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Objective: Cochlear Implant (CI) programming based on subjective psychophysical fine-tuning of loudness scaling involves active participation and cognitive skills and thus may not be appropriate for difficult-to-condition populations. The electrically evoked stapedial reflex threshold (eSRT) is an objective measure that is suggested to provide clinical benefit to CI programming. This study aimed to compare speech reception outcomes between subjective and eSRT objectively determined CI maps for adult MED-EL recipients. The effect of cognitive skills on these skills was further assessed., Methods: Twenty-seven post lingually hearing-impaired MED-EL CI recipients were recruited, 6 with mild cognitive impairment (MCI- 4 male, 79 years ± 5), 21 with normal cognitive function (5 male, 63 years ± 12). Two MAPs were generated: a subjective MAP and an objective MAP in which eSRTs determined maximum comfortable levels (M-Levels). Participants were randomly divided into two groups. Group A trialled the objective MAP for two weeks before returning for outcome assessment. During the following two weeks, Group A trialled the subjective MAP before returning for outcome assessment. Group B trialled MAPs in reverse. Outcome measures included the Hearing Implant Sound Quality Index (HISQUI), Consonant-Nucleus-Consonant (CNC) word test, and Bamford-Kowal-Bench Speech-in-Noise (BKB-SIN) test., Results: eSRT based MAPS were obtained in 23 of the participants. A strong relationship was demonstrated between global charge between eSRT-based and psychophysical-based M-Levels (r = 0.89, p < .001). The Montreal Cognitive Assessment for the Hearing Impaired (MoCA-HI) testing identified 6 CI recipients with MCI (MoCA-HI total score ≤23). The MCI group was older (63, 79 years), but were not otherwise different in sex, duration of hearing loss or duration of CI use. For all patients, no significant differences were found for sound quality or speech in quiet scores between eSRT-based and psychophysical-based MAPs. However, psychophysically determined MAPs showed significantly better speech-in-noise reception (6.74 vs 8.20-dB SNR, p = .34). MoCA-HI scores showed a significant, moderate negative correlation with BKB SIN for both MAP approaches (Kendall's Tau B, p = .015 and p = .008), with no effect on the difference between MAP approaches., Conclusion: Results indicate eSRT-based methods provide poorer outcomes than psychophysical-based method. While speech-in-noise reception is correlated with MoCA-HI score, this affected both behaviourally and objectively determined MAPs. The results suggest fair confidence in the eSRT-based method as a guide for setting M-Level for difficult-to-condition CI populations in simple listening conditions., Competing Interests: It is disclosed that one of the authors is a clinical specialist working for MED-EL Australasia. This does not alter our adherence to PLOS ONE policies on sharing data and materials., (Copyright: © 2023 Yiannos et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

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., Competing Interests: The authors disclose no conflict of interest., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of Otology & Neurotology, Inc.)

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., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

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.

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.

Objectives/hypothesis: Cochlear implant surgery now aims to preserve residual low frequency hearing. The current research explores whether fluctuations in the electrical impedance of cochlear implant electrodes may act as a biomarker for pathological changes that lead to the delayed loss of residual hearing., Study Design: Secondary analysis of a double-blinded randomized trial, where methylprednisolone was administered intravenously before cochlear implantation with a view to preserving residual hearing., Methods: Seventy-four patients with residual hearing after cochlear implant surgery were investigated for an impedance "spike," defined as a median rise of ≥4 kΩ across all electrodes from the baseline measurements. Spikes were related to objective and subjective hearing loss, dizziness, and tinnitus., Results: An impedance spike occurred in 14% (10/74) of enrolled patients. Three months after surgery, five patients exhibited spikes and three of these patients had a total loss of their residual hearing. 4.3% of the 69 patients without spikes lost residual hearing. At 1 year, 9 of 10 patients who exhibited spikes had lost all their residual hearing. 8.1% of the 37 patients who did not experience a spike lost their residual hearing. Seventy percent of patients exhibiting a spike also experienced vertigo. The administration of steroids at the time of surgery did not influence the occurrence of spikes., Conclusion: Our results suggest that there is a relationship between a spike and the loss of residual hearing. It seems that rises in impedance can reflect pathology within the inner ear and predict the future loss of residual hearing.

Near-threshold tones (targets) in noise that are preceded by cues of the same frequency or occur with a high probability are detected better than tones of other frequencies that may occur with a lower probability (probes); the better detection of targets than probes defines the attentional filter. We measured attentional filters using a cued probe-signal procedure with a two-interval forced-choice (2IFC) method in normal-hearing subjects (N = 15) and subjects with sensorineural hearing loss (SNHL; N = 14) with a range of hearing levels. Attentional filters were altered in SNHL subjects, who detected low-frequency probes as well as targets at all hearing levels and who detected high-frequency probes increasingly well with increasing hearing level. These effects were present in both intervals of the 2IFC procedure. As auditory filters measured psychophysically are typically asymmetric in subjects with SNHL, these results suggest that the signal frequencies affected by the attentional filter are governed by the shapes of the auditory filters at and around the cue frequency. The normal-hearing subjects showed the expected attentional filters in the first interval and shallower filters in the second interval, suggesting that the cue-evoked attentional process is transient. In the first interval, both low- and high-frequency probes were detected better as hearing level increased over a narrow range (from -5 to 10 dB at the target frequency), with a resultant loss of attentional filtering. This finding adds to observations of variable auditory function in individuals with clinically normal hearing thresholds established by audiometry., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: Lay the groundwork for using electrocochleography (ECochG) as a measure of cochlear health, by characterizing typical patterns of the ECochG response observed across the electrode array in cochlear implant recipients with residual hearing. Methods: ECochG was measured immediately after electrode insertion in 45 cochlear implant recipients with residual hearing. The Cochlear Response Telemetry system was used to record ECochG across the electrode array, in response to 100- or 110-dB SPL pure tones at 0.5-kHz, presented at 14 per second and with alternating polarities. Hair cell activity, as the cochlear microphonic (CM), was estimated by taking the difference (DIF) of the two polarities. Neural activity, as the auditory nerve neurophonic (ANN), was estimated by taking the sum (SUM) of the two polarities. Prior work in humans and animal studies suggested that the expected ECochG pattern in response to a 0.5-kHz pure tone is an apical-peak in CM amplitude and latency. Results: The most prevalent pattern was a peak in the DIF amplitude near the most apical electrode, with a prolongation of latency toward the electrode tip; this was found in 21/39 individuals with successful ECochG recordings. The 21 apical-peak recipients had the best low-frequency hearing. A low amplitude, long-latency DIF response that remained relatively constant across the electrode array was found in 10/39 individuals, in a group with the poorest low- and high-frequency hearing. A third, previously undescribed, pattern occurred in 8/39 participants, with mid-electrode peaks in DIF amplitude. These recipients had the best high-frequency hearing and a progressive prolongation of DIF latency around the mid-electrode peaks consistent with the presence of discrete populations of hair cells. Conclusions: The presence of distinct patterns of the ECochG response with relationships to pre-operative hearing levels supports the notion that ECochG across the electrode array functions as a measure of cochlear health.