Results of electrocochleography in Ménière's disease after successful vertigo control by single intratympanic gentamicin injection.

In the last several years, a promising new approach has been suggested in the therapy of Ménière's disease (MD): the low-dose intratympanic gentamicin therapy. By titrating the desired vestibular inhibition by single injections and infrequent administration, side effects concerning hearing can be held on an acceptably low level, while disease-related symptoms are often successfully eliminated. However, it is still unclear if endolymphatic hydrops actually decreases when the patients become symptom free. In the literature, hydrops is significantly associated with an enhanced ratio of summating potential/action potential (SP/AP). Our aim in this retrospective study was to answer the question if pathologically high SP/AP ratios normalize after successful low-dose intratympanic gentamicin treatment. Twenty-eight patients with MD received one, two or three intratympanic gentamicin injections. These injections inhibited vertigo spells without causing additional hearing loss. SP/AP ratios measured by noninvasive electrocochleography did not improve statistically when patients became symptom free. This indicates that the beneficial effect of gentamicin does not depend on the improvement of SP/AP ratios. Considering the well-established correlation between increased SP/AP and active MD, it thus seems unlikely that gentamicin treatment significantly reduces hydrops.