Neural Response Telemetry Thresholds Research Articles

Prediction of Cochlear Implant Fitting by Machine Learning Techniques.

This study aimed to evaluate the differences in electrically evoked compound action potential (ECAP) thresholds and postoperative mapping current (T) levels between electrode types after cochlear implantation, the correlation between ECAP thresholds and T levels, and the performance of machine learning techniques in predicting postoperative T levels. Retrospective case review. Tertiary hospital. We reviewed the charts of 124 ears of children with severe-to-profound hearing loss who had undergone cochlear implantation. We compared ECAP thresholds and T levels from different electrodes, calculated correlations between ECAP thresholds and T levels, and created five prediction models of T levels at switch-on and 6 months after surgery. The accuracy of prediction in postoperative mapping current (T) levels. The ECAP thresholds of the slim modiolar electrodes were significantly lower than those of the straight electrodes on the apical side. However, there was no significant difference in the neural response telemetry thresholds between the two electrodes on the basal side. Lasso regression achieved the most accurate prediction of T levels at switch-on, and the random forest algorithm achieved the most accurate prediction of T levels 6 months after surgery in this dataset. Machine learning techniques could be useful for accurately predicting postoperative T levels after cochlear implantation in children.

Cochlear implantation in patients with Streptococcus suis meningitis: clinical characteristics and postoperative evaluation

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.

Cochlear Implant Activation in the Immediate Postoperative Period in the Operating Room.

Introduction Cochlear implant (CI) activation usually takes place at ∼ 30 days postoperative (PO). In our service, CI surgery is performed with local anesthesia and sedation, so activation is possible with the patient's cooperation, immediately after the CI surgery, still in the operating room (OR). Objective The objective of the present study was to provide the patient with hearing experience with the CI and to assess auditory perception immediately after surgery while still in the OR, as well as to compare impedance telemetry (IT), neural response telemetry (NRT), and comfort (C) level at two moments: in the OR and at the definitive activation, ∼ 30 days PO. Methods Nine adult patients (12 ears) with acquired (postlingual) deafness were included. Auditory perception was evaluated through the Ling Six Sound Check, musical instruments, and clapping, presented in two different programming maps, elaborated using t-NRT, and comparing IT, NRT, and C level between the two moments. Results We observed that while still in the OR, the patient can already present auditory detection and recognition responses. The values of IT, NRT threshold (t-NRT), and C on both dates differed, with statistical significance. Conclusion We concluded that it is possible to provide the patient with an auditory experience with the CI immediately after surgery, and that the auditory experience and the values of electrode IT, NRT, and C vary significantly between the two moments.

Is the spread of excitation different between adults and children cochlear implants users?

While cochlea is adult size at birth, etiologies and bone density may differ between children and adults. Differences in neural response thresholds (tNRT) and the spread of excitation (SOE) width may impact the use of artificial intelligence algorithms in speech processor fitting. To identify whether neural response telemetry threshold and spread of excitation width are similar in adults and children. Retrospective cross-sectional study approved by the Ethical Board. Intraoperative tNRT and SOE recordings of consecutive cochlear implant surgeries in adults and children implanted with Cochlear devices (Cochlear™, Australia) were selected. SOE was recorded on electrode 11 (or adjacent, corresponding to the medial region of the cochlea) through the standard forward-masking technique in Custom Sound EP software, which provides SOE width in millimeters. Statistical comparison between adults and children was performed using the Mann-Whitney test (p ≤ 0.05). Of 1282 recordings of intraoperative evaluations, 414 measurements were selected from children and adults. Despite the tNRT being similar between adults and children, SOE width was significantly different, with lower values in children with perimodiolar arrays. Besides, it was observed that there is a difference in the electrode where the SOE function peak occurred, more frequently shifted to electrode 12 in adults implanted. In straight arrays, there was no difference in any of the parameters analyzed on electrode 11. Although eCAP thresholds are similar, SOE measurements differ between adults and children in perimodiolar electrodes.

Comparison of Perioperative Electrophysiological Measurements and Postoperative Results in Cochlear Implantation with a Slim Straight Electrode

This research aims to determine whether a neural response telemetry (NRT) threshold determines the success of surgery. Furthermore, we examined whether the patient’s age, the etiology of their hearing loss, the depth of the electrode insertion, and a slow electrode insertion affect the result of postoperative speech audiometry (PSA). A total of 23 patients that had operations in a tertiary medical centre were included in the research. All of them received a slim straight electrode that was inserted through the round window into the lateral part of scala tympani The duration of the insertion was consistently 2 min in 52.2% and less than 2 min in 47.8% of cases. Statistical analyses were performed in the IBM SPSSTM program. Patients that were diagnosed with sensorineural hearing loss (SNHL) had statistically lower average NRT threshold values in comparison to patients diagnosed with otosclerosis (t = 3.069; p = 0.034). The depth of electrode insertion is inversely proportional to the average of all NRT thresholds (r = −0.464; p = 0.026). No correlation was found between slow electrode insertion and postoperative average values of tone audiometry (U = 44.000; p = 0.300). No statistically significant correlation could be drawn between the average of all NRT thresholds and postoperative speech audiometry (rho = −0.070; p = 0.751).

Comparison of Intraoperative Neural Response Telemetry Results and Postoperative Neural Response Telemetry Results in Case of Children with Congenital Bilateral Severe to Profound Sensorineural Hearing Loss Undergoing Single Sided Cochlear Implantation.

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. 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). 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. 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. The online version contains supplementary material available at 10.1007/s12070-022-03284-x.

Development of Custom Sound® Pro software utilising big data and its clinical evaluation

Objectives To inform and optimise a cochlear implant (CI) fitting software design through an analysis of big data to define array-specific comfort (C) level profiles, frequently-used MAP parameters, and the minimum number of Neural Response Telemetry thresholds (tNRT) needed to create an accurate profile. To evaluate the software’s ease of use and completion time for AutoNRT®s. Design MAPs analysis. Clinical study evaluating software use in creating MAPs, addressing sound-quality issues and setting patient goals. Study sample MAPs (N = 39,885); CI recipients (N = 47) and clinicians (N = 19). Results Distinct C-level profiles were observed for lateral-wall, contour, and slim-modiolar electrode arrays. Default settings were used for most MAP parameters (13/16) except for Pulse Width, Rate, and Maxima. Nine tNRT measurements were required for an accurate C-level profile. Measurement-time of nine tNRTs via the new algorithm was comparable to five tNRTs using the previous algorithm. Nearly all (99%) clinical tasks were completed by clinicians with the first use of the software. Most CI recipients (79.5%) rated goal-setting as valuable. Conclusion Custom Sound Pro fitting software developed based on big data analysis incorporates a guided fitting workflow and expected fitting ranges. It helps to improve clinical efficiency, is easy to use and supports patient-centred care.

The value of threshold of neural response telemetry on the prediction of behavioral audiometry threshold after cochlear implantation patients

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.

Effect of the vertical facial canal to round window distance concerning neural response telemetry during cochlear implantation in children.

To assess the correlation of the distance from the round window (RW) to the vertical facial canal (VFC) with neural response telemetry thresholds (T-NRT), which may have an influence on the insertion trajectory and aid in preoperative surgical planning and electrode selection. An observational study was conducted on 30 prelingually deaf children under five years diagnosed with bilateral severe to profound hearing loss and received a cochlear implant. The preoperative high resolution computed tomography (HRCT) images in the axial cut bone window setting at the round window level was used to calculate the distance from the RW to the VFC on the RadiAnt DICOM Viewer. The intraoperative distance was measured with ScopyDoc version 8.2.4 software. In Auto-NRT mode, software-based recordings (Cochlear's Custom Sound EP 6.0) were used to measure and evaluate the T-NRT current level. A statistically significant positive correlation of the RW to VFC distance with the average T-NRT p=0.02, r=-0.4 and with the mid-frequency, T-NRT p=0.003, r=-0.5 was found. The insertion trajectory can be ascertained by a statistically significant correlation between average T-NRT and mid-frequency T-NRT with RW and VFC distance, and this reliable factor can be taken into account in future surgical technique modulation, electrode selection, and electrode design.

Utility of intraoperative neural response telemetry in pediatric cochlear implants.

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). 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. 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 11/12at 3 months and electrodes 6/7at 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. 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.

Effect of inner ear malformations on intraoperative ECAP thresholds and postoperative auditory performance.

ObjectivesThis 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.MethodsThe 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.ResultsAbsent 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.ConclusionMeasurable 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 Evidence2b.

Is the spread of excitation width correlated to the speech recognition in cochlear implant users?

To assess whether there is an interference of the spread of excitation (SOE) on speech recognition. Retrospective cross-sectional study, approved by the institution's ethics committee (CAAE03409212.8.0000.0068). Adult patients with intraoperative neural response telemetry (NRT) performed on electrodes 6, 11 and 16 implanted with Cochlear Ltd (Sydney, Australia) devices were selected. Patients with partial array insertion, pre-lingual hearing loss, deafness etiology due to and CI experience less than 12months were excluded. SOE was recorded at 10 current units above the NRT threshold (tNRT) and its width in millimeters was collected at point 0.75 of the function. Speech recognition test was 25-recorded monosyllables list, presented at 65dBHL at 0° azimuth in a sound treated booth. The analysis was divided into groups by electrode array type, regarding the tNRT, SOE width, SOE's peak amplitude and electrode peak. A 126 SOE measurements of the 3 tested electrodes were obtained from 43 patients. Patients with straight array had significantly wider SOE, greater peak amplitude at electrode 6 and higher tNRTs. In the perimodiolar array, there was a negative correlation between SOE and monosyllables recognition at electrodes 6 and 11, and in the combined average of the three electrodes, with a significant difference in electrode 11. Sixty-six percent of the SOE measurements had their peak shifted to adjacent electrodes. It was observed, in perimodiolar array, the greater the dispersion of electrical current, the worse the speech recognition, especially in the medial electrode.

Efficacy of using NRT thresholds in cochlear implants fitting, in prelingual pediatric patients

ObjectiveTo evaluate the efficacy of using neural response telemetry (NRT) thresholds in predicting behavioural thresholds during programming of cochlear implant in prelingual children. MethodProspective study of 28 cochlear implants implanted with Nucleus 24 cochlear implant. We recorded NRT-thresholds on electrode numbers 1, 6, 11, 16 and 22 of the electrode array in each patient, the neural response thresholds were correlated with the behavioural map after six months of programming the device. ResultsThe mean neural response telemetry level was significantly higher than the mean threshold level (T-level) but lower than the comfortable level (C-level) in all the electrodes tested. NRT levels could statistically significantly predict T behavioural levels and comfortable behavioural levels, p < 0.01. There was a strong positive correlation between comfortable thresholds and neural response telemetry level measurements and behavioural threshold level and neural response telemetry threshold measurements. ConclusionThere is a useful role for neural response telemetry values in predicting the behavioural threshold and comfortable values in prelingual children. Combining the NRT values with behavioural observations can improve the programming of cochlear implants.

Evaluation of ECAP thresholds, T and C levels in children with sequential bilateral cochlear implants

Aim: The aim of the present study was to compare the values in threshold (T) and comfortable (C) stimulation levels as well as the neural response telemetry (NRT) measurements obtained on the first and the second cochlear implant in children with sequential bilateral cochlear implantation (CI). Material and Methods: Thirty children with sequential bilateral CI between February 2007 and July 2018 were randomly selected. The mean age of the subjects was 7.0 years (age range: 3.3–15.2 years). The NRT thresholds, T levels, and C levels in the electrode (E) 22, E16, E11, E6, and E1 were retrospectively compared for the latest program on the first CI (CI1), and the second CI (CI2) in the postoperative 1st, 3rd, and 6th-month follow-up visits. The duration of daily use of the speech processor on both side was also compared.Results: Twelve male and eightteen female subjects with sequential bilateral CI, were participated in the present study. The median age at CI1 was 15 months and 5 years 5 months for CI1 and CI2 respectively. There was no significant difference between the threshold NRT (tNRT) levels between two ears. The mean tNRT levels were obtained 166 CL and 179 CL in E22 and E1 respectively. The tNRT levels were found higher on the basal electrode rather than the apical electrode (p=0.02). The changes in the T and C levels were significant in 1st, 3rd, and 6th-month follow-up visits on the CI2 side (p=0.000). The mean daily usage time of the sound processor was found 12.05 and 9.62 hours on CI1 and CI2 respectively. Conclusion: In children with sequential CI, the electrical stimulation levels were similar between ears. The present study shows the programming outcomes during the follow-up in children with sequential bilateral CI. Keywords: Hearing loss; cochlear implant; sequential surgery; bilateral cochlear implantation; neural response telemetry.

Changes in Intraoperative and Postoperative Neural Response Telemetry in Cochlear Implant Users

Introduction: The cochlear implant directly stimulates the auditory nerve in deaf patients. Neural Response Telemetry (NRT) is used to record the response of the auditory nerve through thefeedback of the electrical signal. NRT does not need behavioral responses from very young children for thresholds and comfort levels. The status of the cochlear nerve activation with NRT was reviewed through intraoperative and postoperative neural responses. Aim of the work: To detect any changes in intraoperative and postoperative neural response telemetry in cochlear implant users. Patients and Methods:Thirty patients were implanted with a MED-EL device, Sonata II (Med-El, Innsbruck, Austria) at Sohag University hospital. Electrodes 2, 4, 6, 8, 9, 10, 11 and 12 were monitored intraoperatively. One month after surgery, the neural responses were investigated using the same electrodes as during the intraoperative procedures. The corresponding electrodes werethen checked again after another 3 months.Phase duration 30µs, begin by amplitude 200cu increasing in steps each 100cu till get response or reaching maximum level 1200cu (intraoperative) or reached the uncomfortable level of the child (postoperative). Threshold of the neuronal response is calculated using linear equation function. Results:There is significant improvement in thresholdsof NRTresponse postoperatively which was high intraoperatively. NRT threshold increase in postoperative follow up in comparison with first postoperative measurement but this increase is not statistically significant. Conclusion: Absence of NRT response in some electrodes intraoperative does not mean that electrode must be out of function or outside the cochlea.

Postoperative objective detecting techniques for cochlear implant children with inner ear malformation

ObjectivesThis study aims to investigate the changing characteristics and rules of electrically-evoked auditory brainstem response (EABR), electrically-evoked stapedius reflex threshold (ESRT) and neural response telemetry (NRT) after cochlear implant in children with inner ear malformation, and guide postoperative equipment debug. MethodsA total of 88 children with either normal cochlea (control group) or inner ear malformation (test group) received Australian 24 multi-channel cochlear implants. The EABR, ESRT and NRT thresholds at different time points within one year postoperatively and behavioral responses (T-level and C-level) after one year were detected. Furthermore, the changing characteristics and rules of these thresholds were analyzed. ResultsThe EABR, ESRT and NRT thresholds were all significantly higher at all time points in the test group than in the control group, but the general changing trends were similar. Particularly, these thresholds worsened at low frequencies and improved at high frequencies. Furthermore, EABR, ESRT and NRT thresholds gradually increased during the one year postoperative period. In addition, an extremely significant correlation was found between EABR and T-level and between ESRT and C-level, but a less significant correlation was found between NRT threshold and T-level in both groups. ConclusionsThe postoperative changes in characteristics and rules of EABR, ESRT and NRT thresholds among cochlear implant children with inner ear malformation were all the same as those with normal cochlea. Thus, these thresholds can be used to guide the postoperative equipment debug for cochlear implants into patients with inner ear malformation.

Auditory Performance and Electrical Stimulation Measures in Cochlear Implant Recipients With Auditory Neuropathy Compared With Severe to Profound Sensorineural Hearing Loss.

The aim of the study was to compare auditory and speech outcomes and electrical parameters on average 8 years after cochlear implantation between children with isolated auditory neuropathy (AN) and children with sensorineural hearing loss (SNHL). The study was conducted at a tertiary, university-affiliated pediatric medical center. The cohort included 16 patients with isolated AN with current age of 5 to 12.2 years who had been using a cochlear implant for at least 3.4 years and 16 control patients with SNHL matched for duration of deafness, age at implantation, type of implant, and unilateral/bilateral implant placement. All participants had had extensive auditory rehabilitation before and after implantation, including the use of conventional hearing aids. Most patients received Cochlear Nucleus devices, and the remainder either Med-El or Advanced Bionics devices. Unaided pure-tone audiograms were evaluated before and after implantation. Implantation outcomes were assessed by auditory and speech recognition tests in quiet and in noise. Data were also collected on the educational setting at 1 year after implantation and at school age. The electrical stimulation measures were evaluated only in the Cochlear Nucleus implant recipients in the two groups. Similar mapping and electrical measurement techniques were used in the two groups. Electrical thresholds, comfortable level, dynamic range, and objective neural response telemetry threshold were measured across the 22-electrode array in each patient. Main outcome measures were between-group differences in the following parameters: (1) Auditory and speech tests. (2) Residual hearing. (3) Electrical stimulation parameters. (4) Correlations of residual hearing at low frequencies with electrical thresholds at the basal, middle, and apical electrodes. The children with isolated AN performed equally well to the children with SNHL on auditory and speech recognition tests in both quiet and noise. More children in the AN group than the SNHL group were attending mainstream educational settings at school age, but the difference was not statistically significant. Significant between-group differences were noted in electrical measurements: the AN group was characterized by a lower current charge to reach subjective electrical thresholds, lower comfortable level and dynamic range, and lower telemetric neural response threshold. Based on pure-tone audiograms, the children with AN also had more residual hearing before and after implantation. Highly positive coefficients were found on correlation analysis between T levels across the basal and midcochlear electrodes and low-frequency acoustic thresholds. Prelingual children with isolated AN who fail to show expected oral and auditory progress after extensive rehabilitation with conventional hearing aids should be considered for cochlear implantation. Children with isolated AN had similar pattern as children with SNHL on auditory performance tests after cochlear implantation. The lower current charge required to evoke subjective and objective electrical thresholds in children with AN compared with children with SNHL may be attributed to the contribution to electrophonic hearing from the remaining neurons and hair cells. In addition, it is also possible that mechanical stimulation of the basilar membrane, as in acoustic stimulation, is added to the electrical stimulation of the cochlear implant.

Cone-beam computed tomography in children with cochlear implants: The effect of electrode array position on ECAP

ObjectivesTo assess the feasibility of using cone-beam computed tomography (CBCT) in young children with cochlear implants (CIs) and study the effect of intracochlear position on electrophysiological and behavioral measurements. MethodsA total of 40 children with either unilateral or bilateral cochlear implants were prospectively included in the study. Electrode placement and insertion angles were studied in 55 Cochlear® implants (16 straight arrays and 39 perimodiolar arrays), using either CBCT or X-ray imaging. CBCT or X-ray imaging were scheduled when the children were leaving the recovery room. We recorded intraoperative and postoperative neural response telemetry threshold (T-NRT) values, intraoperative and postoperative electrode impedance values, as well as behavioral T (threshold) and C (comfort) levels on electrodes 1, 5, 10, 15 and 20. ResultsCBCT imaging was feasible without any sedation in 24 children (60%). Accidental scala vestibuli insertion was observed in 3 out of 24 implants as assessed by CBCT. The mean insertion angle was 339.7°±35.8°. The use of a perimodiolar array led to higher angles of insertion, lower postoperative T-NRT, as well as decreased behavioral T and C levels. We found no significant effect of either electrode array position or angle of insertion on electrophysiological data. ConclusionCBCT appears to be a reliable tool for anatomical assessment of young children with CIs.Intracochlear position had no significant effect on the electrically evoked compound action potential (ECAP) threshold. Our CBCT protocol must be improved to increase the rate of successful investigations.

Role of dual energy CT with adjusted radiation dose in accurate assessment of electrode position in pediatric cochlear implant

Background and purposePostoperative imaging of cochlear implant needs to provide detailed information on the position of individual electrodes; the aim of this study was to evaluate visualization of individual electrodes and measurement of the electrode–modiolus distance (EMD) using dual energy CT (DECT) – with low radiation dose using virtual monochromatic spectral (VMS) imaging comparing the images quality and radiation dose with those by using multidetector CT (MDCT). Materials and methods25 pediatric patients who underwent cochlear implantation were imaged using DECT (15 patients) and MDCT (10 patients), and the image quality and radiation dose of DECT were compared to those of MDCT. Measurement of EMD was done for 5 electrodes and the results were correlated with neural response telemetry (NRT) and behavioural mapping levels. ResultsA statistically significant difference between the radiation dose of DECT and MDCT was confirmed (p=0.002) without a statistically significant difference in images quality (weighted K=−0.129 and PABAK=0.533).Statistically significant correlations were found between EMD and NRT threshold, T (threshold) and C (maximum comfortable) levels with p=<0.01. ConclusionDECT accurately detects the electrode position with low radiation dose which helps in CI fitting.

Neural Response Telemetry Thresholds in Patients with Cochlear Nerve Canal Stenosis.

To explore neural response telemetry (NRT) thresholds in patients with stenotic versus normal cochlear nerve canals. Case series with chart review. Tertiary referral center. Thirty pediatric patients with profound sensorineural hearing loss in at least 1 ear and no benefit from amplification underwent computed tomography imaging of the temporal bones. They were divided into 3 groups according to the diameter of the cochlear nerve canal: group A, <1.5 mm; group B, 1.5 to 1.7 mm; group C, 1.8 to 2.1 mm. All patients underwent cochlear implantation with full insertion of all electrodes. NRT was performed both intraoperatively and 6 months postoperatively in all patients; thresholds of electrodes 1, 11, and 22 were compared. Per analysis of variance, intraoperative and 6-month postoperative NRT thresholds were both significantly different among groups A, B, and C at electrodes 1 and 22 but not at electrode 11. On intergroup analysis, group A showed statistically higher thresholds than those of groups B and C; however, no difference was found between groups B and C. Cochlear nerve canal stenosis, defined as a canal diameter <1.5 mm, is associated with significantly increased NRT thresholds, which may play a role in postimplant performance.