The Strength of the Medial Olivocochlear Reflex in Chinchillas Is Associated With Delayed Response Performance in a Visual Discrimination Task With Vocalizations as Distractors

The ability to perceive the world is not merely a passive process but depends on sensorimotor loops and interactions that guide and actively bias our sensory systems. Understanding which and how cognitive processes participate in this active sensing is still an open question. In this context, the auditory system presents itself as an attractive model for this purpose as it features an efferent control network that projects from the cortex to subcortical nuclei and even to the sensory epithelium itself. This efferent system can regulate the cochlear amplifier sensitivity through medial olivocochlear (MOC) neurons located in the brainstem. The ability to suppress irrelevant sounds during selective attention to visual stimuli is one of the functions that have been attributed to this system. MOC neurons are also directly activated by sounds through a brainstem reflex circuit, a response linked to the ability to suppress auditory stimuli during visual attention. Human studies have suggested that MOC neurons are also recruited by other cognitive functions, such as working memory and predictability. The aim of this research was to explore whether cognitive processes related to delayed responses in a visual discrimination task were associated with MOC function. In this behavioral condition, chinchillas held their responses for more than 2.5 s after visual stimulus offset, with and without auditory distractors, and the accuracy of these responses was correlated with the magnitude of the MOC reflex. We found that the animals’ performance decreased in presence of auditory distractors and that the results observed in MOC reflex could predict this performance. The individual MOC strength correlated with behavioral performance during delayed responses with auditory distractors, but not without them. These results in chinchillas, suggest that MOC neurons are also recruited by other cognitive functions, such as working memory.

Investigational Medicinal Products for the Inner Ear: Review of Clinical Trial Characteristics in ClinicalTrials.gov

BACKGROUND

The previous 30 years have provided information on the mechanisms of cell death in the inner ear after noise exposure, ototoxic drug injury, and during aging, and clinical trials have emerged for all of these acquired forms of hearing loss. Sudden hearing loss is less well understood, but restoration of hearing after sudden hearing loss is also a long-standing drug target, typically using steroids as an intervention but with other agents of interest as well.

PURPOSE

The purpose of this review was to describe the state of the science regarding clinical testing of investigational medicinal products for the inner ear with respect to treatment or prevention of acquired hearing loss.

DATA COLLECTION AND ANALYSIS

Comprehensive search and summary of clinical trials listed in the National Library of Medicine (www.

CLINICALTRIALS

gov) database identified 61 clinical trials.

RESULTS

Study phase, status, intervention, and primary, secondary, and other outcomes are summarized for studies assessing prevention of noise-induced hearing loss, prevention of drug-induced hearing loss, treatment of stable sensorineural hearing loss, and treatment of sudden sensorineural hearing loss.

CONCLUSION

This review provides a comprehensive summary of the state of the science with respect to investigational medicinal products for the inner ear evaluated in human clinical trials, and the current challenges for the field.

Measuring Distortion-Product Otoacoustic Emission With a Single Loudspeaker in the Ear: Stimulus Design and Signal Processing Techniques

The distortion-product otoacoustic emission (DPOAE) is a backward propagating wave generated inside the cochlea during the wave amplification process. The DPOAE signal can be detected rapidly under relatively noisy conditions. In recent years, the earphone industry demonstrated interest in adopting DPOAE as an add-on feature to make their product “intelligent” of inner-ear status. However, a technical challenge remains to be tackled—the loudspeaker in an earphone generates its own cubic distortion at the same frequency as DPOAE. Unfortunately, the intensity of loudspeaker distortion is typically comparable to that of the DPOAE, if not higher. In this research, we propose two strategies, namely compensation and cancellation, to enable DPOAE measurement with a single loudspeaker. The compensation strategy exploits the part of the growth function of the loudspeaker distortion which is almost linear, and thus suppresses the distortion it generates while retaining a larger portion of DPOAE in the residual signal. The cancellation strategy utilizes a one-dimensional Volterra filter to remove the cubic distortion from the loudspeaker. Testing on normal-hearing ears shows that the compensation strategy improved the DPOAE-to-interference ratio by approximately 7 dB, resulting in a cross-correlation of 0.62 between the residual DPOAE level and the true DPOAE level. Meanwhile, the cancellation strategy directly recovered both the magnitude and the phase of DPOAE, reducing the magnitude estimation error from 15.5 dB to 3.9 dB in the mean-square sense. These pilot results suggest that the cancellation strategy may be suitable for further testing with more subjects.

Keypoints to Successful Newborn Hearing Screening. Thirty Years of Experience and Innovations

Congenital deafness is a major pediatric problem, affecting about 1.5–3 per 1000 newborns. The early treatment through cochlear implantation and auditory rehabilitation has been a historic milestone. Early diagnosis of congenital deafness is an essential requirement to obtain the best results, which is achieved through neonatal screening, a diagnostic practice that we began systematically at the Hospital Clínico in Valencia (Spain) 30 years ago. Neonatal hearing screening is successful in most developed countries. Its implementation has been slow due to the multiple difficulties that its universal application entails since it involves several health professionals and must be carried out, in a short time interval after birth. In addition, it must have a good performance that prevents the overload of other services and that requires experience and continuous adjustments in search of proper protocols. The aim of this review is to shed some light on some key points of neonatal hearing screening, highlighting our experience in the solutions to common problems. We will discuss about techniques, protocols and neonatal or nutritional factors that can influence the screening results. To a summary of our work, an update on the subject is provided with the intention of sharing experiences and facilitating the start-up of the new units.

Auditory biophysics of endolymphatic hydrops

Audiological tests in patients with Menière's disease reveal abnormal patterns relevant for diagnostic purposes with some success. Electrocochleography, otoacoustic emissions and immittance measurements share a moderate sensitivity but a good specificity. Their potential for monitoring the patients suggests means to understand the characteristic time course of Menière's disease and the pathophysiology behind its attacks. Besides, magnetic resonance imaging now allows direct evaluation of endolymphatic hydrops. One issue is now to understand the links between volume inflation of endolymphatic spaces, which sometimes remains asymptomatic, and the functional signs, in the hope that a better understanding of what triggers the attacks may guide future treatments. This article provides a short review of the possible biophysical significance of audiological tests of Menière's disease, and of the attempts to make sense of functional and imaging data and of the patterns they form when combined.

Otoferlin Is Required for Proper Synapse Maturation and for Maintenance of Inner and Outer Hair Cells in Mouse Models for DFNB9

Deficiency of otoferlin causes profound prelingual deafness in humans and animal models. Here, we closely analyzed developmental deficits and degenerative mechanisms in Otof knock-out (Otof^–/–) mice over the course of 48 weeks. We found otoferlin to be required for proper synapse development in the immature rodent cochlea: In absence of otoferlin, synaptic pruning was delayed, and postsynaptic boutons appeared enlarged at 2 weeks of age. At postnatal day 14 (P14), we found on average ∼15 synapses per inner hair cell (IHC) in Otof^–/– cochleae as well as in wild-type controls. Further on, the number of synapses in Otof^–/– IHCs was reduced to ∼7 at 8 weeks of age and to ∼6 at 48 weeks of age. In the same period, the number of spiral ganglion neurons (SGNs) declined in Otof^–/– animals. Importantly, we found an age-progressive loss of IHCs to an overall number of 75% of wildtype IHCs. The IHC loss more prominently but not exclusively affected the basal aspects of the cochlea. For outer hair cells (OHCs), we observed slightly accelerated age-dependent degeneration from base to apex. This was associated with a progressive decay in DPOAE amplitudes for high frequency stimuli, which could first be observed at the age of 24 weeks in Otof^–/– mice. Our data will help to plan and predict the outcome of a gene therapy applied at various ages of DFNB9 patients.

Comparison of Behavioral and Physiological Measures of the Status of the Cochlear Nonlinearity

While an audiogram is a useful method of characterizing hearing loss, it has been suggested that including a complementary, suprathreshold measure, for example, a measure of the status of the cochlear active mechanism, could lead to improved diagnostics and improved hearing-aid fitting in individual listeners. While several behavioral and physiological methods have been proposed to measure the cochlear-nonlinearity characteristics, evidence of a good correspondence between them is lacking, at least in the case of hearing-impaired listeners. If this lack of correspondence is due to, for example, limited reliability of one of such measures, it might be a reason for limited evidence of the benefit of measuring peripheral compression. The aim of this study was to investigate the relation between measures of the peripheral-nonlinearity status estimated using two psychoacoustical methods (based on the notched-noise and temporal-masking curve methods) and otoacoustic emissions, on a large sample of hearing-impaired listeners. While the relation between the estimates from the notched-noise and the otoacoustic emissions experiments was found to be stronger than predicted by the audiogram alone, the relations between the two measures and the temporal-masking based measure did not show the same pattern, that is, the variance shared by any of the two measures with the temporal-masking curve-based measure was also shared with the audiogram.

Analysis of the Referral Rates of Newborn Hearing Screening Test According to Childbirth Delivery Methods in Neonatal Care Units

It is known that neonates born by cesarean delivery (CD) may have higher referral rates than those born by vaginal delivery (VD) for newborn hearing screening (NHS). False-positive NHS results can increase costs and parental anxiety. This study analyzed the differences in NHS referral rates according to delivery methods in Level I, II, and III neonatal care units. A retrospective chart review was done for 2322 infants (4644 ears) with delivery records who underwent NHS between 2004 and 2017. The first NHS was performed immediately before discharge when the infant was in good condition via the automated auditory brainstem response (AABR) or automated otoacoustic emissions (AOAE). There were 98 neonates (196 ears) who underwent both AABR and AOAE simultaneously as the first NHS, 30 of which failed. We used a total of 4810 ears in this analysis. Of all enrolled ears, 2075 ears were of neonates born by CD, and 2735 ears were of neonates born by VD. A total of 2460 ears were from patients in Level III neonatal intensive care units (NICU) and 2350 ears were from Level I and II neonatal care units. The overall referral rate was higher in infants born via CD (4.5%) than VD (3.2%). In Level I and II neonatal intensive care units, the referral rate was significantly higher in those born via CD (3.0%) than via VD (1.4%). Further, based on the screening method, AABR (75.8%) was more frequently used than AOAE (24.2%), thereby revealing AABR’s higher referral rate in CD (2.9%) than in VD (1.2%). The referral rate of infants who underwent the NHS within three days of birth was higher in the CD group (3.0%) than in the VD group (1.3%). There was no significant difference in the referral rate depending on the delivery method when infants were hospitalized for more than four days or hospitalized in the NICU. The referral rate according to the delivery methods was significantly higher when the NHS test was performed for healthy newborns in the Level I and II neonatal care units born by CD within 72 h using AABR. Therefore, we recommend that the hearing screening test for newborns delivered by cesarean section be performed after 72 h of age. The results of this study may reduce the false-positive NHS results, unnecessary further tests, and parental anxiety.

Decentralising paediatric hearing services through district healthcare screening in Western Cape province, South Africa

Background

Childhood hearing loss is a global epidemic most prevalent in low- and middle-income countries where hearing healthcare services are often inaccessible. Referrals for primary care services to central hospitals add to growing lists and delays the time-sensitive treatment of childhood hearing loss.

Aim

To compare a centralised tertiary model of hearing healthcare with a decentralised model through district hearing screening for children in the Western Cape province, South Africa.

Setting

A central paediatric tertiary hospital in Cape Town and a district hospital in the South Peninsula region.

Methods

A pragmatic quasi-experimental study design was used with a 7-month control period at a tertiary hospital (June 2019 to December 2019). Decentralising was measured by attendance rates, travelling distance, number of referrals to the tertiary hospital and hearing outcomes. There were 315 children in the tertiary group and 158 in the district group. Data were collected from patient records and an electronic database at the tertiary hospital.

Results

Attendance rate at the district hospital was significantly higher (p < 0.001). Travel distance to the district hospital was significantly shorter (p < 0.001). Number of referrals to the tertiary hospital decreased significantly during the intervention period (p < 0.001). Most children in both the tertiary and district groups (78.7% and 80.4%, respectively) passed initial hearing screening bilaterally.

Conclusion

Hearing screening should be conducted at the appropriate level of care to increase access, reduce patient travelling distances and associated costs and reduce the burden on tertiary-level hospitals.

Spatiotemporal Developmental Upregulation of Prestin Correlates With the Severity and Location of Cyclodextrin-Induced Outer Hair Cell Loss and Hearing Loss

2-Hyroxypropyl-beta-cyclodextrin (HPβCD) is being used to treat Niemann-Pick C1, a fatal neurodegenerative disease caused by abnormal cholesterol metabolism. HPβCD slows disease progression, but unfortunately causes severe, rapid onset hearing loss by destroying the outer hair cells (OHC). HPβCD-induced damage is believed to be related to the expression of prestin in OHCs. Because prestin is postnatally upregulated from the cochlear base toward the apex, we hypothesized that HPβCD ototoxicity would spread from the high-frequency base toward the low-frequency apex of the cochlea. Consistent with this hypothesis, cochlear hearing impairments and OHC loss rapidly spread from the high-frequency base toward the low-frequency apex of the cochlea when HPβCD administration shifted from postnatal day 3 (P3) to P28. HPβCD-induced histopathologies were initially confined to the OHCs, but between 4- and 6-weeks post-treatment, there was an unexpected, rapid and massive expansion of the lesion to include most inner hair cells (IHC), pillar cells (PC), peripheral auditory nerve fibers, and spiral ganglion neurons at location where OHCs were missing. The magnitude and spatial extent of HPβCD-induced OHC death was tightly correlated with the postnatal day when HPβCD was administered which coincided with the spatiotemporal upregulation of prestin in OHCs. A second, massive wave of degeneration involving IHCs, PC, auditory nerve fibers and spiral ganglion neurons abruptly emerged 4–6 weeks post-HPβCD treatment. This secondary wave of degeneration combined with the initial OHC loss results in a profound, irreversible hearing loss.

Effect of analgesia with pethidine during labour on false positivity of newborn hearing screening test

OBJECTIVES

Newborn hearing screening may fail due to some perinatal and neonatal factors. False positivity of newborn hearing screening increases costs, familial concerns and anxiety. The objective of this study was to determine the effects of pethidine administered in the mother for labor analgesia on the false positivity rates of the newborn hearing screening test.

METHODS

This study was designed as a retrospective and cross-sectional study. A total of 75 pregnant women scheduled for vaginal delivery who received 50 mg intramuscular pethidine at the beginning of the active phase of the labor were included as the patient group and 68 pregnant women who did not receive pethidine as the control group. A total of 143 infants born with vaginal delivery were evaluated with otoacoustic emission (OAE) test before discharge. Perinatal and neonatal variables and test outcomes were recorded, and the correlation between false positivity rate and pethidine usage was evaluated.

RESULTS

Initially, system records of 148 healthy term newborns were screened. Four patients who failed in both OAE tests and were referred to the Automated Auditory Brainstem Response (AABR) test and one patient who failed in all tests (first OAE, control OAE and AABR) and was referred to an upper center for further investigations and treatment were excluded from the study. No statistically significant difference was found between the groups in terms of birth features. First stage OAE test was reported as 'passed' in 8 (10.7%) and 58 (85.3%) newborns in the study and control groups, respectively; while OAE was reported as 'referred' and 'passed' in the second test in 67 (89.3%) and 10 (14.7%) newborns in the study and control groups, respectively. There was a statistically significant difference between both groups in terms of false positivity ratio (p < 0.5).

CONCLUSION

Pethidine significantly decreases the duration of the active phase, providing a good analgesic effect for pain management during labor. Therefore, it seems that pethidine can be used as an acceptable agent during labor. However, it may have neonatal effects after the delivery, causing false positivity in newborn hearing screening tests. The results of this study support the opinion that the OAE test should be performed in postpartum later dates in order to increase OAE passing rates and minimize costs and parents' concerns.

Assessment of the Hearing Status of School-Age Children from Rural and Urban Areas of Mid-Eastern Poland

(1) Background: The purpose of this study was to assess the prevalence of hearing loss in school-age children from rural and urban areas of mid-eastern Poland using standard audiological tests-pure tone audiometry (PTA), impedance audiometry (IA), and otoacoustic emissions (OAEs). (2) Methods: Data were collected from a group of 250 children aged 8 to 13, made up of 122 children from urban areas and 128 children from rural areas of mid-eastern Poland. Hearing was assessed in each of the subjects by means of PTA, IA (tympanometry), and transient-evoked OAEs (TEOAEs). Otoscopy was also performed. (3) Results: There were significantly fewer abnormal results in children from urban than rural areas: they were, respectively, 10.1% and 23.1% for IA, 3% and 9.7% for PTA, and 17.3% and 31.8% for TEOAEs. For hearing-impaired ears in rural areas (failed TEOAE), hearing thresholds were, on average, 11.5 dB higher at 0.5 kHz than for children in urban areas. Comparison of each PTA result with the corresponding IA showed that all cases of hearing loss were related to malfunction of the middle ear. (4) Conclusions: The results of all three hearing tests were significantly worse in children from rural areas compared to those from urban areas. This indicates that audiological healthcare in rural areas needs improvement and that universal hearing screening programs for school-age children would be helpful.

Factors Affecting Neonatal Hearing Screening Follow-up in Developing Countries: One Insitution Prospective Pilot Study

Objective

To detect factors related with loss to follow-up (LTF) in neonatal hearing screening (NHS) program of one institution in a developing country.

Methods

A prospective study was planned based on the data collected in a pilot study conducted a year before in the same institution. In this pilot study, hearing screening was performed before hospital discharge for every infant (1217 newborns) in six months period. Total referral rate was 19.1% (223/1217). Loss to follow-up (LTF) was 38.1% (85/223). Telephonic interviews were done with 50 parents who had not come with their child to the second hearing test. For these telephonic interviews the questionnaire with four sections (socio-demographic information; information about pregnancy, birth, and present health condition of the child; caregiver knowledge of neonatal hearing screening, and reasons for default on follow-up) was created.

Results

The mothers participated in this study were 29.1 years (±5.2 SD) of age in average. Place of residence was mostly rural (64%; n=32) with 39.4 Km (±24.8 SD) away from from the rescreen referral center. Their knowledge on neonatal hearing screening, hearing impairment incidence or treatment opportunities was at a very low level. Caregivers’ perceptions that follow-up was unnecessary (50%; n=25), was most frequently given reason for follow-up default, followed by newborns bad health condition (12%; n=6) and forgetting about the follow-up visits (8%; n=6).

Conclusion

The main reason for default in follow-up in our study was caregiver’s poor knowledge about this topic.

Medial olivocochlear reflex effects on amplitude growth functions of long- and short-latency components of click-evoked otoacoustic emissions in humans

Functional outcomes of medial olivocochlear reflex (MOCR) activation, such as improved hearing in background noise and protection from noise damage, involve moderate to high sound levels. Previous noninvasive measurements of MOCR in humans focused primarily on otoacoustic emissions (OAEs) evoked at low sound levels. Interpreting MOCR effects on OAEs at higher levels is complicated by the possibility of the middle-ear muscle reflex and by components of OAEs arising from different locations along the length of the cochlear spiral. We overcame these issues by presenting click stimuli at a very slow rate and by time-frequency windowing the resulting click-evoked (CE)OAEs into short-latency (SL) and long-latency (LL) components. We characterized the effects of MOCR on CEOAE components using multiple measures to more comprehensively assess these effects throughout much of the dynamic range of hearing. These measures included CEOAE amplitude attenuation, equivalent input attenuation, phase, and slope of growth functions. Results show that MOCR effects are smaller on SL components than LL components, consistent with SL components being generated slightly basal of the characteristic frequency region. Amplitude attenuation measures showed the largest effects at the lowest stimulus levels, but slope change and equivalent input attenuation measures did not decrease at higher stimulus levels. These latter measures are less commonly reported and may provide insight into the variability in listening performance and noise susceptibility seen across individuals.NEW & NOTEWORTHY The auditory efferent system, operating at moderate to high sound levels, may improve hearing in background noise and provide protection from noise damage. We used otoacoustic emissions to measure these efferent effects across a wide range of sound levels and identified level-dependent and independent effects. Previous reports have focused on level-dependent measures. The level-independent effects identified here may provide new insights into the functional relevance of auditory efferent activity in humans.

Muscles in and around the ear as the source of "physiological noise" during auditory selective attention: A review and novel synthesis

The sensitivity of the auditory system is regulated via two major efferent pathways: the medial olivocochlear system that connects to the outer hair cells, and by the middle ear muscles-the tensor tympani and stapedius. The role of the former system in suppressing otoacoustic emissions has been extensively studied, but that of the complementary network has not. In studies of selective attention, decreases in otoacoustic emissions from contralateral stimulation have been ascribed to the medial olivocochlear system, but the acknowledged problem is that the results can be confounded by parallel muscle activity. Here, the potential role of the muscle system is examined through a wide but not exhaustive review of the selective attention literature, and the unifying hypothesis is made that the prominent "physiological noise" detected in such experiments, which is reduced during attention, is the sound produced by the muscles in proximity to the ear-including the middle ear muscles. All muscles produce low-frequency sound during contraction, but the implications for selective attention experiments-in which muscles near the ear are likely to be active-have not been adequately considered. This review and synthesis suggests that selective attention may reduce physiological noise in the ear canal by reducing the activity of muscles close to the ear. Indeed, such an experiment has already been done, but the significance of its findings have not been widely appreciated. Further sets of experiments are needed in this area.

Efferent unmasking of speech-in-noise encoding?

OBJECTIVE

The medial olivocochlear (MOC) reflex provides efferent feedback from the brainstem to cochlear outer hair cells. Physiologic studies have demonstrated that the MOC reflex is involved in "unmasking" of signals-in-noise at the level of the auditory nerve; however, its functional importance in human hearing remains unclear.

DESIGN

This study examined relationships between pre-neural measurements of MOC reflex strength (click-evoked otoacoustic emission inhibition; CEOAE) and neural measurements of speech-in-noise encoding (speech frequency following response; sFFR) in four conditions (Quiet, Contralateral Noise, Ipsilateral Noise, and Ipsilateral + Contralateral Noise). Three measures of CEOAE inhibition (amplitude reduction, effective attenuation, and input-output slope inhibition) were used to quantify pre-neural MOC reflex strength. Correlations between pre-neural MOC reflex strength and sFFR "unmasking" (i.e. response recovery from masking effects with activation of the MOC reflex in time and frequency domains) were assessed.

STUDY SAMPLE

18 young adults with normal hearing.

RESULTS

sFFR unmasking effects were insignificant, and there were no correlations between pre-neural MOC reflex strength and sFFR unmasking in the time or frequency domain.

CONCLUSION

Our results do not support the hypothesis that the MOC reflex is involved in speech-in-noise neural encoding, at least for features that are represented in the sFFR at the SNR tested.

Comparison of Two-Step Transient Evoked Otoacoustic Emissions and One-Step Automated Auditory Brainstem Response for Universal Newborn Hearing Screening Programs in Remote Areas of China

Objective: To compare the hearing screening results of two-step transient evoked otoacoustic emissions (TEOAE) and one-step automatic auditory brainstem response (AABR) in non-risk newborns, and to explore a more suitable hearing screening protocol for infants discharged within 48 h after birth in remote areas of China. Methods: To analyze the age effect on pass rate for hearing screening, 2005 newborns were divided into three groups according to screening time after birth: <24, 24-48, and 48-72 h. All subjects received TEOAE + AABR test as first hearing screen, and those who failed in any test were rescreened with TEOAE + AABR at 6 weeks after birth. The first screening results of AABR and TEOAE were compared among the three groups. The results of two-step TEOAE screening and one-step AABR screening were compared for newborns who were discharged within 48 h. The time spent on screening was recorded for TEOAE and AABR. Results: The pass rate of TEOAE and AABR increased significantly with the increase of first screening time (P < 0.05), and the false positive rate decreased significantly with the increase of first screening time (P < 0.05). The failure rate of first screening of AABR within 48 h was 7.31%, which was significantly lower than that of TEOAE (9.93%) (P < 0.05). The average time spent on AABR was 12.51 ± 6.36 min, which was significantly higher than that of TEOAE (4.05 ± 1.56 min, P < 0.05). The failure rate of TEOAE two-step screening was 1.59%, which was significantly lower than one-step AABR. Conclusions: Compared with TEOAE, AABR screening within 48 h after birth can reduce the failure rate and false positive rate of first screening. However, compared with TEOAE two-step screening, one-step AABR screening has higher referral rate for audiological diagnosis. In remote areas of China, especially in hospitals with high delivery rate, one-step AABR screening is not feasible, and two-step TEOAE screening protocol is still applicable to UNHS screening as more and more infants discharged within 48 h after birth.

Occupational Noise: Auditory and Non-Auditory Consequences

Occupational noise exposure accounts for approximately 16% of all disabling hearing losses, but the true value and societal costs may be grossly underestimated because current regulations only identify hearing impairments in the workplace if exposures result in audiometric threshold shifts within a limited frequency region. Research over the past several decades indicates that occupational noise exposures can cause other serious auditory deficits such as tinnitus, hyperacusis, extended high-frequency hearing loss, and poor speech perception in noise. Beyond the audiogram, there is growing awareness that hearing loss is a significant risk factor for other debilitating and potentially life-threatening disorders such as cardiovascular disease and dementia. This review discusses some of the shortcomings and limitations of current noise regulations in the United States and Europe.

No Change in Medial Olivocochlear Efferent Activity during an Auditory or Visual Task: Dual Evidence from Otoacoustic Emissions and Event-Related Potentials

The medial olivocochlear (MOC) system is thought to be responsible for modulation of peripheral hearing through descending (efferent) pathways. This study investigated the connection between peripheral hearing function and conscious attention during two different modality tasks, auditory and visual. Peripheral hearing function was evaluated by analyzing the amount of suppression of otoacoustic emissions (OAEs) by contralateral acoustic stimulation (CAS), a well-known effect of the MOC. Simultaneously, attention was evaluated by event-related potentials (ERPs). Although the ERPs showed clear differences in processing of auditory and visual tasks, there were no differences in the levels of OAE suppression. We also analyzed OAEs for the highest magnitude resonant mode signal detected by the matching pursuit method, but again did not find a significant effect of task, and no difference in noise level or number of rejected trials. However, for auditory tasks, the amplitude of the P3 cognitive wave negatively correlated with the level of OAE suppression. We conclude that there seems to be no change in MOC function when performing different modality tasks, although the cortex still remains able to modulate some aspects of MOC activity.

Pharmaco-Audiology Vigilance in the Treatment of Adult Patients with HIV/Aids: Ototoxicity Monitoring Protocol Recommendation

South Africa is considered the epicenter of HIV/AIDS with a high rate of TB infection as well. Links have been established between treatments of these conditions to ototoxicity. However, no standardized and systematic ototoxicity monitoring exists within the clinical sites where these conditions are treated, with very minimal and adhoc involvement of audiologists as part of the treatment team. With 3.4 million HIV-infected South Africans being reported to have been on antiretroviral drugs by the end of March 2016; with universal coverage being the target, it is important that ototoxicity monitoring becomes part of the treatment plan. The objective of the current paper is to propose an ototoxicity monitoring protocol that can be implemented within this population to ensure that systematic data are collated in order for evidence-based protocols to be adopted within the South African context. Such a protocol will also allow for early identification and intervention of ototoxic hearing loss within this population. Enough evidence exists to support implementation of standardized protocols that will allow for proper, accurate, efficient, and reliable comparisons of data within and between patients; as well as between and within treatment sites - both locally and internationally. It is hoped that implementation of such a monitoring protocol will also have significant implications for the expanded role of the audiologist in the drug development process, affording evidence-based benefit-risk assessments of drugs in the market for this population.

Lateralization of cochlear dysfunction as a specific biomarker of Parkinson's disease

In the last decade, animal studies highlighted the sensitivity of hearing function to lack of specific cochlear dopamine receptors, while several studies on humans reported association between hearing loss and Parkinson's disease, partially recovered after levodopa administration in de novo patients. Taken together, these observations suggest investigating the possible use of cochlear function outcome variables, particularly, otoacoustic emissions, as sensitive biomarkers of Parkinson's disease. Any lateralization of hearing dysfunction correlated with Parkinson's disease lateralization would (i) further confirm their association and (ii) provide a disease-specific differential outcome variable. Differential indicators are particularly useful for diagnostic purposes, because their effectiveness is not limited by physiological inter-subject fluctuations of the outcome variable. Recent advances in the acquisition and analysis techniques of otoacoustic emissions suggest using them for evaluating differential cochlear damage in the two ears. In this study, we quantitatively evaluated hearing function in a population of subjects with Parkinson's disease, to investigate the occurrence of hearing loss, and, particularly, whether hearing dysfunction shows lateralization correlated with motor symptoms. Pure tone audiometry and distortion product otoacoustic emissions were used as outcome variables in 80 patients (mean age 65 ± 9 years) and 41 controls (mean age 64 ± 10 years). An advanced customized acquisition and analysis system was developed and used for otoacoustic testing, which guarantees response stability independent of probe insertion depth, and has the sensitivity necessary to accurately assess the low levels of otoacoustic response typical of elderly subjects. To our knowledge, this is the first study introducing the distinction between ipsilateral and contralateral ear, with respect to the body side more affected by Parkinson's disease motor symptoms. Significant asymmetry was found in the auditory function, as both otoacoustic responses and audiometric hearing levels were worse in the ipsilateral ear. Significantly worse hearing function was also observed in patients with Parkinson's disease compared to controls, confirming previous studies. Several pathophysiological mechanisms may be hypothesized to explain asymmetric cochlear damage in Parkinson's disease, including the impairment of dopamine release and the involvement of extra-dopaminergic circuits, with the cholinergic pathway as a likely candidate. The observed asymmetry in the audiological response of patients with Parkinson's disease suggests that lateralization of hearing dysfunction could represent a specific non-motor signature of the disease. The possible diagnostic use of cochlear dysfunction asymmetry as a specific biomarker of Parkinson's disease deserves further investigation, needing a more precise quantitative assessment, which would require a larger sample size.

Breastfeeding results in better hearing in newborns compared to bottle-feeding

BACKGROUND AND AIM

Transient evoked otoacoustic emissions (TEOAEs) are a validated technique in newborn hearing screening that is regularly used in many countries. It reflects normal hearing or at least no more than 30 dB HL hearing loss. Breastfeeding has many advantages and some studies have demonstrated that it prevents otitis media by means of opening the Eustachian tube and clearing mucus in the middle ear which is perhaps also combined with immunological effects. A few studies have related how newborn feeding can vary the pass rate to TEOAE. The goal of this study was to investigate the relationship between newborn feeding and TEOAE newborn hearing screening results.

METHODS

Data were retrospectively collected from healthy vaginally delivered newborns of gestational age >37 weeks and body weight > 2.5 kg at the maternity ward. Newborn feeding history was compared with the pass rate to TEOAE performed within the 1st 48 h of life.

RESULTS

The study group included 12,866 newborns. In this group, significant differences were found based on the feeding method (breastfeeding was found to be better than formula, P<0.0001).

CONCLUSIONS

Breastfeeding improves newborn hearing screening results with TEOAE.

RELEVANCE FOR PATIENTS

Lies in the fact that breastfed children respond better to the test and need to repeat it fewer times, avoiding problems such as loss to follow-up and additional work.

Does noise exposure during pregnancy affect neonatal hearing screening results?

Objective

The aim is to investigate whether noise is effective on hearing screening tests of neonates born to mothers exposed to noise during pregnancy.

Material and Method

Screening results of 2653 infants from the period of January 2013-May 2017 were evaluated. Transient Evoked Otoacoustic Emissions (TEOAE) and Auditory Brainstem Response (ABR) were used. Infants of 65 mothers exposed to noise (L_Aeq 80-85 dBA/8 hours/day) during pregnancy (Week ± SD; 32.58 ± 2.71) comprised the study group while the control group consisted of infants of 2588 mothers without noise exposure.

Results

Among the 65 infants, 23 (35.4%) passed screening at the first emission test (OAE1); 34 (52.3%) at the second emission test (OAE2); 7 (10.8%) at the ABR stage, 1 (1.5%) infant was referred to a tertiary center. In the control group, 458 (17.7%) infants passed at OAE1; 1822 (70.4%) at OAE2; 289 (11.2%) at ABR stages, 19 (0.7%) infants were referred to a tertiary center. The rate of infants that passed screening at OAE1 in the study group was high (P = 0.00001). Sixty-four (98.46%) infants in the study group and 2569 (99.26%) infants in the control group passed the tests. The difference between the two groups was not significant, indicating that exposure to noise during pregnancy had no unfavorable effects on auditory functions (P = 0.392).

Conclusion

Unfavorable effect of noise exposure during pregnancy was not observed on auditory functions of the infants. The higher rate of infants that passed the screening test at OAE1 stage in the study group raised the question, "Does the exposure of the noise at exposure action levels (80-85 dB A) during pregnancy contribute to auditory maturation of fetus?"

Future Perspectives on the Relevance of Auditory Markers in Prodromal Parkinson's Disease

Research on auditory processing in Parkinson's disease (PD) has recently made substantial progress. At present, evidence has been found for altered auditory processing in the clinical stage of PD. The auditory alterations in PD have been demonstrated with low-cost and non-invasive assessments that are already used in routine clinical practice. Since auditory alterations have been reported early in disease progression, it would be highly relevant to investigate whether auditory markers could be provided in the prodromal stage of PD. In addition, auditory alterations in early stage PD might be modulated by dopaminergic medication. Therefore, the aim of this review is (1) to summarize the literature on auditory processing in PD with a specific focus on the early disease stages, (2) to give future perspectives on which audiological and electrophysiological measurements could be useful in the prodromal stage of PD and (3) to assess the effect of dopaminergic medication on potential auditory markers in the prodromal stage of PD.

Detection of Age-Related Hearing Losses (ARHL) via Transient-Evoked Otoacoustic Emissions

PURPOSE

The objective of the study was to identify subjects presenting hearing deficits, specifically age-related hearing losses (ARHL), via objective assessment methodologies.

MATERIALS AND METHODS

Initially, 259 subjects (165 men, 94 women) were enrolled in the study. After the application of inclusion criteria, the final number was reduced to 88 subjects (49.8 ± 19.1 ys) subdivided into 64 normal and 83 ARHL cases. The subjects were assessed with traditional audiometry tests and with transiently evoked otoacoustic emissions (TEOAEs). Since each ear has its own acoustic signature, the TEOAE analyses were conducted in terms of ears and not subjects. The TEOAE data were processed by traditional and recurrence quantification analyses, leading to the estimation of the WWR (whole waveform reproducibility) and the new RAD2D (2-dimensional radius) parameters. A plot of WWR vs RAD2D was used to optimize the classification of the cases presenting ARHL.

RESULTS

By using a WWR value of 70% as a classifier, the sensitivity of TEOAEs was estimated as 75.9% and the specificity as 89.1%. By using the RAD2D parameter (with a cut-off value of 1.78), a sensitivity value of 80.7% and a specificity value of 71.9% were obtained. When both parameters were used, a sensitivity value of 85.5% and a specificity value of 92.2% were estimated. In the latter classification paradigm, the number of false negatives decreased from 20 to 12 out of 83 ears (14%).

CONCLUSION

In adult hearing screening assessments, the proposed method optimizes the identification of subjects with a hearing impairment correlated to the presence of age-related hearing loss.