The effect of cochlear implant age and duration of intervention on ESRT in children with cochlear implant.

OBJECTIVE: To study the effect of cochlear implant age and duration of the intervention (auditory rehabilitation post-cochlear implantation) on ESRT in children with cochlear implants. METHODS: A total of 90 pre-lingual cochlear implant users were included. For the measurement of ESRTs the recipient's processor was connected to the programming pod and electrode numbers 22, 11 and 3 (apical, middle and basal), respectively, were activated to give stimulation sequentially and elicit deflection as a response. RESULTS: There were significant differences in the measured T, C and ESRT levels with respect to the duration of the intervention (auditory rehabilitation post-cochlear implantation) and cochlear implant age obtained at p < 0.05*, 0.01**. DISCUSSION: The differences in the T, C and ESRT levels after continued device usage and after attending auditory rehabilitation sessions post-cochlear implantation are subjected to optimal benefit from implantation during the critical period. CONCLUSION: The differences in T, C and ESRT levels can be utilised clinically to study the importance of duration of cochlear implant device usage and the importance of auditory rehabilitation post-cochlear implantation in children with cochlear implantation.

Maximum acceptable level for the determination of ECAP and ESRT in a paediatric population.

OBJECTIVES: Two of the most used objective measures are electrically evoked action potentials (ECAPs) and electrically evoked stapedius reflex thresholds (ESRTs). Although stimuli used for these measures differ considerably, both measures are influenced by subjective loudness percept. We focus on the subjective maximum acceptable loudness (MAL) to investigate if loudness sensitivity varied along the electrode array during ECAP recordings. In addition, we explored how the MAL reached during an ECAP recording related to the postoperative ESRT. METHODS: Uni- and bilaterally implanted young CI users (n = 15, average age = 9 y, age range 3-18 y) underwent ECAP and ESR recordings using the clinical software MAESTRO (MED-EL, Innsbruck, Austria) and a commercially available immittance instrument (PATH MEDICAL GmbH, Germering, Germany). RESULTS: Loudness tolerance during ECAP recordings was lowest at the two apical-most electrode contacts (number 1 and 2). There was a moderate correlation between the MAL achieved during ECAP recordings and ESR maximum stimulation amplitudes. (r: 0.44344). CONCLUSIONS: ECAP recordings should commence at basal or medial contacts to increase the users' comfort and loudness tolerance, especially in young CI users. A higher maximum stimulation appears to increase the chance of the automatic determination of ECAP thresholds for all electrode contacts.

Stapedius reflex evoked in free sound field in cochlear implant users compared to normal-hearing listeners.

OBJECTIVE: To determine the relation between stapedius reflex thresholds in cochlear implant users evoked once through direct electric stimulation on single channels (ESRT) and once through acoustic stimulation in free sound field. For comparison, stapedius reflex thresholds were obtained in free sound field in a normal-hearing control group. DESIGN: For each participant a new ESRT-based fitting was created. Stapedius reflex thresholds were obtained for this new fitting in free sound field for different loudness adjustments. Acoustic stimuli for eliciting the stapedius reflex were narrow band noise signals covering the audiometric frequency range. STUDY SAMPLE: N = 29 experienced CI users (34 ears) and N = 10 normal hearing listeners. RESULTS: ESRT-based fitting resulted in different stapedius reflex behaviour compared to normal-hearing listeners. A frequency dependence was observed. Stapedius reflex thresholds decreased with increasing centre frequencies of acoustic narrow band noise stimuli. A linear relation between upper stimulation levels on the implant channels and corresponding stapedius reflex thresholds evoked in free sound field was found. CONCLUSION: The found correlation may be a guideline for adjusting the electrical dynamic range during cochlear implant fitting. This allows the implant system to mimic the natural reflex behaviour in the best possible way and potentially avoid overstimulation.

Automated detection of electrically evoked stapedius reflexes (eSR) during cochlear implantation.

INTRODUCTION: In cochlear implantation, objective fitting methods are needed to optimize audiological results in small children or patients with poor compliance. Intraoperatively measured electrically evoked stapedius reflexes (eSR) can be used as a marker for the patient's discomfort level. The aim of this study was to develop and evaluate an automated detection method for eSR and to compare it to the detection rate of the surgeon and independent observers. METHODS: Cochlear implantation using a fully digital surgical microscope was performed. Movements of the stapedius tendon were recorded and analyzed by means of computer vision technique. Differences in eSR elicited by stimulating electrodes at different cochlear locations (basal, middle and apical) were analyzed. The eSR detection rate of the image processing algorithm was compared to the surgeon's detection rate and to those of two less experienced observers. RESULTS: A total of 387 electrically impulses were applied. The stimulation of middle turn electrodes showed significantly higher detection rates (50.4%) compared to the basal (40.0%; p = 0.001) and apical (43.6%; p = 0.03) turn. The software identified significantly more of the applied stimuli (58.4%) compared to the surgeon (46.3%; p = 0.0007), the intermediate observer (37.7%; p < 0.0001) and the unexperienced observer (41.3%; p < 0.0001). CONCLUSION: The feasibility of an automated intraoperative software-based detection of eSR is demonstrated. By improving the eSR detection methods and their clinical applicability, their utility in objective cochlear implant fitting may be substantially increased.

Preemptive local anesthetic infiltration reduces opioid requirements without attenuation of the intraoperative electrical stapedial reflex threshold in pediatric cochlear implant surgery.

BACKGROUND AND AIMS: Total intravenous anesthesia using remifentanil provides good surgical condition without affecting the intraoperative electrical stapedial reflex threshold (ESRT). However, remifentanil results in hyperalgesia and increases postoperative opioid requirements. Local anesthetic infiltration is alternative methods to opioid for providing analgesia. However, otologists avoids its use as it can abolish the ESRT. We investigated the effect of the preemptive local anesthetic infiltration on intraoperative ESRT and opioid requirements in pediatric cochlear implant surgery performed under TIVA. MATERIAL AND METHODS: Prospective, randomized, double-blinded, controlled study including 70 child undergoing cochlear implant under TIVA were randomly assigned to a local anesthesia (LA group, n = 35) or control (CT group, N = 35). The primary outcome was the total tramadol consumption during the first 24 h postoperative, and the secondary outcomes were time to first analgesia request, postoperative pain scores, the ESRT and, propofol and remifentanil requirements. The incidence of postoperative vomiting was recorder as well. RESULTS: The total tramadol consumption during the first 24 h after surgery was significantly less in the LA group than in CT group (8.25 [4.3] vs. 16.5 [6.57] mg, P < 0.01). The time to first analgesic request was significantly prolonged in the LA group as compared with the CT group [8 [2-12] vs. 3 [0-8] h, P < 0.01). The postoperative Faces, Legs, Activity, Cry Consolability pain scores were significantly lower in the LA group at 15 min, 30 min, 2, 4 and 6 h postoperative. Mean remifentanil infusion rate [mean (standard deviation)] was significantly higher in in the CT group than in the LA group [0.7 (0.3) vs. 0.5 (0.2) µg/kg/min; P = 0.001).The ESRT response, propofol requirements, and the incidence of postoperative vomiting had no significant differences between both groups. CONCLUSION: Preemptive local anesthetic infiltration reduced opioid requirements without attenuation of the ESRT in pediatric cochlear implant surgery performed under TIVA.

Magnesium sulphate optimises surgical field without attenuation of the stapaedius reflex in paediatric cochlear implant surgery.

BACKGROUND AND AIMS: The anaesthesia technique for paediatric cochlear implantation should be modified to achieve an optimised surgical field and allow neuromonitoring. Total intravenous anaesthesia (TIVA) provides good surgical condition without affecting intraoperative electrical stapaedial reflex threshold (ESRT). Though magnesium sulphate (MgSO4) is a cheap, readily available drug for controlled hypotension, it can decrease the amplitude of motor-evoked potentials. This study aimed to evaluate the effect of MgSO4 infusion on quality of surgical field, intraoperative ESRT, and anaesthetic requirements in paediatric cochlear implant surgery performed under TIVA. METHODS: In this randomised controlled trial, 66 children (1-6 years) undergoing cochlear implant under TIVA were randomly assigned to control group or MgSO4 group. The primary outcome was quality of surgical field, and the secondary outcomes were mean arterial blood pressure (MAP), heart rate (HR), ESRT, and the intraoperative anaesthetic requirements. The incidence of adverse events was recorded as well. RESULTS: The quality of surgical field was better in group M than group C, P < 0.02. The number of children who achieved optimum surgical conditions (scores ≤2) was significantly better in the group M (n = 23/33, 70%) compared with group C (n = 13/33, 39%), P < 0.001. MAP, HR, and anaesthetic requirements were significantly lower in group M, P < 0.05. There were no differences between both groups regarding ESRT response. CONCLUSION: Magnesium sulphate IV infusion optimised surgical field and decreased anaesthetic requirements without attenuating the ESRT in paediatric cochlear implant surgery performed under TIVA.

Novel method of fitting of children with auditory brainstem implants.

OBJECTIVES: To develop a reliable and objective fitting method for use with young children with an auditory brainstem implant (ABI). MATERIALS AND METHODS: Subjects were 17 young children implanted with an ABI with the mean age 2 years and 4 months (8-64 months). Evoked auditory brainstem response (eABR) measurements were performed intraoperatively and at activation in order to record the auditory response and non-auditory side effects. Each child was tested to observe any subjective responses to the electric stimuli and non-auditory side effects. All children were fitted based on the postoperative eABR. The minimum follow up time was 12 months. RESULTS: Intraoperatively an eABR could be obtained in all children. The responses were recordable from 75-100% of all electrodes. At initial stimulation eABR were recordable in all children. The eABR was obtained in 79.7% of all electrodes (25-100%) with a mean eABR threshold of 22.3 nC. eABR without any non-auditory stimulation was recorded on all electrodes in 11 children. Mixed eABR and non-auditory responses were recorded on 2-6 electrodes in 6 children. The subjective auditory responses for at least 1 electrode were noted in 15 children. In the 2 remaining cases the auditory response was obtained only when the device was activated. In all children the subjective responses were within the estimated dynamic range for each electrode. Each child was able to accept up to 100% of volume of the created map. The non-auditory response was observed only on children and electrodes with mixed eABR and non-auditory responses. The mean CAP score at 6 months after the activation was 2.4 (1-4). CONCLUSIONS: eABR seems to be a reliable tool to judge ABI electrode placement and a reliable method for fitting of young children with an ABI. The data suggest that eABR-based fitting helps children to more quickly achieve auditory perception and development.

Comparing eSRT and eCAP measurements in pediatric MED-EL cochlear implant users.

INTRODUCTION: Electrically evoked compound action potentials (eCAP) and electrically evoked stapedius reflexes are the most frequently used objective measurements for programming a cochlear implant (CI) audio processor. Objective methods are particularly beneficial for children and CI users that encounter difficulties in providing feedback. In this study, we compared the threshold and the slope of the eCAP amplitude growth function with the electrically evoked stapedius reflex threshold (eSRT) in pediatric CI users. Furthermore, the duration times required to perform eCAP and eSRT recordings were compared. METHODS: During a regular fitting session, 52 pediatric CI users with recordable eSRTs having MED-EL devices (MED-EL GmbH, Innsbruck, Austria) were programmed using the eSRT fitting method. The eCAP thresholds and the slopes of the amplitude growth function were measured across one apical, one medial, and one basal electrode contact. RESULTS: There was a weak to medium correlation between eCAP thresholds and eSRTs. The eCAP threshold profile did not correlate with the eSRT profile. Typically ECAP thresholds were at a lower stimulation charge than eSRTs with only 4/152 being higher. An eCAP threshold was found on 152/156 electrode contacts with eSRTs. On average, the eCAP measurements took 4.2 times longer to record per electrode than eSRT measurements (median durations 35 s vs. 120 s). CONCLUSION: eSRTs were significantly higher than eCAP thresholds and eSRT and eCAP profiles were generally different from each other reducing the clinical relevance of eCAP testing for setting MCLs across the array. Additionally, the eSRT measurements were faster to record than the eCAP threshold and slope determination measurements.

Objective and subjective evaluations of the Nurotron Venus cochlear implant system via animal experiments and clinical trials.

CONCLUSION: This study described objective and subjective evaluations of the Nurotron® Venus™ Cochlear Implant System and indicated that this system produced a satisfactory performance. OBJECTIVE: To observe the performance of the Nurotron® Venus™ cochlear implant (CI) system via electrophysiological and psychophysical evaluations. METHODS: A 26-electrode CI system was specially designed. The performance of MRI in animal and cadaveric head experiments, EABR in cats experiment, the correlation between ESRT and C level, and psychophysics evaluations in clinical trials were observed. RESULTS: In the animal and cadaveric head experiments, magnet dislocation could not be prevented in the 1.5 T MRI without removal of the internal magnet. The EABR was clearly elicited in cat experiment. In the clinical trial, the ESRT was strongly correlated with C level (p < 0.001). The human clinical trial involving 57 post-lingually deafened native Mandarin-speaking patients was performed. Residual hearing protection in the implanted ear at each audiometric frequency was observed in 27.5-46.3% patients post-operatively. A pitch ranking test revealed that place pitches were generally ordered from apical to basal electrodes. The recognitions of the perceptions of 301 disyllabic words, environment sounds, disyllabic words, and numerals were significantly better than the pre-operative performance and reached plateaus.

Electrophysiological Correlates of Behavioral Comfort Levels in Cochlear Implantees: A Prospective Study.

Indications for cochlear implantation have expanded today to include very young children and those with syndromes/multiple handicaps. Programming the implant based on behavioral responses may be tedious for audiologists in such cases, wherein matching an effective MAP and appropriate MAP becomes the key issue in the habilitation program. In 'Difficult to MAP' scenarios, objective measures become paramount to predict optimal current levels to be set in the MAP. We aimed, (a) to study the trends in multi-modal electrophysiological tests and behavioral responses sequentially over the first year of implant use, (b) to generate normative data from the above, (c) to correlate the multi-modal electrophysiological thresholds levels with behavioral comfort levels, and (d) to create predictive formulae for deriving optimal comfort levels (if unknown), using linear and multiple regression analysis. This prospective study included ten profoundly hearing impaired children aged between 2 and 7 years with normal inner ear anatomy and no additional handicaps. They received the Advanced Bionics HiRes 90K Implant with Harmony Speech processor and used HiRes-P with Fidelity 120 strategy. They underwent, Impedance Telemetry, Neural Response Imaging, Electrically Evoked Stapedial Response Telemetry and Electrically Evoked Auditory Brainstem Response tests at 1, 4, 8 and 12 months of implant use, in conjunction with behavioral Mapping. Trends in electrophysiological and behavioral responses were analyzed using paired t test. By Karl Pearson's correlation method, electrode-wise correlations were derived for NRI thresholds versus Most Comfortable Levels (M-Levels) and offset based (apical, mid-array and basal array) correlations for EABR and ESRT thresholds versus M-Levels were calculated over time. These were used to derive predictive formulae by linear and multiple regression analysis. Such statistically predicted M-Levels were compared with the behaviorally recorded M-Levels among the cohort, using Cronbach's Alpha Reliability test method for confirming the efficacy of this method. NRI, ESRT and EABR thresholds showed statistically significant positive correlations with behavioral M-Levels, which improved with implant use over time. These correlations were used to derive predicted M-Levels using regression analysis. Such predicted M-Levels were found to be in proximity to the actual behavioral M-Levels recorded among this cohort and proved to be statistically reliable. When clinically applied, this method was found to be successful among subjects of our study group. Although there existed disparities of a few clinical units, between the actual and predicted comfort levels among the subjects, this statistical method was able to provide a working MAP, close to the behavioral MAP used by these children. The results help to infer that behavioral measurements are mandatory to program cochlear implantees, but in cases where they are difficult to obtain, this study method may be used as reference for obtaining additional inputs, in order to set an optimal MAP. The study explores the trends and correlations between electrophysiological tests and behavioral responses, recorded over time among a cohort of cochlear implantees and provides a statistical method which may be used as a guideline to predict optimal behavioral levels in difficult situations among future implantees. In 'Difficult to MAP' scenarios, following a protocol of sequential behavioral programming, in conjunction with electrophysiological correlates will provide the best outcomes.