The aim of this study is to analyze the effects of intratympanic gentamicin injections on vestibular function in 33 patients with unilateral Meniere's Disease (according to AAO-HNS guidelines 1995) that had been unresponsive to medical therapy for at least one year. In such patients, the results of bedside examination of vestibular function vestibular examination is compared to those from laboratory tests. Intratympanic gentamicin injections (27 mg/ml) were performed at weekly intervals until symptoms or signs of vestibular hypofunction developed in the treated ear. Vestibular function was evaluated in two different rotatory chair tests. The parameters that were specifically considered were the time constant of the vestibulo-ocular reflex (VOR) after impulse rotation with a peak chair velocity of 100°s-1, and the phase and gain of the VOR after the sinusoidal harmonic acceleration (SHA) test with a peak chair velocity of 50°s-1. After treatment, both the time constant of the VOR after rotation towards the treated side and the gain in the SHA test were significantly reduced. These reductions were in accordance with the number of additional signs observed upon bedside examination at the end of the treatment. The changes observed in the VOR correlate well with the results of bedside examination of vestibular function, which in turn reflects the damage induced by intratympanic gentamicin injection.
