Changes in clinical and instrumental vestibular parameters following acute exposition to auditory stress.

Besides Tullio's phenomenon, resulting from anatomic changes in the labyrinth, a hypersensitivity to acoustic stimuli of the saccular structures appears to be the underlying cause of the vestibular responses detected in some patients. In order to evaluate the incidence of vestibular symptoms triggered by acute exposure to auditory stress (disco music), 40 subjects aged between 18 and 26 years, with no audiological and vestibular disorders, were submitted to otoneurologic tests. Subjects were exposed to disco music [intensity 128 dB (C)], for 3 hours. Tests have been carried out before and immediately after exposure. Canalar and macular functions have been evaluated using vestibular investigation techniques and vestibular evoked myogenic potentials. When compared to baseline data, post-exposure test results did not reveal any canalar damage. Pre- and post-exposure recordings of the vestibular-oculomotor reflex threshold have shown no significant changes. Conversely, post-stimulus recordings have shown a significant increase in the amplitude of the vestibular evoked myogenic potential response, thus indicating a possible irritative involvement of the macular receptor. This result suggests a direct action upon the receptor by acoustic stimulation which could, therefore, be the underlying cause of vestibular symptoms reported by patients following exposure to sufficiently intense acoustic stimuli. Prior to this study. a questionnaire concerning the relationship between habitual disco visiting and audio-vestibular symptoms has been completed by 310 students at the University of Catanzaro. This survey revealed a significant incidence of vestibular symptoms due to acoustic stress (Tullio's phenomenon) which led us to hypothesise that balance disorders due to auditory stress are much more frequent than commonly held, particularly since, in many cases, diagnoses is unknown or not easy due to the difficult procedures by which these conditions are diagnosed.