Amblyaudia: Review of Pathophysiology, Clinical Presentation, and Treatment of a New Diagnosis

The effect of tympanostomy tubes on otoacoustic emissions

PURPOSE

Otoacoustic emissions (OAE) are a common screening tool to evaluate cochlear function. Middle ear dysfunction has been shown to impact results of otoacoustic emission testing, but there are limited data on the effect of tympanostomy tubes on OAE. The purpose of this study was to determine whether tympanostomy tube placement significantly improved OAE.

METHODS

A retrospective review of charts was completed for patients younger than 18 years old who underwent tympanostomy tube placement from January 1, 2018 to September 1, 2023 and had preoperative and postoperative OAE testing within 6 months of surgery. The primary variable was presence of OAE preoperatively and postoperatively. Chi-square analysis and t test were used for statistical analysis.

RESULTS

A total of 212 ears were examined from 111 pediatric patients who underwent tympanostomy tube placement during the study period. Presence of OAE at 3000, 4000, and 5000 Hz were all noted to significantly increase following tympanostomy tube placement, with OAE presence increasing from approximately 27.8% of the sample preoperatively to 95.3% postoperatively at 3000 and 4000 Hz. Patients who noted improvement had a significantly higher proportion of type B tympanogram preoperatively, compared to a higher proportion of type A tympanogram noted in patients who did not note improvement.

CONCLUSION

Tympanostomy tubes can significantly improve otoacoustic emissions in patients with middle ear dysfunction.

Behavioral and Cortical Activation Changes in Children Following Auditory Training for Dichotic Deficits

We report changes following auditory rehabilitation for interaural asymmetry (ARIA) training in behavioral test performance and cortical activation in children identified with dichotic listening deficits. In a one group pretest-posttest design, measures of dichotic listening, speech perception in noise, and frequency pattern identification were assessed before and 3 to 4.5 months after completing an auditory training protocol designed to improve binaural processing of verbal material. Functional MRI scans were also acquired before and after treatment while participants passively listened in silence or to diotic or dichotic digits. Significant improvements occurred after ARIA training for dichotic listening and speech-in-noise tests. Post-ARIA, fMRI activation increased during diotic tasks in anterior cingulate and medial prefrontal regions and during dichotic tasks, decreased in the left precentral gyrus, right-hemisphere pars triangularis, and right dorsolateral and ventral prefrontal cortices, regions known to be engaged in phonologic processing and working memory. The results suggest that children with dichotic deficits may benefit from the ARIA program because of reorganization of cortical capacity required for listening and a reduced need for higher-order, top-down processing skills when listening to dichotic presentations.

Is There a Role for Intraoperative Navigation During Cochlear Implantation in Patients With Aural Atresia?

OBJECTIVE

Concurrent bilateral congenital aural atresia (CAA) and profound sensorineural hearing loss are rare. While not a contraindication, temporal bone and cochleovestibular abnormalities are an important consideration for cochlear implantation (CI) candidacy. Intraoperative image-guided surgical navigation may play a role during CI surgery in patients with complex anatomy, such as CAA.

PATIENT

One patient with bilateral CAA, cochlear dysplasia, speech delay, and profound sensorineural hearing loss underwent candidacy evaluation for cochlear implantation.

INTERVENTIONS

Cochlear implantation using intraoperative image-guided navigation.

MAIN OUTCOME MEASURES

(1) Registration accuracy, (2) surgical outcomes, (3) audiometry.

RESULTS

A four-year-old girl with complete bilateral CAA and profound sensorineural hearing loss successfully underwent a right transmastoid approach for CI using intraoperative image-guided navigation with sticker fiducials. Bony landmarks included the mastoid tip, tympanomastoid suture line, helical root, zygomatic root, and lateral brow. A registration accuracy of 0.9 mm was achieved. There were no intraoperative or immediate postoperative complications. Postoperatively, Neural Response Imaging was confirmed on 9 electrodes and behavioral testing demonstrated Ling-6 access at 30 dB. On most recent follow-up, she has demonstrated gains in language development, vocalizations, and uses total communication in a hearing-impaired educational environment.

CONCLUSIONS

Children with CAA and profound sensorineural hearing loss may be candidates for cochlear implantation, with successful outcomes in the setting of complex anatomy. Surgical navigation may play a role corroborating intraoperative landmarks.

Dichotic listening deficits in amblyaudia are characterized by aberrant neural oscillations in auditory cortex

OBJECTIVE

Children diagnosed with auditory processing disorder (APD) show deficits in processing complex sounds that are associated with difficulties in higher-order language, learning, cognitive, and communicative functions. Amblyaudia (AMB) is a subcategory of APD characterized by abnormally large ear asymmetries in dichotic listening tasks.

METHODS

Here, we examined frequency-specific neural oscillations and functional connectivity via high-density electroencephalography (EEG) in children with and without AMB during passive listening of nonspeech stimuli.

RESULTS

Time-frequency maps of these "brain rhythms" revealed stronger phase-locked beta-gamma (~35 Hz) oscillations in AMB participants within bilateral auditory cortex for sounds presented to the right ear, suggesting a hypersynchronization and imbalance of auditory neural activity. Brain-behavior correlations revealed neural asymmetries in cortical responses predicted the larger than normal right-ear advantage seen in participants with AMB. Additionally, we found weaker functional connectivity in the AMB group from right to left auditory cortex, despite their stronger neural responses overall.

CONCLUSION

Our results reveal abnormally large auditory sensory encoding and an imbalance in communication between cerebral hemispheres (ipsi- to -contralateral signaling) in AMB.

SIGNIFICANCE

These neurophysiological changes might lead to the functionally poorer behavioral capacity to integrate information between the two ears in children with AMB.

Pediatric Single-Sided Deafness: A Review of Prevalence, Radiologic Findings, and Cochlear Implant Candidacy

OBJECTIVE

To characterize the prevalence, imaging characteristics, and cochlear implant candidacy of pediatric patients with single-sided deafness (SSD).

METHODS

An audiometric database of patients evaluated at a large tertiary academic medical center was retrospectively queried to identify pediatric patients (<18 years old) with SSD, defined as severe to profound sensorineural hearing loss in one ear and normal hearing in the other. Medical records of identified patients were reviewed to characterize the prevalence, etiology, and cochlear implant candidacy of pediatric patients with SSD.

RESULTS

We reviewed audiometric data obtained from 1993 to 2018 for 52,878 children at our institution. 191 (0.36%) had the diagnosis of SSD. Cochlear nerve deficiency (either hypoplasia or aplasia) diagnosed on MRI and/or CT was the most common etiology of SSD and was present in 22 of 88 (25%) pediatric SSD patients with available imaging data. 70 of 106 (66%) pediatric SSD patients with available imaging had anatomy amenable to cochlear implantation.

CONCLUSIONS

Pediatric SSD is a rare condition and the most common etiology based on radiology is cochlear nerve deficiency. High resolution imaging of the temporal bone is essential to determine cochlear nerve morphology prior to consideration of cochlear implantation.

Spatial Hearing as a Function of Presentation Level in Moderate-to-Severe Unilateral Conductive Hearing Loss

HYPOTHESIS

Patients with moderate-to-severe unilateral conductive hearing loss (UCHL) can make use of binaural difference cues when stimuli are presented at a high enough intensity to provide audibility in the affected ear.

BACKGROUND

Spatial hearing is essential for listening in complex environments and sound source localization. Patients with UCHL have decreased access to binaural difference cues, resulting in poorer spatial hearing abilities compared with listeners with normal hearing.

METHODS

Twelve patients with moderate-to-severe UCHL, most due to atresia (83.3%), and 12 age-matched controls with normal hearing bilaterally participated in this study. Outcome measures included: 1) spatial release from masking, and 2) sound source localization. Speech reception thresholds were measured with target speech (Pediatric AzBio sentences) presented at 0 degree and a two-talker masker that was either colocated with the target (0 degree) or spatially separated from the target (symmetrical, ±90 degrees). Spatial release from masking was quantified as the difference between speech reception thresholds in these two conditions. Localization ability in the horizontal plane was assessed in a 180 degree arc of 11 evenly-spaced loudspeakers. These two tasks were completed at 50 and 75 dB SPL.

RESULTS

Both children and adults with UCHL performed more poorly than controls when recognizing speech in a spatially separated masker or localizing sound; however, this group difference was larger at 50 than 75 dB SPL.

CONCLUSION

Patients with UCHL experience improved spatial hearing with the higher presentation level, suggesting that the auditory deprivation associated with a moderate-to-severe UCHL does not preclude exposure to-or use of-binaural difference cues.

Dichotic listening performance with cochlear-implant simulations of ear asymmetry is consistent with difficulty ignoring clearer speech

There are an increasing number of bilateral and single-sided-deafness cochlear-implant (CI) users who hope to achieve improved spatial-hearing abilities through access to sound in both ears. It is, however, unclear how speech is processed when inputs are functionally asymmetrical, which may have an impact on spatial-hearing abilities. Therefore, functionally asymmetrical hearing was controlled and parametrically manipulated using a channel vocoder as a CI simulation. In Experiment 1, normal-hearing (NH) listeners performed a dichotic listening task (i.e., selective attention to one ear, ignoring the other) using asymmetrical signal degradation. Spectral resolution varied independently in each ear (4, 8, 16 channels, and unprocessed control). Performance decreased with decreasing resolution in the target ear and increasing resolution in the interferer ear. In Experiment 2, these results were replicated using a divided attention task (attend to both ears, report one after sentence completion) in both NH and bilateral CI listeners, although overall performance was lower than in Experiment 1. In Experiment 3, frequency-to-place mismatch simulated shallow CI insertion depths (0, 3, 6-mm shifts, and unprocessed control). Performance mostly decreased with increasing shift in the target ear and decreasing shift in the interferer ear; however, performance nonmonotonicities occurred. The worst performance occurred when the shift matched across ears, suggesting that pitch similarity increases difficulty. The results show that it is more difficult to attend an ear that is relatively degraded or distorted, which may set spatial-hearing limitations for CI users when trying to attend to a target in complex auditory scenes.

Consistent and chronic cochlear implant use partially reverses cortical effects of single sided deafness in children

Potentially neuroprotective effects of CI use were studied in 22 children with single sided deafness (SSD). Auditory-evoked EEG confirmed strengthened representation of the intact ear in the ipsilateral auditory cortex at initial CI activation in children with early-onset SSD (n = 15) and late-onset SSD occurring suddenly in later childhood/adolescence (n = 7). In early-onset SSD, representation of the hearing ear decreased with chronic CI experience and expected lateralization to the contralateral auditory cortex from the CI increased with longer daily CI use. In late-onset SSD, abnormally high activity from the intact ear in the ipsilateral cortex reduced, but responses from the deaf ear weakened despite CI use. Results suggest that: (1) cortical reorganization driven by unilateral hearing can occur throughout childhood; (2) chronic and consistent CI use can partially reverse these effects; and (3) CI use may not protect children with late-onset SSD from ongoing deterioration of pathways from the deaf ear.

Sound localization latency in normal hearing and simulated unilateral hearing loss

Directing gaze towards auditory events is a natural behavior. In addition to the well-known accuracy of auditory elicited gaze responses for normal binaural listening, their latency is a measure of possible clinical interest and methodological importance. The aim was to develop a clinically feasible method to assess sound localization latency (SLL), and to study SLL as a function of simulated unilateral hearing loss (SUHL) and the relationship with accuracy. Eight healthy and normal-hearing adults (18-40 years) participated in this study. Horizontal gaze responses, recorded by non-invasive corneal reflection eye-tracking, were obtained during azimuthal shifts (24 trials) of a 3-min continuous auditory stimulus. In each trial, a sigmoid function was fitted to gaze samples. Latency was estimated by the abscissa corresponding to 50% of the arctangent amplitude. SLL was defined as the mean latency across trials. SLL was measured in normal-hearing and simulated SUHL conditions (SUHL₃₀ and SUHL₄₃: mean threshold of 30 dB HL and 43 dB HL across 0.5, 1, 2, and 4 kHz). In the normal-hearing condition, the mean ± SD SLL was 280 ± 40 ms (n = 8) with a test-retest SD = 20 ms. A linear mixed model showed a statistically significant effect of listening condition on SLL. The SUHL₃₀ and SUHL₄₃ conditions revealed a mean SLL of 370 ± 49 ms and 540 ± 120 ms, respectively. Repeated measures correlation analysis showed a clear relationship between SLL and the average sound localization accuracy (R² = 0.94). The rapid and reliable method to obtain SLL may be an important clinical tool for evaluation of binaural processing. Future studies in clinical cohorts are needed to assess whether SLL may reveal information about binaural processing abilities beyond that afforded by sound localization accuracy.

Early diagnosis and treatment of unilateral or asymmetrical hearing loss in children: CODEPEH recommendations

The aim of this document is to improve the management and the treatment of unilateral or asymmetrical hearing loss in children. One in one thousand newborn infants has unilateral hearing loss and this prevalence increases with age, due to cases of acquired and delayed-onset hearing loss. Although the impact on the development and learning processes of children of these kinds of hearing loss have usually been minimized, if they are not treated they will impact on language and speech development, as well as overall development, affecting the quality of life of the child and his/her family. The outcomes of the review are expressed as recommendations aimed at clinical diagnosis and therapeutic improvement for unilateral or asymmetrical hearing loss.

Intrinsic and Miniature Postsynaptic Current Changes in Rat Principal Neurons of the Lateral Superior Olive after Unilateral Auditory Deprivation at an Early Age

Unilateral auditory deprivation results in lateralization changes in the central auditory system, interfering with the integration of binaural information and thereby leading to a decrease in binaural auditory functions such as sound localization. Principal neurons of the lateral superior olive (LSO) are responsible for computing the interaural intensity differences that are critical for sound localization in the horizontal plane. To investigate changes caused by unilateral auditory deprivation, electrophysiological activity was recorded from LSO principal neurons in control rats and rats with unilateral cochlear ablation. At one week after unilateral cochlear ablation, the excitability of LSO principal neurons on the side ipsilateral to the ablation (the ablated side) was greater than that on the side contralateral to the ablation (the intact side); however, the input resistance increased on both sides. Furthermore, by analysing the miniature inhibitory postsynaptic currents and miniature excitatory postsynaptic currents, we found that unilateral auditory deprivation weakened the inhibitory driving force on the intact side, whereas it strengthened the excitatory driving force on the ablated side. In summary, asymmetric changes in the electrophysiological activity of LSO principal neurons were found on both sides at postnatal day 19, one week after unilateral cochlear ablation.

Contralateral Interference Caused by Binaurally Presented Competing Speech in Adult Bilateral Cochlear-Implant Users

OBJECTIVES

Bilateral cochlear implants (BI-CIs) are intended to improve sound localization and speech understanding in the presence of interfering sounds. For normal-hearing listeners, improved speech understanding in the presence of interfering sounds can be achieved with monaural head shadow and binaural unmasking. While some BI-CI listeners experience binaural unmasking under certain testing conditions, others appear to not. This study tested a group of BI-CI users with hearing histories that have been linked to poor binaural processing-early onset of deafness or long duration of deafness in just one ear. We predicted that these listeners would experience the opposite of binaural unmasking (i.e., contralateral interference) when trying to understand speech in the presence of a competing talker.

DESIGN

Nine adult BI-CI users who were deafened early in life or had an asymmetric hearing history (e.g., a much longer duration of deafness in one ear) participated in this study. The coordinate response measure corpus was used to assess speech understanding for a male target talker in quiet or in the presence of one male competing talker. Experiment 1 measured binaural unmasking in a paradigm that provided no head-shadow component. The target was always presented monaurally, while the interferer was presented either monaurally or diotically. Experiment 2 measured spatial release from masking in a paradigm that included both a head-shadow component and possible binaural-unmasking component. Nonindividualized head-related transfer functions were used to simulate talker locations in the front or 90° to the left or right.

RESULTS

In experiment 1, all nine listeners experienced contralateral interference (9 dB on average). Four listeners demonstrated roughly symmetric contralateral interference; five listeners experienced asymmetrical contralateral interference. In experiment 2, the listeners experienced only 1 dB of spatial release from masking on average; this small amount was possibly a result of the contralateral interference observed in experiment 1. The results were best explained by individual differences in speech understanding in quiet, which significantly correlated with the duration of deafness in the ipsilateral ear. Specifically, instances of asymmetrical contralateral interference could correspond to asymmetrical hearing histories.

CONCLUSIONS

Bilateral cochlear implantation should provide a hearing benefit to the recipient. For the BI-CI listeners specifically recruited for this study, there seems to be a conflict with processing the auditory information across the two ears, which produced the opposite of the desired hearing benefit. This suggests that there may be a subset of potential BI-CI users for whom contralateral interference offsets much of the potential head-shadow benefit. If so, earlier implantation in the second implanted ear might have produced larger binaural benefits, which is important information for clinicians advising patients considering bilateral implantation.

Auditory Brainstem Implants: Recent Progress and Future Perspectives

The auditory brainstem implant (ABI) was first developed nearly 40 years ago and provides auditory rehabilitation to patients who are deaf and ineligible for cochlear implant surgery due to abnormalities of the cochlea and cochlear nerve. The aims of the following review are to describe the history of the ABI and innovations leading up to the modern ABI system, as well as highlight areas of future development in implant design.

Amplitude Modulation Detection in Children with a History of Temporary Conductive Hearing Loss Remains Impaired for Years After Restoration of Normal Hearing

Otitis media with effusion (OME) is considered a form of relative sensory deprivation that often occurs during a critical period of language acquisition in children. Animal studies have demonstrated that hearing loss during early development can impair behavioral sensitivity to amplitude modulation (AM), critical for speech understanding, even after restoration of normal hearing thresholds. AM detection in humans with a history of OME-associated conductive hearing loss (CHL) has not been previously investigated. Our objective was to determine whether OME-associated CHL in children ages 6 months to 3 years results in deficits in AM detection in later childhood, after restoration of normal audiometric thresholds. Children ages 4 to 7 years with and without a history of OME-associated CHL participated in an AM detection two-alternative forced-choice task at 8 and 64 Hz modulation frequencies using a noise carrier signal and an interactive touch screen interface. Thirty-four subjects were studied (17 with a history of OME-related CHL and 17 without). Modulation detection thresholds improved with age and were slightly lower (more sensitive) for the 64 Hz modulation frequency for both groups. Modulation detection thresholds of children with a history of OME-associated CHL were higher than control thresholds at 5 years, but corrected to expected levels between ages 6-7. OME-associated CHL results in impaired AM detection, even when measured years after restoration of normal audiometric thresholds. Future studies may shed light on implications for speech and language development and academic success for children affected by OME and associated conductive hearing loss.

Development, organization and plasticity of auditory circuits: Lessons from a cherished colleague

Ray Guillery was a neuroscientist known primarily for his ground-breaking studies on the development of the visual pathways and subsequently on the nature of thalamocortical processing loops. The legacy of his work, however, extends well beyond the visual system. Thanks to Ray Guillery's pioneering anatomical studies, the ferret has become a widely used animal model for investigating the development and plasticity of sensory processing. This includes our own work on the auditory system, where experiments in ferrets have revealed the role of sensory experience during development in shaping the neural circuits responsible for sound localization, as well as the capacity of the mature brain to adapt to changes in inputs resulting from hearing loss. Our research has also built on Ray Guillery's ideas about the possible functions of the massive descending projections that link sensory areas of the cerebral cortex to the thalamus and other subcortical targets, by demonstrating a role for corticothalamic feedback in the perception of complex sounds and for corticollicular projection neurons in learning to accommodate altered auditory spatial cues. Finally, his insights into the organization and functions of transthalamic corticocortical connections have inspired a raft of research, including by our own laboratory, which has attempted to identify how information flows through the thalamus.

A review of the effects of unilateral hearing loss on spatial hearing

The capacity of the auditory system to extract spatial information relies principally on the detection and interpretation of binaural cues, i.e., differences in the time of arrival or level of the sound between the two ears. In this review, we consider the effects of unilateral or asymmetric hearing loss on spatial hearing, with a focus on the adaptive changes in the brain that may help to compensate for an imbalance in input between the ears. Unilateral hearing loss during development weakens the brain's representation of the deprived ear, and this may outlast the restoration of function in that ear and therefore impair performance on tasks such as sound localization and spatial release from masking that rely on binaural processing. However, loss of hearing in one ear also triggers a reweighting of the cues used for sound localization, resulting in increased dependence on the spectral cues provided by the other ear for localization in azimuth, as well as adjustments in binaural sensitivity that help to offset the imbalance in inputs between the two ears. These adaptive strategies enable the developing auditory system to compensate to a large degree for asymmetric hearing loss, thereby maintaining accurate sound localization. They can also be leveraged by training following hearing loss in adulthood. Although further research is needed to determine whether this plasticity can generalize to more realistic listening conditions and to other tasks, such as spatial unmasking, the capacity of the auditory system to undergo these adaptive changes has important implications for rehabilitation strategies in the hearing impaired.

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Unilateral hearing loss in infancy can disrupt spatial hearing, even after binaural inputs are restored.

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Plasticity in the developing brain enables substantial recovery in sound localization accuracy.

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Adaptation to unilateral hearing loss is based on reweighting of monaural spectral cues and binaural plasticity.

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Training on auditory tasks can partially compensate for unilateral hearing loss, highlighting potential therapies.

On the Etiology of Listening Difficulties in Noise Despite Clinically Normal Audiograms

Many people with difficulties following conversations in noisy settings have “clinically normal” audiograms, that is, tone thresholds better than 20 dB HL from 0.1 to 8 kHz. This review summarizes the possible causes of such difficulties, and examines established as well as promising new psychoacoustic and electrophysiologic approaches to differentiate between them. Deficits at the level of the auditory periphery are possible even if thresholds remain around 0 dB HL, and become probable when they reach 10 to 20 dB HL. Extending the audiogram beyond 8 kHz can identify early signs of noise-induced trauma to the vulnerable basal turn of the cochlea, and might point to “hidden” losses at lower frequencies that could compromise speech reception in noise. Listening difficulties can also be a consequence of impaired central auditory processing, resulting from lesions affecting the auditory brainstem or cortex, or from abnormal patterns of sound input during developmental sensitive periods and even in adulthood. Such auditory processing disorders should be distinguished from (cognitive) linguistic deficits, and from problems with attention or working memory that may not be specific to the auditory modality. Improved diagnosis of the causes of listening difficulties in noise should lead to better treatment outcomes, by optimizing auditory training procedures to the specific deficits of individual patients, for example.

Response to de Wit et al., 2016, "Characteristics of Auditory Processing Disorders: A Systematic Review"

PURPOSE

This letter to the editor is in response to a review by de Wit et al. (2016), "Characteristics of Auditory Processing Disorders: A Systematic Review," published in April 2016 by Journal of Speech, Language, and Hearing Research.

CONCLUSION

The author argues that the conclusions in the de Wit et al. (2016) review are unfortunate in light of advances made in the clinical diagnosis and treatment of bottom-up auditory processing disorders in children.

The Effect of Age and History of Recurrent Otitis Media on Dichotic Listening and Verbal Memory in Children

OBJECTIVES

To explore the possible effects of recurrent otitis media (ROM) in early childhood on binaural processing and verbal memory in school-aged children.

METHODS

Two hundred eleven children, including 31 children with and 180 children without a history of ROM, were examined. A dichotic digit test (DDT) and a forward and backward digit memory span test (DMST) were administered.

RESULTS

A significant difference was observed between age groups among ROM-free children. The ROM-positive group earned significantly poorer results than the ROM-free group in all measurements, except for the right DDT (rDDT) score. Furthermore, a significant correlation was found between the DDT and EA scores with both DMST scores in the ROM-free group. The correlation between the rDDT and forward DMST scores was not significant in the ROM-positive group, and no significant correlation was observed between the EA score and either DMST score.

CONCLUSIONS

Our findings support that a history of OM in early childhood based on a parental survey of children is associated with differences in DDT and DMST outcomes.