[27 years experiences with transtympanic aminoglycoside treatment of Menière's disease]

Intratympanic (IT) Therapies for Menière's Disease: Some Consensus Among the Confusion

Purpose of Review

Aminoglycosides and corticosteroids are commonly used to treat Menière's disease. Intratympanic (IT) administration of these medications allows high inner ear concentrations without significant adverse systemic effects. As a direct result, IT therapy has grown in popularity. Recent studies have compared patient outcomes between IT aminoglycosides and corticosteroids. This review summarizes these findings.

Recent Findings

Trials comparing IT corticosteroids to IT placebo or oral therapy have had conflicting results. Most recently, Lambert et al. investigated the effect of IT dexamethasone in a sustained-release formulation compared to placebo. Their findings demonstrated improvement in some secondary measures of vertigo with the sustained-release formulation.IT gentamicin is known to be effective in controlling vertigo in Menière's disease. In a recent study from 2016, Patel et al compared IT gentamicin and IT methylprednisolone in a double-blind, randomized controlled trial and identified no significant differences between the two in vertigo control.

Summary

IT injections of aminoglycosides and corticosteroids can improve vertigo control. Hearing and vestibular loss however may result with IT aminoglycosides. Corticosteroids demonstrate limited hearing loss but may not have the same efficacy in controlling vertigo. Further investigation in the etiology of Menière's disease is needed to tailor the proposed treatment to suit the disease mechanism.

Visualization and analysis of superparamagnetic iron oxide nanoparticles in the inner ear by light microscopy and energy filtered TEM

Nanoparticles as potential carriers for local drug transfer are an alternative to systemic drug delivery into the inner ear. We report on the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic(®) F127 (PF127) copolymer. Pluronic copolymers possess a unique viscosity-adjustable property that makes PF127 gels easy to handle compared to conventional cross-linked hydrogels. This ferrogel was successfully tested in cadaver human temporal bones as well as in organotypic explant cultures of mouse inner ears. SPIONs were identified by light microscopy and localized with different imaging modes in energy-filtered transmission electron microscopy. Our approach shows a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels.

FROM THE CLINICAL EDITOR

The authors report the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic® F127 (PF127) copolymer for drug delivery in the inner ear, demonstrasting a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels.

Meniere's disease in the elderly

Menière disease usually begins in adults from 20 to 60 years old, and occurs in more than 10% of patients older than 65. The treatment of Menière disease in the elderly represents a challenge because of polymedication. Antivertiginous drugs such as betahistine and cinnarizin give good results with minor secondary effects. In contrast, major vestibular suppressor drugs such as thiethylperazin must be avoided as long-term treatment because of their side effects. Definitive vestibular surgical deafferentations such as labyrinthectomy and selective vestibular neurectomy represent optional procedures but must be carefully evaluated from case to case. Ablative procedures remain the efficient treatment of drop attacks, which represent a high potential risk of severe injuries by older patients sometimes with important social consequences.

Dependence of hearing changes on the dose of intratympanically applied gentamicin: a meta-analysis using mathematical simulations of clinical drug delivery protocols

OBJECTIVES/HYPOTHESIS

To establish safe dosing protocols for the treatment of patients with Meniere's disease with intratympanic gentamicin.

STUDY DESIGN

A validated computer model of gentamicin dispersion in the inner ear fluids was used to calculate cochlear drug levels resulting from specific clinical delivery protocols. Dosing in the cochlea was compared with changes of hearing sensitivity for 568 patients reported in 19 publications.

METHODS

Cochlear drug levels were calculated based on the concentration and volume of gentamicin applied, the time the drug remained in the middle ear, and on the specific timing of injections. Time courses were quantified in terms of the maximum concentration (Cmax) and the area under the curve of the drug at specific cochlear locations.

RESULTS

Drug levels resulting from single, "one-shot" injections were typically lower than those from repeated or continuous application protocols. Comparison of hearing sensitivity changes with gentamicin dosing revealed a flat curve with a near-zero mean for lower doses, suggesting that hearing changes with doses over this range were probably unrelated to the applied drug. Higher intracochlear doses were generated with repeated or continuous delivery protocols, which in some cases caused substantial hearing losses and an increased incidence of deafened ears.

CONCLUSIONS

One-shot application protocols produce gentamicin doses in the cochlea that have minimal risk to hearing at the frequencies tested. Repeated or continuous application protocols result in higher doses that in some cases damage hearing. The high variability of hearing changes, even with low gentamicin doses, calls into question the rationale for using individual hearing changes to titrate the applied dose.

Cochlear pharmacokinetics with local inner ear drug delivery using a three-dimensional finite-element computer model

HYPOTHESIS

Cochlear fluid pharmacokinetics can be better represented by three-dimensional (3D) finite-element simulations of drug dispersal.

BACKGROUND

Local drug deliveries to the round window membrane are increasingly being used to treat inner ear disorders. Crucial to the development of safe therapies is knowledge of drug distribution in the inner ear with different delivery methods. Computer simulations allow application protocols and drug delivery systems to be evaluated, and may permit animal studies to be extrapolated to the larger cochlea of the human.

METHODS

A finite-element 3D model of the cochlea was constructed based on geometric dimensions of the guinea pig cochlea. Drug propagation along and between compartments was described by passive diffusion. To demonstrate the potential value of the model, methylprednisolone distribution in the cochlea was calculated for two clinically relevant application protocols using pharmacokinetic parameters derived from a prior one-dimensional (1D) model. In addition, a simplified geometry was used to compare results from 3D with 1D simulations.

RESULTS

For the simplified geometry, calculated concentration profiles with distance were in excellent agreement between the 1D and the 3D models. Different drug delivery strategies produce very different concentration time courses, peak concentrations and basal-apical concentration gradients of drug. In addition, 3D computations demonstrate the existence of substantial gradients across the scalae in the basal turn.

CONCLUSION

The 3D model clearly shows the presence of drug gradients across the basal scalae of guinea pigs, demonstrating the necessity of a 3D approach to predict drug movements across and between scalae with larger cross-sectional areas, such as the human, with accuracy. This is the first model to incorporate the volume of the spiral ligament and to calculate diffusion through this structure. Further development of the 3D model will have to incorporate a more accurate geometry of the entire inner ear and incorporate more of the specific processes that contribute to drug removal from the inner ear fluids. Appropriate computer models may assist in both drug and drug delivery system design and can thus accelerate the development of a rationale-based local drug delivery to the inner ear and its successful establishment in clinical practice.

Local inner-ear drug delivery and pharmacokinetics

Several drugs that are applied directly to the inner ear are in widespread clinical use for the treatment of inner-ear disorders. Many new substances and drug delivery systems specific to the inner ear are under development and in some cases are being evaluated in animal experiments and in clinical studies. However, the pharmacokinetics of drugs in the inner ear is not well defined and the field is plagued by technical problems in obtaining pure samples of the inner-ear fluids for analysis. Nevertheless, a basic understanding of the mechanisms of drug dispersal in the inner ear has emerged, which facilitates the design and interpretation of future pharmacokinetic studies.

Menière's disease in the elderly

OBJECTIVES

To assess the prevalence, presentation, treatment, and evolution of Menière's disease in elderly patients (> or = 65 yr old).

STUDY DESIGN

Retrospective clinical study and case report.

SETTING

A neuro-otology referral center at the university hospital in Bern, Switzerland, and a neurotologic practice in Geneva, Switzerland.

PATIENTS

Patients were selected from the hospital clinic and otolaryngologic practice registers. Among 8423 neurotologic checkups performed between 1988 and 1998, 432 (5.1%) patients had definite Menière's disease and 66 (15.3%) of these patients were > or = 65 years old.

INTERVENTION

The files of these 66 patients were analyzed.

RESULTS

Menière's disease in the elderly had 2 modes of presentation: reactivation of longstanding Menière's disease (40.9%) and de novo Menière's disease (59.1%), where the first dizzy spells, tinnitus, and hearing loss appeared after 65 years of age. Drop attacks occurred in 11.1 and 25.6% of the cases, respectively, and could be responsible for misdiagnosis of strokes of the brainstem. The patients were treated by mild antivertiginous drugs (betahistine, cinnarizine). Twenty-seven patients (41%) underwent surgery: transtympanic ventilation tubes (19 patients), sacculotomy (4 patients), vestibular neurectomy (3 patients), surgical labyrinthectomy (1 patient). The vertigo spells disappeared in 73.3 to 100% of the cases according to the type of surgery performed.

CONCLUSION

Our study shows that Menière's disease in the elderly is not at all uncommon. It can appear as a de novo disease or as a reactivated longstanding disease. Drop attacks are more frequent than reported in general patient populations with Menière's disease and can mimic a stroke of the brainstem. Medical and surgical treatments have to be cautious because many of these elderly patients are fragile.

Continuous intratympanic infusion of gentamicin via a microcatheter in Menière's disease

Between 1995 and 1998, 11 patients with disabling Menière's disease were treated at our institution with a continuous gentamicin infusion into the middle ear via a microcatheter. The patients had frequent attacks of vertigo and vomiting (functional levels 3-5). Hearing threshold on the affected side was significantly worse than on the healthy side (stage 4+5). Gentamicin was applied by a high-precision insulin pump with a flow rate of 40 mg per day directly in front of the round window. Application was stopped as soon as signs of vestibular affection appeared. A good overall control of vertiginous spells was achieved in 8 patients. Eight patients experienced complete hearing loss on the affected side, 1 experienced a slight worsening, and 1 had no hearing change. There was no correlation between the cumulative gentamicin dosage and the hearing loss. Our findings show that in terms of hearing loss and hospitalization time the continuous gentamicin application is inferior to other applications presented in the literature.