A review on medicinal plants used for treating ototoxicity and acoustic trauma induced hearing loss

Hearing loss induced by chemotherapy and acoustic trauma is mainly associated with two factors, free radical formation and apoptosis pathway activation. Despite numerous efforts on reducing the effects of these factors, no definite strategy is still determined to interfere with and control these processes. In recent studies, various protective agents, including antioxidants have been used on animal models, to inhibit the formation of free radicals thus improving hearing loss.In this review article we will discuss the role of traditional herbal medicine in treatment of noise/drug induced hearing loss, focusing on medicinal plants' active substances,as well as their mechanisms of action in reducing or preventing the formation of free radicals thus increasing the rate of survival of cochlea cells. Data have been gathered since year 2000, from scientific publications including the following keywords: deafness, drug toxicity, acute trauma, medicinal herbs and oxidative stress. The study includes all herbs and medicinal plants that have been experimentally used in studies on animal models and clinical trials. The results from these studies indicate the effectiveness of most of these herbs and their active substances through their antioxidative properties. Medicinal plants reported in this review can thus be considered as effective remedies intreating noise/drug induced hearing loss,yet further studies need to be done.

Impulse Noise Injury Model.

OBJECTIVES: The new Auditory 4.0 model has been developed for the assessment of auditory outcomes, expressed as temporary threshold shift (TTS) and permanent threshold shift (PTS), from exposures to impulse noise for unprotected ears, including the prediction of TTS recovery. METHODS: Auditory 4.0 is an empirical model, constructed from test data collected from chinchillas exposed to impulse noise in the laboratory. Injury outcomes are defined as TTS and PTS, and Auditory 4.0 provides the full range of TTS and PTS dose-response curves with the risk factor constructed from A-weighted sound exposure level. Human data from large weapons noise exposure was also used to guide the development of the recovery model. RESULTS: Guided by data, a 28-dBA shift was applied to the dose-response curves to account for the scaling from chinchillas to humans. Historical data from rifle noise tests were used to validate the dose-response curves. New chinchilla tests were performed to collect recovery data to construct the TTS recovery model. CONCLUSIONS: Auditory 4.0 is the only model known to date that provides the full TTS and PTS dose-response curves, including a TTS recovery model. The model shows good agreement with historical data.

[Occupational hearing loss--problem of health and safety].

On the basis of the literature review the critical analysis of the recommendations (the letter of Ministry of Health of Russia from 6/11/2012 N 14-1/10/2-3508) on occupation noise-induced hearing loss (HL) assessment is presented. Need of more strict criteria of HL assessment for workers, than for the general population according to ICF (WHO, 2001), in order to avoid growth of accidents and injury rate is proved. The illegitimacy of a deduction of statistical presbiacusia values from individual audiograms as human rights violation is stressed. Some terminological defects are noted. It is necessary to cancel recommendations and to develop the sanitary norms or state standard with the program of hearing conservation at work.

[On the discussion of the new aspects of the occupational hearing loss classification].

The objective of the present work was to analyse the materials of verification of the newly developed classification of occupational hearing loss harmonized with the international criteria an medico-social expertise of hearing impairment. The classification is designed for the practical application in the clinical work of otorhinolaryngologists, occupational pathologists, and medico-social experts who must practice the identical approaches at all stages of the preliminary and final diagnostics of occupational ear diseases, competence assurance, and social maintenance for the subjects presenting with hearing disorders. The authors emphasize the importance of taking account of presbyacusis characteristics at the stage of pre-nosological changes of the hearing function in the subjects exposed to strong occupational noise, i.e. prior to the appearance of the «signs of noise influence on the organs of hearing". Such an approach makes it possible to eliminate the discrepancies in drawing conclusion about the presence of presbyacusis or "signs of noise influence on the organs of hearing".

[The Königsteiner Empfehlung of 2012 - essential alterations and modifications]. / Die Königsteiner Empfehlung von 2012 - Wesentliche Neuerungen und Änderungen.

BACKGROUND: Since 1974, the recommendation for assessment of hearing impairment caused by noise - formerly known as "Königsteiner Merkblatt" (now: "Königsteiner Empfehlung") - has been representing the state of the art for the assessment of the occupational disease BK-No. 2301. It was updated several times, the last time in 2012. It provides a summary of the current medical knowledge. A new measurement for the entire working life - the Effective Noise Dose by Liedtke - was introduced. Otoacoustic emissions (OAE) are now the crucial tests in order to detect a hair cell dysfunction. As from now the tinnitus has to be put under a more comprehensive examination. On the strength of post experience the previous speech audiometry (Freiburger Test) is reliable, it was retrained. In future the indication for hearing aids will be oriented towards the aid guidelines of the legal health insurance. The questionnaire for the expert opinion was revised and the fee was adapted.

Classifying human audiometric phenotypes of age-related hearing loss from animal models.

Age-related hearing loss (presbyacusis) has a complex etiology. Results from animal models detailing the effects of specific cochlear injuries on audiometric profiles may be used to understand the mechanisms underlying hearing loss in older humans and predict cochlear pathologies associated with certain audiometric configurations ("audiometric phenotypes"). Patterns of hearing loss associated with cochlear pathology in animal models were used to define schematic boundaries of human audiograms. Pathologies included evidence for metabolic, sensory, and a mixed metabolic + sensory phenotype; an older normal phenotype without threshold elevation was also defined. Audiograms from a large sample of older adults were then searched by a human expert for "exemplars" (best examples) of these phenotypes, without knowledge of the human subject demographic information. Mean thresholds and slopes of higher frequency thresholds of the audiograms assigned to the four phenotypes were consistent with the predefined schematic boundaries and differed significantly from each other. Significant differences in age, gender, and noise exposure history provided external validity for the four phenotypes. Three supervised machine learning classifiers were then used to assess reliability of the exemplar training set to estimate the probability that newly obtained audiograms exhibited one of the four phenotypes. These procedures classified the exemplars with a high degree of accuracy; classifications of the remaining cases were consistent with the exemplars with respect to average thresholds and demographic information. These results suggest that animal models of age-related hearing loss can be used to predict human cochlear pathology by classifying audiograms into phenotypic classifications that reflect probable etiologies for hearing loss in older humans.

[Current aspects of harmonization of classification of occupational hearing loss].

The objective of the present work was to develop unified criteria for the evaluation of the severity of noise-induced hearing loss. Current approaches to taking expert decisions based on the results of medical examination of the patients with impaired hearing are substantially different due to the considerable difference between the criteria for the estimation of hearing envisaged by the international classification, occupational pathology classification, and the national system of medico-social expertise. We undertook an attempt to correct and harmonize the existing criteria for the estimation of severity of occupational hearing loss based on the integration of all the three classification in order to "reduce them to a common denominator" and thereby to ensure the basis for the unified diagnostic and expert decisions for the cases of hearing impairment of any etiology. The project proposed in this paper makes it possible to use unified criteria for the assessment of the degree of hearing loss caused by occupational noises for diagnostic purposes and expertise compatible with the internationally accepted approaches.

[Göttingen sentence in noise for different audiogram classes]. / Göttinger Satztest im Störgeräusch für verschiedene Gruppen von Schwerhörigkeit.

BACKGROUND: In addition to the standardized Freiburg sentence test in silence validated speech tests in noise are available. They are mainly used to test the benefit of hearing systems in everyday-life situations. In diagnostics tests in noise can also give additional information of the patients' hearing impairment. The determined speech reception threshold (SRT) depends on the degree of hearing loss and the used speech and noise test material. Aim of this study was to analyze the results of the Göttingen sentence test in noise in relation to different audiogram classes. MATERIAL AND METHODS: The Göttingen sentence test in stationary noise (65 dB) was performed for 135 patients with different degrees of hearing losses. Based on the air-conducted threshold all ears were categorized to an audiogram class by an automated procedure. RESULTS: For the mild hearing losses the results of the Göttingen sentence test increased with increasing pure-tone-average (PTA) and the values are smaller than 0 dB SNR with a small standard deviation (± 1-2 dB SNR). For the moderate hearing losses values of 5 dB SNR with a standard deviation of 6 dB SNR were achieved on average. Patients with a high hearing loss achieved values higher than 20 dB SNR. CONCLUSION: For the mild hearing losses the results were located in a small range. However, they can give important information about the patient's hearing impairment mainly appears in a noisy environment. With increasing hearing loss also the reduced hearing in silence affects the results achieved with the Göttingen sentence test in noise. Therefore the hearing in silence has to be taken into account at the interpretation of the results.

[Problematic medical expertise concerning simulation and aggravation in audiology]. / Zur Problematik der Simulation und Aggravation in der HNO-ärztlichen Begutachtung.

BACKGROUND: The effect of an incorrect audiological medical assessment of noise trauma deafness can be substantial. The impact will be demonstrated using a case example. The reasons for incorrect assessment are often insufficient examination conditions or simulation and aggression of the subject. The results of a study on this topic will be presented. PATIENTS AND METHODS: A total of 61 patients who underwent a psycho-acoustic medical assessment were grouped into 1 of 4 categories ranging from category 0 for no simulation or aggravation to category III for severe simulation and aggravation. For category III reliable and valid thresholds of pure tone audiometry can only be achieved using objective audiological measurements. The frequency, extent and socio-economic factors were evaluated. RESULTS: Of the 61 individuals 26 showed no simulation or aggravation behavior (category 0), 10% were grouped into category III and 48% into categories I and II. The tendency to simulation and aggravation increased with the patients' age, the level of education and the frequency of medical examinations prior to this investigation. CONCLUSIONS: Simulation and aggravation is a more frequent phenomenon than previously assumed (approximately 58% of all audiological examinations). The effect in terms of economical damage could be substantial. The usage of a well-defined classification is highly recommended in order to improve the quality of medical assessment in ENT.

[Acute hearing impairment by extremely high sound pressure levels]. / Akute Gehörschäden durch extrem hohe Schalldruckpegel.

The bulletin for occupational disease no. 2301 in the annex of the Occupational Disease Act, noise-induced hearing impairment, ("Merkblatt zu der Berufskrankheit Nr. 2301 der Anlage zur Berufskrankheiten-Verordnung: Lärmschwerhörigkeit") states that sound events with an intensity exceeding 137 dB (C) may cause immediate mechanical damage to the inner ear. Up to now a distinction has been made between prevention and actual damage potential for the risks caused by sounds with extremely high peak levels. In the field of prevention the unweighted sound pressure peak level of 140 dB, which is now 137 dB(C,peak) according to the LärmVibrationsArbSchV, was applied as the trigger threshold for measures; in contrast actual hearing impairment was not found until 150-160 dB. This article compiles the current state of knowledge and demonstrates that in the area of the reasons mentioned here for acute hearing impairment, no scientifically based new findings exist especially with reference to publications listed in the bulletin.

Notched audiograms and noise exposure history in older adults.

OBJECTIVE: Using data from a population-based cohort study, we compared four published algorithms for identifying notched audiograms and compared their resulting classifications with noise exposure history. DESIGN: Four algorithms: (1) , (2) , (3) , and (4) were used to identify notched audiograms. Audiometric evaluations were collected as a part of the 10-yr follow-up examinations of the Epidemiology of Hearing Loss Study, in Beaver Dam, WI (2003-2005, N = 2395). Detailed noise exposure histories were collected by interview at the baseline examination (1993-1995) and updated at subsequent visits. An extensive history of occupational noise exposure, participation in noisy hobbies, and firearm usage was used to evaluate consistency of the notch classifications with the history of noise exposure. RESULTS: The prevalence of notched audiograms varied greatly by definition (31.7, 25.9, 47.2, and 11.7% for methods 1, 2, 3, and 4, respectively). In this cohort, a history of noise exposure was common (56.2% for occupational noise, 71.7% for noisy hobbies, 13.4% for firearms, and 81.2% for any of these three sources). Among participants with a notched audiogram, almost one-third did not have a history of occupational noise exposure (31.4, 33.0, 32.5, and 28.1% for methods 1, 2, 3, and 4, respectively), and approximately 11% did not have a history of exposure to any of the three sources of noise (11.5, 13.6, 10.3, and 7.6%). Discordance was greater in women than in men. CONCLUSIONS: These results suggest that there is a poor agreement across existing algorithms for audiometric notches. In addition, notches can occur in the absence of a positive noise history. In the absence of an objective consensus definition of a notched audiogram and in light of the degree of discordance in women between noise history and notches by each of these algorithms, researchers should be cautious about classifying noise-induced hearing loss by notched audiograms.

Individual susceptibility to noise-induced hearing loss: choosing an optimal method of retrospective classification of workers into noise-susceptible and noise-resistant groups.

OBJECTIVES: Individual susceptibility to noise-induced hearing loss (NIHL) depends on the interaction between intrinsic and environmental factors. To proceed with the study on NIHL susceptibility genes an appropriate selection of workers susceptible and resistant to noise is crucial. The aim of the study was to compare four different methods of subject classification by the susceptibility to NIHL in a group of 949 workers of an electric power plant exposed to steady-state noise at the workplace. MATERIALS AND METHODS: One method based the classification of the workers on the international reference standard ISO 1999:1990; from the entire group of workers, 10% of the subjects with the worst hearing thresholds (HT) in the model were categorized as susceptible to NIHL, whereas 10% of the subjects with the best HT were categorized as resistant to noise. According to three other methods, the entire group of workers was first divided into subgroups by age, duration of employment and the level of noise, and then 10% of the subjects at each HT extreme were selected. RESULTS: The first classification allowed to achieve an excellent separation between HT of the susceptible and resistant subgroups. The susceptible subgroup was significantly younger than the resistant one, showed a shorter duration of employment and a lower level of noise exposure, which is in line with the definition of increased vulnerability to NIHL. The three other methods produced poorer separation of HT with smaller or no gap between HT values in subgroups. CONCLUSIONS: The selection of subjects from the entire worker population of a given industry based on the ISO 1999:1990 standard can be regarded as the most reliable method of classification of noise-susceptible and noise-resistant workers to be used in the future genetic studies on NIHL susceptibility genes.

[Occupational hearing loss: new principles of certification]. / Zawodowe uszkodzenie sluchu: nowe zasady orzecznicze.

Noise-induced hearing loss, together with presbyacusis, are the most prevalent causes of the functional impairment of the inner ear in an adult population. The authors discuss briefly the epidemiological, diagnostic and medical certification issues. The paper is focused on the new legislation that brings about considerable changes in the procedure of medical certification of noise-induced hearing loss. Both the definition of the pathology and new principles for its certification as an occupational disease were intended to harmonize Polish regulations with respective legislation of the EU countries.

Estudo das amplitudes das emissões otoacústicas em indivíduos expostos ao ruído de trios elétricos / Distortion product otoacoustic emission analyses after exposure to loud sound of \"truck bands\"

Os autores estudaram trinta indivíduos, adultos, portadores de audição normal, avaliada através da audiometria tonal, imitanciometria e análise de emissões otoacústicas produto de distorção. Foram estudados antes e depois da exposição sonora a trios elétricos por um período de quatro horas. Este estudo focalizou, especialmente, as frequências de 1,2,3,4e6 kHz.Todos os indivíduos submetidos a este procedimento tiveram as amplitudes das emissões otoacústicas diminuídas após a exposição ao som de alta intensidade, mostrando, assim, a alteração funcional da cóclea, os autores propõem a possibilidade de utilizar esse parâmetro como um indicativo para a prevenção da perda auditiva induzida pelo ruído