Intratympanic gentamicin treatment for Ménière's disease: a randomized, double-blind, placebo-controlled trial on dose efficacy - results of a prematurely ended study

Placebo effect in randomized controlled trials for Meniere's disease: A meta-analysis

PURPOSE

Meniere's Disease is a condition known for its recurrent vertigo, fluctuating sensorineural hearing loss, aural fullness, and tinnitus. Previous studies have demonstrated significant influence of placebo treatments. Our objective was to quantify the magnitude of the placebo effect in randomized controlled trials for Meniere's Disease.

MATERIALS AND METHODS

A systematic review was performed by searching PubMed, SCOPUS, CINAHL, and Cochrane databases from inception through September 27, 2022. Data extraction, quality rating, and risk of bias assessment were performed by two independent reviewers. A meta-analysis of mean differences with 95 % confidence interval, weighted summary proportions, and proportion differences were calculated using random and fixed effects models.

RESULTS

A total of 15 studies (N = 892) were included in the review. Significant improvement was seen in the functional level scores of the pooled placebo groups, with a mean difference of -0.6 points, (95%CI: -1.2 to -0.1). There was no difference in pure tone audiometry, speech discrimination score, or vertigo frequency at 1 and 3 months for the placebo group. Patient-reported vertigo episodes were improved in 52.5 % (95%CI: 39.2 to 65.5) of the placebo group and was significantly less than the pooled experimental group (90.1 %, 95%CI: 39.2 to 65.5, p < 0.001).

CONCLUSIONS

The placebo effect in Meniere's Disease trials is associated with some symptomatic improvement in subjective outcomes, such as patient reported vertigo episodes. However, the clinical significance is questionable across other outcomes measures, especially when analyzing objective data. The extent and strength of the placebo effect continues to be a hurdle in the search for better treatment options.

Intratympanic gentamicin for Ménière's disease

BACKGROUND

Ménière's disease is a condition that causes recurrent episodes of vertigo, associated with hearing loss and tinnitus. Aminoglycosides are sometimes administered directly into the middle ear to treat this condition. The aim of this treatment is to partially or completely destroy the balance function of the affected ear. The efficacy of this intervention in preventing vertigo attacks, and their associated symptoms, is currently unclear.

OBJECTIVES

To evaluate the benefits and harms of intratympanic aminoglycosides versus placebo or no treatment in people with Ménière's disease.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the Cochrane ENT Register; Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 14 September 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs in adults with a diagnosis of Ménière's disease comparing intratympanic aminoglycosides with either placebo or no treatment. We excluded studies with follow-up of less than three months, or with a cross-over design (unless data from the first phase of the study could be identified).  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were: 1) improvement in vertigo (assessed as a dichotomous outcome - improved or not improved), 2) change in vertigo (assessed as a continuous outcome, with a score on a numerical scale) and 3) serious adverse events. Our secondary outcomes were: 4) disease-specific health-related quality of life, 5) change in hearing, 6) change in tinnitus and 7) other adverse effects. We considered outcomes reported at three time points: 3 to < 6 months, 6 to ≤ 12 months and > 12 months. We used GRADE to assess the certainty of evidence for each outcome.  MAIN RESULTS: We included five RCTs with a total of 137 participants. All studies compared the use of gentamicin to either placebo or no treatment. Due to the very small numbers of participants in these trials, and concerns over the conduct and reporting of some studies, we considered all the evidence in this review to be very low-certainty.  Improvement in vertigo This outcome was assessed by only two studies, and they used different time periods for reporting. Improvement in vertigo was reported by more participants who received gentamicin at both 6 to ≤ 12 months (16/16 participants who received gentamicin, compared to 0/16 participants with no intervention; risk ratio (RR) 33.00, 95% confidence interval (CI) 2.15 to 507; 1 study; 32 participants; very low-certainty evidence) and at > 12 months follow-up (12/12 participants receiving gentamicin, compared to 6/10 participants receiving placebo; RR 1.63, 95% CI 0.98 to 2.69; 1 study; 22 participants; very low-certainty evidence). However, we were unable to conduct any meta-analysis for this outcome, the certainty of the evidence was very low and we cannot draw any meaningful conclusions from the results.  Change in vertigo Again, two studies assessed this outcome, but used different methods of measuring vertigo and assessed the outcome at different time points. We were therefore unable to carry out any meta-analysis or draw any meaningful conclusions from the results. Global scores of vertigo were lower for those who received gentamicin at both 6 to ≤ 12 months (mean difference (MD) -1 point, 95% CI -1.68 to -0.32; 1 study; 26 participants; very low-certainty evidence; four-point scale; minimally clinically important difference presumed to be one point) and at > 12 months (MD -1.8 points, 95% CI -2.49 to -1.11; 1 study; 26 participants; very low-certainty evidence). Vertigo frequency was also lower at > 12 months for those who received gentamicin (0 attacks per year in participants receiving gentamicin compared to 11 attacks per year for those receiving placebo; 1 study; 22 participants; very low-certainty evidence).  Serious adverse events None of the included studies provided information on the total number of participants who experienced a serious adverse event. It is unclear whether this is because no adverse events occurred, or because they were not assessed or reported.  AUTHORS' CONCLUSIONS: The evidence for the use of intratympanic gentamicin in the treatment of Ménière's disease is very uncertain. This is primarily due to the fact that there are few published RCTs in this area, and all the studies we identified enrolled a very small number of participants. As the studies assessed different outcomes, using different methods, and reported at different time points, we were not able to pool the results to obtain more reliable estimates of the efficacy of this treatment. More people may report an improvement in vertigo following gentamicin treatment, and scores of vertigo symptoms may also improve. However, the limitations of the evidence mean that we cannot be sure of these effects. Although there is the potential for intratympanic gentamicin to cause harm (for example, hearing loss) we did not find any information about the risks of treatment in this review.  Consensus on the appropriate outcomes to measure in studies of Ménière's disease is needed (i.e. a core outcome set) in order to guide future studies in this area and enable meta-analysis of the results. This must include appropriate consideration of the potential harms of treatment, as well as the benefits.

Potential nanotechnology-based diagnostic and therapeutic approaches for Meniere's disease

Meniere's disease (MD) is a progressive inner ear disorder involving recurrent and prolonged episodes or attacks of vertigo with associated symptoms, resulting in a significantly reduced quality of life for sufferers. In most cases, MD starts in one ear; however, in one-third of patients, the disorder progresses to the other ear. Unfortunately, the etiology of the disease is unknown, making the development of effective treatments difficult. Nanomaterials, including nanoparticles (NPs) and nanocarriers, offer an array of novel diagnostic and therapeutic applications related to MD. NPs have specific features such as biocompatibility, biochemical stability, targetability, and enhanced visualization using imaging tools. This paper provides a comprehensive and critical review of recent advancements in nanotechnology-based diagnostic and therapeutic approaches for MD. Furthermore, the crucial challenges adversely affecting the use of nanoparticles to treat middle ear disorders are investigated. Finally, this paper provides recommendations and future directions for improving the performances of nanomaterials on theragnostic applications of MD.

Interventions for Menière's disease: an umbrella systematic review

OBJECTIVES

To systematically review the efficacy of interventions for Menière's disease (MD) to report clinical implications of the results and to identify areas for future valuable research.

METHODS

In line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Abstracts (PRISMA-A) guideline, a systematic online database search was conducted in which MEDLINE (PubMed), Embase (Ovid) and CENTRAL (Cochrane Library) were searched until May 2021 in order to search for the efficacy of treatment was analysed in a systematic review. Systematic reviews (SRs) on treatments for MD were screened for eligible interventions. From these SRs, we included placebo randomised controlled trials (RCTs). A separate search was conducted to identify RCTs on treatment modalities that were systematically reviewed yet published after the conduction of these SRs. The primary outcome was control of vertigo as defined by the American guideline as published in 1995. The PRISMA-A and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to appraise and evaluate the certainty of evidence.

RESULTS

We found five SRs from which 19 RCTs were extracted. Five RCTs were added by the separate search resulting in a total of 25 RCTs (n=1248) which evaluated the efficacy of betahistine dihydrochloride, intratympanic injections with gentamicin or steroids, endolymphatic sac surgery and pressure pulse therapy. Evidence on the efficacy of interventions for patients with MD is generally of low certainty. Betahistine (48 mg per day and 144 mg per day) and positive pressure therapy probably do not reduce MD symptoms when compared with placebo. Intratympanic injection with gentamicin or steroids, or treatment with endolymphatic surgery may reduce symptoms in MD when compared with placebo.

CONCLUSIONS

A definite effective and well-tolerated therapy for MD has yet to be discovered and information on the natural course of disease is one of the biggest flaws in current research.

PROSPERO REGISTRATION NUMBER

CRD4201502424.

Effects of intratympanic gentamicin and intratympanic glucocorticoids in Ménière's disease: a network meta-analysis

OBJECTIVE

Intratympanic therapies, usually including glucocorticoid and gentamicin, are becoming worldwide used in clinical practice of Ménière's disease today. However, clinical efficacy and safety of these two therapies are still in controversial.

DATA SOURCES

Electronic searches in PubMed, CENTRAL, Web of Science, EMBASE, CINAHL, ClinicalTrials.gov and the European Union Clinical Trials Register were conducted from inception until September 2020.

REVIEW METHODS

The pre-specified protocol of this systematic review and meta-analysis has been registered and published in November 2018 (PROSPERO Identifier: CRD42018114389). All randomized controlled trials of intratympanic gentamicin or glucocorticoids for Ménière's disease, compared with each other or placebo, were considered for this review.

RESULTS

Ten studies with 455 patients met the inclusion criteria. Pooled results indicated significant advantage of intratympanic gentamicin and glucocorticoids over placebo treatments in vertigo control (gentamicin vs placebo: risk rate, RR, 2.56; 95% CI 1.18-5.54; glucocorticoids vs placebo: RR, 3.02; 95% CI 1.36-6.73). There was no significant difference between gentamicin and glucocorticoids in vertigo control (gentamicin vs placebo: RR, 1.18; 95% CI 0.97-1.45). Intratympanic glucocorticoids showed better hearing protective results than gentamicin (change of pure tone audiometric, PTA, mean difference, MD, - 6.48 dB; 95% CI - 11.84 to - 1.13 dB; change of speech discrimination scale, SDS, MD 7.69%; 95% CI 0.83-14.55%).

CONCLUSIONS

Intratympanic gentamicin and glucocorticoids are two effective approaches to control vertigo symptoms for Ménière's disease. Glucocorticoids showed a potentially better hearing protective role over gentamicin.

Current and Emerging Medical Therapies for Dizziness

Medical therapies for dizziness are aimed at vertigo reduction, secondary symptom management, or the root cause of the pathologic process. Acute peripheral vertigo pharmacotherapies include antihistamines, calcium channel blockers, and benzodiazepines. Prophylactic pharmacotherapies vary between causes. For Meniere disease, betahistine and diuretics remain initial first-line oral options, whereas intratympanic steroids and intratympanic gentamicin are reserved for uncontrolled symptoms. For cerebellar dizziness and oculomotor disorders, 4-aminopyridine may provide benefit. For vestibular migraine, persistent postural perceptual dizziness and mal de débarquement, treatment options overlap and include selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants and calcium channel blockers.

3D-Printed Microneedles Create Precise Perforations in Human Round Window Membrane in Situ

HYPOTHESIS

Three-dimensional (3D)-printed microneedles can create precise holes on the scale of micrometers in the human round window membrane (HRWM).

BACKGROUND

An intact round window membrane is a barrier to delivery of therapeutic and diagnostic agents into the inner ear. Microperforation of the guinea pig round window membrane has been shown to overcome this barrier by enhancing diffusion 35-fold. In humans, the challenge is to design a microneedle that can precisely perforate the thicker HRWM without damage.

METHODS

Based on the thickness and mechanical properties of the HRWM, two microneedle designs were 3D-printed to perforate the HRWM from fresh frozen temporal bones in situ (n = 18 total perforations), simultaneously measuring force and displacement. Perforations were analyzed using confocal microscopy; microneedles were examined for deformity using scanning electron microscopy.

RESULTS

HRWM thickness was determined to be 60.1 ± 14.6 (SD) μm. Microneedles separated the collagen fibers and created slit-shaped perforations with the major axis equal to the microneedle shaft diameter. Microneedles needed to be displaced only minimally after making initial contact with the RWM to create a complete perforation, thus avoiding damage to intracochlear structures. The microneedles were durable and intact after use.

CONCLUSION

3D-printed microneedles can create precise perforations in the HRWM without damaging intracochlear structures. As such, they have many potential applications ranging from aspiration of cochlear fluids using a lumenized needle for diagnosis and creating portals for therapeutic delivery into the inner ear.

Use of Super Paramagnetic Iron Oxide Nanoparticles as Drug Carriers in Brain and Ear: State of the Art and Challenges

Drug delivery and distribution in the central nervous system (CNS) and the inner ear represent a challenge for the medical and scientific world, especially because of the blood-brain and the blood-perilymph barriers. Solutions are being studied to circumvent or to facilitate drug diffusion across these structures. Using superparamagnetic iron oxide nanoparticles (SPIONs), which can be coated to change their properties and ensure biocompatibility, represents a promising tool as a drug carrier. They can act as nanocarriers and can be driven with precision by magnetic forces. The aim of this study was to systematically review the use of SPIONs in the CNS and the inner ear. A systematic PubMed search between 1999 and 2019 yielded 97 studies. In this review, we describe the applications of the SPIONS, their design, their administration, their pharmacokinetic, their toxicity and the methods used for targeted delivery of drugs into the ear and the CNS.

Pharmacologic and surgical therapies for patients with Meniere's disease: A systematic review and network meta-analysis

BACKGROUND

Meniere's disease (MD) is a chronic condition of the inner ear consisting of symptoms that include vertigo attacks, fluctuating sensorineural hearing loss, tinnitus and aural fullness. Despite availability of various interventions, there is uncertainty surrounding their relative efficacy, thus making it difficult to select the appropriate treatments for MD. The objective of this systematic review was to assess the relative effects of the available pharmacologic and surgical interventions in patients with MD with regard to vertigo and other key patient outcomes based on data from randomized clinical trials (RCTs).

METHODS

Our published protocol registered with PROSPERO (CRD42019119129) provides details on eligibility criteria and methods. We searched various databases including MEDLINE, Embase and the Cochrane Library from inception to December 10th, 2018. Screening at citation and full-text levels and risk of bias assessment were performed by two independent reviewers in duplicate, with discrepancies resolved by consensus or third-party adjudication. Bayesian network meta-analyses (NMA) were performed for hearing change and vertigo control outcomes, along with pairwise meta-analyses for these and additional outcomes.

RESULTS

We identified 2,889 unique citations, that yielded 23 relevant publications describing 18 unique RCTs (n = 1,231 patients). Overall, risk-of bias appraisal suggested the evidence base to be at unclear or high risk of bias. Amongst pharmacologics, we constructed treatment networks of five intervention groups that included placebo, intratympanic (IT) gentamicin, oral high-dose betahistine, IT steroid and IT steroid plus high-dose betahistine for NMAs of hearing change (improvement or deterioration) and complete vertigo control. IT steroid plus high-dose betahistine was associated with the largest difference in hearing improvement compared to placebo, followed by high-dose betahistine and IT steroid (though 95% credible intervals failed to rule out the possibility of no difference), while IT gentamicin was worse than IT steroid. The NMA of complete vertigo control suggested IT gentamicin was associated with the highest probability of achieving better complete vertigo control compared to placebo, followed by IT steroid plus high-dose betahistine. Only two studies related to surgical interventions were found, and data suggested no statistically significant difference in hearing changes between endolymphatic duct blockage (EDB) versus endolymphatic sac decompression (ESD), and ESD with or without steroid injection. One trial reported that 96.5% of patients in EDB group compared to 37.5% of the patients in ESD group achieved complete vertigo control 24 months after surgery (p = 0.002).

CONCLUSION

To achieve both hearing preservation and vertigo control, the best treatment option among the pharmacologic interventions compared may be IT steroid plus high-dose betahistine, considering that IT gentamicin may have good performance to control vertigo but may be detrimental to hearing preservation with high cumulative dosage and short interval between injections. However, IT steroid plus high-dose betahistine has not been compared in head-to-head trials against other interventions except for IT steroid alone in one trial, thus future trials that compare it with other interventions will help establish comparative effectiveness with direct evidence.

Clinical Practice Guideline: Ménière's Disease

OBJECTIVE

Ménière's disease (MD) is a clinical condition defined by spontaneous vertigo attacks (each lasting 20 minutes to 12 hours) with documented low- to midfrequency sensorineural hearing loss in the affected ear before, during, or after one of the episodes of vertigo. It also presents with fluctuating aural symptoms (hearing loss, tinnitus, or ear fullness) in the affected ear. The underlying etiology of MD is not completely clear, yet it has been associated with inner ear fluid (endolymph) volume increases, culminating in episodic ear symptoms (vertigo, fluctuating hearing loss, tinnitus, and aural fullness). Physical examination findings are often unremarkable, and audiometric testing may or may not show low- to midfrequency sensorineural hearing loss. Conventional imaging, if performed, is also typically normal. The goals of MD treatment are to prevent or reduce vertigo severity and frequency; relieve or prevent hearing loss, tinnitus, and aural fullness; and improve quality of life. Treatment approaches to MD are many and typically include modifications of lifestyle factors (eg, diet) and medical, surgical, or a combination of therapies.

PURPOSE

The primary purpose of this clinical practice guideline is to improve the quality of the diagnostic workup and treatment outcomes of MD. To achieve this purpose, the goals of this guideline are to use the best available published scientific and/or clinical evidence to enhance diagnostic accuracy and appropriate therapeutic interventions (medical and surgical) while reducing unindicated diagnostic testing and/or imaging.

Long-Term Follow-Up of Intratympanic Methylprednisolone Versus Gentamicin in Patients With Unilateral Menière's Disease

OBJECTIVES

To determine whether long term (>48 months) symptomatic vertigo control is sustained in patients with Menière's disease from a previous comparative trial of intratympanic methylprednisolone versus gentamicin, and if the two treatments remain nonsignificantly different at long-term follow-up.

STUDY DESIGN

Mail survey recording vertigo frequency in the previous one and six months, further intratympanic treatment received, and validated symptom questionnaires.

SETTING

Outpatient hospital clinic setting.

PATIENTS

Adult patients with definite unilateral refractory Menière's disease, who previously received intratympanic treatment in a comparative trial.

INTERVENTION

A survey of trial participants who received intratympanic gentamicin (40 mg/mL) or methylprednisolone (62.5 mg/mL).

OUTCOME MEASURES

Primary: number of vertigo attacks in the 6 months prior to receiving this survey compared with the 6 months before the first trial injection. Secondary number of vertigo attacks over the previous 1 month; validated symptom questionnaire scores of tinnitus, dizziness, vertigo, aural fullness, and functional disability.

RESULTS

Forty six of the 60 original trial patients (77%) completed the survey, 24 from the gentamicin and 22 from the methylprednisolone group. Average follow-up was 70.8 months (standard deviation 17.0) from the first treatment injection. Vertigo attacks in the 6 months prior to receiving the current survey reduced by 95% compared to baseline in both drug groups (intention-to-treat analysis, both p < 0.001). No significant difference between drugs was found for the primary and secondary outcomes. Eight participants (methylprednisolone = 5 and gentamicin = 3) required further injections for relapse after completing the original trial.

CONCLUSION

Intratympanic methylprednisolone treatment provides effective long-lasting relief of vertigo, without the known inner-ear toxicity associated with gentamicin. There are no significant differences between the two treatments at long term follow-up.

Inner ear delivery: Challenges and opportunities

OBJECTIVES

The treatment of inner ear disorders remains challenging due to anatomic barriers intrinsic to the bony labyrinth. The purpose of this review is to highlight recent advances and strategies for overcoming these barriers and to discuss promising future avenues for investigation.

DATA SOURCES

The databases used were PubMed, EMBASE, and Web of Science.

RESULTS

Although some studies aimed to improve systemic delivery using nanoparticle systems, the majority enhanced local delivery using hydrogels, nanoparticles, and microneedles. Developments in direct intracochlear delivery include intracochlear injection and intracochlear implants.

CONCLUSIONS

In the absence of a systemic drug that targets only the inner ear, the best alternative is local delivery that harnesses a combination of new strategies to overcome anatomic barriers. The combination of microneedle technology with hydrogel and nanoparticle delivery is a promising area for future investigation.

LEVEL OF EVIDENCE

NA.

Different medications for the treatment of Ménière's disease by intratympanic injection: A systematic review and network meta-analysis

BACKGROUND

It is generally accepted that intratympanic injection provides an effective approach to manage severe vertigo in Ménière's disease. Although there are several medications available, that which is the most effective is still subject to debate.

OBJECTIVE

To assess the effectiveness and safety of the different medications used in the treatment of Ménière's disease by intratympanic injection using a network meta-analysis.

METHODS

PubMed, EMBASE, CINAHL and CENTRAL were searched. Only randomised controlled trials that compared the effectiveness of medications used for intratympanic injection to treat Ménière's disease with each other or a placebo were included. The primary outcome assessed was the effectiveness of medication in the management of vertigo symptoms. The effectiveness was expressed in terms of risk ratio (RR) with a 95% credible interval (CrI) for individual studies analysed. Network meta-analyses were performed by Stata version 15.0 using the network package.

RESULTS

Nine studies involving 314 patients treated with five different medications were included in the present analysis. A number of injections given varied from 1 to 10 and the follow-up time from 3 to 28 months. When compared to each other or to a placebo, Gentamicin was found to be the most efficacious medication, followed by Methylprednisolone, Latanoprost, Dexamethasone and Ganciclovir in order of effectiveness. However, no significant difference in efficacy was found between Gentamicin and Methylprednisolone when outcomes from studies with a follow-up time equal to or more than 24 months were analysed. It was not possible to conduct subgroup and sensitivity analysis because of the limited number of studies that were included.

CONCLUSION

All medications are more effective than a placebo in the treatment of Ménière's disease by intratympanic injection. According to the SUCRA, Gentamicin ranked the most effective, with Gentamicin and Methylprednisolone equally effective in the long-term effect. When the potential risk of hearing loss induced by Gentamicin is taken into consideration, Methylprednisolone may be the best choice for the treatment of Ménière's disease by intratympanic injection.

Long-term Vertigo Control and Vestibular Function After Low-dose On-demand Transtympanic Gentamicin for Refractory Menière's Disease

OBJECTIVE

To describe the long-term clinical vertigo control along with measured lateral canal vestibular function in patients with unilateral refractory Menière's disease (MD) treated with gentamicin transtympanic injections (TTI).

STUDY DESIGN

Retrospective analytic study.

SETTING

Tertiary referral center.

PATIENTS

Thirty-eight patients treated by TTI for medically refractory unilateral MD, defined by the 1995 AAO-HNS criteria, between May 2006 and December 2012.

INTERVENTION(S)

One-year course of treatment with gentamicin TTI following a low dose on-demand protocol. TTI were repeated in new courses of treatment when MD recurrence occurred.

MAIN OUTCOME MEASURE(S)

AAO-HNS class of control, caloric tests (CalT), recurrence rate.

RESULTS

After an average clinical follow-up of 71 months, all patients entered a class of control A (78%) or B (22%), with an average of 2.3 TTI received. The mean maximal obtained deficit was 88.5%, and the mean long-term deficit was 85.5%. Ten (26%) patients had disease recurrence requiring a new course of treatment. A value of the first CalT in the 3 months following the first TTI strictly higher than 78% was significantly associated with disease control and the absence of symptom recurrence (p≤0.01). In the "recurrence" group, four patients had a significantly lower mean value of all CalT performed after the first TTI when compared with other patients (p≤0.001), indicating gentamicin resistance CONCLUSION:: Achieving a sustainable vestibular deficit on caloric testing is key for MD symptom control after gentamicin TTI. Gentamicin resistance must be diagnosed early to adapt therapeutic strategies.

Menière's disease: combined pharmacotherapy with betahistine and the MAO-B inhibitor selegiline-an observational study

OBJECTIVES

Since oral betahistine has a very high first-pass effect (ca. 99%), metabolized by monoamine oxidases (MAO), the benefits of a high-dosage betahistine monotherapy were compared with those of a lower dosage of betahistine in combination with the MAO-B inhibitor (MAO-B) selegiline on the frequency of acute attacks of vertigo in patients with Menière's disease (MD).

METHODS

Thirteen adults aged 40-75 years (mean 58.9 years; six females) had initially been treated with a high dosage of betahistine dihydrochloride for at least 1 year. Under this therapy, all of them had ≤ 1 attack for ≥ 3 months prior to the combination pharmacotherapy. Subsequently, they received 5 mg/day selegiline and the dosage of betahistine was reduced to about one tenth and then individually adjusted to the dosage needed to achieve the same treatment response (≤ 1 per 3 months, observational period of at least 6 months).

RESULTS

The initial dosage for the long-term "titration" of the attacks of vertigo was 9-80 24-mg tablets/day (mean 37.3), i.e. 216-1920 mg/day (mean 895.4 mg/day). After the combination with selegiline, the dosage needed to achieve the same benefit for ≥ 3 months was 3-36 24-mg tablets (mean 8.5), i.e., 72-864 mg/day [mean 204.9 mg/day, p < 0.001 (paired t test)]. One patient transiently stopped the treatment with selegiline, another one reduced the dosage to 2.5 mg/day and the attacks re-occurred after 2-4 weeks. Six out of 13 patients reported transient fullness of the head during the combined treatment; in 2 of them this went away when they switched to 2.5 mg bid. In the longer term (> 9 months), one patient had to increase the selegiline dosage to 5 mg bd, one patient stopped the treatment with selegiline.

CONCLUSIONS

The achievement of the same clinical effect with a significantly lower (about 1/5) dosage of betahistine can be explained by the inhibition of the MAO-B by selegiline leading to higher serum concentrations of betahistine. This approach is in line with recent developments to bypass the first-pass effect of betahistine by transbuccal or intranasal application. Despite the substantial methodological limitations of such an observational study, this combined pharmacotherapy could be an alternative to a high-dosage monotherapy with betahistine of MD.

Sustained and Transient Vestibular Systems: A Physiological Basis for Interpreting Vestibular Function

Otolithic afferents with regular resting discharge respond to gravity or low-frequency linear accelerations, and we term these the static or sustained otolithic system. However, in the otolithic sense organs, there is anatomical differentiation across the maculae and corresponding physiological differentiation. A specialized band of receptors called the striola consists of mainly type I receptors whose hair bundles are weakly tethered to the overlying otolithic membrane. The afferent neurons, which form calyx synapses on type I striolar receptors, have irregular resting discharge and have low thresholds to high frequency (e.g., 500 Hz) bone-conducted vibration and air-conducted sound. High-frequency sound and vibration likely causes fluid displacement which deflects the weakly tethered hair bundles of the very fast type I receptors. Irregular vestibular afferents show phase locking, similar to cochlear afferents, up to stimulus frequencies of kilohertz. We term these irregular afferents the transient system signaling dynamic otolithic stimulation. A 500-Hz vibration preferentially activates the otolith irregular afferents, since regular afferents are not activated at intensities used in clinical testing, whereas irregular afferents have low thresholds. We show how this sustained and transient distinction applies at the vestibular nuclei. The two systems have differential responses to vibration and sound, to ototoxic antibiotics, to galvanic stimulation, and to natural linear acceleration, and such differential sensitivity allows probing of the two systems. A 500-Hz vibration that selectively activates irregular otolithic afferents results in stimulus-locked eye movements in animals and humans. The preparatory myogenic potentials for these eye movements are measured in the new clinical test of otolith function—ocular vestibular-evoked myogenic potentials. We suggest 500-Hz vibration may identify the contribution of the transient system to vestibular controlled responses, such as vestibulo-ocular, vestibulo-spinal, and vestibulo-sympathetic responses. The prospect of particular treatments targeting one or the other of the transient or sustained systems is now being realized in the clinic by the use of intratympanic gentamicin which preferentially attacks type I receptors. We suggest that it is valuable to view vestibular responses by this sustained-transient distinction.

Intratympanic therapy in Meniere's syndrome or disease: up to date evidence for clinical practice

BACKGROUND

Meniere's syndrome or disease (MS/D) is typically characterised by episodic vertigo, aural fullness, tinnitus and fluctuating hearing loss. There are multiple options available for treatment with variation in consensus on the best intervention.

OBJECTIVE

To evaluate the evidence on the efficacy of intratympanic therapies [steroids, gentamicin, antivirals and other therapies] on the frequency and severity of vertigo and other symptoms of MS/D.

SEARCH STRATEGY

A literature search was performed on AMED, EMBASE, HMIC, MEDLINE, PsycINFO, BNI, CINAHL, HEALTH BUSINESS ELITE, CENTRAL and Cochrane Ear, Nose and Throat disorders group trials register using various MeSH. The search was restricted to English and human subjects, and the last date of search was December 2014.

SELECTION CRITERIA

Randomised controlled trials of intratympanic therapies [steroids, gentamicin antivirals and latanoprost] versus a placebo or another treatment.

RESULTS

We analysed 8 RCT's comparing intratympanic steroids, gentamicin, ganciclovir (antiviral) and latanoprost versus another form of intratympanic treatment or placebo.

CONCLUSIONS

On the basis of 6 RCT's (n = 242), there is evidence to support the effectiveness of intratympanic steroids and gentamicin to control symptoms of vertigo in MS/D albeit with a risk of hearing loss with gentamicin. However, there was no consensus found on doses or treatment protocols. There was no evidence to support the use of other forms of intratympanic therapy (antivirals and latanoprost) in MS/D.