Transitory Evoked Otoacoustic Emissions Research Articles

A long-term follow-up study on otoacoustic emissions testing in paediatric patients with severe malaria in Gabon

BackgroundIn a previous study, severe and cerebral malaria have been connected with acute cochlear malfunction in children, demonstrated by a decrease of transitory evoked otoacoustic emissions (TEOAEs) reproducibility. This study aims to determine whether cochlear malfunction persists for 4 years after recovery from severe malaria in a subset of the previous study’s collective. Follow-up TEOAEs were performed on site (CERMEL, Hôpital Albert Schweitzer, Lambaréné, Gabon) or at the participants’ homes; 33 out of 90 participants included in the initial investigation by Schmutzhard et al. could be retrieved and were re-examined, 31/33 could be included. Of the 57 missing participants, 51 could not be contacted, 1 had moved away, 4 refused to cooperate, and 1 had died.MethodsAs in the initial investigation, participants of this prospective follow-up study were subjected to TEOAE examination on both ears separately. A wave correlation rate of > 60% on both ears was considered a “pass”; if one ear failed to pass, the examination was considered a “fail”. The results were compared to the primary control group. Additionally, a questionnaire has been applied focusing on subsequent malaria infections between the primary inclusion and follow-up and subjective impairment of hearing and/or understanding.ResultsThe cohort’s mean age was 9 years, 14 children were female, 18 male. 31 had been originally admitted with severe, one with cerebral malaria. 83.8% of participants (n = 26) presented with a TEOAE correlation rate of > 60% on both ears (the cut-off for good cochlear function); in the control group, 92.2% (n = 83) had passed TEOAE examination on both ears. Recurrent severe malaria was associated with a worse TEOAE correlation rate. Age at infection and gender had no influence on the outcome.ConclusionsCochlear malfunction seems to be persistent after 4 years in more than 16% of children hospitalized for malaria. In a healthy control group, this proportion was 7.8%. Yet, the severity of the initial TEOAE-decrease did not predict a worse outcome.

Identification of risk factors for hearing impairment in newborns: a hospital based study.

Aim To identify risk factors for hearing impairment presented in neonates born in Cantonal Hospital Zenica (CHZ) and to estimate their influence on outcome of hearing tests in Newborn Hearing Screening (NHS). Methods Retrospective-prospective study was done at the Department of Gynaecology and Maternity. The NHS was performed with transitory evoked otoacoustic emissions (TEOAE) during a six-month period using "Titan" device (Interacoustics, Denmark). The questionnaire was written for the purpose of getting more structured basic information about every newborn and to identify risk factors for hearing impairment. Chi-square test was used to investigate the difference between experimental and control group refer incidence. Results A total of 1217 newborns was screened for hearing impairment of which 259 (21.28%) with one or more known risk factors for hearing impairment. The following risk factors for hearing impairment were identified during the study period: family history of permanent childhood hearing impairment in 42 (3.45%) newborns, prematurity in 39 (3.21%), low APGAR scores in 29 (2.40%), asphyxia in 31 (2.55%), hyperbilirubinemia in 41 (3.37%), admission of ototoxic medication (aminoglycosides) after birth in 155 (12.74%). Conclusion There were many serious risk factors for hearing loss identified in this study. Identification of risk factors for hearing impairment in neonates is necessary because a follow up of the children with risk factors is very important.

Age dependence of otoacoustic emissions: the loss of amplitude is primarily caused by age-related hearing loss and not by aging alone

The amplitude of otoacoustic emissions (OAE) is known to decrease with increasing age, but it is still unclear whether this is due to aging alone or to age-related hearing loss. This study describes the exploration of a large database (5,142 patients from 0.4 to 89.8 years) collected in a routine clinical testing. Reliable pure tone audiograms, transitory evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) recordings were available from 5,424 ears without conductive loss, acute sudden deafness or retrocochlear disorder. From this database, group 1 with behavioral thresholds of 10 dB HL or better at all frequencies from 1 to 4 kHz and group 2 with age-accordant thresholds after ISO 7029 were formed. In both groups, the OAE amplitude decreased with increasing age, but in group 1, the effect was significant only for DPOAE recorded at 3 and 4 kHz. In group 2, the loss of amplitude was steeper and highly significant for TEOAE as well as DPOAE at all frequencies, but most pronounced at high frequencies. These findings support the hypothesis that the reduction of OAE amplitude with increasing age is primarily caused by age-linked hearing loss and not by aging alone.

TEOAE amplitude growth, detectability, and response threshold in linear and nonlinear mode and in different time windows

Transitory evoked otoacoustic emissions (TEOAE) have been recorded in 60 ears of 31 adult volunteers with nearly normal hearing at stimulus levels ranging from 83 dB SPL peak equivalent down to the individual response threshold using linear and nonlinear recording mode. The stimulus level dependence of response incidence and amplitude has been analysed for the integral response and in time windows selecting response components of limited latency ranges. At stimulus levels above 70 dB SPL peak equivalent the TEOAE records received in linear mode are contaminated with stimulus artifacts. At moderate stimulus levels the TEOAE amplitude differs only to a small extent between the two recording modes. At low levels the linear mode turns out to be better suited for signal detection due to its inherent lower noise level. The response threshold, defined as the highest stimulus level yielding a reproducibility of at least 60%, is significantly correlated to hearing threshold. The consideration of time windowed responses yields best results with respect to incidence and threshold of responses in the latency range between 5 and 10 ms, but it does not enhance frequency specificity.

Evaluation of Cochlear Function in Patients with Tinnitus Using Spontaneous and Transitory Evoked Otoacoustic Emissions

The aim of this paper has been to investigate the cochlear function and the basic properties of otoacoustic emissions (OAEs) in patients with tinnitus using Spontaneous Otoacoustic Emissions (SOAEs) and Transitory Evoked Otoacoustic Emissions (TEOAEs). We have analyzed the incidence, amplitude and spectral content of hearing thresholds, SOAEs and TEOAEs in a sample of 44 ears. We have measured incidence, intensity, frequency, number of peaks and amplitude of emission and their variability across frequency range from 500 to 5000 Hz. A correlation was determined between the OAEs results and the results obtained using hearing thresholds. We have not found statistically significant differences at 500, 1000, 2000, 4000 and 8000 Hz frequencies neither at mean hearing thresholds between the sample of ears with tinnitus and the sample of ears without tinnitus. SOAEs were only present in 1 of the 44 ears tested (2.27%) and it was a 17 dB SPL amplitude peak at 2770 Hz frequency. TEOAEs, however, were displayed in some frequency in all the ears. We have compared TEOAEs parameters between the sample of ears with tinnitus and the sample of ears without tinnitus in 500, 1000, 2000, 4000 and 5000 Hz frequencies, and we have only found statistically significant differences at 4000 Hz, p = 0.02. Comparison of TEOAEs parameters between ears with tinnitus and ears without tinnitus in the same patient have only found statistically significant differences at 4000 Hz frequency, p = 0.011. In both cases there were not statistically significant differences at 500, 1000, 2000 and 5000 Hz frequencies nor at mean TEOAEs amplitudes for every group. We have not found significant relations between tinnitus and OAEs registration.

Hörvermögen bei Kindern und Jugendlichen mit Down-Syndrom

There are controversial opinions about the incidence of hearing impairment of children and adolescents with Down's syndrome as an additional cause for obstruction in social and communicative live. Next to congenital diseases of the inner ear, functional limitations can often lead to conductive hearing disorders in patients with Down's syndrome. The hearing ability, otoscopic and audiometric characteristics of 115 patients aged 3.2+/-2.9 years were analysed retrospectively over 42 months. A total of 86 children showed morphologic otoscopic peculiarities: transitory evoked otoacoustic emissions (TEOAE) were often non-reproducible, even in patients with normal hearing abilities(14.1% of cases), and were not evaluable in 32.8% of cases. Half of the patients showed hearing loss, 82% of whom suffered from a conductive hearing loss, 6.9% from a combined, and 8.6% from isolated sensorineural hearing loss. Hearing loss was first diagnosed when the children were 4.6+/-3.4 years old. The frequent occurrence of hearing loss justifies and requires an early and continuous pedaudiological examination. As a common screening examination, TEOAE is limited due to its cost, however, it fulfils its purpose as a means of distinguishing healthy children from those with possible hearing disorders. In most cases, objective and subjective audiometric methods must be combined in order to precisely define the hearing ability.

Field Study to Explore Possible Effects of Styrene on Auditory Function in Exposed Workers

We conducted this study to examine, whether occupational styrene exposures are associated with reduced hearing ability. The auditory function was investigated by pure tone audiometry and registration of transitory evoked otoacoustic emissions (TEOAE) in 32 workers of a fibre-reinforced plastic boat building factory. Sixteen subjects were laminators (mean age: 41 yr (SD: 8)) and therefore regularly exposed to styrene with mean duration of exposure to styrene of 7.5 yr (SD 5.0). The tests were applied to a reference group of 16 workers (mean age: 39 yr (SD: 8)) who were not directly exposed to styrene but had a similar noise exposure. A few and isolated correlations between the parameters of hearing acuity and exposure indices, such as current internal styrene exposures (sum of MA and PGA) and duration of styrene exposure, were statistically significant, but no consistent association was found. The results of this study do not support the assumption of an ototoxic effect of chronic styrene exposure in workers.

On a possible prognostic value of otoacoustic emissions: a study on patients with sudden hearing loss.

Otoacoustic emissions (OAE) and pure tone audiogram (PTA) were examined in 26 ears of 25 patients suffering from sudden hearing loss from the 1st day to up to 505 days following the drop of hearing to test the hypothesis whether the OAEs are capable of delivering predictive information about the recovery process. The patients were selected from 50 candidates according to the following criteria: one or both ears exhibited a systematic and significant recovery of pure tone threshold in at least one frequency, OAEs were detectable and PTA available, a conductive hearing loss was excluded, and the auditory brainstem responses (ABR) yielded no signs of retrocochlear disorders. Transitory evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) were measured under constant stimulus and recording conditions in three to nine sessions. The relation between OAE level and actual pure tone threshold was subject to a regression analysis. The correlation between both parameters is small but significant. Even smaller correlations are observed if the OAE level is related to former hearing loss, whereas the correlation improves if the OAE level is compared to the pure tone threshold measured in a later session. The slopes of individual trajectories that connect the successive results of one ear in a plane defined by hearing loss and OAE level show a remarkable accumulation around zero, i.e., in many cases the OAEs remain unchanged even if the hearing loss decreases. The comparison of the OAE levels measured at an early stage with later audiograms shows that there are only a small number of cases with small initial emissions and good final threshold or large initial emissions and bad final threshold. This means that small initial OAEs end up with a remaining final hearing deficit, whereas a high OAE level immediately after drop of threshold correlates with good outcome. The reliability of an individual prediction based on the OAE level combined with the threshold after sudden hearing loss and the consequences for the physiologic mechanisms underlying the sudden hearing loss remain to be proved in further investigations.

Hearing screening of high risk newborn infants

This prospective study reports on the prevalence of hearing impairment in an at-risk neonatal intensive care unit (NICU) population. From 1990 to 1998, 1062 neonates were screened with the use of transitory evoked otoacoustic emissions (TEOAE) and brainstem evoked response audiometry (BERA). 934 infants passed the primary screen for both ears, 75 for one ear, adding up to 95%. 17 infants (1.6%) were lost to follow-up. In fourteen infants (1.3%), bilateral hearing impairment above 30 dB was confirmed. While all children with hearing impairment belonged to the group of 862 children receiving aminoglycosides, only one of them presented no other risk factors. In twelve of the hearing impaired children other anamnestic factors, i.e. dysmorphism, prenatal rubella or cytomegaly, family history of hearing loss or severe peri- and postnatal complications seem to be more probable causes of the identified hearing loss. In one of these children, delayed onset or progression of hearing loss is suspected. From our data, aminoglycosides are not an important risk factor for hearing impairment, when serum levels are continuously monitored, as in our cohort. After adjustment for other risk factors, birth weight between 1000 gr and 1500 gr and a gestational age between 29 and 31 weeks were no predictive markers for hearing impairment. It might be speculated that the improved medical treatment in a NICU reduces the probability of hearing impairment for those two groups. Conductive hearing loss as a possible additional cause for hearing impairment was not studied in detail, but the high percentage of malformations detected (four out of fourteen hearing impaired infants) demands further monitoring, close follow-up, adequate treatment and counselling.

Improvement in the objective diagnosis of hearing disorders by a new technique of simultaneous recording of acoustic and electrical responses of the auditory system

The measurements of transitory evoked otoacoustic emissions (TEOAE) and auditory brainstem responses (ABR) are widely used in objective audiometry for the diagnosis of conductive or sensorineural hearing losses. In some cases only one of these signals is required for a complete diagnosis, while other cases may require both methods to define findings. With conventional equipment the measurement of TEOAE and ABR is performed with different devices at different times. Devices for simultaneous recording of both signals are currently not available or described, although the physiological circumstances and apparatus requirements would favor such an approach. In the present work a prototype for the simultaneous measurement of TEOAE and ABR is presented and its application tested in 33 normal-hearing adults. The equipment used was based on a general purpose laboratory computer connected to an acoustic stimulator and a dual-channel data acquisition system. Stimuli were composed of click sequences for the cancellation of linear signal components and were presented by an ear canal probe (Otodynamics) which also picked up the microphone signal within the outer ear canal. The EEG activity containing the ABR was recorded through surface electrodes fixed at the patient's vertex and mastoid. Acoustic and electric signals were processed simultaneously, resulting in three independent records representing a non-linear TEOAE and the low and high level ABR. The main advantages of the new approach are an improvement in information output and enhancement in the accuracy of determining the site and extent of a hearing impairment.

Hörverlust durch Hochdosis-Carboplatintherapie

Carboplatin is regarded as a non-ototoxic or low-grade ototoxic chemotherapeutic agent. We report on three patients with a recurrence of testicular cancer after cisplatin chemotherapy who suffered hearing loss after subsequent high-dose carboplatin therapy. Audiometry demonstrated carboplatin-induced hearing loss primarily in the mid-range and high frequencies up to 45 dB at 3 kHz and up to 55 dB at 8 kHz. In two of three patients, transitory-evoked otoacoustic emissions were absent after carboplatin therapy. Following first-line cisplatin chemotherapy, salvage treatment with high-dose carboplatin can generate hearing loss in the middle and high frequencies.

Cold deformation elements for attaching an implantable hearing aid transducer to ear ossicles or perilymph

Development and short-term implantation results of the Tübingen implantable hearing aid (TI = Tübingen implant) have been presented. The TI is designed for patients with sensorineural hearing loss due to a malfunction of the cochlear amplifier. This can be identified by the presence of positive recruitment and the absence of TEOAE (transitory evoked otoacoustic emissions). The Tübingen implant functions in two ways: it allows electronic amplification of the auditory signal and electromechanical signal transduction into a micromechanical vibratory stimulus. There are two paths by which vibratory stimulus reaches the cochlea: (1) directly through a perforation in the stapes foot plate into the perilymph or (2) via the ossicular chain. Made of pure titanium, the casing of the helium-tight welded transducer includes the piezoelectric actuator. An implantable manipulator device is designed for transducer positioning and anchoring in the mastoid cavity. Usually, the transducer probe tip is directly coupled to the body of the incus. This functions without a special coupling device by utilization of an Erbium-YAG laser. Special anatomical situations or the loss of incus and/or stapes suprastructure, however, requires coupling of the vibratory signal to other points of the ossicular chain or to the perilymph. A major problem, however, was an intraoperative, irreversible link between the titanium probe tip and coupling elements. To overcome this problem, the coupling elements were made of gold. A crimp technique was developed, allowing the surgeon to induce cold deformation of the gold. The cold deformation technique (crimp) results in an irreversible coupling between the titanium probe tip and the golden coupling element.

Relations between notched-noise suppressed TEOAE and the psychoacoustical critical bandwidth.

Narrow-band transitory evoked otoacoustic emissions (TEOAE) were recorded for nine normal hearing subjects in the presence of a broadband tone complex suppressor. Introducing a spectral notch at the frequency of the narrow-band stimulus causes the suppression effect to decrease, the more so the wider the notch. This decrease in suppression permits an estimate of the size of one critical band. One advantage of this approach is that no active participation of the subjects is required. The estimated critical bandwidth is then compared with independent estimates based on a simultaneous masking experiment, using the same stimuli. The two measures of the critical bandwidth coincide well for those six subjects with spontaneous otoacoustic emissions. However, the bandwidth estimate based on the OAE measurements is too large for the other three subjects without spontaneous emissions. Simulations of the suppression effect with a driven van der Pol oscillator with moderate undamping produce critical bandwidth estimates consistent with those observed in the psychoacoustical experiments. This allows an estimate of the "effective" amount of undamping on the basilar membrane that is required to produce the critical bandwidth observable in psychoacoustic experiments.

Interaction of otoacoustic emissions with additional tones: suppression or synchronization?

The influence of an external tone on transitory evoked otoacoustic emissions (TEOAE) is investigated. Three different averaging techniques were used with the same acoustic stimulus paradigm. These techniques permitted the separation of those parts of the otoacoustic emission (OAE) that contribute to the transitory evoked otoacoustic emission and those parts of the OAE that are synchronized to the continuous tone. The experiments show that the total energy of the OAE is not reduced in the presence of an additional tone. The ‘suppression’ of TEOAEs is an effect of synchronization and the subsequent elimination of the ‘suppressed’ emission in the averaging procedure.

Effect of inner ear hearing loss on delayed otoacoustic emissions (TEOAE) and distortion products (DPOAE)

The assessment of inner ear hearing loss by means of evoked otoacoustic emissions (EOAE) is already established in practice. Nevertheless, empirical data on the relations between emission and audiologic parameters are required. EOAEs werde measured and analysed in 240 ears with sensorineural hearing loss (excluding cases with conductive and retrocochlear disorders) of 120 patients using ILO88/92 equipment with standard test conditions. Audiologic examination consisted of pure tone audiogram, tympanometry and auditory brainstem responses. The results of TEOAE (Transitory Evoked Otoacoustic Emissions), measured with clicks at 80 dB SPL, and DPOAE (Distortion Product Otoacoustic Emissions), measured with frequencies ranging from f2 = 1 kHz to 4 kHz at 70 dB SPL (L2 = L1, f2 = 1.2 f1), were compared to each other and to the hearing thresholds determined by subjective pure tone audiometry. A significant negative correlation is found between the amplitude of TEOAEs and the average hearing loss in the range of 0.5 to 4 kHz. Similarly, the amplitude of DPOAEs is significantly correlated to the hearing threshold encountered at the higher of the two stimulus frequencies. Nevertheless, the prediction of hearing loss from the response amplitude is not possible because of its large amplitude variations between individuals. The analysis of the relation between incidence of EOAEs and hearing loss shows that in ears exceeding a hearing loss of 34 +/- 4 dB (minimal value of subjective thresholds in the range 0.5 to 4 kHz) no TEOAEs can be registered. For DPOAEs, the responses disappear if the hearing loss at the higher stimulus frequency exceeds 47 +/- 3 dB (limits for 50% OAE incidence are given in both cases). In conclusion, the hearing thresholds of ears exhibiting DPOAEs but no TEOAEs are located between approximately 30 and 50 dB HL. The sharpness of the transition between clear responses and absent responses decreases with increasing age. Therefore, the combination of TEOAE and DPOAE recording with the purpose of hearing threshold assessment is especially useful in young patients. Further evaluation shows that male and female patients do not differ in the hearing loss dependent prevalence of otoacoustic emissions. On he other hand, a systematic but not significant influence of the audiogram shape on the parameters of the discrimination function can be observed: steep audiograms are described with a discrimination function, which drops to zero at higher levels of hearing loss and with a larger slope than shallow audiograms. The comparison of right and left ear emissions of the same patient shows that large amplitude differences occur even in cases of comparable subjective thresholds; missing emissions in one ear are observed if and only if the interaural threshold difference exceeds 30 dB.

Otoacoustic emissions (TEOAE and DPOAE) after middle ear operation

The behavior of transitory evoked otoacoustic emissions (TEOAE) and distortion products (DPOAE) in patients after middle ear surgery is unknown. We examined TEOAEs and DPOAEs in 37 ears following stapes surgery, 16 ears following tympanoplasty type I, and nine ears after reconstruction of the ossicular chain. In all patients, the postoperative conductive hearing loss was less than 15 dB HL. In some cases, there was additional sensorineural hearing loss in the high frequencies. Surprisingly, TEOAEs were present only in 10 of 62 ears postoperatively compared to all 22 control subjects. TEOAEs were detected in four of 37 ears after stapes surgery, in six of 16 ears after tympanoplasty type I, and in none of the nine ears who had undergone reconstruction of the ossicular chain. DPOAEs were detected in only four of 31 ears postoperatively compared to all 22 control ears. These results and their relation to the retrograde OAE transmission in the middle ear are discussed. Changes enhancing the stiffness of the middle ear seem to have a greater effect than those enhancing the mass.

Der Einfluß einer Sedierung auf die otoakustischen Emissionen*

Even though the measurement of transitory evoked otoacoustic emissions (TEOAE) is easy and without problems in babies, sedation might be necessary in children aged between 1 and 4 years. As only very little information is available on the influence of a sedation on the TEOAE, the present study was performed. 35 normal hearing patients who were treated with benzodiazepines as a premedication for an operation were included in the investigation. 15 patients received diazepam and 20 were given flunitrazepam in a dosage of 10 and 1 mg respectively. The TEOAE were measured using the ILO 88 system by Bray and Kemp 1 day before, 1 hour after and 3 days after drug intake. 10 additional subjects of whom measurements were taken at the same time intervals served as controls. No statistically significant changes could be detected before and after drug treatment in respect of amplitudes of the TEOAE and frequency of maximum amplitudes. Hence, we conclude that sedation as used in this study must be considered negligible when measuring TEOAE.

Changes in otoacoustic emissions with simultaneous acoustic stimulation of the contralateral ear in normal probands and patients with unilateral acoustic neurinoma

Contralateral white noise alters the amplitude of transitory evoked otoacoustic emissions (TEOAE). 27 students between 20 and 28 years of age with no history of ear disease or dizziness were tested for normal hearing by pure tone audiogram. OAE evoked by nonlinear stimuli were measured with and without contralateral stimulation by 40, 50 and 60 dB white noise. The contralateral stimulation resulted in a statistically significant diminution of the amplitude of the TEOAE under contralateral acoustic stimulation. This diminution is probably caused by the effect of the crossed bundle of the efferent innervation on the outer hair cells resulting in altered vibratory properties of the basilar membrane. In patients with unilateral acoustic neuroma and measurable TEOAE a diminution of the amplitude of the TEOAE under contralateral sound stimulation was not found. The testing can easily be performed with the routine measurement of TEOAE. It could be useful in the diagnostic of lesions of the cerebello pontine angle and the brain stem.