Abstract Objective: The present study aimed to perform a morphological and morphometric analysis of cochlear structures of C57BL/6J mice receiving oral melatonin for a 12-month period. Methods: 32 male C57BL/6J were divided into control and melatonin groups. Control received saline and ethanol solution and melatonin group, 50 μL of 10 mg of melatonin/kg/day orally for a 12-month period. After de experiment the animals were sacrificed into a 40% concentration of CO2 chamber, and the blades were morphological and morphometrically analyzed. Results: The melatonin group revealed a higher median density of viable cells (45 ± 10.28 cells/100 μm2, 31–73, vs. 32 ± 7.47 cells/100 μm2, 25–48). The median area of stria vascularis was 55.0 ± 12.27 cells/100 μm2 (38–80) in the control, and 59.0 ± 16.13 cells/100 μm2 (40–134) in the melatonin group. The morphometric analysis of the spiral ligament reveals a higher median of total viable neurons in the melatonin (41 ± 7.47 cells/100 μm2, 27–60) than in the control group (31 ± 5.68 cells/100 μm2, 21–44). Conclusion: Although melatonin is a potent antioxidant, it does not completely neutralize the occurrence of presbycusis; however, it may delay the onset of this condition. Level of evidence: 3.

Abstract Introduction The excessive noise observed in the school environment can cause damages or losses to the learning process as well as risks to the health of teachers and students, such as physical, mental and social impairments, including, among them, hearing loss. Objective To assess otoacoustic emissions in teachers and determine whether classroom noise reduces distortion-product otoacoustic emissions (DPOAEs) amplitude and signal-to-noise ratio (SNR). Method Sixty-seven teachers were evaluated using otoacoustic emissions testing in two situations: after hearing rest and after the working day. Results Signal amplitude (p = 0.044 [2 kHz]; p = 0.01 [4 kHz]) and SNR for frequencies of 2 kHz (p = 0.008) and 4 kHz (p = 0.001) decreased significantly between time points. Mean classroom noise was associated with the magnitude of the difference in signal amplitude at 2 kHz (p = 0.017) and 4 kHz (p = 0.015), and SNR at 4 kHz (p = 0.023). Conclusions There was a decrease in the amplitude and in the SNR after exposure to the noise in the classroom environment. The high levels of sound pressure that teachers are exposed to on a daily basis can cause a temporary change in the outer hair cells of the Corti organ, and these changes may become permanent over time.

RESUMO Objetivo: descrever o perfil audiológico de profissionais disc jockeys atuantes em cidades do Distrito Federal. Métodos: foram realizados os exames de audiometria, timpanometria, emissões evocadas por estímulo transiente e emissões evocadas - produto de distorção, e entrevista para identificar sintomas auditivos. Foram aplicados os testes estatísticos pertinentes adotando o nível de significância menor que 0,05. Resultados: foram avaliados 21 disc jockeys com faixa etária entre 20 e 45 anos. As queixas auditivas mais citadas foram sensação de plenitude auricular (86%) e zumbido (57%). Os limiares auditivos mantiveram-se predominantemente dentro da normalidade (90%), mas houve aumento dos limiares nas frequências de 3.000 a 6.000 Hz (38%). Apenas 42% da amostra apresentaram resposta “passa” nas emissões evocadas por estímulo transiente e 81% nas emissões evocadas - produto de distorção em ambas as orelhas. Conclusão: a pesquisa identificou limiares auditivos predominantemente dentro dos padrões de normalidade, entretanto com aumento das frequências altas, que podem estar associadas à exposição ao ruído. As emissões otoacústicas apresentaram alterações tanto nas transientes quanto nas por produto de distorção.

ABSTRACT Purpose: to describe the audiological profile of professional disc jockeys acting in cities of the Brazilian Federal District. Methods: audiometry, tympanometry, transient evoked emissions, and distortion product evoked emissions exams were conducted, as well as interviews, in order to identify auditory symptoms. Appropriate statistical tests were applied, adopting a significance level lower than 0.05. Results: a total of 21 disc jockeys, aged between 20 and 45 years, were evaluated. The most cited auditory complaints were feeling of ear fullness (86%) and tinnitus (57%). Auditory thresholds remained predominantly within normal range (90%), but thresholds were increased in frequencies from 3 KHz to 6 KHz (38%). Only 42% of the sample presented a pass response in transient evoked emissions, and 81% in distortion product evoked emissions, in both ears. Conclusion: the research identified auditory thresholds predominantly within standards of normality, though with increased high frequencies, that may be associated with noise exposure. The otoacoustic emissions presented alterations both in the transient ones and in the distortion product.

<sec><title>Introduction</title><p> Analysis of the suppression effect is a simple method to evaluate cochlear status and central auditory mechanisms and, more specifically, the medial olivocochlear system. This structure may be involved in the generation of mechanisms that cause tinnitus and in the pathophysiology of tinnitus in patients with tinnitus and normal hearing.</p></sec><sec><title>Objective</title><p> To review the literature of the etiology of tinnitus on the lights of otoacoustic emissions in patients with normal hearing.</p></sec><sec><title>Data Synthesis</title><p> Individuals with tinnitus and normal hearing have a higher prevalence of alterations in transient-evoked otoacoustic emissions and distortion-product otoacoustic emissions than normal subjects. This fact suggests that dysfunctions of the outer hair cells (OHCs) might be important in the generation of the tinnitus; however, this feature is not always present in those who have the symptoms of tinnitus.</p></sec><sec><title>Final Comments</title><p> These findings suggest that OHC dysfunction is not necessary for tinnitus development—that is, there might be mechanisms other than OHC damage in the tinnitus development. On the other hand, OHC dysfunction alone is not sufficient to cause the symptom, because a great many individuals with OHC dysfunction did not complain about tinnitus.</p></sec>