MED-EL Devices Research Articles

Worldwide differences in surgeon intraoperative practices for cochlear implantation

Objective To characterize practice patterns of intraoperative imaging and/or functional confirmation of cochlear implant electrode location worldwide. Methods A cross-sectional survey of otolaryngologists performing cochlear implantation was conducted between March 1 and May 6, 2023. Participants were recruited worldwide using an international otologic society membership email list and at professional meetings. Ninety-seven of the 125 invited participants (78%) completed the survey. Participants were categorized by continent. Results North American surgeons use intraoperative X-rays more frequently than surgeons in Europe and Asia (p < 0.001). Otolaryngologists in Europe and Asia more frequently use no intraoperative imaging (p = 0.02). There is no regional difference between the intraoperative use of electrophysiologic instruments. European and Asian surgeons implant MED-EL devices (p = 0.012) more frequently than North American surgeons, who more frequently use Cochlear Corporation devices (p = 0.003). MED-EL use is related to less frequent intraoperative X-ray use (p = 0.02). Advanced Bionics use is related to more frequent intraoperative CT use (p = 0.03). No significant association existed between years of practice, number of cochlear implantation surgeries performed yearly, volume of pediatric CI practice, and use of intraoperative tools. Conclusion Intraoperative practice for radiologic and functional verification of cochlear implant electrode positioning varies worldwide. Practice guidelines may help establish a standard of care for cochlear implantation.

Influence of overtones and undertones on melody recognition with a cochlear implant with SSD

Many cochlear implant (CI) users have difficulties recognising pitches and melodies because pitch transmission is blurred and shifted. This study investigates whether postlingually deafened adult CI users recognize melodies better when overtones are removed or undertones are added.Fifteen unilaterally postlingually deafened CI users (single sided deafness = SSD) were included aged 22 to 73 years (MW 52, SD 11.6) with CI hearing experience between 3 and 75 months (MW 33, SD 21.0) with varying MED-EL devices. Three short piano melodies were presented to them firstly to the normal-hearing ear and then in modified overtone or undertone variants and the original variant to the CI ear. These variants should be identified as one of the three original melodies. In addition, musical experience and ability were assessed by the Munich Music Questionnaire and the MiniPROMS music tests.The CI users showed the best melody recognition in the fundamental frequency variant. The overtone variant with the third overtone was as good as the original variant with all overtones with regard to melody recognition (p=1). However, the undertone variant with the first undertone was recognised significantly worse than the fundamental version (p=0.032). Furthermore, there was no correlation between musical experience or musical ability and the number of melodies recognised (p>0.1).Since a reduction of overtones did not worsen the melody recognition, overtone reduction should be considered in future music processing programs for the CI. This could reduce the energy consumption of the CI.

The intraoperative relationship between intracochlear electrical field and excitability of the auditory nerve

A limiting factor of cochlear implant (CI) technology is the electrode-contact overlapping spread of the electrode-generated intracochlear electrical field (EF). While the extent of the spread can be reduced with intracochlear ground electrodes, the stimulation level must be increased to reach similar loudness as with monopolar stimulation utilizing an extracochlear ground. In this study, we investigated the relationship between the monopolar intracochlear EF and the minimum stimulation level required for a measurable neural response assessed with electrically evoked compound action potential (eCAP) thresholds in intraoperative settings. Also, the effect of cochlear diameter on the intracochlear EF was evaluated, as narrower intracochlear EFs were found from larger than smaller cochleae in an earlier study.A total of 171 ears of severely-to-profoundly hearing-impaired patients (ages 0.7–89 years; 42.5 ± 27.8 years, mean ± SD) implanted with a Cochlear Nucleus CI522 or CI622 implant and Slim Straight electrode array or with a Med-El Synchrony implant and Flex 28 electrode array were included in the study. Normal anatomy was established and cochlear diameter was measured for all patients from preoperative imaging. Intraoperative intracochlear EF and eCAP threshold measurements were measured for both Cochlear and Med-El devices with the CIs’ back-telemetry options, and EF and eCAP were compared for Cochlear devices.The peak and width of the intracochlear EF correlated with each other (r = 0.46, p < 0.001), and both had an inverse relationship with eCAP thresholds (r = –0.41, p < 0.001 and r = –0.29, p < 0.001, respectively). The peak amplitudes of the intracochlear EF increased towards the apical part of the electrode array with both Cochlear (r = 0.97, p < 0.001) and Med-El (r = 0.80, p = 0.002) devices. The peak amplitudes of the intracochlear EF were shallower across the electrode array in large than in small cochleae (p < 0.05).Our results indicate that the responsiveness of the cochlear nerve is not only dependent on neural health but is also affected by the physical environment of the electrode array, which can be assessed by measuring the intracochlear EF. Further studies are warranted to investigate the detailed characteristics of the intracochlear current spread in CI recipients with varying anatomical features of the cochlea and with electrode arrays with different locations in the scalae or related to the modiolus in the cochleae.

Cochlear Implantation in Obliterated Cochlea: A Retrospective Analysis and Comparison between the IES Stiff Custom-Made Device and the Split-Array and Regular Electrodes.

Anatomical malformations, obliterations of the cochlea, or re-implantations pose particular challenges in cochlear implantation. Treatment methods rely on radiological and intraoperative findings and include incomplete insertion, the implantation of a double array, and radical cochleostomy. In addition, a stiff electrode array, e.g., the IE stiff (IES) custom-made device (CMD, MED-EL), was prescribed individually for those special cases and pre-inserted prior to facilitate cochlear implantation in challenging cases. Data on outcomes after implantation in obliterated cochleae are usually based on individual case reports since standardised procedures are lacking. A retrospective analysis was conducted to analyse our cases on obliterated cochleae treated with MED-EL devices in order to allow the different cases to be compared. Impedances and speech perception data of patients treated with the IES CMD and the double array were retrospectively compared to patients treated with a STANDARD or FLEX electrode array (the REGULAR group). Patients with a Split-Array CMD had a poor speech perception when compared to patients treated with the IES CMD device. Thus, the IES CMD can successfully be used in patients with obliterated cochleae who would otherwise be non-users, candidates for a Split-Array CMD, or candidates for partial insertion with insufficient cochlear coverage.

CI in single-sided deafness

The cochlear implant (CI) as a treatment option for single-sided deafness (SSD) started with a clinical study looking in to the influence of cochlear implantation with a MED-EL device on incapacitating unilateral tinnitus in SSD. The study began in 2003 and was conducted by P. Van de Heyning and his team in Antwerp, Belgium. The first CI in SSD without tinnitus in Germany was implanted by J. Mueller and R. Jacob in Koblenz in 2005. Translational research activities took place since then to evaluate the CI as a treatment option for SSD not only in adults but also in children. They assessed the hearing performance of SSD patients implanted with CI, importance of long electrode arrays in SSD patients, degree of acceptance of CI by SSD children, importance of early CI implantation in SSD children in developing language skills, music enjoyment by hearing with two ears and evidence on spiral ganglion cell body distribution. In 2013, MED-EL was the first CI manufacturer to receive the CE mark for the indication of SSD and asymmetric hearing loss (AHL) in adults and children. In 2019, MED-EL was the first CI manufacturer to get its CI device approved for patients over the age of five with SSD and AHL, by the FDA in the USA. This article covers the milestones of translational research from the first concept to the widespread clinical use of CI in SSD.

Two-phase survey on the frequency of use and safety of MRI for hearing implant recipients

PurposeMagnetic resonance imaging (MRI) is often used to visualize and diagnose soft tissues. Hearing implant (HI) recipients are likely to require at least one MRI scan during their lifetime. However, the MRI scanner can interact with the implant magnet, resulting in complications for the HI recipient. This survey, which was conducted in two phases, aimed to evaluate the safety and performance of MRI scans for individuals with a HI manufactured by MED-EL (MED-EL GmbH, Innsbruck, Austria).MethodsA survey was developed and distributed in two phases to HEARRING clinics to obtain information about the use of MRI for recipients of MED-EL devices. Phase 1 focused on how often MRI is used in diagnostic imaging of the head region of the cochlear implant (CI) recipients. Phase 2 collected safety information about MRI scans performed on HI recipients.Results106 of the 126 MRI scans reported in this survey were performed at a field strength of 1.5 T, on HI recipients who wore the SYNCHRONY CI or SYNCHRONY ABI. The head and spine were the most frequently imaged regions. 123 of the 126 scans were performed without any complications; two HI recipients experienced discomfort/pain. One recipient required reimplantation after an MRI was performed using a scanner that had not been approved for that implant. There was only one case that required surgical removal of the implant to reduce the imaging artefact.ConclusionIndividuals with either a SYNCHRONY CI or SYNCHRONY ABI from MED-EL can safely undergo a 1.5 T MRI when it is performed according to the manufacturer’s safety policies and procedures.

Temporal integration of short-duration pulse trains in cochlear implant listeners: Psychophysical and electrophysiological measurements

While electrically-evoked auditory brainstem response (eABR) thresholds for low-rate pulse trains correlate well with behavioral thresholds measured at the same rate, the correlation is much weaker with behavioral thresholds measured at high rates, such as used clinically. This implies that eABRs to low-rate stimuli cannot be reliably used for objective programming of threshold levels in cochlear implant (CI) users. Here, we investigate whether the use of bunched-up pulses (BUPS), consisting of groups of closely-spaced pulses may be used as an alternative stimulus.Experiment 1 measured psychophysical detection thresholds for several stimuli having a period of 32 ms in nine CI subjects implanted with a Med-EL device. The stimuli differed in the number of pulses present in each period (from 1 to 32), the pulse rate within period (1000 pps and as high as possible for BUPS) and the electrode location (apical or basal). The correlation between psychophysical thresholds obtained for a high-rate (1000 pps) clinical stimulus and for the BUPS stimuli increased as the number of pulses per period of BUPS increased from 1 to 32. This first psychophysical experiment suggests that the temporal processes affecting the threshold of clinical stimuli are also present for BUPS.Experiment 2 measured eABRs on the apical electrode of eight CI subjects for BUPS having 1, 2, 4, 8, 16 or 32 pulses per period. For most subjects, wave V was visible for BUPS having up to 16 pulses per period. The latency of wave V at threshold increased as a function of the number of pulses per period, suggesting that the eABR reflects the integration of multiple pulses at such low levels or that the neural response to each individual pulse increases along the sequence due to facilitation processes. There was also a strong within-subject correlation between electrophysiological and behavioral thresholds for the different BUPS stimuli. This demonstrates that the drop in behavioral threshold obtained when increasing the number of pulses per period of the BUPS can be measured electrophysiologically using eABRs. In contrast, the across-subject correlation between eABR thresholds for BUPS and clinical thresholds remained relatively weak and did not increase with the number of pulses per period. Implications of the use of BUPS for objective programming of CIs are discussed.

Effect of Stimulation Rate on Speech Understanding in Older Cochlear-Implant Users.

Cochlear implants (CIs) are considered a safe and effective intervention for more severe degrees of hearing loss in adults of all ages. Although older CI users ≥65 years of age can obtain large benefits in speech understanding from a CI, there is a growing body of literature suggesting that older CI users may not perform as well as younger CI users. One reason for this potential age-related limitation could be that default CI stimulation settings are not optimal for older CI users. The goal of this study was to determine whether improvements in speech understanding were possible when CI users were programmed with nondefault stimulation rates and to determine whether lower-than-default stimulation rates improved older CI users' speech understanding. Sentence recognition was measured acutely using different stimulation rates in 37 CI users ranging in age from 22 to 87 years. Maps were created using rates of 500, 720, 900, and 1200 pulses per second (pps) for each subject. An additional map using a rate higher than 1200 pps was also created for individuals who used a higher rate in their clinical processors. Thus, the clinical rate of each subject was also tested, including non-default rates above 1200 pps for Cochlear users and higher rates consistent with the manufacturer defaults for subjects implanted with Advanced Bionics and Med-El devices. Speech understanding performance was evaluated at each stimulation rate using AzBio and Perceptually Robust English Sentence Test Open-set (PRESTO) sentence materials tested in quiet and in noise. For Cochlear-brand users, speech understanding performance using non-default rates was slightly poorer when compared with the default rate (900 pps). However, this effect was offset somewhat by age, in which older subjects were able to maintain comparable performance using a 500-pps map compared with the default rate map when listening to the more difficult PRESTO sentence material. Advanced Bionics and Med-El users showed modest improvements in their overall performance using 720 pps compared with the default rate (>1200 pps). On the individual-subject level, 10 subjects (11 ears) showed a significant effect of stimulation rate, with 8 of those ears performing best with a lower-than-default rate. Results suggest that default stimulation rates are likely sufficient for many CI users, but some CI users at any age can benefit from a lower-than-default rate. Future work that provides experience with novel rates in everyday life has the potential to identify more individuals whose performance could be improved with changes to stimulation rate.

The Relationship between Electrical Stapedius Reflex Thresholds and Behaviorally Most Comfortable Levels in Experienced Cochlear Implant Users.

Programming the cochlear implant's speech processor with subjective methods in young, uncooperative children is difficult. Since young children cannot provide adequate feedback to the clinician, objective methods which do not require patient's response were often used. Electrical Stapedius Reflex Test is one of the most common procedures used. The goal of this study was to investigate the relationship between electricalstapedius reflex thresholds and behaviorally most comfortable levels in experienced cochlear implant users. The patients implanted with two brands of cochlear implants were compared in terms of electrical stapedius reflex thresholds versus most comfortable levels. Speech tests results were also compared between the two groups. 46 cochlear implanted patients who had at least 1 year of cochlear implant experience were included in the study. 28 patients were implanted with Nucleus, 18 patients with Med-El devices. Moderate correlations were obtained between Electrical Stapedius Reflex (ESR) thresholds and C levels in Nucleus users; higher correlations were obtained for Med-El patients. ESR thresholds were present at higher levels than MCL/C levels in both Nucleus and Med-El users. No significant difference was obtained between the two groups in terms of speech tests. ESR test can be very informative for programming young and uncooperative patients.

Causes and frequency of cochlear explantation

Background: The cochlear implant (CI) is unique among medical devices in that it serves as a neurosensory prosthesis capable of restoring or providing de novo the sense of hearing to its users. Causes of cochlear device explantation are divided primarily into device failures and medical failures. Study design: Retrospective and prospective analysis. Objective: determine the causes and the frequency of device and medical failure. Patients and Methods: The study involve 17 patients who had cochlear explantation from total implantation 766 patients in the department of otolaryngology in AL-Yarmouk teaching hospital during period from April 2008 to March 2018, and the data was collected from operative notes that is documented in patients files. Results: A total of 766 implants were performed from April 2008 to March 2018, with 17 devices explanted, the implanted devices were 45.8% Cochlear nucleus devices, and 27.5% were MED-EL devices and 26.6%. Where Advance bionics. The overall failure rate was 17 of 766 (2.22%) of which 13 (76.47%)due to medical failures and 4 (23.5%) due to device failures. Patients with cochlear nucleus devices underwent 9 explants (2.56% failure rate) of which 8 (88.9%) was medical failures and 1(11.1%) was device failures. Patients with MED-EL underwent 3 explants (1.42% failure rate), which all of them was due to device failures Patients with advance bionics underwent 5 explants (2.45% failure rate) all of them was medical failure. Medical failures included wound infection with wound breakdown, wound infection with flap necrosis, hematoma, cholesteatoma and biofilm. Device failure include hard failure and soft failure. Over all the average time to explantation was 559days (range, 10-3468 days). Conclusion: Overall, cochlear explantation rate is low. The medical causes was more common and more with cochlear nucleus device type. the device failure rate was more common with MED-EL device type.

Electrode impedance changes over time in MED El cochlear implant children recipients: Relation to stimulation levels and behavioral measures

Objective: Electrode impedance measures resistance encountered by electric current passing through wires, electrodes and biological tissue. This study was designed mainly to evaluate changes in electrode impedance values and psycho-electric parameters changes (i.e. threshold levels, comfortable levels, and dynamic range) in cochlear implant patients over time. Methods: It was a prospective study encompassing 20 patients implanted by MED-EL device programd using behavioral programs. Electrical stimulation levels and electrode impedance values were examined at 0, 1, 3 and 6 months after the first fitting session. Results: Electrode impedance values were reduced from the time of activation to the 6 months visit. Most comfortable levels increased and dynamic range widened until the 6 months visit. There was an inverse correlation between impedance values and most comfortable level as well as dynamic range, over time. Conclusion: Frequent monitoring of electrode impedance (for device and electrodes problems) and electric stimulation levels (for better performance, mapping and habituation) during the first 6 months of implant use is recommended.

Twenty years of experience in revision cochlear implant surgery: signs that indicate the need for revision surgery to audiologists.

To report device failures, audiological signs and other reasons for revision cochlear implant surgery, and discuss indications for revision surgery. Revision procedures between November 1997 and August 2017 were retrospectively analysed. Over 20 years, 2181 cochlear implant operations were performed, and 114 patients underwent 127 revision operations. The revision rate was 4.67 per cent. The full insertion rate for revision cochlear implant surgery was 88.2 per cent. The most frequent reasons for revision surgery were: device failure (59 per cent), wound breakdown (9.4 per cent) and electrode malposition (8.7 per cent). The device failure rate was: 2.78 per cent for Advanced Bionics, 1.82 per cent for Cochlear and 5.25 per cent for Med-El systems. The number of active electrodes was significantly increased only for Med-El devices after revision surgery. The most common complaints among 61 patients were: gradually decreased auditory performance, sudden internal device shutdown and headaches. The most common reason for revision surgery was device failure. Patients should be evaluated for device failure in cases of: no hearing despite appropriate follow up, side effects such as facial nerve stimulation, and rejection of speech processor use in paediatrics. After revision surgery, most patients have successful outcomes.

Investigating the Effect of Cochlear Size in Insertion of Electrode Depth in Patients with Cochlear Implantation evaluated by CT-Scan

Background Cochlear implant surgery is an invasive procedure for patients with bilateral Sensorineural hearing loss and may cause some risks such as cochlear damage. We aimed to evaluate the effectiveness of cochlear measures obtained by computed tomography (CT) scan in predicting depth of cochlear implant insertion. Materials and Methods This study was conducted in a retrospective and cross-sectional study on 39 patients undergoing cochlear implantation with MED-EL Device. High-resolution radiographs provided preoperative by CT-Scan were used to determine electrode array insertion depth and diameter of the cochlea’s basal turn. The insertion was considered deep when the electrode was placed at least 22 mm into the cochlea. Demographic data, CT-Scan results and cochlear implantation outcomes (deep or shallow) were evaluated. Data were analyzed by SPSS22 software and the significance level was less than 0.05. Results The mean age of patients was 8.026±1.77 years. The depth of insertion of the electrode in 34 (87.18%) patients was deep and in 5 (12.82%) patients was shallow that the difference was statistically significant (P<0.05). Mean size of cochlear in deep group was significantly higher than shallow group (5.89±0.39 vs. 5.2±0.25 mm respectively). There was a significant relationship between age and gender of patients in deep group, which females and patients with lower age reported a higher level of shallow insertion. Conclusion The results of present study showed the efficacy of using CT-Scan before surgery to predict the depth of implant placement and help it to select the appropriate prosthesis.

Measurement of pitch perception as a function of cochlear implant electrode and its effect on speech perception with different frequency allocations

Objective: An experiment was conducted to investigate the possibility that speech perception could be improved for some cochlear implant (CI) users by adjustment of the frequency allocation to the electrodes, following assessment of pitch perception along the electrode array.Study sample: Thirteen adult CI users with MED-EL devices participated in the study.Design: Pitch perception was assessed for individual CI electrode pairs using the Pitch Contour Test (PCT), giving information on pitch discrimination and pitch ranking for adjacent electrodes. Sentence perception in noise was also assessed with ten different frequency allocations, including the default.Results: Pitch perception was found to be poorer for both discrimination and ranking scores at either end of the electrode array. A significant effect of frequency allocation was found for sentence scores [F(4.24,38.2) = 7.14, p < 0.001] and a significant interaction between sentence score and PCT ranking score for basal electrodes was found [F(4.24,38.2) = 2.95, p = 0.03]. Participants with poorer pitch perception at the basal end had poorer scores for some allocations with greater basal shift.Conclusions: The results suggest that speech perception could be improved for CI users by assessment of pitch perception using the PCT and subsequent adjustment of pitch-related stimulation parameters.

Clinically recorded cortical auditory evoked potentials from paediatric cochlear implant users fitted with electrically elicited stapedius reflex thresholds

ObjectivesThis study aimed to objectively evaluate access to soft sounds (55 dB SPL) in paediatric CI users, all wearing MED-EL (Innsbruck, Austria) devices who were fitted with the objective electrically elicited stapedius reflex threshold (eSRT) fitting method, to track their cortical auditory evoked potential (CAEP) presence and latency, and to compare their CAEPs to those of normal-hearing peers. MethodsForty-five unilaterally implanted, pre-lingually deafened MED-EL CI users, aged 12–48 months, underwent CAEP testing in the clinic at regular monthly intervals post switch-on. CAEPs were recorded in response to short speech tokens /m/, /g/ and /t/ presented in the free field at 55 dB SPL. Twenty children with normal hearing (NH), similarly aged, underwent CAEP testing once. ResultsThe proportion of present CAEPs increased and CAEP P1 latencies reduced significantly with post-implantation duration. CAEPs were scored based on their presence and age-appropriate P1 latency. These CAEP scores increased significantly with post-implantation duration. CAEP scores were significantly worse for the /m/ speech token compared to the other two tokens. Compared to the NH group, CAEP scores were significantly smaller for all post-implantation test intervals. ConclusionsThis study provides clinicians with a first step towards typical ranges of CAEP presence, latency, and derived CAEP score over the first months of MED-EL CI use. CAEPs within these typical ranges could validate intervention whereas less than optimum CAEPs could prompt clinicians to seek solutions in a timely manner. CAEPs could clinically validate whether a CI provides adequate access to soft sounds. This approach could form an alternative to behavioural soft sound access verification.

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.

Evaluation of an artifact reduction strategy for electrically evoked auditory steady-state responses: Simulations and measurements

BackgroundElectrically evoked steady-state response (EASSR) recording is a measure of neuronal response strength after continuous electrical stimulation of the auditory system. In order to suppress the large electrical artifact generated by intracochlear electrical stimulation, a sophisticated artifact reduction processing strategy (“Hofmann procedure”) has been proposed (Hofmann and Wouters, 2010). So far, EASSR recordings with artifact reduction procedures were reported only in cochlear implant (CI) users implanted with Cochlear devices (Macquarie, Australia). New methodHere, we demonstrate the application of the Hofmann procedure in CI users implanted with MED-EL (Innsbruck, Austria) devices. To demonstrate potential limitations of the procedure, we calculated discrete time Fourier transformations (DTFT) of various pulse patterns which may be used for EASSR. ResultsEASSR recordings were obtained in three subjects and processed with the Hofmann procedure. Neural response amplitude growth functions and phase for modulated and unmodulated pulse trains at various stimulation rates could be assessed. Simulations of three different interpolation methods aimed to suppress the electrical artifact show that the interpolation of a sinusoidal signal in a temporal window between 0 and 1 ms has demonstrated negligible impact on the spectral amplitude of the signal with a superior performance of a spline interpolation. Comparison with existing methodThe Hofmann procedure, initially developed for recording EASSRs with CIs from the manufacturer Cochlear, was validated for MED-EL devices. ConclusionIt is feasible to record EASSRs with the described measurement setup and CIs from the manufacturer MED-EL.

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.

Using ILD or ITD Cues for Sound Source Localization and Speech Understanding in a Complex Listening Environment by Listeners With Bilateral and With Hearing-Preservation Cochlear Implants.

To assess the role of interaural time differences and interaural level differences in (a) sound-source localization, and (b) speech understanding in a cocktail party listening environment for listeners with bilateral cochlear implants (CIs) and for listeners with hearing-preservation CIs. Eleven bilateral listeners with MED-EL (Durham, NC) CIs and 8 listeners with hearing-preservation CIs with symmetrical low frequency, acoustic hearing using the MED-EL or Cochlear device were evaluated using 2 tests designed to task binaural hearing, localization, and a simulated cocktail party. Access to interaural cues for localization was constrained by the use of low-pass, high-pass, and wideband noise stimuli. Sound-source localization accuracy for listeners with bilateral CIs in response to the high-pass noise stimulus and sound-source localization accuracy for the listeners with hearing-preservation CIs in response to the low-pass noise stimulus did not differ significantly. Speech understanding in a cocktail party listening environment improved for all listeners when interaural cues, either interaural time difference or interaural level difference, were available. The findings of the current study indicate that similar degrees of benefit to sound-source localization and speech understanding in complex listening environments are possible with 2 very different rehabilitation strategies: the provision of bilateral CIs and the preservation of hearing.

Electrode migration after cochlear implant surgery: more common than expected?

The overall complication rate of cochlear implant surgery is low and so-called electrode failures (electrode migration, misplacement, etc.,) account for only a minority of all complications. The aim of this study was to explore the prevalence of electrode migration as the cause for increased impedance values and non-auditory stimulation in the basal channels. Within the scope of a quality control process, the cochlear implant database of the Kuopio University Hospital (Finland) was reviewed. Patients with gradual elevation of impedance values and/or non-auditory stimulation of the basal electrode channels were re-examined and cone-beam computed tomography was administered. There were 162 cochlear implant recipients and 201 implanted devices registered in the database. A total of 18 patients (18 devices) were identified having significantly increased impedance values or non-auditory stimulation of the basal electrodes. Cone-beam computed tomography revealed extra-cochlear electrodes in 12 of these patients due to the migration of the electrode array. All extruded electrodes were lateral wall electrodes, i.e., straight electrode arrays (Cochlear CI422 and Med-El devices). The most common feature of electrode migration was the gradual increase of the impedance values in the basal electrodes, even though telemetry could also be unsuspicious. Electrode migration after cochlear implant surgery may be more common than previously reported. At surgery, special attention should be paid to the reliable fixation of the electrode array. This study underlines the importance of postoperative imaging after cochlear implant surgery.