VESTIBULAR DYSFUNCTION IN NOISE-INDUCED HEARING-LOSS

It is known that loud tones can damage the cochlea, but vestibular involvement has been given less attention. However, patients with noise induced hearing loss (NIHL) sometimes have balance disorders as well and some have symptoms resembling those of Meniere's disease. In this study, we examined the relationship between loud sounds and vestibular problems. Thirty-six NIHL patients were divided into two groups according to the presence (vertigo group) or absence (non-vertigo group) of vestibular complaints. Electrocochleograms were recorded from all subjects after pure tone audiometry. A higher incidence of increased -summating potential (SP)/action potential (AP) ratio was observed in the vertigo group than in the non-vertigo group. Caloric tests were performed in the vertigo group, and a reduced response was observed in 47.1% of ears. It is generally considered that the -SP/AP ratio is a useful indicator of endolymphatic hydrops. Therefore, episodic vertigo in NIHL patients may result from a pathophysiological mechanism similar to that of Meniere's disease,