of evoked otoacoustic emission (EOE) properties. Neonates having normal EOEs have large DPOEs. DPOE amplitudes in neonates are larger than in adults. Neonates with atypical EOE frequency spectrum without low frequency components had normal DPOE input-output functions only for high frequencies (above 2 kHz). DPOEs could be useful, in association with EOEs, to precisely evaluate the auditory peripheral function in neonates.     

Distortion-product otoacoustic emissions. Values for clinical use.

Distortion-product otoacoustic emissions are otoacoustic emissions evoked by two pure tones. They are proposed as a frequency-specific test of the mechanical properties of the cochlea. The aim of this study was to measure distortion-product otoacoustic emissions in a clinical setting to establish the most interesting values suitable for clinical use and the clinical interest of the method. The statistical analysis of the data points out some clinically interesting values: (1) a screening limit value of 30 dB hearing level and when measuring distortion-product otoacoustic emissions in response to 52 dB sound pressure level for studying active frequency selective mechanisms; (2) a screening limit value of 50 dB hearing level and when measuring distortion-product otoacoustic emissions in response to 72 dB sound pressure level for studying passive cochlear mechanisms; and (3) the slope of the input-output function. All physiologic properties of the cochlea fit with these basic distortion-product otoacoustic emission properties. These criteria can be used whatever the population studied and the material used for distortion-product otoacoustic emissions recordings. Distortion-product otoacoustic emissions can be used as a screening test to separate (1) subjects with normal hearing and subjects with a hearing threshold above 30 dB hearing level (distortion-product otoacoustic emissions in response to a 52 dB sound pressure level "primaries" [ie, pure tones] stimulation intensity), and (2) patients with a hearing threshold above or below 50 dB hearing level (distortion-product otoacoustic emissions in response to a 72 dB sound pressure level primary stimulation intensity). Distortion-product otoacoustic emissions cannot be used as a more precise audiometric test.     

Distortion-product and click-evoked otoacoustic emissions of normally-hearing adults.

The purpose of this study was to compare distortion-product otoacoustic emissions (DPOEs) and click-evoked otoacoustic emissions (CEOEs) for normally-hearing human adults. The statistical analysis consisted of computing the DPOE and CEOE levels versus frequency corresponding to the 10th, 25th, 50th, 75th, and 90th percentiles among normal adult ears. The mean and standard deviations of the DPOEs and CEOEs were computed. A direct comparison of the DPOE and CEOE data obtained from the same ears showed that, in a 1-4 kHz frequency region, there was a statistically significant correlation between the levels of the two types of otoacoustic emissions. This finding supports the hypothesis that DPOEs and CEOEs arise from some common mechanisms of the cochlea such as active nonlinear biomechanical mechanisms of the outer hair cells.     

Distortion-product otoacoustic emissions in humans with high frequency sensorineural hearing loss

Distortion-product otoacoustic emissions (DPOAEs) and pure-tone behavioral thresholds were compared in 20 ears with normal hearing and in 20 ears with high-frequency sensorineural hearing loss. The purpose was to determine if DPOAE amplitude is associated with pure-tone behavioral threshold. Comparison of results from the two groups of ears indicated that DPOAEs were reduced in amplitude or were absent in ears with high-frequency hearing loss. The differences occurred at frequencies above 1,500 Hz. Comparing results from 750 to 8,000 Hz within the same ear revealed a frequency-related correspondence of elevated behavioral threshold to reduced DPOAE amplitude. When behavioral thresholds were better than 20 dB HL, DPOAE amplitude was within the range (+/- 2 SDs) determined for the ears with normal hearing. When pure-tone threshold was greater than 50 dB HL, DPOAEs were absent or were significantly attenuated in 16/17 subjects (94%). The association of emission level with behavioral threshold level was variable when threshold was between these two extremes. Results imply that the measurement of DPOAEs has clinical potential as a means of detecting hearing loss by frequency.     

Distortion-product otoacoustic emissions in the common marmoset (Callithrix jacchus): parameter optimization

Distortion-product otoacoustic emissions (DPOAEs) were measured in a New World primate, the common marmoset (Callithrix jacchus). We determined the optimal primary-tone frequency ratio (f(2)/f(1)) to generate DPOAEs of maximal amplitude between 3 and 24kHz. The optimal f(2)/f(1), determined by varying f(2)/f(1) from 1.02 to 1.40 using equilevel primary tones, decreased with increasing f(2) frequency between 3 and 17kHz, and increased at 24kHz. The optimal f(2)/f(1) ratio increased with increasing primary-tone levels from 50 to 74dB SPL. When all stimulus parameters were considered, the mean optimal f(2)/f(1) was 1.224-1.226. Additionally, we determined the effect of reducing L(2) below L(1). Decreasing L(2) below L(1) by 0, 5, and 10dB (f(2)/f(1)=1.21) minimally affected DPOAE strength. DPOAE levels were stronger in females than males and stronger in the right ear than the left, just as in humans. This study is the first to measure OAEs in the marmoset, and the results indicate that the effect of varying the frequency ratio and primary-tone level difference on marmoset DPOAEs is similar to the reported effects in humans and Old World primates.     

Frequency-specific information from click evoked otoacoustic emissions in noise-induced hearing loss.

Click evoked otoacoustic emissions (CEOAEs), pure-tone audiograms (PTAs), and Bekesy sweep frequency audiograms were recorded from 15 ears of 11 subjects with noise-induced hearing loss. For all ears, hearing threshold levels > or = 30 dB HL were found at the high frequencies. The aims of the study were to examine whether the decomposition of CEOAEs into narrow band components could identify hearing loss in a frequency-specific manner and to what extent audiometric thresholds could be predicted. CEOAEs were parcelled into 0.5-kHz-wide components by means of the wavelet transform. Reproducibility of CEOAE components was compared with audiometric threshold at corresponding frequencies. A general trend of low reproducibility for increasing audiometric thresholds was found. A reproducibility value of 60 per cent was found to best separate normal and elevated thresholds. The presence of a CEOAE component at a given frequency was always associated with audiometric thresholds < or = 20-25 dB HL. On the other hand, the absence of a component was equally associated either with normal or abnormal hearing levels. Large inter-subject variability was observed. A weak linear relationship was found between reproducibility and audiometric thresholds at corresponding frequencies, indicating that analysis of narrow band CEOAE components is valuable for separating normal from hearing-impaired ears but cannot replace the audiogram.     

瞬态诱发耳声发射检测职业性听力损伤的可行性研究

目的 :探讨瞬态诱发耳声发射 (TEOAE)检测职业性听力损伤的可行性及临床应用价值。方法 :选择 90例 (180耳 )噪声暴露工人为实验总组 ,按噪声暴露时间长短又分为 1、2、3组 ;另选 11例 (2 2耳 )正常听力青年人作为对照组 ,行纯音听阈和TEOAE测试。结果 :各实验组纯音听阈值明显高于对照组 ,TEOAE总重复率、幅值和信噪比及各频段重复率、幅值和信噪比明显低于对照组 (P <0 .0 5或P <0 .0 1)。实验 1、2、3组间比较 ,随着噪声接触时间的增加 ,各频率点纯音听阈提高 ,TEOAE总重复率、幅值和信噪比及各频段重复率、幅值和信噪比变小 ,在 2 .5 0～ 3.5 0kHz和 3.5 0～ 4 .5 0kHz频段最明显。结论 :用TEOAE检测职业性听力损伤是可行的 ,有临床应用价值 ,最敏感频段为 2 .5 0～ 3.5 0kHz和 3.5 0～ 4 .5 0kHz频段。     

畸变产物耳声发射与瞬态诱发耳声发射的相关性观察

目的：探讨畸变产物耳声发射（DPOAE)和瞬态诱发耳声发射(TEOAE)的特点和相关性。方法：以20例（40耳）耳科正常青年人观察噪声暴露前后在无对侧抑制（NCS)状态下和有对侧抑制（CS)状态下TEOAE的频带信噪比、频带反应幅值，与DPOAE的2f1-f2幅值、信噪比相互间的相关性。结果：DPOAE与TEOAE虽由不同的刺激声所引出，有各自的图形特征，但在绝大多数相近频率点上，其测量值有较好的相关性，形成一定的数量关系。结论：TEOAE测试较为快捷并有中频优势，而DPOAE则有很好的频率特异性和高频优势。二者幅值及信噪比间有良好的相关性，可得出有统计意义的线性回归方程参数，听觉损害，噪声性。     

Temporary and permanent noise-induced changes in distortion product otoacoustic emissions in CBA/CaJ mice

A number of studies have shown that the ear can be protected from sound over-exposure, either by activating the cochlear efferent system, or by sound 'conditioning' in which the role of the efferent system is less certain. To study more definitively the molecular basis of deliberately induced cochlear protection from excessive sounds, it is advantageous to determine, for an inbred mouse strain, a range of noise exposure parameters that effectively alter cochlear function. As an initial step towards this goal, young CBA/CaJ mice were exposed to a 105-dB SPL octave-band noise (OBN), centered at 10 kHz, for various lengths of time consisting of 10 min, or 0.5, 1, 3, or 6 h. Distortion product otoacoustic emissions (DPOAEs) at the 2f1-f2 frequency, in response to equilevel primary tones of low to moderate levels, were used to quantify the damaging effects of these sound over-exposures on cochlear function. In addition, staining for acetylcholinesterase (AChE) activity to assess for noise-induced changes in the pattern of efferent-nerve innervation to the cochlea was also performed in a subset of mice that were exposed to the longest-lasting 6-h OBN. The 10-min OBN resulted in only temporary reductions in DPOAE levels, which recovered to pre-exposure values within 5 days. Increasing the exposure to 0.5 h resulted in permanent DPOAE losses that, for low primary-tone levels, were still present at 31 days post-exposure. Additionally, the 1-h and longer exposures caused permanent reductions in DPOAEs for all test levels, which were measurable at 31 days following exposure. Light-microscopic observations restricted to the 11-18-kHz frequency region of the organ of Corti, for a subset of mice exposed to the 6-h OBN, uncovered a significant loss of outer hair cells (OHCs). However, despite the OHC loss in this region, the AChE activity associated with the related pattern of efferent innervation remained largely intact.     

The effect of various durations of noise exposure on auditory brainstem response, distortion product otoacoustic emissions and transient evoked otoacoustic emissions in rats

This study was designed to investigate the effect of various durations of noise exposure in animals on physiological responses from the cochlea which are also used clinically in humans: auditory brainstem response (ABR), transient evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs). Rats were exposed to 113 dB SPL broad-band noise (12 h on/12 h off) for durations of 3, 6, 9, 12, 15 and 21 days, and tested 24 h after cessation of the noise and again after a period of 6 weeks. ABR threshold to click stimuli and to a 2-kHz tone burst (TB), TEOAE energy content and DPOAE amplitude in the exposed rats were compared to those in a group of control rats not exposed to noise. ABR thresholds (click and TB) were significantly elevated in all exposure duration groups compared to control rats. DPOAE amplitudes and TEOAE energy content were significantly reduced. The mean ABR thresholds following 21 days exposure were significantly greater (click = 100 dB pe SPL; TB = 115 dB pe SPL) than those following 3 days exposure (click = 86 dB pe SPL; TB = 91 dB pe SPL). Linear regression analysis between recorded responses and duration of noise exposure (days) showed a significant increase in ABR thresholds of approximately 0.8-- 1.4 dB/day. TEOAE and DPOAE responses showed no such dependence on noise duration and were already maximally reduced after only 3 days of exposure. This can be explained by the possibility that short noise exposures may cause damage to the early, more active stages of cochlear transduction (as shown by TEOAEs and DPOAEs). As the noise exposure continues, further damage may be induced at additional, later stages of the cochlear transduction cascade (as shown by ABR). Thus, ABR seems more sensitive to noise duration than OAE measures.     

Isoflurane anesthesia suppresses distortion product otoacoustic emissions in rats

A commonly used anesthetic, isoflurane, can impair auditory function in a dose-dependent manner. However, in rats, isoflurane-induced auditory impairments have only been assessed with auditory brainstem responses; a measure which is unable to distinguish if changes originate from the central or peripheral auditory system. Studies performed in other species, such as mice and guinea-pigs, suggests auditory impairment stems from disrupted OHC amplification. Despite the wide use of the rat in auditory research, these observations have yet to be replicated in the rat animal model. This study used distortion product otoacoustic emissions to assess outer hair cell function in rats that were anesthetized with either isoflurane or a ketamine/xylazine cocktail for approximately 45?min. Results indicate that isoflurane can significantly reduce DPOAE amplitudes compared to ketamine/xylazine, and that responses were more variable with isoflurane than ketamine/xylazine over the 45-min test period. Based on these observations, isoflurane should be used with caution when assessing peripheral auditory function to avoid potentially confounding effects.     

Distortion-product otoacoustic emission: early detection in deferoxamine induced ototoxicity

OBJECTIVE: Deferoxamine therapy in lifelong transfusion-dependent anaemias, as beta-thalassemia major, is associated with an increased risk of ototoxic changes. With increasing survival rates, prevention and/or early detection of ototoxicity are important for providing management options. The predictive value of pure-tone audiometry in early detection of ototoxicity has been questioned, particularly in the higher frequencies. Otoacoustic emissions appear to be more sensitive to cochlear insult than the conventional pure-tone audiometry. The aim of our study was to compare the efficacy of otoacoustic emissions (distortion-product otoacoustic emissions) with that of pure-tone audiometry as method of audiological monitoring. METHODS: Baseline audiometric (0.25-8kHz) and otoacoustic emission testing (distortion-product otoacoustic emissions) was conducted in a group of patients with beta-thalassemia major, 60 of whom met the criteria for inclusion in the study. Comparisons were performed between baseline measurements and those recorded after 20 months. Distortion-product otoacoustic emissions were obtained as DP-grams. The DP-gram amplitude was determined for each child. RESULTS: Threshold changes from baseline were found to be statistically significant from 4 to 8kHz in 68.4% of the subjects (P<0.01). Distortion-product otoacoustic emissions demonstrated a significant threshold shift and a decreased amplitude in the frequencies >3kHz (P<0.05). Furthermore, DP-gram amplitude also reduced significantly at 3kHz (P<0.05) without any similar change in pure-tone audiometry. CONCLUSIONS: As ototoxicity screening tool DP-gram was extremely sensitive and superior to pure-tone audiometry. Their use is recommended for regular monitoring of cochlear function, aiming in prevention of permanent damage.     

畸变产物耳声发射的临床研究

畸变产物耳声发射（distortionProductotoacousticemissions，DPOAEs）为由两个纯音（F_1，F_2）同时刺激诱发的、由耳蜗外毛细胞能动活动产生的、在外耳道记录到的一种声能。与其它耳声发射相比其用于临床有以下优点：①潜伏期短；②可以连续评价任何频率，尤其是1～8kHz频率范围耳蜗功能；③可以完全评价刺激阈或刺激阈上水平的耳蜗功能（输入／输出功能曲线）；④听阈高达45～55dBHL，患者可以检测出，而瞬态诱发耳声发射（TEOAES）当听阈大于30dBHL时则测不出’‘’。所以DPOAES越来越多地受到人们的重视。巨DPOAES用于临…     

新生儿自发性耳声发射与瞬态诱发性耳声发射的相关性

目的分析自发性耳声发射（spontaneous otoacoustic emission,SOAE）与瞬态诱发性耳声发射（transient evoked otoacoustic emission,TEOAE）之间的相关性。方法新生儿112例（224耳）,其中女59例,男53例,出生后2～4天内行SOAE及TEOAE检测。结果每耳SOAE信号峰数量与其TEOAE强度相关（r=0.43,P〈0.001）。每耳最大SOAE波幅与其TEOAE强度相关（r=0.49,P〈0.001）。不同耳依据其SOAE信号峰数量将其分为4组：I组无SOAE信号峰;II组为单SOAE信号峰;III组为2～3个SOAE信号峰;IV组为3个以上信号峰。I组TEOAE强度为（10.96±3.77）dBSPL,II组（12.87±3.27）dBSPL,III组（15.61±3.23）dBSPL,IV组（17.100±4.51）dBSPL,各组间的TEOAE强度差异均具有统计学意义。II组SOAE最大强度（-13.54±9.21）dBSPL,III组（-4.56±7.22）dBSPL,IV组（1.00±7.35）dBSPL,各组间最大SOAE波幅差异具有统计学意义。结论SOAE信号峰数量、最大SOAE波幅与TEOAE强度之间存在正相关关系,SOAE信号峰越多,最大SOAE波幅也越强,同时TEOAE强度也越强。     

听神经瘤的耳声发射观察

目的 观察和分析听神经瘤的耳声发射特点,为评估听神经瘤患者的耳蜗功能和选择保护听力的术式提供参考依据.方法 对20例（22耳）听神经瘤患者行纯音听阈、阻抗、听性脑干反应（auditory brainstem response,ABR）、诱发性耳声发射（evoked otoacoustic emissions,EOAE）测试及CT和（或）MRI扫描,能引出EOAE的瘤耳检测其自发性耳声发射（spontaneous otoacoustic emissions,SOAE）和传出抑制功能.结果 28.57%听神经瘤耳能引出EOAE,按其畸变产物耳声发射（distortion product otoacoustic emissions,DPOAE）特点分为三型：①“耳蜗型”3耳;②“非耳蜗型”2耳;③“混合型”1耳;“非耳蜗型”耳能引出强大的SOAE;能引出EOAE的6耳均有内侧橄榄耳蜗传出系统功能障碍.结论 EOAE可精确分析听神经瘤患者的耳蜗（外毛细胞）功能,部分听神经瘤病人存在“离断耳”现象.耳声发射（otoacousticemissions,OAE）在诊断重度感音神经性聋（包括听神经瘤病人）方面有一定潜能.