| Summary: | 博士 === 國立臺灣大學 === 職業醫學與工業衛生研究所 === 94 === Hearing loss from occupational and environmental noise exposures remains the most significant causes of acquired sensorineural hearing loss in the world. The majority of global disease burden from hearing loss is attributed to occupational and environmental noise worldwide.
As recent medico-technological advancements of audiological battery in the objectively hearing assessment, such as otoacoustic emission, auditory steady state evoked potential, we could identify more objectively the hearing threshold level of workers, who suffered from hearing impairment. On the other hand, occupational clinician and otolaryngologist could also take this advantage to differentiate those workers who intended to malinger for occupational compensation or medico-legal issues. Moreover, although the 4k Hz dip was well known as the clinical sign of audiometry for noise-induced hearing loss and 85 dBA was well accepted for recommended permission exposure level in modern industry, we further investigate the major determinants of risk factors on high frequency notch audiogram among male gasoline distribution workers in Taiwan.
With new understanding of mechanistic insights in noise-induced hearing loss from animal laboratory, we can identify the safe and effective interventions that provide scientific rationale to eliminate this most important cause of acquired hearing loss. Such as the role of gap junction protein, connexin 26, in the lateral wall of cochlea, this has been proved to be related to congenital and hereditary deafness. Moreover, a new electrophysiological tool, vestibular evoked myogenic potential, was applied in animal model of noise-induced hearing loss to assess objectively the permanent and temporary damages of vestibular system in inner ear after acoustic trauma.
Here we present an update review and propose new tools to identify noise-induced hearing loss in epidemiological aspects from human workplaces exposure of male gasoline distribution workers in a petrochemical company in Taiwan. Besides, the pathophysiology of acute acoustic injury to inner ear, both cochlear and vestibular systems, was investigated by electrophysiological instruments and molecular biological techniques in animal experimental models, then applied to human subjects with acute acoustic trauma.
There were five domain parts included in this thesis:
Part I: Environmental perspective - Prevalence and determinants of high frequency audiometric notch in male gasoline distribution workers.
Part II: Occupational perspective - Objective assessment of auditory thresholds in noise-induced hearing loss using steady-state evoked potentials.
Part III: Molecular biological perspective - Expression of connexin 26 in the lateral wall of rat cochlea after acoustic trauma.
Part IV: Electrophysiological perspective - Temporary and permanent loss of vestibular evoked myogenic potentials after acute acoustic trauma in guinea pigs.
Part V: Clinical perspective - Vestibular evoked myogenic potentials in acute acoustic trauma
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