Dexamethasone Is One of the Factors Minimizing the Inner Ear Damage from Electrode Insertion in Cochlear Implantation

Hearing preservation in pediatric cochlear implantation

PURPOSE OF REVIEW

Pediatric cochlear implantation has evolved considerably over the past three decades to include more patients at earlier ages with greater degrees of residual hearing. As an extension, a significant focus of research over the past decade has surrounded preservation of existing acoustic hearing.

RECENT FINDINGS

Multiple studies published within the last 5 years demonstrate aidable acoustic hearing preservation in 60-90% of pediatric patients, with 40-60% experiencing complete hearing preservation following cochlear implantation. Durability of preserved hearing varies among patients, with some patients losing residual hearing within 1 year of surgery whereas others maintain acoustic hearing through at least 5 years of follow-up. Speech outcomes appear superior among patients with preserved acoustic hearing, particularly in the presence of background noise. Several recent studies suggest a music appreciation advantage in children with preserved acoustic hearing following cochlear implantation.

SUMMARY

Hearing preservation rates during cochlear implantation in children matches, if not often exceeds, hearing preservation rates observed among adults. Preservation of acoustic hearing during cochlear implantation confers multiple advantages for the pediatric population. Beyond improved speech understanding and music appreciation, minimizing intracochlear trauma and resultant scarring facilitates potential future regenerative treatments or revision surgery.

Effects of Cochlear Implantation and Steroids on the Aging Guinea Pig Cochlea

OBJECTIVE

The objective was to determine the effects of older age on hearing preservation after cochlear implantation (CI), and whether steroids improve hearing preservation in older animals. We hypothesized greater hearing preservation would be observed in (1) young animals compared to older animals and (2) older animals receiving steroids compared to no steroids. The secondary objective was to assess levels of fibrosis utilizing optical coherence tomography (OCT).

STUDY DESIGN

Experimental Animal Study.

SETTING

Laboratory.

METHODS

Three groups of guinea pigs: young (YCI; 8.5 ± 0.5 weeks; n = 10), old (OCI; 19.1 ± 1.0 months; n = 9) and old + steroids (OCI+S; 19.1 ± 1.0 months; n = 9) underwent CI. The OCI+S group received a steroid taper over 7 days starting 2 days before surgery to 4 days after. Auditory brainstem response (ABR) measurements were performed preoperatively and postoperatively. OCT imaging was performed to assess cochleae for extent of fibrotic tissue growth in the scala tympani.

RESULTS

The YCI group had significantly better hearing preservation as measured by smaller increases in ABR thresholds [mean shift: 2.79 ± 0.66] compared to the OCI group [mean shift = 12.44 ± 5.6]. The OCI+S group had significantly better hearing preservation [2.66 ± 1.50] compared to the OCI group. No significant differences was seen in fibrosis across groups.

CONCLUSIONS

Young animals and older animals that received steroids had better hearing after CI than older animals not given steroids, but hearing preservation was not correlated with the level of fibrosis assessed using OCT. This work is the first to investigate differences in hearing preservation by age in an animal model, and supports the protective effects of steroids on hearing preservation in older individuals.

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.

Functional Hearing Preservation in Cochlear Implantation: The Miami Cocktail Effect

OBJECTIVE

To investigate if pharmacological treatment with prednisone and L-N-acetylcysteine (STE + NAC) influence functional hearing preservation in cochlear implant (CI) surgery.

STUDY DESIGNS

Preimplantation and postimplantation longitudinal case-control study.

SETTING

Tertiary referral center.

PATIENTS

Pediatric and adult recipients of CI with preimplantation functional hearing defined as an average of air-conducted thresholds at 125, 250, and 500 Hz (low-frequency pure-tone average [LFPTA]) <80 dB.

INTERVENTIONS

Preimplantation and postimplantation audiometry. Weight-adjusted oral prednisone and L-N-acetylcysteine starting 2 days before surgery (Miami cocktail). Prednisone was continued for 3 days and L-N-acetylcysteine for 12 days after surgery, respectively. Cochlear implantation with conventional length electrodes.

MAIN OUTCOME MEASURES

Proportion of patients with LFPTA <80 dB, and LFPTA change at 1-year postimplantation.

RESULTS

All 61 patients received intratympanic and intravenous dexamethasone intraoperatively, with 41 patients receiving STE + NAC and 20 patients not receiving STE + NAC. At 1-year postimplantation, the proportion of functional hearing preservation was 83% in the STE + NAC group compared with 55% of subjects who did not receive STE + NAC ( p = 0.0302). The median LFPTA change for STE + NAC-treated and not treated subjects was 8.33 dB (mean, 13.82 ± 17.4 dB) and 18.34 dB (mean, 26.5 ± 23.4 dB), respectively ( p = 0.0401, Wilcoxon rank test). Perioperative STE + NAC treatment resulted in 10 dB of LFPTA better hearing than when not receiving this treatment. Better low-frequency preimplantation hearing thresholds were predictive of postimplantation functional hearing. No serious side effects were reported.

CONCLUSION

Perioperative STE + NAC, "The Miami Cocktail," was safe and superior to intraoperative steroids alone in functional hearing preservation 1-year after cochlear implantation.

Variability in Perioperative Steroid Therapy Regimen for Cochlear Implantation as It Relates to Hearing Preservation

HYPOTHESIS

We aimed to identify practice trends and association between physician training and administration of perioperative steroids for cochlear implantation (CI) as it relates to hearing preservation.

BACKGROUND

Perioperative steroid therapy regimens are postulated to protect residual hearing and improve hearing preservation outcomes in CI.

METHODS

A 27-question online survey was developed by the senior authors using the Qualtrics Survey Tool, then distributed via email from September to November 2022 to otolaryngologists specializing in otology or neurotology and who practice in the United States or Canada.

RESULTS

The survey was sent to 463 physicians, 162 (35.0%) of whom completed the survey. One hundred forty-four (31.1%) responses underwent analysis. All physicians administering preoperative steroids (n = 31) prefer preoperative oral prednisone. Of 143 physicians administering intraoperative steroids, 54.5% prefer intraoperative intravenous dexamethasone. More than half (77.6%) of 85 physicians administering postoperative steroids prefer postoperative oral prednisone. Postoperative steroid administration (p < 0.006) and taper utilization (p < 0.041) were greater among physicians who complete greater than 40 CIs annually (n = 47 [71.2%]; n = 30 [49.2%]) than physicians who complete up to 40 CIs annually (n = 37 [48.7%]; n = 20 [31.3%]), respectively. Physicians practicing for 5 to 20 years after residency are more prevalent in using postoperative steroid tapers than physicians practicing for fewer than 5 years after and more than 20 years after residency (n = 37 [51.4%] versus n = 14 [25.5%], p < 0.001).

CONCLUSION

Consensus is needed about the optimal steroid treatment for CI patients.

LEVEL OF EVIDENCE

4.

The Clinical Effect of Steroid Therapy on Preserving Residual Hearing after Cochlear Implantation with the Advanced Bionics HiRes Ultra 3D Cochlear Implant System

(1) Background: The main aim of this study was to assess the clinical effectiveness of two different schemes of administration of steroids ((1) dexamethasone administered intravenously in comparison with (2) combination of steroid treatments: orally administered prednisone and intravenously administered dexamethasone) in comparison with a control group (no steroid administration) on hearing preservation (HP) in patients who underwent an Advanced Bionics cochlear implantation. (2) Methods: Thirty-five adult patients met the inclusion criteria. All patients were randomly divided into three subgroups depending on the scheme of steroid administration: (1) the first subgroup with only intravenously administered dexamethasone (0.1 mg per kg body weight twice a day for three days), (2) the second subgroup with a combination of methods of administration of steroids (intravenous and oral steroid therapy (dexamethasone, 0.1 mg/kg body weight twice a day plus prednisone, 1 mg/kg weight once a day for three days before surgery and after administration of dexamethasone (4th, 5th, 6th day) and after this time the dose of prednisone was reduced)) and (3) the third subgroup without steroid therapy (control group). The results were measured by pure tone audiometry (PTA) in three periods: (1) before implantation, (2) during activation of the processor (one month after implantation), and (3) 12 months after activation. Patients’ hearing thresholds before implantation were on average 82 dB HL, 77 dB HL, and 88 dB HL, respectively. (3) Results: The majority of the patients from the first subgroup had hearing preserved partially (77.8%). A similar result was observed in the second study group (oral + i.v.) (partial hearing preservation was found in 61.5% of the participants). The opposite was true in the control group; a plurality of control patients (38.5%) had no measurable hearing 12 months after the activation of the processor. (4) Conclusions: Pharmacological treatment consisting of the administration of steroids in patients who had undergone cochlear implantation with the Advanced Bionics HiRes Ultra 3D cochlear implant system may be beneficial for preserving residual hearing in patients.

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.

First-in-human intracochlear application of human stromal cell-derived extracellular vesicles

Extracellular vesicles (EVs) derived from the secretome of human mesenchymal stromal cells (MSC) contain numerous factors that are known to exert anti‐inflammatory effects. MSC‐EVs may serve as promising cell‐based therapeutics for the inner ear to attenuate inflammation‐based side effects from cochlear implantation which represents an unmet clinical need. In an individual treatment performed on a ‘named patient basis’, we intraoperatively applied allogeneic umbilical cord‐derived MSC‐EVs (UC‐MSC‐EVs) produced according to good manufacturing practice. A 55‐year‐old patient suffering from Menière's disease was treated with intracochlear delivery of EVs prior to the insertion of a cochlear implant. This first‐in‐human use of UC‐MSC‐EVs demonstrates the feasibility of this novel adjuvant therapeutic approach. The safety and efficacy of intracochlear EV‐application to attenuate side effects of cochlea implants have to be determined in controlled clinical trials.

Immune Response of Macrophage Population to Cochlear Implantation: Cochlea Immune Cells

HYPOTHESIS

The presence and distribution of ionized calcium binding adaptor 1 and CD68 macrophages in the human cochlea is altered in cochlear implantation (CI) compared with the normative or nonimplanted cochlea.

BACKGROUND

It has been hypothesized that CI induces an immunological response in macrophages leading to implant failure or reduced hearing. Macrophages are resident immune cells in human cochlea and have been shown to phagocytize implant material. In animal models, macrophage populations increase with surgical stress and with the introduction of a foreign body. However, the function and response of inner ear macrophages to CI are only beginning to be understood. This study seeks to investigate the inflammatory response to CI by comparing cochlear macrophages in implanted and nonimplanted human temporal bones.

METHODS

Nineteen temporal bones from nine implanted ears, seven contralateral controls, and three normal control ears were evaluated for the presence and distribution of CD68 and Iba1 expressing positive macrophages.

RESULTS

Three types of macrophage populations were detected 1) CD68 positive macrophages, 2) Iba1 positive macrophages, and 3) CD68 and Iba1 colocalizing macrophages. Macrophage distribution was ubiquitous: the stria vascularis, Rosenthal canal, and the mid-modiolus intermingled in the spiral ganglia. Iba1 and CD68 macrophages were found in the CI and non-CI contralateral and normal human cochlea. Most ionized calcium binding adaptor 1 expressing macrophages were ramified/amoeboid cells, while CD68 expressing macrophages were round shaped with foamy appearance in some areas. In the CI cochlea, both types of macrophages were detected in the fibrous sheath surrounding the CI path and within fibrotic areas within the scala tympani and the scala vestibuli in the case of CI translocation. In four cases, the density of macrophages was unchanged in the CI compared with the contralateral nonimplanted side, and in three cases, there was an increased number of macrophages in the implanted CI side compared with the nonimplanted side.

CONCLUSION

Multiple populations of macrophages exist within the cochlea which are present at baseline and in response to trauma from CI. These results further support evidence for a macrophage response to cochlear implantation. Further studies are indicated to evaluate whether these macrophages have a beneficial, detrimental, or a mixed effect in CI patients.

Development of a rapidly made, easily personalized drug-eluting polymer film on the electrode array of a cochlear implant during surgery

OBJECTIVE

To develop a drug-eluting polymer film which can be easily personalized and rapidly made on the electrode array of a cochlear implant during surgery.

METHODS

A precursor solution was prepared with poly lactic-co-glycolic acid (PLGA) and trichloromethane. Using a dip-coating method, the silicone electrode array (HiFocus 1J, Advanced Bionics) was coated in polymer film produced from the precursor solution containing one of three drugs: dexamethasone sodium phosphate (DSP), cytosine arabinoside hydrochloride (Ara-C), or nicotinamide adenine dinucleotide (NAD), and the release of these drugs from the polymer film was studied. The drug-eluting film on the electrode array was analyzed by environmental scanning electron microscopy (ESEM). The water contact angle and the impedance of the electrode array were measured before and after coating. Drug release kinetics was evaluated in a quasi-stationary release model, using high performance liquid chromatography every 24 h for 15 days.

RESULTS

Five electrode arrays were tested with each of the three drugs in the polymer film coating. Before and after coating, ESEM studies revealed that the drug-loaded PLGA coating yielded a smooth covering with an average thickness of 1.02 ± 0.05 μm. The mass of the coated electrode increased by 1.00 ± 0.03 mg. The water contact angle decreased after coating (102 ± 0.6° vs 77 ± 1.6°, p < 0.01) but there was no significant change in the average impedance of the electrodes after coating (0.9 ± 0.22 kΩ vs 1.0 ± 0.18 kΩ, p > 0.05). An in vitro drug kinetics study revealed a faster release in the first 24 h (63.4 ± 0.6%) and a sustained release over the following 15 days (78.3 ± 1.7% in 2 days, 95.6 ± 1.0% in 7 days and 99.1 ± 0.4% in 14 days). The release rate was not affected by the drug, dose or the thickness of the coating.

CONCLUSION

The dip-coating method is feasible for rapid casting of a drug-eluting PLGA film on an electrode array during CI surgery. The coated electrode array maintained its original morphology and became more hydrophilic. The loaded drug is released in a sustained manner and is easily regulated, and so the method might represent a potential application for clinical use in cochlear implantation.

Long-Term in vivo Release Profile of Dexamethasone-Loaded Silicone Rods Implanted Into the Cochlea of Guinea Pigs

Glucocorticoids are used intra-operatively in cochlear implant surgeries to reduce the inflammatory reaction caused by insertion trauma and the foreign body response against the electrode carrier after cochlear implantation. To prevent higher systemic concentrations of glucocorticoids that might cause undesirable systemic side effects, the drug should be applied locally. Since rapid clearance of glucocorticoids occurs in the inner ear fluid spaces, sustained application is supposedly more effective in suppressing foreign body and tissue reactions and in preserving neuronal structures. Embedding of the glucocorticoid dexamethasone into the cochlear implant electrode carrier and its continuous release may solve this problem. The aim of the present study was to examine how dexamethasone concentrations in the electrode carrier influence drug levels in the perilymph at different time points. Silicone rods were implanted through a cochleostomy into the basal turn of the scala tympani of guinea pigs. The silicone rods were loaded homogeneously with 0.1, 1, and 10% concentrations of dexamethasone. After implantation, dexamethasone concentrations in perilymph and cochlear tissue were measured at several time points over a period of up to 7 weeks. The kinetic was concentration-dependent and showed an initial burst release in the 10%- and the 1%-dexamethasone-loaded electrode carrier dummies. The 10%-loaded electrode carrier resulted in a more elevated and longer lasting burst release than the 1%-loaded carrier. Following this initial burst release phase, sustained dexamethasone levels of about 60 and 100 ng/ml were observed in the perilymph for the 1 and 10% loaded rods, respectively, during the remainder of the observation time. The 0.1% loaded carrier dummy achieved very low perilymph drug levels of about 0.5 ng/ml. The cochlear tissue drug concentration shows a similar dynamic to the perilymph drug concentration, but only reaches about 0.005–0.05% of the perilymph drug concentration. Dexamethasone can be released from silicone electrode carrier dummies in a controlled and sustained way over a period of several weeks, leading to constant drug concentrations in the scala tympani perilymph. No accumulation of dexamethasone was observed in the cochlear tissue. In consideration of experimental studies using similar drug depots and investigating physiological effects, an effective dose range between 50 and 100 ng/ml after burst release is suggested for the CI insertion trauma model.

Cochlear Implant

Cochlear implant is the first approved cranial nerve stimulator that works by directly stimulating the cochlear nerve. The medical and societal impact of this revolutionary device cannot be understated. This article reviews the evolving indications for cochlear implant, patient assessment, surgical approach, and outcomes for pediatric and adult cochlear implant that demonstrate its impact. Future concepts in cochlear implant are introduced briefly. This article covers a breadth of information; however, it is not intended be entirely comprehensive. Rather, it should serve as a foundation for understanding cochlear implant.

Preservation of Hearing Following Cochlear Implantation Using Different Steroid Therapy Regimens: A Prospective Clinical Study

Background

A prospective clinical study was conducted to assess different regimens of steroid therapy and preservation of hearing following cochlear implantation.

Material/Methods

Study participants were ≥18 years-of-age, with a cochlear duct length ≥27.1 mm measured by computed tomography (CT), with hearing sound levels in the range of 10–120 decibels (dB) and sound frequencies of 125–250 hertz (Hz); sound levels of 35–120 dB and frequencies of 500–1,000 Hz; sound levels of 75–120 dB and frequencies of 2,000–8,000 Hz. Study exclusion criteria included diseases with contraindications for steroid therapy or medications that increased the effects of steroids. Patients had cochlear implantation and were divided into three treatment groups: intravenous (IV) steroid therapy (standard steroid therapy): combined oral and IV steroid therapy (prolonged steroid therapy); and a control group (cochlear implantation without steroid therapy). Hearing preservation was established by pure tone audiometry based on the pre-operative and postoperative average hearing thresholds according to the formula developed by the HEARRING Network.

Results

There were 36 patients included in the study. In all cases, the cochlear implant electrode was inserted via the round window approach with a straight electrode length of 28 mm. Patients with combined oral and IV steroid therapy (prolonged steroid therapy) had better results when compared with patients with intravenous (IV) steroid therapy (standard steroid therapy) and the control group.

Conclusions

Prolonged steroid therapy using combined oral and IV steroids stabilized hearing thresholds and preserved hearing in adult patients following cochlear implantation.

Effects of dexamethasone on intracochlear inflammation and residual hearing after cochleostomy: A comparison of administration routes

Preservation of residual hearing after cochlear implant is an important issue with regards to hearing performance. Various methods of steroid administration have been widely used in clinical practice to reduce inflammation and preserve residual hearing. Here we compare the effect of different routes of dexamethasone administration on intracochlear inflammation and residual hearing in guinea pig ears. Dexamethasone was delivered into the guinea pigs either through intracochlear, intratympanic or systemic route. The intracochlear concentration of dexamethasone, residual hearing, inflammatory cytokines and histopathologic changes were evaluated over time. A higher intracochlear dexamethasone concentration was observed after intracochlear administration than through the other routes. Residual hearing was better preserved with local dexamethasone administration as was supported by the reduced inflammatory cytokines, more hair cell survival and less severe intracochlear fibrosis and ossification concurrently seen in the local delivery group than in the systemic group. The results demonstrate that local dexamethasone delivery can reduce intracochlear inflammation and preserve residual hearing better than in systemically administered dexamethasone.

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.

Steroid intracochlear distribution differs by administration method: Systemic versus intratympanic injection

OBJECTIVE

Steroids have been widely used to treat inner-ear diseases such as sudden sensorineural hearing loss, tinnitus, and Meniere's disease. They can be given via either systemic or intratympanic (IT) injection. The purpose of the present study was to explore differences in intracochlear steroid distribution by the administration method employed (systemic vs. IT injection).

STUDY DESIGN

Animal study.

METHODS

Twenty-three Sprague-Dawley rats were given fluorescein isothiocyanate-labeled dexamethasone (FITC-DEX) three times (on successive days) via intraperitoneal (IP) or IT injection. Cochlear uptake of FITC-DEX was evaluated via immunohistochemistry and flow cytometry at 6 hours, and 3 and 7 days after the final injection.

RESULTS

FITC-DEX uptake was evident in spiral ganglion cells (SGs), the organ of Corti (OC), and the lateral walls (LWs), the basal turns of which were stained relatively prominently in both groups. Animals receiving IP injections exhibited higher FITC-DEX uptakes by the SGs and OC, whereas IT injection triggered higher-level FITC-DEX accumulation by the OC and LWs. Flow cytometry revealed that intracochlear FITC-DEX uptake by IT-injected animals was higher and more prolonged than in animals subjected to IP injections.

CONCLUSION

We thus describe differences in cochlear steroid distributions after systemic and IT injections. This finding could help our understanding of the pharmacokinetics of steroids in the cochlea.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:189-194, 2018.