Contour Electrode Research Articles

Intraoperative Handheld Digital X-ray for Assessment of Intracochlear Positioning of Electrode Arrays in Recipients of Cochlear Implants.

Objectives: This study aims to evaluate the practicality of handheld digital X-ray in determining the position of the electrode array following Cochlear implantation (CI). Methods: A retrospective study was conducted involving 11 patients (12 ears) who underwent intraoperative imaging via handheld X-ray (MINE ALNU®, OTOM, Gwangju, South Korea) post-CI between December 2021 and January 2023. Immediate confirmation of the correct electrode array placement in the cochlea was achieved, with subsequent comparisons made to C-arm image and postoperative transorbital view X-ray. Results: Rapid intraoperative imaging was achieved in all instances. The electrode types used included 9 Nucleus slim modiolar electrodes, 1 Nucleus contour electrode, and 2 Medel flex26 electrodes. A malpositioned electrode array was detected in one patient. The handheld digital X-ray also adeptly visualized the electrodes implanted in pediatric patients. Conclusions: The use of intraoperative handheld digital X-ray using MINE ALNU® proves to be a safe, efficient, straightforward, and reliable method for immediate identification of an inserted electrode array. It has potential to replace the traditional C-arm X-ray for verifying electrode positioning in the operating room.

Impedance development after implantation of hybrid-L24 cochlear implant electrodes

Objective Shorter and thinner electrodes were developed for preserving residual hearing after cochlear implantation by minimising trauma. As trauma is regarded as one of the causes of fibrous tissue formation after implantation, and increase in impedance is considered to be connected to fibrous tissue formation, the aim of the current study was to evaluate impedance development after implantation of Hybrid-L electrodes. Design Impedance values were retrospectively collected from our clinical database and evaluated for all active contacts and basal, middle and apical contacts separately for up to 10 years. Study samples All 137 adult patients received a Hybrid-L electrode and had to be implanted for at least 1 year. Results On average impedances increased to 13 kOhm before first fitting and dropped to 5–7 kOhm under electrical stimulation with lower values measured on apical contacts. Mean values remained stable over years, but variability increased. Values before first fitting were independent of age at implantation whereas lower values were found later in patients of higher age at implantation. Conclusion Despite smaller contacts, impedance values after start of electrical stimulation were comparable to published values of Contour electrodes. This might suggest less tissue growth with the Hybrid-L electrode array.

Responsiveness of the Electrically Stimulated Cochlear Nerve in Children With Cochlear Nerve Deficiency.

This study aimed to (1) investigate the responsiveness of the cochlear nerve (CN) to a single biphasic-electrical pulse in implanted children with cochlear nerve deficiency (CND) and (2) compare their results with those measured in implanted children with normal-size CNs. Participants included 23 children with CND (CND1 to CND23) and 18 children with normal-size CNs (S1 to S18). All subjects except for CND1 used Cochlear Nucleus cochlear implants with contour electrode arrays in their test ears. CND1 was implanted with a Cochlear Nucleus Freedom cochlear implant with a straight electrode array in the test ear. For each subject, the CN input/output (I/O) function and the refractory recovery function were measured using electrophysiological measures of the electrically evoked compound action potential (eCAP) at multiple electrode sites across the electrode array. Dependent variables included eCAP threshold, the maximum eCAP amplitude, slope of the I/O function, and time-constants of the refractory recovery function. Slopes of I/O functions were estimated using statistical modeling with a sigmoidal function. Recovery time-constants, including measures of the absolute refractory period and the relative refractory period, were estimated using statistical modeling with an exponential decay function. Generalized linear mixed-effect models were used to evaluate the effects of electrode site on the dependent variables measured in children with CND and to compare results of these dependent variables between subject groups. The eCAP was recorded at all test electrodes in children with normal-size CNs. In contrast, the eCAP could not be recorded at any electrode site in 4 children with CND. For all other children with CND, the percentage of electrodes with measurable eCAPs decreased as the stimulating site moved in a basal-to-apical direction. For children with CND, the stimulating site had a significant effect on the slope of the I/O functions and the relative refractory period but showed no significant effect on eCAP threshold and the maximum eCAP amplitude. Children with CND had significantly higher eCAP thresholds, smaller maximum eCAP amplitudes, flatter slopes of I/O functions, and longer absolute refractory periods than children with normal-size CNs. There was no significant difference in the relative refractory period measured in these two subject groups. In children with CND, the functional status of the CN varied along the length of the cochlea. Compared with children with normal-size CNs, children with CND showed reduced CN responsiveness to electrical stimuli. The prolonged CN absolute refractory period in children with CND might account for, at least partially, the observed benefit of using relatively slow pulse rate in these patients.

Comparison of hearing rehabilitation for patients with Mondini malformation after cochlear implantation with different electrodes

Objective:To investigate the feasibility of cochlear implantation with contour electrode in patients with Mondini malformation and analysis of hearing rehabilitation after operation.Method:Collection of 9 cases of straight electrode cochlear implantation patients with Mondini malformation, according to the age of deafness and the condition of rehabilitation, 9 patients with curved electrode implanted were matched and grouped.Retrospectively analysis of audiology characteristics, surgical technique, postoperative NRT results and map results, and evaluating the hearing and speech rehabilitation ability by CAP and SIR scores. The test parameters and rehabilitation effect of two groups' patients were compared according to different implant electrode.Result:Eighteen cases of patients with Mondini malformation are severe sensory neural hearing loss according to preoperative hearing test, 6 cases without residual hearing. By preoperative EABR test, all patients were implanted with different types of electrode. There were 4 cases of gush in operation, 2 cases of facial spasm in straight electrode group, no complications postoperative cerebrospinal fluid leakage, no facial paralysis, no meningitis and other surgical complication after operation. Detecting NRT, the inducing rate of NRT was 77.78% in contour electrode group and 55.56% in straight electrode group; 6 month after operation, the average T value was (145.11±10.88)CL in contour electrode group and (168.44±22.45)CL in straight electrode group (P< 0.05); the average C value was (182.67±14.65)CL in contour electrode group and (213.00±19.27)CL in straight electrode group (P< 0.05). Dynamic range:(37.56±6.75)CL in contour electrode group and (44.56±18.06)CL in straight electrode group (P> 0.05). Postoperative follow-ups were performed from 6 months to 4 years, the average score of CAP was 7.28±0.62 in contour electrode group and 7.22±0.79 in straight electrode group (P> 0.05); the average score of SIR was 4.17±0.56 in contour electrode group and 4.00±0.71 in straight electrode group (P> 0.05).Conclusion:Contour electrode can be chosen for bilateral serious hearing loss patients with Mondini malformation assisted by EABR, there is no significant difference compared with straight electrode in postoperative hearing and speech rehabilitation ability. The advantages are that the stimulation quantity is small, the NRT extraction rate is high, and the complication rate is low.

Intraoperative Electrophysiologic Variations Caused by the Scalar Position of Cochlear Implant Electrodes.

The position of cochlear implant (CI) electrodes in the cochlea is fundamental for the interaction between the implant and the neurons of the spiral ganglion. The scalar position of the electrode in the cochlea is assumed to be an important parameter for the clinical outcome. In our study, the intraoperative electrophysiologic characteristics in dependence of the position of CI electrodes in the scala tympani or in the scala vestibuli after scalar change should be determined. The intraoperative impedances and neural response telemetry (NRT) data of 23 patients implanted with a Nucleus Advance Contour (Cochlear Pty, Sydney, Australia) electrode were recorded. One CI surgeon and two radiologists evaluated the electrode array's position independently radiologically by flat-panel tomography. Results from 17 patients with the electrode positioned in the scala tympani and six patients with the electrode changing intraoperatively from the tympanic into the vestibular scala were retrospectively analyzed. We found a statistically significant difference with an NRT threshold-based ratio for the groups. An estimation of the (radiologically confirmed) scalar position based on the NRT ratio was possible retrospectively. The evaluation of specific intraoperative electrophysiologic data allowed separating between a regular and an irregular (i.e., scalar changing) position of CI electrodes. This noninvasive methodology can support the postoperative radiologic evaluation of the CI electrode array position.

Compare NRT value of straight electrode and contour electrode in Nucleus 24 cochlear implant system

To learn the neural response of spiral ganglion cell to electrical stimulus by comparing the neural response telemetry(NRT) value between straight electrode and contour electrode in Nucleus 24 cochlear implant system. Fourty-six patients with Nucleus 24 cochlear implants were paired into two groups: 23 with contour electrode and 23 with straight electrode respectively. NRT value of each group were tested and compared. The NRT value of straight electrode fell in the range of 160 microV to 170 microV and contour electrode 150 microV to 160 microV. The NRT were going up higher a little bit from electrode twenty to electrode one. The contour electrode requires less power consumption than straight electrode in Nucleus 24 cochlear implant system.

Finite element modelling of the insertion of an electrode array into the cochlear scala tympani with lubricant

Cochlear implants, consisting of electrode arrays for electrically stimulating the auditory nerve fibres, have been developed to restore hearing for profoundly deaf people. The insertion of a straight electrode array into the spiral cochlear scala tympani has unfortunately been found to damage delicate structures within the inner ear, such as the spiral ligament and the basilar membrane. Although a number of studies suggested the use of lubricant for smooth insertion, little attempt has been made to quantify the effect of lubricant on the damage by the electrode array to the cochlear structures. We develop a mathematical model, using the finite element method, to predict the trajectories of the Nucleus standard straight electrode array during insertion into the scala tympani, and associated contact stresses exerted by the array on the cochlear structures. Results from the model show that the use of a lubricant, such as glycerine, reduces the contact stresses exerted by the tip of the array on the spiral ligament from 0.31 to 0.2MPa, whereas the contact stresses on the basilar membrane reduce from 0.075MPa (without lubricant) to 0.025MPa (with lubricant). These results suggest that the use of a lubricant is clinically important for minimising the likelihood of damage by the electrode array to the cochlear structures. References B. K. Chen, G. M. Clark, and R. Jones. Evaluation of trajectories and contact pressures for the straight nucleus cochlear implant electrode array --- a two-dimensional application of finite element analysis. Medical Engineering and Physics, 25:141--147, 2003. doi:10.1016/S1350-4533(02)00150-9. G. M. Clark. Cochlear implants --- Fundamentals and Applications. Springer-Verlag, New York, 2003. L. T. Cohen, J. Xu, S. A. Xu, and G. M. Clark. Improved and simplified methods for specifying positions of the electrode bands of a cochlear implant array. American Journal of Otology, 17:859--865, 1996. H. N. Kha and B. K. Chen. Determination of frictional conditions between electrode array and endosteum lining for use in cochlear implant models. Journal of Biomechanics, 39(9):1752--1756, 2006. doi:10.1016/j.jbiomech.2005.04.031. H. N. Kha, B. K. Chen, G. M. Clark, and R. Jones. Stiffness properties for {N}ucleus standard straight and {C}ontour electrode arrays. Medical Engineering and Physics, 26:677--685, 2004. doi:10.1016/j.medengphy.2004.05.001. R. Laszig, G. J. Ridder, and M. Fradis. Intracochlear insertion of electrodes using hyaluronic acid in cochlear implants. Journal of Laryngology Otology, 116:371--372, 2002. doi:10.1258/0022215021910816. E. Lehnhardt. In B. Fraysse and O. Deguine, editors, Cochlear implants: new perspectives, volume 48 of Advances in Otorhinolaryngology, pages 62--64. Karger, Basel, 1993. Noran Engineering Inc. NE/Nastran Version 8.2 User's Manual, 2002. J. J. T. Roland, T. M. Magardino, J. T. Go et al. Effects of glycerine, hyaluronic acid, and hydroxypropyl methylcellulose on the spiral ganglion of the guinea pig cochlea. Annals of Otology, Rhinology and Laryngology Supplement, 166:64--68, 1995. R. K. Shepherd, G. M. Clark, B. C. Pyman, and R. L. Webb. Banded intracochlear electrode array: Evaluation of insertion trauma in human temporal bones. Annals of Otology, Rhinology and Laryngology, 94:55--59, 1985. C. Todd, F. Naghdy, and M. Svehla. Force application during cochlear implant insertion: An analysis for improvement of surgeon technique. IEEE Transactions on Biomedical Engineering, 54(7):1247--1255, 2007. doi:10.1109/TBME.2007.891937. M. Tykocinski, E. Saunders, L. T. Cohen, C. Treaba, R. J. Briggs, P. Gibson, G. M. Clark, and R. S. Cowan. The Contour electrode array: safety study and initial patient trials of a new perimodiolar design. Otology Neurotology, 22:33--41, 2001. P. Wardrop, D. Whinney, S. J. Rebscher, J. T. J. Roland, W. Luxford, and P. A. Leake. A temporal bone study of insertion trauma and intracochlear position of cochlear implant electrodes. {I}: comparison of {N}ucleus banded and {N}ucleus {C}ontour electrodes. Hearing Research, 203:54--67, 2005. doi:10.1016/j.heares.2004.11.006.

Preliminary results and technique for electrophysiological intra-operative monitoring of residual hearing during cochlear implantation

AimsTo assess the feasibility of intra-operative monitoring of residual hearing using electrocochleography (ECOG) during cochlear implantation. We present our methods and preliminary results.MethodsWe attempted to monitor 21 consecutive paediatric and adult subjects during cochlear implantation. All subjects were implanted via a promontory cochleostomy with full electrode insertions of CochlearTM Nucleus® (Cochlear Nucleus, Cochlear Ltd, Australia) devices: 8 with straight electrodes and 13 with contoured electrodes. Baseline recordings were made after the completion of the posterior tympanotomy, and subsequently at stages of the cochleostomy and electrode insertion.ResultsWe were unable to obtain recordings on five patients because the ear-insert tubing kinked, which disrupted transmission of the stimulus. Five had insufficient cochlear function to be able to record a baseline ECOG. No subjects in whom we were able to obtain a satisfactory baseline ECOG (n = 11) had a reduction in ECOG action potential (AP) amplitude, morphology or threshold up to completion of the cochleostomy. Seven maintained an unchanged ECOG throughout the procedure to full insertion. An implant had to be replaced because of a faulty straight electrode in one patient. The amplitude significantly reduced during insertion of the replacement array. Two had a reduction in amplitude, threshold, and shape of the wave related to inadvertent suction of the perilymph. Subsequently, one maintained this changed ECOG to the end of the procedure, but the other progressed to complete loss of the ECOG during insertion of the array. One other subject had a significant reduction in the amplitude during insertion of the electrode from a depth of approximately 18 mm to full insertion.ConclusionsIntra-operative monitoring of residual hearing may be possible in most patients undergoing cochlear implantation. This pilot study suggests that cochleostomy is not associated with intra-operative loss of residual hearing; ECOG can be preserved during the procedure in most patients; intra-operative loss of hearing is most likely to occur when the tip of the array reaches the basal turn of the cochlea. This risk may increase if the array has to be removed and re-inserted. Suction of perilymph causes immediate changes, which may not recover.

Electrode Interaction in Cochlear Implant Recipients: Comparison of Straight and Contour Electrode Arrays

The degree of overlap among cochlear nerve fibers stimulated by different electrodes results in electrode interaction, which has been shown to have a significantly deleterious effect on speech recognition performance in multi-electrode cochlear implant users. The Nucleus CI24R(CS) Contour array, which lies substantially closer to the modiolus than the CI24M straight array, is expected to exhibit narrower excitation patterns. The neural response telemetry (NRT) 3.0 software provides a method of measuring the spread of neural excitation by presenting the masker and probe pulses on different intra-cochlear electrode bands. Nine pairs of children, using Nucleus CI24M/CI24R(CS) cochlear implants with a similar etiology and duration of deafness, insertion depth, age of implantation and loudest acceptable presentation level (LAPL) in NRT sessions, participated in the study. Profiles of the spread of neural excitation stimulated at the LAPL at 3 probe locations were examined for each pair of the 2 types of electrode array. The spread of neural excitation with respect to array type and location revealed significant effects (p < 0.001; p = 0.002) and no interaction between array type and probe location (p = 0.559). The results demonstrated that the Contour array improved electrode discrimination, especially for the electrodes at the basal end of the cochlea. The findings have implications for future electrode array design and current implant mapping strategies.

Electrically Evoked Auditory Brainstem Responses in Adults and Children

Previous electrophysiologic studies of electrode placement within the scala tympani in both animals and humans have shown effects on neural responses to electrical stimulation. The specific effects, however, may be dependent on electrode design, the location of an electrode along the array, and the method of perimodiolar positioning. The present study compares the effects of lateral and medial positioning of the Nucleus Contour electrode array on electrophysiologic responses in adult and pediatric subjects. Prospective clinical study. Comprehensive Cochlear Implant Program/Tertiary Referral Center. Subjects were adults (n = 15) and children (n = 20) who were consecutively implanted at our center with the Nucleus 24 Contour device. Rehabilitative. Intraoperative electrically evoked auditory brainstem responses (EABRs) were recorded within subjects for lateral and medial placement of the electrode array. Effects of electrode placement on EABR Wave V threshold and suprathreshold amplitude were measured. Group analyses showed significant decreases in EABR threshold and significant increases in EABR amplitude across all electrodes with medial electrode placement. The effects differed across electrode locations for the adult and pediatric subjects. No significant changes in Wave V input/output function slope were found. Medial electrode placement from stylet removal with the Nucleus 24 Contour array results in an increased neural response compared with the lateral condition as demonstrated by lower threshold and larger suprathreshold amplitude of the EABR. Possible clinical implications of these findings are lower psychophysical threshold and comfortable levels with medial cochlear electrode position.

Automated insertion of preformed cochlear implant electrodes: evaluation of curling behaviour and insertion forces on an artificial cochlear model

As a substantial part of our concept of a minimally invasive cochlear implant (CI) surgery, we developed an automated insertion tool. Studies on an artificial scala tympani model were performed in order to evaluate force application when using the insertion tool. Contour electrodes were automatically inserted into a transparent cochlea model in Advance Off-Stylet technique. Occurring forces were measured by the use of a load cell and correlated with observed intracochlear movement of the electrode carriers. Mean insertion forces were measured up to 20 mN comparable to previous studies on temporal bones. The most influencing factor is the implant's 2D curling behaviour in comparison to the 3D helical shape of the cochlea. The study confirms the functionality and reliability of the automated insertion tool for insertion of preformed CI. Improved insertion strategies considering patient-specific anatomy become possible.

Electrical stimulation rate effects on speech perception in cochlear implants

The objective of this study was to explore cochlear implant users’ speech perception performance in quiet and in noise for low to moderate stimulation rates. Eight postlingually deaf adult users of the Nucleus CI24 cochlear implant (contour electrode array) using the ESPrit 3G speech processor participated in this study. Monosyllabic word recognition in quiet and sentence perception in noise was evaluated for low to moderate stimulation rates of 275, 350, 500, and 900 pulses-per-second/channel (pps/ch). All four stimulation rate programs were balanced for loudness. A repeated ABCD experimental design was employed. Take home practice was provided with each stimulation rate. Subjects also responded to a comparative questionnaire to examine their rate preference for a variety of listening situations. Results for six of the eight subjects showed no significant effect of rate for monosyllables in quiet. However, results for the sentence test in noise demonstrated improvements with 500 or 900 pps/ch stimulation rates in seven out of the eight subjects. Although there was not a close relationship between each subject's subjective preference and the rate program that provided best speech perception, most subjects indicated a preference for 500 pps/ch rate in noise.

Otosclerosis

1. To examine whether speech perception after implantation is correlated with the total duration of deafness, the duration of deafness in the implanted ear, or age at implantation. 2. To examine whether the rate of facial nerve stimulation postoperatively is correlated with the type of electrode used. Retrospective case note review. Tertiary referral center. Fifty-nine adults with profound postlingual sensorineural hearing loss due to otosclerosis. Cochlear implantation with the Nucleus device using either a straight (n = 35) or Contour (n = 29) electrode array. Speech perception scores for patients at 3, 6 and 12 months postimplantation were correlated against duration of deafness in the implanted ear, duration of total deafness, and age at implantation. Data on facial nerve stimulation rates postoperatively were collected. Implantation in the shortest deafened ear conferred an initial advantage for speech perception 3 months after surgery; however, this effect was lost by 6 months. There were no significant correlations between the duration of bilateral deafness and hearing outcomes. Age at implantation was negatively correlated with outcome at 3 months, but not at 6 and 12 months. Fourteen of 35 patients with straight electrodes and 0 of 24 patients with Contour electrodes experienced facial nerve stimulation during mapping sessions (p < 0.005, chi). Patients with otosclerosis are not disadvantaged in the long term by implantation in the longest deafened ear. Increasing age at implantation did not predict poorer outcomes. A perimodiolar design of electrode should be used in otosclerotic patients when possible to reduce the risk of facial nerve stimulation.

Clinical Evaluation of Higher Stimulation Rates in the Nucleus Research Platform 8 System

The effect on speech perception of using higher stimulation rates than the 14.4 kHz available in the Nucleus 24 cochlear implant system was investigated. The study used the Nucleus Research Platform 8 (RP8) system, comprising the CI24RE receiver-stimulator with the Contour electrode array, the L34SP body-worn research speech processor, and the Nucleus Programming Environment (NPE) fitting and Neural Response Telemetry (NRT) software. This system enabled clinical investigation of higher stimulation rates before an implementation in the Freedom cochlear implant system commercially released by Cochlear Limited. Use of higher stimulation rates in the ACE coding strategy was assessed in 15 adult subjects. An ABAB experimental design was used to control for order effects. Program A used a total stimulation rate of between 12 kHz and 14.4 kHz. This program was used for at least the first 3 mo after initial device activation. After evaluation with this program, each subject was provided with two different higher stimulation rate programs: one with a total stimulation rate of 24 kHz and the other with a total stimulation rate of 32 kHz. After a 6-week period of familiarization, each subject identified his/her preferred higher rate program (program B), and this was used for the evaluation. Subjects then repeated their use of program A for 3 wk, then program B for 3 wk, before the second evaluation with each. Speech perception was evaluated by using CNC open-set monosyllabic words presented in quiet and CUNY open-set sentences presented in noise. Preference for stimulation rate program was assessed via a subjective questionnaire. Threshold (T)- and Comfortable (C)-levels, as well as subjective reports of tinnitus, were monitored for each subject throughout the study to determine whether there were any changes that might be associated with the use of higher stimulation rates. No significant mean differences in speech perception results were found for the group between the two programs for tests in either quiet or noise. Analysis of individual subject data showed that five subjects had significant benefit from use of program B for tests administered in quiet and for tests administered in noise. However, only two of these subjects showed benefit in both test conditions. One subject showed significant benefit from use of program A when tested in quiet, whereas another showed benefit with this program in noise. Each subject's preferred program varied. Five subjects reported a preference for program A, eight subjects reported a preference for program B and two reported no overall preference. Preference between the different stimulation rates provided within program B also varied, with 10 subjects preferring 24 kHz and five preferring 32 kHz total stimulation rates. A significant increase in T-levels from baseline measures was observed after three weeks of initial experience with program B, however there was no difference between the baseline levels and those obtained after five weeks of use. No significant change in C-levels was found over the monitoring period. No long-term changes in tinnitus that could be associated with the use of the higher stimulation rates were reported by any of the subjects. The use of higher stimulation rates may provide benefit to some but not all cochlear implant recipients. It is important to optimize the stimulation rate for an individual to ensure maximal benefit. The absence of any changes in T- and C-levels or in tinnitus suggests that higher stimulation rates are safe for clinical use.

Quality Control After Insertion of the Nucleus Contour and Contour Advance Electrode in Adults

To evaluate the quality of insertion of the Nucleus Contour and the newly developed Contour Advance electrode in adult cochlear implant recipients and to compare results of speech performance tests with regard to electrode position. A total of 43 adult patients with a history of progressive hearing loss having received a Nucleus cochlear implant, 21 of which had received a Contour electrode and 22 a Contour Advance electrode, were evaluated by rotational tomography after surgery. Electrode position was determined to be in scala tympani, scala vestibuli, or with a dislocation from one scala to the other. Speech test results were collected for Freiburg numbers, Freiburg monosyllables, and Oldenburg sentence tests 1 yr after surgery. The Contour array presented with a high rate of scala vestibuli insertions and a high rate of dislocations from scala tympani to scala vestibuli, whereas the Contour Advance array showed a high rate of scala tympani insertions with very few dislocations and few scala vestibuli insertions. Speech tests results varied with respect to the location of the intracochlear electrode position, with insertions into the scala tympani being significantly superior to the scala vestibuli. Results of studying the Contour array influenced the surgical procedure that improved surgical ability to perform insertions into the scala tympani by using the Contour Advance array. In addition, a comparison between Contour and Contour Advance electrode demonstrated an improved mechanical behavior of the Contour Advance electrode with a decrease of dislocation rate. The use of the Contour Advance electrode allows a more atraumatic electrode insertion, which is of interest with extending indications and the use of further advanced coding strategies. The intracochlear electrode position with regard to speech performance results demonstrated advantages of scala tympani insertions.

3D finite element analyses of insertion of the Nucleus standard straight and the Contour electrode arrays into the human cochlea

Previous experimental studies of insertion of the Nucleus standard straight and the Contour arrays into the scala tympani have reported that the electrode arrays cause damage to various cochlear structures. However, the level of insertion-induced damage by these electrode arrays to cochlear structures (the spiral ligament, the basilar membrane and the osseous spiral lamina) has not been quantified. Although it has been suggested that rotation can overcome this resistance and prevent the basilar membrane from being pierced by the tip of the Nucleus standard straight array, there has not been any attempt to study the relationship between the rotation and the reduction of damage to the basilar membrane. In this study, 3D finite element analyses of insertions of the Nucleus standard straight array and the Contour array into the scala tympani have been undertaken. The perforation of the basilar membrane by the tip of the Nucleus standard straight array at the region of 11–14 mm from the round window appears to be compounded by the geometry of the spiral passage of the scala tympani. Anti-clockwise rotations between 25° and 90° applied at the basal end of the electrode array (for the right cochlea) were shown to significantly reduce the contact stresses exerted by the tip on the basilar membrane which support the practice of applying small rotation partway through insertion of electrode array to minimize damage to the basilar membrane. Although the Contour array (with its stylet intact) is stiffer than the Nucleus standard straight array, a slight withdrawal of the stylet from the Contour array before insertion was found to significantly reduce damage by the electrode array to the spiral ligament and the basilar membrane.

Elimination of Facial Nerve Stimulation by Reimplantation in Cochlear Implant Subjects

Perimodiolar intracochlear electrodes with contacts facing towards the modiolus have limited current flow towards the outer wall of the cochlea and therefore, may reduce the occurrence of facial nerve stimulation (FN) in cochlear implant subjects. Facial nerve stimulation is a well-known complication in cochlear implant treatment especially in the group of subjects with otosclerosis. The possible explanation of this side effect is a change of the electrical properties of the otosclerotic bone leading to leakage current and resulting in facial nerve stimulation. Four CI subjects who had been implanted with a Nucleus Mini22 device with a Nucleus Straight electrode between 9 to 12 years ago suffered from severe FN stimulation. Electrode contacts had to be switched off so that they could only use 4, 11, 13, and 15 electrodes of their usual set of 22. The switch off resulted in deteriorating speech understanding over time. Therefore, all subjects were reimplanted with a Nucleus 24R device with a Contour electrode. Preoperatively, the threshold of FN stimulation was obtained on all electrodes subjectively. Intraoperatively, FN stimulation thresholds were measured objectively with both, the old and the new device and were compared. NRT and SRT thresholds were also obtained with the reimplanted device to assure effective electrical stimulation of the auditory nerve. In all four cases the postoperative fitting demonstrated no FN stimulation on all electrodes up to maximum comfortable level. The insertion of the Contour electrode array was complete in three cases, in one case the array could only be inserted partially similarly to the situation before the reimplantation. Speech perception tests showed a significant improvement in all subjects with the new device. Electrodes with modiolar facing contacts and perimodiolar position like the Nucleus Contour electrode reduce the possibility of facial nerve stimulation significantly due to more focused electrical stimulation.

Modiolar Coiling, Electrical Thresholds, and Speech Perception after Cochlear Implantation Using the Nucleus Contour Advance Electrode with the Advance Off Stylet Technique

Perimodiolar electrode arrays were developed in an attempt to improve stimulation of specific neural populations and to decrease electrical thresholds, thereby decreasing power consumption. Postoperative radiographs show that coiling of the arrays is variable. Our previous study explored the relationship between the angle of coiling, threshold levels, and functional outcomes using the Nucleus Contour electrode array. This study compares coiling angle, electrical threshold levels, and speech perception measures with the Nucleus Contour Advance electrode array implanted using the new advance off stylet technique versus the Nucleus Contour electrode array implanted using the standard technique. Retrospective review. University medical center. Forty-two adults and children with normal cochlear anatomy implanted with the Nucleus CI24RCA electrode using the advance off stylet technique with at least 1-year follow-up. Therapeutic. Computer-aided radiographic analysis of perimodiolar electrode placement, electrical threshold measurements, and speech perception outcome measures at 1 year postimplantation. The degree of modiolar coiling was tighter using the new electrode and technique in comparison with standard insertion technique using the Nucleus Contour electrode array. The tighter coiling tended to result in higher electrical thresholds. Lower speech perception outcome measures tended to correlate with a higher degree of coiling. The Nucleus Contour Advance electrode array combined with the advance off stylet technique resulted in a more consistent perimodiolar position. However, the tighter coiling resulted in statistically significant increased electrical thresholds and decreased speech perception outcomes. This finding may be secondary to multiple factors, not just coiling angle.

Psychophysical measures in patients fitted with Contour™ and straight Nucleus electrode arrays

The objective of this study was to compare the psychophysical performance of patients using the Nucleus Contour™ electrode array with that of patients using the straight banded-electrode array. In particular, we wished to consider how psychophysical parameters would differ for an electrode array positioned closer to the modiolus, and how this might influence both patient benefits and the design of speech processing strategies. Nine subjects participated in the study: four used the Nucleus straight array and five used the Nucleus Contour electrode array. Radiographic analyses found that the Contour array lay closer to the modiolus, was more deeply inserted and spanned a larger fractional length of the basilar membrane than the straight banded-electrode array. The results were analysed in terms of array type and of the position of the individual electrode band, both distance from the modiolus and longitudinal placement. Mean threshold was lower for the Contour array but maximum comfortable level was similar. Whereas threshold varied significantly with distance of electrode band from the modiolus, maximum comfortable level did not. Pitch varied fairly regularly with longitudinal position of the stimulated electrode, with the exception of one Contour subject. The forward masking profiles, using moderately loud maskers, were narrower for the Contour array, indicative of more localized neural excitation.

Evaluation of Streamlined Programming Procedures for the Nucleus Cochlear Implant with the Contour Electrode Array

The objective of this study was to evaluate streamlined programming procedures for the Nucleus cochlear implant system with the Contour electrode array. Phase 1 involved an examination of the clinical MAPs for the first 103 recipients implanted with the Contour electrode array in the Melbourne Cochlear Implant Clinic, to examine the ability to predict the entire MAP based on a smaller number of clinically determined T- and/or C-levels. In phase 2, a subset of the streamlined procedures was selected and clinically evaluated, using speech perception and subjective preference measures. In the first study, the clinical MAP was compared with a MAP based on interpolating across three behavioral T-levels and three behavioral C-levels in a group of newly implanted subjects. The second study investigated the use of a single interpolated profile as the basis to creating the entire MAP. Initial evaluation compared the clinical MAP with two streamlined MAPs, one in which the C-level profile was derived from interpolation across a subset of T-levels and one in which the T-level profile was derived from interpolation across a subset of C-levels. In this case, the interpolated profile was based on five behavioral measures. Subsequently, the use of either three or a single T-level measure as the basis for the interpolated T-level profile was evaluated. Eighteen subjects, who were experienced with the clinical MAP before enrollment in the study, participated in the initial evaluation. The subjects were selected to include a group whose RMS deviation from clinical MAP levels, as determined in Phase 1, was greater than that of the wider population. The Phase 1 analysis showed that as expected, larger differences were observed between the clinical and derived MAP levels as interpolation was applied across fewer measured electrodes and that the use of a single interpolated profile to create the entire MAP resulted in the greatest deviation. No significant group mean difference was found in speech perception scores for newly implanted subjects when mapped with the clinical versus the streamlined MAP based on three behavioral T- and three behavioral C-level measures. For some individual subjects, scores were higher with the streamlined MAP. Subjective reports from the comparative performance questionnaire were consistent with these findings. No significant group mean difference in speech perception scores was found in comparing the clinical MAP with the streamlined MAPs based on a single interpolated T- or C-level profile created from five behavioral measures. Individual effects were observed; however, there was no consistent finding across subjects. The use of three rather than five behavioral T-level measures in the procedure did not result in significantly lower group mean scores; however, significantly poorer scores were obtained for three of the 10 individual subjects. The use of a MAP based on a single behavioral measure did result in poorer speech perception scores when compared with the MAP based on five behavioral T-level measures. These findings were consistent with subjective results from the performance questionnaires administered to determine preference for program across a range of listening situations. Two streamlined programming procedures are recommended for use in the clinical setting: (1) interpolating across three measured T-levels and three measured C-levels and (2) interpolating across five measured T- or C-levels and using the interpolated profile for fitting of the alternative profile.