Global problem of drug-induced hearing loss

Relationship Between Chloroquine or Hydroxychloroquine Use and Hearing Disorders: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Chloroquine and its analog hydroxychloroquine are derivatives of 4-aminoquinoline and are regularly used in the treatment of malaria and autoimmune diseases. Among the side effects of these drugs, alterations associated with the auditory system are frequently mentioned. Thus, the aim of this systematic review is to systematically review publications on hearing disorders and chloroquine or hydroxychloroquine use.

MATERIALS AND METHODS

Inclusion criteria were observational or interventional studies on audiological assessment in participants who were using chloroquine or hydroxychloroquine. The methodological quality was independently assessed by two reviewers using the Meta-Analysis of Statistics: assessment and review Instrument. The certainty of the evidence was assessed using the GRADE tool.

RESULTS

A total of 1,372 non-duplicate papers were screened, out of which 17 were included in the final qualitative synthesis, and 5 studies in the meta-analysis. The odds ratio for the two subgroups evaluated did not show significance with no heterogeneity between the effects observed between the different diseases (I2=0%) and obtaining the global estimate of 0.76 (95% confidence interval [CI]=0.41-1.39; p>0.05). Despite the inclusion of papers with different disease samples, the heterogeneity observed in the analysis was low (I2= 0%) and prediction interval (95% PI=0.32-1.80; p>0.05) remained close to that estimated by the CI (95% CI=0.41-1.39; p>0.05). The certainty of the evidence assessed by the GRADE tool was considered very low due to the risk of bias, indirect evidence, and imprecision.

CONCLUSIONS

The findings of this study suggest that the use of chloroquine/hydroxychloroquine is not associated with hearing disorders.

Self-reporting of hearing loss and tinnitus in the diagnosis of ototoxicity by meglumine antimoniate in patients treated for American tegumentary Leishmaniasis

INTRODUCTION

American Tegumentary Leishmaniasis (ATL) treatment is based on pentavalent antimonials (Sb5+), but these drugs have been associated to several adverse effects. Hearing loss and tinnitus during treatment with meglumine antimoniate (MA) have already been reported. This study aimed to describe the usefulness of self-reporting of hearing loss and tinnitus in diagnosing MA-induced ototoxicity.

METHODS

A prospective longitudinal study was conducted with 102 patients with parasitological diagnosis of ATL, treated with different MA schemes. The presence of clinical auditory toxicity was defined as the emergence or worsening of self-reporting hearing loss and/or tinnitus during monitoring. Measures of sensitivity, specificity, and the positive and negative predictive value of the patient's self-reporting of hearing loss and tinnitus in relation to the result of the audiometric test (considered the gold standard) were calculated.

RESULTS

The age of the evaluated patients ranged from 15 to 81 years, with a median of 41 years, and most were male (73.5%). Seventy-five patients (73.5%) had cutaneous leishmaniasis and 27 (26.5%) mucosal leishmaniasis. Eighty-six patients (84.3%) received intramuscular (IM) treatment and 16 (15.7%) were treated with intralesional MA. During treatment, 18 (17,6%) had tinnitus and 7 (6,9%) had complaint of hearing loss. 53 (52%) patients had cochlear toxicity confirmed by tone threshold audiometry and high frequency audiometry, from which 60% received a dose of 20 mg Sb5+/kg/day (p = 0.015) and 96.2% were treated with IM MA (p = 0.001). Tinnitus has greater specificity and positive predictive value than hearing loss, with a low number of false positives, but with a high false negative value.

CONCLUSION

Although the large number of false negatives suggests that self-report of hearing loss or tinnitus cannot be considered a good screening test for referring the patient to an audiometry, the low number of false positives suggests the need to value the patient's complaint for referral. Otherwise, this study reinforces the importance of audiological monitoring during treatment with MA, especially in those patients with self-reporting of hearing loss or tinnitus when treated with 20 mg Sb5+/kg/day via IM.

Exploring Embryo-Ototoxic Effects: Insights into Deodorant-Induced Hair Cell Damage in Zebrafish

Our study investigated the embryo-ototoxic effects of deodorant2 (DA2) on zebrafish embryos, which serve as valuable model organisms due to genetic and physiological similarities to humans. We focused on understanding DA2's impact on zebrafish hair cells, which are vital for sensory perception and balance regulation. DA2, provided by the Ministry of Environment, Republic of Korea, was used at 460 μg/mL in dimethyl sulfoxide (DMSO), with a 0.43% DMSO solvent control group. Three experiments, each using 10 zebrafish specimens from each group, showed an initial 13% hair cell count reduction in the DA2-exposed group. Subsequent experiments demonstrated reductions of 37% and 22%, each with one mortality case. Statistical analysis revealed a significant 24% hair cell count reduction in the DA2-exposed group. We also assessed DA2's impact on zebrafish behavior. Although not statistically significant, differences in distances traveled (0.33-0.39, 95% confidence interval: -0.46-1.1, p = 0.2033) and latencies (-0.016-0.018, 95% confidence interval: -0.052-0.021, p = 0.1917) hinted at negative effects. These results highlight DA2's ototoxic properties affecting zebrafish auditory systems and behavior. Further investigation into DA2's effects on aquatic organisms and potential mitigation strategies are essential. These findings contribute to understanding DA2's safety profile, benefiting aquatic ecosystems and human health assessments.

Prevalence of hearing loss in children living in low- and middle-income countries over the last 10 years: A systematic review

AIM

To summarize the literature on the prevalence of pediatric hearing loss in low- and middle-income countries (LMICs).

METHOD

A systematic review initially identified 2833 studies, of which 122 met the criteria for inclusion. Eighty-six of those studies included diagnoses and were included in a meta-analysis.

RESULTS

The meta-analysis indicated a 1% (95% confidence interval = 0.8-2.0) prevalence of childhood hearing loss across LMICs. There was significant heterogeneity between studies and evidence of publication bias. The prevalence of mild and moderate cases of hearing loss was higher than more severe cases and there were fewer cases of mixed hearing loss compared to conductive or sensorineural hearing loss. No differences were identified between the prevalence of unilateral versus bilateral hearing loss or hearing loss according to sex. The quality of the studies, age of participants, and location of data collection may have influenced the results. High variability in the reporting of etiology made the causes of hearing loss unclear.

INTERPRETATION

The literature indicates that 1% of children in LMICs have hearing losses. However, most studies missed children with acquired hearing loss, which may lead to under-reporting of global prevalence. This systematic review is an initial step toward developing and implementing population-appropriate treatment and prevention programs for childhood hearing loss in LMICs.

Prospective Observational Study of Evaluating Cisplatin-Induced Ototoxicity in Patients

Introduction Platinum-based chemotherapeutic agents cisplatin and carboplatin are two of the most widely used drugs in cancer today. They display wide range of adverse reactions; among them, ototoxicity is an important cumulative toxicity that more commonly observed with cisplatin. At a later stage, it can affect speech of individual and lead to communication problem with decreased cognitive function and depression in cancer survivors. Periodic monitoring of hearing loss with pure-tone audiometry (PTA) provides early evidence of ototoxicity which may decrease debilitating effect of the same in a patient.

Objective The primary objective of this study was to assess cisplatin-induced ototoxicity. We also investigated its severity, reversibility, and other modifying risk factors.

Materials and Methods We conducted a prospective observational descriptive type of epidemiological study. The study was conducted over 80 randomly selected cancer patients (for estimation of sample size, the following formula was used n = [Zα 2 PQ] / d 2), who were starting with their first cycle of cisplatin from August 2018 to July 2020. This study was conducted at tertiary cancer care center in western Gujarat which caters patients from all over India. We performed PTA in all randomized patients at baseline and periodically. We classified hearing loss according to the World Health Organization (WHO) criteria.

Results A total of 30% (n = 24) patients developed cisplatin-induced ototoxicity according to WHO criteria at end of 3 months after starting the first cycle of cisplatin. It was sensory neuronal, affecting both the ears equally, and was seen predominantly at high frequency. We observed hearing loss at 3 months to be significantly more common in the 301 to 400 mg/m2 cumulative dose group (47%), as compared with the other two groups (0–200 mg/m2 and 201–300 mg/m2; p < 0.05). It showed dose dependency with cisplatin. In the multivariate step-wise regression model, baseline hearing loss (odds ratio [OR] = 17.71, 95% confidence interval [CI]: 6.57–118.91, p < 0.05) and cumulative cisplatin dose of more than 300 mg/m2 were significantly associated with hearing loss at 3 months (OR = 6.62, 95% CI: 2.33–18.74, p < 0.05).

Conclusion Cisplatin-induced ototoxicity manifests as a bilateral high frequency sensorineural hearing loss. Cumulative dose of cisplatin is an important predictor of development of ototoxicity. Baseline and periodic audiometric monitoring could detect ototoxicity early which leads to possible limitation on the severity of ototoxicity.

Ototoxicity in childhood: Recommendations of the CODEPEH (Commission for the Early Detection of Childhood Hearing Loss) for prevention and early diagnosis

Ototoxicity is defined as the damage, reversible or irreversible, produced in the inner ear by various substances that are called ototoxic and that can cause hearing loss and/or an alteration of the vestibular system. Permanent hearing loss significantly affects quality of life and is especially important in children. The lack or delay in its detection is frequent, since it often progresses in an inconspicuous manner until it affects communication and overall development. This impact can be minimized by following a strategy of audiological monitoring of ototoxicity, which allows for its early detection and treatment. This document recommends that children who are going to be treated with cisplatin or aminoglycosides be monitored. This CODEPEH review and recommendation document focuses on the early detection, prophylaxis, otoprotection, monitoring and treatment of ototoxicity caused by aminoglycosides and platinum-based antineoplastics in the paediatric population.

Unexpected Consequences of Noise-Induced Hearing Loss: Impaired Hippocampal Neurogenesis, Memory, and Stress

Noise-induced hearing loss (NIHL), caused by direct damage to the cochlea, reduces the flow of auditory information to the central nervous system, depriving higher order structures, such as the hippocampus with vital sensory information needed to carry out complex, higher order functions. Although the hippocampus lies outside the classical auditory pathway, it nevertheless receives acoustic information that influence its activity. Here we review recent results that illustrate how NIHL and other types of cochlear hearing loss disrupt hippocampal function. The hippocampus, which continues to generate new neurons (neurogenesis) in adulthood, plays an important role in spatial navigation, memory, and emotion. The hippocampus, which contains place cells that respond when a subject enters a specific location in the environment, integrates information from multiple sensory systems, including the auditory system, to develop cognitive spatial maps to aid in navigation. Acute exposure to intense noise disrupts the place-specific firing patterns of hippocampal neurons, “spatially disorienting” the cells for days. More traumatic sound exposures that result in permanent NIHL chronically suppresses cell proliferation and neurogenesis in the hippocampus; these structural changes are associated with long-term spatial memory deficits. Hippocampal neurons, which contain numerous glucocorticoid hormone receptors, are part of a complex feedback network connected to the hypothalamic-pituitary (HPA) axis. Chronic exposure to intense intermittent noise results in prolonged stress which can cause a persistent increase in corticosterone, a rodent stress hormone known to suppress neurogenesis. In contrast, a single intense noise exposure sufficient to cause permanent hearing loss produces only a transient increase in corticosterone hormone. Although basal corticosterone levels return to normal after the noise exposure, glucocorticoid receptors (GRs) in the hippocampus remain chronically elevated. Thus, NIHL disrupts negative feedback from the hippocampus to the HPA axis which regulates the release of corticosterone. Preclinical studies suggest that the noise-induced changes in hippocampal place cells, neurogenesis, spatial memory, and glucocorticoid receptors may be ameliorated by therapeutic interventions that reduce oxidative stress and inflammation. These experimental results may provide new insights on why hearing loss is a risk factor for cognitive decline and suggest methods for preventing this decline.

Reporting Data on Auditory Brainstem Responses (ABR) in Rats: Recommendations Based on Review of Experimental Protocols and Literature

Research in hearing science is accelerating, and a wealth of data concerning auditory brainstem responses (ABR) in various animal models is published in peer-reviewed journals every year. Recently, we reviewed studies using ABR measurements in tinnitus rat models. We found significant discrepancies in the outcomes of these studies, some due to different research approaches and others due to different methodologies. Thus, the present work aimed to collect comprehensive information on all factors influencing ABR recordings in rats and compile recommendations on ABR data reporting. A questionnaire with queries about animal husbandry, transfer, handling, and the exact test conditions before, during, and after ABR recordings was sent to 125 researchers who published the relevant studies between 2015 and 2021. Eighteen researchers provided detailed answers on factors related to ABR measurements. Based on the analysis of the returned questionnaires, we identified three domains reflecting animal-, equipment-, and experiment-dependent factors that might influence the ABR outcome, thus requiring reporting in published research. The analysis of survey results led to the compilation of recommendations for reporting ABR outcomes supported by a literature review. Following these recommendations should facilitate comparative and meta-analyses of ABR results provided by various research groups.

Incidence of childhood hearing loss after in utero exposure to platinum agents

OBJECTIVE

When treated for childhood cancers, at least 50% of children exposed to platinum agents have permanent hearing loss. We determined the relative risk of childhood hearing loss after in utero exposure to platinum chemotherapy in our registry cohort.

METHOD

After exposure to platinum chemotherapy in utero, all children undergo routine newborn hearing screening. This consists of Otoacoustic Emissions. Children who failed this screen were evaluated by audiologists. For those children with hearing loss by Automated Auditory Brainstem Response, prenatal and postnatal treatment details were compared to platinum exposed children without hearing loss.

RESULTS

Three hundred and seven children were exposed to chemotherapy in utero. Four children were diagnosed with hearing loss, all exposed to platinum agents. Chemotherapy exposures included: Cisplatin/Paclitaxel (2), Etoposide/Cisplatin/Bleomycin (1), Carboplatin/Paclitaxel (1) to treat ovarian (2), or cervical cancer (2). Of the 39 platinum exposed without hearing loss: 11 children were exposed to oxaliplatin, 16 were exposed to cisplatin and 12 to carboplatin in utero. Two hundred and sixty four women received non-platinum based chemotherapy for various cancers during pregnancy. Among these, there were no cases of hearing loss. There was a significant difference in hearing loss based on exposure to platinum agents in utero compared to non-platinum-containing chemotherapy regimens, 4/43 versus 0/264, p = 0.0003. There were no statistical differences in prenatal and postnatal treatment details, including: gestational age at diagnosis, at first chemotherapy treatment, at first platinum treatment, at delivery (<32 weeks, <35 weeks, <37 weeks), gender, birthweight, birthweight percentile, rates of intrauterine growth restriction, neonatal complications or use of postnatal antibiotics between the platinum exposed children with and without hearing loss.

CONCLUSION

The only children in the registry exposed to chemotherapy who were diagnosed with hearing loss had been exposed to cisplatin or carboplatin in utero. No hearing loss occurred in children exposed to oxaliplatin, or non-platinum agents. Due to a concern for cisplatin ototoxicity, carboplatin is the preferred platinum agent for use in pregnancy when equivalent maternal survival can be expected for the particular cancer type. For newborns exposed to platinum agents in utero, newborn screening with an auditory emissions test at birth (OES) may not detect sensorineural hearing loss and auditory brainstem response testing is recommended, regardless of the newborn screening result.

Detection of unknown ototoxic adverse drug reactions: an electronic healthcare record-based longitudinal nationwide cohort analysis

Ototoxic medications can lead to significant morbidity. Thus, pre-marketing clinical trials have assessed new drugs that have ototoxic potential. Nevertheless, several ototoxic side effects of drugs may remain undetected. Hence, we sought to retrospectively investigate the potential risk of ototoxic adverse drug reactions among commonly used drugs via a longitudinal cohort study. An electronic health records-based data analysis with a propensity-matched comparator group was carried out. This study was conducted using the MetaNurse algorithm for standard nursing statements on electronic healthcare records and the National Sample Cohort obtained from the South Korea National Health Insurance Service. Five target drugs capable of causing ototoxic adverse drug reactions were identified using MetaNurse; two drugs were excluded after database-based analysis because of the absence of bilateral hearing loss events in patients. Survival analysis, log-rank test, and Cox proportional hazards regression models were used to calculate the incidence, survival rate, and hazard ratio of bilateral hearing loss among patients who were prescribed candidate ototoxic drugs. The adjusted hazard ratio of bilateral hearing loss was 1.31 (1.03–1.68), 2.20 (1.05–4.60), and 2.26 (1.18–4.33) in cimetidine, hydroxyzine, and sucralfate users, respectively. Our results indicated that hydroxyzine and sucralfate may cause ototoxic adverse drug reactions in patients. Thus, clinicians should consider avoiding co-administration of these drugs with other well-confirmed ototoxic drugs should be emphasized.

In silico prediction of drug-induced ototoxicity using machine learning and deep learning methods

Drug-induced ototoxicity has become a serious global problem, because of leading to deafness in hundreds of thousands of people every year. It always results from exposure to drugs or environmental chemicals that cause the impairment and degeneration of the inner ear. Herein, we focused on the in silico modeling of drug-induced ototoxicity of chemicals. We collected 1,102 ototoxic medications and 1,705 non-ototoxic drugs. Based on the data set, a series of computational models were developed with different traditional machine learning and deep learning algorithms implemented on an online chemical database and modeling environment. Six ML models performed best on 5-fold cross-validation and test set. A consensus model was developed with the best individual models. These models were further validated with an external validation. The consensus model showed best predictive ability, with high accuracy of 0.95 on test set and 0.90 on validation set. The consensus model and the data sets used for model development are available at https://ochem.eu/model/46566321. Besides, 16 structural alerts responsible for drug-induced ototoxicity were identified. We hope the results could provide meaningful knowledge and useful tools for ototoxicity evaluation in drug discovery and environmental risk assessment.

Naringin attenuates cisplatin- and aminoglycoside-induced hair cell injury in the zebrafish lateral line via multiple pathways

Exposure to ototoxic drugs is a significant cause of hearing loss that affects about 30 thousand children with potentially serious physical, social and psychological dysfunctions every year. Cisplatin (CP) and aminoglycosides are effective antineoplastic or bactericidal drugs, and their application has a high probability of ototoxicity which results from the death of hair cells (HCs). Here, we describe the therapeutic effect of the flavonoid compound naringin (Nar) against ototoxic effects of cisplatin and aminoglycosides include gentamicin (GM) and neomycin (Neo) in zebrafish HCs. Animals incubated with Nar (100‐400 μmol/L) were protected against the pernicious effects of CP (150‐250 μmol/L), GM (50‐150 μmol/L) and Neo (50‐150 μmol/L). We also provide evidence for the potential mechanism of Nar against ototoxicity, including antioxidation, anti‐apoptosis, promoting proliferation and hair cell regeneration. We found that mRNA levels of the apoptotic‐ and pyroptosis‐related genes are regulated by Nar both in vivo and in vitro. Finally, by proving that Nar does not affect the anti‐tumour efficacy of CP and antibacterial activity of aminoglycosides in vitro, we highlight its value in clinical application. In conclusion, these results unravel a novel therapeutic role for Nar as an otoprotective drug against the adverse effects of CP and aminoglycosides.

Natural Antioxidant and Anti-Inflammatory Compounds in Foodstuff or Medicinal Herbs Inducing Heme Oxygenase-1 Expression

Heme oxygenase-1 (HO-1) is an inducible antioxidant enzyme that catalyzes heme group degradation. Decreased level of HO-1 is correlated with disease progression, and HO-1 induction suppresses development of metabolic and neurological disorders. Natural compounds with antioxidant activities have emerged as a rich source of HO-1 inducers with marginal toxicity. Here we discuss the therapeutic role of HO-1 in obesity, hypertension, atherosclerosis, Parkinson's disease and hepatic fibrosis, and present important signaling pathway components that lead to HO-1 expression. We provide an updated, comprehensive list of natural HO-1 inducers in foodstuff and medicinal herbs categorized by their chemical structures. Based on the continued research in HO-1 signaling pathways and rapid development of their natural inducers, HO-1 may serve as a preventive and therapeutic target for metabolic and neurological disorders.

Otoprotective Effect of 2,3,4',5-Tetrahydroxystilbene-2-O-β-d-Glucoside on Gentamicin-Induced Apoptosis in Mouse Cochlear UB/OC-2 Cells

Excessive levels of reactive oxygen species (ROS) lead to mitochondrial damage and apoptotic cell death in gentamicin-induced ototoxicity. 2,3,4',5-Tetrahydroxystilbene-2-O-β-d-glucoside (THSG), a bioactive constituent, isolated from Polygonum multiflorum Thunb., exhibits numerous biological benefits in treating aging-related diseases by suppressing oxidative damage. However, its protective effect on gentamicin-induced ototoxicity remains unexplored. Therefore, here, we aimed to investigate the otoprotective effect of THSG on gentamicin-induced apoptosis in mouse cochlear UB/OC-2 cells. We evaluated the effect of gentamicin and THSG on the ROS level, superoxide dismutase (SOD) activity, mitochondrial membrane potential, nuclear condensation, and lactate dehydrogenase (LDH) release, and the expression of apoptosis-related proteins was assessed to understand the molecular mechanisms underlying its preventive effects. The findings demonstrated that gentamicin increased ROS generation, LDH release, and promoted apoptotic cell death in UB/OC-2 cells. However, THSG treatment reversed these effects by suppressing ROS production and downregulating the mitochondrial-dependent apoptotic pathway. Additionally, it increased the SOD activity, decreased the expression of apoptosis-related proteins, alleviated the levels of the apoptotic cells, and impaired cytotoxicity. To the best of our knowledge, this is the first study to demonstrate that THSG could be a potential therapeutic option to attenuate gentamicin-induced ototoxicity.

An Ototoxicity Grading System Within a Mobile App (OtoCalc) for a Resource-Limited Setting to Guide Grading and Management of Drug-Induced Hearing Loss in Patients With Drug-Resistant Tuberculosis: Prospective, Cross-Sectional Case Series

BACKGROUND

Tuberculosis (TB) affects millions of people worldwide and is treated with medication including aminoglycosides and polypeptides. Individuals respond differently to medications as a result of their genetic inheritance. These differences in genetic inheritance can result in the underdosing or overdosing of medication, which may affect the efficacy or, in the case of aminoglycosides and polypeptides used in the treatment of all forms of TB, result in ototoxicity. When ototoxicity is detected, physicians should adjust dosages to minimize further ototoxicity and hearing loss; however, there are no suitable grading systems to define significant hearing loss.

OBJECTIVE

The aim of this study was to develop a standardized grading system by making use of an electronic health (eHealth) platform to ensure that a user-friendly method was available to interpret hearing test results, calculate significant hearing loss, and provide recommendations with regard to dosage adjustments and management. It further aimed to establish the sensitivity of the newly developed grading scale.

METHODS

This grading system was developed in South Africa based on data that were obtained from an audiology and pharmacokinetic study on patients with drug-resistant TB (DR-TB) at two DR-TB units at state-run hospitals. This feasibility study employed a prospective, cross-sectional, exploratory, descriptive case series research design, with a total of 22 participants. Participants underwent audiological and pharmacological assessments at baseline and every 2 weeks for the first 3 months of treatment. Various professionals (8 in total) were subsequently involved in the development of the eHealth system, including a software engineer, four audiologists, a pharmacist, a medical doctor, and a nurse. The app underwent 14 modifications that involved aspects of data storage, ease of usability, grades, and the risk factor checklist.

RESULTS

An ototoxicity grading system within a mobile app for use by doctors, nurses, and audiologists was developed for patients with DR-TB. The purpose of this user-friendly ototoxicity calculator, OtoCalc, is to (1) assist health professionals in assessing patients for ototoxicity, (2) establish the clinical significance of ototoxicity by calculating the grade of hearing loss, (3) monitor the progression of hearing loss, and (4) enable systematic referral and management of patients according to their needs.

CONCLUSIONS

This newly developed system is more sensitive than the existing grading methods for determining ototoxicity in patients with DR-TB. This app needs to be trialed in a larger sample to establish data security, ease of use, and suitability within this population.

Use of zebrafish larvae lateral line to study protection against cisplatin-induced ototoxicity: A scoping review

AIM

The present review aimed to consolidate and analyze the recent information about the use of zebrafish in studies concerning cisplatin-induced ototoxicity and otoprotection.

MATERIAL AND METHODS

The PubMed, Web of Science, and Scopus databanks were searched using the following MESH terms: zebrafish, cisplatin, ototoxicity. The identified publications were screened according to inclusion and exclusion criteria and the 26 qualifying manuscripts were included in the full-text analysis. The experimental protocols, including cisplatin concentrations, the exposure duration and the outcome measurements used in zebrafish larvae studies, were evaluated and the reported knowledge was summarized.

RESULTS

Twenty-six substances protecting from cisplatin-induced toxicity were identified with the use of zebrafish larvae. These substances include quinine, salvianolic acid B, berbamine 6, benzamil, quercetin, dexmedetomidine, dexamethsanone, quinoxaline, edaravone, apocynin, dimethyl sulfoxide, KR-22335, SRT1720, ORC-13661, 3-MA, D-methionine, mdivi-1, FUT-175, rapamycin, Z-LLF-CHO, ATX, NAC, CYM-5478, CHCP1, CHCP2 and leupeptin. The otoprotective effects of compounds were attributed to their anti-ROS, anti-apoptotic and cisplatin uptake-blocking properties. The broadest range of protection was achieved when the experimental flow used preconditioning with an otoprotective compound and later a co-incubation with cisplatin. Protection against a high concentration of cisplatin was observed only in protocols using short exposure times (4 and 6 h).

CONCLUSIONS

The data extracted from the selected papers confirm that despite the differences between the human and the zebra fish hearing thresholds (as affected by cisplatin), the sensory cells of zebrafish and larval zebrafish are a valuable tool which could be used: (i) for the discovery of novel otoprotective substances and compounds; (ii) to screen their side effects and (iii) to extend the knowledge on the mechanisms of cisplatin-induced inner ear damage. For future studies, the development of a consensus experimental protocol is highly recommended.

Ototoxicity and Nephrotoxicity With Elevated Serum Concentrations Following Vancomycin Overdose: A Retrospective Case Series

Although a high vancomycin serum concentration is known to be associated with nephrotoxicity, its association with ototoxicity is not well known. The purpose of our study was to examine the latter association in pediatric patients, especially in cases of accidental overdose. Pediatric patients who received vancomycin at our facility between March 2010 and December 2015 with a serum trough concentration > 30 mg/L were enrolled. Age, sex, neonatal hearing screening results, estimated peak vancomycin serum concentration, duration of drug exposure, renal function, and hearing test results were collected. The estimated duration of concentrations above 30 or 80 mg/L were simulated with the Sawchuk-Zaske method. We defined a "high concentration" and "toxic concentration" of vancomycin as 30 to 80 mg/L and > 80 mg/L, respectively. Ototoxicity was assessed based on the auditory brain stem response. We identified 4 females and 2 males with normal hearing at birth. Four of the 6 patients were ≤ 3 months old. All the patients reached an estimated peak serum concentration of > 80 mg/L, and 5 exceeded 150 mg/L. The estimated duration of exposure to a high concentration and toxic concentration of vancomycin was 15 to 62 hours and 8 to 43 hours, respectively. All the patients experienced transient renal dysfunction. Although transient ototoxicity was found in 1 patient, prolonged ototoxicity was not observed in any of the patients. All the patients had received an accidental overdose of vancomycin. Prolonged hearing loss due to a high vancomycin serum concentration was not found in any of the subjects in the present report.

Monitoring Protocols for Cochlear Toxicity

The need for monitoring hearing and auditory function during drug therapy and other treatments that have the potential to cause hearing loss is well documented. Besides the main purpose of ototoxic monitoring, which is to provide feedback to the attending physician about the effects the treatment is having on the auditory system, it is also helpful in setting expectations for the patient and his/her family about the communication issues that may result from the drug therapy. This article will review tests available to an audiologist, both subjective and objective, that can be used to effectively monitor hearing levels and auditory function during treatment. Published guidelines and various ototoxic monitoring protocols are reviewed regarding tests administered, what constitutes a significant change in test results and how these findings are reported, and the impact significant changes may have on the course of treatment. Test protocols from different institutions are compared for both similarities and contrasts. Effective scheduling and test location are key to a successful monitoring program. Finally, the need to streamline ototoxic monitoring of hearing and auditory function to reduce test time and make it less stressful and tiresome on the patient will be considered.

C-phycocyanin from Limnothrix Species KNUA002 Alleviates Cisplatin-Induced Ototoxicity by Blocking the Mitochondrial Apoptotic Pathway in Auditory Cells

Ototoxicity, or adverse pharmacological effects on the inner ear or auditory nerve, is a common side effect of cisplatin, a platinum-based drug widely used in anticancer chemotherapy. Although the incidence of ototoxicity is high among patients that receive cisplatin therapy, there is currently no effective treatment for it. The generation of excessive reactive oxygen species (ROS) is considered to be the major cause of cisplatin-induced ototoxicity. C-phycocyanin (C-PC), a blue phycobiliprotein found in cyanobacteria and red algae, has antioxidant and anticancer activities in different experimental models in vitro and in vivo. Thus, we tested the ability of C-PC from Limnothrix sp. KNUA002 to protect auditory cells from cisplatin-induced ototoxicity in vitro. Pretreatment with C-PC from Limnothrix sp. KNUA002 inhibited apoptosis and protected mitochondrial function by preventing ROS accumulation in cisplatin-treated House Ear Institute-Organ of Corti 1 (HEI-OC1) cells, a mouse auditory cell line. Cisplatin increased the expression of Bax and reduced the expression of Bcl-2, which activate and inhibit, respectively, the mitochondrial apoptotic pathway in response to oxidative stress. Pretreatment with C-PC prior to cisplatin treatment caused the Bax and Bcl-2 levels to stay close to the levels in untreated control cells. Our results suggest that C-PC from Limnothrix sp. KNUA002 protects cells against cisplatin-induced cytotoxicity by inhibiting the mitochondrial apoptotic pathway.

Global burden of hearing impairment and ear disease

Background

Hearing loss can present at birth or be acquired as a result of illness, middle-ear disease, injury, age, overuse of certain medications, and/or induced by exposure to damaging noise levels. There are serious short-term consequences for people living with hearing impairment, including the effects on language acquisition, education, employment and overall wellbeing. There are also complex long-term implications.

Objectives

This review aimed to present some of the leading causes of ear disease and hearing loss globally, and to identify their impact at both an individual and societal level.

Ototoxicity: A Challenge in Diagnosis and Treatment

Ototoxicity is the pharmacological adverse reaction affecting the inner ear or auditory nerve, characterized by cochlear or vestibular dysfunction. The panorama of drug-induced hearing loss has widened over last few decades. Although ototoxic medications play an imperative role in modern medicine, they have the capacity to cause harm and lead to significant morbidity. Evidence has shown early detection of toxicity through prospective ototoxicity monitoring allows for consideration of treatment modifications to minimize or prevent permanent hearing loss and balance impairment. Although many ototoxicity monitoring protocols exist, their practicality is questionable due to several factors. Even though the existing protocols have proven to be effective, certain lacunae in practice have been encountered due to discrepancies among recommended protocols. Implementation of these protocols is mostly held back due to the incapacitated status of the patient. The choice of early ototoxicity identification techniques is still debatable due to variables such as high degree of sensitivity, specificity and reliability, less time consumption and less labour-intensive to the patient. Hence, the diagnosis and effective treatment of ototoxicity is challenging, even today. A stringent protocol with more practicality encompassing all elements aimed at profiling the effects of ototoxicity is greatly needed. This review describes an efficient application of ototoxicity monitoring and treatment protocol as an attempt to reduce the challenges in diagnosis and management of ototoxicity.

Chloroquine gestational use in systemic lupus erythematosus: assessing the risk of child ototoxicity by pure tone audiometry

The objective of this study was to assess child chloroquine ototoxicity after its use during the gestational period in systemic lupus erythematosus (SLE). Nineteen children over four years old were evaluated: nine were exposed to chloroquine diphosphate (CDP) during gestation and 10 were born from mothers that did not take this drug before conception or anytime during pregnancy (CONTROL). Pure tone audiometry was performed in all children and high and low frequency threshold means were compared to evaluate the hearing status. All nine mothers taking CDP were exposed to this drug at least during the first trimester of pregnancy (56% during the whole gestational period) and the mean time of CDP use was 6.1 + 2.9 months. No significant difference was found in children of CDP and CONTROL groups regarding age (7.6 + 4.4 versus 12.3 + 7.2 years; P 0.10, respectively) and gender (P 0.65). Pure tone high frequency thresholds, which are the first to be affected by ototoxic drugs, presented within normal limits in children exposed or not to CDP (8.5 + 5.0 versus 7.4 + 3.6 dBHL; P 0.55, respectively). Likewise, the mean hearing thresholds at low frequencies were also similar in both groups (11.4 + 4.5 versus 11.9 + 3.0 dBHL; P 0.66). In conclusion, child in utero exposure to chloroquine diphosphate does not seem to induce hearing impairment as measured by pure tone audiometry, reinforcing its safe use during pregnancy of lupus patients.

Curcuma longa (curcumin) decreases in vivo cisplatin-induced ototoxicity through heme oxygenase-1 induction

HYPOTHESIS

To investigate whether curcumin may have in vivo protective effects against cisplatin ototoxicity by its direct scavenger activity and/or by curcumin-mediated upregulation of HO-1.

BACKGROUND

Cisplatin-induced ototoxicity is a major dose-limiting side effect in anticancer chemotherapy. A protective approach to decrease cisplatin ototoxicity without compromising its therapeutic efficacy remains a critical goal for anticancer therapy. Recent evidences indicate that curcumin exhibits antioxidant, anti-inflammatory, and chemosensitizer activities.

METHODS

In male adult Wistar rats, a curcumin dose of 200 mg/kg, selected from a dose-response curve, was injected 1 hour before cisplatin administration and once daily for the following 3 days. A single dose of cisplatin (16 mg/kg) was administered intraperitoneally. Rats were divided as follows: 1) control, 2) curcumin control, 3) vehicle control, 4) cisplatin, 5) cisplatin+ vehicle, and 6) curcumin+cisplatin. ABRs were measured before and at Days 3 and 5 after cisplatin administration. Rhodamine-phalloidin staining, 4-hydroxy-2-nonenal and heme-oxigenase-1 immunostainings, and Western blot analyses were performed to assess and quantify OHC loss, lipid peroxidation, and the endogenous response to cisplatin-induced damage and to curcumin protection.

RESULTS

Curcumin treatment attenuated hearing loss induced by cisplatin, increased OHC survival, decreased 4-HNE expression, and increased HO-1 expression.

CONCLUSION

This preclinical study demonstrates that systemic curcumin attenuates ototoxicity and provides molecular evidence for a role of HO-1 as an additional mediator in attenuating cisplatin-induced damage.

The protective role of thymoquinone in the prevention of gentamicin ototoxicity

OBJECTIVE

To investigate the potential protective effect of thymoquinone in gentamicin-induced ototoxicity through auditory brain stem responses (ABR) testing and histomorphological evaluation of the cochlea.

METHODS

This study was conducted on 48 adult female Sprague-Dawley rats that were randomized into 4 groups. Group 1 received intraperitoneal gentamicin; group 2 received intraperitoneal gentamicin plus corn oil solution; group 3 received intraperitoneal thymoquinone; and group 4 received intraperitoneal gentamicin plus thymoquinone. All groups received the drugs (once daily) in the above-mentioned protocols over 15 days. After conducting repeated ABR measurements, the rats were sacrificed, and their cochleae were isolated.

RESULTS

ABR thresholds were preserved in the gentamicin plus thymoquinone group when compared with the group receiving gentamicin alone. There were fewer TUNEL-positive cells and caspase-3 and caspase-9 expressions were weaker in the inner and outer hairy cells of the organ of Corti in the gentamicin plus thymoquinone group compared with the group receiving gentamicin alone.

CONCLUSION

The ABR values and number of apoptotic cells did not significantly increase in the group receiving gentamicin plus thymoquinone when compared to the group receiving gentamicin alone. Again, the cochlear histomorphological findings were supportive of the auditory findings. In light of these findings, we conclude that gentamicin-induced ototoxicity may be prevented by thymoquinone use in rats.

The global burden of disabling hearing impairment: a call to action

At any age, disabling hearing impairment has a profound impact on interpersonal communication, psychosocial well-being, quality of life and economic independence. According to the World Health Organization's estimates, the number of people with such impairment increased from 42 million in 1985 to about 360 million in 2011. This last figure includes 7.5 million children less than 5 years of age. In 1995, a "roadmap" for curtailing the burden posed by disabling hearing impairment was outlined in a resolution of the World Health Assembly. While the underlying principle of this roadmap remains valid and relevant, some updating is required to reflect the prevailing epidemiologic transition. We examine the traditional concept and grades of disabling hearing impairment - within the context of the International Classification of Functioning, Disability and Health - as well as the modifications to grading that have recently been proposed by a panel of international experts. The opportunity offered by the emerging global and high-level interest in promoting disability-inclusive post-2015 development goals and disability-free child survival is also discussed. Since the costs of rehabilitative services are so high as to be prohibitive in low- and middle-income countries, the critical role of primary prevention is emphasized. If the goals outlined in the World Health Assembly's 1995 resolution on the prevention of hearing impairment are to be reached by Member States, several effective country-level initiatives - including the development of public-private partnerships, strong leadership and measurable time-bound targets - will have to be implemented without further delay.

The protective effect of Ginkgo biloba extract against experimental cisplatin ototoxicity: animal research using distortion product otoacoustic emissions

BACKGROUND

Cisplatin, an effective therapeutic agent for various human cancers, has dose-limiting side effects of ototoxicity and nephrotoxicity. Cisplatin ototoxicity is thought to result from increased amounts of toxic free radicals or cell membrane changes leading to increased intracellular calcium content. Ginkgo biloba extract prevents lipid peroxidation, decreases intracellular free oxygen radical levels, regulates the cell membrane calcium transport mechanism and prevents cell death. This study aimed to investigate the protective effect of Ginkgo biloba extract against cisplatin-induced ototoxicity in rats.

METHODS

Twenty Wistar albino rats with normal hearing (confirmed by distortion product otoacoustic emission testing prior to cisplatin application) were randomly allocated to two groups. Both groups received a single intraperitoneal dose of cisplatin (12 mg/kg). Group two also received daily intraperitoneal doses of Ginkgo biloba extract (100 mg/kg) for 10 days. Distortion product otoacoustic emission measurements were repeated on days 10 and 17 and signal-to-noise ratios were compared.

RESULTS

Compared with group one, group two had significantly better distortion product otoacoustic emission results at 3, 4, 6 and 8 kHz on days 10 and 17.

CONCLUSION

These findings suggest that Ginkgo biloba extract protects the inner ear against cisplatin-induced ototoxicity.

Apoptosis in acquired and genetic hearing impairment: the programmed death of the hair cell

Apoptosis is an important physiological process. Normally, a healthy cell maintains a delicate balance between pro- and anti-apoptotic factors, allowing it to live and proliferate. It is thus not surprising that disturbance of this delicate balance may result in disease. It is a well known fact that apoptosis also contributes to several acquired forms of hearing impairment. Noise-induced hearing loss is the result of prolonged exposure to excessive noise, triggering apoptosis in terminally differentiated sensory hair cells. Moreover, hearing loss caused by the use of therapeutic drugs such as aminoglycoside antibiotics and cisplatin potentially may result in the activation of apoptosis in sensory hair cells leading to hearing loss due to the "ototoxicity" of the drugs. Finally, apoptosis is a key contributor to the development of presbycusis, age-related hearing loss. Recently, several mutations in apoptosis genes were identified as the cause of monogenic hearing impairment. These genes are TJP2, DFNA5 and MSRB3. This implies that apoptosis not only contributes to the pathology of acquired forms of hearing impairment, but also to genetic hearing impairment as well. We believe that these genes constitute a new functional class within the hearing loss field. Here, the contribution of apoptosis in the pathology of both acquired and genetic hearing impairment is reviewed.

Highly active antiretroviral therapy: Does it Sound toxic?

Objective

The main objective of the current study is to monitor the auditory status in a group of adults with AIDS, receiving Highly Active Antiretroviral Therapy (HAART) (3TC -lamivudine, D4T – stavudine, and efavirenz) in a hospital outpatient clinic in Gauteng. A total sample of 54 adults (between the ages of 18 and 50 years) in the experimental group and 16 in the control group were assessed prospectively following a repeated measures design. All participants were assessed at baseline at three months, and at six months into the treatment.

Materials and Methods

The participants underwent case history interviews and medical record reviews, otoscopy, and tympanometry, as well as conventional pure tone audiometry and distortion product otoacoustic emission testing. Both descriptive and inferential statistics were used to analyze the data.

Results

On audiological monitoring, statistically significant changes (P<0.05) were established, only in the experimental group, for pure tone audiometry — with clinically significant changes found at high frequencies. Statistically significant changes with clinically significant changes were obtained for distortion product otoacoustic emissions (DPOAEs) in the experimental group, particularly at high frequencies — implying subclinical hearing function changes; while lack of statistically significant changes with no clinically significant changes were found in the control group. The subclinical hearing changes in the experimental group were also evident in the findings of the subclinical hearing loss group, who, although they had normal pure tone function after six months of follow up, presented with clinical changes on DPOAEs at 6 and 8 kHz.

Conclusions

Findings highlight the need for closer monitoring of the effects of antiretroviral drugs (ARVs) on hearing, through the use of more sensitive tools of assessment when conducting drug trials.

The protective role of tiopronin in cisplatin ototoxicity in Wistar rats

The purpose of this study was to evaluate cisplatin-induced ototoxicity and the protective effects of tiopronin. Twenty-four adult Wistar rats served as subjects and were divided into three groups. Eight rats receiving only saline (group A) were used as controls. Eight rats received cisplatin (2 mg/kg) injections (group B) and eight rats received cisplatin and tiopronin (300 mg/kg) (group C) for 8 consecutive days. Both ears of all animals were tested by DPOAE before treatment and on the 4th and 9th days. Seventy-two hours after the final recording session, all animals were killed, and the left cochleas were prepared for electron microscopy and analysed. DPOAE responses were significantly reduced in group B compared to controls (p<0.05). When tiopronin was added, DPOAE responses were significantly increased compared to those obtained with the administration of cisplatin alone (p<0.05). The cochleogram showed that tiopronin had a significant protective effect in the basal half and in the lower half of the middle turn. We conclude that tiopronin, a drug effective in protecting against cisplatin nephrotoxicity, is also effective in protecting against cisplatin ototoxicity.

Análise de prontuários de pacientes oncológicos quanto ao monitoramento auditivo

OBJETIVO: realizar uma análise retrospectiva dos prontuários de pacientes oncológicos quanto ao monitoramento auditivo. MÉTODOS: foram utilizados os prontuários dos pacientes em atendimento durante os meses de setembro a novembro de 2006. A amostra constituiu-se de 25 prontuários de indivíduos com idade compreendida entre um e 53 anos. Foram analisados os dados quanto aos seguintes aspectos: idade, sexo, classificação do câncer, tempo de apresentação da doença, medicamentos utilizados, tempo de tratamento quimioterápico, doenças associadas, realização de avaliação otorrinolaringológica e audiológica. RESULTADOS: verificou-se a falta de acompanhamento audiológico e otorrinolaringológico. A Vincristina foi o medicamento ototóxico mais utilizado. O tipo de câncer de maior ocorrência no setor foi a Leucemia Linfocítica aguda. O tempo que os indivíduos apresentavam o câncer foi de aproximadamente 16 meses e o tempo de tratamento quimioterápico desses pacientes foi em torno de 11 meses. Observou-se, também, a presença de doenças associadas ao câncer nos indivíduos pesquisados. CONCLUSÃO: constatou-se a necessidade de se instalar programas de monitoramento auditivo nos setores que realizam quimioterapia em pacientes oncológicos, uma vez que este tratamento utiliza medicamentos ototóxicos em diversas patologias.

Drug-related nephrotoxic and ototoxic reactions : a link through a predictive mechanistic commonality

BACKGROUND

Drug-induced ototoxicity is a subject of interest because many diseases are treated with drugs that have potential toxic effects on the ear. There is evidence that both inner ear and kidney tissue are immunologically, biochemically and functionally related. It has been suggested that drugs that influence the transport of sodium and/or potassium change ionic homeostasis in the inner ear and, hence, induce functional disturbances such as hearing loss, tinnitus and vertigo.

OBJECTIVES

To assess whether renal suspected adverse drug reactions (sADRs) have predictive value for ear and labyrinth adverse drug reactions (ADRs) and whether drug classes involved have influence ion transport systems.

STUDY DESIGN

Data were obtained from the Netherlands Pharmacovigilance Centre Lareb. The study base comprised all reports of sADRs up until 1 January 2007. Cases were all sADRs for relevant renal disorders and all sADRs for relevant ear disorders. All other reported sADRs were selected as 'non-cases'. The relationship between drug classes and renal, ear and labyrinth sADRs was evaluated by calculating reporting odds ratios (RORs). An ROR > or = 1.50 was regarded as a cut-off value for an association. Drug classes were classified into four groups: (A) ROR kidney <1.50 and ROR ear <1.50 or no reports on ear sADRs (reference group); (B) ROR kidney <1.50 and ROR ear > or = 1.50; (C) ROR kidney > or = 1.50 and ROR ear <1.50 or no reports on ear sADRs; and (D) ROR kidney > or = 1.50 and ROR ear > or = 1.50. For each group, we calculated odds ratios (ORs) for the association between the group classification and the effect on ion channels/ion transport systems in kidney and ear tissues.

RESULTS

Of 193 drug classes with relevant ADRs for renal disorders, 120 drug classes also had reports on ototoxic reactions. Fourteen out of 120 drug classes had an ROR > or = 1.50 for the association between the drug class and both renal and ear sADRs. Among these drug classes were several with a well known ability to induce renal (adverse) effects and ear and labyrinth disorders, such as loop diuretics, aminoglycosides and quinine. We found that one mechanistic commonality of the drug classes mentioned in the reports was the ability to affect ion transport systems. The percentage of drugs having this property differed between the four groups. The ORs for groups D and B were significantly higher compared with the reference group (OR 12.2, 95% CI 3.0, 30.5 and OR 8.7, 95% CI 2.4, 18.7, respectively), whereas there was no association for group C.

CONCLUSION

Our data suggest that renal sADRs as such are not a marker for drug-induced ear and labyrinth disorders. However, the ability of drugs to act on ion channels or ion transport systems and, therefore, have an influence on ionic homeostasis in the kidney and ear might be a predictor for the possible occurrence of drug-related ototoxicity.

Ototoxicity

This paper reviews intriguing recent findings on the mechanisms of drug induced hearing loss caused by two major classes of therapeutic agents: the aminoglycoside antibiotics and cisplatin. Both drug categories are nephrotoxic as well as ototoxic. Aminoglycosides and cisplatin target the outer hair cells in the basal turn of the cochlea to cause high frequency sensorineural hearing loss in a substantial percentage of patients treated with these drugs. Each group of agents appears to generate reactive oxygen species within the cochlea that trigger downstream mechanisms leading to cell death. Various protective agents including antioxidants show promise in protecting the inner ear from damage in experimental animals. The only successful double-blind, placebo controlled clinical trial using a protective agent to prevent ototoxicity was carried out in China. Aspirin or placebo was given in combination with gentamicin. A significant decrease in hearing loss was observed. Successful clinical implementation of protective agents will require a cautious approach, so that the therapeutic effect of the anti-infective agent or anti-neoplastic drug is not attenuated. This may require novel methods of administration of protective agents, such as injection within the middle ear. This would provide a maximal dose of protective agent without systemic interference with the desired effect of the ototoxic agent.

Absence of cochleotoxicity measured by standard and high-frequency pure tone audiometry in a trial of once- versus three-times-daily tobramycin in cystic fibrosis patients

We undertook assessment of hearing in patients with cystic fibrosis who were taking part in a large randomized controlled trial of once- versus three-times-daily tobramycin for pulmonary exacerbations of cystic fibrosis (the TOPIC study). All patients were eligible to have standard pure tone audiometry performed across the frequency range of 0.25 to 8 kHz. High-frequency pure tone audiometry over 10 to 16 kHz was also performed with a subset of patients. Audiometry was undertaken at the start of tobramycin treatment, at the end of a 14-day course of treatment, and at follow-up 6 to 8 weeks later. We enrolled 244 patients, of whom 219 (125 children and 94 adults) completed treatment. Nineteen patients were excluded from analysis due to abnormal baseline audiometry. Complete pre- and posttreatment standard audiological data were obtained for 168/219 patients. We found no significant differences in hearing thresholds when they were assessed at the baseline, at the end of treatment, and at follow-up 6 to 8 weeks later were compared. In addition, no significant differences in hearing thresholds were detected between treatment regimens. Similar results were obtained for the subset of 63/168 patients who underwent high-frequency audiometry. We conclude that for a single 14-day course of tobramycin treatment in patients with cystic fibrosis with no preexisiting auditory deficit, no measurable effect on hearing was apparent with either once- or three-times-daily treatment. Estimation of the cumulative cochleotoxic risk in cystic fibrosis patients due to repeated aminoglycoside therapy, as evidenced by the patients excluded from this study due to hearing loss, also requires further characterization.

Race and sex differences in age-related hearing loss: the Health, Aging and Body Composition Study

OBJECTIVES

To determine the prevalence of and risk factors for hearing loss in a sample of 2,052 older adults (aged 73-84; 46.9% male, 37.3% black) enrolled in the Health, Aging and Body Composition (Health ABC) Study.

DESIGN

Cross-sectional analysis of a longitudinal cohort study.

SETTING

Pittsburgh, Pennsylvania, and Memphis, Tennessee, areas.

PARTICIPANTS

Random sample of Medicare beneficiary subjects enrolled in the Health ABC program from 1997 to 1998. They included 2,052 individuals: 660 white men (32.2%), 631 white women (30.8%), 310 black men (15.1%), and 451 black women (22.0%). Participants ranged in age from 73 to 84, with a mean age of 77.5.

MEASUREMENTS

Hearing sensitivity was measured using pure-tone threshold testing. Hearing loss was defined based on two averages of hearing thresholds: 500, 1,000, and 2,000 Hz greater than 25-decibel (dB) hearing level (HL) (hearing loss); and 2,000, 4,000, and 8,000 Hz greater than 40-dB HL (high-frequency hearing loss). Potential hearing loss correlates, including demographics, medical history, ototoxic medication use, occupational noise exposure, and lifestyle factors, were collected via questionnaire.

RESULTS

The prevalence of hearing loss was 59.9%; the prevalence of high-frequency hearing loss was 76.9%. Hearing loss was most common in white men, followed by white women, black men, and black women. Older age, white race, diabetes mellitus, cerebrovascular disease, smoking, poorer cognitive status, occupational noise exposure, and ear surgery were associated with hearing loss after multivariable adjustment. Race- and sex-specific risk factors included higher blood pressure and occupational noise exposure (white men), poorer cognitive status and smoking (black women), and low total hip bone mineral density (black men). Possible protective factors included salicylate use (overall sample, black men) and moderate alcohol intake (black women).

CONCLUSION

Hearing loss was extremely common in this population. Because many of the identified hearing loss risk factors are modifiable, some of the burden associated with hearing loss in older people should be preventable.

[Hypoacusis after the neonatal period. Situations requiring hearing assessment]

INTRODUCTION

Because hearing plays a major role in language development, pediatric hypoacusis is especially damaging. The high frequency of hearing impairment in newborns and the need for an early diagnosis have led to the establishment of neonatal screening. Nevertheless, there are other situations which may compromise hearing quality in later stages and it is essential to identify them in order to be able to provide early and effective treatment.

OBJECTIVES

To describe the most frequent reasons for referring patients for hearing evaluation to a third level hospital and to identify common situations that require hearing assessment among the pediatric population.

PATIENTS AND METHODS

The clinical histories of 197 non-neonates evaluated for hypoacusis were reviewed. Clinical parameters and diagnosis were compared in patients with impaired and normal hearing.

RESULTS

One hundred sixty-one patients had no previous known hypoacusis. The main reason for evaluation was suspicion by the family or child minder (53.4 %), followed by language underdevelopment. In the first examinations 78 children had hypoacusis (48.4 %), which was more frequently bilateral than unilateral. In 29.5 % of hypoacusic patients, the disease was related to recurrent otitis or adenoiditis and in 25.6 % it was genetic. The most frequent antecedent was deaf relatives in hypoacusic patients and abnormal phenotypes in children with normal hearing. Three patients with previous bacterial meningitis were studied and two of these had hypoacusis.

CONCLUSIONS

Hypoacusic evaluation outside the context of newborn screening is mainly motivated by clinical suspicion of hypoacusis or language underdevelopment. Other situations such as recurrent otitis with effusion, syndromic phenotypic characteristics or bacterial meningitis are related to hearing problems and therefore require detailed evaluation.

The use of zebrafish for assessing ototoxic and otoprotective agents

Zebrafish and other fish exhibit hair cells in the lateral-line neuromasts which are structurally and functionally similar to mammalian inner ear hair cells. To facilitate drug screening for ototoxic or otoprotective agents, we report a straightforward, quantitative in vivo assay to determine potential ototoxicity of drug candidates and to screen otoprotective agents in zebrafish larva. In this study, a fluorescent vital dye, DASPEI (2-(4-(dimethylamino)styryl)-N-ethylpyridinium iodide), was used to stain zebrafish hair cells in vivo and morphometric analysis was performed to quantify fluorescence intensity and convert images to numerical endpoints. Various therapeutics, including gentamicin, cisplatin, vinblastine sulfate, quinine, and neomycin, which cause ototoxicity in humans, also resulted in hair cell loss in zebrafish. In addition, protection against cisplatin-induced ototoxicity was observed in zebrafish larva co-treated with cisplatin and different antioxidants including, glutathione (GSH), allopurinol (ALO), N-acetyl l-cysteine (l-NAC), 2-oxothiazolidine-4-carboxylate (OTC) and d-methionine (d-MET). Our data indicate that results of ototoxicity and otoprotection in zebrafish correlated with results in humans, supporting use of zebrafish for preliminary drug screening.

Minocycline prevents gentamicin-induced ototoxicity by inhibiting p38 MAP kinase phosphorylation and caspase 3 activation

Aminoglycosides are commonly used antibiotics that often induce ototoxicity leading to permanent hair cell loss and hearing impairment. We hereby examined whether minocycline protects hair cells from gentamicin-induced hair cell damage. Two millimolar gentamicin significantly induced outer hair cell damage and the addition of minocycline to gentamicin-treated explants significantly increased hair cell survival in a dose-dependent manner. Additionally, we demonstrated that gentamicin induced p38 MAPK phosphorylation, cytochrome c release, and caspase 3 activation in these cells and these remarkable changes were blocked by minocycline treatments. Furthermore, we showed that the inhibitor of p38 MAPK or the inhibitor of caspase 3 only partially blocked gentamicin-induced hair cell damage, and the pretreatment of explants with the inhibitor of p38 MAPK and the inhibitor of caspase 3 together exerted a synergic protective effect against gentamicin-induced hair cell damage. Our results suggest that minocycline blocks gentamicin-induced hair cell loss possibly by inhibition of three mechanisms: p38 MAPK phosphorylation, cytochrome c release, and caspase 3 activation. This finding may explain why minocycline has protective activity in a variety of apoptotic models. Therapeutic intervention by using minocycline or related drugs may be a novel means for preventing inner ear injury following the use of aminoglycoside.

Escherichia coli infections in newborn puppies--clinical and epidemiological investigations

Epidemiological analyses were performed in five breeding kennels with Escherichia coli infections in newborn pups using pulsed field gel electrophoresis (PFGE). Previous reports demonstrated the high discriminatory power of this method and its usefulness for detecting epidemiologically related isolates. A total of 113 E. coli strains were isolated from vagina, faeces, oral cavity, milk and organs from 19 adult dogs, and 57 diseased or dead pups from 12 litters. Restriction enzyme analyses were performed using XbaI and BlnI digests and the resulting 91 DNA patterns were aligned for comparison. The results showed that a total of 60% of E. coli strains from progeny were also found in vaginal samples of the mothers. Another bacterial source was the faeces found within the kennels. One instance of milk and oral cavity isolates of the mother was found to be identical with strains isolated from the pups. The results indicate that for repeated cases of E. coli infections in neonates, diagnostic procedures of vaginal and faecal swabs from dams result in isolation of the responsible bacteria with high probability and further suggest that preterm treatment could help to control bacterial diseases and losses in pups. In addition, the observation that two canine strains were found to be identical with an E. coli strain isolated from a human case of diarrhoea strongly supports the canine reservoir hypothesis.

Screening and prevention of hearing loss in children

Congenital hearing loss is the most common neurosensory handicap in neonates. Recently, technology has become available that has allowed states to implement universal screening programs at a relatively low cost and with minimal expertise needed for hospital personnel to operate the screening machines. In successful programs, the age of diagnosis has been reduced from 2(1/2) years to 3 to 6 months. Children diagnosed with hearing loss before speech develops have been shown to have better speech and language outcomes than those who are diagnosed later. Strategies for screening and early intervention are discussed, as well as the causes, prevention, and treatment of more common forms of childhood hearing loss.