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Electrocochleography and gentamicin therapy for Ménière's disease: a preliminary report
J Adamonis1, S G Stanton, M Z Cashman
1Audiology Services, Sunnybrook and Women's College Health Sciences Centre, University of Toronto, Ontario, Canada.
Objective:
It is widely held that an enlarged summating potential (SP) relative to the eighth nerve action potential (AP) is a reflection of endolymphatic hydrops. Aminoglycosides are an accepted treatment for incapacitating Ménière's disease and are known to affect both sensory and secretory cells of the inner ear. The intent of this study was to determine whether this effect on secretory cells could be objectively confirmed by virtue of changes in the electrocochleogram (ECoG) of patients receiving gentamicin therapy for Ménière's disease.
Study Design:
This was a prospective longitudinal study of repeated ECoG measures in three groups of subjects. Ménière's patients undergoing gentamicin treatment were compared with two control groups: individuals with stable Ménière's disease and normal-hearing control subjects.
Setting:
The study was conducted at a tertiary referral center.
Patients:
The sample included 21 normal-hearing subjects, 15 patients with stable unilateral Ménière's disease, and 12 with disabling unilateral Ménière's disease.
Interventions:
For patients with disabling Ménière's disease, gentamicin was administered transtympanically. Audiograms, impedance tests, and ECoG were performed twice for all subjects.
Main Outcome Measures:
The SP and AP amplitudes, AP latency, and SP/AP ratio of the EcoG were measured.
Results:
A statistically significant reduction in the SP/AP ratio was observed after gentamicin administration (analysis of variance interaction effect: F2 = 5.64; p = 0.0065).
Conclusions:
The significant reduction in the SP/AP ratio in the gentamicin-treated Ménière's group supports the hypothesis that gentamicin improves the electrophysiologic function of the cochlea, possibly by reducing the severity of the associated endolymphatic hydrops.
Insights
Gentamicin treatment for Ménière's disease significantly reduced the summating potential/action potential (SP/AP) ratio, indicating improved cochlear electrophysiologic function. This supports gentamicin's potential to alleviate endolymphatic hydrops.
Area of Science:
- Oto-neurology
- Inner ear physiology
- Audiology
Background:
- Enlarged summating potential (SP) relative to action potential (AP) is linked to endolymphatic hydrops.
- Gentamicin is a standard treatment for Ménière's disease, affecting inner ear sensory and secretory cells.
Purpose of the Study:
- To objectively confirm gentamicin's effect on inner ear secretory cells.
- To assess changes in electrocochleogram (ECoG) in Ménière's patients receiving gentamicin therapy.
Main Methods:
- Prospective longitudinal study with repeated ECoG measures.
- Compared 12 Ménière's patients treated with transtympanic gentamicin to controls (15 stable Ménière's, 21 normal-hearing).
- Measured SP and AP amplitudes, AP latency, and SP/AP ratio.
Main Results:
- A statistically significant reduction in the SP/AP ratio was observed post-gentamicin treatment (p = 0.0065).
- This ECoG change suggests an improvement in cochlear function.
Conclusions:
- The observed SP/AP ratio reduction supports gentamicin's therapeutic effect in Ménière's disease.
- Gentamicin may improve electrophysiologic function by reducing endolymphatic hydrops severity.