Hearing loss following intratympanic instillation of gentamicin for the treatment of unilateral Meniere's disease

Objective: To determine the incidence, extent, and time course of hearing loss following instillation of intratympanic gentamicin using a predetermined fixed protocol for incapacitating unilateral Meniere's disease and to determine whether such loss is associated with any identifiable risk factors. Study Design: A retrospective analysis of all patients treated with intratympanic gentamicin between 1988 and 1998 using American Academy of Otolaryngology-Head and Neck Surgery reporting guidelines (1985 and 1995). A predetermined regimen using a fixed dose (gentamicin 26.7 mg/mL administered three times daily for 4 consecutive days) was used. Methods: The records of patients treated with this particular protocol were reviewed. The relationship between pretreatment hearing acuity, pretreatment bithermal caloric response, duration of symptoms, and previous treatment to post-treatment hearing were analyzed with respect to hearing. Results: Complete vestibular and audiologic data over a minimum 2-year follow-up were available for 85 individuals. Sixty-three patients (74.1%) had unchanged or improved hearing, and 22 patients (25.9%) realized hearing loss. In 80% of the latter, it occurred during the first month post-treatment. When hearing acuity at the 1-month post-treatment interval remained unchanged (91.1%), it was likely to remain so over the next 23 months. A significantly higher incidence of profound hearing loss was noted in patients who developed hearing loss in the first month, as compared with those who developed hearing loss at a later period (p = .0207, relative risk = 1.5). Re-treatment was not associated with hearing loss. The only identifiable risk factor for developing hearing loss was pretreatment hearing acuity stages 3 and 4 (pure-tone average > 40 dB) (p = .022, relative risk = 1.5). Conclusion: Hearing loss is a recognized complication of treatment with intratympanic gentamicin, occurring in approximately 26% of individuals. In those individuals in whom hearing acuity has remained unchanged after the first month interval, significant worsening of hearing is unlikely, and patients can be reassured accordingly.