Hearing Loss after Intratympanic Gentamicin Therapy for Unilateral Ménière's Disease

Chronic symptoms in patients with unilateral vestibular hypofunction: systematic review and meta-analysis

Objective

To systematically evaluate the full spectrum of self-reported chronic symptoms in patients with unilateral vestibular hypofunction (UVH) and to investigate the effect of interventions on these symptoms.

Methods

A systematic review was conducted following the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis Statement (PRISMA). A literature search was performed in Pubmed, Web of Science, Embase, and Scopus to investigate self-reported symptoms and self-report questionnaires in patients with UVH. All original studies ranging from full-text clinical trials to case reports, written in English, German, and French, were included. The frequency of self-reported symptoms was presented. For self-report questionnaires, a meta-analysis was carried out to synthesize scale means by the pre- and post-intervention means and mean changes for studies that investigated interventions.

Results

A total of 2,110 studies were retrieved. Forty-seven studies were included after title-abstract selection and full-text selection by two independent reviewers. The symptoms of UVH patients included chronic dizziness (98%), imbalance (81%), symptoms worsened by head movements (75%), visually induced dizziness (61%), symptoms worsened in darkness (51%), and oscillopsia (22%). Additionally, UVH could be accompanied by recurrent vertigo (77%), tiredness (68%), cognitive symptoms (58%), and autonomic symptoms (46%). Regarding self-report questionnaires, UVH resulted on average in a moderate handicap, with an estimated mean total score on the Dizziness Handicap Inventory (DHI) and the Vertigo Symptom Scale (VSS) of 46.31 (95% CI: 41.17-51.44) and 15.50 (95% CI: 12.59-18.41), respectively. In studies that investigated the effect of vestibular intervention, a significant decrease in the estimated mean total DHI scores from 51.79 (95% CI: 46.61-56.97) (pre-intervention) to 27.39 (95% CI: 23.16-31.62) (post intervention) was found (p < 0.0001). In three studies, the estimated mean total Visual Analog Scale (VAS) scores were 7.05 (95% CI, 5.64-8.46) (pre-intervention) and 2.56 (95% CI, 1.15-3.97) (post-intervention). Finally, a subgroup of patients (≥32%) persists with at least a moderate handicap, despite vestibular rehabilitation.

Conclusion

A spectrum of symptoms is associated with UVH, of which chronic dizziness and imbalance are most frequently reported. However, semi-structured interviews should be conducted to define the whole spectrum of UVH symptoms more precisely, in order to establish a validated patient-reported outcome measure (PROM) for UVH patients. Furthermore, vestibular interventions can significantly decrease self-reported handicap, although this is insufficient for a subgroup of patients. It could therefore be considered for this subgroup of patients to explore new intervention strategies like vibrotactile feedback or the vestibular implant.

Systematic review registration

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42023389185].

Hearing Outcomes Following Endolymphatic Duct Blockage Surgery and Factors Associated with Improved Audition at Two Years Follow-Up

Objective: To evaluate hearing outcomes at 2 years post endolymphatic duct blockage (EDB) surgery, with an analysis of factors that may predict hearing improvement. Study Design: Retrospective comparative study. Setting: Tertiary care center. Subjects: Definite Ménière's Disease (MD) patients undergoing EDB for refractory disease. Methods: Chart review was conducted to assign cases to one of the three hearing outcome groups (deteriorated, stable, and improved). All cases that met our inclusion criteria were selected. Preoperative data collected were audiograms, bithermal caloric tests, preoperative vertigo episodes, history of previous ear surgery for Ménière, intratympanic steroid injections (ITS) and intraoperative endolymphatic sac (ELS) tear or opening. Postoperative data collected at 24 months were audiograms, vertigo episodes and bithermal caloric testing. Results: Preoperative vertigo episodes, caloric paresis and history of surgery, ITS injections or ELS integrity, as well as postoperative vertigo class distribution and caloric paresis changes were not different between our groups. Preoperative word recognition score (WRS) was lowest in the improved hearing group (p = 0.032). The persistence of tinnitus at 2 years postoperatively was associated with deteriorated hearing (p = 0.033). Conclusions: There are no strong predictors of hearing improvement on presentation pre-EDB, but low preoperative WRS may be the best estimator available. Therefore, ablative interventions should be considered very carefully in patients presenting with low WRS, as they may benefit more from EDB; there is a fair chance of a good hearing outcome with EDB surgery. Persistence of tinnitus can reflect deteriorating audition. Vertigo control and hearing preservation are independent outcomes of EDB surgery, making it desirable as an early intervention for refractory MD cases.

Comparing Intratympanic Gentamicin with Methylprednisolone in Meniere's Disease with Non-Serviceable Hearing

Abstract

To compare the effectiveness of high dose fixed alternate day intratympanic gentamicin with methylprednisolone in the treatment of patients with unilateral, intractable Meniere's disease with poor hearing. Randomized single blind prospective parallel group trial in a tertiary referral centre. Twenty-two patients with definite unilateral Meniere's disease with average pure tone thresholds worse than 50 dB in the affected ear were enrolled. Eleven patients were treated with intratympanic buffered gentamicin and the other eleven were administered intratympanic methylprednisolone (both 4 injections, 40 mg/ml, on alternate days). Patients were assessed pre-intervention, 3 months post intervention and subsequently followed up for 2-4 years. Both groups of patients had significant control of vertigo, DHI scores and THI scores after treatment while the functional scores in the methylprednisolone group was not better than the pre- treatment scores in the long-term follow-up. 9 of 11(82%) patients in gentamicin group and 3 of 11(27%) patients in the methylprednisolone group achieved Class A vertigo control. The gentamicin group had better post intervention DHI scores (p = 0.016, 3 months and p = 0.046, long term) and Functional score (p = 0.014, 3 months and p = 0.05, long term). The hearing in both groups and THI scores, post intervention was similar between both groups. In patients with unilateral intractable MD with non-serviceable hearing, high fixed doses of both intratympanic gentamicin and methylprednisolone are effective in alleviating disease symptoms in long term follow-up. However, intratympanic gentamicin resulted in better control of vertigo, total DHI score and functional level scores than intratympanic methylprednisolone with no significant difference in hearing levels.

Trail Registration Number

Clinical Trials Registry of India (CTRI- REF/2016/10/012363).

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.

On-Demand and Low Dose Intratympanic Gentamicin for Meniere's Disease: A Customized Approach

OBJECTIVE

To evaluate the efficacy of on demand and low dose intratympanic gentamicin (ITG) in patients with intractable Meniere's disease (MD).

STUDY DESIGN

Clinical chart review.

SETTING

Secondary care center.

PATIENTS

Subjects with MD who failed conventional treatment and underwent on demand ITG infiltration from June 2013 to December 2018.

INTERVENTION

0.4 to 0.5 ml of buffered gentamicin were administered through an intratympanic route. A total of 5 mg in case of low dose and 20 mg as a standard dose.

MAIN OUTCOME MEASURES

Vertigo control, Meniere's Disease Functional Level Scale (MDFLS), Dizziness Handicap Inventory (DHI), and pure tone audiometry pre and posttreatment.

RESULTS

Thirty-one patients, 16 women and 15 men with a mean age of 52.81 (22-79) years were included. The number of ITG injections ranged from 1 to 7, with a mean of 2.52 applications per patient. Mean interval between doses was 212.15 (21-1442) days. Average follow-up was 24.03 months. An improvement on MDFLS was seen on 77.4% (n = 24) patients. DHI score improved after gentamicin treatment (mean 55.23 versus 24.06, p ≤ 0.001). Thirty patients (96.8%) reached complete or substantial vertigo control. Only one patient did not achieve control. Hearing was preserved in 43.5% (n = 10) of analyzed audiograms, whereas 17.4% (n = 4) developed hearing loss greater than 20 dB, which was not statistically significant (p = 0.099).

CONCLUSIONS

In our study, on demand and low dose ITG was effective for vertigo control in patients with intractable MD. Individualized therapy is recommended in all patients to minimize vestibular and cochlear toxicity.

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.

Low Concentration Intra-Tympanic Gentamicin Treatment for Menière's Disease: A Long-Term Follow Up

BACKGROUND

Intra-tympanic injections of gentamicin (ITG), a known ototoxic agent, have been proven to be effective in controlling Menière's disease (MD) symptoms, in patients who did not respond to conservative therapy, although its safety was questionable.

OBJECTIVES

To study whether low-concentration ITG, in refractory MD, had an effect on the ipsilateral hearing, in comparison to the contralateral ear, and to study the effectiveness of such treatment.

METHODS

A comparative, retrospective cohort study was conducted between 2003 and 2015, and compared the change in the hearing level between the injected ear and the contralateral, untreated ear.

OUTCOMES

In 20 of 27 patients (74.1%), one course of ITG treatment was considered as successful. In the short-term, there was improvement of hearing level at 1000 Hz (p = 0.014), and deterioration of hearing level at 8000 Hz (p = 0.039), both in comparison to the control ear. In the long-term and after confounders adjustment, we found there were no differences in the hearing levels between the treated ear and the untreated contralateral ear.

CONCLUSIONS

A high success rates of treating vertigo attacks with low concentration ITG in refractory unilateral MD patients is herein reported, while a significant difference was not observed in the hearing threshold compared with the healthy contralateral ear.

Intratympanic Gentamicin for Intractable Ménière's Disease - A Review and Analysis of Audiovestibular Impact

Introduction  Intratympanic gentamicin regulates the symptoms in most patients with incapacitating Ménière's disease. The treatment protocols have changed over the years from medical labyrinthectomy to preservation of vestibular function.

Objectives  This study aims to review the audiovestibular response related to the effect of the drug in controlling vertigo.

Data Synthesis  Articles were identified by means of a search in the PubMed database using the key words Meniere and intratympanic or transtympanic gentamicin . Total 144 articles were reviewed after excluding those that were technical reports, those based on experimental animal studies, those that focused on outcomes other than vertigo (tinnitus or aural fullness), those with delivery methods other than tympanic membrane injection, and those with bilateral cases. If there was more than one article by the same author(s) or institution, only the most recent one matching the aforementioned criteria and those that were not overlapping were included.

Conclusion  Titration methods or multiple injections on a daily basis can be preferred if the patients have profound or non-serviceable hearing, since these methods have significant incidence of hearing loss. Treatment protocols with a frequency of injection not shorter than once a week, or those with injections on a monthly basis as “needed” provide the same level of vertigo control with better preservation of hearing. Caloric testing is not an ideal tool to analyze the correlation between vertigo control and the effect of gentamicin as compared with gain asymmetry of the vestibulo-ocular reflex. Vestibular-evoked myogenic potentials and the head thrust test are more reliable than other vestibular tests for the follow-up of patients undergoing gentamicin treatment.

Physiologic effects on the vestibular system in Meniere's disease

Ménière syndrome is an inner ear disorder characterized by spontaneous attacks of vertigo, fluctuating low-frequency sensorineural hearing loss, aural fullness and tinnitus. When the syndrome is idiopathic and cannot be attributed to any other cause (eg, syphilis, immune-mediated inner ear disease, surgical trauma), it is referred to as Ménière disease. This article reviews the physiologic effects of Ménière disease on vestibular function, as measured by caloric, head impulse, and vestibular-evoked myogenic potential testing.

High-dose intratympanic gentamicin instillations for treatment of Meniere's disease: long-term results

CONCLUSIONS

Administration of high-dose gentamicin for intractable Meniere's disease appears to be effective in achieving long-term control of vertigo. However, the safety of this route of administration with respect to the patient's hearing has not yet been sufficiently established.

OBJECTIVES

The study aimed to analyze the long-term results of patients receiving high-dose intratympanic gentamicin (ITG) instillation for refractory Meniere's disease.

PATIENTS AND METHODS

Fourteen patients with Meniere's disease according to 1995 American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guidelines who had failed medical (12 subjects) or surgical (2 subjects) treatment were included. Intratympanic injections of 27 mg/ml gentamicin were performed three times daily for 4 days. Vertigo control, the patients' functional level, and their hearing threshold were all analyzed. Criteria described in 1995 by AAO-HNS were used.

RESULTS

The overall successful vertigo control rate was 92.9% over the 2-year follow-up and 85.7% at long-term follow-up (average 10 years). Hearing level as pure-tone average was worse in four patients (28.5%) after 2 years follow-up and in six patients (42.8%) after long-term follow-up, respectively. Profound sensorineural hearing loss occurred as a result of gentamicin injection in one patient (7%).

Otoneurological management of petrous apex cholesterol granuloma

OBJECTIVE

The aim of the study is to review the management of petrous apex cholesterol granuloma. The surgical approaches for drainage or total removal and the wait and see policy were analyzed, and outcomes were evaluated.

METHODS

Retrospective charts of 27 patients managed for petrous apex cholesterol granuloma with a minimum follow-up of 12 months were analyzed in a quartenary skull base center. Presenting symptoms and signs were recorded, and radiologic imaging was evaluated. Management options included wait and see policy and surgery by several approaches.

RESULTS

The mean age of patients affected by the lesion was 38.8 years. The mean follow-up was 56.7 months. Patients complained of hearing loss, vertigo, tinnitus, diplopia, hemifacial spasm, trigeminal neuralgia, and facial paresthesia. Twelve patients were managed by wait and see policy, and in this category, only one lesion showed growth during the follow-up. Depending upon size and location, 15 patients were surgically treated by infralabyrinthine approach (9 patients), infratemporal type B approach (3 patients), combined infratemporal type B transotic approach (2 patients), and transotic approach (1 patient). One recurrence was recorded during the follow-up.

CONCLUSIONS

Radiologic evaluation is required for diagnosis and management. Patients with good hearing can be treated by infralabyrinthine approach. Infratemporal fossa type B approach is advocated in patients with extensive disease and internal carotid artery involvement. Wait and see policy is recommended for asymptomatic cases. Drainage and permanent ventilation are the goals of treatment. Complete removal is indicated in selected cases where placement of drainage tube is not feasible.

Contemporary Role of Endolymphatic Mastoid Shunt Surgery in the Era of Transtympanic Perfusion Strategies

Objectives:

Although there exist undisputed methods to permanently silence the aberrant end organ, controversy surrounds the durable efficacy of non-ablative interventions. This study provides a contemporary review of our institution's clinical experience in performing endolymphatic mastoid shunt surgery (EMSS) in patients with medically refractory endolymphatic hydrops, or Meniere's disease.

Methods:

Between 1984 and 2002, 1,612 patients were referred to our institution with a diagnosis of Meniere's disease. Of these referrals, 1,172 patients met the criteria for Meniere's disease. Although 553 patients responded to medical management, 486 patients underwent EMSS and 133 patients had refractory disease that required chemical or surgical obliterative interventions. The retrospective study utilizes data collected on 226 patients who were followed for a minimum of 5 years.

Results:

Overall, 78% patients responded favorably to EMSS, according to the functional level scale and class categories delineated by the American Academy of Otolaryngology-Head and Neck Surgery 1995 guidelines for control of vertigo. According to the Arenberg anatomic classification for endolymphatic sac location, EMSS achieved adequate control of vertigo in 86% of type I cases, 90% of type II cases, and 82% of type III cases.

Conclusions:

Endolymphatic mastoid shunt surgery is a relatively safe, effective procedure for the long-term control of vertigo in patients with medically refractory Meniere's disease.

Comparisons of cochleotoxicity among three gentamicin compounds following intratympanic application

CONCLUSION

Among the three main gentamicin (GM) compounds following intratympanic application, the cochleotoxicity of C2 was the most severe, whereas that of C1a was the weakest. Understanding of the different cochleotoxicity characteristics of each compound may be of use in future custom-made intratympanic therapy for Ménière's disease.

OBJECTIVE

To investigate differences in cochleotoxicity among three major GM compounds following intratympanic application.

MATERIALS AND METHODS

Three GM compounds (C1, C2, and C1a) were isolated. Sprague-Dawley rats were treated every 2 days for 2 weeks with intratympanic application of saline, GM complex, C1, C2, and C1a. The cochleotoxicity of each compound was assessed by measuring auditory brainstem response (ABR) and through morphological analyses using scanning electron microscopy.

RESULTS

The ABR threshold of the C2 group was found to be more impaired than those of the other groups. The C1a group showed the mildest elevation of the ABR thresholds. Morphological analyses revealed that the proportion of remaining outer hair cells (OHCs) was the lowest in animals treated with C2. Morphologically, the C1 and C1a groups showed the least damage to OHCs.

Effects of a single intratympanic gentamicin injection on Meniere's disease

CONCLUSION

Both single and multiple injections of ITGM were effective in vertigo control and functional improvement. However, the risk of sensorineural hearing loss was much lower for a single injection than for multiple injections.

OBJECTIVES

While intratympanic gentamicin injection (ITGM) has been established as treatment option for intractable Meniere's disease, several injection protocols have been introduced. The risk of sensorineural hearing loss (SNHL) has been reported to be variable for each protocol. Among the protocols, the single injection protocol is an easy to administer, well-tolerated and cost effective technique, as compared with others. We compared the clinical efficacy of ITGM with regard to the vertigo control rate and the incidence of SNHL between two different protocols: the use of single and multiple injections.

MATERIALS AND METHODS

A retrospective review was conducted for 30 subjects who were treated with ITGM with intractable unilateral Meniere's disease from May 1997 through February 2005. The patients were divided into two groups according to the protocol utilized: the multiple injection group (n =10) and the single injection group (n =20). Treatment efficacy was evaluated by using the AAO-HNS Committee on Hearing and Equilibrium guidelines (1995).

RESULTS

Effective vertigo control (Class A and B) were accomplished in 90% of patients in the multiple injection group and in 90% of patients in the single injection group. Functional status was also markedly improved in both groups. However, a significant hearing loss occurred more frequently in the multiple injection group (71%) than in the single injection group (5%). The rate of caloric loss was not different for the two groups (88% for the multiple injection group vs. 85% for the single injection group).

Long-Term follow-up after Gentamicin Application via the Silverstein MicroWick in the Treatment of Ménière's Disease

We conducted a retrospective study to evaluate the long-term effectiveness of gentamicin applied directly to the round window membrane via the Silverstein MicroWick system in patients with definite or probable Ménière's disease. The study population was made up of 69 patients who had received 3 drops of gentamicin 10 mg/ml three times daily; the duration of treatment was guided by objective data obtained from weekly electronystagmography and audiometry. Relief of vertigo was assessed by chart review and telephone interviews. After a minimum follow-up of 24 months, we found that vertiginous symptoms remained controlled in 53 patients (76.8%) after one or more courses of drug therapy. A single course of treatment was successful in 41 patients (59.4%). We conclude that long-term control of vertigo can be achieved in patients with Ménierè's disease by direct application of gentamicin to the round window membrane via the Silverstein MicroWick. This minimally invasive self-treatment technique was well tolerated and free of long-term complications.

Search-coil head-thrust and caloric tests in Ménière's disease

CONCLUSIONS

Our findings suggest that canal function is substantially preserved in subjects with active vertigo attacks as a result of Ménière's disease (MD). In these subjects, the head-thrust test (HTT) may not be as sensitive to canal dysfunction as traditional caloric testing. MD may differentially affect the low-frequency sensitivity of the canals.

OBJECTIVE

Caloric tests have traditionally been used to characterize semicircular canal function in vestibular disorders, including MD. The quantitative HTT provides an objective measurement of semicircular canal function in the frequency and velocity ranges of normal head movements. The aim of this study was to compare the findings of caloric and HTTs in subjects with unilateral MD.

MATERIAL AND METHODS

The study population consisted of 38 candidates for gentamicin treatment due to a high frequency of vertiginous attacks (25 males, 13 females; mean age 52.9 years; range 30-70 years). The duration of symptoms was 1-30 years (mean 5.3 years). Horizontal canal function was characterized with bithermal aqueous caloric tests and recordings of the angular vestibulo-ocular reflexes (aVORs) using the scleral search-coil technique during HTTs. The main outcomes were unilateral weakness (UW) on caloric testing and aVOR gain asymmetry (GA) during HTTs. A caloric response asymmetry of >20% was considered to be indicative of pathologic UW. A difference in GA during HTTs of >5.8% was considered significant.

RESULTS

Twenty subjects (52.6%) showed abnormal results on one or both tests. Pathologic UW was present in 16 subjects (42.1%). During HTTs, 11 subjects (28.9%) showed pathologic GA. Seven subjects (18.4%) showed abnormal results on both tests. A significant correlation was found between UW and GA. However, pathologic GA during HTTs in subjects with unilateral MD was less frequent and the values smaller than those published for vestibular neuritis patients. Two subjects with unilateral MD had 100% UW, but none had >30% asymmetry on HTTs.

Distortion product otoacoustic emissions after intratympanic gentamicin therapy for unilateral Ménière's disease

The treatment of patients with Ménière's disease that do not respond to conventional therapy becomes complicated, particularly when taking into account the issue of hearing damage as well as the control of vertigo. Treatment often involves the intratympanic administration of gentamicin, for which different protocols are used. Hence, it is important that we better understand how this treatment influences hearing, beyond mere audiometric assessments. The aim of this prospective study was to evaluate the effect of intratympanic gentamicin treatment for Ménière's disease on cochlear function, as assessed by otoacoustic emissions. The 41 patients included in the study had been diagnosed with unilateral Ménière's disease as defined by the American Academy of Otolaryngology-Head and Neck Surgery guidelines (1995), and had been refractory to medical treatment for at least 1 year. Intratympanic injections of gentamicin at a concentration of 27 mg/ml were performed at weekly intervals until indications of vestibular hypofunction appeared in the treated ear. Before beginning the treatment and 3 months after ending it, pure tone and speech audiometry tests were performed and the results are expressed in terms of the pure tone average (0.5, 1, 2, and 3 kHz) and the speech discrimination score, respectively. At the same time, a distortion product otoacoustic emission (DPOAE) study was performed and the results are expressed in terms of its presence or absence, and as the amplitude and threshold of the emission. When analyzed 3 months after the treatment had terminated, hearing loss was seen in 13 patients (31.7%). However, no significant change in the threshold and/or amplitude of otoacoustic emissions was observed in any of the patients. Neither were changes in the audiometric stage, number of injections required or the existence of DPOAE before treatment detected. Hence, the treatment method used here for patients with intractable unilateral Ménière's disease can be considered as having a low risk on auditory function, as assessed both audiometrically and with otoacoustic emissions, and can be considered as subablative for hearing function.

Transtympanic perfusion: indications and limitations

PURPOSE OF REVIEW

To review the most recent literature regarding the application of transtympanic inner ear perfusion in the treatment of inner ear disorders including Meniere disease, sudden sensorineural hearing loss, and autoimmune inner ear disease.

RECENT FINDINGS

The use of gentamicin perfusion in the management of Meniere disease with intractable vertigo has been demonstrated to have a very high rate of success, and is much less invasive than alternative surgical procedures such as vestibular nerve section or labyrinthectomy. The technique for achieving the highest rate of success while still minimizing the risk of cochleotoxicity continues to be investigated. Sustained delivery techniques such as the Silverstein MicroWick appear to achieve the best pharmacokinetic profile within the inner ear fluids. The end point of treatment does not necessarily require complete vestibular ablation to cure the patient, and shorter courses of treatment may help to reduce the risk of hearing loss. Cochlear Meniere disease can be treated with dexamethasone 4 mg/cc perfusion of the inner ear, which may improve the hearing, tinnitus, and pressure in the ear. Sudden sensorineural hearing loss has been managed with transtympanic steroid delivery, and this appears to be beneficial for some patients who have failed to respond to oral steroids, or have medical contraindications to systemic steroids.

SUMMARY

Inner ear perfusion via transtympanic delivery is an emerging technique in the management of inner ear disease. Improved results are expected over time as research in this area answers questions about dosage and delivery techniques, as well as identifying new applications and pharmaceuticals.

Efficacy of an ototoxic aminoglycoside (gentamicin) on the differentiation of the inner ear of cichlid fish

Previous investigations revealed that the growth of fish inner ear otoliths depends on the amplitude and the direction of gravity, thus suggesting the existence of a (negative) feedback mechanism. In the course of these experiments, it was shown that altered gravity both affected otolith size (and thus the provision of the proteinacious matrix) as well as the incorporation of calcium. It is hitherto unknown, as of whether sensory hair cells are involved either in the regulation of otolith growth or in the provision of otolithic material (such as protein or inorganic components) or even both. The ototoxic aminoglycoside gentamicin (GM) damages hair cells in many vertebrates (and is therefore used for the treatment of Meniere's disease in humans). The present study was thus designed to determine as of whether vestibular sensory cells are needed for otolith growth by applying GM in order to induce a (functionally relevant) loss of these cells. Developing cichlid fish Oreochromis mossambicus were therefore immersed in 120 mg/l GM for 10 or 21 days. At the beginning and at the end of the experimental periods, the fish were incubated in the calcium-tracer alizarin complexone (AC). After the experiment, otoliths were dissected and the area grown during GM-exposure (i.e., the area enclosed by the two AC labellings) was determined planimetrically. The results showed that incubating the animals in a GM-solution had no effect on otolith growth, but the development of otolith asymmetry was affected. Ultrastructural examinations of the sensory hair cells revealed that they had obviously not been affected by GM-treatment (no degenerative morphological features observed). Overall, the present results suggest that hair cells are not affected by GM concerning their possible role in (general) otolith growth, but that these cells indeed might have transitionally been impaired by GM resulting in a decreased capacity of regulating otolith symmetry.