Evaluation of glycerol test in Meniere's disease with pure tone audiometry and distortion product otoacoustic emission

The purpose of the work was to follow up changes in the pure tone audiometry and distortion products otoacoustic emissions (DPOAE) after glycerol administration in Meniere's patients. Twenty patients with Meniere's disease and 16 with cochlear hearing loss without vestibular symptoms were subjected to the glycerol test following the complete audiological evaluation. Glycerol was administered orally 1.5 ml/kg of body weight dissolved in the equal amount of the physiological saline. The results of the glycerol test were analyzed with reference to changes in the pure tone threshold and DPOAE testing. Both investigations were performed in four series: as an initial testing before the glycerol intake and next--one, two and three hours after the glycerol administration. DPOAE included DP-gram registration (L1 = L2 = 70 dB; f2/f1 = 1.22; 1/2 octave) and input/output (I/O) function at 2, 4 and 6 kHz. The glycerol test was regarded as positive in the audiometry if the pure tone threshold improved at least 15 dB at minimum 3 frequencies. Positive result of the glycerol test in DPOAE was judged if DP amplitude increased more than 5dB at 2 or more frequencies in DP-gram and/or DP-threshold lowered at least 10dB in minimum two I/O registrations. In the subjects with Meniere's disease, 11 positive and 9 negative glycerol tests in audiometry and 10 positive and 10 negative DPOAE glycerol tests were obtained. In the reference group, one audiometric glycerol test and two DPOAE glycerol tests were regarded as positive. Much conformity, making 85%, between audiometric and DPOAE tests results is observed. The dynamics of the parameter changing in the consecutive test hours was also similar in both pure tone audiometry and DPOAE. These studies suggest that distortion product otoacoustic emission could be useful in diagnostics of Meniere's disease and would be a valuable diagnostic tool as an objective examination.     

The 2f1-f2 DPOAE amplitudes and latencies in the groups of older people with presbyacusis and young people with normal hearing

Otoacoustic emissions have been shown to be useful as indicators of the cochlear function. One of the most valuable techniques is distortion product otoacoustic emission recording (DPOAE), mostly 2f1-f2 distortion, which is described as being present regularly and indicating the strongest connection with hearing level. DPOAE amplitudes are analysed as relating to the frequency (DP-gram) or to the signal levels (input-output function). Another feature of DPOAE providing many details with regard to cochlear mechanics seems to be the assessment of 2f1-f2 DPOAE latencies. In the present study 2f1-f2 DPOAE amplitudes and latencies were analysed and compared in two groups: the elderly with presbyacousis and the young with normal hearing level. All measurements were taken using Otodynamics ILO 92 system. DPOAE latencies were recorded by phase gradient method with fixed-f1 and swept-f2 signal. The following signal parameters were used: f2 ranging from 732 to 6396 Hz, signal levels L1 = L2 = 70 dB SPL, f2/f1 ratio ranging from 1.18 to 1.25. According to the mathematical formula y = 1.412 + exp(7.685-0.7698*ln(f2)) 2f1-f2 DPOAE latencies were calculated in the group of young people at f2 = 1.0 kHz; 2.0 kHz; 3.0 kHz; 4.0 kHz; 5.0 kHz; 6.0 kHz as follows: 12.08 ms; 7.67 ms; 5.99 ms; 5.08 ms; 4.50 ms; 4.10 ms. The analogous analysis revealed the following results in the group of the elderly: y = 2.402 + exp(9.293-1.019*ln(f2)) and calculated latencies--11.9 ms; 7.09 ms; 5.50 ms; 4.71 ms; 4.24 ms; 3.93 ms. The greater differentiation of the latencies measured in low frequency band was observed in the elderly while in the young subjects in mid and high frequency bands. The 2f1-f2 DPOAE amplitudes recorded for the whole frequency band were significantly higher in the young people than in the elderly. No correlation was observed between latencies and amplitudes in both investigated groups.     

DPOAE otoemission in patients with tinnitus and normal hearing

The goal of our study was analysis of characteristic interrogation, audiometry and distortion products otoacoustic emission in patients with normal hearing and complaining of tinnitus. We examined the group of 24 ill patients with hearing threshold up till 25 dB HL and with tinnitus and the control group of 18 with no audiological complains. All the patients were made tonal audiometry and the discomfort level as well as tinnitus frequency and intensity were evaluated. For each ear separately, we examined DPAOE of DP-gram function with resolving power of half the octave and the fine structure on the level of stimulation L1 = L2 = 70 dB. In the group of patients average time of tinnitus was 1.5 year. Average hearing threshold in patients with tinnitus was 18 dB HL for air conduction and 11 dB HL for bone conduction, average discomfort threshold--93 dB HL. In the control group hearing threshold was comparatively 16 dB and 10 dB HL and average discomfort threshold--95 dB HL. In the tinnitus group 8 patients (21%) complained of hyperacusis. The differences between the two groups in DP-gram were observed mainly in high frequencies (higher than 3000 Hz). In DP-gram fine structure in the group of patients with tinnitus we noted wider span of otoemission decreases (over the octave) compared to control group. In the tinnitus group among 20 examined ears with decreases of otoacoustic emission DP--fine structure only in 6 patients (30%) the frequency of tinnitus given by the patient was overlapping with the frequency for which decreases of otoemission were observed. In both groups we observed decreases of DPOAE for some frequencies but in the patients with tinnitus we noticed the lack of otoacoustic emission in wider span of frequencies, mainly in higher frequencies compared to controls.     

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.     

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.     

Influence of ultrahigh-frequency hearing thresholds on distortion-product otoacoustic emission levels at conventional frequencies

This study examined the association between ultrahigh-frequency (UHF) hearing sensitivity and distortion-product otoacoustic emission (DPOAE) levels at conventional frequencies. Behavioral thresholds were measured from 2 through 16 kHz, and DPOAE levels were measured at discrete f2 frequencies between 2 through 8 kHz in 553 young normal-hearing adult male participants. A DPOAE frequency sweep was measured with primary stimulus levels of L1/L2 = 65/55 dB SPL and an f2/f1 of 1.2. Significant negative correlations, although weak, were found between UHF behavioral thresholds and DPOAE levels. As UHF behavioral thresholds worsened, DPOAE levels decreased at all frequencies. When the data were categorized into two groups, "better" and "worse" UHF behavioral thresholds, significant differences were apparent between the two groups for DPOAEs. Additionally, those with better UHF thresholds had better conventional thresholds compared to those in the worse UHF threshold group. The results of this age-restricted, large-sample-size study confirm and augment findings from earlier studies demonstrating that UHF hearing sensitivity has some influence on DPOAE measures at frequencies from 2 through 8 kHz with moderate stimulus levels. However, because those with better UHF thresholds also had better conventional thresholds and the significant correlations found were weak, this work supports the importance of UHF hearing testing in conjunction with otoacoustic emission measures to identify basal cochlear insults not evident from behavioral testing at conventional frequencies.     

Diplacusis,hearing threshold and otoacoustic emissions in an episode of sudden,unilateral cochlear hearing loss

Limited data are available on the relationship between diplacusis and otoacoustic emissions and sudden hearing threshold changes, and the detail of the mechanism underlying diplacusis is not well understood. Data are presented here from an intensively studied single episode of sudden, non-conductive, mild hearing loss with associated binaural diplacusis, probably due to a viral infection. Treatment with steroids was administered for 1 week. This paper examines the relationships between the hearing loss, diplacusis and oto-acoustic emissions during recovery on a day-by-day basis. The hearing thresholds were elevated by up to 20 dB at 4 kHz and upwards, and there was an interaural pitch difference up to 12% at 4 and 8 kHz. There was also a frequency-specific change in transient evoked otoacoustic emission ( TEOAE) and distortion-product otoacoustic emission (DPOAE) level. DPOAE level was reduced by up to 20 dB, with the greatest change seen when a stimulus with a wide stimulus frequency ratio was used. Frequency shifts in the 2f2 – f1 DPOAE fine structure corresponded to changes in the diplacusis. Complete recovery to previous levels was observed for TEOAE, DPOAE and hearing threshold. The diplacusis recovered to within normal limits after 4 weeks. The frequency shift seen in the DPOAE fine structure did not quite resolve, suggesting a very slight permanent change. The timecourses of TEOAE, diplacusis and hearing threshold were significantly different; most notably, the hearing threshold was stable over a period when the diplacusis deteriorated. This suggests that the cochlear mechanisms involved in diplacusis, hearing threshold and OAE may not be identical.     

Normal values for distortion product otoacoustic emissions in children: a study using primary levels previously demonstrated to be optimum for identification of hearing loss.

No published data exist for normal values of distortion product otoacoustic emissions (DPOAE) in children at primary levels f1 = 65 dB and f2 = 55 dB SPL. These primary levels have been previously demonstrated to be optimal for identification of hearing impaired ears in adults. A total of 102 normal children underwent audiological assessment, including exclusion of middle ear disease, pure tone audiometry and DPOAE DP-grams (primaries L1/L2 = 65/55 dB SPL, f1:f2 = 1.22). There was a statistically significant decrease in DPOAE amplitude with increasing age. DPOAE amplitude was also dependent on the frequency of f2. However, there was wide inter- and intra-individual variation in DPOAE amplitude at different frequencies of f2. There was also a large overlap between the range of values of DPOAE amplitude between the adjacent age groups. Detailed assessment of DPOAE in children is feasible in the clinical setting. These normal values should prove invaluable in future studies; however, the large range of normal values means that cross-sectional studies may not be able to detect small variations in cochlear function.     

Diplacusis, hearing threshold and otoacoustic emissions in an episode of sudden, unilateral cochlear hearing loss

Limited data are available on the relationship between diplacusis and otoacoustic emissions and sudden hearing threshold changes, and the detail of the mechanism underlying diplacusis is not well understood. Data are presented here from an intensively studied single episode of sudden, non-conductive, mild hearing loss with associated binaural diplacusis, probably due to a viral infection. Treatment with steroids was administered for 1 week. This paper examines the relationships between the hearing loss, diplacusis and otoacoustic emissions during recovery on a day-by-day basis. The hearing thresholds were elevated by up to 20 dB at 4kHz and upwards, and there was an interaural pitch difference up to 12% at 4 and 8 kHz. There was also a frequency-specific change in transient evoked otoacoustic emission (TEOAE) and distortion-product otoacoustic emission (DPOAE) level. DPOAE level was reduced by up to 20 dB. with the greatest change seen when a stimulus with a wide stimulus frequency ratio was used. Frequency shifts in the 2f2-fi DPOAE fine structure corresponded to changes in the diplacusis. Complete recovery to previous levels was observed for TEOAE, DPOAE and hearing threshold. The diplacusis recovered to within normal limits after 4 weeks. The frequency shift seen in the DPOAE fine structure did not quite resolve, suggesting a very slight permanent change. The time-courses of TEOAE. diplacusis and hearing threshold were significantly different: most notably, the hearing threshold was stable over a period when the diplacusis deteriorated. This suggests that the cochlear mechanisms involved in diplacusis, hearing threshold and OAE may not be identical.     

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.     

Comparison of distortion product otoacoustic emissions in 28 inbred strains of mice

Cochlear function was evaluated in a longitudinal study of 28 inbred strains of mice at 3 and 5 mo of age using measures of distortion product otoacoustic emissions (DPOAEs) in response to a federal initiative to develop rapid mouse phenotyping methodologies. DP-grams at f(2) frequencies ranging from 6.3 to 54.2kHz were obtained in about 3min/ear by eliciting 2f(1)-f(2) DPOAEs in 0.1-octave steps of f(2) with primary tones at L(1)=L(2) =55, 65, and 75dB SPL. CBA/CaJ mice exhibited average levels of approximately 26dB SPL and this strain was selected as the normal reference strain against which the others were compared. Based upon the configurations of their DP-grams, the 28 mouse strains could be categorized into four distinct groups. That is, nine of the strains including the CBA were designated as the CBA-like group because these mice displayed robust DPOAE levels across frequency. In contrast, the remaining three groups all exhibited irregular DP-gram patterns. Specifically, eight of the remaining 19 strains showed a progressive high- to low-frequency reduction in DPOAE levels that was typical of age-related hearing loss (AHL) associated with mouse strains homozygous for the ahl allele and were labeled as AHL-like strains. Seven strains demonstrating relatively even patterns of reduced DPOAE levels across the frequency-test range were designated as Flat-loss strains. Finally, the remaining four strains exhibited no measurable DPOAEs at either 3 or 5 mo of age and thus were classified as Absent strains. Extending the f(2) test frequencies up to approximately 54kHz led to the detection of very early-onset reductions in cochlear function in non-CBA-like groups so that all strains could be categorized by 3 mo of age. Predictably, the AHL-like strains showed more pronounced DPOAE losses at 5 mo than at 3 mo. A similar deterioration in DPOAE levels was not apparent for the Flat-loss strains. Both the AHL-like and Flat-loss strains showed considerably more variability in DPOAE levels than did the CBA-like strains. Together, these findings indicate that DP-grams adequately reveal both frequency-specific loss patterns and details of inbred strain variability.     

Effect of infrasound on cochlear damage from exposure to a 4 kHz octave band of noise

Infrasound (i.e., <20 Hz for humans; <100 Hz for chinchillas) is not audible, but exposure to high-levels of infrasound will produce large movements of cochlear fluids. We speculated that high-level infrasound might bias the basilar membrane and perhaps be able to minimize noise-induced hearing loss. Chinchillas were simultaneously exposed to a 30 Hz tone at 100 dB SPL and a 4 kHz OBN at either 108 dB SPL for 1.75 h or 86 dB SPL for 24h. For each animal, the tympanic membrane (TM) in one ear was perforated ( approximately 1 mm(2)) prior to exposure to attenuate infrasound transmission to that cochlea by about 50 dB SPL. Controls included animals that were exposed to the infrasound only or the 4 kHz OBN only. ABR threshold shifts (TSs) and DPOAE level shifts (LSs) were determined pre- and post-TM-perforation and immediately post-exposure, just before cochlear fixation. The cochleae were dehydrated, embedded in plastic, and dissected into flat preparations of the organ of Corti (OC). Each dissected segment was evaluated for losses of inner hair cells (IHCs) and outer hair cells (OHCs). For each chinchilla, the magnitude and pattern of functional and hair cell losses were compared between their right and left cochleae. The TM perforation produced no ABR TS across frequency but did produce a 10-21 dB DPOAE LS from 0.6 to 2 kHz. The infrasound exposure alone resulted in a 10-20 dB ABR TS at and below 2 kHz, no DPOAE LS and no IHC or OHC losses. Exposure to the 4 kHz OBN alone at 108 dB produced a 10-50 dB ABR TS for 0.5-12 kHz, a 10-60 dB DPOAE LS for 0.6-16 kHz and severe OHC loss in the middle of the first turn. When infrasound was present during exposure to the 4 kHz OBN at 108 dB, the functional losses and OHC losses extended much further toward the apical and basal tips of the OC than in cochleae exposed to the 4 kHz OBN alone. Exposure to only the 4 kHz OBN at 86 dB produces a 10-40 dB ABR TS for 3-12 kHz and 10-30 dB DPOAE LS for 3-8 kHz but little or no OHC loss in the middle of the first turn. No differences were found in the functional and hair-cell losses from exposure to the 4 kHz OBN at 86 dB in the presence or absence of infrasound. We hypothesize that exposure to infrasound and an intense 4 kHz OBN increases cochlear damage because the large fluid movements from infrasound cause more intermixing of cochlear fluids through the damaged reticular lamina. Simultaneous infrasound and a moderate 4 kHz OBN did not increase cochlear damage because the reticular lamina rarely breaks down during this moderate level exposure.     

The hearing function in prematurely born children during the first year of life depending on the duration of gestation estimated by the otoacoustic technique

A total of 239 premature infants of different gestational age remained under the observation throughout the first year of their life for the elucidation of dynamics of the parameters of DP-gram. It was shown that the absence of the distortion-product otoacoustic emission (DPOAE) response during the first months of life of the premature infants was due to immaturity of their cochlear receptor apparatus. The predominant peak was recorded at a frequency of 2 kHz, regardless of the gestational age. The amplitude of DP-gram values in premature infants lay in the low-frequency region (f2=1 kHz) and never reached the high level. The most intensive maturation of the cochlear receptor apparatus is observed during the first 6 months in premature infants of the gestational age below 28 weeks. After the sixth month, the "high-level" response must develop, regardless of the gestational age. By this time, the intensity of maturation of the cochlear receptor apparatus in all age groups of premature infants is virtually identical (p>0.05).     

Influence of Ketamine–Xylazine Anaesthesia on Cubic and Quadratic High-Frequency Distortion-Product Otoacoustic Emissions

Ketamine is a dissociative anaesthetic, analgesic drug as well as an N-methyl-d-aspartate receptor antagonist and has been reported to influence otoacoustic emission amplitudes. In the present study, we assess the effect of ketamine–xylazine on high-frequency distortion-product otoacoustic emissions (DPOAE) in the bat species Carollia perspicillata, which serves as model for sensitive high-frequency hearing. Cubic DPOAE provide information about the nonlinear gain of the cochlear amplifier, whereas quadratic DPOAE are used to assess the symmetry of cochlear amplification and potential efferent influence on the operating state of the cochlear amplifier. During anaesthesia, maximum cubic DPOAE levels can increase by up to 35 dB within a medium stimulus level range from 35 to 60 dB SPL. Close to the -10 dB SPL threshold, at stimulus levels below about 20-30 dB SPL, anaesthesia reduces cubic DPOAE amplitudes and raises cubic DPOAE thresholds. This makes DPOAE growth functions steeper. Additionally, ketamine increases the optimum stimulus frequency ratio which is indicative of a reduction of cochlear tuning sharpness. The effect of ketamine on cubic DPOAE thresholds becomes stronger at higher stimulus frequencies and is highly significant for f2 frequencies above 40 kHz. Quadratic DPOAE levels are increased by up to 25 dB by ketamine at medium stimulus levels. In contrast to cubic DPOAEs, quadratic DPOAE threshold changes are variable and there is no significant loss of sensitivity during anaesthesia. We discuss that ketamine effects could be caused by modulation of middle ear function or a release from ipsilateral efferent modulation that mainly affects the gain of cochlear amplification.     

Impact of infrasound on the human cochlea

Low-frequency tones were reported to modulate the amplitude of distortion product otoacoustic emissions (DPOAEs) indicating periodic changes of the operating point of the cochlear amplifier. The present study investigates potential differences between infrasound and low-frequency sounds in their ability to modulate human DPOAEs. DPOAEs were recorded in 12 normally hearing subjects in the presence of a biasing tone with f(B)=6Hz and a level L(B)=130dB SPL. Primary frequencies were fixed at f(1)=1.6 and f(2)=2.0kHz with fixed levels L(1)=51 and L(2)=30dB SPL. A new measure, the modulation index (MI), was devised to characterise the degree of DPOAE modulation. In subsequent measurements with biasing tones of f(B) = 12, 24 and 50Hz, L(B) was adjusted to maintain the MI as obtained individually at 6Hz. Modulation patterns lagged with increasing f(B). The necessary L(B) decreased by 12dB/octave with increasing f(B) and ran almost parallel to the published infrasound detection threshold. No signs of an abrupt change in transmission into the cochlea were found between infra- and low-frequency sounds. The results show clearly that infrasound enters the inner ear, and can alter cochlear processing.     

Otoacoustic emissions in patients with hypotension

The aim of this study was to investigate the relation between hypotension and slowly developing hearing impairment, using otoacoustic emissions. A group of 42 patients was examined, with diastolic blood pressure < or = 60 mmHg and systolic blood pressure < or = 105 mmHg. The subjects underwent biochemical, cardiological, ENT and audiological examinations. Distortion product otoacoustic emissions (DPOAE) were recorded in the format of DP-gram. The results were compared to the data of 30 normal persons of similar age and sex, examined at the same laboratory. Audiometric results showed that 18 patients had mild or moderate symmetrical hearing loss in one or more frequencies, mainly in the lower frequency range. DPOAE of the patients had reduced amplitude as compared to controls or were even absent, in one or more frequencies. It may be concluded that a hypotensive condition could be a possible factor in the origin of cochlear damage and DPOAE may be useful in monitoring hypotensive patients.     

急性低频感音神经性耳聋的临床观察

目的探讨急性低频感音神经性耳聋(acute low-tone sensorineural hearing loss,ALHL)的临床特点和疗效,提高对该疾病的诊断和认识。方法回顾性分析62例ALHL患者的临床表现、听力学检查和治疗情况,总结其临床发展规律。结果发病年龄以青中年为主,女性明显多于男性,多为单耳发病,表现为耳闷或伴耳鸣,听力下降,不伴眩晕,所有患者纯音听阈均表现为轻中度低频感音神经性耳聋,治疗前后分别为(38.71±6.82)dB和(20.56±9.44)dB,两者比较差异具有统计学意义(P<0.05)。鼓室图"A"型,49例(80.9%)镫骨肌反射引出,40例(64.5%)Metz试验阳性,62例ABR均正常。62例患者治疗前DPOAE在0.5～1 kHz的引出率仅为18.7%,反应幅值明显降低,治疗后DPOAE在0.5～1 kHz的引出率提高至43.8%,幅值亦有所提高。结论 ALHL以突发的耳闷和(或)伴耳鸣为主要表现,常单耳发病,青中年女性为主,听力学定位诊断为蜗性聋,仅累及低频区,皮质类固醇激素治疗有较好的疗效。     

Intra- and intersubject variability of acoustically evoked otoacoustic emissions. II. Distortion product otoacoustic emissions]

BACKGROUND: Distortion product otoacoustic emissions (DPOAEs) are evoked by simultaneously stimulating the cochlea with two tones. The DPOAE with the highest amplitude (at the frequency 2f1-f2) is usually used for routine audiological evaluation. Any interpretation of DPOAEs in a clinical setting must consider their intra- and intersubject variability. METHODS: DPOAE measurements were performed in 36 normally hearing adults in three weekly test sessions. Each ear was tested twice per session, and the results were statistically analyzed. RESULTS: All test candidates had measurable DPOAEs. Statistically significant differences in absolute DPOAE amplitudes were neither found between two measurements at the same day, nor at weekly intervals, nor between right and left ear of the same candidate. Absolute DPOAE amplitudes in women were significantly higher in the 2-6 kHz range whereas they presented with significantly lower amplitudes below 2 kHz when compared to men. CONCLUSIONS: The present results indicate that monitoring of the inner ear status can be reliably performed using DPOAE measurements. Change in DPOAE amplitudes effectively indicate changes in the cochlear function with high sensitivity. Compared to TEOAE measurements, DPOAEs offer a higher frequency resolution in a broader frequency band and thus more detailed information about the cochlear condition.     

听神经病的听功能状态分析

目的 :探讨听神经病的听功能状态及病损部位。方法 :分析 6 5例听神经病患者的临床资料、纯音测听、声导抗测试、听性脑干反应 (ABR)、4 0Hz听觉相关电位及OAE检查结果。结果 :听神经病的低频听力损失源于蜗后的传入、传出神经及听性脑干受损 ,表现为声反射、传出抑制、ABR异常及诱发性OAE与纯音听阈不呈平行关系 ,与之相对应 ,低频区的外毛细胞处于失抑制的超常活动状态 ,表现为低频区SOAE增强、TEOAE反应幅值及DPOAE幅值升高 ;听神经病的高频听力损失源于耳蜗的外毛细胞损害 ,表现为高频区DPOAE幅值与纯音听阈呈一致性下降 ;听神经病的中频听力损失最轻或接近正常 ,表现为 2kHz附近的纯音听阈和DPOAE幅值均接近于正常。结论 :听神经病的传入、传出系统及耳蜗水平均有不同程度的功能障碍 ,其病损部位主要在耳蜗传入、传出神经 ,向上可侵及脑干 ,向下可侵及耳蜗     

Changes in 2f1 - f2 acoustic distortion products in humans during quinine-induced cochlear dysfunction

Quinine is a suitable model substance for the study of otoacoustic emissions (OAEs) as it reversibly affects the outer hair cells, thus reducing sensitivity, frequency-selectivity and various forms of OAEs. The aim of this experiment was to study quinine-induced changes in the input/output (I/O) function of 2f1 - f2 distortion product OAE (DPOAE; f2/f1 = 1.22; 750-6,000 Hz). Six volunteers with normal hearing (26-39 years old) were intravenously infused to achieve pseudostable quinine plasma concentrations (approximately12 microM) inducing an average pure-tone threshold (PTT; 750-6,000 Hz) shift of 18 dB (5-30 dB) (frequency-independent and reversible). The mean quinine-induced DPOAE shift increased continuously with decreasing equal-level primary tones, e.g. from 1.0 dB at 70 dB sound pressure level (SPL) (n = 42) to 10.5 dB (n = 22) at 40 dB SPL (pooled data, no frequency dependence). According to recruitment, the mean slope of the DPOAE I/O function (at 30-60 dB SPL) increased from 0.86 to 1.35 dB/dB. The lack of correlation between shifts in DPOAE and PTT is in stark contrast to the excellent correlation reported between shifts in transient evoked OAE detection threshold and its corresponding psychoacoustic threshold. The highly vulnerable spontaneous OAEs, in combination with the less vulnerable DPOAEs, fit into a recently proposed taxonomic classification for OAEs.