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INTRODUCTION: The neural response telemetry (NRT) is a standard procedure in cochlear implantation mostly used to determine the functionality of implanted device and to check auditory nerve responds to the stimulus. Correlation between NRT measurements and subjective threshold (T) and maximum comfort (C) levels has been reported but results are inconsistent, and it is still not clear which of the NRT measurements could be the most useful in predicting fitting levels. PURPOSE: In our study we aimed to investigate which NRT measurement corresponds better to fitting levels. Impedance (IMP), Evoked Action Potential (ECAP) threshold and amplitude growth function (AGF) slope values were included in the study. Also, we tried to identify cochlear area at which the connection between NRT measurements and fitting levels would be the most pronounced. MATERIALS AND METHODS: Thirty-one children implanted with Cochlear device were included in this retrospective study. IMP, ECAP thresholds and AGF were obtained intra-operatively and 12 months after surgery at electrodes 5, 11 and 19 as representative for each part of cochlea. Subjective T and C levels were obtained 12 months after the surgery during cochlear fitting. RESULTS: ECAP thresholds obtained 12 months after surgery showed statistically significant correlation to both T and C levels at all 3 selected electrodes. IMP correlated with C levels while AGF showed tendency to correlate with T levels. However, these correlations were not statistically significant for all electrodes. CONCLUSION: ECAP threshold measurements correlated to T and C values better than AGF slope and IMP. Measurements obtained twelve months after surgery seems to be more predictive of T and C values compared to intra-operative measurements. The best correlation between ECAP threshold and T and C values was found at electrode 11 suggesting NRT measurements at mid-portion cochlear region to be the most useful in predicting fitting levels.

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BACKGROUND: Hearing loss is a common sequala of Streptococcus suis (S. suis) meningitis, but few have addressed cochlear implantation (CI) candidates with S. suis meningitis. OBJECTIVES: To assess the clinical characteristics and CI postoperative outcomes in S. suis meningitis patients. MATERIAL AND METHODS: Eight S. suis meningitis patients underwent CI at Sun Yat-sen Memorial Hospital between 2020 and 2023. Control groups included (1) non-Suis meningitis patients (n = 12) and (2) non-meningitis patients (n = 35). Electrode impedances and neural response telemetry (NRT) thresholds were recorded at one month after surgery. The auditory performance-II (CAP) and speech intelligibility rating (SIR) were recorded at the last visit. RESULTS: CAP scores of S. suis meningitis patients were significantly lower than those of non-Suis meningitis and non-meningitis patients (p = .019; p<.001). And NRT thresholds of S. suis meningitis patients were higher than those of non-Suis meningitis and non-meningitis patients (p = .006; p = .027). CONCLUSIONS AND SIGNIFICANCE: It is recommended for S. suis meningitis CI candidates to undergo CI promptly after controlling infection, preferably within four to six weeks. CI users with S. suis meningitis tend to exhibit suboptimal hearing rehabilitation outcomes, possibly associated with the more severe damage on spiral ganglion cells after S. suis meningitis.

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BACKGROUND AND OBJECTIVES: To analyze mapping changes in dynamic range (DR) and neural response threshold (NRT) as prognostic factors for cochlear implant (CI). To analyze whether postoperative speech perception performance could be predicted using DR change and initial NRT. SUBJECTS AND METHODS: The speech comprehension data of 33 patients with CI were retrospectively analyzed after 1, 3, 6, and 12 months of device use. All subjects were adult, postlingually hearing-impaired, and Cochlear Nucleus CI users. Speech perception performance was evaluated using aided pure tone audiometry, consonant, vowel, one-word, two-word, and sentence tests. RESULTS: The averages of initial NRT and DR changes were 197.8±25.9 CU (104-236) and 22.2±18.4 CU (-15-79), respectively. The initial DR was 40.8±16.6 CU. The postoperative DR was 50.3±16.4 CU at 3 months, 58±12.3 CU at 6 months, and 62.9±10.4 CU at 12 months. A gradual increase of DR was observed during the first year of CI. Compared with the initial DR, significant increases in DR were observed at 3 (p<0.05), 6 (p<0.001), and 12 (p<0.001) months. Compared with initial speech performance outcomes, a significant gain in all performance outcomes was achieved at 12 months (p<0.001). CONCLUSIONS: Patients with low NRT after CI surgery could initially set DR to a wider range and had better final speech perception outcomes. Conversely, patients with high NRT after CI surgery had to set up a gradual increase in DR while adjusting the T-C level, and the final speech perception outcomes were worse. DR and NRT, the main CI mapping variables, can help predict prognosis related to speech perception outcomes after CI surgery. In conclusion, the post-CI speech perception is better with a lower initial NRT, wider final DR, or younger age.

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Spiral ganglion neurons (SGNs) facilitation properties can be recorded utilizing electrically evoked compound action potential (ECAP). While intracochlear variation of the ECAP threshold in relation to its electrode channel is reported, no study investigated its impact on facilitation. In this study, we quantified intracochlear variation of the facilitation properties in cochlear implants (CI) using ECAPs. We hypothesized that the facilitation effect is dependent on the electrode channel and its ECAP threshold. Therefore, ECAPs were recorded in 23 CI subjects. For each subject, five default (channel-derived) and up to two additional (threshold-derived) stimulation sites were defined. Facilitation was quantified by the paradigm introduced by (Hey et al., 2017) with optimized parameter settings. For each channel the maximum facilitated amplitude was determined by a series of ECAP measurements. A linear mixed-effects model was used to investigate the impact of the electrode channel and ECAP threshold on the maximum facilitated amplitude. The maximum facilitated amplitude was found to be dependent on the ECAP threshold and independent on the electrode channel. We conclude that the facilitation paradigm is a useful and feasible tool to gain local information on the SGNs temporal processing patterns.

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Aim and Objectives: This study is designed to compare the Intra Operative Neural Response Telemetry (NRT) results with Post-Operative NRT results of the cochlear implanted children, to assess the importance of Intra Operative NRT thresholds in device activation and/or switch on of the audio processor and to evaluate the importance of Intra and post operative AutoNRT results in predicting behavioural thresholds during mapping of prelingual Cochlear Implanted children. Materials and methods: A total of thirty (30) children (16 boys, 14 girls) with congenital Bilateral (B/L) severe to profound Sensorineural hearing loss (SNHL) were included in this study. Children between the age range of 12 to 60 months were participated in this study. All the participants were implanted with Nucleus 24 cochlear implant system. In each patient, the intra operative NRT-thresholds were measured for all 22 active electrodes. Then Intra Operative NRT thresholds were correlated with Post-Operative NRT thresholds at the time of switch on and the behavioural map after six months of switch on of the device (Audio Processor). Results: There is a significant enhancement observed in thresholds of postoperative NRT responses which were raised or absent during intraoperative session. There is a gain in NRT thresholds marked after 6 months of postoperative follow up in comparison with first measurement at the time of Switch On of the device but the change not that significant. During postoperative mapping, there was a significant positive correlation noticed between neural response telemetry level measurements and behavioural threshold level. Conclusion: Absent or elevated NRT responses during intraoperative testing for some electrodes especially basal electrodes does not mean that electrode is out of order or outside the cochlea, because an improvement in NRT thresholds usually occurs postoperatively. In case of children with congenital B/L severe to profound SNHL, the NRT values have a very useful role in predicting the behavioural thresholds. Combination of NRT values with behavioural thresholds and observations of Auditory Verbal Therapist can help in providing best suitable Map to the recipient. Supplementary Information: The online version contains supplementary material available at 10.1007/s12070-022-03284-x.

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OBJECTIVE: To evaluate the role of intraoperative radiographs to confirm electrode position following pediatric cochlear implantation (CI). STUDY DESIGN: Retrospective chart review. SETTING: Single tertiary care pediatric center. METHODS: A retrospective chart review was conducted, including all pediatric patients undergoing CI at UPMC Children's Hospital of Pittsburgh over a 13-year period. RESULTS: We identified 326 patients undergoing 492 procedures. Across the cohort, there were 7 cases that required intraoperative electrode reinsertion due to malposition or presumed malposition. For 6 of the 7 cases, intraoperative X-ray identified electrode malposition. Neural response telemetry (NRT) testing was also abnormal for 4 of these cases prior to reinsertion. Implantation of Cochlear's Slim Modiolar electrode was associated with an abnormal perioperative X-ray (odds ratio [OR]: 9.2, p = 0.03) and increased change in management (OR: 9.2, p = 0.03) compared to Cochlear's Contour Advance (CA). Incidence of abnormal X-rays was 1.24% overall, 4% in the Slim Modiolar group, and 0.3% in the CA group. The Slim Modiolar electrode accounted for 4 of 7 cases requiring reinsertion, and in all 4 of these cases, electrode fold-over was identified on the X-ray. NRT was normal in 1 of these 4 cases. CONCLUSION: The use of Cochlear's Slim Modiolar electrode was associated with a significantly increased risk of abnormal intraoperative X-ray compared to the CA electrode. Given the risk of fold-over with routine insertion and normal electrical testing using the Slim Modiolar electrode, we recommend routine use of intraoperative skull X-ray to confirm electrode position.

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OBJECTIVE: To evaluate the relationship between intraoperative neural response telemetry (NRT) and postoperative auditory testing outcomes in children. STUDY DESIGN: Retrospective study. SETTING: Tertiary-care academic center. METHODS: Children who underwent cochlear implantation using the Cochlear Corporation device between 2010 and 2019 were included. Associations of average NRT and the slope of amplitude with postoperative auditory outcomes including functional auditory measure Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS), and speech perception testing (consonant-nucleus-consonant [CNC], Pediatric AzBio [BABY BIO], Hearing In Noise Test [HINT], and Northwestern University Children's Perception of Speech [NU-CHIPS]), measured between 6 and 57 months after implantation, were assessed using Spearman's rank correlation (ρ). RESULTS: Thirty-eight patients (19 female, 19 male) and 54 ears were included. The median age of implantation was 20.6 months (range 9.6 months to 10.6 years). Eight (21%) children had neurologic disorders such as stroke, epilepsy, cerebral palsy, and other causes. Thirteen (34%) children had connexin mutations. Average NRT was not significantly correlated with postoperative auditory outcomes (IT-MAIS [ρ = -0.08, p = .74], CNC [ρ = 0.19, p = .32], BABY BIO [ρ = 0.21, p = .29], HINT [ρ = 0.05, p = .83]) and NU-CHIPS (ρ = 0.21, p = .28). The average slopes of amplitude and comfort level were not strongly correlated with any auditory outcomes (p > .05). CONCLUSIONS: Intraoperative NRT was not correlated with any postoperative functional auditory outcomes. Patient counseling should include discussions that a subpar intraoperative cochlear response does not preclude favorable speech and auditory outcomes.

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Recent technological advances in cochlear implant (CI) telemetry have enabled, for the first time, CI users to perform cochlear health (CH) measurements through self-assessment for prolonged periods of time. This is important to better understand the influence of CH on CI outcomes, and to assess the safety and efficacy of future novel treatments for deafness that will be administered as adjunctive therapies to cochlear implantation. We evaluated the feasibility of using a CI to assess CH and examined patterns of electrode impedances, electrically-evoked compound action potentials (eCAPs) and electrocochleography (ECochGs), over time, in a group of adult CI recipients. Fifteen subjects were trained to use the Active Insertion Monitoring tablet by Advanced Bionics, at home for 12 weeks to independently record impedances twice daily, eCAPs once weekly and ECochGs daily in the first week, and weekly thereafter. Participants also completed behavioral hearing and speech assessments. Group level measurement compliance was 98.9% for impedances, 100% for eCAPs and 99.6% for ECochGs. Electrode impedances remained stable over time, with only minimal variation observed. Morning impedances were significantly higher than evening measurements, and impedances increased toward the base of the cochlea. eCAP thresholds were also highly repeatable, with all subjects showing 100% measurement consistency at, at least one electrode. Just over half of all subjects showed consistently absent thresholds at one or more electrodes, potentially suggesting the existence of cochlear dead regions. All subjects met UK NICE guidelines for cochlear implantation, so were expected to have little residual hearing. ECochG thresholds were, unsurprisingly, highly erratic and did not correlate with audiometric thresholds, though lower ECochG thresholds showed more repeatability over time than higher thresholds. We conclude that it is feasible for CI users to independently record CH measurements using their CI, and electrode impedances and eCAPs are promising measurements for objectively assessing CH.

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Objective:To explore the feasibility of using the threshold of neural response telemetry（NRT） to guide postoperative machine adjustment by analyzing the regularity and correlation between the threshold of subjective behavior test and NRT in cochlear implant patients with normal cochlear morphology and inner ear malformation. Methods:Thirty cochlear implant patients with normal cochlear morphology and 12 cochlear implant patients with inner ear malformation were selected for NRT test and subjective behavior test, respectively. Electrode 1 representing high frequency, electrode 11 representing medium frequency and electrode 22 representing low frequency were selected to analyze the correlation between NRT threshold and T value and C value. Results:The mean NRT threshold values of the cochlear normal group and the inner ear malformation group were both greater than T value, close to and slightly smaller than C value. The T value, C value and NRT threshold of the inner ear malformation group were slightly higher than those of the cochlear normal group. The NRT thresholds of high, middle and low frequency bands were significantly correlated with C and T values in the normal cochlear group and the inner ear malformation group. Compared with the normal cochlear group, the regression coefficients B of NRT threshold and T value in the high, medium and low frequency groups were 20.90%, 3.02%, 9.68%, and the K coefficients were 13.01%, 3.92%, 5.28%. The regression coefficients B of NRT threshold and C value of the two groups were 15.74%, 2.51%, 0.53%, and K were 14.44%, 0.24%, 4.09%, respectively. It can be seen that the correlation between NRT threshold and T value and C value of the two groups was significantly different in the high frequency band, but similar in the low and middle frequency band. Conclusion:The NRT threshold is significantly correlated with the threshold of subjective behavior test. The linear regression equation obtained can be used to guide the cochlear implant tuning machine, especially for the high frequency band T and C values of patients with inner ear malformation implantation. Different regression equations should be used to estimate the T and C values of patients with normal cochlea, so as to obtain more accurate T and C values.

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OBJECTIVE: The objective of this study is to evaluate the relationship between intraoperative neural response telemetry (NRT) and postoperative Threshold (T) and Comfort (C) levels and their correlation over time after cochlear implantation (CI). METHODS: A retrospective chart review was conducted of patients less than 18 years of age who had CI with a Cochlear™ device and NRT at an academic center from 2010 to 2019. Data collected included demographics, extrapolated NRT threshold (tNRT) and slope of amplitude for electrodes 1, 6/7, 11/12, 16, and 22, and postoperative T and C levels at initial activation and 1 month, 3 months, and 1 year post-activation. Associations between T and C levels and slope of amplitude or tNRT were assessed using Spearman's rank correlation. RESULTS: 39 patients (65 CIs) were included. Intraoperative tNRT correlated strongly with T and C levels at 1 month, 3 months, and 1 year post-activation on nearly all electrodes. Electrodes 6/7 and 11/12 at 3 months and electrodes 6/7 at 1 year did not correlate with T and C levels. There was no significant relationship between the slope of amplitude for nearly all electrodes and the T or C levels post-activation. CONCLUSION: NRT is invaluable in children, with significant correlation found between tNRT and T and C levels over time on nearly all electrodes. There are changes in T and C levels in electrodes 6/7 and 11/12 over time, and close surveillance is beneficial to tailor programming as needed.

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Objectives: This study sought to characterize the influence of inner ear malformations (IEMs) on intraoperative electrically evoked compound action potential (ECAP) and auditory performance to better understand the underlying pathophysiology related to variabilities in cochlear implant (CI) outcomes that individuals with malformed cochlea may present. Methods: The medical records of 222 ears implanted with Cochlear Nucleus CI were reviewed. Of the total, 64 ears had radiologic evidence of IEMs, and 158 ears were normal. Individuals with IEMs were grouped based on the severity of anomalies; 38 had mild IEMs (e.g., enlarged vestibular aqueduct, incomplete partition type II, etc.) and 26 had severe IEMs (e.g., cochlear nerve hypoplasia, common cavity, etc.). Intraoperative ECAP thresholds obtained via neural response telemetry (NRT) and the categories of auditory performance (CAP) scores measured at 12 months postoperative were compared and correlated. Results: Absent ECAP responses were more apparent in the IEM group. ECAP thresholds were significantly elevated in the severe IEM group, while the mild IEM group had ECAP thresholds comparable to the normal group. The mild IEM group achieved CAP scores similar to the normal control. Patients in the severe IEM group showed significantly lower CAP scores at 12 months postoperative. Significant negative relationships existed between ECAP thresholds and CAP scores obtained from all subjects. Conclusion: Measurable ECAP responses and NRT thresholds varied across groups. The inverse relationship between NRT thresholds and CAP scores may suggest that electrophysiological responses measured during surgery may potentially be indicative of postoperative performance in our CI population. Level of Evidence: 2b.

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INTRODUCTION: Cochlear implants allow measures of neural function, through Neural response telemetry (NRT) and Auditory nerve recovery function (REC). These help in programming the speech processor and understanding the auditory system. However, not many studies have evaluated and compared these in different regions of the cochlea. OBJECTIVE: Comparing NRT and REC in different regions of the cochlea. METHODS: Cross-sectional, descriptive and prospective. NRT and REC (through the function of T0 - absolute refractory period, A - amplitude and TAU - time constant of the relative refractory period parameters) were evaluated, in three groups according to the stimulated electrode of the cochlea: apical, medial and basal. RESULTS: 26 adult patients were evaluated, 2 bilateral, totalling 28 ears. Data analysis showed no statistically significant difference between NRT between medial and basal but showed between apical and medial and apical and basal. For T0, there was a significant difference between medial and basal; for A, there was a significant difference between apical and basal and also medial and basal; and for TAU, there was no significant difference. CONCLUSION: There was a statistically significant difference in NRT and REC when compared between different regions of the cochlea.

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OBJECTIVES: To identify whether mismatched bilateral cochlear implants compromise balanced stimulation of the two auditory nerves and establish asymmetric hearing in children. METHODS: Behavioural and electrophysiological measures were completed in 47 children receiving bilateral CIs in the same surgery (simultaneously): 27 children received a peri­modiolar N24RE array in one ear and a 422 anti-modiolar array in the other (experimental group) and 20 children received 2 peri­modiolar arrays (control group). Differences in current levels between the two devices were measured by electrically evoked compound action potentials (ECAPs) at the time of surgery. These data were compared with minimum and maximum comfortably loud levels programmed in each speech processor (T-levels, C-levels, respectively) after 12 months of bilateral CI use. Asymmetries in functional hearing between arrays were measured in open set speech perception testing between 3 to 5 years of CI use. RESULTS: Higher current levels were required from the anti-modiolar than peri­modiolar array to evoke balanced interaural ECAP amplitudes (mismatched group: mean ± SD difference: -9.9 ± 22.6; matched group: -0.8 ± 26.5). This difference was larger in the experimental group than control group (t = -2.51; p = 0.016) and remained constant with increases in current level from ECAP threshold to maximum amplitudes (dynamic range) in many but not all children in both groups. T and C-levels were poorly predictive of levels needed to evoke balanced ECAP amplitudes in children with mismatched devices (F(1, 312) = 1.3, p = 0.263). Speech perception scores were more asymmetric between ears in children using bilateral mismatched arrays (mean ± SD: 73.8 ± 16.4 at the peri­modiolar array; 57.7 ± 26.4 at the anti-modiolar array), compared to children with bilateral matched arrays (right ear: 78.0 ± 10.4; left ear: 74.9 ± 13.5). CONCLUSION: Higher current level requirements at the anti-modiolar array compared to the peri­modiolar array in children with bilateral mismatched CIs are not fully accounted for in device programming. Mismatched electrodes in children receiving bilateral cochlear implants increases the risk of asymmetric hearing.

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Electrically evoked auditory potentials have been used to predict auditory thresholds in patients with a cochlear implant (CI). However, with exception of electrically evoked compound action potentials (eCAP), conventional extracorporeal EEG recording devices are still needed. Until now, built-in (intracorporeal) back-telemetry options are limited to eCAPs. Intracorporeal recording of auditory responses beyond the cochlea is still lacking. This study describes the feasibility of obtaining longer latency cortical responses by concatenating interleaved short recording time windows used for eCAP recordings. Extracochlear reference electrodes were dedicated to record cortical responses, while intracochlear electrodes were used for stimulation, enabling intracorporeal telemetry (i.e., without an EEG device) to assess higher cortical processing in CI recipients. Simultaneous extra- and intra-corporeal recordings showed that it is feasible to obtain intracorporeal slow vertex potentials with a CI similar to those obtained by conventional extracorporeal EEG recordings. Our data demonstrate a proof of concept of closed-loop intracorporeal auditory cortical response telemetry (ICT) with a cochlear implant device. This research breaks new ground for next generation CI devices to assess higher cortical neural processing based on acute or continuous EEG telemetry to enable individualized automatic and/or adaptive CI fitting with only a CI.

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Introduction: In patients with normal inner ear architecture at imaging and who received a prior cochlear implant (CI) without difficulty, the expectation is that replacing a failed CI should be straightforward. Here, we present a patient in whom an unusual complication (to our knowledge, not reported) was encountered. Methods: Review of audiological and medical and surgical records and imaging data. Results: Re-implantation went well except no electrically elicited compound action potential could be elicited via any electrode. The replacement CI did not provide any auditory perception. CT showed the electrode array to enter the cochlea with three electrodes, but all other electrodes extended toward the Eustachian tube. Subsequent re-implantation into the scala vestibuli yielded excellent performance with the CI. Conclusion: Mechanical forces, such as from a CI array, can erode the hardest bone over time. This possibility should be a consideration in patients who are undergoing CI device replacement.

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Abstract Introduction Cochlear implants (CIs) enable objective measures of the neural function in implanted patients through the measurements of the neural response telemetry (NRT) and of the Auditory nerve Recovery Function (REC). These measurements help in programming the speech processor and understanding the auditory system. Objective To compare the NRT and the REC in prelingual and postlingual implanted patients. Methods An observational, descriptive and prospective study was carried out. The NRT and the REC (through the T0, A, and tau parameters) were evaluated in individuals submitted to CI surgery, who were divided into two groups: prelingual and postlingual patients. Results In total, 46 patients were evaluated. Data analysis showed no statistically significant difference between the NRT measurements and the T0, A, and Tau of the REC in the comparison between the two groups, except for the NRT in the basal cochlear region. Conclusion There was no statistically significant difference in the REC in pre- and postlingual patients.

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Introduction Cochlear implants (CIs) enable objective measures of the neural function in implanted patients through the measurements of the neural response telemetry (NRT) and of the Auditory nerve Recovery Function (REC). These measurements help in programming the speech processor and understanding the auditory system. Objective To compare the NRT and the REC in prelingual and postlingual implanted patients. Methods An observational, descriptive and prospective study was carried out. The NRT and the REC (through the T0, A, and tau parameters) were evaluated in individuals submitted to CI surgery, who were divided into two groups: prelingual and postlingual patients. Results In total, 46 patients were evaluated. Data analysis showed no statistically significant difference between the NRT measurements and the T0, A, and Tau of the REC in the comparison between the two groups, except for the NRT in the basal cochlear region. Conclusion There was no statistically significant difference in the REC in pre- and postlingual patients.

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OBJECTIVES: The electrically evoked compound action potential (ECAP) is widely used in clinical to reflect the functional states of the auditory nerve in cochlear implant (CI) recipients, especially in pediatric CI users. Currently, the software can automatically provide the ECAP threshold, which is convenient and not affected by the subjective judgement of the clinicians. However, it remains unclear whether the correlations between human and computer decisions for ECAP threshold can be affected by auditory nerve functional states, which is also the main purpose of our present study. METHODS: Intracochlear electrical stimulation, which can decrease the excitability of the auditory nerve, was used to change the auditory nerve functional states of guinea pigs. Ten normal-hearing guinea pigs were implanted with CIs unilaterally. ECAPs were recorded both before and after the electrical stimulation, representing different functional states of the auditory nerve. Forward masking (FwdMsk) and alternating polarity (AltPol), two most commonly-used artifact-reduction methods, were applied to the measurements. All measurements recorded by the software were saved for computer and human analysis with linear regression and visual detection methods. RESULTS: The correlations between human and computer performance in the peak-picking process were not affected by auditory nerve states and artifact-reduction methods. However, complicated findings were observed for ECAP threshold. With FwdMsk utilized, weaker correlations between human and computer performance were observed in abnormal state compared to those in normal state. Regardless of the functional states of the auditory nerve, the results revealed stronger correlations in AltPol than those in FwdMsk. Furthermore, when compared with human decision, computer linear-regression threshold (C-LRT) was always less accurate than computer visual-detection threshold (C-VDT), which was not affected by auditory nerve states. CONCLUSIONS: (1) the functional states of the auditory nerve can definitely affect the correlations between human and computer decisions for ECAP threshold, but the impact is limited to the FwdMsk method; (2) AltPol can produce stronger correlations compared with FwdMsk, which is not affected by auditory nerve states; and (3) regardless of the auditory nerve states, C-VDT can always show higher consistency with human decision, while C-LRT reveals more variability.

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INTRODUCTION: Precurved cochlear implant (CI) electrode arrays were developed in an attempt to improve the auditory outcome of cochlear implantation, which varies greatly. The recent CI532 (Cochlear Corp., Sydney, Australia) may offer further advantages as its electrode array is thinner than previous precurved CI electrode arrays. The aims here were to investigate 1-year postoperative speech recognition, intraoperative electrically evoked compound action potentials (ECAPs), and their possible relation in patients implanted with a CI532 or its predecessor CI512. METHODS: A retrospective analysis of data from 63 patients subjected to cochlear implantation at the Karolinska University Hospital, Sweden, was performed. Speech recognition of the implanted ear was evaluated using phonemically balanced monosyllabic Swedish words at 65 dB SPL. ECAPs were evaluated using the intraoperative ECAP threshold across ≥8 electrodes generated by the automated neural response telemetry of the CI. RESULTS: The median aided speech recognition score (SRS) 1 year after implantation was 52% (quartile 1 = 40%, quartile 3 = 60%, n = 63) and did not differ statistically significantly between patients with CI512 (n = 38) and CI532 (n = 25). The mean ECAP threshold was 188 CL (current level; SD = 15 CL, n = 54) intraoperatively and did not differ statistically significantly between patients with CI512 (n = 32) and CI532 (n = 22), but the threshold for each electrode varied more between patients with a CI512 (p < 0.0001). A higher mean ECAP threshold was associated with a worse SRS (Spearman's ρ = -0.46, p = 0.0004, n = 54). The association remained among those with a CI512 (Spearman's ρ = -0.62, p = 0.0001, n = 32) when stratified by CI electrode array. CONCLUSION: No statistically significant difference in speech recognition 1 year after cochlear implantation or in mean threshold of ECAP intraoperatively was found between patients with a CI512 and the more recent, slim CI532, but the ECAP thresholds varied more between those with a CI512. A statistically significant association between SRS and mean ECAP threshold was found, but stratified analysis suggests that the association may be true only for patients with a CI512.

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Auditory nerve fibers' (ANFs) refractoriness and facilitation can be quantified in electrically evoked compound action potentials (ECAPs) recorded via neural response telemetry (NRT). Although facilitation has been observed in animals and human cochlear implant (CI) recipients, no study has modeled this in human CI users until now. In this study, recovery and facilitation effects at different masker and probe levels for three test electrodes (E6, E12 and E18) in 11 CI subjects were recorded. The ECAP recovery and facilitation were modeled by exponential functions and the same function used for +10 CL masker offset condition can be applied to all other masker offsets measurements. Goodness of fit was evaluated for the exponential functions. A significant effect of probe level was observed on a recovery time constant which highlights the importance of recording the recovery function at the maximum acceptable stimulus level. Facilitation time constant and amplitude showed no dependency on the probe level. However, facilitation was stronger for masker level at or around the threshold of the ECAP (T-ECAP). There was a positive correlation between facilitation magnitude and amplitude growth function (AGF) slope, which indicates that CI subjects with better peripheral neural survival have stronger facilitation.

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