Gentamicin tympanoclysis: effects on the labyrinthine sensory cells

Preliminary Results of a New Experimental Model for Intratympanic Treatment

OBJECTIVE

Corticosteroids have been applied via transtympanic route for a long time to treat the inner ear disorders. A few animal models were used to answer the questions, "How much drug goes into the inner ear?" and "How far does the drug reach through the scala tympani and/or scala vestibuli?" However, the cerebrospinal fluid contamination poses a major problem. The aims of this study were to create a new sampling model showing the dexamethasone distribution in the inner ear and to provide more reliable data about drug concentrations.

METHODS

Ten Hartley strain albino guinea pigs that weighted between 400 and 600 g were used. After dexamethasone application to the left ear, they were sacrificed at two time points: after 0.5 hours (Exp 1) and after 2 hours (Exp 2). The temporal bones were immediately dissected and put into liquid nitrogen for freezing. The apex, second turn, and basal turns of the cochlea and vestibule were separated, while the bone was in the frozen state. The samples were prepared and measured with ultraviolet (UV) spectroscopy.

RESULTS

The total amount of dexamethasone was statistically higher in the left ear than the control ear. Although the basal turn and vestibule were the most prominent parts, there was no statistical difference between the different parts of the inner ear at 0.5 hours. The vestibule and the apex showed the highest level of dexamethasone at 2 hours.

CONCLUSION

Although the model has some limitations, it can measure dexamethasone concentrations and show the time variability in the inner ear.

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.

Transtympanic Gentamicin and Fibrin Tissue Adhesive for Treatment of Unilateral Menière's Disease: Effects on Vestibular Function

OBJECTIVE: To determine the effects of transtympanic injections, with a mixture composed of gentamicin and fibrin tissue adhesive (FTA), on vestibular function of patients with intractable unilateral Menière's disease.

STUDY DESIGN: This was an open, prospective study.

SETTING AND PATIENTS: The study was performed at 2 tertiary referral centers. Twenty-six patients affected by “definite” unilateral Menière's disease, unresponsive to medical therapy for at least 6 months, were enrolled.

INTERVENTION: A buffered gentamicin solution mixed with FTA was injected in the middle ear until the development of bedside vestibular hypofunction signs and/or caloric weakness in the treated ear.

MAIN OUTCOME MEASURE: Vestibular function was evaluated by 3 bedside vestibular tests (observation of spontaneous nystagmus, head shaking test, and head thrust test) and by a caloric test. Tests were performed on days 10 and 30 after completion of treatment. Tests were also performed 3, 6, and 12 months from completion of the gentamicin-FTA protocol. The effects of treatment were also assessed in terms of hearing levels, control of vertigo, and disability status.

RESULTS: In 22 of the 26 patients, only 1 gentamicin-FTA injection was necessary to obtain 1 or more signs indicating a reduction of the vestibular function in the treated ear. Four patients needed another treatment because of the persistence of their incapacitating symptoms during the follow-up. Four patients needed more than 1 injection to obtain a vestibular hypofunction. None of the patients who received 1 or 2 injections presented hearing loss in direct temporal relationship to the treatment.

CONCLUSIONS: A mixture of gentamicin and fibrin glue makes it possible to considerably reduce the number of administrations in patients with intractable unilateral Menière's disease. Spontaneous nystagmus, post head shaking nystagmus, and a head thrust sign are the clinical signs that indicate onset or progression of unilateral vestibular hypofunction. These signs were obtained with only 1 injection in 81% of patients.

EBM RATING: C

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

BACKGROUND

Gentamicin is used as a therapeutic agent for Ménière's disease because of its vestibulotoxicity causing chemo-ablation of the vestibular sensory epithelia. Its use has increased in recent years. However, there is still no consensus about the dose regimen of gentamicin in the treatment of Ménière's disease. In this study two different dose regimen treatment protocols are compared in a placebo controlled study design. The primary objective is to quantify the treatment effect on dizziness, the secondary objective is hearing evaluation.

METHODS

We performed a randomized, double-blind, placebo-controlled study in adults with unilateral Ménière's disease according to the AAO-HNS guidelines resistant to conservative medication. Three groups received four injections, administered weekly (four intratympanic injections with 40 mg/mL gentamicin solution, two injections gentamicin solution and two injections of placebo in random order, or four injections with placebo). Outcome measures were the score on the Dizziness Handicap Inventory and pure tone audiometry (PTA). Intended follow-up was 2 years.

RESULTS

During follow-up one patient exceeded the accepted amount of hearing loss. Further, enrollment was very slow (until 12 months between two patients) and new insights showed an apparent benefit of intratympanic gentamicin treatment (ITG). Therefore we performed an unscheduled interim analysis which showed that PTA threshold shifts reached the stopping criteria in two more patients. Because of this, this study was ended. Of the three patients with the significant PTA threshold shift two were enrolled in the gentamicin group.

CONCLUSION

No conclusions can be drawn concerning doses regimens. Now that new publications have shown that ITG treatment can be an effective and safe treatment, a placebo-controlled randomized controlled trial may not pass the ethical committee because of these recent reports in literature. Still, a dose regimen study (without placebo) on ITG treatment needs to be performed.

TRIAL REGISTRATION

This trial was registered in The University Medical Center Utrecht/ Gelre hospital Apeldoorn. Protocol ID: 07/343, EudraCT number 2006-005913-37.

Balance dysfunction resulting from acute inner ear energy failure is caused primarily by vestibular hair cell damage

Inner ear energy failure is associated with disorders such as inner ear ischemia. Recently, we used the mitochondrial toxin 3-nitropropionic acid (3-NP) to establish an animal model of inner ear energy failure that presents with auditory dysfunction. Here we investigated the mechanisms underlying balance disorders in the 3-NP animal model. Spontaneous nystagmus peaked 6 hr after treatment with either 300 mM or 500 mM 3-NP. The nystagmus attenuated gradually and disappeared 3 days after 3-NP treatment. A caloric test using ice water was performed to evaluate residual vestibular function 7 days after 3-NP treatment. The response to caloric stimulation was reduced to approximately 40% of the response of the untreated ear following 300 mM 3-NP and was undetectable following 500 mM 3-NP. Structural changes in the peripheral vestibular organs were analyzed by light and electron microscopy. Severe loss of stereocilia was observed following 500 mM 3-NP, whereas disorganized and mildly reduced stereocilia were observed following 300 mM 3-NP. There was severe loss and degeneration of vestibular hair cells following 500 mM 3-NP but only slight loss and degeneration of hair cells following 300 mM 3-NP. These results indicate that acute inner ear energy failure causes balance dysfunction mainly by damaging hair cells in the vestibule, which is distinct from the mechanism underlying auditory disorders.

Intratympanic gentamicin treatment of patients with Ménière's disease with normal hearing

Objective: Understand the safety and outcomes of intratympanic gentamicin treatment in patients with Ménière's disease with normal hearing.

Study Design: Case series with chart review.

Setting: Tertiary referral center.

Subjects and Methods: A total of 224 patients with disabling Ménière's disease treated between May 1996 and June 2007 were grouped according to the American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS) 1995 Committee on Hearing and Equilibrium staging guidelines: stage 1 (<25 dB pure-tone average [PTA]); stage 2 through 4 (>25 dB PTA). Patients underwent self-treatment with intratympanic gentamicin (10 mg/mL) three times daily for one to eight weeks. Outcome measures included pre- and post-treatment speech discrimination score (SDS), PTA, electronystagmography, vertigo relief, and statistical analysis utilizing the Pearson χ2 test.

Results: Twenty-two (88%) of 24 patients with stage 1 Ménière's disease showed unchanged or improved SDS. All 24 patients showed a mean PTA loss of 8 dB. Seventeen (71%) patients reported complete or improved vertigo control. One hundred sixteen (59%) of 200 patients with stage 2 through 4 Ménière's disease showed unchanged or improved SDS. All 200 patients showed a mean PTA loss of 11 dB. One hundred forty-eight (74%) patients reported complete or improved vertigo control.

Conclusions: Patients with stage 1 Ménière's disease appear to have similar vertigo control with better hearing preservation than patients with advanced disease when treated with low-dose intratympanic gentamicin (10 mg/mL).

[Multifrequency vestibular study after vestibular neurotomy and chemical labyrinthectomy]

OBJECTIVES

Vestibular neurotomy (VN) and chemical labyrinthectomy (CL) are the two most common techniques of vestibular deafferention to treat patients with intractable vertigo. A long-term evaluation of vestibular function has been performed with a variety of vestibular tests to find out whether there persisted any residual vestibular function after each technique.

METHODS

We called in all patients who have been treated for the last 10 years and have no known vestibular disease in the non treated ear. Low frequencies were analyzed with caloric tests, medium frequencies with the head-shaking test and head-impulse test, and high frequencies with the skull vibration test. The otolithic function was explored with the subjective vertical visual analysis and otolithic myogenic evoked potentials. Nine patients treated with VN and 12 with CL presented to our department. We were thus able to compare VN and CL patients with a group of 10 normal patients and another group of nine patients that had had a translabyrinthine approach for an acoustic neuroma.

RESULTS

We found out that vestibular responses did persist in seven out of nine (78 %) patients after VN and 11 out of 12 (92 %) patients after CL. On the other hand, no vestibular response was detected following resection of vestibular schwannoma through a translabyrinthine approach.

CONCLUSION

We came to the conclusion that the two latter techniques, unlike vestibulocochlear nerve section via the translabyrinthine approach, are only incomplete methods of vestibular deafferention.

Neurotomie vestibulaire vs. labyrinthectomie chimique dans la maladie de Menière invalidante

OBJECTIVE

To evaluate the efficiency on the vertigos and the impact on the audition of the vestibular neurotomy (VN) and the chemical labyrinthectomy (CL) in patients with severe Menière's disease, in order to determine the precise place for each technique in treatment algorithm.

METHOD

Retrospective study of 71 VN (performed between 1986 and 2003) and 35 CL (performed between 1997 and 2003). These two treatments both aim at obtaining a vestibular deafferentation in order to free definitely the patient of vertigo manifestations. Vestibular results have been assessed by caloric tests performed before and 6 months after treatment. Subjective success was evaluated by searching for recurrent attacks of vertigo and by the AAO-HNS (American Academy of Otolaryngology-Head and Neck Society) scale of subjective evaluation of vertigos (follow-up of 6.4 years after VN and 2.4 years after CL). Pure tone audiometry before treatment and then 6 months later was performed. Complications of two types of treatment were recorded and evaluated.

RESULTS

In 90% of the cases after VN and 86% of the cases after CL, caloric tests indicated a strong vestibular hyporeflexy (hypovalence > 90%). Attacks of vertigo reoccurred in 5.6% of the cases when the hyporeflexy was strong and 85.7% of the cases when it was weak. The quality of the vestibular results on vertigo depends on the degree of hypovalence after treatment. An improvement of the AAO-HNS scale have been obtained in 93% of the cases in the NV group and in 81% of the cases in the LC group. Attacks of vertigo were recurrent in 7% of the patients operated on by VN and 11.4% of the patients treated by CL. Mean pure tone auditory thresholds changed from 50.24 dB HL to 55.64 dB HL (p=0.003) in the VN group and from 69.11 dB HL to 74.51 dB HL (p=0.41) in the CL group. Comparison of the variations of the mean pure tone auditory thresholds before treatment and 6 months after the end of the treatment doesn't show any significant difference between the 2 groups (p > 0.05). Impairment of the audition superior to 20 dB HL was observed in 8.5% of the patients of each group. The auditive results are similar in the 2 groups.

CONCLUSION

These two methods of treatment can not be strictly compared due to several bias in this study. Indeed more patients were treated by VN with a longer follow-up and only the patients with a class C or D audition according to the criteria of the AAO-HNS could be treated by CL. The VN provides a better control of the vertigos than the CL which is an efficient method of treatment in invalidating Meniere's disease. In all the cases, the quality of the results on vertigos depends on the degree of hypovalence after treatment. The auditive results are similar. Since the results of the two treatments are similar, the simplicity of CL encourages us to broaden the indications and to modify the place of the VN in the therapeutic algorithm of Menière's disease.

Communication between the perilymphatic scalae and spiral ligament visualized by in vivo MRI

We evaluated the transport of Gadolinium-diethylenetriaminepentaacetate-bismethylamide (Gd-DTPA-BMA) through the round window (RW) membrane into the perilymphatic space with 4.7-T MRI in an animal study and 1.5-T MRI in humans. After administration of Gd-DTPA-BMA onto the intact RW membrane of guinea pig, Gd-DTPA-BMA uptake was observed in the basal turn and part of the second turn within 40 min. The scala tympani, scala vestibuli, the fibrous part of the spiral ligament and semicircular canal all showed uptake of Gd-DTPA-BMA. All turns of the cochlea were filled with Gd within 10 min in the perforated RW membrane administration group and within 30 min in the intravenous administration group. In patients who accepted middle ear injection of Gd-DTPA-BMA, uptake was observed within 2 h in the basal turn and semicircular canal. After 12 h the apex did still not show any uptake. Gd-DTPA-BMA is transported from the RW to the semicircular canal, the scala tympani and scala vestibuli without passing the helicotrema.

Imaging of the guinea pig cochlea following round window gadolinium application

Precise, non-invasive determination of the aetiology and site of pathology of inner ear disorders is difficult. The aim of this study was to describe an alternative method for inner ear visualization, based on local application of the paramagnetic contrast agent gadolinium. Using a 4.7 T MRI scanner, high contrast images of all four cochlear turns were obtained 3.5 h after placing gadolinium on the round window membrane. Gadolinium cleared from the cochlea within 96 h. Auditory brainstem response measurements performed on a separate group of animals showed no significant threshold shifts after the application, indicating that gadolinium is non-toxic to the guinea pig cochlea.