The effects of noise on the vestibular system

PURPOSE: Subjects with noise-induced hearing loss sometimes also complain about balance disorders, but reports of clinical series that give contradictory results are highly controversial. This study was designed to evaluate the effects of intense noise on the vestibular labyrinth, both in subjects with symmetrical hearing loss and in subjects with asymmetrical loss, and to examine the correlation between the subjects' complaints and the results of the vestibular function tests. METHODS: A total of 258 male military personnel, heavily exposed to various intense noises, were included in the study. They were divided into 2 groups according to their hearing; 134 had a symmetrical high-tone hearing loss, and 124 had asymmetrical losses. Each group was divided into 2 subgroups according to the presence or absence of vestibular complaints. All of the subjects underwent a complete audiological and electronystagmographic evaluation. RESULTS: We found that vestibular damage caused by intense noise exposure might be expressed clinically in subjects with asymmetrical hearing loss. There was a strong correlation between the subjects' complaints and the results of the vestibular function tests. There was no correlation between the severity of the hearing loss and the vestibular symptomatology and pathology. CONCLUSIONS: Subjects exposed to intense noise may have evidence of vestibular pathology only when there is an asymmetrical hearing loss. Whenever hearing loss is symmetrical, an equal damage to the vestibular system of both ears is most probably responsible for the absence of abnormal findings on the vestibular function tests. The results of this study have important medicolegal implications for individuals exposed to intense noises.