[Prevention and management of acoustic traumas]. / Prévention et prise en charge des traumatismes sonores.

Exposure to intense noises during a short time can be responsible for permanent damage of the inner ear, even after an isolated exposure. Amplified music (discos, concert rooms) is the first cause of acute acoustic traumas among the young people. Acute acoustic traumas need urgent management and treatment. Exposure to high noise levels during a long time can lead to a progressive and insidious impairment of the inner ear, the hearing loss appearing obvious only after several months or years. Noise-induced hearing loss is irreversible. The functional consequences of acoustic traumas can be socially disabling and can have an important psychological impact. The prevention is based on the information of the patients, notably of the youngest ones, and on the wearing of hearing protectors at the time of risky situations.

Otoacoustic emissions and persistent tinnitus after acute acoustic trauma.

OBJECTIVES: To follow up the auditory status of military personnel after an acute acoustic trauma and to identify the possible predictive value of hearing thresholds and otoacoustic emissions during the first 24 hours after the acoustic trauma. STUDY DESIGN: A group of 24 young military subjects, aged 22 +/- 2.3 years, without any otologic problem before the acoustic trauma, were examined at three time intervals after an accidental acoustic trauma caused by the discharge of a firearm: 24 hours, 72 hours, and 15 days. METHODS: Each subject was submitted to medical examination and to a questionnaire detailing the circumstances of the acoustic trauma. Pure tone audiometry was performed from 1 to 8 kHz per half octave. Transiently evoked otoacoustic emissions were recorded in the nonlinear mode at 80 dB pSPL, and distortion product otoacoustic emissions were recorded from 1 to 6 kHz, using a distortion product-gram type procedure, at 65/55 dB SPL, with f2/f1 = 1.22. Two groups of subjects were defined: group 1 (n = 8) represented subjects with short-lasting tinnitus (<72 h) and group 2 (n = 16) subjects with long-lasting tinnitus (>72 h). RESULTS: Hearing thresholds did not differ significantly between these two groups 24 hours after the acoustic trauma. However, otoacoustic emissions showed significantly lower amplitudes 24 hours after the acoustic trauma in subjects showing a longer lasting tinnitus. CONCLUSION: Otoacoustic emissions appear to be a better predictor of the persistence of tinnitus than hearing thresholds alone 24 hours after an acute acoustic trauma.

Moderate variations of mood/emotional states related to alterations in cochlear otoacoustic emissions and tinnitus onset in young normal hearing subjects exposed to gun impulse noise.

This study was designed to test whether under impulse noise exposure mood and emotional states could play a role in the onset of tinnitus and/or could modify cochlear sensitivity objectively measured with distortion product otoacoustic emissions (DPOAEs). The experimental design consisted in a short follow-up study of 54 young military subjects (20+/-2 years old), psychologically normal, with normal hearing, during two consecutive days of target practice rounds. Data collection included an abbreviated version of the profile of mood states (POMSs) inventory [Profile of Mood States, Educational and Industrial Testing Service, San Diego, 1971], questionnaires on tinnitus perception (previous history and after shooting) and DPOAEs measurements before and after shooting. Higher scores of tension-anxiety were found in subjects having previous history of tinnitus. Association between tinnitus previous history and tinnitus after shooting was found significant. Perception of tinnitus after target practice rounds was associated with significantly lower DPOAEs at 3 kHz. The most tense-anxious subjects were found to have DPOAEs decreases of 3.35+/-6 dB at 3 kHz after shooting. This study clearly shows that, in young healthy population, psychologically normal and with normal hearing, moderate variations in mood and emotional states were related to tinnitus onset and DPOAEs alterations. It is possible that stronger variations in mood and/or emotional condition would increase risks of tinnitus and alterations of cochlear sensitivity.

DPOAEs in young normal-hearing subjects with histories of otitis media: evidence of sub-clinical impairments.

To investigate the origin of the susceptibility to noise in subjects with histories of otitis media (OM), we assessed early sub-clinical impairments in normally hearing subjects with a history of OM using distortion product otoacoustic emissions (DPOAEs). DPOAEs of 213 normal-hearing subjects aged 18-24 years were obtained and comparisons of DPOAE levels in several groups as a function of OM past infections were tested by ANOVA. A main finding was that young normal-hearing subjects with a history of OM had significantly lower DPOAEs over all octaves tested compared to normal-hearing subjects without antecedent of OM. The mean difference was 3.5+/-1.1 dB in the 2-4 kHz zone, which was especially marked in subjects (n=21) that had undergone a myringotomy (6.6+/-1.5 dB) in the 4 kHz zone. The level of impairment seemed to depend on the severity of the past infection as characterised by the importance and the duration of the infectious effusions.