A Clinical Study of the Progression to Bilateral Meniere's Disease from Unilateral Meniere's Disease: from the Viewpoint of the Indication of Intratympanic Gentamicin Injection Therapy

Intratympanic gentamicin injection has been used as a treatment of intractable Meniere's disease (MD). Although this therapy is supposed to be applied to unilateral MD, it should be noted that unilateral MD progresses to bilateral MD at a rate of 10-40%. Involvement of the contralateral ear after gentamicin injection could cause the serious problem of bilateral inner ear disfunction. To predict the future involvement of the contralateral ear, we reported a prospective study of patients that were diagnosed with unilateral MD at the first examination. Among 71 patients with unilateral MD, 9 (12.6%) showed fluctuating hearing loss in the contralateral ear. The average interval of the contralateral involvement after the unilateral involvement was 8.7 years. Although the prediction of the contralateral involvement was difficult from the results of the pure tone audiometry, caloric test and vestibular evoked myogenic potential, these bilateral cases tended to be seen more in females and in patients of older ages at the onset of the disease. The results of this study revealed that there is a possibility of contralateral involvement for more than 10 years, and the incidence of bilateral involvement is high in female patients who were over 60 at the onset of the disease.