A state-of-the-art analysis of pharmacological delivery and artificial intelligence techniques for inner ear disease treatment

Over the last several decades, both the academic and therapeutic fields have seen significant progress in the delivery of drugs to the inner ear due to recent delivery methods established for the systemic administration of drugs in inner ear treatment. Novel technologies such as nanoparticles and hydrogels are being investigated, in addition to the traditional treatment methods. Intracochlear devices, which utilize current developments in microsystems technology, are on the horizon of inner ear drug delivery methods and are designed to provide medicine directly into the inner ear. These devices are used for stem cell treatment, RNA interference, and the delivery of neurotrophic factors and steroids during cochlear implantation. An in-depth analysis of artificial neural networks (ANNs) in pharmaceutical research may be found in ANNs for Drug Delivery, Design, and Disposition. This prediction tool has a great deal of promise to assist researchers in more successfully designing, developing, and delivering successful medications because of its capacity to learn and self-correct in a very complicated environment. ANN achieved a high level of accuracy exceeding 0.90, along with a sensitivity of 95% and a specificity of 100%, in accurately distinguishing illness. Additionally, the ANN model provided nearly perfect measures of 0.99%. Nanoparticles exhibit potential as a viable therapeutic approach for bacterial infections that are challenging to manage, such as otitis media. The utilization of ANNs has the potential to enhance the effectiveness of nanoparticle therapy, particularly in the realm of automated identification of otitis media. Polymeric nanoparticles have demonstrated effectiveness in the treatment of prevalent bacterial infections in pediatric patients, suggesting significant potential for forthcoming therapeutic interventions. Finally, this study is based on a research of how inner ear diseases have been treated in the last ten years (2012-2022) using machine learning.

Disease-Modifying Antirheumatic Drugs in the Treatment of Autoimmune Inner Ear Disease: A Systematic Review and Meta-Analysis of Auditory and Vestibular Outcomes

OBJECTIVE

To answer the following question: In patients with primary autoimmune inner ear disease (AIED), (population) what impact do disease-modifying antirheumatic agents (DMARDs) (intervention) when compared with no treatment or corticosteroids (comparison) have on auditory and vestibular outcomes (outcome)?

STUDY DESIGN

Systematic review and meta-analysis.

DATA SOURCES

According to PRISMA guidelines, PubMed, Scopus, CINAHL, and Cochrane Library databases were searched from inception to March 10, 2022.

STUDY SELECTION

Studies of patients receiving DMARDs for the treatment of AIED were selected for review. Case reports, phase I/II trials, studies of patients with secondary AIED, and studies of AIED patients receiving solely corticosteroids were excluded.

DATA EXTRACTION

Primary outcomes were pure-tone audiometry and speech discrimination scores at baseline and after DMARD treatment. Secondary outcomes were rates of subjective audiovestibular complaints and rates of adverse reactions. No objective vestibular outcomes underwent meta-analysis.

DATA SYNTHESIS

Mean differences were calculated using RevMan 5.4. Heterogeneity was assessed with the Q test and I2 statistic. Pooled prevalence rates of audiovestibular symptoms were expressed as a percentage with 95% confidence intervals.

RESULTS

Ten studies with a total of 187 patients were included. Treatments included methotrexate, etanercept, azathioprine, anakinra, cyclophosphamide, rituximab, and infliximab. Mean treatment duration was 10.8 ± 22.2 months and mean follow-up was 13.7 ± 8.1 months. The pure-tone audiometry and speech discrimination scores mean differences between baseline and post-DMARD were -2.1 [-4.1, -0.1] dB and 13.9 [8.5, 19.4] %, respectively. Seven studies reported 38 adverse events, four of which were classified as serious.

CONCLUSION

DMARDs showed statistically significant improvement in auditory outcomes, as well as subjective symptoms, with relatively low rates of adverse events. They warrant further exploration to better compare with corticosteroids.

Repurposable Drugs That Interact with Steroid Responsive Gene Targets for Inner Ear Disease

Corticosteroids, oral or transtympanic, remain the mainstay for inner ear diseases characterized by hearing fluctuation or sudden changes in hearing, including sudden sensorineural hearing loss (SSNHL), Meniere's disease (MD), and autoimmune inner ear disease (AIED). Despite their use across these diseases, the rate of complete recovery remains low, and results across the literature demonstrates significant heterogeneity with respect to the effect of corticosteroids, suggesting a need to identify more efficacious treatment options. Previously, our group has cross-referenced steroid-responsive genes in the cochlea with published single-cell and single-nucleus transcriptome datasets to demonstrate that steroid-responsive differentially regulated genes are expressed in spiral ganglion neurons (SGN) and stria vascularis (SV) cell types. These differentially regulated genes represent potential druggable gene targets. We utilized multiple gene target databases (DrugBank, Pharos, and LINCS) to identify orally administered, FDA approved medications that potentially target these genes. We identified 42 candidate drugs that have been shown to interact with these genes, with an emphasis on safety profile, and tolerability. This study utilizes multiple databases to identify drugs that can target a number of druggable genes in otologic disorders that are commonly treated with steroids, providing a basis for establishing novel repurposing treatment trials.

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.

Anatomical basis of drug delivery to the inner ear

The isolated anatomical position and blood-labyrinth barrier hampers systemic drug delivery to the mammalian inner ear. Intratympanic placement of drugs and permeation via the round- and oval window are established methods for local pharmaceutical treatment. Mechanisms of drug uptake and pathways for distribution within the inner ear are hard to predict. The complex microanatomy with fluid-filled spaces separated by tight- and leaky barriers compose various compartments that connect via active and passive transport mechanisms. Here we provide a review on the inner ear architecture at light- and electron microscopy level, relevant for drug delivery. Focus is laid on the human inner ear architecture. Some new data add information on the human inner ear fluid spaces generated with high resolution microcomputed tomography at 15 μm resolution. Perilymphatic spaces are connected with the central modiolus by active transport mechanisms of mesothelial cells that provide access to spiral ganglion neurons. Reports on leaky barriers between scala tympani and the so-called cortilymph compartment likely open the best path for hair cell targeting. The complex barrier system of tight junction proteins such as occludins, claudins and tricellulin isolates the endolymphatic space for most drugs. Comparison of relevant differences of barriers, target cells and cell types involved in drug spread between main animal models and humans shall provide some translational aspects for inner ear drug applications.

Clinical trials for inner ear drugs: Design and execution challenges

The development of therapies for the inner ear presents unique opportunities and challenges. On the one hand, the ear presents an opportunity for localized drug delivery to avoid systemic side effects. However, we do not understand the pathobiology of many common ear disorders clearly enough to develop rational therapeutic solutions. Further, identification of biomarkers beyond conventional audiometry and balance testing to track disease progress and recovery remain elusive. Because of the comparatively low incidence and prevalence of many inner ear disorders, as well as issues with respect to timing of drug delivery for certain diseases, multi-center, multi-investigator collaborative networks are required to promote effective clinical trial design.

Evaluation of a transtympanic delivery system in Mus musculus for extended release steroids

OBJECTIVE

The current investigation evaluated a novel extended release delivery system for treating inner ear diseases. The platform technology consists of a film forming agent (FFA) and microsphere component to localize and extend drug delivery within the ear.

STUDY DESIGN

Studies evaluated dissolution kinetics of microspheres with multiple encapsulates, testing of a variety of FFAs, and ability to localize to the round window membrane in mice in vivo.

SETTING

Studies were completed at Orbis Biosciences and The University of Kansas Medical Center.

SUBJECTS

In conjunction with in vitro characterization, an infrared dye-containing microsphere formulation was evaluated for round window membrane (RWM) localization and general tolerability in C57/BL6 Mus musculus for 35 days.

METHODS

In vitro characterization was performed using upright diffusion cells on cellulose acetate membranes, with drug content quantified by high performance liquid chromatography. Mus musculus dosing of infrared dye-containing microspheres was performed under anesthesia with a 27 GA needle and 2.0 μL injection volume RESULTS: In vitro dissolution demonstrates the ability of the FFA with microsphere platform to release steroids, proteins, peptides, and nucleic acids for at least one month, while necroscopy shows the ability of the FFA with dye-loaded microspheres to remain localized to Mus musculus RWM for the same period of time, with favorable tolerability.

CONCLUSIONS

Combining FFA and microsphere for localized drug delivery may enable cost-effective, extended release local delivery to the inner ear of new and existing small molecules, proteins, peptides, and nucleic acids.

N-Acetylcysteine attenuates tumor necrosis factor alpha levels in autoimmune inner ear disease patients

Autoimmune inner ear disease (AIED) is a poorly understood disease marked by bilateral, rapidly progressive hearing loss triggered by unknown stimuli, which is corticosteroid responsive in 60 % of patients. Although the mechanism of the disease is not precisely understood, a complex interaction of cytokines is believed to contribute toward the inflammatory disease process and hearing loss. Previously, we showed the role of TNF-α in steroid-sensitive and IL-1β in steroid-resistant immune-mediated hearing loss. N-Acetylcysteine (NAC), a broad spectrum antioxidant, has been effective in other autoimmune disorders. Other studies have shown NAC to have a protective adjunct role in human idiopathic sudden hearing loss, where the addition of NAC resulted in better hearing recovery than with steroids alone, although the mechanism of this protection was not elucidated. In the present study, we observed PBMCs from AIED patients exhibited higher baseline TNF-α and MPO levels compared with normal healthy controls. NAC effectively abrogates LPS-mediated TNF-α release from PBMC of both AIED patients and controls. We demonstrated that in AIED patients, the TNF-α downstream signaling pathway appears aberrantly regulated, influencing both MPO and IL-8 expression. Given that NAC effectively abrogated LPS-mediated TNF-α release and exerted minimal effects on the downstream targets of this pathway, we feel NAC may be a rational adjunct therapy for this enigmatic disease, worthy of clinical exploration.

The Effects of Superoxide Dismutase in Gerbils with Bacterial Meningitis

BACKGROUND: Inflammatory products, such as oxygen radicals generated during the course of bacterial meningitis, can damage nerve endings, hair cells, and/or supporting cells in the cochlea. Superoxide dismutase (SOD), an O2-scavenger, has been shown to play an important role in the protection against radical toxicity in various animal experiments.

OBJECTIVE: To study the antioxidant effects of SOD on the inflammatory response of gerbils with bacterial meningitis.

STUDY DESIGN: Meningitis was induced in three groups of 10 gerbils by intrathecal (IT) injection of Streptococcus pneumoniae into the cisterna magna. Group 1 received IT SOD, group 2 received intramuscular (IM) SOD, and group 3, the control group, received IM normal saline. Histologic data and auditory brainstem responses (ABR) were obtained from each gerbil.

RESULTS: Fibrosis and/or neo-ossification were near absent in the IT SOD group and significantly less fibrosis occurred in the IM group (IT vs. IM: P = 0.010; IT vs. control group: P = 0.001). The amount of surviving spiral ganglion cells correlated inversely with the extent of fibrosis (r = −0.753, P < 0.00001).

CONCLUSIONS: IT injection of SOD significantly reduced cochlear fibrosis and neo-ossification, reduced the spiral ganglion cell loss, and decreased damage of the cochlear components following bacterial meningitis.

Direct Round Window Application of Gentamicin with Varying Delivery Vehicles: A Comparison of Ototoxicity

OBJECTIVE: To evaluate patterns of ototoxic damage sustained from gentamicin applied directly to the round window in varying delivery vehicles.

SETTING: The search for a reliable method of drug delivery to the inner ear continues. Vehicles such as Gelfoam, hyaluronic acid, and fibrin may allow for a more reproducible pattern of ototoxic damage.

STUDY DESIGN: Histological evaluation of vestibular and cochlear damage was performed on Mongolian gerbils after a known dosage of gentamicin in different delivery vehicles.

RESULTS: Variable ototoxic damage was caused by Gelfoam and fibrin-based vehicles. No ototoxic damage was found in the Healon vehicle. The vehicle of fibrin and Gelfoam combined resulted in severe damage. There was no evidence of selective cochlear or vestibular ototoxicity in any of the vehicles tested.

CONCLUSIONS AND SIGNIFICANCE: The fibrin/Gelfoam vehicle was the only delivery system to produce reliable damage. Ototoxic damage depended on the vehicle. We found no evidence for selective vestibular ototoxicity with gentamicin.

IL-1β inhibition in autoimmune inner ear disease: can you hear me now?

Clinical vignette: A 51-year-old man with right-sided sudden hearing loss presents to the otology clinic. He has a 4-year history of episodic vertigo of several hours' duration and fluctuating, progressive sensorineural hearing loss in his left ear. The vertigo attacks have not occurred for the last 18 months, and the left ear hearing is consistently poor. The patient's right ear hearing has dropped in the last 36 hours. MRI imaging of brain and temporal bone are normal. A 2-week "burst and taper" of oral prednisone is administered with no effect. Over the next 3 months, serial audiograms show rapidly progressive loss of threshold and word recognition scores on the right side. A trial of high-dose prednisone (60 mg/d for 30 days) results in full recovery of the right ear hearing and substantial improvement in the left ear. As the prednisone dose is slowly tapered over several months, the hearing drops again.

Early efficacy trial of anakinra in corticosteroid-resistant autoimmune inner ear disease

BACKGROUND

Autoimmune inner ear disease (AIED) is a rare disease that results in progressive sensorineural hearing loss. Patients with AIED initially respond to corticosteroids; however, many patients become unresponsive to this treatment over time, and there is no effective alternative therapy for these individuals.

METHODS

We performed a phase I/II open-label, single-arm clinical trial of the IL-1 receptor antagonist anakinra in corticosteroid-resistant AIED patients. Given that the etiology of corticosteroid resistance is likely heterogeneous, we used a Simon 2-stage design to distinguish between an unacceptable (≤10%) and an acceptable (≥30%) response rate to anakinra therapy. Subjects received 100 mg anakinra by subcutaneous injection for 84 days, followed by a 180-day observational period.

RESULTS

Based on patient responses, the Simon 2-stage rule permitted premature termination of the trial after 10 subjects completed the 84-day drug period, as the target efficacy for the entire trial had been achieved. Of these 10 patients, 7 demonstrated audiometric improvement, as assessed by pure tone average (PTA) and word recognition score (WRS). In these 7 responders, reduced IL-1β plasma levels correlated with clinical response. Upon discontinuation of treatment, 3 subjects relapsed, which correlated with increased IL-1β plasma levels.

CONCLUSION

We demonstrated that IL-1β inhibition in corticosteroid-resistant AIED patients was effective in a small cohort of patients and that IL-1β plasma levels associated with both clinical hearing response and disease relapse. These results suggest that a larger phase II randomized clinical trial of IL-1β inhibition is warranted.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01267994.

FUNDING

NIH, Merrill & Phoebe Goodman Otology Research Center, and Long Island Hearing & Speech Society.

Inner ear symptoms and disease: pathophysiological understanding and therapeutic options

In recent years, huge advances have taken place in understanding of inner ear pathophysiology causing sensorineural hearing loss, tinnitus, and vertigo. Advances in understanding comprise biochemical and physiological research of stimulus perception and conduction, inner ear homeostasis, and hereditary diseases with underlying genetics. This review describes and tabulates the various causes of inner ear disease and defines inner ear and non-inner ear causes of hearing loss, tinnitus, and vertigo. The aim of this review was to comprehensively breakdown this field of otorhinolaryngology for specialists and non-specialists and to discuss current therapeutic options in distinct diseases and promising research for future therapies, especially pharmaceutic, genetic, or stem cell therapy.

A regulated delivery system for inner ear drug application

OBJECTIVE

We have recently developed a novel inner ear drug delivery system using chitosan glycerophosphate (CGP) hydrogel loaded with drugs commonly used for treatment of inner ear diseases, significantly improving the drugs' sustained delivery. The goal of this study is to evaluate the effectiveness of chitosanase as a "switch off" mechanism for this drug delivery system when side effects and potential ototoxicities appear during treatment. To evaluate this effect, we tested gentamicin (GENT) in the inner ear following CGP delivery with/without regulation.

METHODS

Purified chitosanase was obtained and used for regulating the CGP delivery system. In vitro studies were performed to evaluate the effect of the interaction between chitosanase and CGP-hydrogel loaded with GENT or Texas Red-labeled GENT (GTTR). In vivo studies were performed using our mouse model to investigate the regulatory effect of chitosanase application on the delivery of GENT to the inner ear. To assess the potential drug rerouting regulatory effect of chitosanase the GTTR fluorescence intensity was evaluated at the round window niche (RWN) and the Eustachian tube (ET). To further characterize this regulatory effect, GENT concentration in the perilymph of the inner ear was analyzed by chromatographic tandem mass spectrometry (LC-MS/MS), and the uptake in the inner ear cells was measured using fluorescence microscopy following CGP delivery with/without chitosanase application.

RESULTS

The chitosanase effectively digested the CGP-hydrogel, quickly releasing GENT and GTTR from the system in vitro. When reacted with GENT alone chitosanase did not produce any reducing sugars and did not affect GENT's antimicrobial activity. In vivo GTTR was effectively rerouted from the RWN to the ET, limiting its uptake in inner ear hair cells. Concurrent with these findings, GENT concentration in the inner ear perilymph was significantly decreased after chitosanase application.

CONCLUSION

Our study findings suggest that, for the first time, sustained and controlled inner ear drug delivery can be successfully regulated enhancing its translation potential for clinical application. The use of chitosanase to digest the CGP-hydrogel results in the rerouting of the loaded drug away from the RWN, effectively downregulating its delivery to the inner ear. This important modification to our drug delivery system has the ability to deliver therapy to the inner ear until desired effect is achieved and to stop this process when side effects or treatment-related ototoxicities start to occur, providing a novel and salient approach for safe and effective delivery to the inner ear.

Microsystems technologies for drug delivery to the inner ear

The inner ear represents one of the most technologically challenging targets for local drug delivery, but its clinical significance is rapidly increasing. The prevalence of sensorineural hearing loss and other auditory diseases, along with balance disorders and tinnitus, has spurred broad efforts to develop therapeutic compounds and regenerative approaches to treat these conditions, necessitating advances in systems capable of targeted and sustained drug delivery. The delicate nature of hearing structures combined with the relative inaccessibility of the cochlea by means of conventional delivery routes together necessitate significant advancements in both the precision and miniaturization of delivery systems, and the nature of the molecular and cellular targets for these therapies suggests that multiple compounds may need to be delivered in a time-sequenced fashion over an extended duration. Here we address the various approaches being developed for inner ear drug delivery, including micropump-based devices, reciprocating systems, and cochlear prosthesis-mediated delivery, concluding with an analysis of emerging challenges and opportunities for the first generation of technologies suitable for human clinical use. These developments represent exciting advances that have the potential to repair and regenerate hearing structures in millions of patients for whom no currently available medical treatments exist, a situation that requires them to function with electronic hearing augmentation devices or to live with severely impaired auditory function. These advances also have the potential for broader clinical applications that share similar requirements and challenges with the inner ear, such as drug delivery to the central nervous system.

Drug-mediated ototoxicity and tinnitus: alleviation with melatonin

This review evaluates the published basic science and clinical reports related to the role of melatonin in reducing the side effects of aminoglycosides and the cancer chemotherapeutic agent cisplatin, in the cochlea and vestibule of the inner ear. A thorough search of the literature was performed using available databases for the purpose of uncovering articles applicable to the current review. Cochlear function was most frequently evaluated by measuring otoacoustic emissions and their distortion products after animals were treated with cytotoxic drugs alone or in combination with melatonin. Vestibular damage due to aminoglycosides was evaluated by estimating hair cell loss in explanted utricles of newborn rats. Tinnitus was assessed in patients who received melatonin using a visual analogue scale or the Tinnitus Handicap Inventory. Compared to a mixture of antioxidants which included tocopherol, ascorbate, glutathione and N-acetyl-cysteine, melatonin, also a documented antioxidant, was estimated to be up to 150 times more effective in limiting the cochlear side effects, evaluated using otoacoustic emission distortion products, of gentamicin, tobramycin and cisplatin. In a dose-response manner, melatonin also reduced vestibular hair cell loss due to gentamicin treatment in explanted utricles of newborn rats. Finally, melatonin (3 mg daily) limited subjective tinnitus in patients. These findings suggest the potential use of melatonin to combat the ototoxicity of aminoglycosides and cancer chemotherapeutic agents. Additional studies at both the experimental and clinical levels should be performed to further document the actions of melatonin at the cochlear and vestibular levels to further clarify the protective mechanisms of action of this ubiquitously-acting molecule. Melatonin's low cost and minimal toxicity profile supports its use to protect the inner ear from drug-mediated damage.

Inner ear drug delivery for auditory applications

Many inner ear disorders cannot be adequately treated by systemic drug delivery. A blood-cochlear barrier exists, similar physiologically to the blood-brain barrier, which limits the concentration and size of molecules able to leave the circulation and gain access to the cells of the inner ear. However, research in novel therapeutics and delivery systems has led to significant progress in the development of local methods of drug delivery to the inner ear. Intratympanic approaches, which deliver therapeutics to the middle ear, rely on permeation through tissue for access to the structures of the inner ear, whereas intracochlear methods are able to directly insert drugs into the inner ear. Innovative drug delivery systems to treat various inner ear ailments such as ototoxicity, sudden sensorineural hearing loss, autoimmune inner ear disease, and for preserving neurons and regenerating sensory cells are being explored.

[A case of herpetic facial paralysis in which cochleovestibular symptoms outweigh facial nerve symptoms]

A 42-year-old man presented with sensorineural hearing loss of acute onset, tinnitus, and vertigo. Physical examination revealed slight asymmetry in facial nerve functions and spontaneous nystagmus. Magnetic resonance imaging of the internal acoustic canal showed contrast enhancement consistent with edema-inflammation, being notable and diffuse in the seventh and eighth cranial nerve complex, and minimal in the cochlea. Non-hydropic cochleovestibular syndrome was considered and the patient was treated with antiviral and corticosteroid medications. A week later, facial paralysis improved and the acute hearing loss reversed. On the twelfth day of presentation, he had no complaints other than mild imbalance on abrupt changes in movement. In this type of herpetic facial paralysis in which cochleovestibular symptoms outweigh facial nerve symptoms, it might be argued that varicella zoster virus reactivation occurs in the spiral and/or vestibular ganglion.

Thioperamide delays vestibular compensation in goldfish

Unilateral lesion of the vestibular system induces posturo-locomotor deficits that are compensated for with time. Drug therapy is currently used to improve the recovery process and to facilitate vestibular compensation. We investigated the effects of thioperamide on functional recovery after unilateral labyrinthectomy in Carassius auratus. Approximately 24h after surgery, the animals were injected intraperitoneally with thioperamide (15 mg/kg) and saline (1.5 ml/kg). The injections were repeated daily for a total of 15 consecutive days. The substances were administered in a volume of 1.5 ml/kg body weight. Another group, which served as a non-lesion control, did not receive unilateral labyrinthectomy or system injections. Animals treated with saline presented a compensatory decrease in body tilt on the 7th day, while the animals treated with thioperamide presented a decrease in body tilt from the 13th day, suggesting a delay in the functional recovery process. These results suggest that an increase in cerebral histamine levels impairs vestibular compensation in goldfish.

Inner ear therapy for neural preservation

A gradual loss of auditory neurons often occurs following sensorineural hearing loss. Since the cochlear implant must stimulate the remaining auditory neuron population, it would be beneficial to preserve as many auditory neurons as possible. Neurotrophic factors protect auditory neurons from degradation after sensorineural hearing loss in experimental animals, but have not yet been translated into the clinical setting. Current experimental and clinical techniques for drug delivery to the inner ear are examined in this review, covering the routes for drug delivery to the cochlea and the delivery systems used to introduce them. Duration of treatment, drug diffusion, effectiveness and safety are discussed with references to how they may be translated to the implementation of neurotrophic factor treatment for neural preservation.

Substance distribution in a cochlea model using different pump rates for cochlear implant drug delivery electrode prototypes

Several studies using animals have shown the protective effects of neurotrophic factors (NF) on spiral ganglion cells (SGC). This is of particular importance since the number of SGCs is considered to be among the factors defining the efficacy of cochlear implants. A device for local inner ear treatment is therefore of great interest. As described previously, we modified a Contour(TM) cochlear implant electrode, to examine the inbuilt canal to be used for fluid release [Paasche, G., Gibson, P., Averbeck, T., Becker, H., Lenarz, T., Stöver, T., 2003. Technical report: modification of a cochlear implant electrode for drug delivery to the inner ear. Otol. Neurotol. 24, 222-227]. In the present study, three different electrode prototypes with openings of the delivery channel at various locations along the electrode array were examined to determine distribution of dye in a cochlea model over time. We compared dye delivery with: (a) release of the dye at the tip, (b) release of the dye at the tip and the side of the electrode, and (c) release of the dye only at the side of the electrode (6 mm from the tip). A mechanical pump was used to drive the system at pump rates of 100, 10, and 1 microl/h. Dye concentration changes along the length of the whole cochlea were investigated. Mean values for all experimental conditions show that the distribution along the array is fastest with two outlets whereas the distribution via a single outlet at the side of the electrode array is not considered to be sufficient. The established experimental setup provides the possibility of investigating prototypes of a fluid based drug delivery system for the treatment of inner ear pathologies in combination with electrical stimulation.

Serial Audiometry in a Clinical Trial of AIED Treatment

OBJECTIVE

We analyzed pure-tone and speech audiometric results from a prospective trial of anti-inflammatory treatment of subjects with active autoimmune inner ear disease (AIED). We sought to characterize the pattern and size of the treatment effect as reflected in clinical audiometry and to identify audiometric predictors of response to steroid treatment of AIED.

SUBJECTS

Adult participants demonstrated clinically established criteria for AIED (n = 116). Eligibility required audiometric evidence of active AIED as indicated by idiopathic sensorineural hearing loss with threshold elevations within 3 months of enrollment.

METHODS

We evaluated audiometric changes after 4 weeks of treatment with pharmacologic doses (60 mg/day) of prednisone. We examined the relationship between audiometric pure-tone thresholds at baseline and changes in word intelligibility score (WIS) using parametric and nonparametric analyses. Magnitudes of change were assessed using independent or paired t-tests. Separate analyses were performed on subgroups that did or did not show improved WIS score with steroid treatment.

RESULTS

Overall mean pure-tone averages improved from baseline to closeout of prednisone treatment in better hearing ears from 52.4 to 48.3 dB (p < .0001). Mean WIS improved in the better ear from 71.4% to 78.1% (p < .0001). Of pure-tone measures, only the six-tone average showed significant correlation with both the absolute improvements in WIS and with the percentage change in WIS after treatment. Individual frequencies at baseline showed no significant relationship with changes in WIS score after treatment. In 69 (59.5%) of 116 subjects, WIS improved (range, 2-80%) in the better ear. In these subjects, the baseline pure-tone thresholds and pure-tone averages correlated significantly and positively with improvement in WIS.

CONCLUSIONS

Steroid treatment in AIED-mediated hearing loss produce variable but significant hearing gains. Neither a focal, cochleotopic region of greatest vulnerability to AIED nor frequency-specific amenability to treatment were evident. We did observe that analysis of predictors and the degree of treatment effect vary with different approaches to measuring change in the WIS. Depending on the approach adopted, the size of the treatment effect may be greatest across intermediate hearing levels at baseline. These observations offer an audiometric database that may enable greater precision in judging clinically meaningful parameters for future studies of AIED treatment and other interventions for sensorineural hearing loss.

Etanercept Treatment for Autoimmune Inner Ear Disease: Results of a Pilot Placebo-Controlled Study

PURPOSE

Autoimmune Inner Ear Disease (AIED) is an idiopathic progressive, often bilateral, sensironeural hearing loss that occurs over weeks to months, generally resulting in significant auditory disability. Response to treatment with immunomodulators other than corticosteroids has been poor. Data from a guinea pig model of AIED and a recent open label trial of etanercept suggested potential treatment benefit. Based on these preliminary results, we conducted a pilot placebo controlled trial of etanercept in AIED patients.

METHODS

Twenty AIED patients were enrolled in a 12-week blinded placebo (PLA) controlled randomized clinical trial of etanercept (ETA) with 25 mg SC twice weekly. Patients received treatment for 8 weeks with a 4-week follow-up off-treatment. The primary study endpoint was an improvement in pure tone threshold (PTA) of 10 Db in two consecutive frequencies and/or improvement in speech discrimination of >12% at week 8.

RESULTS

Patient demographics were similar for the ETA and PLA patients. Seventeen subjects (8 ETA, 9 PLA) completed the trial. The 3 dropouts were due to lack of efficacy. One ETA and 2 PLA subjects achieved the primary endpoint (p > 0.999). One ETA and 1 PLA pt demonstrated improved in hearing loss and vertigo severity by VAS and hearing disability. No safety issues were observed.

CONCLUSION

The results of this pilot trial demonstrate that etanercept 25 mg twice weekly for 8 weeks was no better than placebo for treatment of AIED in this patient population.

Syndrome de Cogan révélé par une diarrhée glairo-sanglante

INTRODUCTION

Cogan's syndrome is defined by the combination of non syphilitic interstitial keratitis and inner ear dysfunction, similar to Meniere's disease.

OBSERVATION

Cogan's syndrome was revealed by haemorrhagic glaireous diarrhoea in a 21 year-old woman whose medical history included Hirschsprung's disease. Cerebral MRI revealed viral-like bilateral neuritis of the eighth cranial nerve, never described in the literature before. The auditory and visual disorders regressed after treatment with corticosteroids.

CONCLUSION

The early diagnosis of Cogan's syndrome permits the cure of the visual and auditory and notably inner ear symptoms with corticosteroid therapy.

Round-window anatomical considerations in intratympanic drug therapy for inner-ear diseases

Our aim was to elucidate the importance of anatomical aspects in planning local therapies for inner-ear diseases. The study undertakes the anatomical evaluation, from a surgical-approach perspective, of the relationship between the false and true round-window membranes. As our design, we chose a human temporal bone dissection study, for which we used 20 fresh temporal bones. After an exploratory tympanotomy and atticotomy, we drilled the anterosuperior (promontory) edge of the round-window niche until the true round-window membrane was completely exposed. We registered the presence or absence and the extent of the false round-window membranes on the round-window niche. We found false round-window membranes obstructing the round-window niche partially or completely in five temporal bones (25%). Complete obstruction was present in one temporal bone (5%). We found mucoperiosteal folds obstructing the round-window niche partially or completely in a significant proportion of the ears. These anatomical particularities could account, at least partially, for the great variability of the results of intratympanic therapies for inner-ear diseases.

Etanercept therapy for immune-mediated cochleovestibular disorders: A multi-center, open-label, pilot study

OBJECTIVE

Immune-mediated cochleovestibular disorders (IMCVDs) continue to present a diagnostic and therapeutic challenge. Antirheumatic agents, commonly employed for IMCVDs, are associated with variable efficacy and sometimes with serious side effects. The objective of the current study was to preliminarily evaluate the efficacy of etanercept therapy for IMCVD.

METHODS

In this open-label prospective pilot study, 23 patients with bilateral IMCVDs or symptoms of bilateral Meniere's disease were treated with etanercept (25 mg twice weekly, by subcutaneous injection) for 24 weeks. All participants showed progressive hearing loss within 3 months prior to the study and responded to prednisone therapy. Hearing improvement was defined as an improvement of sensorineural hearing from baseline, in at least one ear, of 15 dB or more in the pure-tone air conduction thresholds, or an increase of more than 12% in word identification score. When present, vertigo and tinnitus were assessed by frequency and severity of attack and a functional level scale. Limited serial positron emission tomography (PET) of the inner ear region was performed in 5 patients to assess disease activity.

RESULTS

There were 12 female (52%) and 11 male patients with a mean age of 48 years. Hearing improved in 7 (30%) patients, was unchanged in 13 (57%), and worsened in 3 (13%). Of 21 patients with tinnitus, this symptom improved in 7 (33%), was unchanged in 10 (48%), and worsened in 3 (13%). Of 16 patients with vertigo, 8 (50%) were improved, 7 (47%) unchanged, and 1 (3%) worse at the end of the study. Etanercept was generally well tolerated. PET was positive on one ear of 2 of 5 patients, remained positive with treatment on 1 of these, and was initially positive in 1 deaf ear, becoming negative at followup.

CONCLUSION

These prospective pilot data suggest that etanercept therapy is safe among patients with IMCVDs. However, these data do not suggest substantial efficacy of etanercept among patients with IMCVDs in improving hearing loss. There appeared to be stabilization or improvement of hearing in 87% in this group of patients with pretreatment intractable progressive hearing loss. However, the study endpoint of improvement in 70% of patients was not attained. This short-term effect of possible stabilization requires further study. PET scanning was not useful as a tool to evaluate hearing loss in a limited subset of patients.

Effects of Chlorpheniramine and L-histidine on vestibular compensation in goldfish, Carassius auratus

Histamine is thought to be involved in the recovery of vestibular function after damage to the vestibular receptors of the inner ear. This study evaluated the effects of post-operative treatment using Chlorpheniramine (H1 histamine antagonist) and L-histidine, (a histaminergic precursor), after hemilabyrinthectomy in goldfish. In this lesion model, the unilateral removal of the labyrinth induces a transient postural imbalance in response to light. After the lesion, the animals were injected intraperitoneally, during 12 consecutive days, with Chlorpheniramine, L-histidine and saline. All the substances were administered in a volume of 1 ml/kg body weight. Another group, which served as a non-lesion control, did not receive hemilabyrinthectomy or systemic injections. Chlorpheniramine accelerated the functional recovery when compared with that of the saline group. These data suggest that the inhibition of the histaminergic system facilitates the functional recovery in goldfish.

Otosyphilis: report on six cases

Syphilis is a multisystemic disease that may also affect the inner ear. The objective of this study was to investigate the frequency, clinical presentation and outcome of otosyphilis. A retrospective analysis of inpatients seen by a team of ENT specialists and dermatologists at a teaching hospital in Dresden, Germany, during 1986-2000. Six cases of otosyphilis had been diagnosed. None was related to risk factors such as HIV infection or drug abuse. We identified four female and two male patients, age range 25-58 years. Four patients suffered from syphilis stage II, one from syphilis stage and another from congenitial syphilis. ENT complaints included loss or impairment of hearing, tinnitus and nystagmus. All were treated with penicillin G. Adjuvant therapy included systemic corticosteroids oral pentoxifillin in two patients each. Improvement of ENT symptoms was achieved in all but one patient, who suffered from congenitial syphilis. This study confirms that otosyphilis is still a complication of syphilis in developed countries. The first line therapy is systemic penicillin G. There is a lack of controlled trials for adjuvant treatments such as corticosteroids and pentoxifillin. Clinical cooperation between dermatologists/venereologists and ENT specialists supports the best outcome.

Typical and atypical Cogan's syndrome: 32 cases and review of the literature

OBJECTIVE

To report our experience on a multicentre series of 32 patients with either typical or atypical Cogan's syndrome, to combine our results with a detailed review of the literature, and to compare the clinical manifestations of typical and atypical Cogan's syndrome.

METHODS

Patients were identified from a survey conducted with physicians affiliated to the French National Society for Internal Medicine, and were classified into typical or atypical Cogan's syndrome according to the Haynes criteria. Clinical data were collected in a standardized manner. A comprehensive literature review using the Medline database and the reference lists of identified articles was performed.

RESULTS

Seventeen patients had typical Cogan's syndrome and 15 had atypical Cogan's syndrome. Apart from non-syphilitic interstitial keratitis, the ocular manifestations of patients with atypical Cogan's syndrome were mainly uveitis and episcleritis. All but one patient presented with Ménière-like syndrome, and at the end of follow-up 11 were deaf and 19 additional patients had developed a significant decrease in auditory acuity. Twenty-five patients (78%) developed systemic manifestations, including aortitis in four. Comparison of typical and atypical Cogan's syndrome showed that some systemic manifestations were more common in atypical Cogan's syndrome, but these differences may be explained by reporting bias in the literature.

CONCLUSION

Differences regarding the associated systemic manifestations of typical and atypical Cogan's syndrome may reflect reporting bias in the literature. However, the diversity of the ocular and audiovestibular manifestations and the acceptable lengthy delay between the two types of involvement in atypical Cogan's syndrome should make one cautious before accepting this diagnosis as the diagnosis may mimic various other systemic diseases.

Estimation of perilymph concentration of agents applied to the round window membrane by microdialysis

OBJECTIVE

The round window membrane (RWM) is known to be permeable to various biological substances. Application of biological substances to the RWM has been shown to affect inner ear fluid composition and damage hair cells, resulting in functional changes RWM instillation of gentamicin, a preferentially vestibulotoxic aminoglycoside, is used as a therapeutic treatment for patients with intractable vertigo and is gaining acceptance as a chemical vestibular ablation agent, despite considerable variations in the incidence and severity of hearing loss associated with gentamicin. Clearly, the susceptibility of vestibular and auditory hair cells to the ototoxic effects of gentamicin is not well understood. The aim of this study was to understand the kinetics of urea and methylene blue instilled into the inner ear space through the RWM and to establish a method for determining the optimal dosage for the treatment of inner ear disorders.

MATERIAL AND METHODS

We used inner ear microdialysis to quantify changes in perilymph concentration of low molecular weight agents applied to the RWM in a chinchilla model.

RESULTS

Preliminary results after placement of a microdialysis probe and application of a low molecular weight marker (urea) to the RWM were extrapolated from a time versus concentration plot from dialysates sampled over a 3-min interval using modifications of standard microdialysis equations for estimation of in vivo recovery. Our data suggest that inner ear microdialysis can be used to measure the pharmacokinetics of a low molecular weight agent within the perilymphatic space without the need for repeated direct sampling.

CONCLUSION

Inner ear microdialysis may be a useful method for establishing a therapeutic dosage for ototoxic agents used in the treatment of inner ear disorders.

Pharmacologic treatment of inner ear: from basic science to the patient

Most of the deafness are of sensorineural origin and are characterized by a loss of hair cells and of spiral ganglion neurons. At the present time, hearing aids are the only treatment. However, in some diseases of the inner ear, pharmacological treatment have been proposed and used successfully. In this paper, we will review some basic science aspects of the biology of the neurosensory structures of the inner ear, in particular of the auditory neurons, that lead to the rationale of some treatments for the inner ear diseases. Developmental studies, neuronal cell culture experiments, and analyses of gene knockout animals reveal a number of growth factors which are important for the rescue and repair of injured auditory neurons in the inner ear. These factors rescue the injured auditory neurons in vivo. Furthermore, perfusion of antioxydant to the cochlea prevented the hearing loss induced by cisplatin. These in vitro and in vivo experiments demonstrate that it is possible to manipulate the neurosensory structures of the inner ear and provide an effective treatment to prevent the degeneration of the neurons. The molecules or drugs can be administered locally to the inner ear through a direct perilymphatic perfusion or through the round window membrane. As an example, we will discuss the treatment of patients suffering from idiopathic sensorineural hearing loss which can be treated successfully by a perfusion through the round window membrane, improving their hearing threshold and their speech discrimination.

Serotonin reuptake inhibitors for dizziness with psychiatric symptoms

OBJECTIVE

To investigate the efficacy and tolerability of selective serotonin reuptake inhibitors (SSRIs) for the treatment of patients with dizziness and major or minor psychiatric symptoms, with or without neurotologic illnesses.

DESIGN

Review of 60 consecutive cases of patients with dizziness who were treated with an SSRI for at least 20 weeks during the 30-month period from July 1998 to December 2000.

SETTING

Tertiary care, multidisciplinary referral center.

PATIENTS

Sixty men and women, aged 13 to 81 years, with (1) psychogenic dizziness, (2) dizziness due to a neurotologic condition, as well as significant psychiatric symptoms, or (3) idiopathic dizziness.

INTERVENTIONS

Open-label treatment with an SSRI titrated to 1 of 3 end points: optimal clinical benefit, intolerable adverse effects, or no therapeutic response.

MAIN OUTCOME MEASURE

Change in dizziness and psychiatric symptoms measured by the 7-point, clinician-rated, Clinical Global Impressions-Improvement Scale.

RESULTS

Thirty-eight (63%) of 60 patients in the intent-to-treat sample and 32 (84%) of 38 patients who completed treatment improved substantially. The response rates did not differ between patients with major psychiatric disorders and those with lesser psychiatric symptoms. Patients whose only diagnosis was a psychiatric disorder and those with coexisting peripheral vestibular conditions or migraine headaches fared better than patients with central nervous system deficits. Before being treated with an SSRI, two thirds of the study patients took meclizine hydrochloride and/or benzodiazepines, with minimal benefit.

CONCLUSIONS

Treatment with SSRIs relieved dizziness in patients with major or minor psychiatric symptoms, including those with peripheral vestibular conditions and migraine headaches. Patients fared far better with SSRI treatment than with treatment with vestibular suppressants or benzodiazepines.

Photochemically induced equilibrium dysfunction in the hamster model with evaluation by means of a new globe rotatory test system

Thrombosis in the inner ear is regarded as one of the causes of equilibrium dysfunction. We have established an experimental thrombosis model by producing a photochemical reaction between rose bengal and green light, and have evaluated the dysfunction with a new rotatory test system. Hamsters were treated with tissue-type plasminogen activator (tPA) in doses of 0, 0.13, 0.26, and 0.52 mg/kg. The equilibrium dysfunction of the hamsters was evaluated by scoring their behavior according to visual observation and by measuring their time on the rotatory test system. Treatment of animals with sufficient tPA (> or = 0.26 mg/kg) caused a significant amelioration of the behavior and a concomitant significant prolongation of time on the rotating globe. These findings suggest that the equilibrium dysfunction induced by the photochemical reaction was due to the thrombi formed, and that our test system may provide a useful tool for evaluating equilibrium dysfunction in hamsters.

Autoimmune vestibulo-cochlear disorders

Autoimmune vestibulo-cochlear disorders (AVCD) represent a group of syndromes with overlapping clinical features, manifesting as sensorineural hearing loss, often associated with vertigo, tinnitus, and aural fullness, and believed to be caused by an autoimmune mechanism. Although definitive evidence of a classic "autoimmune process" is still lacking, substantial indirect evidence has accumulated to strongly indicate such a pathogenesis. Rapidly progressing AVCD is analogous to rapidly progressive glomerulonephritis in that inner ear inflammation progresses to severe, irreversible damage within 3 months of onset (and often much more quickly). Thus patients with rapidly progressive AVCD are treated with a sense of urgency. Prompt treatment with corticosteroids and other antirheumatic/immunosuppressive agents can preserve hearing and vestibular functions. We are not aware of any randomized controlled clinical trials evaluating the efficacy of antirheumatic/immunosuppressive agents in AVCD. In this article we review reports of various therapies that have been tried in this condition and our experience of etanercept therapy in AVCD.

Corticosteroid pharmacokinetics in the inner ear fluids: an animal study followed by clinical application

OBJECTIVE

Autoimmune disease (e.g., Cogan syndrome) and other inflammatory inner ear diseases may ravage the labyrinth if not treated aggressively with antiinflammatory medication. Corticosteroids are the mainstay of treatment, yet, partly because of the existence of the blood-labyrinthine barrier, the ideal drug, dose, and route of administration are currently unknown.

STUDY DESIGN

In the present study, we established cochlear fluid pharmacokinetic profiles of hydrocortisone, methylprednisolone, and dexamethasone in the guinea pig following oral, intravenous, and topical (intratympanic) administration. High-performance liquid chromatography was used to determine the drug concentrations, and comparisons were made with simultaneous pharmacokinetic profiles from blood and cerebrospinal fluid.

RESULTS

Our findings demonstrated a much higher penetration of all three drugs into the cochlear fluids following topical application as compared with systemic administration, with methylprednisolone showing the best profile.

DISCUSSION

The results suggested that intratympanic administration of corticosteroids might be more efficacious while avoiding high blood levels and therefore the deleterious side effects of systemic use.

CLINICAL APPLICATION

Thirty-seven patients with various inner ear disorders causing sensorineural hearing loss were subsequently treated using intratympanic corticosteroids, 20 with dexamethasone, and 17 with methlyprednisolone. Patients with immune-mediated hearing losses showed the best results, with notable improvement also seen in several cases of a "sudden deafness." No benefit was seen in patients with cochlear hydrops or those with sudden deterioration of a preexisting hearing loss. Three patients developed a transient otitis media related to the treatments, easily controlled with antibiotics. There were no cases of treatment-induced hearing loss and no permanent tympanic membrane perforations.

CONCLUSIONS

Overall injection of intratympanic corticosteroids for the treatment of hearing loss in inner ear disorders appears to be both safe and highly effective for certain disorders. The concept of this technique is supported by animal experimental data. The findings from the present study warrant further clinical application and experimental investigation.

The effects of nitric oxide synthase inhibitor, L-NAME on NO production during focal cerebral ischemia in rats: could L-NAME be the future treatment of sudden deafness?

Recent evidence in primary neuronal cell culture implicates NO as a mediator of glutamatergic neurotoxicity acting via N-methyl-D-aspartate (NMDA) receptors. In this study, we investigated the effects of inhibition of NOsynthase activity in focal cerebral ischemia in rats. Focal cerebral ischemia was produced by permanent occlusion of right MCA in urethane anesthetized rats. A number of indicators of brain NO production, nitrite and cGMP were determined in ipsilateral and contralateral cerebral cortex and cerebellum after 0, 10 and 60 minutes of focal cerebral ischemia. The same parameters were measured in rats pre- and posttreated with the potent Nitric oxide synthase (NOS) inhibitor, NW-nitro-L-arginine methyl ester (L-NAME).

Immune-mediated inner ear disease and parvovirus B19

Human parvovirus B19 (HP-B19), the etiologic agent of the common childhood illness erythema infectiosum, has been implicated in systemic immune disorders. Patients presenting with sensorineural hearing loss and/or dizziness, not readily categorized, were evaluated for immune-mediated inner ear disease. Appropriate serologic studies including parvovirus B19 antibody titers were conducted. Thirty patients with suspected immune-mediated inner ear disease were treated with corticosteroid trial for 5 to 7 days, then reexamined with repeat audiogram and/or vestibular testing. Seventeen patients with clinical response were treated with long-term corticosteroids and cyclophosphamide. Six patients had positive HP-B19 immunoglobulin M (IgM) titers and 8 patients had positive parvovirus immunoglobulin G (IgG) titers. All 14 patients responded to therapy. Parvovirus B19, therefore, is a possible etiology of immune-mediated inner ear disease.

The pharmacology of auditory and vestibular systems

Pharmacologists are among the most recent basic medical scientists to apply themselves to the auditory and vestibular systems. They bring to the subject a fresh perspective and, uniquely, the ability to control biological processes through drugs. Interest in the auditory and vestibular systems among pharmacologists has focussed on: the drug-sensitive processes (primarily but not exclusively neuro-transmission); toxicology, and pharmacotherapy. Pharmacology holds the promise of shedding further light on auditory and vestibular function and ameliorating auditory and vestibular dysfunction.