Efficacy of increased gentamicin concentration for intratympanic injection therapy in Meniere's disease

Objectives: Update of ongoing case series of intratympanic gentamicin use in intractable Meniere's disease. Comparison of the treatment results of two gentamicin concentrations: 30 mg/ml and 40 mg/ml. Study Design: Retrospective case-matched review of an ongoing protocol. Setting: Ambulatory visits in an office setting. Patients: Eighty-seven patients were included in this study according to the 1995 guidelines of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) for reporting treatment results of Meniere's disease. Intervention: Intratympanic injection of a buffered gentamicin solution (30 mg/ml) was used in 44 patients (Group 1) in years 1992 to 1995. Stock gentamicin solution (40 mg/ml) was used in 43 patients (Group 2) in years 1996 to 1999. Treatment was titrated for each patient. and the hearing was strictly monitored. The endpoint of treatment was the complete cessation of vertigo spells. Main Outcome Measures: Hearing results, vertigo control scores. and ice water caloric testing responses were analyzed after 24 months of follow-up. Thirty-two patients from each group were selected for case-matched statistical analysis. Results: Four or fewer gentamicin injections were used in 70% of Group 1 patients and 96% of Group 2 patients, In Group 1, vertigo control was achieved in 81% of patients, and the hearing remained the same or was improved in 68% of patients. In Group 2. vertigo control was achieved in 72% of patients, and the hearing remained the same or was improved in 81% of patients. Treatment was aborted in four patients of Group 2 for early reversible hearing loss, and 31 of 39 patients (79%) who completed the protocol experienced lasting vertigo control. There was a trend for longer-lasting vertigo control in the Group 2 patients. Conclusion: It was concluded that increasing the gentamicin concentration to 40 mg/ml probably produces similar rates of vertigo control as those of the lower dose, at least initially, but requires fever injections, The higher dose did not increase the risk of hearing loss if treatment was stopped at the first indication of injury. A larger study is needed to confirm the trend of improved long-term hearing results in patients treated with the 40 mg/ml solution.