Brain Signatures of Early and Late Neural Measures of Auditory Habituation and Discrimination in Autism and Their Relationship to Autistic Traits and Sensory Overresponsivity.

Sensory differences are included in the DSM-5 criteria of autism for the first time, yet it is unclear how they relate to neural indicators of perception. We studied early brain signatures of perception and examined their relationship to sensory behaviors and autistic traits. Thirteen autistic children and 13 Typically Developing (TD) children matched on age and nonverbal IQ participated in a passive oddball task, during which P1 habituation and P1 and MMN discrimination were evoked by pure tones. Autistic children had less neural habituation than the TD comparison group, and the MMN, but not P1, mapped on to sensory overresponsivity. Findings highlight the significance of temporal and contextual factors in neural information processing as it relates to autistic traits and sensory behaviors.

A Preliminary Study Characterizing Subcortical and Cortical Auditory Processing and Their Relation to Autistic Traits and Sensory Features.

This study characterizes the subcortical auditory brainstem response (speech-ABR) and cortical auditory processing (P1 and Mismatch Negativity; MMN) to speech sounds and their relationship to autistic traits and sensory features within the same group of autistic children (n = 10) matched on age and non-verbal IQ to their typically developing (TD) peers (n = 21). No speech-ABR differences were noted, but autistic individuals had larger P1 and faster MMN responses. Correlations revealed that larger P1 amplitudes and MMN responses were associated with greater autistic traits and more sensory features. These findings highlight the complexity of the auditory system and its relationships to behaviours in autism, while also emphasizing the importance of measurement and developmental matching.

Joint Profile Characteristics of Long-Latency Transient Evoked and Distortion Otoacoustic Emissions.

PURPOSE: In clinical practice, otoacoustic emissions (OAEs) are interpreted as either "present" or "absent." However, OAEs have the potential to inform about etiology and severity of hearing loss if analyzed in other dimensions. A proposed method uses the nonlinear component of the distortion product OAEs together with stimulus frequency OAEs to construct a joint reflection-distortion profile. The objective of the current study is to determine if joint reflection-distortion profiles can be created using long-latency (LL) components of transient evoked OAEs (TEOAEs) as the reflection-type emission. METHOD: LL TEOAEs and the nonlinear distortion OAEs were measured from adult ears. Individual input-output (I/O) functions were created, and OAE level was normalized by dividing by the stimulus level yielding individual gain functions. Peak strength, compression threshold, and OAE level at compression threshold were derived from individual gain functions to create joint reflection-distortion profiles. RESULTS: TEOAEs with a poststimulus window starting at 6 ms had I/O functions with compression characteristics similar to LL TEOAE components. The model fit the LL gain functions, which had R 2 > .93, significantly better than the nonlinear distortion OAE gain functions, which had R 2 = .596-.99. Interquartile ranges for joint reflection-distortion profiles were larger for compression threshold and OAE level at compression threshold but smaller for peak strength than those previously published. CONCLUSIONS: The gain function fits LL TEOAEs well. Joint reflection-distortion profiles are a promising method that could enhance diagnosis of hearing loss, and use of the LL TEOAE in the profile for peak strength may be important because of narrow interquartile ranges. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.20323593.

Relationships between click auditory brainstem response and speech frequency following response with development in infants born preterm.

The speech evoked frequency following response (sFFR) is used to study relationships between neural processing and functional aspects of speech and language that are not captured by click or toneburst evoked auditory brainstem responses (ABR). The sFFR is delayed, deviant, or weak in school age children having a variety of disorders, including autism, dyslexia, reading and language disorders, in relation to their typically developing peers. Much less is known about the developmental characteristics of sFFR, especially in preterm infants, who are at risk of having language delays. In term neonates, phase locking and spectral representation of the fundamental frequency is developed in the early days of life. Spectral representation of higher harmonics and latencies associated with transient portions of the stimulus are still developing in term infants through at least 10 months of age. The goal of this research was to determine whether sFFR could be measured in preterm infants and to characterize its developmental trajectory in the time and frequency domain. Click ABR and sFFR were measured in 28 preterm infants at ages 33 to 64 weeks gestational age. The sFFR could be measured in the majority of infants at 33 weeks gestational age, and the detectability of all sFFR waves was 100% by 64 weeks gestational age. The latency of all waves associated with the transient portion of the response (waves V, A, and O), and most waves (waves D and E) associated with the quasi-steady state decreased with increasing age. The interpeak wave A-O latency did not change with age, indicating that these waves share a neural generator, or the neural generators are developing at the same rate. The spectral amplitude of F0 and the lower frequencies of the first formant increased with age, but that for higher frequencies of the first formant and higher harmonics did not. The results suggest that the sFFR can be reliably recorded in preterm infants, including those cared for in the neonatal intensive care unit. These findings support that in preterm infants, F0 amplitude continues to develop within the first 6 months of life and develops before efficient representation of higher frequency harmonics. Further research is needed to determine if the sFFR in preterm infants is predictive of long-term language or learning disorders.

Refining Measurements of Power Absorbance in Newborns: Probe Fit and Intrasubject Variability.

OBJECTIVES: Because unresolved debris in the ear canal or middle ear of newborns may produce high false positive rates on hearing screening tests, it has been suggested that an outer/middle ear measure can be included at the time of hearing screening. A potential measure is power absorbance (absorbance), which indicates the proportion of power in a broadband acoustic stimulus that is absorbed through the outer/middle ear. Although absorbance is sensitive to outer/middle dysfunction at birth, there is large variability that limits its accuracy. Acoustic leaks caused by poor probe fitting further exacerbate this issue. The objectives of this work were to: (1) develop criteria to indicate whether a change in absorbance occurs in association with probe fit; (2) describe the variability in absorbance due to poor fitting; and (3) evaluate test-retest variability with probe reinsertions, excluding poor fits. DESIGN: An observational cross-sectional design was used to evaluate changes in absorbance due to probe fit and probe reinsertion. Repeated measurements were recorded in 50 newborns (98 ears) who passed TEOAE screenings and were <48 hours of age. One absorbance measurement was chosen as the baseline that served as a best-fit reference in each ear. Changes in absorbance, called absorbance probe-fit Δ, were calculated relative to the baseline in each ear. Correlations were assessed between the absorbance probe-fit Δ and low-frequency absorbance, impedance magnitude, impedance phase, and equivalent volume, to determine which measures predicted poor fits. Criteria were derived from the strongest of these correlations and their performance was analyzed. Next, measurements with poor/leaky fits were identified, and the changes in absorbance that they introduced were analyzed. Excluding the poor fits, test-retest differences in absorbance, called reinsertion Δ, were determined. Variability was assessed using the SDs associated with absorbance, absorbance probe-fit Δ, and reinsertion Δ. RESULTS: Based on the analysis of 12 moderate-strong correlations, the following criteria were adopted to identify measurements with poor fits: (1) impedance phase-based criterion (500 to 1000 Hz) > -0.11 cycles and (2) absorbance-based criterion (250 to 1000 Hz) > 0.58. Poor-fit measurements introduced statistically significant increases in absorbance up to 0.1 for 1000 to 6000 Hz, and up to 0.4 for frequencies <1000 Hz. Reinsertion Δ were ≤0.02, and were significant for 500 to 5000 Hz. The SDs of absorbance probe-fit Δ were greatest and similar to overall absorbance SD in the low frequencies. Separately, the SDs of reinsertion Δ were also greatest and similar to low-frequency absorbance SD. CONCLUSIONS: Poor probe fits introduced the greatest inflation in absorbance for frequencies < 500 Hz, and a smaller but significant inflation for higher frequencies, consistent with controlled experiments on acoustic leaks in adults. Importantly, inflation of absorbance in diagnostically sensitive 1000 to 2000 Hz may impact its clinical performance. Test-retest with probe reinsertion contributed significantly to absorbance variability, especially in the low frequencies, consistent with reports in adults, even though changes were smaller than those associated with poor probe fit. The results indicate that variability in absorbance was reduced by minimizing acoustic leaks. Pending further validation, the probe-fit criteria developed in this work can be recommended to ensure proper probe fit.

Observations of Distortion Product Otoacoustic Emission Components in Adults With Hearing Loss.

OBJECTIVES: Distortion product otoacoustic emissions (DPOAEs) measured in the ear canal are composed of OAEs generated by at least two mechanisms coming from different places in the cochlea. Otoacoustic emission (OAE) models hypothesize that reduction of cochlear gain will differentially impact the components. The purpose of the current experiment was to provide preliminary data about DPOAE components in adults with hearing loss in relation to OAE models and explore whether evaluation of the relative amplitudes of generator and reflection components can enhance identification of hearing loss. DESIGN: DPOAEs were measured from 45 adult ears; 21 had normal hearing (≤15 dB HL) and 24 with mild-to-severe sensorineural hearing loss (>15 dB HL). The higher frequency primary (f2) was swept logarithmically between 1500 and 6000 Hz, and f2/f1 was 1.22. The two equal-level primaries varied from 55 to 75 dB SPL in 5 dB steps. The swept primary procedure permitted the measurement of the amplitude and phase of the DPOAE fine structure and the extraction of the two major components (generator and reflection) by varying the predicted delays of the analysis windows. RESULTS: DPOAE fine structure was reduced or absent in ears with hearing loss. DPOAE generator and reflection components were lower in ears with hearing loss than those with normal hearing, especially for the reflection component. Significant correlations were found between the generator component and hearing threshold but not between reflection levels and hearing threshold. Most ears with normal hearing had both components, but only a small number of ears with hearing loss had both components. CONCLUSIONS: The reflection component is not recordable or low in level in ears with hearing loss, explaining the reduced or absent DPOAE fine structure. DPOAE generator components are also lower in level in ears with hearing loss than in ears without hearing loss. In ears that had both measurable generator and reflection components, the relationship between the two did not depend on the presence or absence of hearing loss. Because reflection components are not measurable in many ears with hearing thresholds >15 dB HL, stimuli that evoke other types of reflection emissions, such as stimulus-frequency or long-latency transient-evoked emissions, should be explored in conjunction with DPOAE generator components.

Frequency-change in DPOAE evoked by 1 s/octave sweeping primaries in newborns and adults.

Distortion product otoacoustic emissions (DPOAE) in newborns and adults were evoked by sweeping primaries up and down in frequency at 1 s/octave. Sweeping up and down in frequency resulted in changes in the amplitude vs. frequency functions of the composite DPOAE and its two major components. In addition, DPOAE component phases differed slightly between the up- and down-swept conditions. The changes in amplitude vs. frequency functions were quantified using a covariate correlation technique, yielding single-valued estimates of the magnitude of the frequency changes. Separate analyses were performed for the entire DPOAE frequency range and split into low and high frequency ranges. There were consistent changes in newborn and adult composite DPOAEs and reflection components, but not generator components. Adults had significant frequency changes in the composite DPOAE for all frequency ranges and in the reflection component for the entire frequency range. Newborns had significant frequency change in the reflection component for all frequency ranges. Differences in frequency change between adults and newborns may stem from developmental changes in cochlear processing. Alignment of the component phase differences between the up- and down-swept conditions resulted in elimination of frequency-change in reconstructed composite DPOAEs.

An Evidence-Based Systematic Review on the Diagnostic Accuracy of Hearing Screening Instruments for Preschool- and School-Age Children.

PURPOSE: The purpose of this article is to conduct an evidence-based systematic review on the accuracy of pure-tone or otoacoustic emission (OAE) screening for identifying hearing loss in preschool- and school-age children. METHOD: A systematic search of the literature published between 1975 and 2013 was conducted. Articles meeting the selection criteria were critically appraised for quality. Selection criteria required that behavioral thresholds be measured in children failing the screen and in at least a subset of children passing the screen. Sensitivity and specificity were used to calculate positive and negative likelihood ratios that could be compared between instruments. RESULTS: Eighteen studies were included in the final analysis. There was considerable variability among studies on stimulus levels, response criteria, and definition of hearing loss. Approximately half of positive and negative likelihood ratio pairs for OAEs (52%) and pure-tone screening (45%) were considered suggestive or informative for identifying hearing loss. CONCLUSIONS: Both pure-tone and OAE screening can identify hearing loss in preschool- and school-age children. Studies that compared both tools in the same population concluded that pure-tone screening had higher sensitivity than OAE screening and thus was considered the preferred tool. Future research should incorporate standard stimulus levels, response criteria, and definitions of hearing loss.

Wideband acoustic immittance measures: developmental characteristics (0 to 12 months).

Rapid developmental changes of the peripheral auditory system in normal infants occur in the first year of life. Specifically, the postnatal development of the external and middle ear affects all measures of external and middle ear function including wideband acoustic immittance(WAI). This article provides an overview of WAI studies in newborns and infants from a developmental perspective. Normative WAI data in newborns are fairly consistent across studies. However, there are discrepancies in some WAI measures between studies, possibly due to differences in sampling, methodology, and instrumentation. Accuracy of WAI measurements is compromised when a good probe seal cannot be maintained during testing or an inaccurate estimate of the cross-sectional area of the ear canal of newborns occurs. Comparison of WAI data between age groups from 0 to 12 months reveals maturation effects. Additional age-specific longitudinal and cross-sectional normative WAI data for infants from birth to 12 months are required to validate and consolidate existing data.

Pediatric applications of wideband acoustic immittance measures.

Wideband acoustic immittance (WAI) measures have potential capability to improve newborn hearing screening outcomes and middle ear diagnosis for infants and children. To fully capitalize on these immittance measures for pediatric hearing care, developmental and pathologic effects need to be fully understood. Published literature on wideband immittance (reflectance, absorbance, tympanometry, and acoustic reflexes) is reviewed in this article to determine pathologic effects in newborns, infants, and children relative to standard audiologic tests such as otoacoustic emissions (OAEs), standard tympanometry, air and bone conduction auditory brainstem response, and otoscopy. Infants and children with surgically confirmed otitis media with effusion have lower absorbance in the mid-frequency range (1 to 3 kHz) for the affected ear(s). Newborns that do not pass OAE screening at birth also have lower absorbance for frequencies from 1 to 3 kHz, suggesting that nonpass results are frequently associated with middle ear issues at birth. In Newborn Hearing Screening Programs, WAI may help to interpret hearing screening results. Conclusions are limited by the fact that the true status of the middle ear and cochlea are not known for newborns and infants in studies that use OAE or tympanometry as the reference standard. Likelihood ratios for reflectance against surgery gold standards range from diagnostically suggestive to informative. Although some of the results are promising, limited evidence and methodological considerations restrict the conclusions that can be drawn regarding the diagnostic accuracy of WAI technologies in infants and children. Additional investigations using stronger gold standard comparisons are needed to determine which tools can most accurately predict middle ear status in the pediatric population.

Prediction of conductive hearing loss using wideband acoustic immittance.

The purpose of this article was to review the effectiveness of wideband acoustic immittance (WAI) and tympanometry in detecting conductive hearing loss (CHL). Eight studies were included that measured CHL through air-and bone-conducted thresholds in at least a portion of their participants. One study included infants, three studies included children, one study included older children and adults, and three studies included adults. WAI identified CHL well in all populations. In infants and children, WAI in several single-frequency bands identified CHL with equal accuracy to measures of middle ear admittance using clinical tympanometry with a single probe tone (1000 Hz for infants; 226 Hz for children and adults). When WAI was combined across frequency bands, it identified CHL superior to traditional, single-frequency tympanometry. Only two studies used WAI tympanometry, which assesses the outer/middle ear across both frequency and introduced air pressure, and differing results were reported as to whether introducing pressure into the ear canal provides better identification of CHL. In general, WAI appears to be a promising clinical tool, and further investigation is warranted.

Consensus statement: Eriksholm workshop on wideband absorbance measures of the middle ear.

The participants in the Eriksholm Workshop on Wideband Absorbance Measures of the Middle Ear developed statements for this consensus article on the final morning of the Workshop. The presentations of the first 2 days of the Workshop motivated the discussion on that day. The article is divided into three general areas: terminology; research needs; and clinical application. The varied terminology in the area was seen as potentially confusing, and there was consensus on adopting an organizational structure that grouped the family of measures into the term wideband acoustic immittance (WAI), and dropped the term transmittance in favor of absorbance. There is clearly still a need to conduct research on WAI measurements. Several areas of research were emphasized, including the establishment of a greater WAI normative database, especially developmental norms, and more data on a variety of disorders; increased research on the temporal aspects of WAI; and methods to ensure the validity of test data. The area of clinical application will require training of clinicians in WAI technology. The clinical implementation of WAI would be facilitated by developing feature detectors for various pathologies that, for example, might combine data across ear-canal pressures or probe frequencies.

Identification of conductive hearing loss in young infants using tympanometry and wideband reflectance.

OBJECTIVE: The goal of the study was to evaluate the effectiveness of tympanometry and wideband reflectance (WBR) in detecting conductive hearing loss (CHL) in young infants. METHODS: Type of hearing loss was determined using auditory brainstem response using air- and bone-conducted tone bursts in 84 ears from 70 infants (median age = 10 weeks). Of these 84 ears, 60 are included in the current analysis: 43 with normal hearing (NH) and 17 with CHL. Tympanometry was measured using probe tone frequencies of 226, 678, and 1000 Hz. Tympanograms were evaluated in two ways: (1) Acoustic middle ear admittance (Ya, in millimhos); and (2) two-category classification (normal/abnormal), as described by Baldwin (2006). Measures of Ya were evaluated in two ways: by admittance-magnitude tympanograms and calculated admittance magnitude from subcomponents (conductance and susceptance). WBR was measured in response to a chirp stimulus after probe calibration. WBR was analyzed into thirteen 1/3 octave bands. Tests for statistical differences for two-category classification were analyzed using Chi-squared and Ya, and WBR were analyzed using repeated-measures analyses of variances. Cohen's d and likelihood ratios were computed for comparison with statistically significant differences. RESULTS: Ya measured with 678- and 1000 Hz probe tones was significantly different between ears with CHL and NH. Two-category classification of tympanograms using a 1000 Hz probe tone was significantly different between ears with CHL and NH. Neither two-category classification nor Ya was significantly different between ears identified with CHL and NH using a 226 Hz probe tone. WBR was significantly higher in the frequency bands 800 to 2500 Hz and in the frequency band centered at 6300 Hz in infants with CHL. Effect sizes (Cohen's d) were greater than 2 for several WBR frequency bands and Ya measured with 1000 Hz probe tones. The results were similar for calculations of Ya from admittance-magnitude and subcomponent tympanograms. Positive likelihood ratios for WBR ranged between 8.1 and 38, and those for Ya using 1000 Hz ranged between 12.5 and 32. CONCLUSIONS: CHL in young infants can be detected well with WBR or tympanometry using probe frequencies of 678 and 1000 Hz.

Hearing screening in a well-infant nursery: profile of automated ABR-fail/OAE-pass.

OBJECTIVES: The goals were to examine the prevalence of a screening outcome pattern of auditory brainstem response fail/otoacoustic emission pass (ABR-F/OAE-P) in a cohort of infants in well-infant nurseries (WINs), to profile children at risk for auditory neuropathy spectrum disorder, and to compare inpatient costs for 2 screening protocols using automated auditory brainstem response (ABR) and otoacoustic emission (OAE) screening. METHODS: A total of 10.6% (n = 2167) of 20 529 infants admitted to WINs in 2006-2009 were screened for auditory neuropathy spectrum disorder risk by using an experimental protocol (automated ABR testing first, followed by OAE testing if the automated ABR test was not passed). A second WIN cohort (n = 281) was screened by using the standard WIN protocol for the facility (OAE testing first, followed by automated ABR testing if the OAE test was not passed). Comparisons were made regarding preparation and testing times and personnel costs. RESULTS: The ABR-F/OAE-P outcome was found for 0.92% of infants in WINs in inpatient testing and none in outpatient rescreening. The time for test preparation was 4 times longer and that for test administration was 2.6 times longer for the experimental protocol, compared with the standard protocol. Inpatient costs for the experimental protocol included 3 times greater personnel time costs. CONCLUSIONS: Less than 1% of infants in WINs had ABR-F/OAE-P screening outcomes as inpatients and none as outpatients. These results suggest that prevalence is low for infants cared for in WINs and use of OAE testing as a screening tool in WINs is not unreasonable.

Infant air and bone conduction tone burst auditory brain stem responses for classification of hearing loss and the relationship to behavioral thresholds.

OBJECTIVE: A clinical protocol for diagnosing hearing loss (HL) in infants designed to meet early intervention guidelines was used with the goals of providing normative data for (1) frequency-specific tone burst auditory brain stem response (TBABR) thresholds by air conduction (AC) and bone conduction (BC) in early infancy used to classify type and severity of HL, (2) ear-specific behavioral thresholds for these same infants by 1 yr of age, and (3) the relationship between TBABR thresholds and behavioral thresholds for this group of infants. DESIGN: AC- and BC-TBABRs were measured in young infants (mean age, <3 mo) under natural sleep to classify the type and severity of HL (conductive, sensorineural, or mixed). A small group of normal-hearing adults undergoing the same TBABR protocol served as a control group. Threshold and latency data for AC- and BC-ABR were analyzed for infants classified as having normal hearing and for those with and without conductive HL. The ability to detect conductive HL based on ABR latencies evoked by clicks presented at 80 dB nHL was assessed. Behavioral thresholds using visual reinforcement audiometry (VRA) were measured in infants at a mean age of approximately 10 mo. The relationship between TBABR and behavioral thresholds obtained in infancy was analyzed, and the prediction of behavioral thresholds from TBABR thresholds was examined. RESULTS: Mean TBABR thresholds in young infants with normal hearing tested under natural sleep were similar to previously published data. The relationship between AC- and BC-TBABR thresholds differed as a function of stimulus frequency for infants but not adults. A mean air-bone gap (ABG) of 15 dB was present at 500 Hz even in normal-hearing infants, with those infants classified as having conductive HL presenting with substantially larger ABGs. Wave V latency functions for AC- and BC-TBABR also differed between infants and adults as a function of frequency. Infant BC-TBABR latencies were well matched between those with normal hearing and conductive HL, whereas AC-TBABR latency functions separated these groups. Mean VRA thresholds using insert phones in normal-hearing infants tested were between 14 and 17 dB HL for all three test frequencies at a mean age of 9.7 mo. Correlations between TBABR and VRA thresholds, both obtained during infancy, were strong for all three test frequencies (r = 0.86, 0.90, and 0.91 for 500, 2000, and 4000 Hz, respectively). CONCLUSIONS: AC- and BC-TBABR results can be readily obtained in young infants under natural sleep and were used to classify the type of HL based on the absolute threshold and the size of the ABG. Differences in wave V latency functions for TBABR by AC and BC and wave I and V latencies of the high-level click ABR also distinguish between infants with and without TBABR ABGs. Ear-specific behavioral responses can be obtained at levels under 20 dB HL in normal-hearing infants younger than 1 yr using VRA, and these behavioral thresholds correlate well with TBABR thresholds obtained on average 6.5 mo previously in this population. The current results suggest that protocols for obtaining AC- and BC-TBABR and behavioral thresholds that meet guidelines for early intervention are clinically feasible.

Changes in transient-evoked otoacoustic emissions in the first month of life.

OBJECTIVE: Current Joint Committee on Infant Hearing guidelines recommend the use of transient-evoked otoacoustic emissions (TEOAEs) as a screening tool to identify hearing loss for newborns cared for in the well-baby nursery. Newborns who do not pass the TEOAE screen before leaving the hospital are typically rescreened as outpatients by 1 mo of age, at which time, approximately 50 to 70% pass screening criteria. To better understand why many infants are referred at initial screening but pass at the rescreening, more complete knowledge of developmental differences in the TEOAE levels, noise floor, or a combination of both for infants who pass and fail birth screening is needed. In addition, it has been shown that infants with occluding ear-canal debris are more likely to not pass TEOAE screening at the hospital than those without occluding ear-canal debris. This study explores whether changes in TEOAE levels in half-octave frequency bands are related to changes in ear-canal debris over the first month of life. DESIGN: Seventy-nine neonates from a well-baby nursery had their hearing screened before leaving the hospital and again at approximately 1 mo of age. All participants passed the follow-up screening. Overall TEOAE levels and levels in half-octave frequency bands centered at 1.5, 2, 3, and 4 kHz were measured. Judgments of ear-canal debris were made by otoscopy and were rated using one of three categories at both visits. RESULTS: TEOAE levels in infants significantly increased from birth to 1 mo of age across all frequencies tested, regardless of whether they passed or failed the screening at birth. The increase in TEOAE level was frequency dependent, with the greatest increases occurring in the highest frequency bands. No significant correlation between debris change and frequency-specific changes was found for either ear. Infants who failed the screening at birth but who subsequently passed at 1 mo of age had significantly lower TEOAE levels at the rescreening than did infants with passing TEOAE levels at birth. However, pass/fail status at birth was only a weak predictor of TEOAE levels at 1 mo of age. CONCLUSIONS: The increase in TEOAE levels during the first month of life is frequency dependent, with greater increases occurring at higher frequencies. Increased TEOAE levels were not associated with changes in ear-canal debris.

Changes in transient-evoked otoacoustic emission levels with negative tympanometric peak pressure in infants and toddlers.

OBJECTIVES: Otoacoustic emission (OAE) testing is now a standard component of the diagnostic audiology protocol for infants and toddlers and is an excellent tool for detecting moderate-to-profound cochlear hearing loss. Detection of hearing loss is especially important in infants and toddlers. Unfortunately, middle-ear dysfunction has a high incidence in this age range and can confound interpretation of OAEs. The goal of the study was to determine how transient-evoked otoacoustic emission (TEOAE) and noise levels were different when tympanometric peak pressures (TPP) measured from tympanograms were normal versus negative in the same individual. Another goal was to determine how TEOAE screening pass rates using a priori pass criteria were affected on days when TPP was negative. DESIGN: TEOAE and noise levels were collected in 18 cases under 2 conditions: on a day when the tympanogram TPP was normal and on a day when the tympanogram TPP was negative. Data were collected from 11 children aged 3 to 39 mo, some of whom were tested more than once. Paired t tests were performed to determine whether there were changes in overall TEOAE and noise levels and TEOAE and noise levels analyzed into half-octave bands. A one-way ANOVA was performed on differences across half-octave bands to determine whether TPP affected TEOAE levels for some frequency bands more than others. Equality-of-proportion Z tests were run to determine whether there were significant differences in the percentage of "passes" on days when TPP was negative and TPP was normal. RESULTS: Mean TEOAE level was lower when TPP was negative, but noise levels did not change between the 2 conditions. Mean TEOAE levels were lower for all frequency bands from 1000 to 4000 Hz and no significant differences were found among the mean reduction across frequency bands. There were no significant differences in the percentage of passes between TEOAEs collected on days when TPP was normal and when TPP was negative. CONCLUSIONS: Mean data indicated that when tympanograms had negative TPP, TEOAE level was lower by approximately 4 dB across all frequency bands. However, this affected the pass rate in only 5% to 6% of cases. Although the number of participants in the current study was small, the data suggest that it is possible to measure TEOAEs in children with negative TPP. If emission-to-noise ratio is used to identify hearing loss in mid-to-high frequency bands, the majority of children will still have TEOAEs that meet clinical criteria, this providing the clinician with important information about cochlear status.

Effects of anesthesia on DPOAE level and phase in rats.

Many studies of the auditory system are performed on animals under general anesthesia. A concern for researchers is that these agents may significantly alter the underlying neurophysiologic mechanisms being studied. The effects may very across species, and even among individuals within a species. An investigation was undertaken to study whether DPOAE measures differ using three different anesthetic regimens: acetylpromazine-ketamine, xylazine-ketamine, and sodium pentobarbital. The same rat was anesthetized in three consecutive weeks using a different anesthetic regimen each week. DPOAE magnitude and phase temporal responses were recorded from which several measures were taken: DPOAE levels at the onset of the primaries, changes in DPOAE level as a function of time during presentation of the primaries (DeltaLI) and changes in DPOAE level (DeltaLC) and phase (DeltaPC) during presentation of a broad-band noise presented contralateral to the probe. Each week the same measurements were repeated with the rat anesthetized using a different regimen and at the end of the third week, the middle ear muscles were sectioned and the measurements repeated once again. Results showed that the anesthetic regimens did not differentially alter the DPOAE onset levels. When sodium pentobarbital was used as the anesthetic regimen, DeltaLC and DeltaPC were significantly smaller relative to those measured when the rats were anesthetized with acetylpromazine-ketamine and xylazine-ketamine. Based on the assumption that large, positive (DeltaPC) values are related to middle ear muscle activation, the middle ear muscle reflex remained at least partially active in some rats under sodium pentobarbital anesthesia. The DeltaLI measures were significantly smaller when the animals were anesthetized with xylazine-ketamine and sodium pentobarbital than when they were anesthetized with acetylpromazine-ketamine. Recordings taken after sectioning the middle ear muscles suggested that the middle ear muscle reflex substantially contributes to DeltaLC and DeltaPC measures under the anesthetic regimens xylazine-ketamine and acetylpromazine-ketamine. Data indicated that anesthetic agents variably alter neurophysiologic mechanisms involved with the complex control of the auditory signal even among individuals in the same species. Extreme care should be taken when comparing DeltaLI, DeltaLC and DeltaPC across studies when different anesthetic regimens are used within and across species.

Test-retest reliability of wideband reflectance measures in infants under screening and diagnostic test conditions.

OBJECTIVE: The main goal of this study was to examine the test-retest reliability of wideband reflectance (WBR) measures collected from infants in screening and diagnostic hearing test environments. In addition, the results of WBR testing for infants who passed and failed otoacoustic emission (OAE) screening were examined to determine whether these measures distinguished between the two groups. DESIGN: Repeated WBR measures were collected from two groups of infants, one group tested in an outpatient hearing screening setting and the other group in a diagnostic test setting. For a total of 127 infants and a control group of 10 adults, repeated WBR measurements were made with the probe left in place between the two tests (T1 and T2) and after reinsertion of the probe (T3) for a total of 3 measurements. Test-retest differences were calculated for each individual across one-third octave frequency bands, and the mean and 90th percentile were calculated by subject group and OAE results. WBR patterns were also compared between infants who passed versus failed OAE screening. RESULTS: Mean test-retest differences were smaller for the diagnostic group than for the screening group. Test-retest differences were largest for the reinsertion condition and for the frequencies below 500 Hz. While the low frequencies were variable, the test-retest differences were smallest in the mid-frequency range which is thought to be the frequency range most sensitive to middle ear dysfunction. Test-retest performance did not differ between infants who passed or failed OAE screening. However, infants who failed OAE screening had significantly higher WBR in the range from 630 to 2000 Hz than infants who passed OAE screening. CONCLUSIONS: Test-retest performance was poor for frequencies below 500 Hz, but in general test-retest differences were small across the important mid-frequency range. Reinsertion of the probe between repeated tests yielded larger and more variable test-retest differences. Careful monitoring of probe fit and testing while infants are in a quiet state appears to be critical for obtaining reliable WBR results. Analysis of WBR results indicated significantly higher reflected energy in the mid-frequency range for infants who failed OAE screening than for those who passed OAE screening. Although conclusions are limited by the fact that the true status of the middle ear and cochlea were not known for the infants in this study, this result may indicate that a number of these infants failed OAE screening due to transient or permanent middle ear dysfunction which was detected by WBR.

Normative multifrequency tympanometry in infants and toddlers.

Multifrequency tympanometry data were measured multiple times between the ages of four weeks and two years from 33 infants/toddlers. Tympanograms were also measured from 33 adult participants. Tympanograms recorded with five probe-tone frequencies (226, 400, 630, 800, and 1000 Hz) were classified using the Vanhuyse et al model classification system (Vanhuyse et al, 1975). Admittance at +200 daPa (Y200) and middle ear admittance (Y(ME)) were calculated. The proportion of Vanhuyse et al patterns in infants and toddlers was different than in adults, especially for younger ages. Y(ME) and Y200 both increased with age. Y(ME) and Y200 data for all infant/toddler groups were significantly lower than adult values at all of the tested probe-tone frequencies. These data can be used as a guide in the clinic to assess normal tympanometric values for infants and toddlers.