Management of intractable Ménière's disease after intratympanic injection of Gentamicin

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

Objective

This study used a national insurance claims database to analyze trends in procedural management of Meniere's disease.

Study Design

Retrospective cohort analysis.

Setting

Database study using United States inpatient and outpatient insurance claims submitted from January 2003 to December 2021.

Subjects and Methods

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.

Results

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.

Conclusion

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.

Low Dose Intratympanic Gentamicin in Ménière’s Disease

Intratympanic gentamicin has become an accepted standard of care for Ménière's disease. But there still exists controversies regarding the dosing protocol as well as the drug concentration for optimum control of vertigo and hearing preservation. To determine if 20 mg of intratympanic gentamicin administered once a month for a maximum of 2 months can alleviate intractable vertigo caused by definite Ménière's disease with hearing preservation. Once diagnosed with definite Ménière's disease as per AAO-HNS criteria, the patient was given 0.5 ml of 40 mg/ml intratympanic gentamicin. Follow-up was done at 1-month and 6-month post-treatment. If at 1-month review patient continued to have vertigo one more dose of intratympanic gentamicin was administered. Thirty-two patients were included in the study. Seventeen patients (53.1%) received one dose and 15 patients (46.9%) received two doses of intratympanic injection. We achieved an effective vertigo control of 59.4% and complete vertigo control rate of 53.1%. Worsening of symptoms was noted in 1 patient. Hearing was preserved in all patients except for one. Among the patients who attained effective vertigo control, 72.2% had dead labyrinth at 6-month cold caloric status. A single injection of 20 mg intratympanic gentamicin can alleviate intractable vertigo caused by definite Ménière's disease with hearing preservation. Non-responders may be given a second dose after one month. Intratympanic gentamicin is a simple, cheap treatment that can be carried out in an out-patient setting.

Vestibular drop attacks in Ménière's disease: A systematic review and meta-analysis of frequency, correlates and consequences

BACKGROUND

Vestibular drop attacks (VDA), also called Tumarkin otolith crises as a complication of Ménière's disease (MD) were first described in 1936. Nevertheless, a clearer understanding of their prevalence and manifestations is needed.

THE OBJECTIVE

of this review is to determine the frequency, correlates and consequences of VDA in MD.

METHOD

Three databases were searched (i.e., MEDLINE, PubMed and Google Academia). A total of 1,791 references were identified, of which 18 studies were considered eligible. There was a large variation in the definition of VDA used in the studies.

RESULTS

The frequency of VDA in MD leading to a fall to the ground varied from 3 to 19% in 9 hospital-based studies. In studies where a less restrictive definition of VDA included attacks with postural perturbation, tripping and near-to-fall situations was used the prevalence ranged from 50 to 72%. The pooled frequency of VDA leading to fall to the ground was 8% (95% CI 4 to 12%) in hospital-based studies. In these studies, VDA often occurred in severe and advanced MD whereas in cohort studies such connection was not found. Co-morbidity with migraine increased the likelihood of VDA occurrence in MD. In 3 studies syncope was recorded in connection to VDA with falls. In terms of clinical manifestation, audiometry, MRI, vestibular evoked muscle response measures indicated endolymphatic hydrops with involvement of the otolith system. The hearing loss was more pronounced, and balance was worse in MD patients with VDA than in those without. Injury associated with VDA was reported in only one study.

CONCLUSIONS

VDA is a common phenomenon in MD, occurring even in mild MD and complicated with syncope. Some preliminary evidence suggests that VDA may lead to severe injuries.

The Physiologic Role of Corticosteroids in Menière's Disease: An Update on Glucocorticoid-mediated Pathophysiology and Corticosteroid Inner Ear Distribution

: There are multiple treatment options for Ménière's disease (MD), including dietary modifications, aminoglycoside therapy, and surgery. All have limitations, ranging from limited effectiveness to permanent hearing loss. Corticosteroids have long been used to manage MD due to their relative efficacy and tolerability, but the exact mechanism for disease alleviation is uncertain. Until recently, the precise distribution and role that glucocorticoid receptors play in inner ear diseases have remained largely uninvestigated. Several studies propose they influence mechanisms of fluid regulation through ion and water homeostasis. This review will provide an update on the basic science literature describing the activity of endogenous glucocorticoids and exogenous corticosteroids in the inner ear and the relevance to MD, as well as early clinical trial data pertaining to the application of novel technologies for more effective administration of corticosteroids for the treatment of MD.

Contralateral spreading of substances following intratympanic nanoparticle-conjugated gentamicin injection in a rat model

This study was performed to investigate the Eustachian tube as a potential route for contralateral spreading following intratympanic nanoparticle (NP)-conjugated gentamicin injection in a rat model. Sprague–Dawley rats were divided into three groups and substances were injected in the right ear: group 1 (fluorescent magnetic nanoparticles [F-MNPs], n = 4), group 2 (F-MNP-conjugated gentamicin [F-MNP@GM], n = 2), and control group (no injections, n = 2). T2-weighted sequences corresponding to the regions of interest at 1, 2, and 3 h after intratympanic injection were evaluated, along with immunostaining fluorescence of both side cochlea. The heterogeneous signal intensity of F-MNPs and F-MNP@GM on T2-weighted images, observed in the ipsilateral tympanum, was also detected in the contralateral tympanum in 4 out of 6 rats, recapitulating fluorescent nanoparticles in the contralateral cochlear hair cells. Computational simulations demonstrate the contralateral spreading of particles by gravity force following intratympanic injection in a rat model. The diffusion rate of the contralateral spreading relies on the sizes and surface charges of particles. Collectively, the Eustachian tube could be a route for contralateral spreading following intratympanic injection. Caution should be taken when using the contralateral ear as a control study investigating inner-ear drug delivery through the transtympanic approach.

Transmastoid Labyrinthectomy for Menière's Disease: Experience and Outcomes

OBJECTIVE

To characterize presurgical symptoms and treatment history and postoperative course in patients with medically recalcitrant Menière's disease undergoing transmastoid labyrinthectomy in the post-intratympanic gentamicin era.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary academic medical center.

PATIENTS

All patients who underwent transmastoid labyrinthectomy for medically recalcitrant Menière's disease in 2003 to 2019 by the senior author.

INTERVENTIONS

Review of patients' medical records for: preoperative history of drop attacks, gentamicin injections, endolymphatic sac decompression or vestibular neurectomy, preoperative audiograms, length of hospital stay, postoperative complications, and persistent symptoms or challenging recovery.

MAIN OUTCOME MEASURES

Presurgical clinical history and proximal postoperative outcomes.

RESULTS

Seventy-two patients with a mean age of 56.7 (standard deviation [SD] 10.7) were included. All cases were unilateral. Forty-three patients (59.7%) suffered from drop attacks. Sixty-two (86.1%) had failed sufficient symptom control with gentamicin injections. The mean preoperative word recognition score was 36.4% (SD 23.7) versus 95.1% (SD 8.5) in the contralateral ear. The mean pure-tone average (PTA) of the ipsilateral ear before surgery was 65.5 dB (SD 18.0) versus 16.2 (SD 13.5) for the contralateral ear. Mean hospital stay was 2.0 days (SD 0.87 days, range of 1-5 d). Three patients (4.2%) had prolonged postoperative vertigo.

CONCLUSIONS

Transmastoid labyrinthectomy at our center is performed for unilateral Menière's disease, generally when intratympanic gentamicin has failed. A majority of surgical patients suffer from drop attacks preoperatively. Hospital stay is typically brief.

Management of Ménière's Disease: How Does the Coexistence of Vestibular Migraine Affect Outcomes?

OBJECTIVE

To report the incidence of vestibular migraine (VM) in patients with Ménière's disease (MD) and investigate whether management outcomes of MD differ by the association of VM.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary care academic center.

PATIENTS

MD patients (n = 251) with/without VM who were managed for 5 years in a dizziness clinic.

MAIN OUTCOME MEASURES

Influence of VM on management outcomes and hearing at the latest follow-up in stepwise management options.

RESULTS

Incidence of VM was 35% in MD patients. VM was more common in women than men (40 vs. 22%) and in probable MD than definite MD (43 vs. 29%). Bilateral MD was more frequent with coexistence of VM than without VM in definite MD (14 vs. 0%) as well as probable MD (24 vs. 7%). At the latest follow-up, preventive medications were effective in controlling vertigo in most (80%) patients (74%/90% in definite/probable MD). Additional intratympanic steroids were required in 16% (20%/10% in definite/probable MD) and intratympanic gentamicin or surgeries in 9 (6%) patients with intractable MD. The percentage of intractable MD did not differ with coexistence of VM, though definite MD showed a significantly higher percentage of intractable MD than probable MD (6 vs. 0%, respectively, p = 0.002). Worsening hearing was more frequent in definite MD than probable MD (19 vs. 4%), and association of VM did not influence the incidence of worsening hearing.

CONCLUSIONS

Coexistence of VM was about 30 to 40% in definite and probable MD, especially frequent in bilateral MD (77%) and women with probable MD (50%), requiring identification of coexisting VM while managing MD patients. Management outcomes and worsening hearing in MD patients are not dependent on the coexistence of VM, when both are managed.

Change of VOR gain and pure-tone threshold after single low-dose intratympanic gentamicin injection in Meniere's disease

Background: Intratympanic gentamicin injection (ITG) is a well-accepted means to treat intractable Meniere's disease (MD).Aims/Objectives: To investigate change of vestibule-ocular reflex (VOR) gain and pure-tone threshold after low-dose ITG for MD.Methods: Sixteen patients with definite MD who were treated by low-dose ITG were retrospectively reviewed. We defined VOR gain difference as an amount of decreased gain in video head impulse test one month after ITG. Patients were classified into two groups: single injection vs. multiple injections. Multiple injections group was composed of patients with poor vertigo control after initial ITG who required second or third ITG later in follow up period.Results: VOR gain differences of both horizontal and posterior canal plane were higher than those of anterior canal plane. Between two groups, mean VOR gain difference of horizontal canal plane in multiple injections group was lower than that in single injection group. Only two patients showed increased pure-tone threshold more than 10 dB.Conclusion and significance: Our results suggest that ITG appears to cause a differential loss of function across three semicircular canals. Furthermore, if VOR gain difference of horizontal canal is relatively low after initial ITG, patient might have poor vertigo control and be required another ITG.

A comparison of endolymphatic shunt surgery and intratympanic gentamicin for meniere's disease

OBJECTIVE

To report audiovestibular outcomes following endolymphatic shunt surgery (ELS) and intratympanic gentamicin injections (ITG) in patients with Meniere's disease (MD).

STUDY DESIGN

Retrospective matched cohort study METHODS: Patients with MD refractory to medical management between 2004 and 2017 were reviewed: 44 patients underwent ELS and had outcomes available, while 27 patients underwent ITG and had outcomes available. Mean follow-up durations for the ELS and ITG groups were 39.1 and 43.3 months, respectively. Twenty-six patients from the ELS group and 24 patients from the ITG group were then included in a pretreatment hearing- and age-matched analysis. Main outcome measures were successful control of vertigo, pure-tone average (PTA; 0.5, 1, 2 and 4 kHz), word recognition score (WRS), and treatment complications.

RESULTS

A matched analysis showed vertigo control rates of 73.1% in the ELS group and 66.8% in the ITG group, which were not significantly different (P = .760). The change in PTA following treatment was statistically similar between the ELS group (6.2 dB) and ITG group (4.6 dB) (P = .521), while the change in WRS for the ELS group (+3.9 %) was significantly more favorable than the ITG group (-13.6 %) (P = .046). Chronic post-treatment unsteadiness was reported in 25.0% of the ITG group and was not encountered in the ELS group (P = .009).

CONCLUSION

ELS provided successful vertigo control at least as well as ITG with a lower incidence of audiovestibular complications.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:2455-2460, 2020.

Intratympanic Gentamicin Versus Labyrinthectomy: Inner Ear Sensitivity to Gentamicin and Impact on the Contralateral Labyrinth

Objectives.

To investigate the impact of labyrinthectomy and intratympanic (IT) gentamicin injections on the contralateral labyrinth, we also assessed the response of each individual semicircular canal to each IT gentamicin application.

Methods.

We performed a pilot observational study on tertiary, referral, academic settings. Thirteen patients with unilateral vestibular pathology were organized into two groups, group I (seven patients) receiving IT gentamicin and group II undergoing labyrinthectomy (six patients). All patients underwent six-canal video-head-impulse test in predetermined time intervals. Patients receiving gentamicin were additionally tested 3 to 5 days after every sequential injection, until all ipsilateral canals were ablated, to determine the order of response to gentamicin. We recorded the vestibular-ocular reflex gains and the presence of covert/overt saccades for each canal.

Results.

The posttreatment ipsilateral gains were abnormal. No patient from the gentamicin group developed abnormal contralateral responses, while patients undergoing labyrinthectomy had abnormal contralateral responses from at least one canal, even several months posttreatment. Finally, the lateral semicircular canal was the first one to be affected by IT gentamicin followed by the posterior canal: the superior canal was ablated last.

Conclusion.

In our study, labyrinthectomy had an impact on the responses recorded from the contralateral ear, while IT gentamicin ablated the ipsilateral labyrinthine function without affecting the contralateral responses, possibly because of a milder, more gradual impact. We also show for the first time the order that IT gentamicin application affects the semicircular canals, with the lateral being the first to be affected.

CASP9 genotype confers gentamicin susceptibility in intratympanic treatment of intractable vertigo caused by Ménière's disease

BACKGROUND

Ménière's disease (MD) is a disorder of the inner ear, causing episodes of vertigo. Although surgery is reserved for intractable MD, intratympanic gentamicin (ITG) injection has become an alternative for controlling vertigo.

AIMS/OBJECTIVES

To investigate the genetic basis of ITG efficacy.

MATERIAL AND METHODS

We hypothesized that single nucleotide polymorphisms (SNPs) affect outcomes in patients with MD who receive ITG injections. Whole-exome sequencing was used to determine variations in coding regions.

RESULTS

Multivariate analysis revealed two SNPs, rs1052571 in caspase 9 (CASP9; p = .017) and rs3745274 in cytochrome P450 2B6 (p = .053), which were associated with susceptibility to ITG injections. Only the C-allele in the rs1052571 SNP was significantly associated with susceptibility (p = .027; odds ratio: 5.95; 95% confidence interval: 1.26-28.57, by Fisher's exact test).

CONCLUSIONS AND SIGNIFICANCE

Our results elucidated the role of the rs1052571 SNP and provide a genetic perspective on gentamicin efficacy (susceptibility) in treating intractable MD.

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.

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.

The Degeneration of the Vestibular Efferent Neurons After Intratympanic Gentamicin Administration

Intratympanic gentamicin (ITG) has been used to treat refractory Ménière's disease. Disequilibrium after ITG was still a challenge for some patients, and the underlying mechanism is poorly understood. Our previous study demonstrated that gentamicin distributed in the bilateral vestibular efferent neurons (VEN) after ITG; however, does it lead to VEN damage and cause further disequilibrium in patients following ITG? In this study, we observed severe damaged gentamicin-positive neurons of VEN and severe fractured myelin layer plates around neural fibers when viewed under transmission electron microscopy at day 3 after ITG. At day 30, neurons of VEN presented with relatively normal structures. Compared with the control group, the total number of choline acetyltransferase (CHAT) immunolabeling neurons in bilateral VEN showed a significant decrease both at day 3 and day 30. However, there was no significant difference in the total number of CHAT immunolabeling neurons between day 3 and day 30. It indicates that gentamicin is not only retrogradely transported into bilateral VEN, but also results in the degeneration of VEN after ITG. These findings may be related to patients' disequilibrium symptom after ITG. Furthermore, we speculate that VEN may play a role in vestibular compensation.

Translabyrinthine approach to internal auditory meatus: A retrospective study

Background

Ear and the lateral skull base surgery is challenging and yet fascinating for a Neuro-otologist. A thorough knowledge of the complex anatomy is indispensable for the surgeon in order to provide the best possible care.

Methods

The aim of the study was to highlight the present day indications for translabyrinthine approach to IAM from a Neuro-otologist perspective.

Results

There were a total of 7 patients who underwent Translabyrinthine approach at our centre. In the present study we have reported cases of Vestibular Schwannoma, Facial nerve schwannoma, Cholesteatoma involving the IAM, Meniere's disease with refractory vertigo which were managed via translabyrinthine approach. We also encountered, probably the first reported case, tuberculoma of the IAM which was clinical suspected to be vestibular schwannoma.

Conclusion

The article presents different clinical situations where this approach can be suitably utilized and has been dealt with via a retrospective study encountered at our centre.

[The effectiveness of the intra-tympanic administration of methylprednisolone and gentamycin for the treatment of Meniere's disease]

Meniere's disease is an inner ear pathology characterized by periodic fits of systemic dizziness, fluctuating low-frequency sensorineural loss of hearing, stuffiness in the ear and tympanophonia. The objective of the present study was to evaluate the effectiveness of the intra-tympanic administration of methyl prednisolone in the combination with gentamycin used to treat the patients presenting with Meniere's disease. The study included 18 patients at the age varying from 18 to 70 years presenting with this condition. Group 1 was formed to treat the patients with gentamycin, group 2 was comprised of the patients treated with methyl prednisolone. Special emphasis was placed on the recording of dynamics of the parameters of tonal threshold audiometry and cervical evoked vestibular myogenic potentials. The episodes of dizziness were characterized based on the results of comparison of the number of systemic dizziness episodes within the first 6 months after the first injection of methyl prednisolone or gentamycin with the number of such episodes during one month prior to the onset of the treatment. The results were estimated based on the Dizziness Handicap Inventory (DHI scale). It was shown that the patients comprising group 2 experienced a more pronounced reduction in the number of dizziness episodes compared with those in group 1 (91.56 and 69.81% decrease respectively). Moreover, hearing improved by 35% in the patients of group 2, whereas the improvement was altogether absent the patients of group 1. The patients of both groups reported comparable reduction of subjective tympanophonia estimated based on the DHI scale. The results of the comparison were evaluated based on the DHI scale (54.9% in group 2 and 53.8% in group 1).

Recent surgical options for vestibular vertigo

Vertigo is not a well-defined disease but a symptom that can occur in heterogeneous entities diagnosed and treated mainly by otolaryngologists, neurologists, internal medicine, and primary care physicians. Most vertigo syndromes have a good prognosis and management is predominantly conservative, whereas the need for surgical therapy is rare, but for a subset of patients often the only remaining option. In this paper, we describe and discuss different surgical therapy options for hydropic inner ear diseases, Menière's disease, dehiscence syndromes, perilymph fistulas, and benign paroxysmal positional vertigo. At the end, we shortly introduce the most recent developments in regard to vestibular implants. Surgical therapy is still indicated for vestibular disease in selected patients nowadays when conservative options did not reduce symptoms and patients are still suffering. Success depends on the correct diagnosis and choosing among different procedures the ones going along with an adequate patient selection. With regard to the invasiveness and the possible risks due to surgery, in depth individual counseling is absolutely necessary. Ablative and destructive surgical procedures usually achieve a successful vertigo control, but are associated with a high risk for hearing loss. Therefore, residual hearing has to be included in the decision making process for surgical therapy.

Partial Aminoglycoside Lesions in Vestibular Epithelia Reveal Broad Sensory Dysfunction Associated with Modest Hair Cell Loss and Afferent Calyx Retraction

Although the effects of aminoglycoside antibiotics on hair cells have been investigated for decades, their influences on the dendrites of primary afferent neurons have not been widely studied. This is undoubtedly due to the difficulty in disassociating pathology to dendritic processes from that resulting from loss of the presynaptic hair cell. This was overcome in the present investigation through development of a preparation using Chinchilla laniger that enabled direct perilymphatic infusion. Through this strategy we unmasked gentamicin's potential effects on afferent calyces. The pathophysiology of the vestibular neuroepithelia after post-administration durations of 0.5 through 6 months was assessed using single-neuron electrophysiology, immunohistochemistry, and confocal microscopy. Hair cell densities within cristae central zones (0.5-, 1-, 2-, and 6-months) and utricle peri- and extrastriola (6-months) regions were determined, and damage to calretinin-immunoreactive calyces was quantified. Gentamicin-induced hair cell loss exhibited a profile that reflected elimination of a most-sensitive group by 0.5-months post-administration (18.2%), followed by loss of a second group (20.6%) over the subsequent 5.5 months. The total hair cell loss with this gentamicin dose (approximately 38.8%) was less than the estimated fraction of type I hair cells in the chinchilla's crista central zone (approximately 60%), indicating that viable type I hair cells remained. Extensive lesions to afferent calyces were observed at 0.5-months, though stimulus-evoked modulation was intact at this post-administration time. Widespread compromise to calyx morphology and severe attenuation of stimulus-evoked afferent discharge modulation was found at 1 month post-administration, a condition that persisted in preparations examined through the 6-month post-administration interval. Spontaneous discharge was robust at all post-administration intervals. All calretinin-positive calyces had retracted at 2 and 6 months post-administration. We found no evidence of morphologic or physiologic recovery. These results indicate that gentamicin-induced partial lesions to vestibular epithelia include hair cell loss (ostensibly reflecting an apoptotic effect) that is far less extensive than the compromise to stimulus-evoked afferent discharge modulation and retraction of afferent calyces (reflecting non-apoptotic effects). Additionally, calyx retraction cannot be completely accounted for by loss of type I hair cells, supporting the possibility for direct action of gentamicin on the afferent dendrite.

Repeated courses of intratympanic dexamethasone injection are effective for intractable Meniere's disease

CONCLUSION

Intra-tympanic dexamethasone injection (ITD) could serve as a first-line intra-tympanic (IT) treatment for Meniere's disease (MD), regardless of hearing level. Even if the response to initial ITD course was unsatisfactory, a repeated course may be beneficial with some patients.

OBJECTIVES

This study examined the effect of repeated courses of ITD administered on demand and investigated the possibility of ITD as an initial IT treatment for medically intractable MD patients.

METHOD

Fifty-one patients who had been diagnosed with definite MD and given course(s) of ITD treatment were included. Vertigo control, pure tone average and functional disability scores were evaluated against the American Academy of Otolaryngology-Head and Neck Surgery guidelines for MD.

RESULTS

Vertigo disappeared or was substantially controlled in 58.8% and 23.5% of the patients, respectively, after the first ITD course. A repeated course further raised the complete vertigo control rate by 15.7% and intra-tympanic gentamycin injection could be postponed or avoided in 78.6% of the patients who required repeated IT treatment. Hearing was unchanged after the first course of ITD (p > .05). No significant differences were detected in the clinical profiles or laboratory findings between patients receiving single course of ITD and those on multiple courses (p > .05).

Menière's disease

Menière's disease (MD) is a chronic multifactorial disorder of the inner ear characterized by episodic vestibular symptoms associated with sensorineural hearing loss, tinnitus, and aural pressure. Epidemiologic and genomic evidence supports a genetic susceptibility with multiple biochemical pathways involved, including the endocrine system, innate immune response, and autonomic nervous system. Allergens, infectious agents, vascular events, or genetic factors could modify inner-ear homeostasis and trigger MD. The diagnosis of MD is based on clinical criteria and requires the observation of an episodic vertigo syndrome associated with low- to medium-frequency sensorineural hearing loss and fluctuating aural symptoms (hearing loss, tinnitus, and/or fullness) in the affected ear. Headache is also found during the attacks and bilateral involvement is found in 25-40% of cases. Audiologic and vestibular assessment is recommended to monitor the clinical course. The treatment of MD is symptomatic to obtain relief of vestibular episodes and preventive to limit hearing loss progression. Treatment options include sodium restriction, betahistine, intratympanic gentamicin, or steroids and eventually surgery, such as cochlear implantation.