The Detrimental and Beneficial Functions of Macrophages After Cochlear Injury

Macrophages are the main intrinsic immune cells in the cochlea; they can be activated and play a complicated role after cochlear injury. Many studies have shown that the number of macrophages and their morphological characteristics within the major cochlear partitions undergo significant changes under various pathological conditions including acoustic trauma, ototoxic drug treatment, age-related cochlear degeneration, selective hair cell (HC) and spiral ganglion neuron (SGN) elimination, and surgery. However, the exact role of these macrophages after cochlear injury is still unclear. Regulating the migration and activity of macrophages may be a therapeutic approach to reduce the risk or magnitude of trauma-induced hearing loss, and this review highlights the role of macrophages on the peripheral auditory structures of the cochlea and elucidate the mechanisms of macrophage injury and the strategies to reduce the injury by regulating macrophage.

Hair Cell Protection from Ototoxic Drugs

Hearing loss is often caused by death of sensory hair cells (HCs) in the inner ear. HCs are vulnerable to some ototoxic drugs, such as aminoglycosides(AGs) and the cisplatin.The most predominant form of drug-induced cell death is apoptosis. Many efforts have been made to protect HCs from cell death after ototoxic drug exposure. These mechanisms and potential targets of HCs protection will be discussed in this review.And we also propose further investigation in the field of HCs necrosis and regeneration, as well as future clinical utilization.

A validation study of auditory function in an aminoglycoside-furosemide ototoxicity mouse model: Auditory brainstem response and distortion product otoacoustic emissions

Sensorineural hearing loss due to ototoxic drugs remains as a conflict as the treatment option with aminoglycosides. Ototoxic mouse model was produced with the administration of ototoxic drugs aminoglycoside kanamycin and loop-diuretic furosemide, thus validation of auditory function of the mouse model is needed to determine the efficacy of the drugs. Kanamycin sulfate 550 mg/kg (VWR life sciences, PA, USA) and furosemide 130 mg/kg (Lasix, Handok, Korea) were administered through subcutaneous and intraperitoneal injection respectively. Auditory brainstem response and distortion otoacoustic emission tests were performed on days 3,5,7,10,14 post administration of the ototoxic drug. Thresholds in response to the stimulus given in the auditory brainstem recordings and distortion otoacoustic emission tests were obtained. The hearing threshold shift to high stimulus intensity was observed post administration of the ototoxic drug. Latency of the ABR peak waves were recorded and analyzed, latency delay was observed as hearing threshold increases. These findings will further support in the application of this animal model in various studies regarding ototoxic hearing loss.

Awareness of Ototoxicity among Medical Doctors in Assam

Introduction Previous literature has reported ill-effect of ototoxic drug on hearing and balance. Present study investigated awareness among medical doctors for the same. Method A total of 55-medical doctors of multiple specialties from Assam, India participated in the present study. A total of 14 questions with Likert Scale based scoring pattern were framed and validated for the present study. Results Outcome of the present study showed high awareness percentage about side effect ototoxic drugs was obtained, which was a satisfying outcome. Conclusion While low audiological referral and consultation awareness was identified as an area of concern.

Awareness And Abuse Of Ototoxic Drugs Among Health Professionals In Federal Teaching Hospital, Ido-Ekiti

Background of study—The challenge of hearing loss is global but worse in Africa. It heavily weighs adversely on the national economy, occupational productivity and social integration on the Individual and family affected and on the community and society at large. Injury to the ear which may lead to hearing loss have been attributed to many factors, one of the major factors, being drugs that are injurious to the ear commonly called ototoxic drugs. Other damaging factors are infections, noise, genetics and metabolic systemic diseases. The menace of ototoxic drugs is devastating in Africa because there is no legislation yet against these drugs hence they are still easily purchased without medical prescription. There are over 200 known ototoxic medications (both prescribe drugs and over-the-counter) in the market today. This study was therefore aimed at assessing awareness and abuse of ototoxic drug among health care professionals in a federal teaching hospital in Nigeria as a preliminary study to comprehensive solution to the challenges of hearing loss in Nigeria. Methodology—A descriptive cross-sectional quantitative study with purposive sampling technique was used as the research design which is aimed at determining the awareness and abuse of ototoxic drugs among health professionals in a Federal Teaching Hospital A sample size of 365 participants was calculated for the research study but only 191 persons participated in the study comprising of 111 nurses, 47 doctors, 33 pharmacists. Semi- structured questionnaires were administered to the target group; Test-retest method was used to test the reliability of the questionnaire. Data was analyzed using SPSS and analysis was done at both univariate and bivariate levels. Result—The findings from the study revealed that there was a high level of awareness of ototoxic drugs among health professionals (94.8%) but prevalence (66.5%) level of ototoxic drug was also high. Majority of the respondent have high level of awareness about ototoxic drugs, therefore use some of the drugs with precaution but it was found however that the prevalence of ototoxic drug was still high and this is found to be attributed to other compelling factors such as reduced price, readily available and shorter medication regime. Findings from the study also revealed that there is a significant relationship between level of education of respondents and their awareness about ototoxic drugs but there is no significant relationship between the profession of respondents and their awareness of ototoxic drug use.

Audiological Abnormalities in Vitiligo Patients: A Hospital-Based Cross-Sectional Study

Introduction There are some discrepancies in the literature about the influence of vitiligo on auditory functions. According to some authors, vitiligo influences hearing, whereas others question such influence. Therefore, we conducted a study to evaluate audiological functions in vitiligo patients. Objectives To determine the effect of vitiligo on auditory functions. Methods A hospital-based observational study was done from January 2017 to July 2017. Clinically diagnosed cases of vitiligo were enrolled for the study. A complete otological examination was conducted in all patients. Results Fifty-two patients (male: female 28:24) were included in the study. Ten patients (19.2%) had sensorineural hearing loss (SNHL). Seven patients (13.5%) had bilateral and 3 (5.7%) had unilateral SNHL. High frequency loss was seen in 17 out of 20 ears (10 affected patients), 6 ears had both low and high-frequency hearing loss. Of 12 ears with speech frequency involvement, mild hearing loss was seen in 5 and moderate to severe in 1 ear. Most cases of SNHL were detected in the age group 41 to 60 years old (63.6%), which was statistically significant (p-value 0.00). Conclusion The results of this study suggest that vitiligo patients require routine monitoring for auditory functions for early identification of SNHL. Older subjects with vitiligo might be at a higher risk for audiological abnormalities. These patients should also be informed regarding the associated risk with noise and ototoxic drug exposure.

Secondary Degeneration of Auditory Neurons after Topical Aminoglycoside Administration in a Gerbil Model

Hair cells in the cochlea can be damaged by various causes. Damaged hair cells can lead to additional destruction of parts of the auditory afferent pathway sequentially, which is called secondary degeneration. Recently, researches regarding cochlear implants have been actively carried out for clinical purposes; secondary degeneration in animals is a much more practical model for identifying the prognosis of cochlear implants. However, an appropriate model for this research is not established yet. Thus, we developed a secondary degeneration model using an ototoxic drug. 35 gerbils were separated into four different groups and kanamycin was applied via various approaches. ABR was measured several times after drug administration. SGCs were also counted to identify any secondary degeneration. The results showed that outer and inner HCs were damaged in all kanamycin-treated groups. Twelve weeks after kanamycin treatment, the round window membrane injection group showed severe subject differences in hair cells and SGC damage, whereas the gelfoam group showed consistent and severe damage in hair cells and SGCs. In this study, we successfully induced secondary degeneration in hair cells in a gerbil model. This model can be used for various purposes in the hearing research area either for treatment or for preservation.