Interaural Differences Research Articles

The effect of cochlear implants on vestibular-evoked myogenic potential responses in adults

Background Cochlear implants (CIs) as a golden solution for improving hearing for patients with profound hearing loss may although causes damage for peripheral vestibular system during insertion of electrode interpretatively leading to vestibular dysfunction. This can be assessed by several methods. One of the important methods is cervical vestibular evoked myogenic potential (cVEMP) which can assess the function of saccule. Aim of the work Study the effect of insertion of electrodes of CIs on the saccular function, by using cVEMP test which was performed before and after the operation. Also, cVEMP was measured in the CI-on and CI-off modes to determine if electrical stimulation of electrodes of CIs affects the saccular function or not. Materials and method Thirty adult CI candidates were recruited from the audiology unit of Hearing and Speech Institute. cVEMP was recorded preoperatively for each candidate and two months post operative. cVEMP testing was performed in the CI-on and CI-off modes. Results cVEMP response was recorded postoperatively for 19 out of 30 (63%) implanted ears. The amplitude of wave P and wave N in implanted ears with CI-off mode was decreased compared to preoperative results and this decrease is statistically significant. Also, amplitude of wave P and wave N in implanted ears with CI-on mode were increased compared to preoperative results and this increase is statistically significant. The interaural amplitude difference (IAD) ratio in postoperative CI-on mode was decreased compared to preoperative results and this decrease is not statistically significant. Conclusion cVEMP should be included in cochlear implant selection protocol with caloric testing as it is more sensitive for discovering vestibular disorders. Also, postoperative cVEMP testing in the CI-on and CI-off modes will offer accurate evaluation of saccule function after CI surgery.

A sex difference and learning in the discrimination of interaural-level differences but not interaural-time differences in naïve listeners

The two primary cues to sound-source location on the horizontal plane are interaural differences in time (ITDs) and in level (ILDs). Here, we asked whether the ability to discriminate small changes in each of these interaural cues differs between the sexes. We tested males and females who had no prior experience with any psychoacoustic task on either ILD discrimination at 4 kHz or ITD discrimination at 0.5 kHz. For ILD discrimination, the overall mean threshold, as well as the threshold for each 50-trial block, was significantly lower for males (n = 80) than for females (n = 166). Both males and females learned over the course of testing, but there was no sex difference in learning rate. In contrast, for ITD discrimination, thresholds did not differ significantly between the sexes for the overall mean or for any block (n = 43M/94F). There also was no learning across blocks for either group. For both tasks, the individual thresholds spanned a wide range in each group. The presence of sex differences and learning for ILD but not ITD discrimination suggests that the factors responsible for these outcomes influenced a relatively peripheral ILD-specific pathway, and not an ITD-specific pathway, or a more central locus that is not cue specific.

The effect of target and interferer frequency on across-frequency binaural interference of interaural-level-difference sensitivity.

Across-frequency binaural interference occurs when the sensitivity to changes in interaural differences in a target sound is decreased by a spectrally remote diotic interfering sound. For interaural time differences (ITDs), low-frequency (e.g., 0.5 kHz) interferers cause more interference on high-frequency (e.g., 4 kHz) targets than vice versa. For interaural level differences (ILDs), however, it is unclear if a frequency dependence exists. Therefore, ILD discrimination thresholds and across-frequency binaural interference were measured for target and interferer frequencies between 0.5 and 8 kHz (for tones) or 12 kHz (for narrowband noises). For tones, 8-kHz targets experienced the least interference and 8-kHz interferers produced the most interference, suggesting that higher-frequency ILDs are a more heavily weighted localization cue than lower-frequency ILDs. For narrowband noises, the frequency-dependent interference patterns increased in complexity in comparison to tones. Low-frequency ITD dominance (from randomly varying onset ITDs) and grouping cues (e.g., envelope modulations) might explain some of the complexity in the interference patterns for the noises. These data contribute to a better understanding of across-frequency ILD processing, which remains poorly understood.

Clinical correlates of different forms of endolymphatic hydrops

BackgroundThe aim of this study is to explore the different kinds of endolymphatic hydrops and the sensitivity of vestibular evoked myogenic potentials (VEMP) and electrocochleography in their diagnosis. Three groups of patients were selected according to the diagnosis, definitive MD (DMD), cochlear MD (CMD), and recurrent vestibulopathy (RV) groups. A basic audiological evaluation was carried out. It included pure tone audiometry, speech audiometry, acoustic immittancemetry testing and electrocochleography, cervical VEMP (c-VEMP), and ocular VEMP (o-VEMP).ResultsThe overall sample was 40 cases, 13 with DMD, 10 with CMD, and 17 with RV. The mean age is variable between groups (p-value < 0.001) with the highest in the DMD group (38.3 ± 7.4 years) and the lowest in the CMD group (25.2 ± 4.6 years). The male to female ratio is variable between groups of the study (p-value = 0.03) with the highest ratio 9:4 in the DMD group. There was a significant difference between groups (p < 0.001) regarding dizziness. Asymmetric response of c-VEMP was seen in nine (69.2%) of DMD cases, in 14 (82.4%) of RV cases, and only in three (30%) of CMD cases (p-value < 0.001). Low amplitude of o-VEMP was seen in 11 (84.6%) of DMD cases, 9 (90%) of CMD cases, 15 (88.2%) of RV cases, and only two (25%) of normal cases (p-value = 0.002). A significant difference was found between definitive and cochlear Meniere’s as regards o-VEMP inter-aural amplitude difference (IAD) (p-value = 0.032) only. There was a significant positive strong correlation between age and EcochG SP/AP ratio left ear, o-VEMP IAD, and o-VEMP left ear n1. In addition, there is a significant positive weak correlation between duration and EcochG SP/AP ratio left ear and c-VEMP left ear n1.ConclusionsAsymmetric response of c-VEMP can be used as a diagnostic tool to differentiate different kinds of MD: DMD, RV, and CMD.

Anatomical variation of inner ear may be a predisposing factor for unilateral M\xe9ni\xe8re\u2019s disease rather than for ipsilateral delayed endolymphatic hydrops

ObjectiveRadiological anatomical variations, measured by magnetic resonance imaging (MRI), were evaluated in patients with ipsilateral delayed endolymphatic hydrops (DEH) and unilateral Ménière’s disease (MD). The role of anatomical variations in different subtypes of hydropic ear disease was investigated.MethodsTwenty-eight patients with ipsilateral DEH, 76 patients with unilateral MD, and 59 control subjects were enrolled. The radiological indices included the distance between the vertical part of the posterior semicircular canal and the posterior fossa (MRI-PP distance) and the visibility of vestibular aqueduct (MRI-VA). These variations among patients with DEH, MD, and control subjects were compared. The correlation between radiological anatomical variations and clinical features or audio-vestibular findings was also examined.Results(1) MRI-PP distance in the affected side of unilateral MD was shorter than that in ipsilateral DEH (Z = − 2.481, p = 0.013) and control subjects (Z = − 2.983, p = 0.003), while the difference of MRI-PP distance between the affected side of ipsilateral DEH and control subjects was not statistically significant (Z = − 0.859, p = 0.391). (2) There was no significant interaural difference of MRI-PP distance in patients with unilateral MD (Z = − 0.041, p = 0.968) and ipsilateral DEH (t = − 0.107, p = 0.915) respectively. (3) No significant interaural difference of MRI-VA visibility was observed in patients with unilateral MD (χ2 = 0.742, p = 0.389) and ipsilateral DEH (χ2 = 0.327, p = 0.567) respectively. (4) No correlation was found between these anatomical variables and clinical features or audio-vestibular findings in patients with unilateral MD and ipsilateral DEH respectively (p > 0.05).ConclusionsAnatomical variations of inner ear may be a predisposing factor in the pathogenesis of unilateral MD rather than ipsilateral DEH.Key Points• Patients with ipsilateral delayed endolymphatic hydrops showed normal distance between the vertical part of the posterior semicircular canal and the posterior fossa.• Compared to patients with ipsilateral delayed endolymphatic hydrops and control subjects, patients with unilateral Ménière’s disease exhibited shorter distance between the vertical part of the posterior semicircular canal and the posterior fossa.• Anatomical variations of inner ear may be a predisposing factor in the pathogenesis of unilateral Ménière’s disease rather than ipsilateral delayed endolymphatic hydrops.

Assessing HRTF preprocessing methods for Ambisonics rendering through perceptual models

Binaural rendering of Ambisonics signals is a common way to reproduce spatial audio content. Processing Ambisonics signals at low spatial orders is desirable in order to reduce complexity, although it may degrade the perceived quality, in part due to the mismatch that occurs when a low-order Ambisonics signal is paired with a spatially dense head-related transfer function (HRTF). In order to alleviate this issue, the HRTF may be preprocessed so its spatial order is reduced. Several preprocessing methods have been proposed, but they have not been thoroughly compared yet. In this study, nine HRTF preprocessing methods were used to render anechoic binaural signals from Ambisonics representations of orders 1 to 44, and these were compared through perceptual hearing models in terms of localisation performance, externalisation and speech reception. This assessment was supported by numerical analyses of HRTF interpolation errors, interaural differences, perceptually-relevant spectral differences, and loudness stability. Models predicted that the binaural renderings’ accuracy increased with spatial order, as expected. A notable effect of the preprocessing method was observed: whereas all methods performed similarly at the highest spatial orders, some were considerably better at lower orders. A newly proposed method, BiMagLS, displayed the best performance overall and is recommended for the rendering of bilateral Ambisonics signals. The results, which were in line with previous literature, indirectly validate the perceptual models’ ability to predict listeners’ responses in a consistent and explicable manner.

Towards a simplified and generalized monaural and binaural auditory model for psychoacoustics and speech intelligibility

Auditory perception involves cues in the monaural auditory pathways, as well as binaural cues based on interaural differences. So far, auditory models have often focused on either monaural or binaural experiments in isolation. Although binaural models typically build upon stages of (existing) monaural models, only a few attempts have been made to extend a monaural model by a binaural stage using a unified decision stage for monaural and binaural cues. A typical prototype of binaural processing has been the classical equalization-cancelation mechanism, which either involves signal-adaptive delays and provides a single channel output, or can be implemented with tapped delays providing a high-dimensional multichannel output. This contribution extends the (monaural) generalized envelope power spectrum model by a non-adaptive binaural stage with only a few, fixed output channels. The binaural stage resembles features of physiologically motivated hemispheric binaural processing, as simplified signal-processing stages, yielding a 5-channel monaural and binaural matrix feature “decoder” (BMFD). The back end of the existing monaural model is applied to the BMFD output and calculates short-time envelope power and power features. The resulting model accounts for several published psychoacoustic and speech-intelligibility experiments and achieves a prediction performance comparable to existing state-of-the-art models with more complex binaural processing.

Binaural-cue Weighting and Training-Induced Reweighting Across Frequencies.

During sound lateralization, the information provided by interaural differences in time (ITD) and level (ILD) is weighted, with ITDs and ILDs dominating for low and high frequencies, respectively. For mid frequencies, the weighting between these binaural cues can be changed via training. The present study investigated whether binaural-cue weights change gradually with increasing frequency region, whether they can be changed in various frequency regions, and whether such binaural-cue reweighting generalizes to untrained frequencies. In two experiments, a total of 39 participants lateralized 500-ms, 1/3-octave-wide noise bursts containing various ITD/ILD combinations in a virtual audio-visual environment. Binaural-cue weights were measured before and after a 2-session training in which, depending on the group, either ITDs or ILDs were visually reinforced. In experiment 1, four frequency bands (centered at 1000, 1587, 2520, and 4000 Hz) and a multiband stimulus comprising all four bands were presented during weight measurements. During training, only the 1000-, 2520-, and 4000-Hz bands were presented. In experiment 2, the weight measurements only included the two mid-frequency bands, while the training only included the 1587-Hz band. ILD weights increased gradually from low- to high-frequency bands. When ILDs were reinforced during training, they increased for the 4000- (experiment 1) and 2520-Hz band (experiment 2). When ITDs were reinforced, ITD weights increased only for the 1587-Hz band (at specific azimuths). This suggests that ILD reweighting requires high, and ITD reweighting requires low frequencies without including frequency regions providing fine-structure ITD cues. The changes in binaural-cue weights were independent of the trained bands, suggesting some generalization of binaural-cue reweighting.

Masked Speech Recognition by Normal-Hearing 6-13-Year-Olds in Conditions With and Without Interaural Difference Cues.

Using the Danish 'børneDAT' corpus, the current study aimed to (1) collect normative masked speech recognition data for 6-13-year-olds in conditions with and without interaural difference cues, (2) evaluate the test-retest reliability of these measurements, and (3) compare two widely used measures of binaural/spatial benefit in terms of the obtained scores. Seventy-four children and 17 young adults with normal hearing participated. Using headphone presentation, speech recognition thresholds (SRTs) were measured twice at two separate visits in four conditions. In the first two conditions, børneDAT sentences were presented in diotic stationary speech-shaped noise, with the sentences either interaurally in-phase ('N0S0') or interaurally out-of-phase ('N0S180'). In the other two conditions, børneDAT sentences were simulated to come from 0° azimuth and two running speech maskers from either 0° azimuth ('co-located') or ±90° azimuth ('spatially separated'). In relative terms, the children achieved lower SRTs in stationary noise than in competing speech, whereas the adults showed the opposite pattern. 12-13-year-old children achieved adult-like performance in all but the co-located condition. Younger children showed generally immature speech recognition abilities. Test-retest reliability was highest for the SRTs in stationary noise and lowest for the spatial benefit scores. Mean benefit was comparable for the two measures and participant groups, and the two sets of scores were not correlated with each other. Developmental effects were most pronounced in the conditions with interaural difference cues. In conclusion, reference data for the børneDAT corpus obtained under different acoustic conditions are available that can guide future research and potential clinical applications.

Auditory brainstem response for Sri Lankan children under 5 years of age: Normativedata

For years Sri Lankan Audiologists resorted to western norms in the interpretation of Auditory Brainstem Response (ABR) in the absence of national standards. The study focused on establishing normative data on ABR for Sri Lankan children below 5 years. ABR was performed on 258 healthy children between 6 weeks and 5 years of age to gather data on absolute latencies and inter-peak latencies.All inter-aural differences were within 0.2-0.4ms. The mean inter-aural difference for the study sample was significantly small (-0.0204ms to 0.0286ms). Mean values of absolute latencies for waves I, III, V for the 6-week age group at 30dBnHL were 3.33 ms, 5.91 ms and 8.27 ms respectively. Mean values of inter-peak latencies of wave I-III, III-V, I-V were 2.08 ms, 2.36 ms and 4.76 ms respectively for the 6-week age group at 30 dBnHL. The normative ABR data obtained in this study may be used across audiology clinics in Sri Lanka as a baseline measurement to diagnose hearing loss among children from infancy to 5 years of age when children are tested in their natural sleep and insert earphones are used. The mean value plus 2 standard deviations for each ABR measure may be used as the upper limit cutoff values. Hence this study helps eliminate misdiagnosis and under-diagnosis of hearing loss in children.

Features of use of evoked potential method on children with epilepsy of pre- and puberty age-old period

This paper of the usage of the evoked potential method is studied, in patients with epilepsy. A brief description of the method is described. A pilot study of auditory long-latency and visual on the outbreak of evoked potential was carried out in 19 children with various forms of epilepsy, who are in long-term remission, and also with pharmacoresistant seizures. It was found that the visual evoked potentials are more indicative than auditory evoked potential. In most cases, a decrease in the amplitude and lengthening of evoked potentials latencies was revealed. Moreover, in the presence of focal changes, interocular or interaural differences were recorded. In that way, it is necessary to study the features of evoked potentials in children with epilepsy, study evoked potentials in the course of treatment in order to predict the course of the disease and the effectiveness of the therapy. The obtained data will serve as the basis for further research of the evoked potential method in children with epilepsy.

Progressive Asymmetry in Occupational Noise-Induced Hearing Loss: A Large Population-Based Cohort Study With a 15-Year Follow-Up.

Background: To evaluate interaural differences between the right and left ears at frequencies from 0.25 to 8 kHz in 3 groups of workers from metallurgy companies.Methods: This study is a cross-sectional cohort study. Workers were divided into 3 groups: (1) workers without occupational noise exposure and normal audiometric testing; (2) workers with 10 years of occupational noise exposure; and (3) workers with 15 years of occupational noise exposure. The interaural difference from 0.25 to 8 kHz was measured in each group.Results: A total of 2103 workers were included. Of these, 483 workers had been exposed to noise in the workplace for 10 years and 216 workers for 15 years. Group 1, only at 4 and 6 kHz, the difference was statistically significant. Group 2, only at 3 , 4 , and 6 kHz, the difference was statistically significant. Group 3, the difference was statistically significant at the frequencies from 2 to 8 kHz.Conclusion:Asymmetry between the right and left ears was observed in all groups, with higher air-conduction thresholds in the left ear. It is important for otolaryngologists be aware that NIHL can also cause or accentuate asymmetry between the right and left ears over time.

Diagnostic Validity of Auditory Brainstem Response for the Initial Screening of Vestibular Schwannoma.

Background and ObjectivesTo investigate the diagnostic validity of auditory brainstem response (ABR) in the screening of vestibular schwannoma (VS).Subjects and MethodsForty patients diagnosed with VS using magnetic resonance imaging who had undergone ABR before treatment between 2005 and 2015 were included. ABR results were considered positive when findings met at least one of the following criteria: 1) absent evoked response, 2) desynchronization of waves other than wave I, 3) interpeak latency (IPL) between waves I and III >2.5 ms, 4) IPL between waves I and V >4.4 ms, 5) wave V interaural latency difference >0.2 ms, and 6) interaural difference in IPL between waves I and V >0.2 ms.ResultsThe overall sensitivity of ABR was 85.0%. For tumors measuring <10 mm, the sensitivity of ABR was 66.7%, whereas it increased to 90.3% for tumors measuring >10 mm. The sensitivity of tumors confined to the internal acoustic canal was 73.3% compared with 100.0% for tumors confined to the cerebellopontine angle. In patients with serviceable hearing, the mean tumor size was 7.8±2.9 mm in patients with a normal ABR and 15.1±9.4 mm in patients with an abnormal ABR, indicating a significant difference (p<0.05).ConclusionsABR alone is insufficient for the screening of VS, bearing the risk of false-negative outcomes when examining small, intracanalicular tumors. However, ABR can be inexpensively applied for the screening of VS measuring >10 mm in patients with serviceable hearing, supporting the need for further active diagnostic and treatment modalities in clinical practice.

Influence of envelope fluctuation on the lateralization of interaurally delayed low-frequency stimuli.

Disregarding onset and offset effects, interaurally delaying a 500 Hz tone by 1.5 ms is identical to advancing it by 0.5 ms. When presented over headphones, humans indeed perceive such a tone lateralized toward the side of the nominal lag. Any stimulus other than a tone has more than one frequency component and is thus unambiguous. It has been shown that phase ambiguity can be resolved when increasing the stimulus bandwidth. This has mostly been attributed to the integration of information across frequencies. Additionally, interaural timing information conveyed in the stimulus envelope within a single frequency channel is a second possible cue that could help to resolve phase ambiguity. This study employs stimuli designed to differ in the amount of envelope fluctuation while retaining the same power spectral density as well as interaural differences. Any difference in lateralization must thus be a result of the difference in envelope. The results show that stimuli with strong envelope fluctuation require significantly smaller bandwidths to resolve phase ambiguity when compared to stimuli with weak envelope fluctuation. This suggests that within-channel information is an important cue used to resolve phase ambiguity.

Measurements and models for tone localization by moving listeners

Listeners were given the challenging task of localizing a steady-state sine tone in a moderately reverberant room. Listeners attempted to optimize performance by moving during the nine-second tone interval. To discover listener localization strategies, the experiment acquired complete records of listener head motion (Polhemus head tracker) and the signals in the ear canals (Etymotic probe tubes). Experiment data were used to test two models of sound localization by moving listeners: According to the “Relative Null" model, listeners search for nulls in relevant interaural differences and use the momentary nose orientations where these nulls occur as indicators of source azimuth. According to the “Inferred Azimuth" model, listeners acquire a continuous, long-term record of inferred source location based on momentary head orientation combined with corresponding interaural differences. Models include different cue weighting assumptions and are evaluated by their ability to predict listener responses. The Relative Null model proves to be more accurate, but sometimes fails to make a prediction. The Inferred Azimuth model always makes multiple predictions, and often leads to further insights. These models are the most straightforward of numerous possibilities. Alternatives that weight the time course of listener cues, should be considered.

Lateralization biases for narrowband stimuli in listeners with typical and symmetrical hearing thresholds

In listeners with normal audiometric thresholds, it is assumed that stimuli presented over headphones with zero interaural differences are perceived to be centered in the head. In this study, intracranial lateralization was measured by having ten young adults with normal and interaurally symmetric thresholds (within 5 dB) point to perceived sound locations along a visual reference scale. The stimuli were either tones or 50-Hz-bandwidth narrowband noises, at frequencies of 300, 400, 500, 600, and 700 Hz. A range of interaural time differences (ITDs) was applied while the interaural level difference was always zero. To diminish any transducer-based effects, the headphones were reset and reversed between each of ten blocks of trials. Lateralization curves for five of the ten listeners showed a substantial bias to one ear at a subset or all frequencies tested; the worst individual case demonstrated a perceived 60% lateralization bias (from the midline to the left ear) for a zero ITD. This result challenges a long-standing assumption held in binaural hearing and, while similar results have been observed previously, the basis of the phenomenon remains largely unexplored.

Intracranial lateralization bias observed in the presence of symmetrical hearing thresholds.

It is generally assumed that listeners with normal audiograms have relatively symmetric hearing, and more specifically that diotic stimuli (having zero interaural differences) are heard as centered in the head. While measuring intracranial lateralization with a visual pointing task for tones and 50-Hz-wide narrowband noises from 300 to 700 Hz, examples of systematic and large (>50% from midline to the ear) lateralization biases were found. In a group of ten listeners, five showed consistent lateralization bias to the right or left side at all or a subset of frequencies. Asymmetries in hearing, not apparent in audiometric thresholds, may explain these lateralization biases.

Normalización de los Potenciales Evocados Auditivos del Tronco Cerebral I: Resultados en una muestra de adultos normoyentes

Este artículo es el primero de una serie de estudios que tienen por objeto describir las características de los Potenciales Evocados Auditivos del Tronco Cerebral (PEATC) tanto en sujetos normoyentes como hipoacúsicos. En la interpretación de estos registros electrofisiológicos es necesario conocer los valores de normalidad de la latencia y amplitud de los principales componentes y su relación con la distintas intensidades así como los valores de los intervalos interondas y las posibles diferencias interaurales. Estos valores de normalidad varían en función de múltiples factores como el sexo, la edad, los parámetros de estimulación y de registro o las condiciones en las cuales se llevan a cabo los PEATC. En este primer trabajo se describen los valores de normalidad de latencia de los componentes de los PEATC utilizando para ello los parámetros de estimulación y de registro propios de nuestro laboratorio en una muestra de sujetos adultos normoyentes.

BERA as a screerning tool for evaluating cases of SNHL due to suspected retrocochlear pathology

Background: BERA is an objective study for assessing hearing loss on patients with inconsistent responses on pure tone audiogram. BERA is a non-invasive and the most cost-effective method for diagnosing retrocochlear lesion, not affected by sedation, anesthesia or age. Which helps to identify retrocochlear hearing loss. BERA is most accurate and sensitive for diagnosis of lesions in VIII nerve and auditory pathway in brainstem, especially in adults. Objectives: Screening tool for evaluating cases of sensorineural hearing loss due to suspected retrocochlear pathology. Objective test in cases of inconsistent response for pure tone audiometry. Role in evaluating brainstem lesions. Method and Aim: This is a cross sectional prospective cohortHospital based study, review of 50 patient subjected to BERA for SNHL in any age group referred to department of ENT Vijayanagara institute of medical sciences, Bellary. We aim to find Brainstem evoked response audiometry (BERA) andits applications in ENT. Result: In this study threshold and latency measures were obtained from 50 cases (100 ears) by brainstem evoked response audiometry. No restrictions were imposed on age, sex, degree of hearing loss, or audiometric configuration. The data was analyzed separately for pediatric age group (36 cases) and adults(16 cases). out of 36 pediatric cases screened 15 cases (41.7%) had normal hearing in 13 cases had profound hearing loss without any risk factors. 6 cases ( 16.7 %) hearing loss due meningitis. 2 cases (5.6%) hearing loss due to neonatal jaundice. In adult age group (14 cases) BERA was done to identify cases of retocochlear pathology and in cases of threshold estimation of hearing. Conclusion: BERA can be used to screen retrocochlear pathologies as seen in our study. Patients with hearing loss with tinnitus and giddiness screened and BERA performed had grossly degraded wave with identification of only wave I and absence of other waves and increased latencies and interaural difference in wave latencies suggests lesion in the auditory pathway. Depending on the absence of specific wave site of the lesion can also be made out. In our study 3 cases of retrocochlear pathology previously confirmed by MRI was taken and BERA was performed showing presence of only wave I and absence of remaining waves. BERA is screening test and should be confirmed by MRI.

Auditory brainstem response with click and CE-Chirp® Level Specific stimuli in hearing infants

IntroductionThe assessment of the integrity of the neural responses with ABR, aims to assist in the differential diagnosis of retrocochlear alterations. The gold standard stimulus for this assessment is Click. However, the CE-Chirp® Level Specific was developed to optimize the triggering of neural responses. Objectiveto compare neural responses obtained with CE-Chirp® LS stimulus to those obtained with Clicks at 70 dB nHL in hearing infants, in order to analyze advantages in using CE-Chirp® LS. MethodsEighteen infants with normal hearing were evaluated with Eclipse EP25 ABR System. Clicks and CE-Chirp® LS stimuli were presented using ER-3A insert earphones at 70 dB nHL, rate 45.1/s, and alternating polarity. A 30 Hz high-pass and 1500 Hz low-pass filter was applied, and ±40 μV artifact rejection level. Absolute latency of waves I, III and V and their interpeak intervals I-III, III-V and I–V were measured, as well as interaural difference for wave V and interpeak I–V, and wave V amplitude. ResultsAlthough 18 infants were included in the study, it was possible to collect data only in 30 ears for Click stimulus, and 33 ears for CE-Chirp® LS, according to exclusion criteria. It was possible to record waves I, III, and V for both stimuli at 70 dB nHL in all normal-hearing infants. CE-Chirp® LS stimulus evoked a higher wave V amplitude than Click (p < 0.001). Wave I absolute latency was statistically different between stimuli (p < 0.001), being delayed for CE-Chirp® LS. Wave III absolute latency was statistically different between stimuli only for the right ear (p = 0.021), and wave V absolute latency was similar in both stimuli (p = 0.210). Interpeak intervals I-III and I–V were statistically different between stimuli (p < 0.001), being reduced for CE-Chirp® LS. Interpeak interval III-V was different between the stimuli only for right ears (p = 0.006). There was no difference between stimuli for interaural difference wave V (p = 1.33) and interaural difference interpeak I–V (p = 0.409). ConclusionIt is possible to use CE-Chirp® LS stimulus in order to analyze neural synchrony in infants at 70 dB nHL, since better morphology waveforms were observed, and higher wave V amplitudes could be recorded. We suggest that new studies with infants with neurological disabilities and various hearing status, to observe how CE-Chirp® LS stimulus evokes neural responses in these conditions.