Etiology Of Hearing Loss Research Articles

Prevalence of GJB2 gene mutations correlated to presence of clinical and environmental risk factors in the etiology of congenital sensorineural hearing loss of the Romanian population.

Although etiologically heterogeneous at least 50% of all early on-set hearing losses have a genetic cause and of these, the large majority, 75-80% are most probably autosomal recessive and 70% are non-syndromic. The rest of the congenital hearing losses are determined by clinical and environmental factors such as ototoxic medication, prematurity, and complications at birth. During the last decade it became clear that 50-80% of all such afflictions result from mutations in a single gene, GJB2, which encodes the protein Connexin 26. In order to, at least partially clarify this problem, especially in an emerging country such as Romania, where the problem is not studied adequately, we developed a comprehensive study of genetic, clinical and environmental risk factors for congenital hearing loss. The two most common variations of this gene, 35delG and W24X in children with positive diagnosis of bilateral severe to profound sensorineural hearing loss were investigated. A cohort of 34 children (20 female and 14 male), ages between 2 and 10 (mean age 4.62 years), coming from 33 non-related families were evaluated. All cases were diagnosed with severe or profound bilateral congenital SNHL. A statistical comparison of genetic and environmental/clinical prevalence was also attempted since the presence of a genetic disorder cannot rule out the role of other documented risk factors in the etiology of SNHL. The results showed that, 29.4% of cases (10/34) were homozygotic for the 35delG mutation 35delG/35delG), also known as genotype Δ/Δ. 5.88% of cases (2/34) belong to the heterozygotic bi-genic group 35delG/W24X. The clinical factors with high statistical significance for SNHL in a non-genetic group have no significance for genetic SNHL patients. Thus, the present study confirms the relatively high prevalence of the 35delG and W24X mutations in cases of congenital non-syndromic severe of profound bilateral SNHL.

Confirmation of COL4A6 variants in X-linked nonsyndromic hearing loss and its clinical implications

Hearing loss (HL) is one of the most common sensory defects, of which X-linked nonsyndromic hearing loss (NSHL) accounts for only 1–2%. While a COL4A6 variant has been reported in a single Hungarian family with NSHL associated with inner ear malformation, causative role of COL4A6 variants and their phenotypic consequences in NSHL remain elusive. Here we report two families in which we identified a male member with X-linked HL. Each has inherited a rare hemizygous COL4A6 variant from their respective mothers, NM_001287758.1: c.3272 G > C (p.Gly1091Ala) and c.951 + 1 G > C. An in vitro minigene splicing assay revealed that c.951 + 1 G > T leads to skipping of exon 15, strongly suggesting a pathogenic role for this variant in the HL phenotype. The p.Gly1091Ala variant is classified as a variant of unknown significance based on the variant interpretation guidelines. This report provides evidence for variants in the COL4A6 gene resulting in X-linked NSHL. It highlights the importance of in-depth genetic studies in all family members in addition to the proband, especially in multiplex families, to determine the precise etiology of HL.

Usher Syndrome in the Inner Ear: Etiologies and Advances in Gene Therapy.

Hearing loss is the most common sensory disorder with ~466 million people worldwide affected, representing about 5% of the population. A substantial portion of hearing loss is genetic. Hearing loss can either be non-syndromic, if hearing loss is the only clinical manifestation, or syndromic, if the hearing loss is accompanied by a collage of other clinical manifestations. Usher syndrome is a syndromic form of genetic hearing loss that is accompanied by impaired vision associated with retinitis pigmentosa and, in many cases, vestibular dysfunction. It is the most common cause of deaf-blindness. Currently cochlear implantation or hearing aids are the only treatments for Usher-related hearing loss. However, gene therapy has shown promise in treating Usher-related retinitis pigmentosa. Here we review how the etiologies of Usher-related hearing loss make it a good candidate for gene therapy and discuss how various forms of gene therapy could be applied to Usher-related hearing loss.

The frequency of the homozygote 35delG mutation in the connexin 26 gene in North African with non-syndromic hearing loss: A meta-analysis study

ObjectiveEstimate the frequency of the homozygote 35delG mutation in patients with non-syndromic hearing loss. DesignMeta-analysis of studies investigated the presence of the 35delG mutation in patients from the North of Africa (Morocco, Algeria, Tunisia, Libya and Mauritania). We used three databases for seeking studies that reported the frequency of the 35delG mutation between 2000 and 2020. We excluded studies if they disagree with the inclusion criteria. Study samplePatients from the North of Africa with non-syndromic hearing loss. ResultsWe included 12 studies with a total of 1052 patients with non-syndromic hearing loss. The 35delG mutation was found in 303 (28.80%). ConclusionThe research of 35delG mutation is very useful in the investigation of the genetic etiology of non-syndromic hearing loss. However, including other gene candidates will be better for the identification of the etiology of hearing loss in patients negative for the 35delG mutation.

Etiology of early hearing loss in Brazilian children

IntroductionHearing loss etiology depends on the population studied as well as on the ethnicity and the socio-economic condition of the analyzed region. Etiological diagnosis contributes to the improvement of preventive measures and to the early identification of this deficiency. ObjectiveTo identify the etiological factors of hearing loss and its prevalence in a tertiary hospital in southern Brazil, to verify the frequency of mutations in GJB2 and GJB6 genes, and to correlate the degree of hearing loss with the etiological factors of deafness. MethodsThis prevalence study involved 140 children with bilateral sensorineural or mixed hearing loss. Medical history, physical examination, audiometry, and evoked auditory brainstem response were conducted. Imaging and genetic examinations were also performed. ResultsEtiologies and their prevalence were as follows: (a) indeterminate causes, 31.4%; (b) conditions related to neonatal period, 22.1%; (c) genetic, 22.1%; (d) auditory neuropathy, 10%; (e) other factors (cortical malformation, intracranial hemorrhage, and internal ear malformations), 7.9% and (f) congenital infections, 6.4%. Within the genetic cases, ten homozygous and seven heterozygotes of the 35delG mutation were identified, besides two cases of rare variants of GJB2: p.Try172* and p.Arg184Pro. One case with homozygosis of del(GJB6-D13S1830) was found. Regarding severity of hearing loss, in 78.6% of the cases the degree of hearing loss was profound and there were no significant differences when comparing between etiologies. ConclusionThe number of indeterminate etiologies is still high and congenital CMV infection may be a possible cause of undiagnosed etiology for hearing loss. The predominance of etiologies related to neonatal conditions and infectious causes are characteristic of developing countries. The most prevalent mutation was 35delG, the main GJB2 gene, probably because of the European influence in the genotype of our population.

Knowledge and attitudes of university health students in the Pacific Islands towards childhood hearing loss and hearing services: a Samoan survey study protocol

IntroductionThe Pacific Islands have among the highest rates of ear disease and hearing loss in the world, especially among children. Given that Ear, Nose and Throat (ENT)/audiology specialists are limited...

Clinical perspectives of anterior inferior cerebellar artery: a review

<p class="abstract">The anterior inferior cerebellar artery arises at the cerebellopontine angle (CPA), usually from the lower one third of the basilar artery. However, the vascular anatomy of the anterior inferior cerebellar artery (AICA) is highly variable. In respect to the neurovascular relationship in the internal auditory canal (IAC), the AICA is intimately related with vestibulocochlear and facial nerve. Microvascular compression of the vestibulocochlear nerve by AICA is an important etiology for tinnitus, hearing loss and vertigo. The vascular loop or aneurysm of the AICA will compress the vestibulocochlear nerve in the internal auditory canal. The AICA loop should be separated from the vestibulocochlear nerve. Magnetic resonance angiography (MRA) is helpful to reveal the vascular pathology of the AICA and confirm the causes for disabling otological symptoms. After confirmation of the vascular pathology of AICA, surgery is usually planned. The intrameatal AICA and vestibulocochlear nerve conflict produce specific pathological features and their surgical treatment is also invariably challenging. The objective of this review article is to discuss the details of vascular anatomy, etiopathology, clinical presentations, diagnosis, neurophysiology and current treatment of the vascular anomalies of AICA in IAC which often pose challenge to the clinicians.</p>

Congenital cytomegalovirus infection screening in high risk newborn

Congenital cytomegalovirus infection (cCMV) is the most frequent cause of congenital infection, 90% of affected newborn (NB) are asymptomatic at birth and 6-15% will develop long term sequalae. It is the main etiology of non-genetic sensorineural hearing loss. To determine prevalence of CMV in high risk NB. Cohort prospective study, including inpatient NB with one or more of following criteria: birth weight < 1,500 g, < 32 weeks gestational age (GA), severe small for gestational age (SGA), suspected congenital infection or "refer" in newborn hearing test, also NB to HIV-infected mothers. Urine CMV polymerase chain reaction was performed within 21 day of life. 193 NB were enrolled. Global cCMV prevalence 2.6% (n: 5) and by risk group: one third (n: 1) in NB with suspected congenital infection, 8.3% in NB with "refer" result in hearing test, 4.9% in NB to HIV-infected mothers, 3.3% in severe SGA and 1.7% in < 1,500 g, none with significant association. Only one symptomatic cCMV was detected who died in neonatal period and the remaining (asymptomatic) cCMV patients have normal hearing follow-up. Reported prevalence was comparable to international reports. We recommend cCMV screening, at least in risk groups, being ideal the universal screening. This would allow timely treatment and active follow-up.

Evaluation of Vibrant® Soundbridge™ positioning and results with laser doppler vibrometry and the finite element model.

The etiology of hearing loss originates from genetic factors and includes several other events including infections, working or living environment, as well as several endocrine and metabolic disorders. The Vibrant® Soundbridge™ (VSB) is an implantable hearing aid whose floating mass transducer (FMT) is attached to the long process of the incus. The device is used for pure sensorineural hearing loss with an intact middle ear. Variations in the manner of attachment may occur. Knowledge of the impact of such variations on the overall device performance may guide towards optimal transducer attachment during surgery. A mechanical modelling of the ear was first reported by von Békésy and indicated that the tympanic membrane (TM) moves as a stiff plate, and that the mallear and incudal ligaments act as a rotation axis for the ossicular chain at low frequencies. Experimental investigations and simulations with the model yield the same main results. The first fitting situation, where the FMT floats freely in the middle ear, provides by far the worst possible results. Contact to the stapes supra-structure of the FMT is necessary for optimal performance of the FMT. The mastoid specimen preserves its acoustic properties that have been shown to be similar to those in the vital human ear, under these conditions. Properly coupling the electromagnetic transducer to the ossicles can be difficult and it requires a certain degree of experience. A finite-element model (FEM) is useful for functional evaluation of the VSB since it enables easy modelling of the complicated middle ear structures and simulation of their dynamic behavior which makes it easy to understand it in detail without experiments.

Identifying barriers and considerations for cochlear implantation in Amish children

ObjectiveTo determine if barriers to cochlear implantation (CI) exist with respect to Amish children and to describe unique considerations associated with CI and subsequent otologic care in the Amish population. MethodsOut of all patients who underwent CI at a tertiary care pediatric hospital from 2008 to 2019, Amish children were age-matched to the remainder of the cohort to compare demographics and care-related metrics including etiology of hearing loss, age at time of initial hearing-related appointment and at CI, total number of pre- and post-operative audiologic and otologic appointments, and post-operative complications. Social considerations that may pose barriers to care were collected for descriptive analysis. ResultsSince 2008, 232 children underwent CI, of which 8 implants were performed on Amish children. Six (75%) Amish children underwent newborn hearing screening and 3(38%) were found to have syndromic etiology for hearing loss. While Amish patients had a lower number of both audiologic (15 vs 33.5, p<.001) and otologic (4.5 vs 8.5, p=.028) appointments when compared to age-matched controls, median age at the time of implantation for the whole sample was not different between groups (2.5 vs 2.0 years, p=.211). From a social standpoint, limitations in transportation, telephone communication, and ability to recharge processor batteries must be considered in the Amish population. ConclusionAmish children undergoing CI face unique barriers to care including transportation and technologic limitations, leading to overall fewer hearing-related appointments when compared to an age-matched cohort. Understanding societal differences is important to facilitate optimal care for Amish children with hearing loss.

Aetiologies of profound bilateral sensorineural hearing loss among children in Ekiti State, south western Nigeria

Introductiona strong need exists for the knowledge of aetiologies of diseases as this will guide the clinicians on the strategies for their treatment and prevention. In this study, we determined the aetiologies of profound bilateral sensorineural hearing loss (pbSNHL) with a view to provide the relevant data needed for preventive and therapeutic intervention among children in Ekiti State, South Western Nigeria.Methodsmedical records of children with pbSNHL seen over a ten-year period were analysed.Resultsin all, records of 142 children with pbSNHL were analysed. The results showed spectrum of aetiologies that were similar to those reported decades ago with the 'unknown' assuming a recurring decimal. Of the known (acquired) cases, measles takes up the largest 'chunk' with a prevalence of 45.8%. Twenty-eight (32.2%) of those with febrile illnesses had treated their fever with ototoxic antibiotics. Late diagnosis was characteristic of the pbSNHL.Conclusionthis study shows that there hasn't been any significant shift in the common causes of pbSNHL. Of great concern is the persistence of the 'unknown' causes which assumes a recurring decimal in this and previous studies. Also worrisome is the high prevalence of measles-induced pbSNHL despite the availability of anti-measles vaccine. We therefore suggest effective immunization against measles and other vaccine-preventable causes of pbSNHL. The need for intensive research on the unknown causes of pbSNHL is hereby stressed. Also recommended is routine hearing assessment for survivors of febrile conditions so as to detect, if any, hearing loss promptly.

A clinical study of different causes in unilateral sensorineural hearing loss

Background: Unilateral sensorineural hearing loss (USNHL) is important to be identified and diagnosed early. It is common and can be a symptom of a wide range of diseases. In our region, south India, the USNHL has not been studied before. In this study we report different causes of this entity.Method and Aim: This is a Prospective observational Hospital based study, review of 50 patient with USNHL in the age group above 18yrs. We aim to find the risk factors, causes, common presentationn of USNHL in the south India and comparing the result with a literature review.Result: It was found, 50 cases were presented with unilateral SNHL during the study period. It constitutes 15% of cases screened. Most of our cases had gradual onset of hearing loss. Tinnitus, vertigo and ear discharge were the most common associated symptoms respectively. On audiological assessment: PTA at time of investigation, severe hearing loss (46%). Etiologies of unilateral sensorineural hearing loss, Meniere's disease (28%), Metabolic (24%), Sudden SNHL (22%), idiopathic (20%), Acoustic neuroma (4%) and Left COM, squamosal disease (2%). MRI was done in all 50 cases with unilateral SNHL, in 4 cases it found to be abnormal. ENG was done in 35 of cases of which it is abnormal in 30 cases, Left Hypo active labyrinth (48.6%). Conclusion: All patients with USNHL need full audiological screening and early diagnosis. Regarding our study, we recommend MRI as part of their diagnostic workup. The choice of diagnostic laboratory tests should be directed by patient risk factors and exposures.

Dysregulation of sonic hedgehog signaling causes hearing loss in ciliopathy mouse models.

Defective primary cilia cause a range of diseases known as ciliopathies, including hearing loss. The etiology of hearing loss in ciliopathies, however, remains unclear. We analyzed cochleae from three ciliopathy mouse models exhibiting different ciliogenesis defects: Intraflagellar transport 88 (Ift88), Tbc1d32 (a.k.a. bromi), and Cilk1 (a.k.a. Ick) mutants. These mutants showed multiple developmental defects including shortened cochlear duct and abnormal apical patterning of the organ of Corti. Although ciliogenic defects in cochlear hair cells such as misalignment of the kinocilium are often associated with the planar cell polarity pathway, our results showed that inner ear defects in these mutants are primarily due to loss of sonic hedgehog signaling. Furthermore, an inner ear-specific deletion of Cilk1 elicits low-frequency hearing loss attributable to cellular changes in apical cochlear identity that is dedicated to low-frequency sound detection. This type of hearing loss may account for hearing deficits in some patients with ciliopathies.

Noise Outcomes in Servicemembers Epidemiology (NOISE) Study: Design, Methods, and Baseline Results.

Military Service members and Veterans commonly report hearing loss and tinnitus, both of which can result in significant disability. During military service, Service members are exposed to many different types of loud noise, which is strongly associated with hearing loss and tinnitus. Other military-related exposures, such as chemicals and traumatic brain injury (TBI), are also linked with auditory problems. The purpose of the "Noise Outcomes in Servicemembers Epidemiology" (NOISE) study is to gather information from Active-Duty Service members and recently separated Veterans about their military and nonmilitary noise exposures, other relevant military and nonmilitary exposures, and potential outcomes of these exposures including tinnitus, hearing loss, and other hearing-related health concerns. The NOISE study assesses lifetime noise exposures, chemical and blast exposures, TBI, physical and psychiatric comorbidities, and other military and nonmilitary exposures and outcomes that can affect auditory function. Participants undergo comprehensive in-person audiologic examinations; those who experience tinnitus undergo a complete tinnitus assessment. Exposures and select outcomes are reassessed annually by mail, and the comprehensive in-person assessment is completed every 5 years. This report presents descriptive, baseline data obtained from the first 690 participants enrolled between 2014 and 2018. Some notable findings from this analysis include: (1) the prevalence of hearing loss in the sample was 8% for low frequencies (0.25 to 2 kHz), 20% for high frequencies (3 to 8 kHz), and 39% for extended high frequencies (9 to 16 kHz); (2) the prevalence of tinnitus was 53%; (3) the prevalence of both hearing loss and tinnitus was higher among those with higher age, more years of military service, greater degree of noise exposure, and exposures to blasts and/or TBI in the military; and (4) tinnitus was most prevalent among participants who serve/served in the Army relative to the other military branches. The NOISE study is acquiring comprehensive data on military-related auditory dysfunction. It is the first of its kind to enroll active Service members and recently separated Veterans into a longitudinal study to examine the etiology and outcomes of tinnitus and hearing loss in this population. Although these data do not necessarily represent the entire military and Veteran populations, ongoing enrollment is focused on increasing generalizability and will also provide the statistical power to conduct multivariable analyses. This will allow us to examine longitudinal associations of interest while controlling for potential confounders and other possible sources of error. These data will provide critical knowledge to refine future military hearing conservation efforts and inform efforts to develop future treatments.

Diagnostic Assessment of Progressive Fluctuating Sensorineural Hearing Loss in Children

Deterioration of auditory thresholds in young children is directly associated with negative impact on language development. Early detection of the cause of sensorineural hearing loss eases proper intervention and signalizes valuable prognostic data. Nowadays, the etiology of pediatric hearing loss has been modified, attributable to progresses in gene testing and adequate management of birth infections. This paper updates well known risk factors for progression along with fluctuation of hearing acuity involving health hazard indicators, auditory, laboratory and clinical manifestations of such young patients. This review takes into consideration the most well-known risk indicators associated with an increased likelihood of progressive hearing loss (including but not limited to neonatal intensive care unit admission, family history of hearing loss, various syndromes, prenatal and postnatal infections etc.). Prompt post neonatal monitoring of hearing, leading to early hearing loss identification, is crucial to optimize management and therefore appropriate intervention.

Annals for Educators - 1 December 2020.

Annals for Educators - 1 December 2020.

Idiopathic Sudden Sensorineural Hearing Loss in Children: A Systematic Review and Meta-analysis.

Idiopathic sudden sensorineural hearing loss (ISSNHL) is uncommon in children, and its treatment and outcome are debated. We aimed to critically review evidence in the literature about treatment options and functional outcomes of pediatric ISSNHL. Additionally, we performed a meta-analysis of the results of combined systemic-intratympanic steroid therapy versus solely systemic treatment. A search was run in the PubMed, Scopus, and Google Scholar databases. Included articles were original ISSNHL case series, written in English, with a population age ranging from 2 to 19 years. Other study types (single case reports, editorials, and reviews) and case series with known etiology of sudden hearing loss were excluded. Descriptive data of patients, treatments, outcomes, and possible prognostic factors were extracted and recorded for every included study. Twelve articles (7 cohort and 5 case-control studies) met all the selection criteria. Based on only the studies that provided sufficient data about clinical outcome, the pooled overall recovery rate was 67.91% (95% CI, 58.34%-77.48%). No studies showed a significant difference between systemic steroid and combined systemic-intratympanic steroid. The pooled odds ratio for combined systemic-intratympanic steroid versus systemic steroid alone was 0.90 (95% CI, 0.36-2.27) based on a random effects model, ruling out any significant difference between these treatment options. The results of our meta-analysis did not support combination therapy more than systemic steroid alone. Further prospective clinical trials are necessary to establish evidence-based therapies.

Analysis of related factors between sudden sensorineural hearing loss and serum indices base on artificial intelligence and big data

Objective:The etiology and pathophysiologic mechanism of sudden sensorineural hearing loss are undefined. We will use artificial intelligence and big data methods to explore the correlation between sudden sensorineural hearing loss and serum indices. Method:A total of 1218 patients with sudden deafness admitted to Sun Yat-sen Memorial Hospital were selected as the experimental group, 95 861 healthy subjects were randomly selected as the control group at the same period. Serum biochemical indexes in two groups were collected and analyzed by TreeNet and CART machine learning algorithms, to screen out highly correlated indicators with sudden sensorineural hearing loss and dig out a set of clinical features for people with high risk of sudden sensorineural hearing loss. Result:It was found that high prevalence rate of sudden sensorineural hearing loss is related to eosinophils, reticulocyte and fibrinogen. The areas under the receiver operator characteristic curves（ROC-AUC） were exploited to evaluate the prediction performance of TreeNet model. Overall the TreeNet model has provided high predictive ability by ROC curve, achieving AUC of 0.99, both recall and accuracy rate of 99.90%. Conclusion:There is significant difference between sudden deadness and normal people in serum biochemical indexes. Eosinophil is the first important indicator to distinguish sudden sensorineural hearing loss. Treenet model has important referenced significance for the screening and diagnosis of sudden sensorineural hearing loss.

Genetic Testing Leading to Early Identification of Childhood Ocular Manifestations of Usher Syndrome.

Hearing-loss gene panel testing (HLGPT) is increasingly accessible as a first-line test in determining the etiology of sensorineural hearing loss (SNHL) in children. A major advantage of HLGPT is early identification of syndromic forms of SNHL, especially Usher syndrome, prior to the development of overt syndromic phenotype, which may impact management and counseling. Here, we describe early ocular findings in children with clinically non-syndromic SNHL identified by HLGPT as having two variants associated with Usher Syndrome. A total of 184 children, ages 1 month - 15 years of age, evaluated at one tertiary pediatric children's hospital for clinically non-syndromic SNHL, underwent next-generation sequencing of 150 genes involved in hearing loss. Children with two variants in genes associated with Usher syndrome were referred for evaluation by pediatric ophthalmology. A total of 18/184 tested children had two variants in Usher syndrome-associated genes, including MYO7A, GPR98 (ADGRV1), USH2A, and PDZD7. SNHL varied from moderate to profound. 29% of the children who underwent clinical ophthalmology evaluation were found to have previously unidentified retinal abnormalities on retinal imaging or electroretinography consistent with inherited retinal degeneration. Among this ethnically and racially diverse pediatric population with apparently non-syndromic SNHL, HLGPT yielded a high proportion (10%) of children with two variants in genes associated with Usher syndrome. Early genetic testing allows early identification of variants conferring a diagnosis of Usher syndrome at a stage prior to visual symptoms. This allows for more informed genetic counseling, reproductive planning, and sensory deficit interventions. 4 Laryngoscope, 131:E2053-E2059, 2021.

Effects of acute hypoxia on auditory pathway of Wistar albino rats

Background/aimIschemia is insufficient blood flow to provide adequate oxygenation. In the present study, we aimed to show whether acute hypoxia has a critical oxygen value that may lead to the deterioration of cochlear function.Materials and methodsUnder general anesthesia, prehypoxic signal-to-noise ratios were determined by distortion product otoacoustic emissions (DPOAE). The oxygen saturation (SaO2) values ​​of rats were monitored with an oxygen saturation probe. Rats were injected with an extra dose of anesthetic agent, and SaO2 was reduced. DPOAE values ​​in SaO2 100–90, 90–80, 80–70, and 70–60 posthypoxic values​ were measured and compared statistically with prehypoxic values.ResultsAt 3000 and 4000 Hz, SaO2 70–60 values measured after the hypoxia were observed to be statistically significantly lower than the values measured before the hypoxia. At 6000 and 8000 Hz, SaO2 80–70 and 70–60 values measured after the hypoxia were observed to be statistically significantly lower than the values measured before the hypoxia. At 10,000 Hz, all of the values measured after the hypoxia were observed to be statistically significantly lower than the values obtained before the hypoxia.ConclusionMany studies have been conducted on the effects of hypoxia on the inner ear. It remains unclear how fluctuations in DPOAE levels affect hearing in clinical trials when the SaO2 starts to decrease. Although hypoxia has been implicated in the etiology of sudden hearing loss and tinnitus, the effects of acute hypoxia on the cochlea are still uncertain. Further studies are needed on this subject.