Objective estimation of loudness growth in hearing-impaired listeners

A methodology for the estimation of individual loudness growth functions using tone-burst otoacoustic emissions (TBOAEs) and tone-burst auditory brainstem responses (TBABRs) was proposed by Silva and Epstein [J. Acoust. Soc. Am. 127, 3629-3642 (2010)]. This work attempted to investigate the application of such technique to the more challenging cases of hearing-impaired listeners. The specific aims of this study were to (1) verify the accuracy of this technique with eight hearing-impaired listeners for 1- and 4-kHz tone-burst stimuli, (2) investigate the effect of residual noise levels from the TBABRs on the quality of the loudness growth estimation, and (3) provide a public dataset of physiological and psychoacoustical responses to a wide range of stimuli intensity. The results show that some of the physiological loudness growth estimates were within the mean-square-error range for standard psychoacoustical procedures, with closer agreement at 1 kHz. The median residual noise in the TBABRs was found to be related to the performance of the estimation, with some listeners showing strong improvements in the estimated loudness growth function when controlling for noise levels. This suggests that future studies using evoked potentials to estimate loudness growth should control for the estimated averaged residual noise levels of the TBABRs.

Unilateral auditory neuropathy spectrum disorder

CONCLUSIONS

The majority of the patients with unilateral auditory neuropathy spectrum disorder (UANSD) were pediatric and mostly showed a great degree of hearing loss when diagnosed. Abnormal auditory brainstem response (ABR) and preserved otoacoustic emissions (OAEs) and/or cochlear microphonics (CM) were important features to differentiate it from common sensorineural deafness and central nerve hearing loss.

OBJECTIVE

To identify the clinical characteristics of patients with UANSD.

METHODS

This was a retrospective study involving 14 patients diagnosed as having UANSD between 2004 and 2010 in the Chinese PLA Hospital.

RESULTS

In all, 50% of the cases were males (1:1 sex ratio) and the average age of onset was 4.1 years. Of the 14 affected ears with UANSD in these cases, 6 were left-sided, while 8 were right-sided. Of the 14 contralateral ears, 4 presented with sensorineural hearing loss, while the other 10 showed normal hearing. The degree of hearing loss in the 14 affected ears varied, including moderate in 1, moderately severe in 4, severe in 5, and profound in 4. ABRs were absent in the 14 affected ears, while the OAEs, and/or CM were present.

[Currently possibilities for diagnostics and electroacoustical correction of hearing in the children]

This study was designed to compare different objective methods applied to study the hearing function in 132 children presenting with sensorineural impairment of hearing and deafness. It was focused on the assessment of risk factors of congenital and acquired loss of hearing and deafness. In addition, the factors influencing the efficacy and quality of electroacoustical correction of hearing in the children were considered including those of importance after cochlear implantation.

From otoacoustic emission to late auditory potentials P300: the inhibitory effect

This study verifies the effects of contralateral noise on otoacoustic emissions and auditory evoked potentials. Short, middle and late auditory evoked potentials as well as otoacoustic emissions with and without white noise were assessed. Twenty-five subjects, normal-hearing, both genders, aged 18 to 30 years, were tested . In general, latencies of the various auditory potentials were increased at noise conditions, whereas amplitudes were diminished at noise conditions for short, middle and late latency responses combined in the same subject. The amplitude of otoacoustic emission decreased significantly in the condition with contralateral noise in comparison to the condition without noise. Our results indicate that most subjects presented different responses between conditions (with and without noise) in all tests, thereby suggesting that the efferent system was acting at both caudal and rostral portions of the auditory system.

Function of the medial olivocochlear system in children with phonological disorders

PURPOSE

To verify whether children with phonological disorders present alterations in the medial olivocochlear system.

METHODS

This is a prospective cross-sectional study in which 19 normal hearing children of both genders, with ages between 4 and 7 years, were divided into two groups: 11 children without phonological disorders (control group) and eight with phonological disorders (study group). The auditory condition was verified by visual examination of the external ear canal, pure tone audiometry, and tympanometry. The study included only children with hearing thresholds below or equal to 15 dB, type A tympanometry, and presence of acoustic reflexes. To evaluate the function of the medial olivocochlear system, it was carried out the evaluation of transient evoked otoacoustic emissions (TEOAE) with and without contralateral white noise at 60 dBHL. Data were statistically analyzed.

RESULTS

The occurrence and average values of TEOAE suppression in right and left ears did not present differences in the frequencies of 1, 2, 3 and 4 kHz within groups. In the comparison of the mean and the occurrence of the suppressive effect of TEOAE between control and study groups, there was also no difference in the frequencies analyzed.

CONCLUSION

Children with phonological disorders do not present alterations in the medial olivocochlear system, as evidenced by the occurrence of the suppressive effect of transient evoked otoacoustic emissions.

Assessment of the peripheral hearing system of sport divers

OBJECTIVE

To investigate the effect of regular scuba diving on the hearing thresholds of sport divers who have no history of noise exposure or ear-related accidents. Comprehensive topographic examination of the peripheral hearing system of sport divers.

DESIGN

Cross-sectional study.

SETTINGS

General sport diving community.

PARTICIPANTS

81 sport divers with a mean of 300 dives each were compared to a control group of 81 non-divers.

MAIN OUTCOME MEASURE

Participants were classified into three age groups. Examination included microscopic otoscopy, tympanometry, pure-tone audiometry (PTA) including air and bone conduction, speech audiometry and otoacoustic emissions (OAE).

RESULTS

PTA suggested significant differences of the hearing thresholds at several frequencies between sport divers and non-divers in all age groups, although a Bonferroni correction for multiple testing was applied. Interestingly, the results were contradictory. Divers obtained better hearing results in air conduction, whereas non-divers showed better results in bone conduction. Speech audiometry and OAE did not reveal significant differences.

CONCLUSION

There are no published studies of the peripheral cochlear system of divers that have used a combination of PTA, speech audiometry and OAE. All studies suggesting hearing impairment in divers were based on PTA and might have been influenced by a lack of accuracy of PTA. Our results suggest that diving does not adversely affect the hearing system of sport divers. A thorough test battery of audiological methods implying PTA, speech audiometry and OAE may contribute to offer more reliable results to answer the question of whether commercial or military divers are at higher risk for hearing detoriation.

Effects of low-frequency biasing on otoacoustic and neural measures suggest that stimulus-frequency otoacoustic emissions originate near the peak region of the traveling wave

Stimulus-frequency otoacoustic emissions (SFOAEs) have been used to study a variety of topics in cochlear mechanics, although a current topic of debate is where in the cochlea these emissions are generated. One hypothesis is that SFOAE generation is predominately near the peak region of the traveling wave. An opposing hypothesis is that SFOAE generation near the peak region is deemphasized compared to generation in the tail region of the traveling wave. A comparison was made between the effect of low-frequency biasing on both SFOAEs and a physiologic measure that arises from the peak region of the traveling wave--the compound action potential (CAP). SFOAE biasing was measured as the amplitude of spectral sidebands from varying bias tone levels. CAP biasing was measured as the suppression of CAP amplitude from varying bias tone levels. Measures of biasing effects were made throughout the cochlea. Results from cats show that the level of bias tone needed for maximum SFOAE sidebands and for 50% CAP reduction increased as probe frequency increased. Results from guinea pigs show an irregular bias effect as a function of probe frequency. In both species, there was a strong and positive relationship between the bias level needed for maximum SFOAE sidebands and for 50% CAP suppression. This relationship is consistent with the hypothesis that the majority of SFOAE is generated near the peak region of the traveling wave.

Effects of changes in dynamic characteristics of the middle ear on transient-evoked otoacoustic emissions

Transient-evoked otoacoustic emissions are transmitted through the middle ear. The purpose of this study was to investigate the effects of dynamic properties of the transmission system on the measurability of transient otoacoustic emissions. The authors analyzed the presence of transient otoacoustic emissions in 48 children with serous otitis media regarding the tympanogram, presence and type of effusion and pure tone average findings. The results obtained in this research show the predominant absence of transient otoacoustic emissions in patients with type B tympanogram (69.1%) especially if the effusion is mucoid (77.5%) with the hearing loss of 15 decibel hearing level. This research shows that disorders in dynamic characteristics of the middle ear in patients with serous otitis obstruct the transmission of acoustic energy and affect the measurability of transient otoacoustic emissions, especially if the effusion is mucoid and hearing loss of 15 decibel hearing level.

Point vowel duration in children with hearing aids and cochlear implants at 4 and 5 years of age

This work investigates the developmental aspects of the duration of point vowels in children with normal hearing compared with those with hearing aids and cochlear implants at 4 and 5 years of age. Younger children produced longer vowels than older children, and children with hearing loss (HL) produced longer and more variable vowels than their normal hearing peers. In this study, children with hearing aids and cochlear implants did not perform differently from each other. Test age and HL did not interact, indicating parallel but delayed development in children with HL compared with their typically developing peers. Variability was found to be concentrated among the high vowels /u, i / but not in the low vowels /ae, a / . The broad findings of this work are consistent with previous reports and contribute a detailed description of point vowel duration not in the literature.

Dose-dependent protection on cisplatin-induced ototoxicity - an electrophysiological study on the effect of three antioxidants in the Sprague-Dawley rat animal model

BACKGROUND

Sprague-Dawley rats were used as an acute cisplatin ototoxicity model to compare the chemo-protective efficacy of 2 sulphur-containing antioxidants (D-methionine, N-L-acetylcysteine) and 1 seleno-organic compound (ebselen). Each putative chemo-protective agent was tested at 3 different dosages in order to assess the influence of dose on auditory preservation.

MATERIAL/METHODS

A total of 40 Sprague-Dawley albino male rats were used in the study. Animals were divided into 10 groups, 3 groups of different doses for each protective agent and a cisplatin-treated control group. The animals were weight-matched before drug exposure to ensure similar weights in all groups. Auditory function was assessed with auditory brainstem responses and distortion product otoacoustic emissions at time zero and at 96 hours post-treatment.

RESULTS

At the post-treatment follow-up no significant threshold change at 8 kHz was found in the D-Met- and NAC-treated groups. All ebselen-treated animals presented significant threshold elevations. At 12 and 16 kHz, only the groups treated with 300, 450 mg/kg of D-Met and 475 mg/kg of NAC presented thresholds comparable to the pre-treatment ABR data. The ebselen-treated animals presented significant threshold shifts and showed the highest threshold elevations. The DPOAE data analysis showed that only the animals from the 350 mg/kg D-met group presented lack of statistical differences between the pre and post recordings.

CONCLUSIONS

Considering the outcome from the ABR and DPOAE analyses together, only the 350 mg/kg D-met group presented a complete auditory preservation against the 14 mg/kg cisplatin administered i.v. Data from ebselen pre-treated Sprague-Dawley albino male rats demonstrate that ebselen dosages up to 12 mg/kg given by i.p. administration lack auditory preservation in this species.

Frequency of congenital hearing loss in 43,503 healthy newborn infants in Konya, Turkey

OBJECTIVE

To determine the frequency of congenital hearing loss (CHL) in healthy newborn infants in Konya, Turkey.

METHODS

A total of 43,503 healthy neonates born at Doctor Faruk Sükan Obstetrics and Children's Hospital between the years of 2006 and 2011 were evaluated, prospectively. Hearing screening test was carried out using Transient Evoked Otoacoustic Emission (TEOAE) method. Hearing test was also repeated three times in neonates with suspected hearing loss in first month of life. Infants with abnormal hearing test were referred to Department of Ear, Nose and Throat Selçuk University, Meram Faculty of Medicine, Konya, Turkey. Evoked auditory brainstem responses (E-ABR) were performed in these cases. Infants with abnormal E-ABR were referred to further centers for cochlear implantation.

RESULTS

Hearing test was found to be abnormal in 226 (5.19/1,000) infants based on the results of TEOAE, repeated three times. CHL was diagnosed in 216 (4.97/1,000) of 226 infants at the end of E-ABR. These 216 infants were referred for cochlear implantation.

CONCLUSION

Our findings showed that TEOAE method is highly effective in neonatal hearing screening and frequency of CHL was 4.97/1,000 in our region.

Outcome of a universal newborn hearing-screening programme based on multiple transient-evoked otoacoustic emissions and clinical brainstem response audiometry

CONCLUSION

This universal newborn hearing-screening (UNHS) programme revealed high efficacy. The proportion of congenital sensorineural hearing loss was higher in left ears and in males than in right ears and females, which was in line with the systematic ear asymmetries and sex differences in transient-evoked otoacoustic emission (TEOAE) pass percentage.

OBJECTIVES

To study the long-term outcome of a UNHS programme based on multiple TEOAEs and clinical click-evoked auditory brainstem response (ABR).

METHOD

The study included all the newborns that were screened during a 6-year period (n = 31 092). TEOAE pass/fail was analysed in detail. In an assessment performed 10 years after the start of the 6-year UNHS, prevalence, degree and type of congenital hearing loss were studied.

RESULTS

The proportion of screened newborns was high, i.e. 98%. Multiple TEOAE recordings minimized the need for clinical ABR. Fifty-seven (0.18%) subjects showed bilateral hearing loss (exceeding ≈ 30 dB HL); median ABR threshold = 60 dB nHL (at 2.5 months of age). Bilateral and unilateral sensorineural hearing loss was found in 0.17% (n = 52; 56% males) and 0.06% (n = 18; 61% left ears, 56% males) of the screened newborns, respectively. Higher TEOAE pass percentages (p < 0.01) were demonstrated in right ears and in females than in left ears and males.

A connection between the Efferent Auditory System and Noise-Induced Tinnitus Generation. Reduced contralateral suppression of TEOAEs in patients with noise-induced tinnitus

BACKGROUND

Subjective tinnitus is an auditory perception that is not caused by external stimulation, its source being anywhere in the auditory system. Furthermore, evidence exists that exposure to noise alters cochlear micromechanics, either directly or through complex feed-back mechanisms, involving the medial olivocochlear efferent system. The aim of this study was to assess the role of the efferent auditory system in noise-induced tinnitus generation.

MATERIAL/METHODS

Contralateral sound-activated suppression of TEOAEs was performed in a group of 28 subjects with noise-induced tinnitus (NIT) versus a group of 35 subjects with normal hearing and tinnitus, without any history of exposure to intense occupational or recreational noise (idiopathic tinnitus-IT). Thirty healthy, normally hearing volunteers were used as controls for the efferent suppression test.

RESULTS

Suppression of the TEOAE amplitude less than 1 dB SPL was considered abnormal, giving a false positive rate of 6.7%. Eighteen out of 28 (64.3%) patients of the NIT group and 9 out of 35 (25.7%) patients of the IT group showed abnormal suppression values, which were significantly different from the controls' (p<0.0001 and p<0.045, respectively).

CONCLUSIONS

The abnormal activity of the efferent auditory system in NIT cases might indicate that either the activity of the efferent fibers innervating the outer hair cells (OHCs) is impaired or that the damaged OHCs themselves respond abnormally to the efferent stimulation.

A new method to analyze distortion product otoacoustic emissions (DPOAEs) in the high-frequency range up to 18 kHz using windowed periodograms

Distortion product otoacoustic emissions (DPOAEs) are widely used as an objective examination procedure to determine cochlear function. In a clinical routine setting, the amplitude of the DPOAE signal at 2f1 .. f2 is applied as an indicator for a potential hearing loss up to 8 kHz. Due to their poor signal to noise ratio, meatal nodes from standing waves and calibration issues, high-frequency DPOAEs > 8 kHz have hardly been addressed in experimental and clinical audiology so far. Here, we present a new method of measuring DPOAE signal levels based on optimal maximum likelihood estimation with windowed power spectral density estimation of stochastic signals and filtering theory. Analysis of simulated data showed that the proposed method effectively reduces the disturbing noise floor compared to conventional averaging techniques. Robust DPOAE signals were measured in 20 ears from 10 normally hearing young adults (21 to 27 years) from 0:5 to 18 kHz. Repeated DPOAE recordings in one individual yielded a good to very good testretest reliability of the proposed method. These observations are discussed in the context of DPOAE signal processing and possible clinical applications of high-frequency DPOAE measurements.

Characterizing distortion-product otoacoustic emission components across four species

Distortion-product otoacoustic emissions (DPOAEs) were measured as level/phase (L/P) maps in humans, rabbits, chinchillas, and rats with and without an interference tone (IT) placed either near the 2f(1)-f(2) DPOAE frequency place (f(dp)) or at one-third of an octave above the f(2) primary tone (1/3-oct IT). Vector differences between with and without IT conditions were computed to derive a residual composed of the DPOAE components removed by the IT. In humans, a DPOAE component could be extracted with the expected steep phase gradient indicative of reflection emissions by ITs near f(dp). In the laboratory species, ITs near f(dp) failed to produce any conclusive evidence for reflection components. For all species, 1/3-oct ITs extracted large DPOAE components presumably generated at or basal to the IT-frequency place that exhibited both distortion- and reflection-like phase properties. Together, these findings suggested that basal distortion components could assume reflection-like phase behavior when the assumptions of cochlear-scaling symmetry, the basis for shallow phase gradients for constant f(2)/f(1) ratio sweeps, are violated. The present results contradict the common belief that DPOAE components associated with steep or shallow phase slopes are unique signatures for reflection emissions arising from f(dp) or distortion emissions generated near f(2), respectively.

The breaking of cochlear scaling symmetry in human newborns and adults

Scaling symmetry appears to be a fundamental property of the cochlea as evidenced by invariant distortion product otoacoustic emission (DPOAE) phase above ∼1-1.5 kHz when using frequency-scaled stimuli. Below this frequency demarcation, phase steepens. Cochlear scaling and its breaking have been described in the adult cochlea but have not been studied in newborns. It is not clear whether immaturities in cochlear mechanics exist at birth in the human neonate. In this study, DPOAE phase was recorded with a swept-tone protocol in three, octave-wide segments from 0.5 to 4 kHz. The lowest-frequency octave was targeted with increased signal averaging to enhance signal-to-noise ratio (SNR) and focus on the apical half of the newborn cochlea where breaks from scaling have been observed. The results show: (1) the ear canal DPOAE phase was dominated by the distortion-source component in the low frequencies; thus, the reflection component cannot explain the steeper slope of phase; (2) DPOAE phase-frequency functions from adults and infants showed an unambiguous discontinuity around 1.4 and 1 kHz when described using two- and three-segment fits, respectively, and (3) newborns had a significantly steeper slope of phase in the low-frequency portion of the function which may suggest residual immaturities in the apical half of the newborn cochlea.

Level dependence of distortion product otoacoustic emission phase is attributed to component mixing

Distortion product otoacoustic emissions (DPOAEs) measured in the ear canal represent the vector sum of components produced at two regions of the basilar membrane by distinct cochlear mechanisms. In this study, the effect of stimulus level on the 2f(1) - f(2) DPOAE phase was evaluated in 22 adult subjects across a three-octave range. Level effects were examined for the mixed DPOAE signal measured in the ear canal and after unmixing components to assess level effects individually on the distortion (generated at the f(1), f(2) overlap) and reflection (at f(dp)) sources. Results show that ear canal DPOAE phase slope becomes steeper with decreasing level; however, component analysis further explicates this result, indicating that interference between DPOAE components (rather than a shift in mechanics related to distortion generation) drives the level dependence of DPOAE phase measured in the ear canal. The relative contribution from the reflection source increased with decreasing level, producing more component interference and, at times, a reflection-dominated response at the lowest stimulus levels. These results have implications for the use of DPOAE phase to study cochlear mechanics and for the potential application of DPOAE phase for clinical purposes.

Temporal aspects of suppression in distortion-product otoacoustic emissions

This study examined the time course of cochlear suppression using a tone-burst suppressor to measure decrement of distortion-product otoacoustic emissions (DPOAEs). Seven normal-hearing subjects with ages ranging from 19 to 28 yr participated in the study. Each subject had audiometric thresholds ≤ 15 dB HL [re ANSI (2004) Specifications for Audiometers] for standard octave and inter-octave frequencies from 0.25 to 8 kHz. DPOAEs were elicited by primary tones with f(2) = 4.0 kHz and f(1) = 3.333 kHz (f(2)/f(1) = 1.2). For the f(2), L(2) combination, suppression was measured for three suppressor frequencies: One suppressor below f(2) (3.834 kHz) and two above f(2) (4.166 and 4.282 kHz) at three levels (55, 60, and 65 dB SPL). DPOAE decrement as a function of L(3) for the tone-burst suppressor was similar to decrements obtained with longer duration suppressors. Onset- and setoff- latencies were ≤ 4 ms, in agreement with previous physiological findings in auditory-nerve fiber studies that suggest suppression results from a nearly instantaneous compression of the waveform. Persistence of suppression was absent for the below-frequency suppressor (f(3) = 3.834 kHz) and was ≤ 3 ms for the two above-frequency suppressors (f(3) = 4.166 and 4.282 kHz).

Breaking away: violation of distortion emission phase-frequency invariance at low frequencies

The phase versus frequency function of the distortion product otoacoustic emission (DPOAE) at 2f(1) - f(2) is approximately invariant at frequencies above 1.5 kHz in human subjects when recorded with a constant f(2)/f(1). However, a secular break from this invariance has been observed at lower frequencies where the phase-gradient becomes markedly steeper. Apical DPOAEs, such as 2f(1) - f(2), are known to contain contributions from multiple sources. This experiment asked whether the phase behavior of the ear canal DPOAE at low frequencies is driven by the phase of the component from the distortion product (DP) region at 2f(1) - f(2), which exhibits rapid phase accumulation. Placing a suppressor tone close in the frequency to 2f(1) - f(2) reduced the contribution of this component to the ear canal DPOAE in normal-hearing adult human ears. When the contribution of this component was reduced, the phase behavior of the ear canal DPOAE was not altered, suggesting that the breaking from DPOAE phase invariance at low frequencies is an outcome of apical-basal differences in cochlear mechanics. The deviation from DPOAE phase invariance appears to be a manifestation of the breaking from approximate scaling symmetry in the human cochlear apex.

Distribution of standing-wave errors in real-ear sound-level measurements

Standing waves can cause measurement errors when sound-pressure level (SPL) measurements are performed in a closed ear canal, e.g., during probe-microphone system calibration for distortion-product otoacoustic emission (DPOAE) testing. Alternative calibration methods, such as forward-pressure level (FPL), minimize the influence of standing waves by calculating the forward-going sound waves separate from the reflections that cause errors. Previous research compared test performance (Burke et al., 2010) and threshold prediction (Rogers et al., 2010) using SPL and multiple FPL calibration conditions, and surprisingly found no significant improvements when using FPL relative to SPL, except at 8 kHz. The present study examined the calibration data collected by Burke et al. and Rogers et al. from 155 human subjects in order to describe the frequency location and magnitude of standing-wave pressure minima to see if these errors might explain trends in test performance. Results indicate that while individual results varied widely, pressure variability was larger around 4 kHz and smaller at 8 kHz, consistent with the dimensions of the adult ear canal. The present data suggest that standing-wave errors are not responsible for the historically poor (8 kHz) or good (4 kHz) performance of DPOAE measures at specific test frequencies.

Distortion products and backward-traveling waves in nonlinear active models of the cochlea

This study explores the phenomenology of distortion products in nonlinear cochlear models, predicting their amplitude and phase along the basilar membrane. The existence of a backward-traveling wave at the distortion-product frequency, which has been recently questioned by experiments measuring the phase of basilar-membrane vibration, is discussed. The effect of different modeling choices is analyzed, including feed-forward asymmetry, micromechanical roughness, and breaking of scaling symmetry. The experimentally observed negative slope of basilar-membrane phase is predicted by numerical simulations of nonlinear cochlear models under a wide range of parameters and modeling choices. In active models, positive phase slopes are predicted by the quasi-linear analytical computations and by the fully nonlinear numerical simulations only if the distortion-product sources are localized apical to the observation point and if the stapes reflectivity is unrealistically small. The results of this study predict a negative phase slope whenever the source is distributed over a reasonably wide cochlear region and/or a reasonably high stapes reflectivity is assumed. Therefore, the above-mentioned experiments do not contradict "classical" models of cochlear mechanics and of distortion-product generation.

Fast and slow effects of medial olivocochlear efferent activity in humans

Background

The medial olivocochlear (MOC) pathway modulates basilar membrane motion and auditory nerve activity on both a fast (10–100 ms) and a slow (10–100 s) time scale in guinea pigs. The slow MOC modulation of cochlear activity is postulated to aide in protection against acoustic trauma. However in humans, the existence and functional roles of slow MOC effects remain unexplored.

Methodology/Principal Findings

By employing contralateral noise at moderate to high levels (68 and 83 dB SPL) as an MOC reflex elicitor, and spontaneous otoacoustic emissions (SOAEs) as a non-invasive probe of the cochlea, we demonstrated MOC modulation of human cochlear output both on a fast and a slow time scale, analogous to the fast and slow MOC efferent effects observed on basilar membrane vibration and auditory nerve activity in guinea pigs. The magnitude of slow effects was minimal compared with that of fast effects. Consistent with basilar membrane and auditory nerve activity data, SOAE level was reduced by both fast and slow MOC effects, whereas SOAE frequency was elevated by fast and reduced by slow MOC effects. The magnitudes of fast and slow effects on SOAE level were positively correlated.

Conclusions/Significance

Contralateral noise up to 83 dB SPL elicited minimal yet significant changes in both SOAE level and frequency on a slow time scale, consistent with a high threshold or small magnitude of slow MOC effects in humans.

Changes in amplitude and phase of distortion-product otoacoustic emission fine-structure and separated components during efferent activation

Medial olivocochlear (MOC) efferent fibers synapse directly on the outer hair cells (OHCs). Efferent activation evoked by contralateral acoustic stimulation (CAS) will affect OHC amplification and subsequent measures of distortion-product otoacoustic emissions (DPOAEs). The aim of this study was to investigate measures of total and separated DPOAEs during efferent activation. Efferent activation produces both suppression and enhancement of the total DPOAE level. Level enhancements occurred near fine-structure minima and were associated with consistent MOC evoked upward shifts in DPOAE fine-structure frequency. Examination of the phase of the separated components revealed that frequency shifts stemmed from increasing phase leads of the reflection component during CAS, while the generator component phase was nearly invariant. Separation of the two DPOAE components responsible for the fine-structure revealed more consistent reduction of the levels of both components. Using vector subtraction (which takes into account both level and phase) to estimate the changes in the unseparated DPOAE provided consistent evidence of DPOAE suppression. Including phase information provided a more sensitive, valid and consistent estimate of CAS function even if one does not know the position of the DPOAE in the fine-structure.

Comparison of otoacoustic emissions within gecko subfamilies: morphological implications for auditory function in lizards

Otoacoustic emissions (OAEs) are sounds emitted by the ear and provide a non-invasive probe into mechanisms underlying peripheral auditory transduction. This study focuses upon a comparison of emission properties in two phylogenetically similar pairs of gecko: Gekko gecko and Hemidactylus turcicus and Eublepharis macularius and Coleonyx variegatus. Each pair consists of two closely related species within the same subfamily, with quantitatively known morphological properties at the level of the auditory sensory organ (basilar papilla) in the inner ear. Essentially, the comparison boils down to an issue of size: how does overall body size, as well as the inner-ear dimensions (e.g., papilla length and number of hair cells), affect peripheral auditory function as inferred from OAEs? Estimates of frequency selectivity derived from stimulus-frequency emissions (emissions evoked by a single low-level tone) indicate that tuning is broader in the species with fewer hair cells/shorter papilla. Furthermore, emissions extend outwards to higher frequencies (for similar body temperatures) in the species with the smaller body size/narrower interaural spacing. This observation suggests the smaller species have relatively improved high-frequency sensitivity, possibly related to vocalizations and/or aiding azimuthal sound localization. For one species (Eublepharis), emissions were also examined in both juveniles and adults. Qualitatively similar emission properties in both suggests that inner-ear function is adult like soon after hatching and that external body size (e.g., middle-ear dimensions and interaural spacing) has a relatively small impact upon emission properties within a species.

Distortion-product otoacoustic-emission suppression tuning in human infants and adults using absorbed sound power

The greatest difference in distortion product otoacoustic emission (DPOAE) suppression tuning curves (STCs) in infant and adult ears occurs at a stimulus frequency of 6 kHz. These infant and adult STCs are much more similar when constructed using the absorbed power level of the stimulus and suppressor tones rather than using sound pressure level. This procedure incorporates age-related differences in forward and reverse transmission of sound power through the ear canal and middle ear. These results support the theory that the cochlear mechanics underlying DPOAE suppression are substantially mature in full-term infants.

[The functional state of the cochlea in premature infants born before 28 weeks gestation on the 6th month of life]

The objective of the present study was to assess the state of the peripheral portion of the auditory analyzer based on induced otoacoustic emissions (IOAEs), distortion product otoacoustic emissions (DPOAEs), and delayed IOAEs (DIOAEs). The study included 31 premature infants born before 28 weeks gestation and examined later on the 6th month of postnatal life. All of them were shown to have the underdeveloped cochlea. It was shown that the DPOAEs technique makes it possible to record induced otoacoustic emissions more frequently than the DIOAEs method. It is concluded that the hearing function in premature infants born before 28 weeks gestation should be evaluated on the 6th month of postnatal life based on two classes of emission.

Hearing level equalized otoacoustic emissions acquired by swept-tones: intensity characteristics

Otoacoustic emissions (OAE), which are acoustic responses produced by the cochlea, can be recorded with a microphone in the ear canal to give diagnostic information regarding cochlear functioning. Recently, the researchers developed a novel stimulus for the acquisition of OAE using a hearing-level equalized (HL(eq)) swept-tone signal. The objective of this study was to observe OAE characteristics at a multitude of intensities to track the changes in temporal and spectral morphology. An increase in high-frequency emissions was found as stimulation intensity decreased. Furthermore, it was found that hearing level equalized swept-tone OAEs (HL(eq) sTEAOE) can be acquired at very low intensities, which is not typical under current acquisition modalities. This may result in clinical improvements by providing a fast and cheap method for contributing to the detection of auditory thresholds.

[Prospects for the use of histaminergic preparations for the purpose of noise otoprotection]

The objective of the present study was to experimentally evaluate the otoprotective effect of the histaminergic preparation betagistin dihydrochloride given at a dose of 32 mg to 10 healthy male volunteers aged from 18 to 22 (mean 19.4) years who were exposed to 85 dB "white" nose for 1 hour. The functional state of their auditory system was estimated from the results of investigations including determination of the tonal auditory threshold, delayed evoked otoacoustic emission and distortion-product frequency otoacoustic emission, short-latency evoked auditory potentials, and extratympanic electrocochleography. It was shown that betagistin dihydrochloride produced a well-apparent otoprotective effect over the entire range of tests comprehensively characterizing the functional state of the cochlea. It is concluded that betagistin dihydrochloride has good prospects for the application in a variety of production activities (to treat occupational noise-induced pathology) including aerospace medicine.

[Modern aspects of diagnosis of presbycusis and its treatment in elderly patients]

This study was designed to evaluate the efficacy of tanakan used to treat tympanophonia in elderly women. The entire spectrum of modern audiological technique was employed to examine the patients. It was shown that tanakan therapy decreases intensity of typmanytis and improves speech hearing in aged patients. The results of the study give reason to recommend the treatment with tanakan for the elderly patients presenting with either presbiacusis or normal tonal hearing.

[The results of audiologic examination by the method of evoked otoacoustic emission in children born from multiple pregnancies]

The objectives of the present work were to study and evaluate the state of the peripheral portion of the acoustic analyzer in premature infants born after multiple pregnancies. The measurements were made by the so-called evoked otoacoustic emission technique. A total of 62 premature infants born after multiple pregnancies were available for the examination. Diagnostics of the hearing function by the method of evoked otoacoustic emission was performed using an ECLIPSE device (Interacoustics, Denmark). Analysis of the results of audiological examination indicates that up to 90.3% and 3.2% of the premature infants aged 6 months showed otoacoustic emission from both ears and from one ear respectively. 6.5% of the children failed otoacoustic emission screening.

[The functional state of the auditory analyzer in prematurely born infants (after 29 weeks of gestation) at 6 months of life]

The objective of the present study was to evaluate the functional state of the auditory analyzer in infants born prematurely (after 29 weeks of gestation) and examined at 6 months of life. The evoked otoacoustic emission (EOAE) techniques were used for the purpose. Testing with the help of two different modes of EOAE yielded virtually identical results which confirms the possibility to apply both delayed EOAE (dEOAE) and distortion-product frequency OAE (dpOAE) for the assessment of the auditory function. It is concluded that the degree of cochlear development in prematurely born infants (after 29 weeks of gestation) examined by the dpOAE technique at 6 months of life is significantly different from that in children born between the gestation age of 33 and 37 weeks.

Auditory monitoring by means of evaluation of the cochlea in soldiers of the Brazilian Army exposed to impulse noise

INTRODUCTION

Exposure to continuous or impulse noise may lead to High Sound Pressure Induced Hearing Loss (HSPIHL) or to acoustic trauma in soldiers. Auditory evaluation by means of evoked otoacoustic emissions (EOAE) has been demonstrating its importance in the detection of subtle changes in cochlear function still unidentified in threshold tone audiometry in subjects exposed to noise.

OBJECTIVE

Studying Distortion product otoacoustic emissions (DPOAEs) before and after exposure to impulse noise in soldiers of the Brazilian Army.

MATERIAL AND METHOD

This is an analytical, observational, longitudinal and prospective study. Auditory evaluation was performed by means of DPOAEs in 60 soldiers before and after exposure to impulse noise, of whom 30 were reevaluated immediately after exposure and 30 were reevaluated 24 hours after exposure.

RESULTS

The statistical analysis revealed that both groups reevaluated after exposure to impulse noise showed a decrease in amplitudes in comparison with the tests before exposure. As for the signal/noise ratio, there was a significant difference at the frequencies of 6 and 8KHz and there was a significant association between a tinnitus complaint and the group reevaluated immediately after exposure to noise.

CONCLUSION

The DPOAE test proved sensitive to detect subtle shifts after exposure to impulse noise, both with regard to the amplitude criterion and with regard to the signal/noise ratio even 24 hours after exposure. This demonstrated the applicability of the DPOAE test in monitoring the hearing of soldiers exposed to impulse noise.

[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).

[Functional examinations of the ear and auditory pathway]

Hearing is usually examined by means of pure tone and speech audiometry. Alternative examinations are required when the level of hearing defect needs to be more closely defined or hearing is being measured from a patient who is unable to give reliable feedback on a test sound. Neonatal hearing screening involves measuring of otoacoustic emissions generated in the cochlea of the inner ear or brain stem responses formed within the auditory pathway. Immittance measurements are used to evaluate the function of the middle ear. Most commonly used methods include tympanometry probing the mobility of the tympanic membrane and middle ear pressure, and acoustic reflex assessing the functionality of the ossicular chain.

Severe progressive sensorineural hearing loss improved after removal of large jugular foramen schwannoma

We report a very rare case of hearing improvement after removal of the intracranial part of a jugular foramen schwannoma (JFS) presenting with chronic and severe progressive sensorineural hearing loss (SNHL). The patient presented with progressive hearing impairment in his right ear, lasting 2 years. The patient's pure tone audiogram revealed severe SNHL. His speech discrimination score (SDS) was 0%. Auditory-evoked brain responses (ABRs) comprised only I waves following 30-100dB stimulation, although distortion-product otoacoustic emissions (DPOAEs) had good responses. These test results indicated that his hearing impairment was retrocochlear SNHL. Magnetic resonance imaging revealed within the right jugular foramen a large intracranial-extracranial tumor that compressed the brainstem. The intracranial part of the tumor was resected through retrosigmoidal craniotomy, and the tumor was pathologically diagnosed as a schwannoma. Several months after the operation, the patient's auditory thresholds improved to a level consistent with mild SNHL, ABR V waves emerged following 60-90dB stimulation, and SDS improved significantly to 95%. This case demonstrates that hearing improvement can be achieved after surgery for JFS presenting with severe and chronic progressive SNHL, and that good DPOAE responses and the presence of ABR I waves may be predictors of postoperative hearing recovery in JFS.

Evidence for surviving outer hair cell function in congenitally deaf ears

OBJECTIVES/HYPOTHESIS

The hypotheses of the study were that congenital hearing impairment in infants can result from the isolated loss of inner hair cells of the cochlea and that this is shown by the presence of abnormal positive summating potentials on round window electrocochleography. The objectives were to establish the proportion of infants with hearing loss affected, the nature of the cochlear lesion, and its etiology. And to highlight the important implications for otoacoustic emissions testing and universal neonatal screening.

STUDY DESIGN

A prospectively conducted consecutive cohort study with supplemental review of notes was performed.

METHODS

Four hundred sixty-four children underwent round window electrocochleography and auditory brainstem response testing under general anesthesia to assess suspected hearing loss. The presence of abnormal positive potentials was recorded. Otoacoustic emissions data were collected separately and retrospectively.

RESULTS

Three hundred forty-two children had significant bilateral congenital hearing loss. All results were from hearing-impaired children. Abnormal positive potentials were recorded in 73 of 342 children (21%). Eighty-three percent of children with otoacoustic emissions also had abnormal positive potentials, but only 14% of children without otoacoustic emissions had abnormal positive potentials (P <.001). In the neonatal intensive care unit setting, 43% of infants were found to have abnormal positive potentials, whereas only 10% had abnormal positive potentials if not in the neonatal intensive care unit setting (P <.001). Abnormal positive potentials were present in 63% of infants born before 30 weeks gestation and in 14% of infants born at term (P <.001). Abnormal positive potentials were identified in 57% of infants with documented hypoxia and 11% of children with no episodes (P <.001). Otoacoustic emissions were present in 48% of infants from the neonatal intensive care unit, despite their hearing loss.

CONCLUSION

Both otoacoustic emissions and abnormal positive potentials may originate from outer hair cell activity following inner hair cell loss. This may occur in more than 40% of hearing-impaired children in the neonatal intensive care unit setting. Chronic hypoxia is the most likely cause. Otoacoustic emissions testing may not be a suitable screening tool for such infants.

Transient evoked otoacoustic emissions in superior canal dehiscence syndrome

Superior semicircular canal dehiscence syndrome (SCDS) is a clinical disorder that is characterized by vertigo and oscillopsia induced by loud sounds. Transient evoked otoacoustic emissions (TEOAEs) allow to noninvasively check the integrity of the cochlea. The present study aimed at identifying cochlear stress as the result of micro alterations of the cochlear functionality due to anatomic anomaly. 11 SCDS and 10 normal individuals as control group were submitted to history taking, otological examination, basic audiologic evaluation and TEOAEs analysis using the standard wideband protocol and moving time window analysis. Although TEOAEs test results showed no statistically significant difference using the standard protocol, off-line analysis of the waveforms' "effective duration" was statistically significantly shortened (p < 0.0001) when compared to normal ears. In conclusion, dehiscence of bone overlying the superior canal has been shown to have effects on inner ear function in terms of a third mobile window theory, thus altering pressure across cochlear partition with decrease in inner ear impedance.

Temporary reduction of distortion product otoacoustic emissions (DPOAEs) immediately following auditory brainstem response (ABR)

The hearing status of an experimental animal is typically assessed in the laboratory setting by the combined use of auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs), carried out in succession, with the former assay preceding the latter. This study reports a cautionary finding that the use of this accepted regimen yields a reduced DPOAE response. When the DPOAEs were performed after ABR testing, transient reduction of the DPOAE amplitudes was observed at all frequencies in both the inbred, C57/B6 and FVB/N, and the outbred, SW mouse strains. DPOAEs were reduced post-ABR in multiple mouse strains which suggests that this finding is not strain-specific but a general consequence of the preceding ABR analysis. The reduction in DPOAE was temporary: when re-tested at one hour, DPOAE amplitudes recovered to pre-ABR levels. In contrast to the ABR's impact on DPOAE response, ABR thresholds were not altered or reduced when preceded immediately by DPOAE measurements. The molecular alterations underlying the ABR-induced transient reduction of DPOAE remain to be determined. To investigate the potential role of reactive oxygen species in post-ABR DPOAE reduction, transgenic mice over-expressing SOD1, the cytoplasmic enzyme critical for removal of superoxide radicals were subjected to the same auditory testing regimen. Similar to their wild type littermates, the SOD1 transgenic mice also demonstrated post-ABR DPOAE reduction, and thus do not support a role for superoxide radicals in transient reduction of DPOAE. While toxic noise exposure is known to negatively impact OAE, transient decrease in DPOAE levels following standard ABR assay has not been previously described. A practical outcome from this study is a recommendation for reversal of the traditional order for carrying out auditory tests, with the OAE measurements preceding ABR assessment, thus ensuring that the DPOAE response is unaffected.

Impedance audiometry in infants with a cleft palate: the standard 226-Hz probe tone has no predictive value for the middle ear condition

OBJECTIVE

Infants with a cleft palate and microscopical evidence for middle ear effusion attracted our attention because of normal tympanometry results and negative otoacoustic emissions. These contradictory findings initiated us to study to what extent high frequency tampynometry is able to supply us with more reliable results.

METHODS

Eighty-three ears of 46 cleft palate babies aged between 2 and 7 months were examined within the pedaudiological screening procedure via tympanometry before their surgical cleft closure. We applied probe tone frequencies of 226 Hz and 678 Hz. A control cohort of 69 ears of 36 babies without cleft palate was established. Results were later compared to the intraoperative findings.

RESULTS

By tympanometry with a 226-Hz probe tone, the examiners predicted the intraoperative findings correctly in only 29 cases of 83 examined ears (34.9%). However, their interpretation of tympanometry results by means of a 678-Hz probe tone correlated to the intraoperative findings in 96.3% cases.

CONCLUSIONS

In cleft palate babies tympanometry with a 678-Hz probe tone yields clear evidence of middle ear effusion and should therefore serve as an essential instrument before the first surgical step of palate closure. In case of applying the 226-Hz probe tone, we were often confronted with normal function of the Eustachian tube despite of proved existence of middle ear effusion.

[Value of otoacoustic emission tests in the diagnosis and follow-up of the otitis media with effusion]

OBJECTIVES

This study aimed to determine the value of otoacoustic emission tests in the diagnosis and treatment of the otitis media with effusion.

PATIENTS AND METHODS

Seventy-eight ears of 39 patients (24 males, 15 females; mean age 7.84 years; range 4 to 14 years) operated on because of serous otitis media with effusion and adenoid hypertrophy between September 2006 and May 2007 were included in the study. The medical history, otoscopic examination and audiologic tests were used in diagnosis. Otoacoustic emission tests (DPOAE and TEOAE), pure tone audiometry and tympanometry were also applied in the pre- and postoperative first month. Myringotomy and ventilation tube insertion was performed on patients with type B tympanograms.

RESULTS

In patients with type B tympanograms, pre- and postoperative audiogram values compared with pre-treatment air and bone gap values significantly decreased (p<0.01). After treatment DPOAE and TEOAE positivity compared to pretreatment values significantly increased (p<0.001). The presence of middle ear effusion affects otoacoustic emissions.

CONCLUSION

The results of this study revealed that the measurement of otoacoustic emissions may be helpful in evaluating the condition of the middle ear during the treatment. Otoacoustic emissions are easy, practical tests for the follow-up of effusional otitis media during the pre- and postoperative period. Otoacoustic emissions may give valuable information for applying ventilation tubes and help avoid unnecessary myringotomy.

Newborn hearing screening: a regional example for national care

Congenital Permanent Childhood Hearing Impairment (PCHI) is known to have a negative effect on language acquisition, cognitive development and social integration. Since 2000 our department has implemented a UNHS program in the West of Ireland. We describe our experience and detail our results to date. All neonates born from October 2000 to November 2007 were screened using a 2-stage protocol. Transient evoked oto-acoustic emissions (TEOAEs) were used to screen all neonates, followed by automated auditory brainstem response (AABR) in those who did not pass TEOAE, and all neonates at audiological risk. 26,281 babies were born over the eight year period. 25,742 underwent the screening process, achieving a coverage rate of 98%. The prevalence of PCHI in the population tested was 1.21/1000 live births (31/25,731). Our results show that a hospital based 2-stage UNHS protocol using TEOAEs and AABR is accurate, feasible and effective.

Measurement of conductive hearing loss in mice

In order to discriminate conductive hearing loss from sensorineural impairment, quantitative measurements were used to evaluate the effect of artificial conductive pathology on distortion-product otoacoustic emissions (DPOAEs), auditory brainstem responses (ABRs) and laser-Doppler vibrometry (LDV) in mice. The conductive manipulations were created by perforating the pars flaccida of the tympanic membrane, filling or partially filling the middle-ear cavity with saline, fixing the ossicular chain, and interrupting the incudo-stapedial joint. In the saline-filled and ossicular-fixation groups, averaged DPOAE thresholds increased relative to the control state by 20-36 and 25-39 dB, respectively with the largest threshold shifts occurring at frequencies less than 20kHz, while averaged ABR thresholds increased 12-19 and 12-25 dB, respectively without the predominant low-frequency effect. Both DPOAE and ABR thresholds were elevated by less than 10 dB in the half-filled saline condition; no significant change was observed after pars flaccida perforation. Conductive pathology generally produced a change in DPOAE threshold in dB that was 1.5-2.5 times larger than the ABR threshold change at frequencies less than 30 kHz; the changes in the two thresholds were nearly equal at the highest frequencies. While mild conductive pathology (ABR threshold shifts of <10 dB) produced parallel shifts in DPOAE growth with level functions, manipulations that produced larger conductive hearing losses (ABR threshold shifts >10 dB) were associated with significant deceases in DPOAE growth rate. Our LDV measurements are consistent with others and suggest that measurements of umbo velocity are not an accurate indicator of conductive hearing loss produced by ossicular lesions in mice.

Local cochlear damage reduces local nonlinearity and decreases generator-type cochlear emissions while increasing reflector-type emissions

Distortion product otoacoustic emissions (DPOAEs) originate in cochlear nonlinearity and emerge into the ear canal as an apparent sum of emission types, one of which (generator) travels directly out and the other (reflector) travels out following linear reflection. The present study explores intracochlear sources of DPOAEs via simultaneous ear canal and intracochlear pressure measurements in gerbils. A locally damaged cochlea was produced with reduced local intracochlear nonlinearity and significant elevation of the compound action potential thresholds at frequencies represented within the damaged region. In the DPOAE the comparison of healthy to locally damaged cochleae showed the following: (1) In the broad frequency region corresponding to the locally damaged best frequency, DPOAEs evoked by wider f(2)/f(1) stimuli decreased, consistent with the reduction in local nonlinearity. (2) DPOAEs evoked by narrow f(2)/f(1) stimuli often had a bimodal change, decreasing in a lower frequency band and increasing in a band just adjacent and higher, and the DPOAE phase-vs-frequency slope steepened. These changes confirm the complex nature of the DPOAE.

[Comparison of transient evoked otoacoustic emissions in newborns and adults with frequency specific approach]

OBJECTIVE

To investigate the difference of transient evoked otoacoustic emissions (TEOAE) between neonates and adults with the frequency-specific approach.

METHODS

TEOAE were recorded from 112 newborns (62 females, 58 males) who passed hearing screening, and 32 adults (17 females, 15 males) tested with pure-tone threshold equal or less than 20 dBHL. Band reproducibility, signal-to-noise rate (SNR) of frequency-band and half-octave frequency analysis of TEOAE amplitude was recorded respectively.

RESULTS

Significant differences were found in two groups, the higher entire TEOAE level found in newborn [(15.18 +/- 4.39) dB SPL] was higher than that of adults group [(9.51 +/- 4.12) dB SPL, P < 0.05]. The lowest wave reproducibility and SNR were in first frequency band (0.8 kHz) for neonate, and then, in last frequency band (4.0 kHz) were for young adults. For newborns, the highest band reproducibility and SNR were presented at fourth frequency band (3.2 kHz). However, for adults, the highest band reproducibility and SNR were presented at second frequency band (1.5 kHz). Frequency space of the SNR response peaks between neonates and adults was 1.7 kHz. The level difference was 7.09 dB SPL. Half octave frequency analysis shows a TEOAE response peaks in neonates was (10.50 +/- 5.09) dB SPL at the 2828 Hz, and in adults, it was (2.84 +/- 5.33) dB SPL at the 1414 Hz. Frequency space of the TEOAE response peaks between neonates and adults was 1414 Hz. Level differences of TEOAE response peaks was 7.66 dB SPL. TEOAE response peak in adult appear at 1.5 kHz, and then dropped down correlated to increase of frequency. From the first to the last testing frequency band, the difference of TEOAE level between neonate and adult was found to increase correlated to increase of frequency.

CONCLUSIONS

TEOAE response level in newborn is higher than that in adult group. Further, the decrease of TEOAE response level presented more sharpens with the frequency increasing in adult. The frequency of TEOAE response peak in neonate (3.2 kHz) is higher than adult (1.5 kHz). The level of TEOAE response peak is also greater than adult.

Audiologic disturbances in long-term mobile phone users

INTRODUCTION

There is general concern regarding the possible hazardous health effects of exposure to radiofrequency electromagnetic radiation emitted from mobile phones. This study aimed to assess the effects of chronic exposure to electromagnetic waves emitted from Global System for Mobile Communication (GSM) mobile phones on auditory functions.

MATERIAL AND METHODS

A retrospective, cross-sectional, randomized, case control study was carried out in a tertiary care hospital. One hundred twelve subjects who were long-term mobile phone users (more than 1 year) and 50 controls who had never used a mobile phone underwent a battery of audiologic investigations including pure-tone audiometry (both speech and high frequency), tympanometry, distortion product otoacoustic emissions, auditory brain responses, and middle latency responses. Changes in the various parameters were studied in the mobile phone- and non-mobile phone-using ears of subjects and corresponding ears of the controls to ascertain the effects of electromagnetic exposure.

RESULTS

There was no significant difference between users and controls for any of the audiologic parameters. However, trends for audiologic abnormalities were seen within the users. High-frequency loss and absent distortion product otoacoustic emissions were observed with an increase in the duration of mobile phone use, excessive use of mobile phones, and age more than 30 years. Additionally, users with some complaints during mobile phone use demonstrated absent distortion product otoacoustic emissions and abnormalities in auditory brainstem response.

CONCLUSION

Long-term and intensive mobile phone use may cause inner ear damage. A large sample size would be required to reach definitive conclusions.

[Alzheimer's disease and hearing loss]

INTRODUCTION

Despite the different epidemiological, neurophysiological and morphological studies published in the literature, it is still not known for sure whether there is a relation between Alzheimer's disease (AD) and peripheral hearing loss. In this work we conduct an auditory study in patients with AD and in volunteer controls in order to investigate this possible relationship.

SUBJECTS AND METHODS

The sample studied consisted of 14 patients with a clinical diagnosis of probable AD (age: 79 Y 6 years) and 14 volunteers (age: 76 Y 5 years) who visited the Clinica Universidad de Navarra. After applying a set of thorough criteria to preclude any previous hearing problems, all the participants underwent a subjective hearing assessment by means of pure-tone threshold audiometry and vocal audiometry and an objective auditory assessment using a tympanometry study, stapedial reflex, otoacoustic emissions and brainstem auditory evoked potentials. For the analysis, patients with AD and controls were paired homogenously by sex and age.

RESULTS

The main obstacle hindering the study was to recruit the participants, due to the fact that they did not see any direct benefit from the study and it demanded an excessive amount of their time. Pure-tone threshold audiometry showed that patients with AD had a pattern of greater hearing loss for acute frequencies, with statistically significant differences. No significant differences were found in the analysis of the rest of the subjective and objective hearing tests.

CONCLUSIONS

The findings of our study both agree and disagree with some earlier works from the literature, which suggests that patients with AD may have their own auditory pattern.

Distortion product otoacoustic emission phase and component analysis in human newborns

Apical distortion product otoacoustic emissions (DPOAEs) are comprised of at least two components, as evidenced by the interference pattern of alternating maxima and minima known as fine structure. DPOAE fine structure is produced by the shifting phase relationship in the ear canal, between the generator and characteristic frequency (CF) component of the response. Each component arises from a different cochlear region and, according to theory, reflects a distinct generation mechanism. The analysis of DPOAE components and phase in newborns may provide a window into targeted aspects of cochlear physiology during development. 2f(1)-f(2) DPOAE fine structure was recorded from 15 adults and 14 newborns using a swept-tone technique. DPOAE group delay, as well as magnitude and phase of each component, was compared between age groups. Results show narrower fine structure spacing, a longer group delay (steeper phase gradient) in low frequencies, and a stronger relative contribution from the CF component in newborns. The prolonged group delay for low-frequency DPOAEs could indicate immature basilar membrane motion in the apex of the cochlea and warrants further investigation. The enhanced contribution from the CF component may have implications for clinical practice as well as for theories of cochlear maturation.

Detection of dead regions in the cochlea: relevance for combined electric and acoustic stimulation

A dead region is a region in the cochlea where the inner hair cells and/or the auditory neurones are functioning very poorly, if at all. People who are being considered for a combination of a cochlear implant and a hearing aid typically have a dead region in the parts of the cochlea that normally respond to medium and high frequencies, but have some functional hearing at lower frequencies. For such people, it may be useful to determine the edge frequency, f(e), of any dead region. This may be relevant to choosing the most appropriate insertion depth of the electrode array, and to the way that frequencies in the input signal are mapped to acoustic and electric stimulation. It may also be helpful in interpreting the results of research studies. This paper reviews methods for diagnosing dead regions and defining the value of f(e). It is argued that the value of f(e) cannot be determined reliably from the audiogram, although a dead region is likely to be present at a given frequency when the hearing loss at that frequency is 70 dB or more. When a sinusoidal signal is reported as sounding highly distorted or noise-like, a dead region may be present at the signal frequency, but again this is not a reliable indicator. The TEN test is a simple clinical method for diagnosis of dead regions. Where this test gives a positive diagnosis, it is recommended that psychophysical tuning curves be measured to define the value of f(e) more precisely.

The monitoring role of otoacoustic emissions and oxidative stress markers in the protective effects of antioxidant administration in noise-exposed subjects: a pilot study

BACKGROUND

Oxidative stress has been recently identified as the pivotal pathway of cochlear damage. The aims of this study were to evaluate whether distortion product otoacoustic emissions (DPOAEs) can discriminate normal subjects with a risk of damage induced by sound exposure, the effectiveness of OAEs in monitoring the protective effects of Coenzyme Q10 terclatrate (QTer), and the role of blood parameters in monitoring preventive therapies.

MATERIAL/METHODS

Twenty volunteers were randomized to two groups: the first (n=10) was treated with Q-Ter (200 mg orally once daily) for 7 days before noise exposure and the second group was treated with placebo using the same schedule. All participants were exposed to white noise of 90 dB HL for 15 minutes. DPOAEs and pure-tone audiometry (PTA) were measured before and 1 h, 16 h, and 7 and 21 days after exposure. Inflammatory and oxidative stress parameters were measured before and 2 and 24 h after exposure.

RESULTS

In the placebo group, DPOAE amplitudes were reduced 1 and 16 h after exposure compared with the baseline values (p<0.05). In the Q-Ter group, DPOAEs did not show any significant difference between baseline and post-exposure (p>0.1). PTA threshold values in the Q-Ter and placebo groups did not differ before and after exposure. No significantly different levels of the inflammatory markers were observed in the Q-Ter and placebo groups at the different time points.

CONCLUSIONS

This pilot study confirms that DPOAEs represent a sensitive test for monitoring the effects of noise in preclinical conditions and pharmacological treatment.