Hearing preservation using topical dexamethasone alone and associated with hyaluronic acid in cochlear implantation

The Role of Steroids in the Preservation of Hearing and Vestibular Function in Cochlear Implantation

OBJECTIVE

Cochlear implant surgery is guided by principles of atraumatic insertion as to protect the inner ear. Previous studies suggest the potential benefit of steroids in patients undergoing cochlear implantation (CI), although the optimal route of administration has yet to be determined. We aim to systematically review the human studies of hearing and vestibular function preservation in patients undergoing CI receiving perioperative steroids and to discuss their role.

DATA SOURCES

Search performed in PubMed, EMBASE, and CENTRAL databases in December 2023.

REVIEW METHODS

Studies comparing several methods of steroid delivery and conventional management for patients undergoing CI were identified. Primary outcomes included hearing and vestibular function preservation. Secondary outcomes included reported adverse events, routes of steroid administration, and the presence of a control group without steroid administration.

RESULTS

A total of 15 studies (N = 659) met inclusion criteria. Methodology, doses, route of steroid administration, and follow-up duration differed between most studies. Audiometric, vestibular, and hearing preservation (HP) results were inconsistent. In 12 studies, perioperative steroids were associated with either increased HP or vestibular function preservation. Only two studies reported adverse events related to oral corticosteroid therapy.

CONCLUSIONS

There is a tendency for perioperative steroids to have a positive impact, at least in the short term, on hearing and vestibular function preservation in CI. Topical corticosteroid therapy appears to have a superior risk-benefit profile. There is a need for future carefully designed randomized controlled trials to determine the ideal route of steroid administration and its real impact in the long term. Laryngoscope, 134:3458-3465, 2024.

Evaluation of the hearing preservation and tissue response of dexamethasone and hyaluronic acid delivery during cochlear implantation on cats in a three-month period study

OBJECTIVE

To evaluate the effects of DX and HA on hearing preservation and tissue response with cochlear implantation in a cat mode.

METHODS

11 cats were bilaterally implanted with Nurotron electrode. According to the different treatment, 22 ears were subdivided into four following groups: Electrode (E) only, Electrode +HA (E+H), Electrode + DX (E+DX), and Electrode +HA +DX (E+H+DX). Auditory brainstem responses (ABR) thresholds were recorded before and 3 months after surgery. After 3 months of cochlear implantation histopathological assessment of all cochleae were performed .

RESULTS

At low frequencies, the mean ABR thresholds shift in animals treated with E+H+DX demonstrated a statistically significant difference. The proportion of cochleae showing fibrous tissue and new bone formation was 50% in E+H+DX group, 66.7% in E+DX group, 83.3% in E+H group and 100% in E group.

CONCLUSION

United HA and DX local delivery could provide better protection against hearing loss at low-frequency threshold and could more effectively reduce the trauma related to electrode insertion and the fibrous tissue formation around the electrode.

Noise-induced hearing disorders: Clinical and investigational tools

A series of articles discussing advanced diagnostics that can be used to assess noise injury and associated noise-induced hearing disorders (NIHD) was developed under the umbrella of the United States Department of Defense Hearing Center of Excellence Pharmaceutical Interventions for Hearing Loss working group. The overarching goals of the current series were to provide insight into (1) well-established and more recently developed metrics that are sensitive for detection of cochlear pathology or diagnosis of NIHD, and (2) the tools that are available for characterizing individual noise hazard as personal exposure will vary based on distance to the sound source and placement of hearing protection devices. In addition to discussing the utility of advanced diagnostics in patient care settings, the current articles discuss the selection of outcomes and end points that can be considered for use in clinical trials investigating hearing loss prevention and hearing rehabilitation.

Improving Clinical Outcomes in Cochlear Implantation Using Glucocorticoid Therapy: A Review

Cochlear implant surgery is a successful procedure for auditory rehabilitation of patients with severe to profound hearing loss. However, cochlear implantation may lead to damage to the inner ear, which decreases residual hearing and alters vestibular function. It is now of increasing interest to preserve residual hearing during this surgery because this is related to better speech, music perception, and hearing in complex listening environments. Thus, different efforts have been tried to reduce cochlear implantation-related injury, including periprocedural glucocorticoids because of their anti-inflammatory properties. Different routes of administration have been tried to deliver glucocorticoids. However, several drawbacks still remain, including their systemic side effects, unknown pharmacokinetic profiles, and complex delivery methods. In the present review, we discuss the role of periprocedural glucocorticoid therapy to decrease cochlear implantation-related injury, thus preserving inner ear function after surgery. Moreover, we highlight the pharmacokinetic evidence and clinical outcomes which would sustain further interventions.

Inner ear drug delivery through a cochlear implant: Pharmacokinetics in a Macaque experimental model

OBJECTIVES

The method of drug delivery directly into the cochlea with an implantable pump connected to a CI electrode array ensures long-term delivery and effective dose control, and also provides the possibility to use different drugs. The objective is to develop a model of inner ear pharmacokinetics of an implanted cochlea, with the delivery of FITC-Dextran, in the non-human primate model.

DESIGN

A preclinical cochlear electrode array (CI Electrode Array HL14DD, manufactured by Cochlear Ltd.) attached to an implantable peristaltic pump filled with FITC-Dextran was implanted unilaterally in a total of 15 Macaca fascicularis (Mf). Three groups were created (5 Mf in each group), according to three different drug delivery times: 2 hours, 24 hours and 7 days. Perilymph (10 samples, 1μL each) was sampled from the apex of the cochlea and measured immediately after extraction with a spectrofluorometer. After scarifying the specimens, x-Rays and histological analysis were performed.

RESULTS

Surgery, sampling and histological analysis were performed successfully in all specimens. FITC-Dextran quantification showed different patterns, depending on the delivery group. In the 2 hours injection experiment, an increase in FITC-Dextran concentrations over the sample collection time was seen, reaching maximum concentration peaks (420-964µM) between samples 5 and 7, decreasing in successive samples, without returning to baseline. The 24-hours and 7-days injection experiments showed even behaviour throughout the 10 samples obtained, reaching a plateau with mean concentrations ranging from 2144 to 2564 µM and from 1409 to 2502µM, respectively. Statistically significant differences between the 2 hours and 24 hours groups (p = 0.001) and between the 2 hours and 7 days groups (p = 0.037) were observed, while between the 24 hours and 7 days groups no statistical differences were found.

CONCLUSIONS

This experimental study shows that a model of drug delivery and pharmacokinetics using an active pump connected to an electrode array is feasible in Mf. An infusion time ranging from 2 to 24 hours is required to reach a maximum concentration peak at the apex. It establishes then an even concentration profile from base to apex that is maintained throughout the infusion time in Mf. Flow mechanisms during injection and during sampling that may explain such findings may involve cochlear aqueduct flow as well as the possible existence of substance exchange from scala tympani to extracellular spaces, such as the modiolar space or the endolymphatic sinus, acting as a substance reservoir to maintain a relatively flat concentration profile from base to apex during sampling. Leveraging the learnings achieved by experimentation in rodent models, we can move to experiment in non-human primate with the aim of achieving a useful model that provides transferrable data to human pharmacokinetics. Thus, it may broaden clinical and therapeutic approaches to inner ear diseases.

Systemic methylprednisolone for hearing preservation during cochlear implant surgery: A double blinded placebo-controlled trial

AIM

To assess whether a single, peri-operative, high dose of methylprednisolone can improve the preservation of residual acoustic hearing following cochlear implantation (CI).

METHODS

This was a double blinded placebo-controlled trial, performed in a tertiary academic centre. The hypothesis was that methylprednisolone would improve the preservation of hearing, and lower electrode impedances. Adult patients (18-85 years) with hearing at 85 dB or better at 500 Hz in the ear to be implanted were randomly allocated to either treatment (methylprednisolone, 1g administered intravenously upon induction of anaesthesia) or control (normal saline infusion). As per standard clinical practice, all patients received a routine dose of dexamethasone (8 mg intravenously) on induction of anaesthesia. Implantation was undertaken with a slim and flexible lateral wall electrode via the round window. Surgical technique was routine, with adherence to soft surgical principles. The primary outcome was hearing preservation within 20 dB at 500 Hz, 12 months following cochlear implantation. Secondary outcomes included hearing preservation at 6 weeks and 3 months, monopolar electrode impedance, and Consonant-Vowel-Consonant (CVC) Phoneme scores at 3 and 12 months after surgery.

RESULTS

Forty-five patients were enrolled into the control group and 48 patients received the steroid. The number of patients achieving hearing preservation at 12 months did not differ significantly between those receiving methylprednisolone treatment and the controls. There were no differences in hearing preservation at any frequency at either 6 weeks or 3 months after implantation. Neither CVC phoneme scores nor electrode impedances differed between the groups.

CONCLUSIONS

This paper demonstrates that high-dose local steroid injection at surgery was not effective in preventing a loss of residual hearing, improving speech perception, or lowering electrode impedances. The findings were contrary to the experimental literature, and emerging clinical evidence that steroid elution from implant electrodes influences cochlear biology in humans. We found no evidence to support the widely-held practice of administering intravenous steroids in the perioperative period, in an attempt to preserve residual hearing.

Anatomical Correlates and Surgical Considerations for Localized Therapeutic Hypothermia Application in Cochlear Implantation Surgery

Application of localized, mild therapeutic hypothermia during cochlear implantation (CI) surgery is feasible for residual hearing preservation.

Preparation, characterization and application research of a sustained dexamethasone releasing electrode coating for cochlear implantation

Cochlear inflammatory response after cochlear implantation (CI) is an important mechanism for implantation trauma and hearing loss. The hearing loss was also caused by damage to auditory hair cells (HCs), whereas ion homeostasis within the cochlea can ensure survival of HCs. In our study, pure hyaluronic acid (HA) was crosslinked with 1, 4-butanediol diglycidyl ether (BDDE) and the successful preparation of the cross-linked hydrogel (CHA) was confirmed by rheological characteristics and FTIR spectra. Artificial perilymph (APL) was prepared to simulate the ion homeostasis microenvironment within scala tympani of human cochlear, and served as the major component of artificial perilymph soaked CHA (APL-CHA). The conductivity experiment indicated that APL-CHA is more suitable to the requirements of the electrical conductivity in scala tympani. The electrode coating process found that the extrusion coating method have advantages of controllable adhesive capacity of APL-CHA, uniform coating thickness and smooth surface as compared to common method. Due to CI surgery application requirement, optimization of coating process was selected as follows: extrusion coating method, degree of 3.6 vol%, pinhole diameter of 32G (110 μm), pressure of 200 ± 15.81 Psi. Controlled dexamethasone 21-phosphate sodium salt (DSP) release of 20 days could be demonstrated using the hydrogel filled reservoir via a validated HPLC method. The morphological structure of CHA showed different sizes of porous structure among APL-CHA provided structural basis for drug delivery. L929 fibroblasts culture and Spiral Ganglion Neuron Explants culture results revealed that APL-CHA possesses fine biological compatibility. APL-CHA shows a promising application in CI surgery and has great potential in preventing hearing loss with well simulation of ion homeostasis within the cochlear, local DSP delivery for target anti-inflammatory, approximate conductivity within the scala tympani and optimization of electrode coating process.

The Role of Preoperative Steroids for Hearing Preservation Cochlear Implantation: Results of a Randomized Controlled Trial

Objectives: To determine whether preoperative steroids can improve hearing outcomes in cochlear implantation (CI). Methods: This is a randomized controlled trial involving 30 postlingual deaf CI patients. Subjects had preoperative thresholds of better than or equal to 80 dB at 125 and 250 Hz, and better than or equal to 90 dB at 500 and 1,000 Hz. The subjects were randomized to a control group, an oral steroid group (receiving 1 mg/kg/day of prednisolone for 6 days prior to surgery), or a transtympanic steroid group (receiving a single dose of 0.5 mL of 10 mg/mL dexamethasone at 24 h prior to surgery). Results: The subjects receiving transtympanic steroids had a significant decrease in the pure tone average over 3 months compared to the control and oral steroid group, which persisted over 12 months (p < 0.05). Conclusion: A single dose of preoperative transtympanic steroids prior to CI appears to have a beneficial effect, at least in the short term, with minimal effects seen in the longer term.

Effect of a liposomal hyaluronic acid gel loaded with dexamethasone in a guinea pig model after manual or motorized cochlear implantation

Goals of cochlear implantation have shifted from complete insertion of the cochlear electrode array towards low traumatic insertion with minimally invasive techniques. The aim of this study was first to evaluate, in a guinea pig model of cochlear implantation, the effect of a motorized insertion technique on hearing preservation. The second goal was to study a new gel formulation containing dexamethasone phosphate loaded in liposomes (DEX-P). Guinea pigs had a unilateral cochlear implantation with either a manual technique (n = 12), or a motorized technique (n = 15), with a 0.4 mm diameter and 4 mm long array trough a cochleostomy. At the end of the procedure, hyaluronic acid gel containing drug-free liposomes, or liposomes loaded with DEX-P, was injected into the bulla. Auditory brainstem responses thresholds were recorded before surgery and day 2 and 7 after surgery. All the animals had increased auditory brainstem responses thresholds after the cochlear implantation. Implanted animals with the motorized insertion tool experienced a partial hearing recovery at day 7 but not in those implanted with the manual insertion procedure (p < 0.001). In the manually implanted animals, a partial recovery was observed when DEX-P contained in liposomal gel was locally administrated (p < 0.0001). Finally, no additive effect with the motorized insertion was noticed. The deleterious effect of manual insertion, during cochlear implantation, can be prevented with local DEX-P administration in the bulla at day 7. The use of a motorized tool performed more atraumatic electrode array insertion for postoperative hearing.

Analysis of Outcome Domains in Adult Cochlear Implantation: A Systematic Review

OBJECTIVES

To determine the breadth of outcome domains used in the reporting of adult cochlear implant surgery for the purpose of registry and quality measure development.

DATA SOURCES

Systematic review of randomized controlled trials.

REVIEW METHODS

In consultation with a medical librarian, search strategies were constructed to identify randomized controlled trials studying adults undergoing cochlear implantation. MEDLINE, EMBASE, Scopus, CINAHL, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, and the Database of Abstracts of Reviews of Effects were searched from database inception to July 2015. Studies were evaluated for level of evidence and risk of bias with the Cochrane Collaboration's Risk of Bias Tool, and outcome domains were extracted from each study.

RESULTS

Of 4473 unique citations found, 8 studies were included in this review. All 8 trials were evidence level 1B. Risk of bias was low in 2 trials and high in the other 6. Reported outcome domains included speech perception in quiet and noise, speech tracking, quality of life, timbre perception, hearing preservation, vestibular function, electrode insertion technique, functional measures, functional imaging, fitting time, and tinnitus.

CONCLUSIONS

An analysis of randomized controlled trials studying cochlear implantation in adults yielded a wide spectrum of outcome domains. This is the first study to comprehensively describe the breadth of outcome domains in adult cochlear implantation. Validated instruments from these domains could be considered for potential inclusion as quality measures and registry use.

Residual Hearing Preservation with the Evo® Cochlear Implant Electrode Array: Preliminary Results

Introduction The preservation of residual hearing is currently an important challenge for cochlear implant surgeries. Indeed, if patients exhibit functional hearing after cochlear implantation, they can benefit from the combination of acoustical stimulation, usually in the low-frequencies and electrical stimulation in the high-frequencies. This combined mode of stimulation has proven to be beneficial both in terms of speech perception and of sound quality. Finding the right procedures for conducting soft-surgeries and designing electrode arrays dedicated to hearing preservation is an open issue. Objective The objective of this study is to evaluate the combination of a soft-surgery procedure implicating round-window insertion and the use of dexamethasone and hyaluronic acid during surgery, with the use of a specifically designed straight soft electrode array, on hearing preservation in patients with functional hearing in the low frequencies. Methods This pre-clinical trial was conducted on seven patients with residual hearing in the low frequencies. The surgical method used employed a round window insertion and the use of topical dexamethasone. Results The soft-surgery protocol could be successfully followed in five patients. In this group, the average hearing threshold shift compared with pre-operative values was of 18.7 +/- 16.1 dB HL up to 500 Hz and 15.7 +/- 15.1 up to 1 kHz, demonstrating satisfying levels of hearing preservation. Conclusion We were able to demonstrate the possibility of preserving residual hearing in most of the patients using the EVO electrode. Significant residual hearing preservation levels were was obtained when a soft surgical approach involving round window insertion, dexamethasone and hyaluronic use during the surgery.