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Updated: Feb 2, 2026
A Revised Surgical Approach to Induce Endolymphatic Hydrops in the Guinea Pig
Published on: June 4, 2020
Gentamicin delivery to the inner ear: Does endolymphatic hydrops matter?
Pedro Marques1,2, Maoli Duan3,4, Nicolas Perez-Fernandez5
1Department of Otorhinolaryngology, S.João Hospital Centre, Porto, Portugal.
Introduction:
Middle ear application of gentamicin is a common medical treatment for uncontrolled Ménière's disease. The objective of the study was to evaluate the impact of endolymphatic hydrops on inner ear delivery.
Methods:
Perilymph gentamicin concentrations and correlation with endolymphatic hydrops in an animal model were assessed. A group of 24 guinea pigs was submitted to surgical obstruction of the endolymphatic sac and duct of the right ear. Gentamicin was applied either to the right ear's round window niche or through a transtympanic injection. Perilymph specimens were collected at different times. Histologic morphometry was used to evaluate both turn-specific and overall hydrops degree.
Results:
In animals with endolymphatic hydrops, lower concentrations of gentamicin were observed after 20 or 120 minutes of exposure and in both types of administration, when compared to controls. This difference reached statistical significance in the round window niche application group (Mann-Whitney, p = 0,007). A negative correlation between perilymphatic gentamicin concentration and hydrops degree could be observed in both groups, after 120 minutes of exposure (Spearman correlation, round window niche p<0,001; TT p = 0,005).
Conclusions:
The study indicates that the endolymphatic hydrops degree has a negative interference on the delivery of gentamicin into the inner ear following middle ear application.
Insights
Endolymphatic hydrops negatively impacts gentamicin delivery to the inner ear via middle ear application. This finding is crucial for optimizing Ménière
Area of Science:
- Ototoxicology
- Inner Ear Physiology
- Pharmacokinetics
Background:
- Middle ear gentamicin application is a standard treatment for Ménière's disease.
- Endolymphatic hydrops is a characteristic feature of Ménière's disease.
- The efficacy of gentamicin delivery may be influenced by inner ear conditions.
Purpose of the Study:
- To investigate the effect of endolymphatic hydrops on gentamicin concentration in the inner ear.
- To assess the correlation between the degree of endolymphatic hydrops and perilymph gentamicin levels.
Main Methods:
- An animal model of endolymphatic hydrops was created in guinea pigs.
- Gentamicin was administered via round window niche or transtympanic injection.
- Perilymph gentamicin concentrations and hydrops severity were measured.
Main Results:
- Animals with endolymphatic hydrops showed significantly lower perilymph gentamicin concentrations.
- A negative correlation was found between hydrops severity and gentamicin levels.
- This effect was observed for both administration routes.
Conclusions:
- Endolymphatic hydrops impairs gentamicin's inner ear penetration.
- Treatment strategies for Ménière's disease may need to account for hydrops-related delivery changes.
- Further research is needed to optimize gentamicin delivery in Ménière's disease.
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