Auditory Effects of Acoustic Noise From 3-T Brain MRI in Neonates With Hearing Protection

BACKGROUND

Neonates with immature auditory function (eg, weak/absent middle ear muscle reflex) could conceivably be vulnerable to noise-induced hearing loss; however, it is unclear if neonates show evidence of hearing loss following MRI acoustic noise exposure.

PURPOSE

To explore the auditory effects of MRI acoustic noise in neonates.

STUDY TYPE

Prospective.

SUBJECTS

Two independent cohorts of neonates (N = 19 and N = 18; mean gestational-age, 38.75 ± 2.18 and 39.01 ± 1.83 weeks).

FIELD STRENGTH/SEQUENCE

T1-weighted three-dimensional gradient-echo sequence, T2-weighted fast spin-echo sequence, single-shot echo-planar imaging-based diffusion-tensor imaging, single-shot echo-planar imaging-based diffusion-kurtosis imaging and T2-weighted fluid-attenuated inversion recovery sequence at 3.0 T.

ASSESSMENT

All neonates wore ear protection during scan protocols lasted ~40 minutes. Equivalent sound pressure levels (SPLs) were measured for both cohorts. In cohort1, left- and right-ear auditory brainstem response (ABR) was measured before (baseline) and after (follow-up) MRI, included assessment of ABR threshold, wave I, III and V latencies and interpeak interval to determine the functional status of auditory nerve and brainstem. In cohort2, baseline and follow-up left- and right-ear distortion product otoacoustic emission (DPOAE) amplitudes were assessed at 1.2 to 7.0 kHz to determine cochlear function.

STATISTICAL TEST

Wilcoxon signed-rank or paired t-tests with Bonferroni's correction were used to compare the differences between baseline and follow-up ABR and DPOAE measures.

RESULTS

Equivalent SPLs ranged from 103.5 to 113.6 dBA. No significant differences between baseline and follow-up were detected in left- or right-ear ABR measures (P > 0.999, Bonferroni corrected) in cohort1, or in DPOAE levels at 1.2 to 7.0 kHz in cohort2 (all P > 0.999 Bonferroni corrected except for left-ear levels at 3.5 and 7.0 kHz with corrected P = 0.138 and P = 0.533).

DATA CONCLUSION

A single 40-minute 3-T MRI with equivalent SPLs of 103.5-113.6 dBA did not result in significant transient disruption of auditory function, as measured by ABR and DPOAE, in neonates with adequate hearing protection.

EVIDENCE LEVEL

2.

TECHNICAL EFFICACY

Stage 5.

Pre-registered controlled comparison of auditory function reveals no difference between hospitalised adults with and without COVID-19

OBJECTIVE

Several viruses are known to have a negative impact on hearing health. The global prevalence of COVID-19 means that it is crucial to understand whether and how SARS-CoV2 affects hearing. Evidence to date is mixed, with studies frequently exhibiting limitations in the methodological approaches used or the populations sampled, leading to a substantial risk of bias. This study addressed many of these limitations.

DESIGN

A comprehensive battery of measures was administered, including lab-based behavioural and physiological measures, as well as self-report instruments. Performance was thoroughly assessed across the auditory system, including measures of cochlear function, neural function and auditory perception. Hypotheses and analyses were pre-registered.

STUDY SAMPLES

Participants who were hospitalised as a result of COVID-19 (n = 57) were compared with a well-matched control group (n = 40) who had also been hospitalised but had never had COVID-19.

RESULTS

We find no evidence to support the hypothesis that COVID-19 is associated with deficits in auditory function on any auditory test measure. Of all the confirmatory analyses, only the self-report measure of hearing decline indicated any difference between groups.

CONCLUSION

Results do not support the hypothesis that COVID-19 infection has a significant long-term impact on the auditory system.

Potential application value of pigment epithelium-derived factor in sensorineural hearing loss

The inner ear is a complex and precise auditory perception system responsible for receiving and converting sound signals into neural signals, enabling us to perceive and understand sound. However, the occurrence and development of inner ear diseases and auditory disorders, such as sensorineural hearing loss, remain a global problem. In recent years, there has been increasing research on the treatment of inner ear diseases and auditory regeneration. Among these treatments, pigment epithelium-derived factor (PEDF), as a multifunctional secretory protein, exhibits diverse biological activities and functions through various mechanisms, and has shown potential applications in the inner ear. This minireview comprehensively evaluates the performance of PEDF in sensorineural hearing loss in inner ear and its potential targets and therapeutic prospects.

The auditory function in migraine model rats induced by postauricular nitroglycerin injection

Objective

The mechanism by which migraines produce inner ear-related symptoms is not well understood. Previous studies have found that the latency of auditory brainstem response (ABR) in animal models of migraine has changed, but the threshold has not changed significantly. Therefore, it is necessary to establish a better animal model with both migraine and hearing loss to explore the relationship between migraine and auditory function deeply.

Methods

In this study, the rat model of migraine was induced by postauricular injection of nitroglycerin (NTG), and the effect on the auditory function of the inner ear was explored by comparing with intraperitoneal injection of nitroglycerin. The rats were given the drug repeatedly on alternate days, a total of 5 dosing, with the body weight monitored during the drug administration. The tactile threshold of the rats' forepaw was measured using von-Frey filaments and auditory function was assessed by ABR.

Results

The results showed that the baseline tactile threshold of rats gradually decreased during the modeling process, and hyperalgesia appeared. Postauricular injection of NTG did not affect the weight gain of rats, while intraperitoneal injection of NTG showed slow or even negative weight gain. The ABR threshold of Click, 4 and 8 kHz of postauricular NTG injection rats increased, the latency was prolonged, and the ABR threshold in the right ear was higher than that in the left ear.

Conclusions

We demonstrated that postauricular injection of nitroglycerin may be safer and more effective than intraperitoneal injection of nitroglycerin in the process of creating rat migraine model without affecting the weight gain. Postauricular injection of nitroglycerin has more damage to the auditory function of rats. Therefore, the migraine model rat induced by postauricular injection of nitroglycerin may be a new model of cochlear migraine.

Quantitative Threshold Determination of Auditory Brainstem Responses in Mouse Models

The auditory brainstem response (ABR) is a scalp recording of potentials produced by sound stimulation, and is commonly used as an indicator of auditory function. However, the ABR threshold, which is the lowest audible sound pressure, cannot be objectively determined since it is determined visually using a measurer, and this has been a problem for several decades. Although various algorithms have been developed to objectively determine ABR thresholds, they remain lacking in terms of accuracy, efficiency, and convenience. Accordingly, we proposed an improved algorithm based on the mutual covariance at adjacent sound pressure levels. An ideal ABR waveform with clearly defined waves I-V was created; moreover, using this waveform as a standard template, the experimentally obtained ABR waveform was inspected for disturbances based on mutual covariance. The ABR testing was repeated if the value was below the established cross-covariance reference value. Our proposed method allowed more efficient objective determination of ABR thresholds and a smaller burden on experimental animals.

Sex differences and the effect of female sex hormones on auditory function: a systematic review

Aims

First, to discuss sex differences in auditory function between women and men, and whether cyclic fluctuations in levels of female sex hormones (i.e., estradiol and progesterone) affect auditory function in pre-menopausal and post-menopausal women. Second, to systematically review the literature concerning the discussed patterns in order to give an overview of the methodologies used in research. Last, to identify the gap in knowledge and to make recommendations for future work.

Methods for the systematic review

Population, Exposure, Control, Outcome and Study design (PECOS) criteria were used in developing the review questions. The review protocol follows the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was pre-registered in the Prospective Register of Systematic Reviews (PROSPERO; CRD42020201480). Data Sources: EMBASE, PubMed, MEDLINE (Ovid), PsycINFO, ComDisDome, CINAHL, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL) via Cochrane Library, and scanning reference lists of relevant studies, and internet resources (i.e., Mendeley) were used. Only studies published between 1999 and 2022, in English, or in English translation, were included. The quality of evidence was assessed using the Newcastle-Ottawa Scale (NOS).

Results

Sex differences: Women had more sensitive hearing (measured at the level of peripheral and central auditory system) than men. Cyclic fluctuations: Auditory function in women fluctuated during the menstrual cycle, while no such fluctuations in men over the same time period were reported. Hearing sensitivity improved in women during the late follicular phase, and decrease during the luteal phase, implying an effect of female sex hormones, although the specific effects of estradiol and progesterone fluctuations on the central auditory system remain unclear. Hearing sensitivity in women declined rapidly at the onset of menopause.

Conclusion

The review has shown the following. Consistent sex differences exist in auditory function across the auditory pathway with pre-menopausal women often showing better function than age-matched men. Moreover, pre-menopausal women show fluctuations in hearing function across the menstrual cycle with a better function during the peak of estradiol or when the ratio of estradiol to progesterone is high. Third, menopause marks the onset of hearing loss in women, characterized by a rapid decline in hearing sensitivity and a more pronounced loss than in age-matched men. Finally, the systematic review highlights the need for well-designed and -controlled studies to evaluate the influence of estradiol and progesterone on hearing by consistently including control groups (e.g., age-matched man), using objective tests to measure hormonal levels (e.g., in saliva or blood), and by testing participants at different points across the menstrual cycle.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020201480, identifier CRD42020201480.

Intraoperative brainstem auditory evoked potential monitoring during cerebellopontine angle surgery via retrosigmoid approach

OBJECTIVES

Brainstem auditory evoked potential (BAEP) monitoring was used to identify the influence of auditory function during cerebellopontine angle (CPA) surgery for cranial neuropathy via the retrosigmoid approach.

METHODS

This prospective study included 20 patients who underwent CPA surgery for cranial neuropathy via the retrosigmoid approach with intraoperative BAEP monitoring and pure tone audiometry (PTA). The latency and interpeak latency were analyzed at each surgical step in combination with the pre- and postoperative PTA.

RESULTS

Follow-up data were available for 17 patients. The mean pre- and postoperative PTA values were 25.65 dB and 20.70 dB, respectively. Two patients (2/17, 11.76%) developed hearing loss postoperatively. The latency of wave І significantly changed during direct auditory nerve manipulation and at the end of the surgery, while that of wave III only changed during direct auditory nerve manipulation. The appearance of wave V peak was delayed during CPA surgery.

CONCLUSIONS

CPA surgery for cranial neuropathy via the retrosigmoid approach can cause hearing loss to varying degrees, and intraoperative BAEP monitoring can reduce the occurrence of hearing loss. Intraoperative hearing function can be estimated by the latency of wave I. Hearing loss due to stretching of the brainstem can be estimated by the latency of wave III, and wave V is an early indicator of intraoperative hearing loss. Waves I and III remained stable both pre- and postoperatively, whereas wave V was unstable despite no surgery. Therefore, a precise operation and well-defined operative steps for surgeons during CPA surgery could facilitate maximal preservation of the anatomical structure and function.

Hearing loss in mice with disruption of auditory epithelial patterning in the cochlea

In the cochlear auditory epithelia, sensory hair and supporting cells are arranged in a checkerboard-like mosaic pattern, which is conserved across a wide range of species. The cell adhesion molecules nectin-1 and nectin-3 are required for this pattern formation. The checkerboard-like pattern is thought to be necessary for auditory function, but has never been examined. Here, we showed the significance of checkerboard-like cellular pattern in the survival and function of sensory hair cells in the cochlear auditory epithelia of nectin-3 knockout (KO) mice. Nectin-3 KO mice showed progressive hearing loss associated with degeneration of aberrantly attached hair cells via apoptosis. Apoptotic hair cell death was due to the disorganization of tight junctions between the hair cells. Our study revealed that the checkerboard-like cellular pattern in the auditory epithelium provides a structural basis for ensuring the survival of cochlear hair cells and hearing function.

[Research progress on non-surgical treatment of vestibular schwannomas]

At present, the main treatment for vestibular schwannomas is surgery. Considering the risk of multiple complications from surgery and the subjective and objective conditions of patients, a non-surgical treatment modality, namely stereotactic radiotherapy, has gradually been included in the treatment of vestibular schwannomas. Studies have shown that Gamma Knife therapy has a more prominent therapeutic effect on smaller tumors and can alleviate facial nerve disorders caused by space occupying of tumor mass. Cyberknife not only has a better effect on tumor control, but also has an ideal retention rate for patients' auditory function. Proton beam therapy has also been gradually applied to the treatment of vestibular schwannomas, but the effect of treatment remains to be further studied. Drug therapy includes a variety of target inhibitors and anti-angiogenic drugs. At present, drug treatment focuses more on preclinical research. This article reviews the clinical research of various radiotherapy and the progress of drug treatment.

MicroRNA expression is associated with auditory dysfunction in workers exposed to ototoxic solvents and noise

This study is part of a project on early hearing dysfunction induced by combined exposure to volatile organic compounds (VOCs) and noise in occupational settings. In a previous study, 56 microRNAs were found differentially expressed in exposed workers compared to controls. Here, we analyze the statistical association of microRNA expression with audiometric hearing level (HL) and distortion product otoacoustic emission (DPOAE) level in that subset of differentially expressed microRNAs. The highest negative correlations were found; for HL, with miR-195-5p and miR-122-5p, and, for DPOAEs, with miR-92b-5p and miR-206. The homozygous (mut) and heterozygous (het) variants of the gene hOGG1 were found disadvantaged with respect to the wild-type (wt), as regards the risk of hearing impairment due to exposure to VOCs. An unsupervised artificial neural network (auto contractive map) was also used to detect and show, using graph analysis, the hidden connections between the explored variables. These findings may contribute to the formulation of mechanistic hypotheses about hearing damage due to co-exposure to noise and ototoxic solvents.

[Effects of GLAST gene knockout on phenotype and hearing in mice]

OBJECTIVE

To investigate the effects of glutamate aspartate transporter (GLAST)deletion on the normal auditory function of mice.

METHODS

We hybridized GLAST^+/- mice with C57BL/6J background and identified the genotypes of their offspring by agarose gel electrophoresis. 9-10-week-old mice were selected to detect the expression of GLAST protein in the cochlea by immunofluorescence staining and to verify the knockout results(n=3). The changes in weight from 7 days to 30 days after birth and the 30-day body length of male and female mice were compared(n=8). The auditory brainstem response(ABR) was used to detect the auditory threshold and the amplitude of wave I in 9-10-week-old male and female mice(n=5).

RESULTS

Male GLAST^-/- mice had shown significantly lower weight and body length compared to male GLAST^+/+ and GLAST^+/- mice(P＜0.01), and male GLAST^-/- mice showed significant differences compared to GLAST^+/+ from P7 to P30 statistical time. Male GLAST^-/- mice exhibited a significant reduction in weight after P15 compared to male GLAST^+/- mice. In contrast, no significant differences in weight and body length were observed in female GLAST^-/- mice compared with female GLAST^+/+ and GLAST^+/- mice. There was no difference in the hearing threshold detected by ABR between the three genotypes in both male and female mice, but the amplitude of wave I in GLAST^-/- mice was significantly lower than that in male GLAST^+/+ mice(P＜0.01). In contrast, the amplitude of wave I in females was reduced throughout the stimulus intensity but was most significant only at high-intensity stimulation (e.g.80 dB, 90 dB) (P＜0.05).

CONCLUSION

GLAST knockout affects the normal growth and development of male mice, and decreases the amplitude of wave I, but do not change the threshold, suggesting that GLAST knockout may lead to synaptic pathological changes, and there are gender differences in this effect.

Assessment of auditory functions in patients with hepatic glycogen storage diseases

BACKGROUND

Hepatic glycogen storage diseases are a group of diseases manifesting mainly with hypoglycemia and hepatomegaly. The patients require frequent daytime and nocturnal feedings. Hypoglycemia may cause sensorineural hearing loss and nocturnal feeding is a risk factor for the development of gastroesophageal reflux that may cause chronic otitis media and hearing loss consequently. We aimed to determine the prevalence and characteristics of hearing loss in hepatic glycogen storage diseases.

METHODS

A total of 24 patients with hepatic glycogen storage disease (15 glycogen storage disease type I and 9 non type I) and 24 age/sex matched healthy controls were enrolled in the study. Pure tone audiometer, immitansmetry, acoustic reflex measurement, otoacoustic emission test (OAE) and auditory brainstem response (ABR) tests were applied to all participants.

RESULTS

Hearing loss was determined in 17/24 patients (12 glycogen storage disease type I and 5 non type I) with pure tone audiometer. Interpretation of all the findings revealed a total of 8 patients had conductive and 9 had mixed hearing loss. All parameters were significantly different than the control group.

CONCLUSIONS

This is the first study to comprehensively assess the auditory functions of patients with hepatic glycogen storage disease. Audiological findings determined a significantly increased prevalence of conductive/ mixed type hearing loss in the patient group which is a new finding in the literature. Further studies with extended patient numbers are required to enlighten the underlying pathophysiology.

[Common tools of auditory function assessment in infants and toddlers]

With the prevalence of early hearing detection and intervention program in China, more and more infants and toddlers with hearing loss can be diagnosed and treated timely. During the process, evaluation of auditory function is of great importance, which can fully reflect the outcomes of auditory intervention. With the variety of auditory function evaluation tools, we should concern the psychometric properties and clinical applications of each tool before application.

Synaptojanin2 Mutation Causes Progressive High-frequency Hearing Loss in Mice

Progressive hearing loss is very common in the human population but we know little about the underlying molecular mechanisms. Synaptojanin2 (Synj2) has been reported to be involved, as a mouse mutation led to a progressive increase in auditory thresholds with age. Synaptojanin2 is a phosphatidylinositol (PI) phosphatase that removes the five-position phosphates from phosphoinositides, such as PIP₂ and PIP₃, and is a key enzyme in clathrin-mediated endocytosis. To investigate the mechanisms underlying progressive hearing loss, we have studied a different mutation of mouse Synj2 to look for any evidence of involvement of vesicle trafficking particularly affecting the synapses of sensory hair cells. Auditory brainstem responses (ABR) developed normally at first but started to decline between 3 and 4 weeks of age in Synj2^tm1b mutants. At 6 weeks old, some evidence of outer hair cell (OHC) stereocilia fusion and degeneration was observed, but this was only seen in the extreme basal turn so cannot explain the raised ABR thresholds that correspond to more apical regions of the cochlear duct. We found no evidence of any defect in inner hair cell (IHC) exocytosis or endocytosis using single hair cell recordings, nor any sign of hair cell synaptic abnormalities. Endocochlear potentials (EP) were normal. The mechanism underlying progressive hearing loss in these mutants remains elusive, but our findings of raised distortion product otoacoustic emission (DPOAE) thresholds and signs of OHC degeneration both suggest an OHC origin for the hearing loss. Synaptojanin2 is not required for normal development of hearing but it is important for its maintenance.

Can auditory brain stem response accurately reflect the cochlear function?

Auditory brain stem response (ABR) and compound action potential (CAP) recordings have been used in animal research to determine hearing sensitivity. Because of the relative ease of testing, the ABR test has been more commonly used in assessing cochlear lesions than the CAP test. The purpose of this experiment is to examine the difference between these two methods in monitoring the dynamic changes in auditory function after cochlear damage and in detecting asymmetric hearing loss due to unilateral cochlear damage. ABR and CAP were measured in two models of cochlear damage: acoustic trauma induced by exposure to a narrowband noise centered at 4 kHz (2,800-5,600 Hz) at 105 dB sound pressure level for 5 h in chinchillas and unilateral cochlear damage induced by surgical destruction of one cochlea in guinea pigs. Cochlear hair cells were quantified after completing the evoked potential testing. In the noise-damaged model, we found different recovery patterns between ABR and CAP. At 1 day after noise exposure, the ABR and CAP assessment revealed a similar level of threshold shifts. However, at 30 days after noise exposure, ABR thresholds displayed an average of 20-dB recovery, whereas CAP thresholds showed no recovery. Notably, the CAP threshold signifies the actual condition of sensory cell pathogenesis in the cochlea because sensory cell death is known to be irreversible in mammals. After unilateral cochlear damage, we found that both CAP and ABR were affected by cross-hearing when testing the damaged ear with the testing stimuli delivered directly into the canal of the damaged ear. When cross-hearing occurred, ABR testing was not able to reveal the presence of cross-hearing because the ABR waveform generated by cross-stimulation was indistinguishable from that generated by the test ear (damaged ear), should the test ear be intact. However, CAP testing can provide a warning sign, since the typical CAP waveform became an ABR-like waveform when cross-hearing occurred. Our study demonstrates two advantages of the CAP test over the ABR test in assessing cochlear lesions: contributing evidence for the occurrence of cross-hearing when subjects have asymmetric hearing loss and providing a better assessment of the progression of cochlear pathogenesis.NEW & NOTEWORTHY Auditory brain stem response (ABR) is more commonly used to evaluate cochlear lesions than cochlear compound action potential (CAP). In a noise-induced cochlear damage model, we found that the reduced CAP and enhanced ABR caused the threshold difference. In a unilateral cochlear destruction model, a shadow curve of the ABR from the contralateral healthy ear masked the hearing loss in the destroyed ear.

Interactive Improvements of Visual and Auditory Function for Enhancing Performance in Youth Soccer Players

We analyzed the effects of a regular training program on the health- and skill-related physical fitness (PF) of talented soccer players aged < 12 years; visual reaction time (VRT) and auditory reaction time (ART) were also assessed. In this single-group interventional study, 78 talented male youth soccer players (mean age, 9.54 years) were critically selected by the Korean Educational Development Institute and underwent a 22-week training program consisting of 16 weeks of PF and basic skill training (90 min/week) and 6 weeks of intensive training (3, 150-min sessions/week). We assessed the pre- and post-training body composition, cardiovascular endurance, muscle strength and endurance, and flexibility. We also measured power, agility, coordination and speed, passing ability, VRT, and ART. All variables improved after training. Post-training VRT correlated with ART, muscle mass, power, cardiovascular endurance, 10-m dribble time, 10-m ball touch count, and 10-m successful pass count. ART only correlated with muscle mass. ART and 10-m ball-touch count influenced VRT, and VRT influenced ART. In conclusion, the training program enhanced the PF and visual- and auditory-related reactions in talented youth soccer players. This study suggests the importance of the assessed relationships, indicating that a training program that improves these parameters enhances the players’ performance.

β-Secretase BACE1 Is Required for Normal Cochlear Function

Cleavage of amyloid precursor protein (APP) by β-secretase BACE1 initiates the production and accumulation of neurotoxic amyloid-β peptides, which is widely considered an essential pathogenic mechanism in Alzheimer's disease (AD). Here, we report that BACE1 is essential for normal auditory function. Compared with wild-type littermates, BACE1^-/- mice of either sex exhibit significant hearing deficits, as indicated by increased thresholds and reduced amplitudes in auditory brainstem responses (ABRs) and decreased distortion product otoacoustic emissions (DPOAEs). Immunohistochemistry revealed aberrant synaptic organization in the cochlea and hypomyelination of auditory nerve fibers as predominant neuropathological substrates of hearing loss in BACE1^-/- mice. In particular, we found that fibers of spiral ganglion neurons (SGN) close to the organ of Corti are disorganized and abnormally swollen. BACE1 deficiency also engenders organization defects in the postsynaptic compartment of SGN fibers with ectopic overexpression of PSD95 far outside the synaptic region. During postnatal development, auditory fiber myelination in BACE1^-/- mice lags behind dramatically and remains incomplete into adulthood. We relate the marked hypomyelination to the impaired processing of Neuregulin-1 when BACE1 is absent. To determine whether the cochlea of adult wild-type mice is susceptible to AD treatment-like suppression of BACE1, we administered the established BACE1 inhibitor NB-360 for 6 weeks. The drug suppressed BACE1 activity in the brain, but did not impair hearing performance and, upon neuropathological examination, did not produce the characteristic cochlear abnormalities of BACE1^-/- mice. Together, these data strongly suggest that the hearing loss of BACE1 knock-out mice represents a developmental phenotype.SIGNIFICANCE STATEMENT Given its crucial role in the pathogenesis of Alzheimer's disease (AD), BACE1 is a prime pharmacological target for AD prevention and therapy. However, the safe and long-term administration of BACE1-inhibitors as envisioned in AD requires a comprehensive understanding of the various physiological functions of BACE1. Here, we report that BACE1 is essential for the processing of auditory signals in the inner ear, as BACE1-deficient mice exhibit significant hearing loss. We relate this deficit to impaired myelination and aberrant synapse formation in the cochlea, which manifest during postnatal development. By contrast, prolonged pharmacological suppression of BACE1 activity in adult wild-type mice did not reproduce the hearing deficit or the cochlear abnormalities of BACE1 null mice.

Functional and morphological analysis of different aminoglycoside treatment regimens inducing hearing loss in mice

Aminoglycoside ototoxicity is common in clinical practice but reliable protective agents currently do not exist. Aminoglycoside regimens causing ototoxicity in different laboratory animals are under investigation. The assessment method used most commonly to determine auditory effects is the auditory brainstem response (ABR). Distortion product otoacoustic emissions (DPOAE) have been used less frequently. A precise recommendation on the specific method to assess peripheral auditory function before and after aminoglycoside toxicity in mice does not exist. In order to evaluate various mouse models for ototoxic injury caused by various aminoglycoside regimens, there is a need for performing preliminary tests in small cohorts before large experiments. The aim of our study was to investigate different aminoglycoside regimens that cause substantial ototoxic damage in vivo. Aminoglycosides are safe and produce a detectable hearing threshold shift in a small cohort of mice that can be used as a model for preliminary tests. Different ototoxic regimens were assessed by ABR and DPOAE measurements pre- and post-treatment. Further, the sensory cell loss was quantified by counting hair cells in the cochlea. It was revealed that an ototoxic regimen with kanamycin twice daily for 15 consecutive days is safe, well tolerated and produces an early significant hearing threshold shift detected by DPOAE in a small cohort of mice. The study compared ABR and DPOAE in mentioned regimens for the first time and illustrated that DPOAE is well suited for detecting hearing threshold shifts in high frequencies before ABR threshold shifts occur in accordance with predominating outer hair cell damage mainly in the basal turn of the cochlea.

Interplay between Nutrition and Hearing Loss: State of Art

Hearing loss has been recently ranked as the fifth leading cause of years lived with disability, ahead of many other chronic diseases such as diabetes, dementia, or chronic obstructive pulmonary disease. Moreover, according to the World Health Organization, moderate-to-profound hearing loss affects about 466 million people worldwide. Its incidence varies in each population segment, affecting approximately 10% of children and increasing to 30% of the population over 65 years. However, hearing loss receives still very limited research funding and public awareness. This sensory impairment is caused by genetic and environmental factors, and among the latter, the nutritional status has acquired relevance due its association to hearing loss detected in recent epidemiological studies. Several experimental models have proved that the onset and progression of hearing loss are closely linked to the availability of nutrients and their metabolism. Here, we have reviewed studies focused on nutrient effects on auditory function. These studies support the potential of nutritional therapy for the protection against hearing loss progression, which is especially relevant to the aging process and related quality of life.

Assessment of auditory function and lipid levels in patients receiving oral isotretinoin (13-cis retinoid) therapy for acne vulgaris

Introduction

Isotretinoin (13-cis retinoid) is a synthetic retinoid. It was approved by the FDA in 1982 for use of oral isotretinoin in severe acne. It is also used in moderate-severe acne that does not respond to conventional treatments. Isotretinoin is the only available drug that affects all stages of acne pathogenesis.

Aim

To prospectively investigate whether there is an effect of isotretinoin therapy on auditory function and, if so, to demonstrate its association with simultaneous blood lipid levels.

Material and methods

Thirty patients (60 ears) with acne vulgaris, who received 0.5 mg/kg of isotretinoin therapy, were included in the study. Distortion product otoacoustic emissions (DPOAEs) and pure tone audiometry tests were performed to evaluate auditory function at the beginning of the procedure and the 6^th month of treatment. In addition, aspartate aminotransferase (AST), alanine aminotransferase (ALT), total cholesterol, triglyceride, high-density lipoproteins (HDL) and low-density lipoproteins (LDL) cholesterol levels were recorded.

Results

There was no statistically significant difference between pre-treatment and post-treatment mean pure tone audiometry threshold and DPOAE values; however, the increase in total blood cholesterol, triglyceride and LDL levels and the decrease in HDL levels were statistically significant.

Conclusions

According to our study findings, isotretinoin did not cause worsening of the bilateral hearing threshold, but increased blood lipid levels. There is no need for follow-up auditory functions in routine practice during therapy, but blood lipid levels should be monitored.

[Age-specific dynamics of the auditory function in the extremely premature babies]

Extremely early premature babies (i.e. those born before the 32^nd week of pregnancy) constitute a group at high risk of development of the perceptive forms of hearing impairment represented mostly by chronic sensorineural hearing loss (CSNHL) and hearing neuropathy (HN). The timely diagnostics of these hearing disorders in premature children and, accordingly, their early and adequate rehabilitation provide a basis for the prevention of hearing and speech problems. At the same time, the hearing function in prematurely born babies is known to be highly unstable and can undergo substantial changes with age; these changes are most frequently observed during the early childhood. This paper was designed to report the results of observations of the hearing function dynamics in a cohort of the extremely early premature children. A total of 186 babies were available for the examination. It was shown that 14 (7.5%) of them had hearing problems. They disappeared by the 12^th and 24^th months of life in 3 children. Three other babies experienced transformation of NH into CSNHL at the age of 12, 14, and 18 months. NH transformed into CSNHL in three children by the age of 12, 24, and 48 months. Five children developed delayed CSNHL by the 10^th, 15^th, 24^th, 28^th, and 36^th months of the actual life. These findings give evidence that the extremely premature children may experience both the improvement of the hearing function due largely to the processes of maturation in the auditory system and its deterioration or delayed formation of hearing impairment. It is concluded that the extremely early premature children born before the 32^nd week of pregnancy should remain under the dynamic audiological observation at least as long as the third or fourth years of life.

Alteration of auditory function in type 2 diabetic and pre-diabetic patients

BACKGROUND

The association between type 2 diabetes mellitus (T2DM) and hearing loss has not been fully investigated and there is little information on the effects of pre-diabetes on alterations in auditory function in Chinese subjects.

METHODS

The study recruited 51 patients with T2DM, 55 patients with pre-diabetes and 43 control subjects. Auditory function was assessed by pure tone audiometry (PTA) tests and distortion product of otoacoustic emissions (DPOAEs). Tinnitus symptoms were recorded using a medical history questionnaire.

RESULTS

A significantly larger number of patients with T2DM (45.1%) were affected by hearing loss, compared to pre-diabetes patients (23.6%; p = .04) and control subjects (25.6%; p = .02), as assessed by PTA. There was no significant difference in PTA between the number of pre-diabetes patients and control subjects. In contrast, mean DPOAEs amplitudes of the pre-diabetes patients were significantly lower than of the control subjects, at all frequencies investigated, except 0.75 kHz. A significantly greater number of pre-diabetes patients reported tinnitus symptoms.

CONCLUSIONS

Diabetes is associated with bilateral sensorineural hearing loss, especially at high frequencies. While pre-diabetes is not necessarily associated with significant hearing loss, there may be cochlear malfunction, as indicated by DPOAEs. Thus, patients with pre-diabetes who have tinnitus may benefit from DPOAEs and PTA tests.

The Relationship Between Hospital Construction and High-Risk Infant Auditory Function at NICU Discharge: A Retrospective Descriptive Cohort Study

PURPOSE

To describe the difference in auditory function at neonatal intensive care unit (NICU) discharge between high-risk infant cases exposed to hospital construction during NICU stay and those not exposed.

BACKGROUND

Noise produced by routine NICU caregiving exceeds recommended intensity. As California hospitals undergo construction to meet seismic safety regulations, vulnerable neonates are potentially exposed to even higher levels of noise. Ramifications are unknown.

METHODS

Retrospective data-based descriptive cohort design was used to compare high-risk infant auditory function at NICU discharge between hospital construction exposed and unexposed groups.

SAMPLE SIZE

N = 540 infant cases (243 construction exposed and 297 unexposed controls).

INCLUSION CRITERIA

Infant cases born and discharged from the study site NICU in the year 2010 (unexposed) and year 2015 (exposed) and received a newborn hearing screening by automated auditory brainstem evoked response (ABER) prior to discharge with results reported. Infant cases excluded: hearing screen results by ABER unavailable, potentially confounding characteristics (congenital infection, major anomalies including cleft lip and/or palate), and transferred into or out of the study site.

INSTRUMENTATION

ABER.

ANALYSIS

descriptive statistics (SPSS Version 24.0), hypothesis testing, correlation, and logistic regression.

RESULTS

The difference in auditory function at NICU discharge between high-risk infant cases exposed to hospital construction noise and those unexposed was statistically insignificant, χ² = 1.666, df = 4, p = .1968, 95% confidence interval [-0.635, 2.570].

CONCLUSIONS

More research is needed to better understand whether hospital construction exposure during NICU admission negatively affects high-risk infant auditory function. Findings may catalyze theory development, future research, and child health policy.

Knockout Mice for Dyslexia Susceptibility Gene Homologs KIAA0319 and KIAA0319L have Unaffected Neuronal Migration but Display Abnormal Auditory Processing

Developmental dyslexia is a neurodevelopmental disorder that affects reading ability caused by genetic and non-genetic factors. Amongst the susceptibility genes identified to date, KIAA0319 is a prime candidate. RNA-interference experiments in rats suggested its involvement in cortical migration but we could not confirm these findings in Kiaa0319-mutant mice. Given its homologous gene Kiaa0319L (AU040320) has also been proposed to play a role in neuronal migration, we interrogated whether absence of AU040320 alone or together with KIAA0319 affects migration in the developing brain. Analyses of AU040320 and double Kiaa0319;AU040320 knockouts (dKO) revealed no evidence for impaired cortical lamination, neuronal migration, neurogenesis or other anatomical abnormalities. However, dKO mice displayed an auditory deficit in a behavioral gap-in-noise detection task. In addition, recordings of click-evoked auditory brainstem responses revealed suprathreshold deficits in wave III amplitude in AU040320-KO mice, and more general deficits in dKOs. These findings suggest that absence of AU040320 disrupts firing and/or synchrony of activity in the auditory brainstem, while loss of both proteins might affect both peripheral and central auditory function. Overall, these results stand against the proposed role of KIAA0319 and AU040320 in neuronal migration and outline their relationship with deficits in the auditory system.

Role of Obesity on the Prognosis of Sudden Sensorineural Hearing Loss in Adults

OBJECTIVE

To investigate the role of obesity/overweight on the prognosis of sudden sensorineural hearing loss (SSHL).

STUDY DESIGN

Retrospective cohort study.

SETTING

Outpatient department of a community hospital.

SUBJECTS AND METHODS

We collected 254 adult patients with SSHL from a community hospital. The odd ratios of body mass index (BMI) or obesity/overweight (BMI ≥25 kg/m(2)) on the recovery of SSHL were evaluated with multivariate logistic regression analysis.

RESULTS

There were 120 (47.2%) patients in the nonobesity group (BMI <25 kg/m(2)) and 134 (52.8%) patients in the obesity/overweight group (BMI ≥25 kg/m(2)). The complete and partial recovery rates were 10.0% and 49.2% in the nonobesity group and 9.7% and 47.0% in the obesity/overweight group, respectively. Univariate logistic regression showed that BMI had no significant association with recovery of SSHL (odds ratio [OR] of complete and partial recovery versus no recovery = 1.04, 95% confidence interval [CI] = 0.965-1.113, P = .327). Multivariate logistic regression analysis also showed that BMI (OR = 1.04, 95% CI = 0.964-1.131, P = .292) was not significantly associated with the recovery of SSHL for all subjects, after adjusting for all considered variables. Also, obesity/overweight (BMI ≥25 kg/m(2)) had no significant association with the recovery of SSHL.

CONCLUSION

Obesity/overweight would appear to have no significant effect on the prognosis of SSHL.

Local mechanisms for loud sound-enhanced aminoglycoside entry into outer hair cells

Loud sound exposure exacerbates aminoglycoside ototoxicity, increasing the risk of permanent hearing loss and degrading the quality of life in affected individuals. We previously reported that loud sound exposure induces temporary threshold shifts (TTS) and enhances uptake of aminoglycosides, like gentamicin, by cochlear outer hair cells (OHCs). Here, we explore mechanisms by which loud sound exposure and TTS could increase aminoglycoside uptake by OHCs that may underlie this form of ototoxic synergy. Mice were exposed to loud sound levels to induce TTS, and received fluorescently-tagged gentamicin (GTTR) for 30 min prior to fixation. The degree of TTS was assessed by comparing auditory brainstem responses (ABRs) before and after loud sound exposure. The number of tip links, which gate the GTTR-permeant mechanoelectrical transducer (MET) channels, was determined in OHC bundles, with or without exposure to loud sound, using scanning electron microscopy. We found wide-band noise (WBN) levels that induce TTS also enhance OHC uptake of GTTR compared to OHCs in control cochleae. In cochlear regions with TTS, the increase in OHC uptake of GTTR was significantly greater than in adjacent pillar cells. In control mice, we identified stereociliary tip links at ~50% of potential positions in OHC bundles. However, the number of OHC tip links was significantly reduced in mice that received WBN at levels capable of inducing TTS. These data suggest that GTTR uptake by OHCs during TTS occurs by increased permeation of surviving, mechanically-gated MET channels, and/or non-MET aminoglycoside-permeant channels activated following loud sound exposure. Loss of tip links would hyperpolarize hair cells and potentially increase drug uptake via aminoglycoside-permeant channels expressed by hair cells. The effect of TTS on aminoglycoside-permeant channel kinetics will shed new light on the mechanisms of loud sound-enhanced aminoglycoside uptake, and consequently on ototoxic synergy.

Acoustic Startle Reflex and Prepulse Inhibition

The completion of genome sequencing in humans and mice has opened new opportunities to study the relationship between gene expression and behavior and for development of novel therapeutic approaches for brain diseases. Recently, several international programs for large-scale production and phenotyping of genetically modified mice have been launched (e.g., EUCOMM, EUMODIC, IMPC), and comprehensive high-throughput behavioral phenotyping strategies have been developed (EUMORPHIA). In this context, startle reflex represents an important research tool for studying the impact of genetic manipulations not only on sensory processes but also on complex brain functions such as cognition, emotions, and movement control. In this unit, step-by-step protocols for measurement of acoustic startle reactivity and prepulse inhibition of startle in mice are described, and supporting experimental data presented. Curr. Protoc. Mouse Biol. 2:25-35 © 2012 by John Wiley & Sons, Inc.

An analysis of auditory manifestations in a group of adults with AIDS prior to antiretroviral therapy

The chief objective of the current study was to investigate the auditory status in a group of adults with AIDS before commencing antiretroviral therapy (ART) in a hospital outpatient clinic in Gauteng, South Africa. A total sample of 150 participants, aged between 20 and 46 years, was assessed following a prospective qualitative research design. All participants underwent case history interviews and medical record reviews, otoscopy and tympanometry, as well as conventional pure tone audiometry testing. Descriptive statistics was used to analyse data obtained. Prevalence, type, degree, configuration, and symmetry of the auditory manifestations; as well as type of onset of hearing loss and the possible causes of the auditory manifestations were analysed. Findings indicated that auditory manifestations in adults with AIDS are varied in nature and are possibly due to a number of causes. Manifestations including hearing loss, tinnitus and vertigo (in varied combinations) were found; with the types of hearing loss being mainly sensorineural in nature. The severity of hearing loss ranged from mild to severe, occurred either unilaterally or bilaterally; with the type of onset being mainly gradual and progressive in nature. The varied causes of hearing loss included HIV infection or AIDS illness as a primary cause, opportunistic infections, and various ototoxic therapies that the patients had undergone. Implications for future research as well as future assessment and management of patients with AIDS are raised.

Cerebellum and auditory function: an ALE meta-analysis of functional neuroimaging studies

Over the past two decades neuroimaging data have accumulated showing that the cerebellum, traditionally viewed only as a motor structure, is also active in a wide variety of sensory and cognitive tasks. We have proposed that instead of explicit involvement in any particular motor, sensory, or cognitive task, the cerebellum performs a much more fundamental computation involving the active acquisition of sensory data. We carried out an activation likelihood estimate (ALE) meta-analysis to determine whether neuroimaging results obtained during a wide range of auditory tasks support this proposal. Specifically, we analyzed the coordinates of 231 activation foci obtained in 15 different auditory studies selected through an extensive search of the positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) literature. The studies selected represent a wide variety of purely auditory tasks using highly controlled synthesized acoustic stimuli. The results clearly revealed that in addition to temporal auditory areas of cerebral cortex, specific regions in the cerebellum are activated consistently across studies regardless of the particular auditory task involved. In particular, one area in left lateral crus I area showed the greatest volume and ALE peak value among the extratemporal regions. A subanalysis was carried out that ruled out the specific association of this cerebellar cluster with attentional demand. The results are consistent with the hypothesis that the cerebellum may play a role in purely sensory auditory processing, and are discussed in light of the broader idea of the cerebellum subserving a fundamental sensory function.