Sensorineural hearing loss and ischemic injury: Development of animal models to assess vascular and oxidative effects

Relationship between hearing loss and glasgow prognostic score in patients with cancer

OBJECTIVE

Oxidative stress damages cochlear hair cells in vitro. However, the effect of systemic inflammation on hearing loss remains unclear. Growing evidence suggests that malnutrition influences the development of hearing loss. In this study, we aimed to investigate the influence of the Glasgow prognostic score (GPS), which is calculated based on systemic inflammatory responses and malnutrition, on auditory threshold increases in patients with cancer.

METHODS

This single-center retrospective cohort study included patients with cancer who underwent standard pure-tone audiometry (PTA) between November 2014 and May 2023. Patients with complete data in their electronic medical records within 90 days before undergoing standard PTA were included. Multivariate analysis was performed using auditory threshold as the response variable. Covariates, including GPS, were obtained from blood data and physical data before standard PTA. The GPS was classified into three levels based on serum albumin and C-reactive protein levels.

RESULTS

Standard PTA was performed 14,868 times in 5,462 patients. Of these, 742 had cancer and 384 met the inclusion criteria. Multivariate analysis revealed that older age, creatinine clearance <60 mL/min, and high GPS significantly increased the auditory threshold at frequencies of 500-8,000 Hz. A history of platinum drug use and male sex increased the auditory threshold at frequencies >4,000 and >2,000 Hz, respectively.

CONCLUSION

The GPS was independently associated with elevated standard PTA thresholds in patients with cancer. These results suggest an association between malnutrition/chronic inflammation and hearing loss and provide new information for planning clinical research on hearing loss prevention.

Effects of cooking with solid fuel on hearing loss in Chinese adults-Based on two cohort studies

The association between cooking fuel and hearing loss still needs more research to clarify, and two longitudinal cohort studies were explored to find if solid fuel use for cooking affected hearing in Chinese adults. The data from Chinese Health and Retirement Longitudinal Survey (CHARLS) and Chinese Longitudinal Healthy Longevity Survey (CLHLS) were analyzed. Participants (older than 18) without hearing loss at baseline and follow-up visits were included, which were divided into clean fuel and solid fuel groups. Hearing loss rate was from follow-up visits (both in year 2011) until the recent one (year 2018 in CHARLS and 2019 in CLHLS). Cox regressions were applied to examine the associations with adjustment for potential confounders. Fixed-effect meta-analysis was used to pool the results. A total of 9049 participants (average age 8.34 ± 9.12 [mean ± SD] years; 4247 [46.93%] males) were included in CHARLS cohort study and 2265 participants (average age, 78.75 ± 9.23 [mean ± SD] years; 1148 [49.32%] males) in CLHLS cohort study. There were 1518 (16.78%) participants in CHARLS cohort and 451 (19.91%) participants in CLHLS cohort who developed hearing loss. The group of using solid fuel for cooking had a higher risk of hearing loss (CHARLS: HR, 1.16; 95% CI 1.03-1.30; CLHLS: HR, 1.43; 95% CI 1.11-1.84) compared with the one of using clean fuel. Pooled hazard ratio showed the incidence of hearing loss in the solid fuel users was 1.17 (1.03, 1.29) times higher than that of clean fuel users. Hearing loss was associated with solid fuel use and older people were at higher risk. It is advised to replace solid fuel by clean fuel that may promote health equity.

Updates on Genetic Hearing Loss: From Diagnosis to Targeted Therapies

Sensorineural hearing loss (SNHL) is the most common sensory disorder, with a high Mendelian genetic contribution. Considering the genotypic and phenotypic heterogeneity of SNHL, the advent of next-generation sequencing technologies has revolutionized knowledge on its genomic architecture. Nonetheless, the conventional application of panel and exome sequencing in real-world practice is being challenged by the emerging need to explore the diagnostic capability of whole-genome sequencing, which enables the detection of both noncoding and structural variations. Small molecules and gene therapies represent good examples of how breakthroughs in genetic understanding can be translated into targeted therapies for SNHL. For example, targeted small molecules have been used to ameliorate autoinflammatory hearing loss caused by gain-of-function variants of NLRP3 and inner ear proteinopathy with OSBPL2 variants underlying dysfunctional autophagy. Strikingly, the successful outcomes of the first-in-human trial of OTOF gene therapy highlighted its potential in the treatment of various forms of genetic hearing loss. clustered regularly interspaced short palindromic repeats (CRISPR)-based technologies are currently being developed for site-specific genome editing to treat human genetic disorders. These advancements have led to an era of genotype- and mechanism-based precision medicine in SNHL practice.

Association Between Speech Reception Threshold in Noise and Multimorbidity: The UK Biobank Study

OBJECTIVE

To investigate the association between hearing function, as approached with the functional auditory capacity, and multimorbidity.

STUDY DESIGN

Cross-sectional study.

SETTING

The UK Biobank was established from 2006 to 2010 in the United Kingdom. This cross-sectional analysis included 165,524 participants who provided baseline information on hearing function.

METHODS

Functional auditory capacity was measured with a digit triplet test. Three categories were defined according to the speech reception threshold in noise (SRTn): normal (SRTn < -5.5 dB signal-to-noise ratio [SNR]), insufficient (SRTn ≥ -5.5 to ≤ -3.5 dB SNR) and poor hearing function (SRTn > -3.5 dB SNR). To define multimorbidity, 9 chronic diseases were considered, including chronic obstructive pulmonary disease, dementia, Parkinson's disease, stroke, cancer, depression, osteoarthritis, coronary heart disease, and diabetes; multimorbidity was defined as the coexistence of 2 or more in the same individual. Analyses were conducted using logistic models adjusted for relevant confounders.

RESULTS

Among the study participants, 54.5% were women, and the mean (range) age was 56.7 (39-72) years. The prevalence of insufficient and poor hearing function and multimorbidity was 13% and 13.2%, respectively. In comparison with having a normal SRTn, the odds ratio (95% confidence interval) of multimorbidity associated with insufficient SRTn was 1.13 (1.08-1.18), and with poor SRTn was 1.25 (1.14-1.37).

CONCLUSION

Insufficient and poor hearing function was associated with multimorbidity. This association suggests common biological pathways for many of the considered morbidities.

Underestimated Subsequent Sensorineural Hearing Loss after Septicemia

Background and Objectives: Hearing loss after septicemia has been found in mice; the long-term risk increased 50-fold in young adults in a previous study. Hearing loss after septicemia has not received much attention. The aim of this study was to assess the relationship between septicemia and subsequent hearing loss. Materials and Methods: Inpatient data were obtained from the Taiwan Insurance Database. We defined patients with sensorineural hearing loss and excluded patients under 18 years of age. Patients without hearing loss were selected as controls at a frequency of 1:5. The date of admission was defined as the date of diagnosis. Comorbidities in the 3 years preceding the date of diagnosis were retrieved retrospectively. Associations with hearing loss were established by multiple logistic regression and forward stepwise selection. Results: The odds ratio (OR) for the association between sepsis and hearing loss was 3.052 (95% CI: 1.583-5.884). Autoimmune disease (OR: 5.828 (95% CI: 1.906-17.816)), brain injury (OR: 2.264 (95% CI: 1.212-4.229)) and ischemic stroke (OR: 1.47 (95% CI: 1.087-1.988)) were associated with hearing loss. Conclusions: Our study shows that hearing loss occurred after septicemia. Apoptosis caused by sepsis and ischemia can lead to hair cell damage, leading to hearing loss. Clinicians should be aware of possible subsequent complications of septicemia and provide appropriate treatment and prevention strategies for complications.

Cervical and Ocular Vestibular Evoked Myogenic Potential Recovery in Susac Syndrome: A Case Report

Purpose:

Susac syndrome (SS) is a rare autoimmune disorder that affects the brain and the retina and causes unilateral or bilateral sensorineural hearing loss. Although vestibular dysfunction is reported in SS, limited information is available underlying the vestibular pathophysiology.

Method:

The diagnosis of SS was established based on symptoms and diagnostic tools such as magnetic resonance imaging and fundus fluorescein angiography. The audiovestibular evaluation was done on the seventh day of admission (Session 1) into the emergency unit, whereas the second and third evaluations were done at 3-month (Session 2) and 8-month (Session 3) follow-ups after discharge, respectively. The audiovestibular test battery consisted of routine audiological tests, auditory brainstem response, and vestibular evoked myogenic potentials (VEMPs; both cervical and ocular).

Results:

We found unilateral sensorineural hearing loss and absent cervical VEMPs(cVEMPs) when testing the left ear during Session 1. In the following sessions, the unilateral hearing loss did not recover; however, cVEMPs were present bilaterally. The ocular VEMPs showed an increase in amplitude during Sessions 2 and 3.

Conclusions:

SS can selectively disrupt auditory and vestibular structures. It may present with unique findings of audiovestibular tests. A detailed audiovestibular evaluation may be essential in patients with SS.

Supplemental Material:

https://doi.org/10.23641/asha.21513843

The prevalence and risk factors for congenital hearing loss in neonates: A birth cohort study based on CHALLENGE study

OBJECTIVES

To determine the prevalence and risk factors of congenital hearing loss (HL) in neonates based on China Longitudinal Environmental, Genetic, and Economic Cohort (CHALLENGE cohort).

METHODS

Maternal and neonatal data were collected based on the CHALLENGE cohort study from July 2018 to September 2020. Total 7287 neonates underwent the universal newborn hearing screening (UNHS). Babies who did not pass the initial screening and the rescreening were given the formal audiological diagnosis for possible HL. The data was analyzed to find out the prevalence and risk factors for congenital HL in this cohort study.

RESULTS

The prevalence of congenital HL was 3.43‰, and temporary HL was 0.07‰ (5 neonates). The statistical data showed that risk factors, including craniofacial anomalies, neonatal intensive care unit (NICU) admission, family history and advanced maternal age (AMA), could be associated with congenital HL. Additionally, exchange transfusion, assisted ventilation and NICU admission, these three factors could be associated with congenital sensorineural HL (SNHL). Risk factors including craniofacial anomalies, NICU admission, family history and AMA might be contributed to congenital conductive HL(CHL).

CONCLUSION

There were several common risk factors could be contributed to congenital HL, which were consistent with previous studies. However, some risk factors were no longer causing congenital HL due to the improvement of medical treatment and prenatal care. This study has not only helped explain the status quo of the prevalence of congenital HL in China but also laid foundation for future studies.

Associations between household solid fuel use and hearing loss in a Chinese population: A population-based prospective cohort study

Hearing loss, a common chronic condition, severely affects the quality of human life. However, the longitudinal relationships between household solid fuel use and hearing loss are unclear. To explore the associations between household solid fuel use and hearing loss in a Chinese population. There were 8835 participants enrolled in this prospective cohort study. Hearing function was assessed by asking the following self-reported question. Cox proportional hazards regression models were used to examine the relationships between baseline household solid fuel use and hearing loss incidence. After 6 (range, 2-7) years of follow-up, 1654 (18.72%) of 8835 participants developed hearing loss. This study demonstrated that increasing baseline solid fuel exposure was associated with a higher rate of poor hearing function (P for trend < 0.01). Compared with the clean fuel group (both cooking and heating), the hazard ratios (HR) (95% confidence intervals) of poor hearing function for the solid fuel group (cooking or heating) and both solid fuel groups (both cooking and heating) were 1.17 (1.01, 1.37) and 1.26 (1.09, 1.45) after adjustments, respectively. In subgroup analysis of household energy sources, the use of solid fuels for both heating (HR, 1.21; 1.07, 1.37) and cooking (HR, 1.12; 1.01, 1.26) was related to a higher incidence of poor hearing function. In subgroup analysis of place of residence, more solid fuel use was associated with a higher rate of poor hearing function in urban communities (HR, 1.39; 1.12, 1.74) but not in rural villages (HR, 1.18; 0.97, 1.45). Moreover, compared with the population that used solid fuel for cooking at both baseline and follow-up, those who switched from solid to clean fuel had a lower risk of developing poor hearing function (HR, 0.54, 0.46-0.63). This study demonstrates that household solid fuel use is closely associated with poor hearing function. Programs that educate individuals on the effects of household fuel use on hearing function should be established, especially in urban communities.

Hearing Loss After Radiation and Chemotherapy for CNS and Head-and-Neck Tumors in Children

PURPOSE

Hearing loss (HL) is a serious secondary effect of treatment for CNS and head-and-neck tumors in children. The goal of this study was to evaluate incidence and risk factors for HL in patients with multiple ototoxic exposures.

PATIENTS AND METHODS

We evaluated 340 ears from 171 patients with CNS or head-and-neck tumors treated with radiation, with or without chemotherapy, who had longitudinal audiologic evaluation. International Society of Pediatric Oncology-Boston grades were assigned to 2,420 hearing assessments. Multivariable weighted ordinal logistic regression was fitted to evaluate the effect of clinicopathologic features on HL.

RESULTS

Mean cochlea dose (odds ratio [OR] 1.04 per Gy, P < .001), time since radiotherapy (RT; OR 1.21 per year, P < .001), cisplatin dose (OR 1.48 per 100 mg/m², P < .001), and carboplatin dose (OR 1.41 per 1,000 mg/m², P = .002) were associated with increasing International Society of Pediatric Oncology-Boston grade of HL. There was no synergistic effect of RT and cisplatin (interaction term, P = .53) or RT and carboplatin (interaction term, P = .85). Cumulative incidence of high-frequency HL (> 4 kHz) was 50% or greater at 5 years after RT if mean cochlea dose was > 30 Gy, while incidence of HL across all frequencies continued to increase beyond 5 years after RT.

CONCLUSION

Children treated with radiation and chemotherapy experience a high incidence of HL over time, with associations found between more severe HL and cisplatin or carboplatin dose as well as mean cochlea dose. Mean cochlea dose of ≤ 30 Gy is proposed as a goal to reduce the risk of HL; a lower threshold (20-25 Gy) may be considered in patients receiving platinum chemotherapy to reduce cumulative HL burden.

Chronic Obstructive Pulmonary Disease is a Risk Factor for Sensorineural Hearing Loss: A US Population Study

OBJECTIVES

The goal of this study is to determine if chronic obstructive pulmonary disease (COPD) is associated with sensorineural hearing loss (SNHL) in a national database.

STUDY DESIGN

Cross-sectional study.

SETTING

National sample of the United States population.

PATIENTS

Adults with audiometric and spirometry data from the National Health and Nutrition Examination Study (NHANES) database.

INTERVENTIONS

None.

METHODS

A total of 2,464 adults with spirometry and audiometry data from the NHANES database (2009-2012) were studied. Outcome measures included hearing, measured by high-frequency pure tone average (HFPTA; 3, 4, 6, 8 kHz) and low-frequency pure tone average (LFPTA; .5, 1, 2 kHz) frequencies. SNHL was defined as a HFPTA or LFPTA threshold more than 25 decibels (dB) in the better ear. Multivariable regression analyses explored the association between hearing loss and COPD.

RESULTS

The prevalence of COPD was 19.8% in individuals with SNHL in the better ear and 4.7% in individuals with normal hearing (p < 0.001). Presence of COPD was associated with elevated hearing thresholds (worse hearing) at each individual frequency. The presence of COPD was independently associated with a 3.29 dB (95% CI: 1.48, 5.09) increase in HFPTA (p < 0.001), and 2.32 dB (1.13, 3.50) increase in LFPTA (p < 0.001) after controlling for medical, social, and environmental covariates. The presence of COPD was independently associated with a 1.85-fold (1.12, 3.06) increased odds of isolated low-frequency SNHL (p = 0.017).

CONCLUSIONS

COPD was independently associated with sensorineural hearing loss after controlling for multiple confounding factors. These results contribute to the evidence that COPD and pulmonary dysfunction can be comorbid with hearing decline.

Differential expression and hypoxia-mediated regulation of the N-myc downstream regulated gene family

Many organisms rely on oxygen to generate cellular energy (adenosine triphosphate or ATP). During severe hypoxia, the production of ATP decreases, leading to cell damage or death. Conversely, excessive oxygen causes oxidative stress that is equally damaging to cells. To mitigate pathological outcomes, organisms have evolved mechanisms to adapt to fluctuations in oxygen levels. Zebrafish embryos are remarkably hypoxia-tolerant, surviving anoxia (zero oxygen) for hours in a hypometabolic, energy-conserving state. To begin to unravel underlying mechanisms, we analyze here the distribution of the N-myc Downstream Regulated Gene (ndrg) family, ndrg1-4, and their transcriptional response to hypoxia. These genes have been primarily studied in cancer cells and hence little is understood about their normal function and regulation. We show here using in situ hybridization that ndrgs are expressed in metabolically demanding organs of the zebrafish embryo, such as the brain, kidney, and heart. To investigate whether ndrgs are hypoxia-responsive, we exposed embryos to different durations and severity of hypoxia and analyzed transcript levels. We observed that ndrgs are differentially regulated by hypoxia and that ndrg1a has the most robust response, with a ninefold increase following prolonged anoxia. We further show that this treatment resulted in de novo expression of ndrg1a in tissues where the transcript is not observed under normoxic conditions and changes in Ndrg1a protein expression post-reoxygenation. These findings provide an entry point into understanding the role of this conserved gene family in the adaptation of normal cells to hypoxia and reoxygenation.

Hydrogen peroxide toxicity on auditory cells: An in vitro study

In recent decades, interest has increased in the role of reactive oxygen species (ROS) in health and disease. The ROS are key causative factors in several hearing loss pathologies including ototoxicity, noise trauma, cochlear ageing and ischemic injury. In order to investigate ROS effects on inner ear cells and counteract them, we developed an in vitro model of oxidative stress by exposing the inner ear cell line OC-k3 to hydrogen peroxide (H₂O₂) at concentrations able to affect in vivo cellular components but allowing cell survival. The treatment with high concentrations (20 and 30 μM) resulted in reduction of cell viability, activation of apoptosis/necrosis and alteration of morphology, cell cycle progression and antioxidant defences. The ROS effects in inner ear cells are difficult to assess in vivo. Organocultures may provide preservation of tissue architecture but involve ethical issues and can be used only for a limited time. An in vitro model that could be commercially available and easy to handle is necessary to investigate inner ear oxidative stress and the ways to counteract it. The OC-k3 line is a suitable in vitro model to study ROS effects on inner ear cells because the observed cell alterations and damages were similar to those reported in studies investigating ROS effects of ototoxic drugs, noise trauma and cochlear ageing.

Nuclear Factor Erythroid 2-Related Factor 2-Histone Deacetylase 2 Pathway in the Pathogenesis of Refractory Sudden Sensorineural Hearing Loss and Glucocorticoid Resistance

INTRODUCTION

A significant number of sensorineural hearing loss (SSNHL) patients had no noticeable hearing improvement after glucocorticoid (GC) treatment. In the present study, we examined expression of the nuclear factor erythroid 2-related factor 2 (NRF2) and histone deacetylase 2 (HDAC2) in peripheral blood mononuclear cells (PBMCs) of refractory SSNHL patients to study the role of NRF2-HDAC2 pathway in GC insensitivity hearing improvement after GC treatment, which is usually referred to as refractory SSNHL or GC insensitivity.

MATERIALS AND METHODS

Forty-four refractory SSNHL patients were treated by intratympanic GC infusion. Hearing was tested in all patients before and after treatment by pure tone hearing test. NRF2/HDAC2 mRNA and protein levels were examined in PBMCs of refractory SSNHL patients before and after treatment. PBMCs from healthy volunteers were used as normal controls.

RESULTS

According to the hearing improvement after treatment, patients were assigned into 2 groups: the intratympanic GC sensitive (IGCS) group (hearing recovery ≥15 dB HL) and the intratympanic GC insensitive (IGCI) group (hearing recovery <15 dB HL). Before treatment, the NRF2 mRNA level was lower in all patients than the normal control group. After treatment, NRF2 and HDAC2 mRNA and protein levels were increased in the IGCS group, while no significant change was observed in the IGCI group.

CONCLUSION

Low response of NRF2/HDAC2 proteins is associated with GC insensitivity in SSNHL. We speculate that the NRF2-HDAC2 pathway affects GC sensitivity in SSNHL patients.

Effects of acute hypoxia on auditory pathway of Wistar albino rats

Background/aim

Ischemia 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 methods

Under 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.

Results

At 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.

Conclusion

Many 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.

Hearing impairment in young and middle-aged septicemia survivors

The ability of sepsis to induce acute phase hearing impairment has been evaluated in septic and sepsis-surviving mice. The relationship between septicemia and long-term hearing impairment remains unknown in humans.The data were obtained from the Taiwan Longitudinal National Health Insurance Database from 2000 to 2013. We identified patients suffering from septicemia after discharge, excluding those younger than 18 years old and older than 65 years old. The comparison group was matched based on age, sex, and comorbidities. The outcome was hearing impairment occurring after septicemia. The risk factors associated with hearing impairment were established using multivariate Cox proportional hazard regression.Our study found that septicemia associated with hearing impairment had an adjusted hazard ratio (HR) of 53.11 (95% confidence interval [CI]: 41.74-67.59). The other factors related to hearing impairment in young and middle-aged septicemia survivors included male sex (adjusted HR 1.31 [95% CI: 1.14-1.5]), chronic kidney disease (adjusted HR 1.63 [95% CI: 1.38-1.94]), and otoscleroisis (adjusted HR 231.54 [95% CI: 31.61-1695.8]).Our study revealed that septicemia was associated with increased development of hearing impairment in young and middle-aged humans in the long term. Clinicians should be aware of long-term septicemia-related hearing impairment and provide prevention strategies for otopathy in septicemia survivors.

Cochlear Patency after Translabyrinthine and Retrosigmoid Vestibular Schwannoma Surgery

OBJECTIVES

To assess the incidence and onset of cochlear obliteration after translabyrinthine and retrosigmoid vestibular schwannoma surgery.

MATERIALS AND METHODS

We retrospectively identified a consecutive series of eighty ears in eighty vestibular schwannoma patients who were treated via a translabyrinthine or retrosigmoid approach by a single neuro-otological surgical team in a tertiary referral center from May 2011 to January 2018. Postoperative, high- resolution T2-weighted turbo spin echo three-dimensional magnetic resonance (MR) images of the posterior fossa were evaluated at the level of the membranous labyrinth and internal auditory canal. Perilymphatic patency of the vestibule, basal, and apical cochlear turns were scored and classified as patent, hypointense, partially obliterated, or completely obliterated.

RESULTS

Twenty-five vestibular schwannomas were treated with surgery via a translabyrinthine approach, and fifty-five were treated using a retrosigmoid approach; of these, 8% and 65%, respectively, showed no signs of perilymphatic alterations in the basal or apical turns, while 84% and 20%, respectively, showed partial or complete obliteration in the basal or apical turns with a mean postoperative interval of 127 and 140 days, respectively. All the patients who underwent multiple MR scans and had a completely patent perilymphatic system on the first postoperative scan remained patent during subsequent scans; 16% of the patients showed worsened perilymphatic appearance. The onset of cochlear obliteration occurred within 2-7 months in most translabyrinthine patients.

CONCLUSION

These findings may support the need for simultaneous cochlear electrode or dummy implantation in translabyrinthine surgery. Second-stage implantation could be feasible in cases where a retrosigmoid approach is used; however, the implantation should be considered within the initial months to avoid cochlear obliteration. Findings on the first postoperative MR could indicate the need for intensified MR follow-up and may even predict the occurrence of cochlear obliteration.

Increased Risk of Sensorineural Hearing Loss as a Result of Exposure to Air Pollution

Whether exposure to air pollution is associated with developing sensorineural hearing loss (SHL) remains controversial. Using data from the National Health Insurance Research Database, we recruited a total of 75,767 subjects aged older than 20 years with no history of SHL from 1998 to 2010, and they were followed up until SHL was observed, they withdrew from the National Health Insurance program, or the study ended. The subjects were evenly exposed to low-level, mid-level, and high-level carbon monoxide (CO) and nitrogen dioxide (NO₂). The incidence rate ratio of SHL for patients exposed to high-level CO was 1.24 (95% confidence interval (CI) = 1.14–1.36). The NO₂ pollutants increased the incidence rate ratios of SHL in mid-level NO₂ and high-level NO₂ exposures by 1.10 (95% CI = 1.10–1.32) and 1.36 (95% CI = 1.24–1.49) times, respectively. The adjusted hazard ratio (adj. HR) of SHL in patients exposed to high-level CO was 1.45 (95% CI = 1.31–1.59), relative to that of patients exposed to low-level CO. Compared to patients exposed to low-level NO₂, patients exposed to mid-level NO₂ (adj. HR = 1.40, 95% CI = 1.27–1.54) and high-level NO₂ (adj. HR = 1.63, 95% CI = 1.48–1.81) had a higher risk of developing SHL. The increased risk of SHL following the increased concentrations of air pollutants (CO and NO₂) was statistically significant in this study. In conclusion, the subjects’ exposure to air pollution exhibited a significantly higher risk of developing SHL in Taiwan.

Acoustic Trauma Modulates Cochlear Blood Flow and Vasoactive Factors in a Rodent Model of Noise-Induced Hearing Loss

Noise exposure affects the organ of Corti and the lateral wall of the cochlea, including the stria vascularis and spiral ligament. Although the inner ear vasculature and spiral ligament fibrocytes in the lateral wall consist of a significant proportion of cells in the cochlea, relatively little is known regarding their functional significance. In this study, 6-week-old male C57BL/6 mice were exposed to noise trauma to induce transient hearing threshold shift (TTS) or permanent hearing threshold shift (PTS). Compared to mice with TTS, mice with PTS exhibited lower cochlear blood flow and lower vessel diameter in the stria vascularis, accompanied by reduced expression levels of genes involved in vasodilation and increased expression levels of genes related to vasoconstriction. Ultrastructural analyses by transmission electron microscopy revealed that the stria vascularis and spiral ligament fibrocytes were more damaged by PTS than by TTS. Moreover, mice with PTS expressed significantly higher levels of proinflammatory cytokines in the cochlea (e.g., IL-1β, IL-6, and TNF-α). Overall, our findings suggest that cochlear microcirculation and lateral wall pathologies are differentially modulated by the severity of acoustic trauma and are associated with changes in vasoactive factors and inflammatory responses in the cochlea.

The biological strategies for hearing re-establishment based on the stem/progenitor cells

The cochlea is the essential organ for hearing and includes both auditory sensory hair cells and spiral ganglion neurons. The discovery of inner ear stem cell brings hope to the regeneration of hair cell and spiral ganglion neuron as well as the followed hearing re-establishment. Thus the investigation on characteristics of inner ear stem/progenitor cells and related regulating clue is important to make such regeneration a reality. In addition, attempts have also been made to transplant exogenous stem cells into the inner ear to restore hearing function. In this review, we describe recent advances in the characterization of mammalian inner ear progenitor/stem cells and the mechanisms of regulating their proliferation and differentiation, and summarize studies that have used exogenous stem cells to repair damaged hair cells and neurons in the inner ear.

Applicability of vital staining and tissue clearing to vascular anatomy and melanocytes' evaluation of temporal bone in six laboratory species

The purpose of the present study was to define the applicability of tissue clearing to the field of otology. We combined tissue clearing with vital staining perfusion via a pumping system to examine the vascular anatomy of temporal bones in laboratory animals. We used six different types of species including Korean wild mouse, mouse, Mongolian gerbil, hamsters and Guinea pigs. A mixture of Alcian blue reagent and 4% paraformaldehyde was circulated throughout the entire circulatory system of the animal via a perfusion pump system. Transparency images were obtained from the temporal bones according to the protocol of the SunHyun 3D Imaging Kit. In examining the inner surface of the tympanic membrane, flaccid part (pars flaccida) was positioned along the entire marginal area in Guinea pig. In the Guinea pig, unlike the other species, the cortical bone of the mastoid (bullae) was easily removed using cold instruments, allowing a direct approach to the enclosed structures. The distribution and pattern of cochlea melanocytes were compared among the species. "Mobius strip"-like accumulated melanocytes in vestibules were shown in both the Korean wild mouse and mouse. The collateral blood supply to the cochlea in six different species was checked in various pattern. Combining dye infusion with tissue-clearing techniques, we documented the middle ear and transparent inner ear structures in six different species. The information and associated images will help other researchers to develop hypotheses and design experimental investigations.

Association between mitral valve prolapse and sudden sensorineural hearing loss: A case-control population-based study

This study aimed to evaluate the relationship between sudden sensorineural hearing loss (SSNHL) and MVP using a population-based dataset. Data for this case-control study were retrieved from the Taiwan Longitudinal Health Insurance Database. In total, 3399 cases of newly diagnosed SSNHL were identified. We used propensity score matching to select 3399 comparison patients (one for every case) from the same dataset. The selected matching variables included age, sex, monthly income, geographical location, urbanization level of the patient's residence, hypertension, diabetes, and hyperlipidemia. Chi-squared tests were used to compare differences in sociodemographic characteristics, while conditional logistic regression analyses were used to examine the association of SSNHL with previously diagnosed MVP. Of the 6798 sampled subjects, 131 (1.93%) patients had received a diagnosis of MVP prior to the index date. A significant difference in the prevalence of prior MVP between cases and controls (2.41% vs. 1.44%, p = 0.004) was observed. The conditional logistic regression analysis conditioned on gender, age, monthly income, urbanization level, geographic region, hyperlipidemia, diabetes, and hypertension suggested that the odds ratio of prior MVP for cases was 1.69 (95% confidence interval (CI): 1.18~2.42) compared to controls. Our study found that patients with MVP had a 1.69-fold higher risk of getting SSNHL compared to patients without MVP.

MIF protects against oxygen-glucose deprivation-induced ototoxicity in HEI-OC1 cochlear cells by enhancement of Akt-Nrf2-HO-1 pathway

Ischemia and oxidative stress play crucial roles in the pathophysiology of sudden sensorineural hearing loss (SSNHL). Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine and serves an important role in hearing function. The present study was designed to evaluate the effect of MIF on oxygen-glucose deprivation (OGD)-induced ototoxicity and to elucidate its molecular mechanism. In HEI-OC1 auditory cells, OGD reduced cell viability and increased supernatant lactate dehydrogenase (LDH) and MIF in a time-dependent manner. However, the reduced cell viability exerted by OGD was attenuated by antioxidant and MIF. Luciferase reporter assay demonstrated that MIF could activate NF-E2-related factor 2 (Nrf2), and real-time PCR showed increased mRNA expressions of Nrf2 and two Nrf2-responsive genes, including heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO1). MIF also suppressed oxidative stress induced by OGD, as demonstrated by decreased MDA and increased GSH in cellular supernatant. Inhibition of Nrf2 using siRNA suppressed HO-1 protein expression, the protective effect on OGD-induced injury and decrease in oxidative stress by MIF. Moreover, MIF prevented OGD-induced reduction of Akt1 phosphorylation at Ser473. LY294002, an inhibitor of PI3K/Akt signaling, attenuated the enhancement of Nrf2 protein and protective effect of MIF in OGD-treated cochlear cells. We demonstrate that MIF protects cochlear cells against OGD-induced injury through activation of Akt-Nrf2-HO-1 pathway.

Cochlear Pericytes Are Capable of Reversibly Decreasing Capillary Diameter In Vivo After Tumor Necrosis Factor Exposure

OBJECTIVE

The aim of this work was to evaluate the effect of tumor necrosis factor (TNF) and its neutralization with etanercept on the capability of cochlear pericytes to alter capillary diameter in the stria vascularis.

METHODS

Twelve Dunkin-Hartley guinea pigs were randomly assigned to one of three groups. Each group was treated either with placebo and then placebo, TNF and then placebo, or TNF and then etanercept. Cochlear pericytes were visualized using diaminofluorescein-2-diacetate and intravasal blood flow by fluorescein-dextrane. Vessel diameter at sites of pericyte somas and downstream controls were quantified by specialized software. Values were obtained before treatment, after first treatment with tumor necrosis factor or placebo and after second treatment with etanercept or placebo.

RESULTS

Overall, 199 pericytes in 12 animals were visualized. After initial treatment with TNF, a significant decrease in vessel diameter at sites of pericyte somas (3.6 ±4.3%, n = 141) compared with placebo and downstream controls was observed. After initial treatment with TNF, the application of etanercept caused a significant increase (3.3 ±5.5%, n = 59) in vessel diameter at the sites of pericyte somata compared with placebo and downstream controls.

CONCLUSION

We have been able to show that cochlear pericytes are capable of reducing capillary diameter after exposition to TNF. Moreover, the reduction in capillary diameter observed after the application of TNF is revertible after neutralization of tumor necrosis factor by the application of etanercept. It seems that contraction of cochlear pericytes contributes to the regulation of cochlear blood flow.

Examination of the Relationship between Umbilical Cord Blood Gas Values and Hearing Function in Neonates

Objective

The aim of the present study was to examine the relationship between the results of the transient otoacoustic emission (TEOAE) test used in neonatal hearing screening and the results of the umbilical cord blood (UCB) analysis in neonates.

Methods

This retrospective study included 209 neonates born in the obstetric unit at the 37^th gestational week. Based on the results of the TEOAE test, the neonates included in the study were divided into two groups as the study group composed of those "REFER" (n=141) and the control group consisting those "PASS" (n=68) the test. The UCB sampling procedure was performed on all neonates. In the blood samples, the pH parameters were evaluated by using glass electrodes, and the pCO₂ and pO₂ parameters were evaluated directly by using sensitive electrodes.

Results

When the additional maternal diseases were compared with the TEOAE results, the ratio of hypothyroidism was found to be statistically higher in the study group (p<0.05). In terms of the pO₂, pCO₂, HCO₃, and pH values obtained as a result of analyzing the UCB samples, there was no statistically significant difference between the groups (p>0.05).

Conclusion

The results of the present study showed that there was no statistically significant difference between the results of UCB analysis and the TEOAE test. However, we believe that conducting a larger study evaluating other parameters and employing UCB analysis would be useful, and UCB evaluation, which is an inexpensive, easy and effective method in determining hypoxia in neonates, might be a significant marker in cases at risk of hearing loss.

Systemic Lupus Erythematosus and hearing disorders: Literature review and meta-analysis of clinical and temporal bone findings

Objective

This literature review and meta-analysis was performed to evaluate the correlations among hearing and vestibular clinical symptoms, temporal bone findings, and pathological mechanisms in patients with systemic lupus erythematosus (SLE).

Study design

Relevant papers in the literature were retrospectively reviewed. Clinical hearing aspects in patients with SLE and relevant temporal bone studies in the same field were analyzed.

Methods

PubMed and Google Scholar searches were performed using the following keywords: “auto-immune disease,” “systemic lupus erythematosus (SLE),” “hearing loss,” “temporal bone study,” “vertigo,” “dizziness,” “tinnitus,” “ear symptoms,” “treatment,” “diagnosis,” “symptoms,” “etiopathogenesis,” “Wegener granulomatosis,” “Sjogren,” “polyarteritis nodosa,” “Cogan syndrome,” and “granulomatosis.” Also included were reviews in which the following terms were present: “SLE,” “temporal bone,” and “hearing symptoms.”

Review and conclusion

This literature review and meta-analysis focused on the pathological mechanisms through which SLE can damage inner ear structures and determinate hearing and vestibular symptoms. The main mechanisms involved in inner ear damage include the autoimmune response, deposition of immune complexes in the vessels and, to a lesser extent, cytotoxic damage.

Otopathologic Findings of Pena-Shokeir Syndrome Type I

BACKGROUND

Pena-Shokeir syndrome type I is a rare genetic disorder that includes multiple congenital facial and joint anomalies as well as pulmonary hypoplasia. Affected infants are usually premature, and 30% of them are stillborn. So far, studies have reported low-set ears in such infants, with no middle or inner ear findings.

METHOD

Histopathological study of human temporal bones with Pena-Shokeir syndrome type I.

RESULTS

Our case report describes an infant with severely decreased number of spiral ganglion cells and number of outer and inner hair cells of the cochlea, mild loss of vestibular hair cells, hypoplasia in the facial nerves, and ischemic degeneration of Schwann cells in the modiolus.

CONCLUSION

Pena-Shokeir syndrome type I is associated with a degenerative process in the labyrinth.