Dexamethasone pharmacokinetics in the inner ear: comparison of route of administration and use of facilitating agents

Efficacy of Intratympanic Glucocorticoid Steroid Administration Therapy as an Initial Treatment for Idiopathic Sudden Sensorineural Hearing Loss During the COVID-19 Pandemic

OBJECTIVE

Systemic administration of glucocorticoid steroids is the most common initial treatment for idiopathic sudden sensorineural hearing loss (ISSNHL); however, due to the prevalence of coronavirus disease, the indications for this treatment must be carefully determined. The aim of this study was to investigate the efficacy of intratympanic steroid therapy as an initial treatment for idiopathic SSNHL.

METHODS

Sixty-eight patients with idiopathic ISSNHL who were treated with intravenous or intratympanic steroids were included in this study. Patients were retrospectively evaluated regarding preoperative grade, type of additional treatment, outcome of treatment, and side effects of each treatment.

RESULTS

In 46 cases, patients received intravenous steroid therapy as the initial treatment, while 22 patients received intratympanic steroid therapy; 10 patients underwent salvage treatment due to inadequate improvement of symptoms. Regarding additional treatment, intravenous steroid monotherapy was used in 37 patients. The outcomes were similar after both treatments; 16 (43%) and 11 (52%) patients treated exclusively with intravenous and intratympanic steroids, respectively, were completely cured. There were no significant differences in the effects between the 2 treatments, indicating that they were almost equally effective. The side effects observed in patients treated with intravenous steroid therapy were increased blood pressure, acute gastric mucosal disorder, and insomnia. None of these side effects were observed in any of the patients treated with intratympanic steroids; however, 1 case of perforation of the tympanic membrane occurred due to the procedure.

CONCLUSION

There were no significant differences in posttreatment outcomes between patients treated with either intratympanic or intravenous steroids. The therapeutic effects were comparable, and no severe side effects were observed; therefore, intratympanic steroid therapy may be considered useful as an initial treatment for ISSNHL in the context of widespread coronavirus disease.

[Intratympanic Drug Application - Indication and Procedure]

Neurootologic disorders of the inner ear associated with symptoms such as tinnitus, vertigo, and hearing loss are common and often cause significant distress to affected patients. Treatment options are usually limited. There are now some indications for which intratympanic drug application is a possible treatment option. Intratympanic drug administration is a simple, inexpensive therapy option with few side effects that can be used on an outpatient basis. Therefore, it should not be disregarded when indicated.

Intratympanic Dexamethasone Role in Hearing Protection in Cancer Patients

Introduction The study aims to determine the role of intratympanic dexamethasone (ITD) on the hearing profile of patients with head and neck cancer post-chemoradiotherapy. Study design This study employs a prospective case-control design. Subjects and methods In total 834 patients were evaluated for eligibility. Seven hundred and eleven were excluded because they didn't meet the inclusion criteria. A hundred cases out of 123 were diagnosed with head and neck cancer for which the treatment protocol included cisplatin concurrent to radiotherapy recruited. Before each cisplatin treatment session, ITD was injected into one ear (experimental ear) while the other ear of the same patient served as the control. Pure-tone audiometry (PTA) and distortion product otoacoustic emissions (DPOAE) test results of the baseline and follow-up examinations in the sixth and 12th weeks were compared within and between the study and control ears. Results For pure tone thresholds, significant hearing threshold change was noticed at 8 kHz in the experimental group at six weeks and at ≥ 6 kHz in the control group. At 12 weeks, high frequencies were significantly affected at ≥ 4 kHz in the control group. When the baseline was compared across the groups in the 12th week, for otoacoustic emissions, high frequencies showed a loss in the control group more compared to the experimental side (Wilcoxon signed-rank test). Conclusion ITD functions less effectively at higher frequencies because the basal turn of the cochlea is more susceptible to cisplatin ototoxicity. ITD might have potential in the reduction of cisplatin-induced hearing loss.

Enhancement of Trans-Tympanic Drug Delivery by Pharmacological Induction of Inflammation

Drug delivery directly across the tympanic membrane (TM) could eliminate systemic exposure to antibiotics prescribed for otitis media, the most common reason for pediatricians to prescribe antibiotics. Here, we hypothesized that inducing inflammation of the TM could enhance drug flux across the TM. We demonstrated that the flux of ciprofloxacin across the TM was greatly increased by treatment with the proinflammatory agent histamine. That enhancement was blocked by concurrent treatment with blockers of histamine receptor 1. Treatment of the TM with histamine was able to enhance drug flux sufficiently to eradicate otitis media in vivo in chinchillas, but only if the histamine was applied prior to treatment with antibiotics.

Sudden Sensorineural Hearing Loss: A Review

The objective of this review is to present and evaluate the current views on sudden sensorineural hearing loss. Sudden sensorineural hearing loss is an otolaryngology emergency requiring immediate diagnosis and treatment. The etiology of the majority of cases is unknown. The etiology can be classified into various categories such as autoimmune diseases, infections, functional, metabolic disorders, vascular disorders, traumatic causes, due to toxins, and neurological disorders. We searched the U.S. National Library of Medicine's PubMed database using the terms "sudden S.N.H.L.," "virus and ssnhl," and "sudden deafness," as well as the keywords such as "etiology," "COVID 19, and ssnhl," “epidemiology,” “clinical characteristics,” “management,” “therapy,” and “prognosis."

Evaluation of prednisolone and prednisolone sodium succinate concentrations in human plasma and inner ear perilymph during cochlear implantation 24 h after intratympanic injection

BACKGROUND

The use of intratympanic (IT) steroids has drastically increased over the past 10-15 years to manage many otological pathologies.

OBJECTIVES

This study aimed to compare the concentrations of prednisolone and prednisolone sodium succinate (SS) in the plasma and inner ear perilymph of participants who underwent cochlear implantation 24 h after IT injection.

MATERIALS AND METHODS

It was a prospective comparative randomized study. Twenty participants received an IT injection of prednisolone SS ∼24 h before the cochlear implantation. The other five participants received an IT saline injection and represented the control group. Perilymph and blood were sampled during the cochlear implantation surgery.

RESULTS

Both prednisolone and prednisolone SS were still present in perilymph ∼24 h after the IT administration. Only prednisolone was present in the blood plasma of seven participants (35%).

CONCLUSION

IT injection of prednisolone SS resulted in high perilymph concentrations of prednisolone and prednisolone SS, which could stay in the perilymph for at least 24 h. Using a mini-endoscope during the IT injection may effectively detect barriers infront of the round window membrane, increasing the drug concentration in the inner ear.

SIGNIFICANCE

IT injection is an effective method for delivering prednisolone to the inner ear.

Efficacy of transtympanic infusion of dexamethasone into the tympanic cavity in mice with acute sensorineural hearing loss associated with cytomegalovirus infection

BACKGROUND

There is no report on acute sensorineural hearing loss with congenital cytomegalovirus (cCMV) infection in basic experiments.

AIMS/OBJECTIVES

The aim of this study was to evaluate the effect of dexamethasone, an anti-inflammatory steroid, on acute sensorineural hearing loss in the mouse cytomegalovirus (MCMV) infection model mice.

MATERIAL AND METHODS

Sensorineural hearing loss model mice were divided into two groups, one with and one without intratympanic dexamethasone. Dexamethasone was injected into the tympanic cavity of only the right ear, and hearing ability was assessed at the ages of three, six, and eight weeks by auditory brainstem response measurement.

RESULTS

Among the 23 mice intratympanically injected with dexamethasone (15 μg/mouse) at the age of three weeks, five (21.7%) had a hearing improvement of at least 10 dB and 18 (78.3%) had no improvement at the age of six weeks. Among the 19 mice that did not receive a dexamethasone injection, one (5.3%) showed improvement and 18 (94.7%) showed no improvement (p = 0.129).

CONCLUSIONS AND SIGNIFICANCE

In this study, transtympanic infusion of dexamethasone into the tympanic cavity was effective in some mice with sensorineural hearing loss, suggesting that, in addition to angiogenesis, anti-inflammatory activity might be a mechanism of treatment for hearing loss.

Corticosteroids for patients with vestibular neuritis: an evidence synthesis for guidelines for reasonable and appropriate care in the emergency department

BACKGROUND

A short course of corticosteroids is among the management strategies considered by specialists for the treatment of vestibular neuritis (VN). We conducted an umbrella review (systematic review of systematic reviews) to summarize the evidence of corticosteroids use for the treatment of VN.

METHODS

We included systematic reviews of randomized controlled trials (RCTs) and observational studies that evaluated the effects of corticosteroids as compared to placebo or usual care in adult patients with acute VN. Titles, abstracts, and full texts were screened in duplicate. The quality of reviews was assessed with the A MeaSurement Tool to Assess systematic Reviews (AMSTAR-2) tool. The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) assessment was used to rate certainty of evidence. No meta-analysis was performed.

RESULTS

From 149 titles, 5 systematic reviews were selected for quality assessment, and 2 reviews were of higher methodological quality and were included. These 2 reviews included 12 individual studies and 660 patients with VN. In a meta-analysis of 2 RCTs including a total of 50 patients, the use of corticosteroids (as compared to placebo) was associated with higher complete caloric recovery (risk ratio 2.81, 95% CI 1.32 to 6.00, low certainty). It is very uncertain whether this translates into clinical improvement as shown by the imprecise effect estimates for outcomes such as patient-reported vertigo or patient-reported dizziness disability. There was a wide confidence interval for the outcome of dizziness handicap score (1 study, 30 patients, 20.9 points in corticosteroids group vs 15.8 points in placebo, mean difference +5.1, 95% CI -8.09 to +18.29, very low certainty). Higher rates of minor adverse effects for those receiving corticosteroids were reported, but the certainty in this evidence was very low.

CONCLUSIONS

There is limited evidence to support the use of corticosteroids for the treatment of vestibular neuritis in the emergency department.

Comparison of the Pathway to the Inner Ear Between Postauricular and Intramuscular Injection of Dexamethasone in Guinea Pigs

Background

Postauricular injection as a local therapy has been confirmed to be effective for inner ear diseases. However, the mechanism for the drugs entering the inner ears remains unknown. This study aims to compare the distribution of dexamethasone by intramuscular injection with that by postauricular injection, and explore the pathway of the drugs entering the inner ears.

Methods

An in vivo optical imaging system was used to conduct a time course observation to compare the distribution of dexamethasone by intramuscular injection with that by postauricular injection in male guinea pigs. The drug availability in the tympanic mucosa, tympanum, endolymphatic sac, and cochlea was observed by a confocal laser scanning microscope.

Results

The local fluorescent intensity by postauricular injection was significantly higher in the inner ears, and lower in partial peripheral organs, than that by the intramuscular injection. The drug metabolism by postauricular injection exhibited an obviously sustained release effect in the inner ears. Drugs by postauricular injection might enter the endolymphatic sac through the posterior auricular artery and occipital artery, as well as the connections of the mastoid emissary vein, sigmoid sinus and endolymphatic sac.

Conclusion

More drugs concentrated in the inner ear for longer therapeutic time and less systemic delivery implied more effective and less risk of side effects through postauricular injection than intramuscular injection safer for the treatment of inner ear diseases.

In silico Single-Cell Analysis of Steroid-Responsive Gene Targets in the Mammalian Cochlea

Background

Treatment of many types of hearing instability in humans, including sudden sensorineural hearing loss, Meniere's disease, and autoimmune inner ear disease, rely heavily on the utilization of corticosteroids delivered both by oral and transtympanic routes. Despite this use, there is heterogeneity in the response to treatment with corticosteroids in humans with these diseases. The mechanisms by which corticosteroids exert their effect and the cell types in which they exert their effects in the inner ear remain poorly characterized. In this study, we localize steroid-responsive genes to cochlear cell types using previously published transcriptome datasets from the mammalian cochlea.

Methods

Steroid-responsive genes were localized to specific cochlear cell types using existing transcriptome datasets from wild-type mammalian cochlea exposed to systemic and transtympanic steroids, as well as previously published single-cell and single-nucleus RNA-sequencing datasets from the mammalian cochlea. Gene ontology (GO) analysis of differentially expressed genes (DEGs) was performed using PANTHER to investigate cellular processes implicated in transtympanic vs. systemic steroid action in the cochlea.

Results

Steroid-responsive genes were localized to specific cell types and regions in the cochlea including the stria vascularis, organ of Corti, and spiral ganglion neurons (SGN). Analyses demonstrate differential prevalence of steroid-responsive genes. GO analysis demonstrated steroid-responsive DEGs in the SGN to be associated with angiogenesis, apoptosis, and cytokine-mediated anti-inflammatory pathways.

Conclusions

Single-cell and single-nucleus transcriptome datasets localize steroid-responsive genes to specific regions in the cochlea. Further study of these regionally-specific steroid-responsive genes may provide insight into the mechanisms of and clinical response to corticosteroids in diseases of hearing instability.

Effectiveness of Various Treatments for Sudden Sensorineural Hearing Loss-A Retrospective Study

(1) Background: A retrospective clinical study was conducted to compare the effectiveness of different pharmacological and non-pharmacological regimens for treating sudden sensorineural hearing loss (SSNHL). (2) Methods: Adult patients (n = 130) diagnosed with sudden sensorineural hearing loss (SSNHL) and hospitalized between 2015 and 2020 were enrolled in this study. Depending on the treatment regimen applied, patients were divided into five groups. Inclusion criteria were as follows: (i) hearing loss of sudden onset; (ii) hearing loss of at least 30 dB at three consecutive frequencies; (iii) unilateral hearing loss; (iv) age above 18 years. Exclusion criteria were as follows: (i) no follow-up audiogram; (ii) bilateral hearing loss; (iii) recognized alternative diagnosis such as tumor, disorder of inner ear fluids, infection or inflammation, autoimmune disease, malformation, hematological disease, dialysis-dependent renal failure, postdural puncture syndrome, gene-related syndrome, mitochondrial disease; and (iv) age below 18 years. (3) Results: Complete recovery was found in 14% of patients (18/130) and marked improvement was found in 6% (8/130), giving an overall success rate of 20%. The best results were obtained in the second group (i.e., patients given intratympanic glucocorticoid + prolonged orally administered glucocorticoid) where the success rate was 28%. In general, the older the patient, the smaller the improvement in hearing, a correlation that was statistically significant. (4) Conclusions: In treating SSNHL, the highest rate of hearing recovery-28%-was in the group of patients given intratympanic corticoid plus prolonged treatment with orally administered glucocorticoid.

Association Between the Number of Intratympanic Steroid Injections and Hearing Recovery in Sudden Sensorineural Hearing Loss

The frequency of intratympanic (IT) steroid injection varies from once daily to once weekly or less among studies and does not reach a uniform standard. This study investigated the potential association between the number of IT steroid injections and hearing recovery to determine the optimal number in sudden sensorineural hearing loss (SSNHL) patients. A retrospective study involving 233 SSNHL patients receiving IT steroids plus batroxobin within 7 days of onset was performed. Patients were followed up for 3 months. More than 15 dB of HL improvement in the pretreatment pure tone average (PTA) was defined as effective. The effective group had a higher IT injection numbers than the ineffective group (≥ 6 times: 84.6 vs. 61.1, p < 0.001). Regardless of the unadjusted model or adjusted model, patients who received more frequent IT steroid injections seemed more likely to recover hearing (unadjusted model, OR, 95% CI: 1.25, 1.06-1.48; p = 0.007; adjusted model, OR, 95% CI: 1.21, 1.01-1.45; p = 0.044). Six IT injections had the highest rate of hearing recovery (79.1%). In conclusion, IT injection number was an independent factor that was positively associated with hearing recovery, and the optimal number of IT steroid injections was 6. Batroxobin plus higher number of IT steroid injections showed more effective for treating SSNHL.

Promising Applications of Nanoparticles in the Treatment of Hearing Loss

Hearing loss is one of the most common disabilities affecting both children and adults worldwide. However, traditional treatment of hearing loss has some limitations, particularly in terms of drug delivery system as well as diagnosis of ear imaging. The blood–labyrinth barrier (BLB), the barrier between the vasculature and fluids of the inner ear, restricts entry of most blood-borne compounds into inner ear tissues. Nanoparticles (NPs) have been demonstrated to have high biocompatibility, good degradation, and simple synthesis in the process of diagnosis and treatment, which are promising for medical applications in hearing loss. Although previous studies have shown that NPs have promising applications in the field of inner ear diseases, there is still a gap between biological research and clinical application. In this paper, we aim to summarize developments and challenges of NPs in diagnostics and treatment of hearing loss in recent years. This review may be useful to raise otology researchers’ awareness of effect of NPs on hearing diagnosis and treatment.

Junctional Modulation of Round Window Membrane Enhances Dexamethasone Uptake into the Inner Ear and Recovery after NIHL

Delivery of substances into the inner ear via local routes is increasingly being used in clinical treatment. Studies have focused on methods to increase permeability through the round window membrane (RWM) and enhance drug diffusion into the inner ear. However, the clinical applications of those methods have been unclear and few studies have investigated the efficacy of methods in an inner ear injury model. Here, we employed the medium chain fatty acid caprate, a biologically safe, clinically applicable substance, to modulate tight junctions of the RWM. Intratympanic treatment of sodium caprate (SC) induced transient, but wider, gaps in intercellular spaces of the RWM epithelial layer and enhanced the perilymph and cochlear concentrations/uptake of dexamethasone. Importantly, dexamethasone co-administered with SC led to significantly more rapid recovery from noise-induced hearing loss at 4 and 8 kHz, compared with the dexamethasone-only group. Taken together, our data indicate that junctional modulation of the RWM by SC enhances dexamethasone uptake into the inner ear, thereby hastening the recovery of hearing sensitivity after noise trauma.

Comparison of Drug Availability in the Inner Ear After Oral, Transtympanic, and Combined Administration

Although combination of oral and transtympanic drug therapy (CT) has been proved more effective and safer for idiopathic sudden sensorineural hearing loss (ISSNHL) by some clinical trials, there are few laboratory researches on the pharmacokinetics in the inner ear following CT on account of structural limitations of the inner ear. The aim of the present study was to investigate the pharmacokinetic behaviors of CT in the inner ear of mice. Eighteen transgenic GFAP-Luc mice which express luciferase in cochlear spiral ganglion cells were divided into oral administration (OR) group, transtympanic injection route (TT) group and CT group, and luciferin was delivered into the inner ear of these mice through oral, transtympanic or combined routes, respectively. A new in vivo imaging system was used to observe luciferin/luciferase signals and the compare the pharmacokinetics of different administration routes in the inner ear of mice. Bioluminescence signals were observed in the inner ear 3.3 ± 2.6 min after CT, significantly earlier than that of OR group (15.8 ± 7.4 min). CT owned the longest reaching-peak time and largest area under the curve (AUC) among three groups. Compared to TT, CT had longer biological half-life and higher AUC value, but did not displayed stronger peak value. There were significant differences in the peak values between OR group and TT group and between OR group and CT group. This study suggests that the OR route is less effective than the TT or CT route, and combination of OR and TT can deliver more drugs into the inner ear and confer a longer therapeutic window, but cannot increase drug intensity.

The Efficacy of Intratympanic Steroid Injection in Tinnitus Cases Unresponsive to Medical Treatment

OBJECTIVES

To examine the efficacy of an intratympanic steroid injection in tinnitus cases unresponsive to medical treatment.

MATERIALS AND METHODS

The study was carried out at the Ear, Nose, and Throat Department with 107 patients (46 male, 61 female) between the ages of 20 and 77 with a mean of 42.8 years who had idiopathic tinnitus. Patients were randomized by simple randomization to receive intratympanic dexamethasone or isotonic solution. The patients received six intratympanic injections, two per week for three weeks. Tinnitus handicap index (THI) was performed before treatment and at first week, first month, and six months after the completion of the study protocol. The audiometric tests were performed six months after the treatment.

RESULT

In the study group, pretreatment THI and post-treatment first month THI scores and pretreatment THI and post-treatment sixth month THI scores were significantly different whereas the same scores were not significantly different in the control group. The comparison of THI scores between the groups revealed significantly lower scores in the first and sixth months for the study group.

CONCLUSION

The effect of the intratympanic injection of dexamethasone on the efficacy of treatment of tinnitus severity was statistically significant.

Effect and Biocompatibility of a Cross-Linked Hyaluronic Acid and Polylactide-co-glycolide Microcapsule Vehicle in Intratympanic Drug Delivery for Treating Acute Acoustic Trauma

The treatment of acute hearing loss is clinically challenging due to the low efficacy of drug delivery into the inner ear. Local intratympanic administration of dexamethasone (D) and insulin-like growth factor 1 (IGF1) has been proposed for treatment, but they do not persist in the middle ear because they are typically delivered in fluid form. We developed a dual-vehicle drug delivery system consisting of cross-linked hyaluronic acid and polylactide-co-glycolide microcapsules. The effect and biocompatibility of the dual vehicle in delivering D and IGF1 were evaluated using an animal model of acute acoustic trauma. The dual vehicle persisted 10.9 times longer (8.7 days) in the middle ear compared with the control (standard-of-care vehicle, 0.8 days). The dual vehicle was able to sustain drug release over up to 1 to 2 months when indocyanine green was loaded as the drug. One-third of the animals experienced an inflammatory adverse reaction. However, it was transient with no sequelae, which was validated by micro CT findings, endoscopic examination, and histological assessment. Hearing restoration after acoustic trauma was satisfactory in both groups, which was further supported by comparable numbers of viable hair cells. Overall, the use of a dual vehicle for intratympanic D and IGF1 delivery may maximize the effect of drug delivery to the target organ because the residence time of the vehicle is prolonged.

Current Strategies to Combat Cisplatin-Induced Ototoxicity

Cisplatin is widely used for the treatment of a number of solid malignant tumors. However, ototoxicity induced by cisplatin is an obstacle to effective treatment of tumors. The basis for this toxicity has not been fully elucidated. It is generally accepted that hearing loss is due to excessive production of reactive oxygen species by cells of the cochlea. In addition, recent data suggest that inflammation may trigger inner ear cell death through endoplasmic reticulum stress, autophagy, and necroptosis, which induce apoptosis. Strategies have been extensively explored by which to prevent, alleviate, and treat cisplatin-induced ototoxicity, which minimize interference with antitumor activity. Of these strategies, none have been approved by the Federal Drug Administration, although several preclinical studies have been promising. This review highlights recent strategies that reduce cisplatin-induced ototoxicity. The focus of this review is to identify candidate agents as novel molecular targets, drug administration routes, delivery systems, and dosage schedules. Animal models of cisplatin ototoxicity are described that have been used to evaluate drug efficacy and side effect prevention. Finally, clinical reports of otoprotection in patients treated with cisplatin are highlighted. For the future, high-quality studies are required to provide reliable data regarding the safety and effectiveness of pharmacological interventions that reduce cisplatin-induced ototoxicity.

Practical aspects of inner ear gene delivery for research and clinical applications

The application of gene therapy is widely expanding in research and continuously improving in preparation for clinical applications. The inner ear is an attractive target for gene therapy for treating environmental and genetic diseases in both the auditory and vestibular systems. With the lack of spontaneous cochlear hair cell replacement, hair cell regeneration in adult mammals is among the most important goals of gene therapy. In addition, correcting gene defects can open up a new era for treating inner ear diseases. The relative isolation and small size of the inner ear dictate local administration routes and carefully calculated small volumes of reagents. In the current review, we will cover effective timing, injection routes and types of vectors for successful gene delivery to specific target cells within the inner ear. Differences between research purposes and clinical applications are also discussed.

Effectiveness of Steroid Treatment for Sudden Sensorineural Hearing Loss: A Meta-analysis of Randomized Controlled Trials

Background:

The best way to administer steroids for sudden sensorineural hearing loss (SSHL) is still unclear. The present study was aimed at estimating the efficacy of steroids by intratympanic, systemic, and combined therapy (CT) routes.

Methods:

A systematic literature search was performed from 1950 to October 2019 for randomized controlled trials comparing the use of intratympanic, systemic, and combined steroid therapy for SSHL. The outcomes of recovery rate and pure tone average (PTA) improvement were assessed by random-effects and fixed-effects meta-analysis.

Results:

A total of 20 articles identified from 7 countries were eligible for analysis. Although no significant difference in recovery rate was observed between intratympanic steroid therapy (IST) and systemic steroid therapy (SST), IST did demonstrate better hearing improvement, as evidenced by a higher PTA than SST. Compared with SST, CT comprising IST and SST had significant recovery rate improvement. Patients treated with CT had a significantly higher PTA than those treated with SST. Through subgroup analysis based on the equivalent dose of prednisone, it was shown that CT led to a significantly higher PTA than SST only in the high-dose CT versus high-dose SST groups and moderate-dose CT versus high-dose SST groups.

Conclusion:

Moderate and high dose of CT could accelerate hearing improvement in SSHL.

Comparison of 2 Different Intratympanic Methylprednisolone Injection Schedules in Combination With Intravenous Dexamethasone for Unilateral Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss is a common otologic disease in clinic. Systemic and intratympanic steroid treatment have been proved to be effective, but the regimens vary from center to center. The purpose of the study is to analyze the effects of the combined application of intravenous dexamethasone and intratympanic methylprednisolone injection in different time strategies for the treatment of unilateral sudden sensorineural hearing loss. A retrospective chart review was performed for the period from March 2016 to June 2018 at our Department of Otorhinolaryngology-Head and Neck Surgery. A total number of 61 patients who met the academy criteria for unilateral sudden hearing loss were included and grouped based on the time to introduce intratympanic methylprednisolone. All the patients received intravenous dexamethasone 10 mg once daily for 5 days, followed 5 mg once daily for the next 7 days. Intratympanic methylprednisolone (40 mg) was injected every other day 4 times into all patients. This regimen was commenced on day 1 in group 1 and on day 6 in group 2. The pre and posttreatment pure-tone audiograms were analyzed. Sixty-one patients met our inclusion criteria. No significant differences were observed between patients' demographics or pretreatment hearing thresholds. In the 3 months posttreatment pure-tone audiogram assessment, the mean hearing threshold improvement were similar between groups with no frequency specificity. The curative rate in both groups were similar and satisfying. Two patients with diabetes mellitus had persistent small perforations. Some patients had other transient discomfort that disappeared before discharge. The different timing of initiation of intratympanic methylprednisolone injection does not significantly affect the outcome of the treatment for sudden sensorineural hearing loss. Thus, we suggest that intratympanic steroid injection should not be applied as a first-line method except for patients who do not respond early to systemic steroid therapy.

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.

[Topical drug administration to the inner ear. Modern state of the problem and development perspectives]

The work assessed modern methods of drug delivery through biological barriers to the lesion, in particular, through the most studied - skin. The main advantages and disadvantages of the existing methods for the topical administration of drugs into the inner ear - intra-imperial and intra-labyrinth delivery are analyzed. A brief review of medicinal substances for topical administration to the inner ear, both widely used (for example, aminoglycosides, steroid drugs) and undergoing clinical trials, is given. An assessment is made of the prospects for the use of transmembrane drug delivery to the inner ear using an electric field, which has a combined electro-creative and iontophoretic effect.

Long Term Outcomes of Intratympanic Dexamethasone in Intractable Unilateral Meniere's Disease

To evaluate the long term effect of Intratympanic dexamethasone in intractable Meniere's disease. 30 patients with refractory Meniere's disease which did not respond to the standard medical management, were treated with Intratympanic dexamethasone injections. Post treatment hearing outcome and dizziness scores were compared with the pretreatment values respectively. The mean dizziness handicap inventory (DHI) score was reduced from 91.58 (range 80-100) to be 31.00 (p = 0.00) at 3 months of treatment. With the successive follow-up periods, the mean DHI scores were reduced to 51.50, 46.6, and 50.90 at the end of, 6, 12, and 24 months (p = 0.04, 0.35, and 0.49 respectively). Again at the end of 24 months, 23.80% of patients were free of vertigo (p = 0.01). No patient had improvement in the hearing (> 10 dB) in any of the follow-up periods and 6.6% demonstrated deterioration in hearing. There were no major intraoperative or postoperative complications detected. Intratympanic injection of steroid is a safe and effective method for treating intractable Meniere's disease. Although short term improvement in the vertigo is well documented, still in 23% of the patients were found to be free of vertigo at even the end of 24 months. There was no significant improvement in hearing noticed, either in short term or in long term.

Early Intratympanic Methylprednisolone in Sudden SNHL: A Frequency-wise Analysis

Sudden sensorineural hearing loss is a dire medical emergency which must be treated at the earliest to get better long term hearing results. Our study aims to determine the efficacy of intratympanic steroid (Methylprednisolone) on auditory outcomes in patients of sudden sensorineural hearing loss and study the relation between time of onset of hearing loss to start of therapy and frequency-wise recovery of hearing loss. A prospective cohort clinical study with 33 patients with sudden hearing loss of 30 dB or more were treated with the intratympanic injection of methylprednisolone and the effect of the drug was observed. In this study, 33 patients with sudden onset (unilateral or bilateral) of hearing loss were treated with intratympanic methylprednisolone. The duration at which the drug was administered and the age of the participants was taken into consideration. Main outcome measures included audiometry results at low, medium and high hearing loss frequencies. The specific frequency at which the hearing improvement took place was tabulated. It was observed that hearing improved significantly if the steroid is injected within the first 4 days of onset (p < 0.05) at all the frequencies. A gain of 15 dB or more was achieved in more than 78% patients after injecting methylprednisolone intratympanically. A statistically significant association was found between recovery rate and frequency of hearing loss with patients showing greater improvement at low hearing loss frequency in comparison to mid and high frequencies (p < 0.05). The drug efficacy does not change with the age of the patient.

Advances and Challenges in Pharmaceutical Therapies to Prevent and Repair Cochlear Injuries From Noise

Noise induces a broad spectrum of pathological injuries to the cochlea, reflecting both mechanical damage to the delicate architecture of the structures of the organ of Corti and metabolic damage within the organ of Corti and lateral wall tissues. Unlike ototoxic medications, the blood-labyrinth barrier does not offer protection against noise injury. The blood-labyrinth barrier is a target of noise injury, and can be weakened as part of the metabolic pathologies in the cochlea. However, it also offers a potential for therapeutic intervention with oto-protective compounds. Because the blood-labyrinth barrier is weakened by noise, penetration of blood-borne oto-protective compounds could be higher. However, systemic dosing for cochlear protection from noise offers other significant challenges. An alternative option to systemic dosing is local administration to the cochlea through the round window membrane using a variety of drug delivery techniques. The review will discuss noise-induced cochlear pathology, including alterations to the blood-labyrinth barrier, and then transition into discussing approaches for delivery of oto-protective compounds to reduce cochlear injury from noise.

Efficacy of intratympanic corticosteroid, intravenous batroxobin and combined treatment for sudden sensorineural hearing loss with type-2 diabetes

BACKGROUND

Intratympanic corticosteroid (IC), intravenous batroxobin (IB) as the treatment for sudden sensorineural hearing loss (SSNHL) has been reported. However, the data on combination therapy (CT) was scarce.

OBJECTIVE

The aim of this retrospective study was to compare the efficacy of IC, IB, and CT in the treatment of SSNHL with diabetes.

MATERIAL AND METHODS

A total of 212 SSNHL patients with diabetes, who were initially treated within 14 days of onset of disease, were divided into three groups by treatment modality. The hearing recovery was evaluated by the results of pure-tone test after completion of treatment. The prognostic factors, including age, severity of initial hearing loss, duration to onset of treatment, and audiometric curve type, were further compared.

RESULTS

There was a significant difference in hearing recovery by the treatment (p < .05). Recovery rates in the CT group were significantly higher in patients with early treatment than with delayed treatment (p = .021). However, duration and recovery rate was not significantly correlated in IC and IB group (p > .05). In patients recieving early treatment, the recovery rate in CT group was significantly higher than that in IC (p = .013) and IB group (p = .029). Regardless of treatment, the recovery rates were higher in patients with flat and ascending audiograms (p < .05).

CONCLUSIONS AND SIGNIFICANCE

Patients receiving combined therapy, especially in the early stage of SSNHL, could achieve significantly superior recovery in the treatment of SSNHL with diabetes, compared with those using IC or IB alone.

Intratympanic Steroid Use for Sudden Sensorineural Hearing Loss: Current Otolaryngology Practice

OBJECTIVE

To investigate the current practice of intratympanic steroid (ITS) injection for sudden sensorineural hearing loss (SSNHL) in the United Kingdom and link the data with data from the United States and continental Europe.

METHODS

A survey of 21 questions was distributed to members of the British Society of Otology using an online survey platform via ENT UK. Data obtained from UK otolaryngologists (n = 171) were integrated with previously published data from other countries, including the United States (n = 63) and continental Europe (n = 908).

RESULTS

In the United Kingdom, 62% of responding otolaryngologists use ITS injection for SSNHL, while 38% do not. Of those using ITS, 59% use it as first-line treatment, either using it in conjunction with oral steroids (51%) or using it as monotherapy (8%). Of those that use ITS, a majority (83%) use it as salvage therapy when primary treatment with systemic steroids has failed, and similar results are found in the continental Europe and US surveys. The most commonly used preparation is dexamethasone. Responses to questions regarding treatment regimes used are enlightening and show considerable variation in the treatment regimes used within and between countries.

CONCLUSIONS

There is a wide variation in practice with regards to ITS for SSNHL hearing loss in the United Kingdom, United States, and continental Europe. In the absence of protocols or definitive guidance from published literature, knowledge of contemporary practice may help guide or encourage reevaluation of clinical practice and will help guide the design of future clinical trials.

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.

Detection of intralabyrinthine abnormalities using post-contrast delayed 3D-FLAIR MRI sequences in patients with acute vestibular syndrome

PURPOSE

3D-FLAIR sequences with delayed acquisition after contrast medium injection have demonstrated new insights into blood-labyrinthine barrier (BLB) abnormalities in various diseases. The aim of this study was to assess the BLB in patients referred with unilateral acute vestibular syndrome (UAVS).

MATERIALS AND METHODS

In this retrospective multicenter imaging study, we performed 3D-FLAIR and steady-state free precession (SSFP) sequences 4 h after contrast medium administration in 26 healthy volunteers and in 30 patients with UAVS. Two radiologists, blinded to the clinical data, independently assessed the asymmetrical enhancement of the labyrinthine structures and the vestibular nerve on 3D-FLAIR sequences, and the signal of the labyrinthine structures on SSFP sequences. Inter-reader agreement tests were performed.

RESULTS

An asymmetrical enhancement of the semicircular canals was observed in 26 out of 30 ears (86.6%, p < 0.001) and never observed in healthy subjects. An asymmetrical enhancement of the vestibular nerve was never observed in either patients or healthy subjects. An asymmetrical enhancement of the cochlea was observed on the 3D-FLAIR sequence in 6 out of 30 ears only in the patients' group (20%, p = 0.03) and always associated with an enhancement of at least one semicircular canal. A low signal on SSFP sequences was observed only in 11 out of 30 symptomatic ears (36.7%, p < 0.001), involving the utricle in 7 ears and the superior semicircular canal in 4 ears.

CONCLUSION

Patients with typical UAVS presented with semicircular canal enhancement on MRI, while an asymmetrical enhancement of the vestibular nerve was not displayed.

TRIAL REGISTRATION

NCT02529475 KEY POINTS: • Patients with typical vestibular neuronitis presented with semicircular canal enhancement on MRI in 87% of cases. • An enhancement of the vestibular nerve was never displayed.

Animal model studies yield translational solutions for cochlear drug delivery

The field of hearing and deafness research is about to enter an era where new cochlear drug delivery methodologies will become more innovative and plentiful. The present report provides a representative review of previous studies where efficacious results have been obtained with animal models, primarily rodents, for protection against acute hearing loss such as acoustic trauma due to noise overexposure, antibiotic use and cancer chemotherapies. These approaches were initiated using systemic injections or oral administrations of otoprotectants. Now, exciting new options for local drug delivery, which opens up the possibilities for utilization of novel otoprotective drugs or compounds that might not be suitable for systemic use, or might interfere with the efficacious actions of chemotherapeutic agents or antibiotics, are being developed. These include interesting use of nanoparticles (with or without magnetic field supplementation), hydrogels, cochlear micropumps, and new transtympanic injectable compounds, sometimes in combination with cochlear implants.

The Effects of Experimental Intratympanic Steroid Administration on Organ of Corti Type 1 Spiral Ganglion

Introduction  It is unclear how effective is the intratympanic (IT) steroid treatment on organ of Corti type 1 spiral ganglion, its optimal dosage and frequency of administration. The effect of dexamethasone on cochlear functions in individuals with a normal hearing ability is also unknown.

Objective  The aim of this study was to evaluate, at the electrophysiological and ultrastructural levels, the effect of IT dexamethasone administration in guinea pigs with normal hearing on organ of Corti type 1 spiral ganglion.

Methods  A total of 20 guinea pigs ( n  = 40 ears) whose hearing was detected to be normal by electrophysiological tests were included in the study and randomly divided into 6 groups. Four groups were considered study groups, while 2 groups were considered control groups. Dexamethasone was administered intratympanically in doses of 2 mg/mL and 4 mg/mL in the guinea pigs in the study groups. The animals in the control groups received physiological saline in equal doses as the study groups. All interventions were performed under general anesthesia, and the electrophysiological tests were repeated following the IT injections.

Results  No statistically significant differences were found among the groups when the IT injections were evaluated in terms of the electrophysiological measurements ( p  > 0.05). The ultrastructural evaluation showed a cellular mitochondrial increase in the spiral ganglions of the cochlea in the groups in which dexamethasone was administered in a dose of 4 mg/mL.

Conclusion  According to the findings of this study, it can be suggested that the IT injection of dexamethasone is safe, and when applied in a dose of 4 mg/mL, it increases metabolic activity at the cellular level.

Intratympanic steroid use for idiopathic sudden sensorineural hearing loss: current otolaryngology practice in Germany and Austria

AIMS

The frequency of the use of intratympanic steroids (ITS) as a treatment for idiopathic sudden sensorineural hearing loss (ISSNHL) in Europe is still unknown and remains a contentious issue amongst otolaryngologists. We undertook a survey of otolaryngologists in Germany and Austria to establish if there is any professional consensus with which to form a protocol for its use.

METHODS

A survey of 21 questions was distributed electronically to otolaryngologists in Germany and Austria and data on demographics, indications for intratympanic treatment, procedure, follow-up, and outcomes were analysed.

RESULTS

We received 908 responses. 49.1% of otolaryngologists used ITS for ISSNHL. Of those otolaryngologists who use ITS, 73.7% do not use it as primary treatment. 20.6% use ITS in conjunction with oral steroids for primary treatment and only 5.8% use ITS as monotherapy for primary treatment. 90.5% use ITS as salvage therapy. 81.1% do not consider the use of ITS after 2 weeks from the onset of symptoms. 8.3% used a tympanostomy tube and while the most commonly used steroid was dexamethasone at a concentration of 4 mg/ml (61%), a wide variety or other steroids and concentrations were used.

CONCLUSIONS

This survey illustrates wide variation of current practice of intratympanic corticosteroid injection for ISSHL in Germany and Austria. In the absence of high-level evidence, knowing what current practice is allows clinicians to assess what they do against what their colleagues are doing, and if they do something very different, make them question their practice. Moreover, the obtained data will help to direct future clinical trials with the aim to compare the outcomes of more commonly used protocols.

Pharmacokinetics of sodium thiosulfate in Guinea pig perilymph following middle ear application

Hypothesis

To determine the pharmacokinetics of sodium thiosulfate in the inner ear perilymph following middle ear application in Guinea pigs.

Background

Cisplatin chemotherapy is often associated with a dose-dependent high frequency sensorineural hearing loss. Sodium thiosulfate has been shown to reduce cisplatin-induced ototoxicity when given intravenously, but this may limit the tumoricidal effects of the chemotherapy. Recent animal studies looking at middle ear application of sodium thiosulfate have shown prevention of outer hair cell and hearing loss, but the perilymph pharmacokinetics have not yet been established.

Methods

Twenty Guinea pig ears were split into two groups and administered sodium thiosulfate to the middle ear at either a concentration of 250 mg/mL or 50 mg/mL for 30 min. Perilymph samples were then obtained serially through the round window over 6 h. Sodium thiosulfate concentrations were obtained using high-pressure liquid chromatography.

Results

The 250 mg/mL group had a maximum perilymph concentration of 7.27 mg/mL (±0.83) that decreased to 0.94 mg/mL (±0.03) over 6 h. The 50 mg/mL group had an initial concentration of 1.63 mg/mL (±0.17) and was undetectable after 1 h. The half-life of sodium thiosulfate within perilymph was 0.74 h.

Conclusions

and Relevance: The results of this study show that sodium thiosulfate is capable of diffusing through round window and into the inner ear perilymph. Peak levels decline over several hours after exposure. This has a potential application as a localized therapy in the prevention of cisplatin induced ototoxicity.

Advances in nano-based inner ear delivery systems for the treatment of sensorineural hearing loss

Sensorineural hearing loss (SNHL) is one of the most common diseases, accounting for about 90% of all hearing loss. Leading causes of SNHL include advanced age, ototoxic medications, noise exposure, inherited and autoimmune disorders. Most of SNHL is irreversible and managed with hearing aids or cochlear implants. Although there is increased understanding of the molecular pathophysiology of SNHL, biologic treatment options are limited due to lack of noninvasive targeted delivery systems. Obstacles of targeted inner ear delivery include anatomic inaccessibility, biotherapeutic instability, and nonspecific delivery. Advances in nanotechnology may provide a solution to these barriers. Nanoparticles can stabilize and carry biomaterials across the round window membrane into the inner ear, and ligand bioconjugation onto nanoparticle surfaces allows for specific targeting. A newer technology, nanohydrogel, may offer noninvasive and sustained biotherapeutic delivery into specific inner ear cells. Nanohydrogel may be used for inner ear dialysis, a potential treatment for ototoxicity-induced SNHL.

Intratympanic Steroids for Idiopathic Sudden Sensorineural Hearing Loss

Objectives:

We undertook to evaluate the effectiveness of intratympanic (IT) steroid injections for treating idiopathic sudden sensorineural hearing loss (ISSHL) by performing a retrospective case series study in a private otology practice.

Methods:

A total of 21 eligible patients with ISSHL were included. We defined ISSHL as a hearing loss of 20 dB or more at at least 3 consecutive audiometric frequencies that develops within 72 hours or less and cannot be attributed to any commonly identifiable cause of sudden hearing loss. Three IT injections of 0.4 mL of 62.5 mg/mL methylprednisolone solution were administered 1 week apart. The end point for the study was a clinically significant change in audiometric values, with a positive response determined to be a 10-dB or greater improvement in the 4-tone pure tone average and/or a 15% or greater improvement in the word discrimination score. Audiometric data were recorded just before therapy and 1 week after the last IT treatment. The potentially confounding variables recorded included age, sex, “prompt treatment” (defined as treatment within 14 days from onset), concurrent or prior treatment with oral steroids, and severity of hearing loss.

Results:

The overall response rate to the IT steroid protocol was 67% (14 of 21 patients), with a 95% confidence interval of 43% to 85%. Backward stepwise logistic regression identified “prompt treatment” as the only variable that significantly affected the outcome. The response rate of the “prompt treatment” cohort was 91% (10 of 11 patients), with a 95% confidence interval of 59% to 100%.

Conclusions:

These findings support the use of IT steroids as an early intervention in the treatment of ISSHL.

Intratympanic Steroid Perfusion for Refractory Sudden Sensorineural Hearing Loss

OBJECTIVE: Patients with sudden sensorineural hearing loss (SSHL) can benefit from systemic steroid therapy. Unfortunately, some patients are not candidates for steroid therapy due to concern over possible complications. Furthermore, not all patients will benefit from steroid administration. This study evaluates the potential benefits and safety of treating patients with SSHL refractory to oral steroids with intratympanic steroid therapy.

METHODS: A retrospective case review was performed on all patients who presented with sudden sensorineural hearing loss refractory to oral steroid therapy during the past year. Seventeen patients were identified. All patients underwent intratympanic steroid administration, via MicroWick placement and/or round window catheter placement.

RESULTS: Nine patients with sudden sensorineural hearing loss showed an improvement with intratympanic steroid therapy, consisting of MicroWick placement with dexamethasone drop (Decadron) administration for 1–2 weeks and/or round window catheter placement with steroid perfusion. Only one of the patients presenting with hearing loss present for greater than 8 weeks benefited from intratympanic therapy. Complications were few and included tympanic membrane perforation, chronic otitis media, dysequilibrium, and dysguesia.

CONCLUSIONS: Intratympanic steroid therapy can be beneficial in treating patients with sudden sensorineural hearing loss refractory to oral steroid use. EBM rating: C.

Evaluation of Super-High-Dose Steroid Therapy for Sudden Sensorineural Hearing Loss

OBJECTIVE: To determine the efficacy of a high-dose steroid regimen for patients with sudden sensorineural hearing loss (SSNHL) and to evaluate the relationship between outcome and initial steroid dose.

STUDY DESIGN AND SETTING: We conducted a retrospective study of 112 patients presenting to Saitama Medical Center. Patients received tapering courses of hydrocortisone (HC) with an initial dose of either 1200 mg or 600 mg.

RESULTS: More than 87% of patients had recovery of hearing. When hearing stabilized, there were no significant differences between the 1200 mg and 600 mg groups in terms of hearing outcome ( P > 0.05). However, at completion of treatment, the 1200 mg group exhibited significantly superior complete recovery rate and improvement rate ( P < 0.05).

CONCLUSION: Application of our treatment protocol of a tapered course of 1200 mg HC significantly and rapidly improves recovery outcomes in patients of SSNHL.

EBM rating: C-4

[Intratympanic injection therapy for therapy refractory acute hearing loss: A safe option for secondary treatment]

BACKGROUND

High-dose corticosteroids are currently recommended for idiopathic sudden sensorineural hearing loss (ISSNHL) treatment. Intratympanic injections (ITI) are of growing importance, especially in cases of therapy resistance. The selection of patients for this procedure in SSNHL has not been adequately examined so far.

STUDY DESIGN

A total of 77 patients with ISSNHL after ineffective systemic pretreatment underwent intratympanic administration of dexamethasone and hyaluronic acid. Improvement after treatment was determined by pure tone audiometry for both ears before and of the treated ear after ITI.

RESULTS

In this study 34 female and 43 male patients with mean age of 57 years showed a pre-ITI hearing loss of 35 dB in the lower frequencies and 69 dB in the higher frequencies. The mean hearing gain was 10 dB and the response rate was 62%. Absolute hearing gain revealed significant improvements at 500 Hz, 1 kHz and 2 kHz. Under inclusion of contralateral thresholds there were hardly any differences up to 4 kHz. In a detailed analysis of responders moderate improvements could be observed even in higher frequencies. Overall, no relevant adverse events occurred.

CONCLUSION

Treatment of ISSNHL resistant to systemic regimens by ITI of steroids provides an option that offers additional prospects of auditory improvement for affected patients. The presented results indicate that these modalities are also valid for patients with pancochlear ISSNHL.

Hyaluronic acid pretreatment for Sendai virus-mediated cochlear gene transfer

Gene therapy with viral vectors is one of the most promising strategies for sensorineural hearing loss. However, safe and effective administration of the viral vector into cochlear tissue is difficult because of the anatomical isolation of the cochlea. We investigated the efficiency and safety of round window membrane (RWM) application of Sendai virus, one of the most promising non-genotoxic vectors, after pretreatment with hyaluronic acid (HA) on the RWM to promote efficient viral translocation into the cochlea. Sendai virus expressing the green fluorescent protein reporter gene was detected throughout cochlear tissues following application combined with HA pretreatment. Quantitative analysis revealed that maximum expression was reached 3 days after treatment. The efficiency of transgene expression was several 100-fold greater with HA pretreatment than that without. Furthermore, unlike the conventional intracochlear delivery methods, this approach did not cause hearing loss. These findings reveal the potential utility of gene therapy with Sendai virus and HA for treatment of sensorineural hearing loss.

A single dose of dexamethasone encapsulated in polyethylene glycol-coated polylactic acid nanoparticles attenuates cisplatin-induced hearing loss following round window membrane administration

This study aimed to investigate the sustained drug release properties and hearing protection effect of polyethylene glycol-coated polylactic acid (PEG-PLA) stealth nanoparticles loaded with dexamethasone (DEX). DEX was fabricated into PEG-PLA nanoparticles using an emulsion and evaporation technique, as previously reported. The DEX-loaded PEG-PLA nanoparticles (DEX-NPs) had a hydrodynamic diameter of 130±4.78 nm, and a zeta potential of −26.13±3.28 mV. The in vitro release of DEX from DEX-NPs lasted 24 days in phosphate buffered saline (pH 7.4), 5 days in artificial perilymph (pH 7.4), and 1 day in rat plasma. Coumarin 6-labeled NPs placed onto the round window membrane (RWM) of guinea pigs penetrated RWM quickly and accumulated to the organs of Corti, stria vascularis, and spiral ganglion cells after 1 hour of administration. The DEX-NPs locally applied onto the RWM of guinea pigs by a single-dose administration continuously released DEX in 48 hours, which was significantly longer than the free DEX that was cleared out within 12 hours after administration at the same dose. Further functional studies showed that locally administrated single-dose DEX-NPs effectively preserved outer hair cells in guinea pigs after cisplatin insult and thus significantly attenuated hearing loss at 4 kHz and 8 kHz frequencies when compared to the control of free DEX formulation. Histological analyses indicated that the administration of DEX-NPs did not induce local inflammatory responses. Therefore, prolonged delivery of DEX by PEG-PLA nanoparticles through local RWM diffusion (administration) significantly protected the hair cells and auditory function in guinea pigs from cisplatin toxicity, as determined at both histological and functional levels, suggesting the potential therapeutic benefits in clinical applications.

Systemic effects of intratympanic dexamethasone therapy

OBJECTIVE

The study aimed to assess the possible systemic effects of intratympanic dexamethasone (IT-Dex) on the hypothalamic-pituitary-adrenal (HPA) axis, inflammation, and bone metabolism.

DESIGN

A prospective cohort study including 30 adult patients of a tertiary referral ENT clinic treated with 9.6 mg IT-Dex over a period of 10 days was carried out.

METHODS

Effects on plasma and salivary cortisol concentrations (basal and after low-dose (1 μg) ACTH stimulation), peripheral white blood cell count, and biomarkers for bone turnover were measured before (day 0) and after IT-Dex (day 16). Additional measurements for bone turnover were performed 5 months after therapy. Clinical information and medication with possible dexamethasone interaction were recorded.

RESULTS

IT-Dex was well tolerated, and no effect was detected on the HPA axis (stimulated plasma and salivary cortisol concentration on day 0: 758±184 and 44.5±22.0 nmol/l; day 16: 718±154 and 39.8±12.4 nmol/l; P=0.58 and 0.24 respectively). Concentrations of osteocalcin (OC) and bone-specific alkaline phosphatase (BSAP) did not differ after dexamethasone (OC on days 0 and 16 respectively: 24.1±10.5 and 23.6±8.8 μg/l; BSAP on day 0, 16, and after 5 months respectively: 11.5±4.2, 10.3±3.4, and 12.6±5.06 μg/l); similarly, there was no difference in the peripheral white blood cell count (5.7×10(12)/l and 6.1×10(12)/l on days 0 and 16 respectively).

CONCLUSIONS

IT-Dex therapy did not interfere with endogenous cortisol secretion or bone metabolism.

In vitro and in vivo evaluation of a hydrogel reservoir as a continuous drug delivery system for inner ear treatment

Fibrous tissue growth and loss of residual hearing after cochlear implantation can be reduced by application of the glucocorticoid dexamethasone-21-phosphate-disodium-salt (DEX). To date, sustained delivery of this agent to the cochlea using a number of pharmaceutical technologies has not been entirely successful. In this study we examine a novel way of continuous local drug application into the inner ear using a refillable hydrogel functionalized silicone reservoir. A PEG-based hydrogel made of reactive NCO-sP(EO-stat-PO) prepolymers was evaluated as a drug conveying and delivery system in vitro and in vivo. Encapsulating the free form hydrogel into a silicone tube with a small opening for the drug diffusion resulted in delayed drug release but unaffected diffusion of DEX through the gel compared to the free form hydrogel. Additionally, controlled DEX release over several weeks could be demonstrated using the hydrogel filled reservoir. Using a guinea-pig cochlear trauma model the reservoir delivery of DEX significantly protected residual hearing and reduced fibrosis. As well as being used as a device in its own right or in combination with cochlear implants, the hydrogel-filled reservoir represents a new drug delivery system that feasibly could be replenished with therapeutic agents to provide sustained treatment of the inner ear.

Prevention of Cisplatin-Induced Hearing Loss by Intratympanic Dexamethasone

Objective

To examine the role of intratympanic Dexamethasone (ITD) in the prevention of Cisplatin-induced hearing loss.

Study Design

Prospective randomized controlled clinical trial.

Setting

Tertiary referral center.

Subjects and Methods

Twenty-six patients suffering from a neoplastic disease for which the treatment protocol included Cisplatin were recruited. Prior to each Cisplatin treatment session ITD was injected to the baseline randomly assigned ear while the other ear of the same patient served as the control. Audiometry and Distortion Product Otoacoustic Emissions (DPOAEs) test results of the baseline and follow-up examinations were compared within and between the study and control ears.

Results

The cumulative dose of Cisplatin was greater than 400 mg for the 15 subjects who completed the study. The pure tone threshold at 8000 Hz and pure tone average threshold at 4000 to 8000 Hz significantly increased in both the study ( P < .005, P < .03, respectively) and control ears ( P < .01, P < .005, respectively). Significant increase in the pure tone threshold for 6000 Hz was observed in the control ( P < .02) but not in the study group. Within the groups comparison also revealed significant decrease in the DPOAE average signal-to-noise ratio (SNR) for the f2 frequencies 7031 ( P < .04) and 8391 Hz ( P < .04) and SNR average for 4000 to 8000 Hz in the control ( P < .04) but not in the study ears.

Conclusions

ITD significantly attenuated hearing loss at 6000 Hz and decreased the outer hair dysfunction in the DPOAE f2 range of 4000 to 8000 Hz. ITD might have potential in the reduction of Cisplatin-induced hearing loss.

Intratympanic dexamethasone on cochlear blood flow in Guinea pigs

To determine the effect of intratympanically delivered dexamethasone on cochlear blood flow. 29 white Hartly guinea pigs were divided into 2 groups. By laser Doppler flowmeter, baseline data were recorded in the first 15-20 min, followed by 20 min' recording after applying dexamethasone or normal saline, with a record of flow every 5 min in 2 groups. Friedman Test was used to test the change of blood flow in these four timing. There were no significant changes of blood flow after injecting dexamethasone (p = .18 > .05) and normal saline (p = .93 > .05). The effects of dexamethasone on cochlear blood flow were variable and not significant. The following research would be designed under pathological conditions, such as cochlear ischemia, to show the possible mechanism of dexamethasone for specific inner ear disease.

LEVEL OF EVIDENCE

3a (SR of case-control studies).

Dexamethasone uptake in the murine organ of Corti with transtympanic versus systemic administration

Objective

To investigate glucocorticoid uptake in auditory hair cells following transtympanic versus systemic administration of dexamethasone.

Study design

Controlled experimental study.

Setting

Translational science experimental laboratory.

Methods

Swiss-Webster mice were injected with dexamethasone via transtympanic or systemic administration. At 1, 6, or 12 hours post-injection the temporal bones were harvested. After cryosectioning, immunohistochemical staining was performed using an antibody for dexamethasone.

Results

Dexamethasone labelling was greatest at 1 hour. Inner hair cells demonstrated much higher steroid uptake than outer hair cells. Both transtympanic injection and high-dose systemic administration resulted in strong dexamethasone labelling of hair cells, and a decreasing basal-to-apical gradient of hair cell fluorescence intensity was observed. Systemically delivered dexamethasone was rapidly eliminated from the inner ear, demonstrating mild labelling after 6 hours and none after 12 hours. In contrast, the mice receiving transtympanic injection had persistent moderate intensity fluorescence at 6 and 12 hours post-injection.

Conclusion

There is similar uptake of dexamethasone by auditory hair cells after transtympanic and high-dose systemic delivery. Novel findings include the presence of a decreasing basal-apical gradient of steroid uptake, and demonstration of greater affinity of inner hair cells for dexamethasone compared to outer hair cells. In this animal model transtympanic injection resulted in prolonged steroid uptake. These findings help further our understanding of the pharmacokinetics of steroids in the cochlea, with a focus on auditory hair cells.

Novel in vivo imaging analysis of an inner ear drug delivery system in mice: comparison of inner ear drug concentrations over time after transtympanic and systemic injections

Objective

Systemic steroid injections are used to treat idiopathic sudden-onset sensorineural hearing loss (ISSHL) and some inner ear disorders. Recent studies show that transtympanic (TT) steroid injections are effective for treating ISSHL. As in vivo monitoring of drug delivery dynamics for inner ear is lacking, its time course and dispersion of drugs is unknown. Here, we used a new in vivo imaging system to monitor drug delivery in live mice and to compare drug concentrations over time after TT and systemic injections.

Methods

Luciferin delivered into the inner ears of GFAP-Luc transgenic mice reacted with luciferase in GFAP-expressing cells in the cochlear spiral ganglion, resulting in photon bioluminescence. We used the Xenogen IVIS® imaging system to measure how long photons continued to be emitted in the inner ear after TT or systemic injections of luciferin, and then compared the associated drug dynamics.

Results

The response to TT and IP injections differed significantly. Photons were detected five minutes after TT injection, peaking at ∼20 minutes. By contrast, photons were first detected 30 minutes after i.p. injection. TT and i.p. drug delivery time differed considerably. With TT injections, photons were detected earlier than with IP injections. Photon bioluminescence also disappeared sooner. Delivery time varied with TT injections.

Conclusions

We speculate that the drug might enter the Eustachian tube from the middle ear. We conclude that inner-ear drug concentration can be maintained longer if the two injection routes are combined. As the size of luciferin differs from that of therapeutics like dexamethasone, combining drugs with luciferin may advance our understanding of in vivo drug delivery dynamics in the inner ear.

Dexamethasone levels and base-to-apex concentration gradients in the scala tympani perilymph after intracochlear delivery in the guinea pig

HYPOTHESIS

To determine whether intracochlearly applied dexamethasone will lead to better control of drug levels, higher peak concentrations, and lower base-to-apex concentration gradients in the scala tympani (ST) of the guinea pig than after intratympanic (round window [RW]) application.

BACKGROUND

Local application of drugs to the RW results in substantial variation of intracochlear drug levels and significant base-to-apex concentration gradients in ST.

METHODS

Two microliters of dexamethasone-phosphate (10 mg/ml) were injected into ST either through the RW membrane, which was covered with 1% sodium hyaluronate gel or through a cochleostomy with a fluid tight seal of the micropipette. Perilymph was sequentially sampled from the apex at a single time point for each animal, at 20, 80, or 200 min after the injection ended. Results were mathematically interpreted by means of an established computer model and compared with previous experiments performed by our group with the same experimental techniques but using intratympanic applications.

RESULTS

Single intracochlear injections of 20 minutes resulted in approximately 10 times higher peak concentrations (on average) than 2 to 3 hours of intratympanic application to the RW niche. Intracochlear drug levels were less variable and could be measured for over 220 minutes. Concentration gradients along the scala tympani were less pronounced. The remaining variability in intracochlear drug levels was attributable to perilymph and drug leak from the injection site.

CONCLUSION

With significantly higher, less variable drug levels and smaller base-to-apex concentration gradients, intracochlear applications have advantages to intratympanic injections. For further development of this technique, it is of importance to control leaks of perilymph and drug from the injection site and to evaluate its clinical feasibility and associated risks.

Perilymph pharmacokinetics of markers and dexamethasone applied and sampled at the lateral semi-circular canal

Perilymph pharmacokinetics was investigated by a novel approach, in which solutions containing drug or marker were injected from a pipette sealed into the perilymphatic space of the lateral semi-circular canal (LSCC). The cochlear aqueduct provides the outlet for fluid flow so this procedure allows almost the entire perilymph to be exchanged. After wait times of up to 4 h the injection pipette was removed and multiple, sequential samples of perilymph were collected from the LSCC. Fluid efflux at this site results from cerebrospinal fluid (CSF) entry into the basal turn of scala tympani (ST) so the samples allow drug levels from different locations in the ear to be defined. This method allows the rate of elimination of substances from the inner ear to be determined more reliably than with other delivery methods in which drug may only be applied to part of the ear. Results were compared for the markers trimethylphenylammonium (TMPA) and fluorescein and for the drug dexamethasone (Dex). For each substance, the concentration in fluid samples showed a progressive decrease as the delay time between injection and sampling was increased. This is consistent with the elimination of substance from the ear with time. The decline with time was slowest for fluorescein, was fastest for Dex, with TMPA at an intermediate rate. Simulations of the experiments showed that elimination occurred more rapidly from scala tympani (ST) than from scala vestibuli (SV). Calculated elimination half-times from ST averaged 54.1, 24.5 and 22.5 min for fluorescein, TMPA and Dex respectively and from SV 1730, 229 and 111 min respectively. The elimination of Dex from ST occurred considerably faster than previously appreciated. These pharmacokinetic parameters provide an important foundation for understanding of drug treatments of the inner ear.

Gadolinium distribution in cochlear perilymph: differences between intratympanic and intravenous gadolinium injection

INTRODUCTION

Three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) imaging 24 h after intratympanic gadolinium injection (IT method) or 4 h after intravenous injection (IV method) has been used to visualize endolymphatic hydrops in Ménière's disease. The aims of this study were to evaluate the difference in gadolinium distribution in cochlear perilymph between the two methods by comparing the enhancement of the basal and apical turns and clarify the pharmacokinetics in cochlear perilymph.

METHODS

A total of 24 ears of 22 patients who underwent the IT method (gadolinium-diethylene-triamine pentaacetic acid was diluted eightfold with saline) and 28 ears of 17 patients who underwent the IV method (double dose of gadoteridol (0.5 mmol/ml); 0.2 mmol/kg body weight in total amount) at 3 T was analyzed retrospectively. Regions of interest of the perilymph of the cochlear basal turn (B), of the apical turn (A), and the medulla oblongata (M) were determined on each patient. The signal intensity ratios between B and M (BMR), A and M (AMR), and A and B (ABR) were subsequently evaluated.

RESULTS

The IT-BMR (2.63 ± 1.22) was higher than the IV-BMR (1.46 ± 0.45) (p < 0.001). There was no significant difference between the IT- (1.46 ± 0.76) and IV-AMRs (1.21 ± 0.48) (p = 0.15). The IT-ABR (0.58 ± 0.17) was lower than the IV-ABR (0.84 ± 0.22) (p < 0.001).

CONCLUSION

Gadolinium was predominantly distributed in the basal turn compared with the apical turn in the IT method, whereas it was more uniformly distributed in the IV method. These characteristics might reflect the distribution of therapeutic medications administered either intratympanically or systemically.