Cochlear implantation outcomes in children with multiple disabilities: a topic that's worth revisiting.

OBJECTIVES: To determine the benefits of cochlear implantation in hearing loss children with multiple disabilities (MD) in terms of auditory outcomes, speech performance, and their quality of life. METHODS: This was a cross sectional study from January 2019 to December 2020 in which thirty-one children with hearing loss and multiple disabilities were evaluated. Their improvement in auditory and speech performances were assessed using Categories of Auditory Performance version II (CAP-II) and the Speech Intelligibility Rating (SIR) scales. The assessment was done at 6-month intervals, with the baseline evaluation done at least six months after activation of the implant. Parents were asked to fill the Parents Evaluation of Aural/Oral Performance of Children (PEACH) diary and Perceived Benefit Questionnaire (PBQ) to evaluate the child's quality of life. RESULTS: All 31 children have Global Developmental Delay (GDD), with 11 having an additional disability. Both mean CAP-II and SIR scores showed significant improvement with increased hearing age (p < 0.05) after 6-month intervals. In addition, 20 out of 31 children (64.5%) have achieved verbal communication after implantation. The mean PEACH score in quiet was significantly better than in noise (p = 0.007) and improved with the increased of hearing age. The majority of parents (96%‒100%) perceived a cochlear implant as beneficial to their child in terms of auditory response, awareness, interaction, communication, and speech development. CONCLUSIONS: Cochlear implantation had shown benefits in children with multiple disabilities. Outcome measures should not only focus on auditory and speech performances but the improvement in quality of life. Hence, individualized each case with realistic expectation from families must be emphasized in this group of children. LEVEL OF EVIDENCE: Level 3.

Photosynthetic conversion of carbon dioxide from cement production to microalgae biomass.

Production of microalgae is a potential technology for capturing and recycling carbon dioxide from cement kiln emissions. In this study, a process of selecting a suitable strain that would effectively utilize carbon dioxide and generate biomass was investigated. A down-selection screening method was applied to 28 strains isolated from the area surrounding a commercial cement plant. In laboratory-scale (1 L) continuous-mode chemostats, observed productivity was > 0.9 g L-1 d-1 for most strains studied. Chlorella sorokiniana (strain SMC-14M) appeared to be the most tolerant to cement kiln gas emissions in situ, delivered under control of a pH-stat system, and was down-selected to further investigate growth and biomass production at large-scale (1000 L) cultivation. Results demonstrated little variability in lipid, crude protein, and carbohydrate composition throughout growth between kiln-gas grown algal biomass and biomass produced with laboratory grade CO2. The growth rate at which the maximum quantity of CO2 from the emissions is recycled also produced the maximum amount of the targeted biomass components to increase commercial value of the biomass. An accumulation of some heavy metals throughout its growth demonstrates the necessity to monitor the biomass cultivated with industrial flue gases and to carefully consider the potential applications for this biomass; despite its other attractive nutritional properties. KEY POINTS: • Studied high biomass producing algal strains grown on CO2 from cement flue gas. • Chlorella sorokiniana SMC-14M grew well at large scale, in situ on cement flue gas. • Demonstrated the resulting commercial potential of the cultured algal biomass.

Cochlear implant surgery facilitates intracochlear distribution of perioperative systemic steroids.

BACKGROUND: Systemically administered steroids are widely utilised for hearing preservation therapies. More recently, steroids have been administered to achieve hearing protection after cochlear implant surgery. Currently there is a lack of understanding as to which administration route offers most therapeutic efficacy, local or systemic administration. Paramount to this are observations in animal studies that systemic administration following implantation offers hearing protection and reduced cochlear fibrosis, despite observations that perilymphatic levels are up to 10-fold higher after local administration in non-implanted cochleae. AIMS/OBJECTIVES: This paper explores the impact that cochlear implantation and associated acute inflammation has on steroid distribution and uptake following systemic administration of dexamethasone. MATERIAL AND METHODS: Eight guinea pigs received systemic dexamethasone 60 min prior to cochlear implantation. Implanted and contralateral non-implanted cochlea were harvested for tissue immunohistochemistry and detection of dexamethasone. RESULTS: Cochleostomy with scala tympani implantation resulted in a significant increase in cochlear dexamethasone signal. This was most notable at the organ of Corti, stria vascularis, and blood product in the scala tympani. CONCLUSIONS AND SIGNIFICANCE: This study demonstrates that the inner ear distribution of systemically administered steroids is enhanced following surgery for cochlear implantation and provides rationale for systemic perioperative steroids in hearing preservation surgery.

Systematic review of the diagnostic value of hydrops MRI in relation to audiovestibular function tests (electrocochleography, cervical vestibular evoked myogenic potential and caloric test).

The objective of this systematic review is to compare the diagnostic value of endolymphatic hydrops (EH) magnetic resonance imaging (MRI) with audiovestibular function tests, including electro cochleography (ECochG), cervical vestibular evoked myogenic potential (cVEMP) and caloric tests for the diagnosis of definite Meniere's disease (DMD). An electronic search was performed in the PubMed, Embase and Cochrane databases in August 2022. Original studies which reported the efficacy of gadolinium MRI for diagnosis of DMD were compared with ECochG, cVEMP and caloric tests from 2007 to 2022 published in English. Two reviewers extracted the methodology and results of MRI and functional tests, assessing them independently. A modified version of the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) was used for the assessment of the quality and the risk of bias of each study. The proportion of DMD cases diagnosed by MRI hydrops vs corresponding functional tests were calculated and the relationship between MRI and functional tests were evaluated using the Cohen's Kappa test. Concerning the MRI, the proportion diagnostic of DMD was 0.67 by cochlear EH and 0.80-0.82 by vestibular EH. Regarding the functional test, the propotiojn diagnostic of DMD was 0.48 by ECochG, 0.76 by cVEMP and 0.65 by caloric test. The findings of this systematic review were that the vestibular EH on imaging most effectively assisted in diagnosing DMD. Among the functional tests, cVEMP was the second most effective test. The agreement between imaging and cVEMP was moderate (0.44), indicating a gap between the patients identified by the imaging and functional tests based on the relatively small number of patients.

Four-Point Impedance Changes After Cochlear Implantation for Lateral Wall and Perimodiolar Implants.

OBJECTIVE: Monitor four-point impedance in cochlear implant recipients over time and determine if implant type, surgical approach, and electrode positioning affected impedance measurements. STUDY DESIGN: Prospective observational. SETTING: Hospital. PATIENTS: Adult cochlear implant recipients implanted with a perimodiolar or lateral wall cochlear implant. MAIN OUTCOME MEASURES: Mean values for four-point impedances were calculated for all electrode contacts at perioperative and 3 months after surgery. Linear mixed models were applied to the impedance data to compare between implant types and time points. The angular insertion depth and electrode position relative to the medial and lateral wall, commonly termed the Intracochlear Position Index (ICPI), were collected and compared with impedance measurements. RESULTS: Perioperatively, the four-point impedance was similar between implant types, with perimodiolar implants having marginally higher impedance values in the basal region. At 3 months after surgery, impedances significantly increased in the basal half of the electrode array for both implants, with higher impedance values for CI532 implants. There were no significant differences in insertion angle depth between implant types. The ICPI values for the seven most basal electrodes were similar for both implants; however, CI532 arrays were significantly more medially placed along the remaining apical portion of the array, which is expected. ICPI values did not correlate with impedance measurements for either implant. CONCLUSIONS: Four-point impedance increases at 3 months after surgery may reflect fibrous tissue formation after cochlear implantation. The higher impedance values in perimodiolar implants may reflect a more extensive fibrosis formation as a result of surgical approaches used, requiring drilling of the cochlea bone.

Four-point Impedance Changes in the Early Post-Operative Period After Cochlear Implantation.

OBJECTIVE: Monitoring four-point impedance changes after cochlear implantation with comparison to conventional impedance measurements. Four-point impedance provides information regarding the bulk biological environment surrounding the electrode array, which is not discernible with conventional impedances. STUDY DESIGN: Prospective observational. SETTING: Hospital. PATIENTS: Adult cochlear implant recipients with no measurable hearing before implantation and implanted with a perimodiolar cochlear implant. MAIN OUTCOME MEASURES: Mean values for four-point and common ground impedances were calculated for all electrode contacts at intra-operative, 1 day, 1 week, 4 to 6 weeks, and 3 months post implantation. Linear mixed models were applied to the impedance data to compare between impedances and time points. Furthermore, patients were divided into groups dependent on the normalized change in four-point impedance from intra-operative to 1 day post-operative. The normalized change was then calculated for all other time points and compared across the two groups. RESULTS: Significant increases in four-point impedance occurred 1 day and 3 months after surgery, particularly in the basal half of the array. Four-point impedance at 1 day was highly predictive of four-point impedance at 3 months. Four-point impedance at the other time points showed marginal or no increases from intra-operative. Patients with an average increase higher than 10% in four-point impedance from intra-operative to 1 day, had significantly higher values at 3 months ( p = 0.012). These patterns were not observed in common ground impedance. CONCLUSION: This is the first study to report increases in four-point impedance within 24 hours of cochlear implantation. The increases at 1 day and 3 months align with the natural timeline of an acute and chronic inflammatory responses.

Spironolactone Ameliorates Cochlear Implant Induced Endolymphatic Hydrops.

BACKGROUND: Endolymphatic hydrops (EH) has been observed in both animal and human cochleae following cochlear implant (CI) surgery. We tested whether EH could be eliminated by administration of mineralocorticoid steroid antagonist spironolactone and explored the electrophysiological consequences of this. METHODS: Sixty-four adult guinea pigs underwent cochlear implantation with a dummy electrode. Animals then survived either 2, 7, or 28 days. Auditory function was monitored by recording electrocochleography from the round window membrane preimplantation, and on the last day of the experiment. Spironolactone or control solution was added to animals' feed for 7 days (if they survived that long) beginning immediately prior to surgery. The presence of EH was determined using thin-sheet laser imaging microscopy. RESULTS: Treatment with spironolactone resulted in significant reduction in EH in the second cochlear turn 7 days postimplantation. In all animals, the compound action potential (CAP) threshold was elevated 2 days postimplantation, but for most frequencies had recovered substantially by 28 days. There was no treatment effect on CAP thresholds. SP/AP ratios were elevated at day 2. The amplitude growth of the CAP did not differ between test and control groups at any time after implantation. CONCLUSIONS: EH can be suppressed by antagonism of mineralocorticoid receptors in the week after cochlear implantation. Reduction in EH did not lead to any change in hearing, and there was no indication of synaptopathy signalled by reduced CAP amplitude at high sound intensities. We found no electrophysiological evidence that EH early after implantation impacts negatively upon preservation of residual hearing.

Mice heterozygous for the Serpinb6a null mutation show deficits in central auditory function after acoustic trauma.

OBJECTIVES: Complete deficiency of the serine protease inhibitor gene, SERPINB6, is responsible for autosomal-recessive, nonsyndromic sensorineural hearing loss in humans. A mouse model of this deafness gene identifies Serpinb6a expression in the neurosensory epithelium and fibrocytes of the cochlea. Homozygous Serpinb6a mutant mice display an exaggerated hearing loss after exposure to moderate acoustic trauma. It is unknown if and how heterozygous Serpinb6a mice show increased vulnerability to acoustic trauma. METHODS: We exposed Serpinb6a+/- and Serpinb6a+/+ mice to acoustic trauma and measured their hearing function prior to, 3 and 14 days postexposure, analysing shifts in hearing threshold and amplitudes of Wave I and II of the auditory brainstem-evoked response (ABR) to 4, 8, 16 and 32 kHz tones. RESULTS: Shifts in hearing threshold and Wave I amplitude of Serpinb6a+/- mice were not significantly different from Serpinb6a+/+ mice at both time points and all frequencies tested (P > 0.05, Mann-Whitney test). However, Wave II amplitudes at 16 and 32 kHz tones, were more severely diminished in Serpinb6a+/- mice (P < 0.05). To exclude any effects of ageing on auditory function in Serpinb6a+/- mice, hearing function of unexposed Serpinb6a+/- mice was measured at start and end of the experimental period. The shift in Wave II amplitude of exposed Serpinb6a+/- mice was significantly lower than unexposed Serpinb6a+/- mice only at 16 and 32 kHz (P < 0.01), confirming acoustic trauma as the main cause of hearing deficits in Serpinb6a+/- mice. CONCLUSION: These results suggest that heterozygous Serpinb6a humans may be vulnerable to noise.

Viral-mediated transduction of auditory neurons with opsins for optical and hybrid activation.

Optical stimulation is a paradigm-shifting approach to modulating neural activity that has the potential to overcome the issue of current spread that occurs with electrical stimulation by providing focused stimuli. But optical stimulation either requires high power infrared light or genetic modification of neurons to make them responsive to lower power visible light. This work examines optical activation of auditory neurons following optogenetic modification via AAV injection in two species (mouse and guinea pig). An Anc80 viral vector was used to express the channelrhodopsin variant ChR2-H134R fused to a fluorescent reporter gene under the control of the human synapsin-1 promoter. The AAV was administered directly to the cochlea (n = 33) or posterior semi-circular canal of C57BL/6 mice (n = 4) or to guinea pig cochleae (n = 6). Light (488 nm), electrical stimuli or the combination of these (hybrid stimulation) was delivered to the cochlea via a laser-coupled optical fibre and co-located platinum wire. Activation thresholds, spread of activation and stimulus interactions were obtained from multi-unit recordings from the central nucleus of the inferior colliculus of injected mice, as well as ChR2-H134R transgenic mice (n = 4). Expression of ChR2-H134R was examined by histology. In the mouse, transduction of auditory neurons by the Anc80 viral vector was most successful when injected at a neonatal age with up to 89% of neurons transduced. Auditory neuron transductions were not successful in guinea pigs. Inferior colliculus responses to optical stimuli were detected in a cochleotopic manner in all mice with ChR2-H134R expression. There was a significant correlation between lower activation thresholds in mice and higher proportions of transduced neurons. There was no difference in spread of activation between optical stimulation and electrical stimulation provided by the light/electrical delivery system used here (optical fibre with bonded 25 µm platinum/iridium wire). Hybrid stimulation, comprised of sub-threshold optical stimulation to 'prime' or raise the excitability of the neurons, lowered the threshold for electrical activation in most cases, but the impact on excitation width was more variable compared to transgenic mice. This study demonstrates the impact of opsin expression levels and expression pattern on optical and hybrid stimulation when considering optical or hybrid stimulation techniques for neuromodulation.

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.

Otitis media guidelines for Australian Aboriginal and Torres Strait Islander children: summary of recommendations.

INTRODUCTION: The 2001 Recommendations for clinical care guidelines on the management of otitis media in Aboriginal and Torres Islander populations were revised in 2010. This 2020 update by the Centre of Research Excellence in Ear and Hearing Health of Aboriginal and Torres Strait Islander Children used for the first time the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. MAIN RECOMMENDATIONS: We performed systematic reviews of evidence across prevention, diagnosis, prognosis and management. We report ten algorithms to guide diagnosis and clinical management of all forms of otitis media. The guidelines include 14 prevention and 37 treatment strategies addressing 191 questions. CHANGES IN MANAGEMENT AS A RESULT OF THE GUIDELINES: A GRADE approach is used. Targeted recommendations for both high and low risk children. New tympanostomy tube otorrhoea section. New Priority 5 for health services: annual and catch-up ear health checks for at-risk children. Antibiotics are strongly recommended for persistent otitis media with effusion in high risk children. Azithromycin is strongly recommended for acute otitis media where adherence is difficult or there is no access to refrigeration. Concurrent audiology and surgical referrals are recommended where delays are likely. Surgical referral is recommended for chronic suppurative otitis media at the time of diagnosis. The use of autoinflation devices is recommended for some children with persistent otitis media with effusion. Definitions for mild (21-30 dB) and moderate (> 30 dB) hearing impairment have been updated. New "OMapp" enables free fast access to the guidelines, plus images, animations, and multiple Aboriginal and Torres Strait Islander language audio translations to aid communication with families.

Increased susceptibility to acoustic trauma in a mouse model of non-syndromic sensorineural deafness, DFNB91.

Inactivating mutations of SERPINB6 in humans result in progressive hearing loss starting in early adulthood (DFNB91). We have previously shown that C57BL/6J mice lacking the orthologous gene, Serpinb6a, exhibit progressive hearing loss, which is associated with progressive loss of distinct cell types in the organ of Corti beginning with outer hair cells (OHCs). However, deafness in these animals occurs much earlier than expected, possibly because C57BL/6J mice also carry an age-related hearing loss mutation in the cadherin 23 gene (Cdh23ahl ) that causes late onset hearing loss. The CBA/CaH strain of mice does not carry Cdh23ah/ahl and may represent a better model of the human DFNB91 patients. Here, we show that transfer of the mutant Serpinb6a allele onto the Cdh23 normal CBA/CaH background markedly delays onset of hearing loss, more closely phenocopying DFNB91, without altering the pattern of cellular loss. Young, pre-symptomatic mice of this genotype exposed to acoustic trauma exhibit permanent hearing loss, compared to controls, associated with the disappearance of OHCs. We conclude that Serpinb6 helps to maintain hearing by protecting hair cells from stress.

A triticale tapetal non-specific lipid transfer protein (nsLTP) is translocated to the pollen cell wall.

KEY MESSAGE: A Triticeae type III non-specific lipid transfer protein (nsLTP) was shown for the first time to be translocated from the anther tapetum to the pollen cell wall. Two anther-expressed non-specific lipid transfer proteins (nsLTPs) were identified in triticale (× Triticosecale Wittmack). LTPc3a and LTPc3b contain a putative signal peptide sequence and eight cysteine residues in a C-Xn-C-Xn-CC-Xn-CXC-Xn-C-Xn-C pattern. These proteins belong to the type III class of nsLTPs which are expressed exclusively in the inflorescence of angiosperms. The level of LTPc3 transcript in the anther was highest at the tetrad and uninucleate microspore stages, and absent in mature pollen. In situ hybridization showed that LTPc3 was expressed in the tapetal layer of the developing triticale anther. The expression of the LTPc3 protein peaked at the uninucleate microspore stage, but was also found to be associated with the mature pollen. Accordingly, an LTPc3a::GFP translational fusion expressed in transgenic Brachypodium distachyon first showed activity in the tapetum, then in the anther locule, and later on the mature pollen grain. Altogether, these results represent the first detailed characterization of a Triticeae anther-expressed type III nsLTP with possible roles in pollen cell wall formation.

A new method for three-dimensional immunofluorescence study of the cochlea.

Visualisation of cochlear histopathology in three-dimensions has been long desired in the field of hearing research. This paper outlines a technique that has made this possible and shows a research application in the field of hearing protection after cochlear implantation. The technique utilises robust immunofluorescent labelling followed by effective tissue clearing and fast image acquisition using Light Sheet Microscopy. We can access the health of individual components by immunofluorescent detection of proteins such as myosin VIIa to look at cochlear hair cells, NaKATPase alpha 3 to look at spiral ganglion neurons, and IBA1 to look at macrophages within a single cochlea, whilst maintaining the integrity of fine membranous structures and keeping the cochlear implant in place. This allows the tissue response to cochlear implantation to be studied in detail, including the immune reaction to the implant and the impact on the structure and health of neural components such as hair cells. This technique reduces time and labour required for sectioning of cochleae and can allow visualisation of cellular detail. Use of image analysis software allows conversion of high-resolution image stacks into three-dimensional interactive data sets so volumes and numbers of surfaces can be measured. Immunofluorescent whole cochlea labelling and Light Sheet Microscopy have the capacity to be applied to many questions in hearing research of both the cochlea and vestibular system.

Slim, Modiolar Cochlear Implant Electrode: Melbourne Experience and Comparison With the Contour Perimodiolar Electrode.

OBJECTIVE: To describe the tip fold over rate, scalar localization, and speech perception outcomes of the CI532 Slim Modiolar Electrode. PATIENTS AND INTERVENTION: All patients receiving the CI532 implant before June 2018. MAIN OUTCOME MEASURES: Outcome measures for adults patients include pre- and postoperative speech perception, operative report details, electrode position as determined by X-ray and cone beam computed tomography. Comparison made with previous experience with the Contour perimodiolar electrode (CI512). In the pediatric population tip fold-over rate, measured by intraoperative X-ray, was the exclusive outcome. RESULTS: One hundred twenty-five CI532 devices were implanted in adults and 69 in children. Electrode tip fold-over occurred in eight adults cases and none among children (4.1%). Cone beam CT scans of 120 out of 125 adult patients confirmed scala tympani (ST) position in all but one case where the electrode had been placed into scala vestibuli. There were no translocations from ST to scala vestibuli. This compares favorably with the CI512 translocation rate of 17%. Speech perception outcomes demonstrated good performance with mean preop phoneme scores of 16.2% (±13) increasing to 64.2% (±14) and 71.6 (±16) 3 and 12-months postop, respectively. Compared with a matched group of CI512 recipients, CI532 recipient phoneme scores were significantly higher 3 and 12-months postop by 4 and 7%, respectively. CONCLUSION: The slim modiolar, CI532 electrode has provided very reliable ST position with a low rate of tip fold over. A trend toward better speech perception scores in CI532 compared with CI512 was observed.

Nanomechanical mapping reveals localized stiffening of the basilar membrane after cochlear implantation.

Cochlear implantation leads to many structural changes within the cochlea which can impair residual hearing. In patients with preserved low-frequency hearing, a delayed hearing loss can occur weeks-to-years post-implantation. We explore whether stiffening of the basilar membrane (BM) may be a contributory factor in an animal model. Our objective is to map changes in morphology and Young's modulus of basal and apical areas of the BM after cochlear implantation, using quantitative nanomechanical atomic force microscopy (QNM-AFM) after cochlear implant surgery. Cochlear implantation was undertaken in the guinea pig, and the BM was harvested at four time-points: 1 day, 14 days, 28 days and 84 days post-implantation for QNM-AFM analysis. Auditory brainstem response thresholds were determined prior to implantation and termination. BM tissue showed altered morphology and a progressive increase in Young's modulus, mainly in the apex, over time after implantation. BM tissue from the cochlear base demonstrated areas of extreme stiffness which are likely due to micro-calcification on the BM. In conclusion, stiffening of the BM after cochlear implantation occurs over time, even at sites far apical to a cochlear implant.

Glucocorticoid for Hearing Preservation After Cochlear Implantation: A Systemic Review and Meta-analysis of Animal Studies.

OBJECTIVES: To conduct systematic review and meta-analyses of preclinical studies describing the efficacy of glucocorticoids administered via different routes for hearing preservation after cochlear implantation. DATA SOURCES: A literature search was performed in PubMed to identify peer-reviewed articles published before December 31, 2017, with no language restrictions. Search components were "Cochlear implant," "Glucocorticoids," and "Hearing preservation." The results were specified for animal studies. STUDY SELECTION: Original studies in which glucocorticoids were administered before or during cochlear implantation in animal models and hearing threshold shifts were measured using auditory brainstem response. DATA EXTRACTION: Quality of included studies was assessed using the SYstematic Review Centre for Laboratory animal Experimentation protocol. Threshold Shift reduction between the "study" and "control" groups at 1-month postimplantation was the parameter used to evaluate hearing preservation. DATA SYNTHESIS: The random-effects models were used to combine the results of selected studies. Separate meta-analyses were performed for drug-eluting electrodes, systemic, and local administration. CONCLUSIONS: Administering either systemic or topical glucocorticosteroids had a significant effect on preserving low and high-frequency hearing. Topical administration was equally effective across a range of concentration levels and provided maximal hearing preservation when applied 120 minutes before implantation. The effect of systemic treatment was achieved with high doses, equivalent to 26 mg of dexamethasone per day in humans. No significant effect was found with the use of drug-eluting electrodes and more studies are needed to characterise the utility and efficacy of this administration method.

Electrical Impedance as a Biomarker for Inner Ear Pathology Following Lateral Wall and Peri-modiolar Cochlear Implantation.

OBJECTIVES/HYPOTHESIS: Spikes in cochlear implant impedance are associated with inner ear pathology after implantation. Here, we correlate these spikes with episodes of hearing loss and/or vertigo, with a comparison between lateral wall and peri-modiolar electrode arrays. METHODS: Seven hundred seventy recipients of Cochlear's slim-straight, lateral wall electrode (CI422), or peri-modiolar (CI512) electrode were investigated for impedance spikes. Impedance fluctuations were defined as a median rise of ≥ 4 kΩ across all intracochlear electrodes from baseline measurements taken 2 weeks after switch-on. Medical records were analyzed from 189 of the 770 patients. RESULTS: The slim straight, lateral wall electrode was found to spike in impedance at a significantly higher rate than the peri-modiolar array (17% vs 12%). The peri-modiolar electrode tended to spike in impedance earlier than the slim-straight electrode. Impedance spikes were found to significantly correlate with medical events (hearing loss, vertigo, or tinnitus). Overall, in the "spike" group, 42 of 75 patients (56%) demonstrated a clinical event during the impedance spike, whereas 26 of 114 patients (22%) of the "non-spike" group had a clinical event. This significant difference existed with both implant types. CONCLUSION: These results demonstrate a small, but significant increase in impedance spikes in lateral wall electrodes, and support the relationship between spikes in cochlear implant impedances and postoperative inner-ear events, including the loss of residual hearing and vertigo. Monitoring cochlear implant impedance may be a method for early detection, and so the prevention, of these events in the future.

Adjuvant agents enhance round window membrane permeability to dexamethasone and modulate basal to apical cochlear gradients.

Glucocorticoids have direct anti-inflammatory, anti-oxidant and anti-apoptotic effects on cochlear hair cells. Cochlear glucocorticoid therapy has gained particular attention for its ability to enhance the protection of residual hearing following hearing preservation cochlear implantation. Local drug delivery methods achieve high drug concentrations within the inner ear fluids but are reliant upon diffusion across the round window membrane. Diffusion has been shown to demonstrate large individual variability. This study explores the role of "adjuvant agents", which when administered with glucocorticoids, enhance inner ear absorption and distribution. Guinea pig cochleae were administered either dexamethasone alone or in combination with hyaluronic acid, histamine, or combination histamine and hyaluronic acid, targeted at the round window membrane. Control subjects received saline. Perilymph was sampled from the cochlear apex, and basal to apical dexamethasone concentrations recorded with mass spectroscopy. Cochleae were harvested, and immunohistochemistry employed to explore dexamethasone tissue penetration and distribution. Basal to apical gradients were observed along the scala tympani, with higher dexamethasone concentrations observed at the cochlear base. Gradients were more pronounced and uniform when administered on a hyaluronic acid sponge, while histamine increased absolute concentrations reaching the inner ear. Tissue penetration correlated with perilymph concentration. Our results demonstrate that adjuvant agents can be employed to enhance dexamethasone absorption and distribution in the inner ear, thus proposing therapeutic strategies that may enhance steroid facilitated hearing protection.

A comparison of cochlear distribution and glucocorticoid receptor activation in local and systemic dexamethasone drug delivery regimes.

Local and systemically delivered glucocorticoids are commonly administered to protect the cochlea against damage associated with a variety of insults. There is reason to believe that dexamethasone administered by these routes may arrive at cochlear target sites via different pathways. Clinically, there is a lack of clarity as to which route is more effective in any specific circumstance. This study explores dexamethasone distribution within the guinea pig cochlea following local and systemic delivery methods. A combination of mass spectroscopy and immunohistochemistry were employed to compare both perilymph distribution, tissue uptake and receptor activation. Local administration of dexamethasone to the round window membrane resulted in greater perilymph concentrations, with a basal to apical gradient that favours the cochlear base. Tissue immunofluorescence was intimately related to perilymph concentration following local administration. Systemic administration resulted in much lower perilymph concentrations, with an inverse basal to apical gradient favouring the cochlear apex. Lower perilymph concentrations following systemic administration were associated with minimal tissue immunofluorescence. Despite this, GR activation of the SGNs was equivalent in both administration regimes. These results bring into question the efficacy of measuring perilymph concentrations alone as a surrogacy for dexamethasone distribution and activity in the cochlea, suggesting that the steroid ligand may arrive at its target receptor via alternative pathways. Our results suggest an equivalence in efficacy between local and systemic administration routes early after drug delivery, when the ultimate outcome of GR activation is the goal.