Rapid adaptation of the 2f1-f2 DPOAE in humans: binaural and contralateral stimulation effects

The present data were collected in humans to characterize the effects of monaural and binaural stimulation and contralateral noise on the 2f1-f2 distortion-product otoacoustic emission (DPOAE) adaptation response. DPOAE levels (f2/f1=1.21, L1=70 dB SPL, L2=65 dB SPL) were measured in both ears for a range of f2 frequencies (1.2 to 10.0 kHz). The f2 frequency producing the largest amplitude DPOAE was used for further testing employing three different stimulus conditions: the primary tones were presented to only one ear for 4 s; the two tones were presented simultaneously in both ears; and, contralateral broadband noise (60 dB SPL) was presented for 5 s, beginning 4 s after the onset of the monaural primaries in the test ear. Acoustic reflex thresholds were measured to verify that the middle-ear muscles played no systematic role in the measured DPOAE reductions. Estimates of monaural rapid adaptation levels and time constants agreed well with previous human findings. The magnitude of the rapid adaptation under binaural stimulation, as compared with monaural primaries, was 25% greater on average, though adaptation time constants were comparable. With added contralateral noise, the average DPOAE suppression was 1.1 dB (0.3-2.7 dB). The magnitude of the monaural adaptation and the effects of binaural and contralateral stimulation, however, were smaller than those measured previously in experimental animals, though the time constants were in good agreement.     

Fine structure of distortion product otoacoustic emissions: its dependence on age and hearing threshold and clinical implications

Distortion product otoacoustic emissions (DPOAE) are routinely used in audiological diagnostics. When the stimulus frequencies f1 and f2 are varied in small steps, distinct non-monotonicities (peaks and valleys) in DPOAE level versus frequency functions can be observed. This so-called DPOAE fine structure (FS) is supposed to be the result of physiological interferences between two different cochlear sources which generate the DPOAE signal. Although FS can complicate interpretations with respect to cochlear functional status at the primary source near f2, its presence might also be relevant in clinical audiological diagnostics. It is therefore of interest to determine FS prevalence and its dependence on age, frequency and hearing threshold. First, it was screened for FS using two tone stimulation (L1/L2 = 55/45 dB SPL, f2/f1 = 1.22) and frequency steps of 40 Hz in the frequency range of 1.8-4.2 kHz. DPOAE (2f1 - f2) were then recorded in 1/3 octave-bands centered around f2 = 2, 3 and 4 kHz with a frequency resolution of 12.5, 20 and 25 Hz, respectively, both with and without a third stimulus (L3 = 45 dB SPL, f3 = 2f1 - f2 + 25 Hz) which was supposed to act as a suppressor of FS. Results of measurements in 102 human individuals from a mixed patient population are reported. Prevalence of DPOAE and FS in a specific frequency range, (i.e. 2, 3, or 4 kHz) was classified into five categories: I) distinct FS within the respective frequency range, II) "single dip" in DP-gram, III) "flat" DP-gram well above noise floor but no distinct FS, IV) DPOAE near noise floor with "irregular responses", and V) no DPOAE measurable. The prevalence of the categories was set in relation to the subject's age and the audiometric threshold at the corresponding center frequency. The estimated probability for a FS (category I and II) was 50-80% if hearing threshold was better than 10 dB HL at the corresponding center frequency. FS prevalence strongly decreased with increasing hearing loss (P < 0.0001). There was no statistically significant age effect (P = 0.088). In more than 50% of the subjects with a behavioral hearing threshold of 10 dB HL or better, a distinct FS near the according frequency was detected, given the presented measurement conditions. While further research is directed at optimal suppression of the second cochlear source of DPOAE and thereby of FS in order to obtain information about the cochlear status near f2 only, the evaluation of FS itself may be clinically useful for monitoring subtle cochlear changes, e.g. during exposure to ototoxic substances or noise.     

Clinical relevance of distortion product emissions by means of receiver operating characteristic (ROC) analysis.

The clinical use of distortion product otoacoustic emissions (DPOAE) stems from the observation that the outer hair cells are the most vulnerable part of the cochlea, and damage to these cells is associated with hearing loss and loss of DPOAE. The purpose of this study is to evaluate the applicability of DPOAE in predicting hearing thresholds under clinical conditions. DPOAE measurements (L1 = L2 = 70 dB SPL. f2/f1 = 1.20) of 219 hearing-impaired and normal hearing ears were analyzed. Recordings were acquired for DPOAE at 2 f1-f2 varying from 635 to 4052 Hz. The detectability of DPOAE in hearing-impaired subjects exhibited a strong hearing threshold dependence. Receiver operating characteristic (ROC) analysis yielded the highest sensitivity and specificity for threshold levels of about 30 dB at low frequencies and for threshold levels of about 60 dB at high frequencies. In addition, the separability of groups with different hearing status was more reliable at high frequencies as compared to low frequencies. The DPOAE provide an objective assessment of cochlear function. However, prognosis of hearing thresholds on the basis of DPOAE measurements depends strongly on the test frequency and is associated with large errors. Hence, the clinical use of DPOAE in predicting hearing thresholds is limited.     

Distortion product otoacoustic emission response characteristics in older adults

OBJECTIVE: The primary purpose of this study was to determine the distortion product otoacoustic emission (DPOAE) and noise response characteristics in a large sample of older adults. Another purpose was to evaluate how specific absolute DPOAE levels or DPOAE/Noise ratios differentiated hearing status in these individuals. DESIGN: A cross-sectional design was utilized for this study. As a part of the Epidemiology of Hearing Loss Study (EHLS), DPOAEs were measured in 937 of the 3,429 participants aged 48 to 92 yr. The DPOAE and noise response characteristics were evaluated at 1,000, 2,000, 4,000, and 8,000 Hz. Absolute DPOAE level and DPOAE/Noise ratios were measured in the participants. The DPOAE data were compared with individual pure-tone frequencies (1,000, 2,000, 4,000, and 8,000 Hz) in the participants to investigate how DPOAE responses differentiated ears with normal hearing from impaired ears. Sensitivity, specificity, positive and negative predictive values, and accuracies were calculated for various absolute DPOAE levels and DPOAE/Noise ratios. RESULTS: Due to the considerable overlap between DPOAE responses and the noise levels at 1,000 Hz, this frequency was not used for any analyses. Sensitivity and specificity were calculated for various DPOAE responses. Sensitivity and specificity varied by frequency for absolute DPOAE levels and DPOAE/Noise ratios. Receiver operator characteristic (ROC) analyses were used to determine which DPOAE responses differentiated normal hearing from hearing loss. The ROC analyses demonstrated that -6 dB SPL at 2,000 Hz, -14 dB SPL at 4,000 Hz, and -22 dB SPL at 8,000 Hz and a +9 dB DPOAE/Noise ratio at each of these frequencies yielded the highest discrimination. CONCLUSIONS: Sensitivity and specificity varied by DPOAE response characteristics and frequency. The decision as to which DPOAE response criterion used should be based on careful consideration of objectives and the possible consequences of misdiagnosis. The results of this study support the use of DPOAEs as a clinical measure for older adults.     

国产C57和BALB／c小鼠年龄相关性听力损失的畸变产物耳声发射检测

目的通过对国产C57和BALB/c近交系小鼠不同日龄时DPOAE的检测,探讨其听力随年龄变化的趋势.方法对不同日龄国产C57和BALB/c近交系小鼠进行DPOAE测试,设定初始音f1、f2(f1/f2=1.22),其强度L1=70dBSPL,L2=65dBSPL,在频率[(f1·     

Evaluating cochlear function and the effects of noise exposure in the B6.CAST+Ahl mouse with distortion product otoacoustic emissions

Cochlear function and susceptibility to noise over-exposure were examined in the congenic mouse strain B6.CAST+Ahl (B6.CAST) and compared to these same features in the CAST/Ei (CAST) and C57BL/6J (C57) parental strains. For both types of comparisons, the primary measure was the distortion-product otoacoustic emissions (DPOAE) at 2f1-2f2. Our assumption was that the B6.CAST mouse was corrected for the early onset age-related hearing loss (AHL) exhibited by one of its parental strains (C57) by the age-resistant properties of its other parental strain (CAST), and thus would exhibit neither AHL nor susceptibility to noise overstimulation effects. With respect to cochlear function, for 2.5-month mice, there was a tendency for DPOAEs to be slightly lower for mid-frequency primary tones for both C57 and B6.CAST mice, while the former mice showed clear AHL effects at the highest test frequency. However, by 5 months of age, the B6.CAST mice, like the CAST mice, displayed robust DPOAE levels that were significantly larger than DPOAE levels for the C57 mice, which were essentially absent for frequencies above about 30 kHz. To investigate the role of the Ahl gene in the susceptibility of the cochlea to the effects of noise over-exposure, two distinct paradigms consisting of temporary (TTS: 1-min, 105-dB SPL, 10-kHz pure tone) and permanent (PTS: 1-h, 105-dB SPL, 10-kHz octave band noise) threshold-shift protocols were used. The brief TTS exposure produced reversible reductions in DPOAEs that for both the B6.CAST and CAST mice recovered to within a few dB of their baseline levels by 3 min post-exposure. In contrast, the C57 mice recovered somewhat slower and, by 5 min post-exposure, emission levels were still 5 dB or more below their corresponding pre-exposure values. At 3 months of age, the TTS mice along with another group of na?ve subjects representing the same three mouse strains were exposed to the PTS paradigm. By 4 days post-exposure, for B6.CAST and CAST mice, DPOAE levels had recovered to their pre-exposure control levels. However, DPOAEs for the C57 mice at most of the measurable frequencies were at least 10-30 dB lower than their counterpart baseline levels. Together these data suggest that the Ahl allele in the C57 strain contributes to both the early onset AHL exhibited by these mice as well as their susceptibility to both TTS and PTS over-exposures.     

Interpreting auditory brainstem evoked responses and distortion product otoacoustic emissions in diabetic patients with normal hearing

ObjectiveHearing impairment is a reported late complication of diabetes mellitus (DM). Previous studies have suggested that microangiopathic complications may cause cochlear nerve function deterioration. We evaluated the auditory brainstem evoked responses (ABRs) and distortion product otoacoustic emission (DPOAE) results according to the presence of DM in subjects with normal hearing.MethodsA cross-sectional comparative study was conducted from January 2016 to January 2018. Auditory function tests including ABR and DPOAE were performed for outpatients complaining of unilateral tinnitus. All of analyses were conducted in ears without tinnitus on contralateral side of tinnitus ears. We included subjects showing hearing thresholds within 25 dB at 0.5, 1k, 2k, and 4k on pure tone audiometry. 45 ears in patients with type 2 diabetes mellitus and 85 ears in non-diabetic patients were finally enrolled in our study.ResultsDiabetic subjects showed significantly more prolonged absolute peak latencies (I, III, V) and inter-peak latencies (I–V, III–V) than non-diabetic subjects. However, there was no significant difference in the inter-peak latency (I–III) between these two groups. Diabetic subjects also showed significantly lower amplitudes at f2 frequencies of 1001, 1200, 1587, 4004, 5042, and 6348 Hz than non-diabetic subjects. Additionally, the prevalence of a DPOAE response, defined as 3 dB above the noise floor, was significantly lower in diabetic subjects than that in non-diabetic subjects.ConclusionDiabetic patients with normal hearing can still have abnormal ABR and DPOAE results due to diabetic neuroangiopathy. ABR and DPOAE assessments can help in detecting subclinical auditory dysfunction, which precedes the manifestation of hearing impairment in diabetic patients.     

Olivocochlear activity and temporary threshold shift-susceptibility in humans

STUDY OBJECTIVES: Animal studies (guinea pig, cat, chinchilla) have shown that activity of the medial olivocochlear efferents can exert noise-protective effects on the cochlea. It is not yet known whether such effects are also existent in humans. Olivocochlear activity can be estimated indirectly by contralateral suppression (CS) of otoacoustic emissions (OAE). MATERIAL AND METHODS: We measured Input/Output functions of distortion products of OAE (DPOAE), with and without contralateral acoustic stimulation by white noise, in 94 normal hearing young male subjects. Seven stimuli with L2 between 20 and 60 dB SPL and L1 = 39 dB + 0.4 L2 ("scissor paradigm") were used at f2 = 2, 3, 4, 5, and 6 kHz. The measurement was repeated 2 weeks later. In 83 subjects of the same group, pure tone audiometry was registered before and 6 minutes after shooting exercises to evaluate individual susceptibility to develop a temporary threshold shift (TTS). RESULTS: Test-retest repeatability of CS was generally good. CS averaged 0.98 dB SPL (SD 1.19 dB, median 0.56 dB). As expected, CS was greatest at low stimulus levels (median 1.06 dB at L2 = 20 dB, as compared with 0.33 dB at L2 = 60 dB). The smallest average CS was found at 4 kHz, and the greatest CS appeared at 2 kHz. A TTS occurred in 7 of 83 (8.5%) subjects. Statistical analysis did not reveal any correlation between the amount of CS and individual TTS susceptibility. CONCLUSIONS AND OUTLOOK: 1) Measurement of CS of DPOAE using an extensive measurement paradigm revealed good test-retest repeatability, confirming the reliability of this audiologic tool. 2) CS of DPOAE does not predict individual susceptibility to mild TTS induced by impulse noise in humans. Possible explanations for the missing association are discussed. Future perspectives include longitudinal studies to further elucidate the association between medial olivocochlear bundle-activity and permanent threshold shift in humans. The goal is to develop a diagnostic tool for the prediction of individual noise vulnerability in humans, thereby preventing noise-induced hearing loss.     

Human efferent adaptation of DPOAEs in the L1,L2 space

The adaptive properties of distortion product otoacoustic emissions (DPOAEs) at 2f(1)-f2 were investigated in 12 ears of normally hearing adults aged 18-30 years using long-lasting 1-s primary-tone on-times. In this manner, DPOAE adaptation at a single f2 of 1.55 kHz (f2/f1=1.21) was evaluated as a function of the levels of the primary tones in a matrix of L1, L2 settings, which varied from 45 to 80 dB SPL, in 5-dB steps. DPOAEs were elicited under both monaural and binaural stimulus-presentation conditions. Adaptation was defined as the difference in DPOAE levels between the initial 92-ms baseline measure using a standard protocol and one obtained during the final 92 ms of the prolonged 1-s primary-tones. These differences were averaged across subjects to create contour plots of mean adaptation in the L1,L2 space. The 2f(1)-f2 DPOAE revealed consistent regions of suppression (-0.5 dB difference) or enhancement (+0.5 dB difference) with respect to baseline measures within the L(1),L(2) matrix for both acoustic-stimulation conditions. Specifically, 2f(1)-f2 DPOAE suppressions of 1-2 dB occurred for both monaural and binaural presentations, typically at level combinations in which L1>L2. In contrast, larger 2f(1)-f2 DPOAE enhancements of 3-4 dB occurred for only the binaural condition, at primary-tone level combinations where L1相似文献   

Adaptation of Distortion Product Otoacoustic Emission in Humans

Previous studies of animals observed a phenomenon of adaptation of distortion product otoacoustic emission (DPOAE) and found that the phenomenon was mediated to a large extent by the medial olivocochlear (MOC) reflex. The present study investigated DPOAE adaptation in humans. The following stimuli were used: f2/f1 = 1.2; f2 = 2, 4, or 5.65 kHz; L2 = 50-65 dB SPL re 20 microPa rms, L1 - L2 = 0-15 dB, where L1 and L2 represent levels of the f1 and f2 tones, respectively; duration of two-tone burst = 5.5 s; interburst gap = 20 or 30 s; number of repetitions = 40 or 64. We analyzed the 2f1 - f2 DPOAE as a function of time using a method of heterodyne envelope detection. The subjects were 20 humans aged from 15 to 54 years (median = 21 years) with normal hearing. We observed that (1) humans exhibited DPOAE adaptation phenomenon; (2) the time course of DPOAE level was characterized by a 2-exponential function; (3) distributions of the fast and slow time constants were well separated with their median values being 69 ms and 1.51 s, respectively; (4) distributions of the magnitudes of the fast and slow adaptation components were largely overlapped with their median values being 0.65 and 0.40 dB, respectively; and (5) the combined magnitude of the adaptation ranged from 0.4 to 3.0 dB with a median of 1.10 dB. To our knowledge, the present study is the first published article to describe adaptation of DPOAE in humans. These results should help advance the basic knowledge of human cochlear mechanics operating under the control of the MOC feedback system and contribute to the development of practical applications such as identifying people at high risk of acoustical injury and a clinical test of the functional status of the MOC system.     

DPOAE level shifts and ABR threshold shifts compared to detailed analysis of histopathological damage from noise

A detailed comparison of 2f(1)-f(2) distortion product otoacoustic emission (DPOAE) level shifts (LS) and auditory brainstem response (ABR) threshold shifts with noise-induced histopathology was conducted in chinchillas. DPOAE levels (i.e., L(1) and L(2)) at f(1) and f(2), respectively, ranged from 55-75 dB sound pressure level (SPL), with f(2)/f(1)=1.23, 6 points/octave, f(2)=0.41-20 kHz, and ABR thresholds at 0.5-20 kHz, 2 points/octave, were determined pre-exposure. The exposure was a 108 dB SPL octave band of noise centered at 4 kHz (1-1.75 h, n=6) or 80-86 dB SPL (24 h, n=5). DPOAE LSs (magnitude pre- minus post-exposure) and ABR threshold shifts (TS) were determined at 0 days and up to 28 days post-exposure. The cochleae were fixed, embedded in plastic and dissected into flat preparations. The length of the organ of Corti (OC) was measured; missing inner (IHC) and outer (OHC) hair cells counted; stereocilia damage rated; and regions of OC and nerve-fiber loss determined. Cytocochleograms were made showing functional loss and structural damage with the LS and TS overlaid. Some unexpected results were obtained. First, the best correlation of LS with histopathology required plotting the DPOAE data at f(1) with respect to the chinchilla-place map. The best correlation of TS was with IHC and nerve-fiber loss. Second, wide regions of up to 10% scattered OHC loss in the apical half of the OC showed little or no LS. Third, with the 108 dB SPL noise, there was 20-40 dB of recovery for DPOAEs at mid-high frequencies (3-10 kHz) in eight of 12 cochleae where there was 70-100% OHC loss in the basal half of the OC. The largest recovery at mid-high frequencies occurred in regions where the OC was entirely missing. Fourth, with the 80-86 dB SPL noise, there was no LS at small focal lesions (100% loss of OHCs over 0.4 mm) when the frequency place of either f(1) or f(2) was within the lesion but not both. There was no correlation of LS with OHC stereocilia loss, fusion or disarray. These results suggest that, after noise exposure, DPOAEs at mid-high frequencies can originate from or be augmented by generators located at someplace other than the frequency place of f(2), possibly the basal 20% of the OC when this region is intact. Also, noise-induced DPOAE LSs seemed to reflect differing mechanisms for temporary and permanent hearing loss.     

Distortion product otoacoustic emission test performance for a priori criteria and for multifrequency audiometric standards.

OBJECTIVES: 1) To describe distortion product otoacoustic emission (DPOAE) test performance when a priori response criteria are applied to a large set of DPOAE data. 2) To describe DPOAE test performance when multifrequency definitions of auditory function are used. 3) To determine DPOAE test performance when a single decision regarding auditory status is made for an ear, based on DPOAE data from several frequencies. 4) To compare univariate and multivariate test performance when multifrequency gold standard definitions and response criteria are applied to DPOAE data. DESIGN: DPOAE and audiometric data were analyzed from 1267 ears of 806 subjects. These data were evaluated for three different frequency combinations (2, 3, 4 kHz; 2, 3, 4, 6 kHz; 1.5, 2, 3, 4, 6 kHz). DPOAE data were collected for each of the f2 frequencies listed above, using primary levels (L1/L2) of 65/55 dB SPL and a primary ratio (f2/f1) of 1.22. Sensitivity and specificity were evaluated for signal to noise ratios (SNRs) of 3, 6, and 9 dB, which are in common clinical use. In addition, test performance was evaluated using clinical decision theory, following the convention we have used in previous reports on otoacoustic emission test performance. Both univariate and multivariate analyses techniques were applied to the data. In addition to evaluating DPOAE test performance for the case when audiometric and f2 frequency were equal, multifrequency gold standards and multifrequency criterion responses were evaluated. Three new gold standards were used to assess test performance: average pure-tone thresholds, extrema thresholds that took into account both the magnitude of the loss and the number of frequencies at which hearing loss existed, and a combination of the two. These new gold standards were applied to each of the three frequency groups described above. RESULTS: As expected, SNR criteria of 3, 6, and 9 dB never resulted in perfect DPOAE test performance. Even the most stringent of these criteria (9 dB SNR) did not result in a sensitivity of 100%. This result suggests that caution should be exercised in the interpretation of DPOAE test results when these a priori criteria are used clinically. Excellent test performance was achieved when auditory status was classified on the basis of the new gold standards and when either SNR or the output of multivariate logistic regressions (LRs) were used as criterion measures. Invariably, the LR resulted in superior test performance compared with what was achieved by the SNR. For SNR criteria of 3, 6, and 9 dB and (by definition) for the LR, specificity, in general, exceeded 80% and often was greater than 90%. Sensitivity, however, depended on the magnitude of hearing loss. Diagnostic errors, when they occurred, were more common for patients with mild hearing losses (21 to 40 dB HL); sensitivity approached 100% once the hearing loss exceeded 40 dB HL. The largest differences between test performance based on SNR or LR occurred for the ears with mild hearing loss, where the LR resulted in more accurate diagnoses. CONCLUSIONS: It should not be assumed that the use of a priori response criteria, such as SNRs of 3, 6, or 9 dB, will identify all ears with hearing loss. Test performance when multifrequency gold standards are used to define an ear as normal or impaired and when data from multiple f2 frequencies are used to make a diagnosis, resulted in excellent test performance, especially when the LR was used. When predicting auditory status with multifrequency gold standards, the LR resulted in relative operating characteristic curve areas of 0.95 or 0.96. An output from the LR can be selected that results in a specificity of 90% or better. When the loss exceeded 40 dB HL, the same output from the LR resulted in test sensitivity of nearly 100%. These were the best test results that were achieved. (ABSTRACT TRUNCATED)     

DPOAE in tinnitus patients with cochlear hearing loss considering hyperacusis and misophonia

The most probable place generating tinnitus in auditory pathway are outer hair cells (OHC) inside cochlea. To asses their activity otoacoustic emission is used. The goal of the investigation was estimation the features of otoemission DPOAE in groups with tinnitus patients with cochlear hearing loss, estimation of diagnostic value of DPOAE parameters for analysis of function of the cochlea in investigated patients emphasizing DPOAE parameters most useful in localizing tinnitus generators and estimation of hypothetic influence of hyperacusis and misophony on parameters of DPOAE in tinnitus patients with cochlear hearing loss. The material of the study were 42 tinnitus patients with cochlear hearing loss. In the control group there were 21 patients without tinnitus with the same type of hearing loss. Then tinnitus patients were divided into three subgroups--with hyperacusis, misophony and without both of them, based on audiologic findings. METHOD: after taking view on tinnitus and physical examination in all the patients pure tone and impedance audiometry, supratreshold tests, ABR and audiometric average and discomfort level were evaluated. Then otoemission DPOAE was measured in three procedures. First the amplitudes of two points per octave were assessed, in second--"fine structure" method-- 16-20 points per octave (f2/f1 = 1.2, L1 = L2 = 70 dB). Third procedure included recording of growth rate function in three series for input tones of value f2 = 2002, 4004, 6006 Hz (f2/f1= 1.22) and levels L1=L2, growing by degrees of 5dB in each series. RESULTS: DPOAE amplitudes in recording of 2 points per octave and fine structure method are very valuable parameters for estimation of cochlear function in tinnitus patients with cochlear hearing loss. Decreasing of DPOAE amplitudes in patients with cochlear hearing loss and tinnitus suggests significant role of OHC pathology, unbalanced by IHC injury in generation of tinnitus in patients with hearing loss of cochlear localization. DPOAE fine structure provides us the additional information about DPOAE amplitude recorded in two points per octave, spreading the amount of frequencies f2, where differences are noticed in comparison of two groups--tinnitus patients and control. Function growth rate cannot be the only parameter in estimation of DPOAE in tinnitus patients with cochlear hearing loss, also including subjects with hyperacusis and misophony. Hyperacusis has important influence on DPOAE amplitude, increases essentially amplitude of DPOAE in the examined group of tinnitus patients.     

Distortion product otoacoustic emissions in human hypercholesterolemia

Epidemiological and experimental studies suggest that hypercholesterolemia promotes the development of sensorineural hearing loss; however, the underlying cellular pathomechanism remains obscure. In the present study, 20 healthy subjects and 20 patients with familial hypercholesterolemia were compared with respect to their hearing function. None of the 40 persons reported any history of hearing disorder. In accordance with this subjective impression, mean hearing thresholds were within the normal, age-dependent ranges in both groups. In contrast, the single-generator distortion product otoacoustic emissions (sgDPOAE) were reduced at and above 4 kHz. Input-output functions of DPOAE could be subdivided into three groups: (i) normal, with unity slope at low intensities and slope less than unity (0.24+/-0.07 dB/dB at higher intensities; (ii) pathologic, described by a single straight line; (iii) ill-defined, with data usually indistinguishable from the background noise level. The ill-defined DPOAE behavior was only found in patients with hypercholesterolemia; namely, for 25% of patients at f(2)=1.5 kHz and for 50% at f(2)=4 kHz. Patients belonging to the pathologic and ill-defined DPOAE groups had significantly (P<0.05) higher total serum cholesterol and LDL-cholesterol levels compared with subjects from the normal DPOAE group. While hearing thresholds of patients with ill-defined growth functions were not statistically different from those of normal subjects, speech scores were significantly reduced in these cases. The data imply that nonlinear mechanical processes in the cochlea are compromised in hypercholesterolemic patients.     

新生儿畸变产物耳声发射测试

用ＧＳＩ６０ＤＰＯＡＥ仪对２０例（４０耳）新生儿进行畸变产物耳声发射（ＤＯＰＡＥ）测试。结果显示，在ｆ１≤１ｋＨｚ时ＤＯＰＡＥ检出率很低，而当ｆ１位于１．４￣４．０ｋＨｚ时，检出率大于９０％；低频率的ＤＯＰＡＥ辐值较低，在ｆ１位于１．４￣４．０ｋＨｚ范围内幅值较高。提示新生儿低频段ＤＰ易受噪声、刺激声强度、受试者的自身代谢活动、中耳功能及中耳对耳蜗反应的传输功能的影响。因此，在用ＤＰ进行新生儿听力     

Prediction of hearing outcomes by distortion product otoacoustic emissions in patients with idiopathic sudden sensorineural hearing loss

Objective

To investigate whether distortion product otoacoustic emissions (DPOAEs) can be a prognostic indicator of hearing outcomes in patients with idiopathic sudden sensorineural hearing loss (ISSNHL).

Methods

Seventy-eight consecutive patients with ISSNHL were enrolled. DPOAEs were measured at the first hospital visit. Two primary pure tones with a frequency ratio (f2/f1) of 1.2 were used at non-equal sound pressure levels (L1/L2 = 80/70 dB SPL). The DPOAE amplitude was measured at the 11 frequencies of 2f1-f2 with f2 varying from 593 to 6031 Hz. All the patients received steroid administration in combination with hyperbaric oxygen (HBO) therapy. Hearing recovery was evaluated by the improvement in hearing compared to the unaffected contralateral ear. Correlations between the hearing improvement rate and five potential prognostic factors (the DPOAE amplitude, patient's age, days from onset to the start of treatment, initial hearing level, and presence of vertigo) were examined by simple and multiple regression analyses.

Results

The net DPOAE amplitude in patients with hearing improvement rate ≥50% was significantly larger than that with hearing improvement rate <50% at f2 frequencies of 3031 and 4812 Hz (unpaired Student's t-test, p < 0.05). A simple regression analysis showed that the hearing improvement rate significantly correlated with the net DPOAE amplitude at f2 frequencies of 3031 and 4812 Hz, but not with that at the other f2 frequencies tested. The correlation coefficients were 0.528 and 0.522 for 3031 and 4812 Hz, respectively, with p values <1 × 10⁻⁶. In a multiple regression analysis, the partial correlation coefficients of the net DPOAE amplitude were 0.308 and 0.246 with p values of 0.008 and 0.036 for 3031 and 4812 Hz, respectively.

Conclusion

The significant correlation between hearing recovery and DPOAEs measured before treatment indicates that DPOAEs are a potentially useful means of predicting hearing prognosis in ISSNHL.     

Susceptibility of DPOAEs to Sound Overexposure in Inbred Mice with AHL

The notion that three inbred strains of mice, i.e., C57BL/6J (C57), BALB/cByJ (BALB), and WB/ReJ (WB), which exhibit differential rates of age-related hearing loss (AHL), may also exhibit differential susceptibility to noise-induced hearing loss was tested by comparing the effects of sound overexposure on these strains. The aftereffects of noise overstimulation on the distortion-product otoacoustic emissions (DPOAEs) of these three strains were compared and contrasted to those for the CBA/CaJ (CBA) strain, which does not show changes in hearing threshold sensitivity up to 15 months of age. Two cohorts of mice, one at 2.5 and the other at 6 months of age, were first exposed to a tonal overstimulation paradigm, were allowed to recover, and then were later re-exposed to an octave band noise (OBN), at 3 or 7 months of age, respectively. The two sound exposure episodes were designed to produce either a temporary (tonal exposure) or permanent (OBN exposure) reduction in the levels of the 2f1 - f2 DPOAE in the WB strain, which exhibited the fastest rate of AHL. Although the tonal paradigm resulted in a temporary decrease in DPOAE levels for all strains at both ages, the 2.5-month BALBs showed the greatest susceptibility to this overexposure, while the 2.5-month WBs exhibited the least effects on DPOAEs. At the older age of 6 months, tonal overexposure produced essentially the same reduction in DPOAE levels for all four strains. In addition, there were no differences noted between CBAs and C57s, at either of the two ages. The OBN paradigm resulted in a permanent decrease in DPOAE levels in all the strains exhibiting early AHL, i.e., the C57, BALB, and WB mice, for frequencies about one-half to an octave higher than the exposure frequency, regardless of age. In contrast, the CBA strain was not significantly affected by the OBN overexposure.     

Detection of hearing loss using 2f2-f1 and 2f1-f2 distortion-product otoacoustic emissions.

Although many distortion-product otoacoustic emissions (DPOAEs) may be measured in the ear canal in response to 2 pure tone stimuli, the majority of clinical studies have focused exclusively on the DPOAE at the frequency 2f1-f2. This study investigated another DPOAE, 2f2-f1, in an attempt to determine the following: (a) the optimal stimulus parameters for its clinical measurement and (b) its utility in differentiating between normal-hearing and hearing-impaired ears at low-to-mid frequencies (相似文献   

Effects of sample size on the noise floor and distortion product otoacoustic emissions

This study investigated the effects of sample size on the noise floor and distortion product otoacoustic emissions (DPOAEs) in 55 normal-hearing subjects as a function of intensity. More specifically, we investigated the effects of sample size (12-400 sweeps) as a function of intensity (L1 = L2 = 35, 45 and 55 dB SPL), firstly, on the identifiability of DPOAEs (2F1-F2), secondly, on the noise floor adjacent to DPOAEs, and thirdly, on the magnitude of DPOAEs centred around geometric means of 531 Hz, 1,000 Hz, 2,000 Hz and 4,000 Hz. Testing was conducted with a commercially available system for measuring DPOAEs (Grason-Stadler, GSI-60). A constant F2:F1 ratio of 1.21 was used. As sample size increased from 12 to 400 sweeps, the noise floors decreased by about 13 dB; this closely corresponds to the expected 15 dB reduction based on the square root rule of noise reduction. The highest noise floors were measured at 531 Hz and the lowest noise floors at 2,000 Hz and 4,000 Hz. Identifiability increased as intensity increased from 35 to 55 dB SPL and as sample size increased from 12 to 400 sweeps for all stimulus conditions. Mean DPOAEs for all frequencies (531-4,000 Hz) appeared to decrease as sample size increased, particularly at stimulus levels of 35 dB and 45 dB SPL. These results may be explained by a reduction in the noise levels within the bandwidth of the DPOAE bin. That is, the DPOAE bin is comprised of the DPOAE plus background noise and these two quantities are not separated within the measured bin. Because the magnitude of bin containing DPOAEs is critically dependent on sample size, clinicians should carefully document this variable when collecting normative data. Similarly, clinicians who compare the magnitude of their DPOAEs to published data should note the sample size employed.     

Test-retest repeatability of distortion product otoacoustic emissions

OBJECTIVES: Distortion product otoacoustic emissions (DPOAE) have become part of routine audiological diagnostics. The large scale of clinical DPOAE applications, such as screening of hearing in infants, objective estimation of hearing status, distinction between cochlear and retrocochlear origin of sensorineural hearing loss, exclusion of psychogenic hearing loss, monitoring of hearing during administration of ototoxic drugs, and others illustrates the significance of this audiological tool. In all diagnostic tests, knowledge about the procedure's test-retest repeatability is of crucial importance, to allow for distinction between measurement deviations and true physiological or pathological changes in monitoring over time. DESIGN: Measurements of DPOAE were performed in triplicate in 80 normally hearing ears of 40 subjects. Both immediate remeasurements with the ear probe left in place [single-fit mode (SF-mode)] and remeasurements after approximately 5 to 10 days [multiple-fit mode (MF-mode)] were included. DPOAE primary tone levels were varied in 5 dB steps from L2 = 60 to 20 dB SPL (L1 = L2 x 0.4 + 39 dB SPL) and within the frequency range f2 = 1 to 6 kHz. Repeatability of DPOAE was evaluated by the standard error of measurement (Sm), reliability (Cronbach alpha), absolute differences between measurements, 95% confidence intervals, and repeatability standard deviations. RESULTS: Sm averaged 0.67 dB over all frequencies and primary tone levels in the SF-mode, and 1.44 dB in the MF-mode, respectively. As expected, test-retest repeatability declined with decreasing primary tone levels; however, repeatability values were still mostly satisfactory with the lower primary tone levels. For the exemplary primary tone level combination of L1/L2 = 63/60 dB SPL, which is close to common clinical paradigms, the difference between two DPOAE measurements under the reported test conditions could be considered statistically significant (p = 0.05) if it exceeded 0.7 to 1.3 dB in the range 1 to 5 kHz and 2.3 dB for 6 kHz in the SF-mode, when compared with 1.8 to 2.7 dB for 1 to 5 kHz and 3.7 dB for 6 kHz in the MF-mode. Signal to noise ratio (SNR) did not seem to have a large influence on repeatability, as long as SNR was within 6 to 35 dB, which covers the range of most clinical DPOAE measurements. CONCLUSIONS: The DPOAE-test-retest study presented here is to our knowledge the first, which combines variation of primary tone levels, assessment of both SF- and MF-modes, and comparison of the two modalities within the same subjects. Although the measurements were conducted under practical conditions resembling the clinical setting, repeatability was generally good. The widely used minimum SNR of 6 dB seems to be a recommendable criterion when considering both practicability and measurement quality under clinical conditions. The current findings underline the suitability of DPOAE as a monitoring tool of cochlear status over time. The data are intended to assist the clinician and the scientist in the correct interpretation of DPOAE level changes in the test-retest situation.