Long-term follow-up after gentamicin application via the Silverstein MicroWick in the treatment of Meniere's disease

Ear, Nose & Throat Journal,  August, 2006  by Samuel L. Hill, III,  Nicholas B. Digges,  Herbert Silverstein

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Abstract

We conducted a retrospective study to evaluate the long-term effectiveness of gentamicin applied directly to the round window membrane via the Silverstein MicroWick system in patients with definite or probable Meniere's disease. The study population was made up of 69 patients who had received 3 drops of gentamicin 10 mg/ml three times daily; the duration of treatment was guided by objective data obtained from weekly electronystagmography and audiometry. Relief of vertigo was assessed by chart review and telephone interviews. After a minimum follow-up of 24 months, we found that vertiginous symptoms remained controlled in 53 patients (76.8%) after one or more courses of drug therapy. A single course of treatment was successful in 41 patients (59.4%). We conclude that long-term control of vertigo can be achieved in patients with Meniere's disease by direct application of gentamicin to the round window membrane via the Silverstein MicroWick. This minimally invasive sell-treatment technique was well tolerated and free of long-term complications.

Introduction

Schuknecht originally described middle ear perfusion with an aminoglycoside antibiotic for the treatment of Meniere's disease in 1956. (1) Afterward, the popularity of transtympanic methods of treating inner ear disease grew rapidly. Transtympanic treatment of Meniere's disease has several advantages: (1) it is easy to perform, (2) the surgeon can treat the affected ear directly, (3) drug can be delivered to the site of action in higher concentrations, (4) the side effects of systemic drug therapy are avoided, and (5) these procedures are much less invasive than the traditional surgical treatments for Meniere's disease. (2) Transtympanic gentamicin is a widely used and effective treatment for vertigo in patients with Meniere's disease. (3-6)

Several methods of delivering gentamicin to the inner ear have been described in the literature, and no consensus has been reached as to which is the most effective. These methods include transtympanic injections, application of gentamicin and Gelfoam to the round window membrane, continuous perfusion through the Round Window Microcatheter (Durect Corp.; Cupertino, Calif.), and transtympanic perfusion via the Silverstein MicroWick system (Micromedics; Eaton, Minn.). (7-9)

Two types of transtympanic gentamicin dosing schedules have been described in the literature: fixed dosing and titration. The titration method relies on objective measures obtained by electronystagmography (ENG) and audiometry to guide therapy. Toth and Parnes compared the two methods and found that while they were equally effective, the titration method resulted in significantly less hearing loss. (10)

The Silverstein MicroWick system has been shown to be highly successful in controlling vertigo in patients with Meniere's disease. In 2002, our group reported the outcomes of 92 patients who had been treated with 3 drops of gentamicin 10 mg/ml three times daily. (2) The Silverstein MicroWick system delivers gentamicin in a titrated fashion, and therefore treatment was guided by weekly ENG and audiometry results; the treatment goal was to elicit a 100% reduced vestibular response (RVR) to ice air on caloric testing. Of patients who responded to a questionnaire, 85% experienced relief of vertigo, 67% experienced alleviation of aural pressure, and 57% experienced relief of tinnitus. The overall incidence of hearing loss was 36%. These results are essentially the same as those reported by others. (11-13) In another study, we attempted to elucidate the relationship between the level of vestibular ablation, the subsequent control of vertigo, and the risk of hearing loss with the MicroWick system. (5) We did find an association among these variables, and we also suggested that it might not be necessary to elicit a 100% RVR in order to achieve or maintain vertigo control. In that study, the overall vertigo control rate was 82%, the vertigo persistence rate was 9%, and the vertigo recurrence rate was 9%. All recurrent episodes occurred within 1 year.

Until now, no data have been published on long-term outcomes following the direct application of gentamicin to the round window membrane via the Silverstein MicroWick system in patients with Meniere's disease. The objective of this article is to report our evaluation of the MicroWick after a minimum of 24 months' follow-up in terms of vertigo control, the need for repeat treatments, the management of treatment failures, and overall patient satisfaction. The current study is a follow-up to our two earlier studies. (2,5)

Patients and methods

We retrospectively reviewed the records of 92 patients with Meniere's disease who had been treated at a private otology/neurotology practice with gentamicin inner ear perfusion via the Silverstein MicroWick system. Patients had received 3 drops of gentamicin 10 mg/ml three times daily; the duration of titrated treatment was guided by objective data obtained from weekly ENG and audiometry, with a targeted endpoint of a 100% RVR on ice air. Specific procedural aspects of the initial treatment regimen have been described in detail elsewhere. (2,5) In addition to patients' charts, telephone calls were also used to obtain data.