Intratympanic Gentamicin Research Articles

The comparison between intratympanic gentamicin prehabilitation and postoperative virtual reality exposure to standard vestibular training in patients with vestibular schwannoma.

Resection of the vestibular schwannoma causes acute peripheral vestibular loss. The process of central compensation starts immediately afterward. The rehabilitation goal is to support this process and restore the quality of life. In this prospective single-center study, 67 consecutive patients underwent vestibular schwannoma resection (40 females, mean age 52 ± 12 years). The patients were divided into three groups: the prehabilitation with intratympanic gentamicin group, the virtual reality group (optokinetic stimulation via virtual reality goggles in the first ten days after the surgery), and the control group. All patients were examined with objective methods and completed questionnaires before the prehabilitation, before the surgery, at the hospital discharge, and after three months. Intratympanic gentamicin prehabilitation leads ipsilaterally to a significant aVOR reduction in all semicircular canals (p < 0.050), the increase of the unilateral weakness in air calorics (p = 0.026), and loss of cVEMPs responses (p = 0.017). Prehabilitation and postoperative exposure to virtual reality scenes improved the patient's perception of vertigo problems according to Dizziness Handicap Inventory (p = 0.039 and p = 0.076, respectively). These findings conform with the optokinetic testing results, which showed higher slow phase velocities at higher speeds (40deg/s) in both targeted groups compared to the control group. Preoperative intratympanic gentamicin positively affects peripheral vestibular function, influencing balance perception after VS resection. In long-term follow-up, prehabilitation and postoperative exposure to virtual reality improve patients' quality of life in the field of vertigo problems.

Pharmacological Interventions for Menière's Disease: A Systematic Review and Network Meta-Analysis.

Objective: Evaluation of the effectiveness and posttreatment effects of intratympanic gentamicin and corticosteroids in treating patients with Ménière's disease (MD). Methods: Based on PubMed and Embase databases, randomized controlled trials using intratympanic injections of 4 drugs (gentamicin, methylprednisolone, dexamethasone, and placebo) for the treatment of MD were searched from 1995 to October 2023, and the literature was screened according to inclusion and exclusion criteria, and data were netted for meta-analysis using Stata 17. Results: A total of 13 studies were selected, involving 559 participants, with follow-up time ranging from 3 to 28 months. Meta-analysis showed that there was no statistically significant difference in pure-tone average between gentamicin and dexamethasone [standardized mean difference (SMD) = 0.09, 95% confidence interval (CI) (-0.42, 0.24), P < .05]. Compared to placebo, intratympanic injection of gentamicin [risk ratio (RR) = 1.18, 95% CI (0.43, 1.93)], methylprednisolone [RR = 0.88, 95% CI (0.07, 1.70)], and dexamethasone [RR = 0.70, 95% CI (-0.01, 1.41)] all showed better efficacy in treating vertigo. For the treatment of tinnitus, the SUCRA ranking results showed that dexamethasone was the most effective, followed by methylprednisolone and gentamicin. Conclusion: Pharmacological intervention is more effective than placebo in treating MD. Although gentamicin treatment shows significant effects in treating vertigo, corticosteroid combination therapy is markedly superior to gentamicin in controlling hearing loss and vertigo symptoms.

A Randomised Controlled Trial Comparing Intratympanic Gentamicin with Methylprednisolone in Meniere's Disease with Good Hearing.

Randomised prospective parallel group trial. Tertiary care centre in South India. Forty patients with unilateral Meniere's disease and serviceable hearing with vertigo following 6months of conservative therapy were enrolled between November 2018 and March 2020. Twenty patients were administered with one dose of intratympanic Gentamicin (40mg/ml) and the other half were given intratympanic Methylprednisolone (40mg/ml, 4 injections given on alternate days). Pure tone audiogram, speech discrimination score, number of vertigo episodes, dizziness handicap inventory, tinnitus handicap inventory and functional scores were compared before treatment, 3months later and up to 24months. There was no significant difference between the two treatments with regard to short term as well as long term DHI scores, THI scores, Functional level score and average pure tone audiogram of patients. In patients with unilateral Meniere's disease who have good hearing, one dose of Gentamicin had equivalent effect to that of four doses of Methylprednisolone in vertigo and tinnitus control, hearing preservation and quality of life.

Pre-operative intratympanic gentamicin in patients undergoing retrosigmoid resection of large vestibular schwannomas: a pilot study.

Pre-operative intratympanic gentamicin in patients undergoing retrosigmoid resection of large vestibular schwannomas: a pilot study.

Sound Exposure Promotes Intratympanic Drug Delivery to the Inner Ear.

To investigate the impact of sound exposure, with the resultant windows vibration on perilymphatic concentrations following intratympanic (IT) dexamethasone and gentamicin in an animal model. Animal model blinded study. Animal facility of a tertiary medical center. Bilateral IT dexamethasone or gentamicin was applied to 15 tested rats. Following injections, each rat was exposed for 3minutes to free field 30 dB sound pressure level (SPL), 512 vHz noise, with 1external auditory canal plugged (contralateral control). Following noise exposure, perilymph was obtained from both ears. Drug concentrations were measured using ultrahigh-performance liquid chromatography-mass spectrometer. For dexamethasone, the average (±SD) perilymphatic steroidal concentration was 0.417 µg/mL (±0.549) in the control ears versus 0.487 µg/mL (±0.636) in the sound-exposed ears (P = .008). The average (±SD) gentamicin perilymphatic concentration was 8.628 µg/mL (±2.549) in the sound-exposed ears, compared to 4.930 µg/mL (±0.668) in the contralateral control (nonsound exposed) ears. Sound exposure promoted steroidal and gentamicin diffusion to the inner ear by an averaged (±SD) factor of 1.431 and 1.730 (±0.291 and 0.339), respectively. Low-intensity noise (30 dB SPL) was found to enhance dexamethasone phosphate and gentamicin diffusion to the inner ear (by an averaged factor of ∼1.4 and 1.7, respectively) in a murine model.

Trends in Procedural Management of Meniere's Disease: Analysis of a National Insurance Claims Database.

This study used a national insurance claims database to analyze trends in procedural management of Meniere's disease. Retrospective cohort analysis. Database study using United States inpatient and outpatient insurance claims submitted from January 2003 to December 2021. The Merative MarketScan Commercial and Medicare Claims Databases were queried for adults (≥18 years) with a diagnosis of Meniere's Disease according to International Classification of Diseases codes. Patients receiving procedures per Current Procedural Terminology codes for endolymphatic sac surgery, vestibular nerve section, labyrinthectomy, and intratympanic dexamethasone or gentamicin were identified. Temporal trends were analyzed by calculating annual percent change (APC) in the proportion of patients receiving procedures using Joinpoint regression. A total of 16,523 unique patients with MD receiving procedural management were identified. From 2003 to 2021, the proportion of patients managed with intratympanic dexamethasone increased (APC 1.76 [95% CI 1.53-1.98], P < .001). The proportion of patients receiving intratympanic gentamicin increased from 2003 to 2015 (APC 4.43 [95% CI 1.29-7.66], P = .008) but decreased from 2015 to 2021 (APC -10.87 [95% CI -18.31 to -2.76], P = .013). The proportion of patients receiving endolymphatic sac surgery (APC: -10.20 [95% CI -11.19 to -9.20], P < .001) and labyrinthectomy (APC: -6.29 [95% CI -8.12 to -4.42], P < .001) decreased from 2003 to 2021. From 2003 to 2021, there has been an increase in the use of intratympanic dexamethasone and a decrease in the use of intratympanic gentamicin, endolymphatic sac surgery, and labyrinthectomy for procedural management of Meniere's Disease.

Preliminary Evidence for the Effects of Gentamicin on Vertical Semicircular Canals

Introduction: Gentamicin is a vestibulotoxic antibiotic often used in patients with Ménière's disease for its vestibular ablative effects. Gentamicin’s effect on the horizontal semicircular canal does not always correlate with the degree of vertigo control achieved by patients; its effect on the vertical semicircular canals remains unknown. We sought to examine the effect of intratympanic gentamicin on vertical semicircular canal function in patients with Ménière's disease using video head impulse testing. Methods: A retrospective case series was carried out at a tertiary academic center. Patients with Ménière's disease who received ≥1 intratympanic gentamicin injection from 2019–2022 and had video head impulse testing performed were included. Outcomes of interest were vertical semicircular canal function following intratympanic gentamicin, correlations between vertical semicircular canal function and horizontal semicircular canal function, and residual symptoms following injection. Results: Ten patients met inclusion criteria. Twenty percent had abnormal V-SCC function prior to any injection and 40% following the first injection. There was an association between abnormal vertical and horizontal semicircular canal function following the first intratympanic gentamicin injection, though the relationship did not reach statistical significance (p = 0.058). While patients with abnormal vertical semicircular canal function following the first injection were less likely to report ongoing vertigo attacks, the relationship was not statistically significant (p = 0.260). Conclusions: Intratympanic gentamicin leads to changes in vertical semicircular canal function in at least a proportion of patients with Ménière's disease. Further study is required to better assess correlations between vertical semicircular canal function and symptom control following intratympanic gentamicin.

Improved Recovery after Vestibular Schwannoma Excision with Intratympanic Gentamicin Prehabilitation.

Translabyrinthine excision of a vestibular schwannoma is associated with acute vestibular failure. Preoperative intratympanic gentamicin (ITG) injections can improve objective balance function after surgery but its clinical benefits remain to be established. Adult patients undergoing translabyrinthine removal of a vestibular schwannoma between January 2014 and February 2018 underwent preoperative vestibular function testing. Patients were divided in to 3 groups, those with vestibular function (VF) who received ITG injections, those with VF but did not receive ITG and those with no VF. Groups were compared according to degree of vertigo, length of stay, time to unassisted mobilization, and postoperative anti-emetic consumption. Forty six patients had ITG injections (Group 1), 7 had residual VF but refused treatment (Group 2), 21 had no VF (Group 3). Group 1 had a significant improvement in vertigo over time whereas groups 2 and 3 did not. There was a statistically significant 70% decrease in time to independent mobilization between Group 1 and other groups and a 19% decrease in length of stay in Group 1 compared to other groups although this did not reach statistical significance. Two patients had injection-related complications. Group 1 used less anti-emetics than other groups but this was not statistically significant. Preoperative intratympanic gentamicin injection with vestibular rehabilitation exercises is associated with less postoperative vertigo and earlier postoperative mobilization. There was reduced duration of hospitalization and decreased consumption of anti-emetic but not significantly so possibly because of low numbers of patients in the no treatment group. 2 Laryngoscope, 134:3316-3322, 2024.

Therapeutic Response of Meniere's Disease Utilizing Sorbus domestica.

Introduction Meniere's disease (MD) is a chronic condition characterized by episodic attacks of vertigo, fluctuating hearing loss, and tinnitus. MD can impart a significant socioeconomic impact with associated progressive hearing loss. First-line therapies consist of diuretics and antihistamines, with second-line therapies including intratympanic steroids and pulse therapy. Third-linetreatments include endolymphatic sac surgery (ELSS) followed by intratympanic gentamicin injection and/or vestibular neurectomy. The gemmotherapy Sorbus domestica's inherent properties to regulate venous circulation and lymphatic drainage have been utilized in the European literature for the treatment of MD and the patients in this study. Methods Patients presenting for rehabilitation at Pulaski Health and Rehabilitation Facility with a history of vertigo were examined and, through history and specific exam, to define MD. This resulted in six patients whose symptoms and exam were consistent with MD and interfered with their therapeutic progression. These patients were offered and accepted treatment with Sorbus domestica for their MD. Results All patients responded with either resolution or significant improvement in their symptoms and hearing loss. Treatment also resulted in an improved and probably shortened rehabilitative course. All patients had no adverse reactions and were supplied with resources for continual treatment upon discharge. Conclusion Sorbus domestica is a safe and viable treatment option for MD. It has been useful, especially in treatment-resistant diseases, without side effects and can be utilized in initial cases with improvement or resolution of hearing loss.

Role of prior intratympanic gentamicin and corticosteroids therapy on speech understanding in patients with Menière's disease after cochlear implantation

AimIntratympanic injection of corticosteroids (ITC) and gentamicin therapy (ITG) are widely used treatments for vertigo in Meniere’s disease (MD). Even though studies show good results after cochlea implantation (CI) in MD patients when compared to non-MD groups, there is no indication on the effect of ITC and ITG prior to CI on hearing after CI. This study compares the post-operative hearing of CI patients with and without MD and patients who have received ITG or ITC prior to CI.MethodsIn a retrospective case control study, adult patients with MD who received CI from 2002 till 2021 were compared to a matched control group of CI patients without MD. Patients with prior ITC/ITG were extracted from MD group. Pre-operative audiological results were measured and trends across post-operative monosyllabic word recognition score at 65 decibels (WRS65CI) at switch-on, 3–6 months, 1 year and last yearly value were analyzed across all groups.Results28 MD ears were compared with 33 control ears. From MD ears 9 had received ITG and 6 ITC prior to CI. WRS65CI increased significantly with time within MD and control groups, but no difference in WRS65CI was found between these 2 groups. ITG ears showed fluctuating WRS65CI after CI with no change across time, while ITC ears showed significant increase in trend of WRS65CI values across time.ConclusionMD and non-MD patients showed comparable hearing results after CI. Prior ITC might positively influence hearing preservation after CI in MD patients whereas ITG group showed fluctuating hearing.

Comparative efficacy of intratympanic gentamicin and intratympanic corticosteroid in the treatment of Meniere's disease: a systematic review and meta-analysis.

We aimed to evaluate the efficacy of gentamicin compared to corticosteroids for the treatment of Meniere's disease. An extensive search was conducted in PubMed, Embase, and Web of Science until May 2024. For continuous outcomes, pooled effect estimates were determined by calculating the weighted mean difference (WMD), while for binary outcomes, the risk ratio (RR) was used, each accompanied by their respective 95% confidence intervals (CIs). Heterogeneity among the studies was assessed using Cochran's I 2 and Q statistics. A total of 12 studies were selected, involving 694 patients. Our analysis found that the gentamicin group demonstrates superior vertigo control rates compared to the corticosteroid group (RR: 1.36, 95% CI: 1.13 to 1.65, p < 0.001). In subgroup analysis, the gentamicin group showed a higher vertigo control rates at 6 months compared to the corticosteroid group (RR: 1.69, 95% CI: 1.28 to 2.24, p < 0.001); however, there was no statistically significant difference between the two groups at 12 months (RR: 1.48, 95% CI: 0.88 to 2.49, p = 0.14). Regarding changes in pure tone average, the corticosteroid group was superior to the gentamicin group (WMD: 4.41, 95% CI: 3.31 to 5.52, p < 0.001). Our study suggests that the intratympanic gentamicin group achieves higher vertigo control rates, whereas the corticosteroid group demonstrates better improvement in pure tone averages. However, the high heterogeneity in vertigo control rates warrants caution. Larger sample-sized randomized controlled trials are needed to further validate these findings.

Vestibular Drop Attack: An Analysis of the Therapeutic Response.

The present study evaluates the response to betahistine in patients who presented vestibular drops attacks in the context of Ménière's disease (MD) and the factors that can predict an unfavorable response to it. A total of 43 patients were analyzed, out of which 33 were diagnosed with MD. This is a descriptive, cross-sectional study with retrospective data collection. Data as regards age, accompanying symptoms, etiological diagnosis and response to MD treatment were collected. A statistical analysis was carried out, and we found that the disease evolution time and specific alterations in the vestibulospinal and oculomotor physical examination present an unfavorable response to betahistine. Failures for betahistine were treated with intratympanic gentamicin, with which symptomatic control was achieved in all cases.

Vestibular Prehabilitation-A Single UK Center Experience and Literature Review.

Objectives To assess whether vestibular prehabilitation with intratympanic gentamicin is a useful preoperative adjunct in allowing for early mobilization and short length of stay in patients with vestibular schwannoma (VS). Design Retrospective single-center study and literature review. Setting Tertiary neurosurgical center. Participants Adult patients undergoing surgery for VS. Main Outcome Measures Our primary outcome measures were evidence of compensation following prehabilitation (defined as saccades becoming more covert and clustered on video head impulse testing-vHIT), length of stay, and days until mobilization. Secondary outcome measures were reduction in gain on vHIT following treatment as well as need for antiemetics postoperatively. Results Ten patients have been treated at our center and the majority have shown preoperative reduction in gain and evidence of compensation on vHIT. Median time to mobilization was 1 day and modal length of stay was 6 days. We found the current evidence to be variable, with small sample sizes and significant variation in outcome measures used. Conclusion Overall we have found that the use of vestibular prehabilitation enables early mobilization, shortened length of stay and appears to be a promising preoperative adjunct in this population. Further research and assessment with a multicenter prospective clinical trial is merited.

Efficacy and preservation of hearing with low-dose gentamicin in unilateral meniere's disease: A clinical symptomatology-based study

PurposeMeniere's disease (MD), a disorder of the inner ear, presents numerous therapeutic challenges, and intratympanic (IT) gentamicin has been proposed for intractable cases. However, controversy regarding dosage and method persists. The purpose of this study was to assess the efficacy and safety of low-dose IT gentamicin on vertigo attacks in MD using a clinical symptomatology-based method, wherein administration was repeated only if vertigo attacks recurred, with a 2-week interval between injections. Materials and methodsThis study included 88 patients with unilateral intractable MD. All patients received one to five IT injections with 0.5 ml of 10 mg of gentamicin (80 mg/2 ml) with an interval of 2 weeks between injections. Vertigo attacks were evaluated before and after therapy and categorized into classes A–F according to the 2015 Equilibrium Committee criteria. Audiovestibular assessments, including Pure Tone Audiometry and Vestibulo-Ocular Reflex evaluations, were performed. ResultsBefore treatment, patients had an average of 4.4 vertigo attacks/month; after treatment, this average decreased to 0.52. The majority of patients (57 %) reached Class A or B vertigo control with five or fewer gentamicin injections. VOR gain was slightly affected on the healthy side and significantly reduced on the affected side. No hearing deterioration was found in any of the treated patients. ConclusionsLow-dose IT gentamicin administration based on clinical symptomatology can produce a satisfactory control of vertigo attacks after treatment. This protocol primarily affected the vestibular function, as demonstrated by the significant reduction in VOR gain on the affected side, while avoiding cochlear damage. The lack of adverse events and preservation of hearing underscore the safety and efficacy of this method. These findings have significant clinical implications, suggesting that a low-dose, clinical symptomatology-based gentamicin treatment regimen could be an effective and safe strategy for managing unilateral Meniere's disease in a larger population.

Intratympanic injection for treatment of inner ear diseases

Background: Intratympanic injection has emerged as a novel approach to bypass the blood-labyrinth barrier and effectively deliver drugs into the inner ear. This technique is used for treatment of various inner ear diseases and overcomes the limitations of systemic drug therapy. In this paper, we provide an overview of the application of intratympanic injection using steroids and gentamicin and highlight the major diseases and summarize the reported efficacy of this approach.Current Concepts: Intratympanic steroid injections have been used for treatment of various inner ear diseases, including sudden sensorineural hearing loss, Ménière disease, and tinnitus. Therapeutic effects of steroids include reducing inflammation, modulating the immune response, improving cochlear blood flow, and maintaining ion homeostasis. Intratympanic gentamicin injections are primarily used to minimize hearing loss and control vertigo symptoms in patients with Ménière disease. Gentamicin selectively injures vestibular hair cells with minimal ototoxicity compared with other aminoglycoside antibiotics.Discussion and Conclusion: Intratympanic injections offer several advantages, including targeted drug delivery, minimal systemic adverse effects, and rapid action. Reportedly, intratympanic steroid injections used as primary or salvage treatment are associated with positive outcomes in patients with sudden sensorineural hearing loss. Ménière disease also shows positive outcomes following intratympanic steroid and gentamicin injections. However, studies have reported conflicting results, and further research is required to standardize dosing and administration protocols. Intratympanic injections are a promising therapeutic option, and ongoing research is essential to optimize their efficacy and safety.

Prosthetic Stimulation of the Vestibular Nerve Can Evoke Robust Eye and Head Movements Despite Prior Labyrinthectomy.

Prosthetic electrical stimulation can evoke compensatory eye and head movement despite vestibular implant electrode insertion occurring years after prior labyrinthectomy. Vestibular implants sense head rotation and directly stimulate the vestibular nerve, bypassing damaged end organs. Animal research and current clinical trials have demonstrated the efficacy of this approach. However, candidacy criteria for vestibular implants currently require presence of a patent labyrinth in the candidate ear and at least aidable hearing in the opposite ear, thus excluding patients who have undergone prior labyrinthectomy for unilateral Menière's disease that later progressed to bilateral vestibular hypofunction. Eight years after right unilateral labyrinthectomy, we implanted stimulating electrodes in the previously exenterated right ear ampullae of a rhesus macaque monkey. The left labyrinth had long-standing hypofunction due to intratympanic gentamicin injection and surgical disruption. We used three-dimensional video-oculography to measure eye movement responses to prosthetic electrical stimulation. We also measured head-movement responses to prosthetic stimulation with the head unrestrained. Bilateral vestibular hypofunction was confirmed by absence of vestibuloocular reflex responses to whole-body rotation without prosthetic stimulation. For a subset of the implanted electrodes, prosthetic vestibular stimulation evoked robust compensatory eye and head movements. One electrode reliably elicited responses aligned with the implanted ear's anterior canal nerve regardless of the return electrode used. Similarly, a second electrode also elicited responses consistent with excitation of the horizontal canal nerve. Responses grew quasilinearly with stimulation rate and current amplitude. Prosthetic electrical stimulation targeting the vestibular nerve can be effective years after labyrinthectomy, if at least some parts of the vestibular nerve's ampullary branches remain despite destruction or removal of the membranous labyrinth.

USE OF SKULL VIBRATION-INDUCED NYSTAGMUS DURING FOLLOW-UP IN MÉNIÈRE.

Ménière's disease (MD) is an idiopathic disorder that affects patients' hearing and the inner ear balance. Intratympanic gentamicin (ITG) is also considered an effective treatment for uncontrolled MD characterized by persistent vertigo attacks despite therapy. The video head impulse test (vHIT) and the skull vibration-induced nystagmus (SVIN) are both validated test to assess the vestibular function. A progressive linear relationship has also been described between the slow-phase velocity (SPV) of SVIN with a skull vibrator at 100 Hz and the gain difference (healthy ear/affected ear) measured in vHIT. The objective of this study was to determine whether the SPV of the SVIN was correlated with the restoration of vestibular function after ITG and, consequently, whether the SVIN can predict the appearance of new vertigo attacks in patients with MD treated with ITG. A prospective longitudinal case-control study was conducted. We recorded several variables after ITG and during the follow-up and statistical analyses were performed. Two groups were compared, those who presented vertigo attacks 6 months after ITG and those who did not. Our sample included 88 patients with definite MD who were treated with ITG. Among the 18 patients who experienced vertigo attacks again, 15 showed recovery of the gain of the affected ear, while all 18 showed a reduction in the SPV of the SVIN. SPV of SVIN may have more sensitivity than vHIT for detecting recovery of vestibular function after intratympanic gentamicin (ITG) administration. To the best of our knowledge, this is the first study to describe the association between decreased SPV and the probability of vertigo attacks in patients with MD treated with ITG.

Pre-habilitation with intratympanic gentamicin in vestibular schwannomas: a systematic review.

To assess whether pre-habilitation with intratympanic gentamicin can accelerate vestibular compensation following vestibular schwannoma resection. Seventeen studies were retrieved from the databases Medline, PubMed, Frontiers, Cochrane Library, Cambridge Core and ScienceDirect. Eight of the 17 studies met our criteria; the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used. Heterogeneity, risk of bias and effect on post-operative recovery were assessed. Four of the eight studies showed a statistically positive effect of pre-habilitation with gentamicin on the post-operative recovery process; the remainder also reported benefits, although not statistically significant. No study reported negative effects. Limitations were linked mostly to the limited number of enrolled patients and the outcome assessment methods. Fifty per cent of the studies found a statistically positive effect of pre-habilitation with gentamicin prior to vestibular schwannoma resection. While the results are promising, due to the limited numbers further prospective studies are required to strengthen the evidence.

Binocular 3-D otolith-ocular reflexes: responses of chinchillas to natural and prosthetic stimulation after ototoxic injury and vestibular implantation.

The otolith end organs inform the brain about gravitational and linear accelerations, driving the otolith-ocular reflex (OOR) to stabilize the eyes during translational motion (e.g., moving forward without rotating) and head tilt with respect to gravity. We previously characterized OOR responses of normal chinchillas to whole body tilt and translation and to prosthetic electrical stimulation targeting the utricle and saccule via electrodes implanted in otherwise normal ears. Here we extend that work to examine OOR responses to tilt and translation stimuli after unilateral intratympanic gentamicin injection and to natural/mechanical and prosthetic/electrical stimulation delivered separately or in combination to animals with bilateral vestibular hypofunction after right ear intratympanic gentamicin injection followed by surgical disruption of the left labyrinth at the time of electrode implantation. Unilateral intratympanic gentamicin injection decreased natural OOR response magnitude to about half of normal, without markedly changing OOR response direction or symmetry. Subsequent surgical disruption of the contralateral labyrinth at the time of electrode implantation surgery further decreased OOR magnitude during natural stimulation, consistent with bimodal-bilateral otolith end organ hypofunction (ototoxic on the right ear, surgical on the left ear). Delivery of pulse frequency- or pulse amplitude-modulated prosthetic/electrical stimulation targeting the left utricle and saccule in phase with whole body tilt and translation motion stimuli yielded responses closer to normal than the deficient OOR responses of those same animals in response to head tilt and translation alone.NEW & NOTEWORTHY Previous studies to expand the scope of prosthetic stimulation of the otolith end organs showed that selective stimulation of the utricle and saccule is possible. This article further defines those possibilities by characterizing a diseased animal model and subsequently studying its responses to electrical stimulation alone and in combination with mechanical motion. We show that we can partially restore responses to tilt and translation in animals with unilateral gentamicin ototoxic injury and contralateral surgical disruption.

Skull-vibration-induced nystagmus test in patients who are candidates for intratympanic gentamicin injection

This study aims to evaluate the utility of the skull-vibration-induced nystagmus test (SVINT) in the selection of patients with Ménière's disease (MD) for intratympanic injection of gentamicin. To date the indications for this treatment have been based only on subjective elements. A retrospective study was performed in 20 patients diagnosed with unilateral MD. SVINT were performed monthly and the evoked responses were evaluated. After 6 months, the results from patients who were candidates for gentamicin treatment (G group) were compared with those who did not need it (nG group). Correlation with Dizziness Handicap Inventory (DHI) score was evaluated. 120 tests were performed. Positive SVINTs were identified in 52 cases (43.3%) and included excitatory nystagmus in 18 (34.7%), inhibitory nystagmus in 28 (53.8%), and atypical pattern in 6 cases (11.5%). A significant increase excitatory nystagmus was recorded in group G (p = 0.00001). Moreover, there was a significant increase in the DHI score in group G compared with the nG group (p < 0.0001) and in patients with evoked excitatory nystagmus. The finding of excitatory nystagmus during SVINTs performed on several occasions in the follow-up prior to intratympanic injection of gentamicin strengthens this therapeutic choice.