Bilocated Intracochlear Electrocochleography During Cochlear Implantation to Provide Surgical Feedback.

A cochlear implant (CI) is a hearing device introduced in the 1980s for profoundly deaf subjects who gained little or no benefit from powerful hearing aids. This device comprises an electrode array inserted in the cochlea, connected to an internal receiver, and an externally worn speech processor. The CI transforms acoustic signals into electrical currents which directly stimulate the auditory nerve. Since the early 1990s, cochlear implantation in children has been developing rapidly. Although it is still difficult to predict how a child will perform with a cochlear implant, the success of cochlear implantation can no longer be denied. In this paper, some recent papers and reports, and the results of the various Nijmegen cochlear implant studies, are reviewed. Issues about selection, examinations, surgery and the outcome are discussed. Overall, our results were comparable with those of other authors. It can be concluded that cochlear implantation is an effective treatment for postlingually deaf as well as prelingually (congenital or acquired) deaf children with profound bilateral sensorineural deafness.

Objective(s):Robotic-assisted electrode array (EA) insertion is a promising technique that may enhance hearing preservation in cochlear implant (CI) surgery. The purpose of our study is to understand the extent to which robotic-assisted EA insertion improves hearing preservation.Methods:Twenty-four adult patients underwent CI surgery with manual EA insertion and 27 adult patients underwent CI surgery with robotic-assisted EA insertion using the iotaSOFT system. The EAs used included the Flex 20/24/26. The primary outcome variable was low frequency pure-tone average (LFPTA), defined as mean audiometric threshold at 125, 250, and 500 Hz. This was measured preoperatively, at initial activation (within 4 weeks of surgery), and subsequently at 2 weeks, 3 months, 6 months, and 1 year. Functional acoustic hearing was defined as LFPTA < 80 dB HL.Results:Seventeen out of 24 patients (71%) in the manual insertion group and 23 out of 27 patients (85%) in the robotic-assisted EA insertion group had preserved functional acoustic hearing (< 80 dB HL) up till 1 year (Fisher’s exact test (two-tailed) is not statistically significant, p = 0.31). The number needed to treat with robotic-assisted EA insertion to prevent one additional negative outcome of loss of functional acoustic hearing would be 7 (1/0.14).Conclusion:Robotic-assisted EA insertion is associated with improved hearing preservation over 1 year compared with manual insertion. Hearing preservation leads to improved outcomes and therefore every effort should be made to preserve the delicate structure and function of the cochlea during EA insertion. Robotic-assisted EA insertion advances that objective.Level of Evidence:III (cohort study).

IntroductionElectrocochleography (ECochG) is increasingly used in cochlear implant (CI) surgery, in order to monitor the effect of insertion of the electrode array aiming to preserve residual hearing. However, obtained results are often difficult to interpret. Here we aim to relate changes in ECochG responses to acute trauma induced by different stages of cochlear implantation by performing ECochG at multiple time points during the procedure in normal-hearing guinea pigs.Materials and methodsEleven normal-hearing guinea pigs received a gold-ball electrode that was fixed in the round-window niche. ECochG recordings were performed during the four steps of cochlear implantation using the gold-ball electrode: (1) Bullostomy to expose the round window, (2) hand-drilling of 0.5–0.6 mm cochleostomy in the basal turn near the round window, (3) insertion of a short flexible electrode array, and (4) withdrawal of electrode array. Acoustical stimuli were tones varying in frequency (0.25–16 kHz) and sound level. The ECochG signal was primarily analyzed in terms of threshold, amplitude, and latency of the compound action potential (CAP). Midmodiolar sections of the implanted cochleas were analyzed in terms of trauma to hair cells, modiolar wall, osseous spiral lamina (OSL) and lateral wall.ResultsAnimals were assigned to cochlear trauma categories: minimal (n = 3), moderate (n = 5), or severe (n = 3). After cochleostomy and array insertion, CAP threshold shifts increased with trauma severity. At each stage a threshold shift at high frequencies (4–16 kHz) was accompanied with a threshold shift at low frequencies (0.25–2 kHz) that was 10–20 dB smaller. Withdrawal of the array led to a further worsening of responses, which probably indicates that insertion and removal trauma affected the responses rather than the mere presence of the array. In two instances, CAP threshold shifts were considerably larger than threshold shifts of cochlear microphonics, which could be explained by neural damage due to OSL fracture. A change in amplitudes at high sound levels was strongly correlated with threshold shifts, which is relevant for clinical ECochG performed at one sound level.ConclusionBasal trauma caused by cochleostomy and/or array insertion should be minimized in order to preserve the low-frequency residual hearing of CI recipients.

Identifying Slim Modiolar Electrode Tip Fold-Over With Intracochlear Electrocochleography.

The round window insertion (RWI) and cochleostomy approaches are the 2 most common surgical techniques used in cochlear implantation (CI). However, there is no consensus on which approach is ideal for electrode array insertion, in part because visualization of intracochlear electrode position is challenging, so postoperative assessment of intracochlear electrode contact is lacking. To measure and compare electrode array position between RWI and cochleostomy approaches for CI insertion. Retrospective case-comparison study of 17 CI users with Med-El standard-length electrode arrays who underwent flat-panel computed tomography scans after CI surgery at a tertiary referral center. The data was analyzed in October 2015. Flat-panel computed tomography scans were collected between January 1 and August 31, 2013, for 22 electrode arrays. The surgical technique was identified by a combination of operative notes and imaging. Eight cochleae underwent RWI and 14 cochleae underwent cochleostomy approaches anterior and inferior to the round window. Interscalar electrode position and electrode centroid distance to the osseous spiral lamina, lateral bony wall, and central axis of the modiolus. Nine participants were men, and 8, women; the mean age was 54.4 (range, 21-64) years. Electrode position was significantly closer to cochlear neural elements with RWI than cochleostomy approaches. Between the 2 surgical approaches, the RWI technique produced shorter distances between the electrode and the modiolus (mean difference, -0.33 [95% CI, -0.29 to -0.39] mm in the apical electrode; -1.42 [95% CI, -1.24 to -1.57] mm in the basal electrode). This difference, which was most prominent in the first third and latter third of the basal turn, decreased after the basal turn. The RWI approach was associated with an increased likelihood of perimodiolar placement. Opting to use RWI over cochleostomy approaches in CI candidates may position electrodes closer to cochlear neural substrates and minimize current spread. These findings need to be interpreted in light of the increased potential for osseous spiral lamina trauma with reduced distances between the electrode array and modiolus.

To describe a method of cochlear implantation in which the opening of the cochlea and the electrode array insertion are performed under water (underwater technique). Retrospective patient review. Academic tertiary referral center. Fifteen implantations in children and adult patients with residual hearing at the frequencies 250, 500, and 1000 Hz on the unaided preoperative pure-tone audiometry were included in this study. Cochlear implantation with a conventional full-length electrode, in which the opening of the cochlea and the electrode array insertion are performed after the tympanic cavity was filled with body-temperature Ringer solution. Changes on residual hearing 6 to 8 weeks after surgery and at subsequent follow-up appointments were analyzed. Preservation of residual hearing was defined as measurable postoperative threshold at the frequencies 250, 500, and 1000 Hz. Overall postimplant hearing preservation 6 to 8 weeks after implantation was achieved in 13 of the patients (87%). Subsequent follow-up was performed on average 15.2 months after surgery (range, 7-32) in 14 out of 15 patients. At this late postoperative evaluation preservation of hearing was recorded in nine patients (64%), whereas in the remaining five patients (36%) no residual hearing was measured. The underwater technique offers a reliable nontraumatic method for electrode array insertions during cochlear implantation. The method respects the physiology of the cochlea und minimizes the pressure variations during cochlear opening and implantation.

To report residual hearing preservation outcomes in patients with low frequency hearing, after cochlear implant (CI) electrode insertion with two types of electrode arrays: one straight and other perimodiolar, when using intraoperative intracochlear electrocochleography (ECochG) during (CI) electrode insertion. Prospective, randomized study. Tertiary referral otology center. Fifteen patients ranging from 33 to 54 years old (mean 51.19). They had been diagnosed with a bilateral, profound sensorineural hearing loss and treated with a unilateral cochlear implant: eight of them with the CI532 and seven of them with the CI522 (Cochlear Ltd, Sydney, Australia). Pure-tone audiometry was performed preoperatively and at 1 and 6 months postoperatively. Interoperatively, intracochlear ECochG was performed using the apical-most electrode. The amplitude of the first harmonic was plotted and monitored in real time by the audiologist-surgeon team during their CI electrode insertion. The different ECoch patterns of the insertion track were recorded and analyzed. In 12 cases ECochG responses were successfully recorded. In three cases no ECochG responses could be recorded with no residual hearing observed postoperatively in two of them. With respect to the first harmonic amplitude changes, we found: four cases with an overall increase in amplitude measured from the beginning of insertion until completion, all of them showed residual hearing (<15 dB HL) at 6 months postoperation. Three cases with an increasing amplitude at the beginning of insertion, with a decrease in amplitude as insertion progressed to completion, in two cases dropping of residual hearing (15-30 dB HL) were observed after 6 months postoperation and, in one case, complete residual hearing was observed at 6 months postoperatively. And finally five cases presented amplitudes at the start of insertion with modifications of amplitude during the insertion dynamic, with increasing and descending in amplitude range during the whole insertion, two of them showed residual hearing at 6 months postoperation and three cases a drop of residual hearing (15-30 dB HL) was observed after 6 months postoperation. No statistical differences between CI532 and CI522 electrodes were found. Data of the ECochG responses are also presented (p value ≥ 0.05). ECochG is a useful tool to evaluate the residual hearing in CI patients with straight and perimodiolar cochlear implant. More studies are needed to fully understand the relationship between ECochG and the presence of residual hearing, cochlear trauma, and functional outcomes.

Conclusions: The straight electrode array with length of 31 mm can be fully inserted using round window insertion in cochlear implantation with Mondini’s deformity. It is a safe and effective process, but also a challenging task of the full implantation in children with Mondini’s deformity.Objective: The aim of this study is to discuss whether the straight electrode array with a length of 31 mm could be fully inserted in cochlear implantation with Mondini’s deformity.Methods: A chart review of 30 patients undergoing cochlear implantation with Mondini’s deformity using the electrode array with length of 31 mm was undertaken from January 2012 and December 2015 in Anhui Provincial Hospital.Results: Full insertion of the straight electrode array with length of 31 mm were performed successfully in all patients with Mondini’s deformity using round window insertion. Resistance was not encountered while introducing the electrodes. Ten of 30 patients had cerebrospinal fluid drainage during cochlear implantation. Cerebrospinal fluid drainage was controlled with small pieces of temporalis fascia packing round window in all patients. Intra-operative neural response telemetry was performed in all patients, and results were good. The result of X-ray showed proper placement of the cochlear implant electrode array. During surgery, no patients had experienced any immediate or delayed post-operative complications such as wound infection, intracranial complication, extrusion, or migration of the implant during an average follow-up period of 6–36 months.

To preserve residual hearing during cochlear implant (CI) surgery it is desirable to use intraoperative monitoring of inner ear function (cochlear monitoring). A promising method is electrocochleography (ECochG). Within this project the relations between intracochlear ECochG recordings, position of the recording contact in the cochlea with respect to anatomy and frequency and preservation of residual hearing were investigated. The aim was to better understand the changes in ECochG signals and whether these are due to the electrode position in the cochlea or to trauma generated during insertion. During and after insertion of hearing preservation electrodes, intraoperative ECochG recordings were performed using the CI electrode (MED-EL). During insertion, the recordings were performed at discrete insertion steps on electrode contact 1. After insertion as well as postoperatively the recordings were performed at different electrode contacts. The electrode location in the cochlea during insertion was estimated by mathematical models using preoperative clinical imaging, the postoperative location was measured using postoperative clinical imaging. The recordings were analyzed from six adult CI recipients. In the four patients with good residual hearing in the low frequencies the signal amplitude rose with largest amplitudes being recorded closest to the generators of the stimulation frequency, while in both cases with severe pantonal hearing losses the amplitude initially rose and then dropped. This might be due to various reasons as discussed in the following. Our results indicate that this approach can provide valuable information for the interpretation of intracochlearly recorded ECochG signals.

Cochlear implant surgery is a procedure that requires delicate insertion of an electrode array into the inner ear. This paper reports the clinical motivation, design considerations, analysis, and design optimization of a new robot for electrode arrays insertion. This paper describes a new approach for coordinated insertion of perimodiolar electrode arrays in order to minimize shape discrepancy between the shape of the electrode array and the shape of the inner ear anatomy. A new design of a 3-degrees-of-freedom (DoF) parallel robot with wire-actuated prismatic legs is presented. The dimensional synthesis of the robot design was based on satisfying the accuracy, speed, system size, and workspace requirements. The robot prototype is validated experimentally to execute electrode insertions in plastic models of temporal bones.

Surgical complication related to an electrode array in cochlear implantation is rare; however, in cases with cochlear ossification after bacterial meningitis, the electrode array insertion can be problematic. The patient complained of an aggravated hearing impairment after bacterial meningitis. He was performed cochlear implantation. Both intraoperative neural response telemetry (NRT) and impedance telemetry results were normal. However, postoperative transorbital x-ray revealed only partial insertion of the electrode array. Four days after the surgery, he complained dizziness. Postoperative temporal bone CT showed malposition of the electrode array into the vestibule. Revision surgery was performed and a new electrode array was fully inserted after further drilling out into the cochleostomy window. Though intraoperative NRT and impedance telemetry are normal, misdirection of an electrode array can occur. Therefore, it should be considered that intraoperative radiologic examination is used after insertion of an electrode array for assessment of an electrode array location. (J Clinical Otolaryngol 2011;22:86–89)

Cochlear implants enable improvements in speech perception, but music perception outcomes remain variable. Image-guided cochlear implant programming has emerged as a potential programming strategy for increasing the quality of spectral information delivered through the cochlear implant to improve outcomes. To perform 2 experiments, the first of which modeled the variance in music perception scores as a function of electrode positioning factors, and the second of which evaluated image-guided cochlear implant programming as a strategy to improve music perception with a cochlear implant. This single-center, prospective study recruited 50 adult patients with at least 6 months of cochlear implant listening experience and normal cochlear anatomy to participate in experiment 1 from 2013 to 2023. Data analysis was conducted from January to February 2024. Thirty-four of the 50 patients from experiment 1 also completed experiment 2. Cochlear implant programming using a computed tomography-guided electrode selection strategy. University of Washington Clinical Assessment of Music score, including subtests of pitch discrimination thresholds, isochronous familiar melody recognition, and timbre recognition. Of 50 participants, 20 (40%) were female, and the mean (SD) age was 57.7 (16.4) years. Experiment 1 suggested that better music perception abilities in the 50 participants were associated with patients who were younger and had a postlingual onset of deafness, as well as electrode arrays with a full scala tympani insertion, higher modiolar distance, and shallower insertion depth. Experiment 2 suggested improvements in melody recognition in the 34 participants using the image-guided cochlear implant programming strategy. Patients with apical electrodes that were deactivated were more likely to demonstrate an improvement in their pitch perception thresholds with the image-guided strategy, likely due to the low-frequency stimuli used in the University of Washington Clinical Assessment of Music. This study identified patient and device factors that were associated with music perception outcomes with a cochlear implant. These findings suggest that a personalized, image-guided approach to programming may improve music perception abilities for patients with cochlear implants.

To determine whether a change in cochlear implant technology and electrode array design affects electrophysiological, behavioral, and functional measures of audition in pediatric cochlear implant users. Prospective nonrandomized control study over 6 months postimplantation. Tertiary referral pediatric hospital. A total of 115 children using unilateral cochlear implants were included in this study. Subjects were divided into 3 groups: 1) 38 using the Nucleus 24M straight array device, 2) 20 using the perimodiolar Nucleus 24RCS Contour array, and 3) 57 using the perimodiolar Nucleus 24RE array with advance off stylet insertion. The mean ages at implantation were 4.85 +/- 4 (24M), 3.88 +/- 3.4 (24RCS), and 5.41 +/- 4.36 years (24RE; not significant, p > 0.05). The electrically evoked compound action potential (ECAP) and the electrically evoked stapedius reflex and behavioral measures of stimulation threshold were evoked by stimulation of basal, mid, and apical electrodes. These measures were completed at regular intervals over 6 to 12 months of implantation. Age-appropriate speech perception skills were also assessed during this period. The 24RE array group had significantly lower ECAP and behavioral thresholds compared with the 24M and 24RCS array groups. The largest reductions of ECAP thresholds in the precurved array group were observed upon apical and basal electrode stimulation. Electrically evoked stapedius reflex thresholds were significantly higher in the 24RE group as compared with 24M and 24RCS groups. Comparing age-matched groups, open- and closed-set speech perception test scores were significantly higher in the 24RE array group. The precurved Freedom 24RE cochlear implant potentially provides a wider range of stimulation levels and better functional results than the straight electrode 24M and the precurved 24RCS devices in profoundly hearing impaired children.

Cochlear implantation is currently regarded as a safe and minimally invasive procedure. However, cochlear implantation can have an impact on vestibular function, despite the lack of correlation between patient symptomatology and damage in vestibular tests. Thus, the present study aims to analyze the presence of hydrops and histological reactions at the level of the vestibule after cochlear implantation with dexamethasone pump delivery in Macaca fascicularis (Mf). A detailed histological study was conducted on a total of 11 Mf. All 11 Mf were divided into three groups: 5 Mf were implanted with an electrode array HL-14 connected to a pump delivering FITC-dextran for 24 h (Group A); 4 Mf were implanted with a CI electrode array attached to a pump for FITC-dextran delivery for 7 days (Group B); and 2 Mf were considered the control group, without any kind of cochlear device implantation (Group C). After drug deliver, the selected macaques were euthanized to collect tissue samples for histological analysis. An experienced observer, focusing on the utricle and saccule areas, conducted a blinded inner ear histology analysis. Surgical procedures were successfully performed in all cases. No signs of cochlear reaction to the device were observed, including neither collapse nor fibrosis. Endolymphatic sinus dilatation was observed in Mf4A and Mf3B, while cochlear hydrops was observed in Mf3A. The mean areas of the utricle and saccule exhibited some statistically significant differences, specifically, in the saccule between groups C and both groups A (p = 0.028) and B (p = 0.029); however, no significant differences were observed between groups A and B or among comparisons of the utricle. A significant concern relates to the safety of cochlear implantation with regard to vestibular preservation and hearing. New advancements in electrode arrays, such as CI devices coupled with delivery pumps, pose a challenge in maintaining minimally traumatic surgical concept-based procedures without affecting the inner ear homeostasis. The implantation of this device may cause vestibular hydrops in the saccule, indicating that the longer the time of substance release, the greater the grade of hydrops evidenced at the saccular level. Apart from this finding, the risk of histological damage to the vestibule is low.

Speech recognition outcomes with a cochlear implant (CI) are highly variable. One factor suggested to correlate with CI-aided speech recognition is frequency-to-place mismatch, or the discrepancy between the natural tonotopic organization of the cochlea and the electric frequency allocation of the CI electrodes within the patient's cochlea. To evaluate the association between frequency-to-place mismatch and speech recognition outcomes in a large cohort of postlingually deafened adult CI users, while controlling for various clinical factors known to be associated with those outcomes. This retrospective cohort study used data from a CI program at a tertiary medical center and included CIs from postlingually deafened adult CI users. After excluding patients whose data were not logged, patients with implantations occurring between 2016 and 2023 were included in the analysis. The data were extracted in November 2023. Results of the Consonant-Nucleus-Consonant (CNC) monosyllabic word recognition test measured in the CI-aided alone condition 1 month, 3 months, 6 months, and 12 months after activation served as the main outcome. The independent variables included frequency-to-place mismatch, electrode array type, mean modiolar distance, electrode position, age at implantation, biological sex, contralateral hearing abilities, time since CI activation (test interval), and daily device use. In 498 CIs from 447 postlingually deafened adults (mean [SD] age, 63.1 [17.1] years; 271 [54.4%] CIs with male users), frequency-to-place mismatch was negatively correlated with CI-aided speech recognition outcomes, but the association was only significant for precurved electrode arrays and not straight electrode arrays. In the linear mixed effects model for straight electrode arrays, only test interval (β = 1.14 [95% CI, 0.90-1.38]) and daily device use (β = 0.90 [95% CI, 0.42-1.38]) were correlated with the improvement of word recognition over the first year of device use. In the model for precurved electrode arrays, mismatch at 1500 Hz (β = -0.011 [95% CI, -0.011 to -0.006]), scalar location (β = 16.37 [95% CI, 9.01 to 23.74]), test interval (β = 1.18 [95% CI, 1.18-1.41]) and daily device use (β = 1.65 [95% CI, 1.15-2.14]) all were significantly associated with the improvement of word recognition over the first year of device use. In this cohort study of postlingually deafened adult CI users, including both straight and precurved electrode arrays, daily device use and time since CI activation were found to be significantly associated with improved CI-aided speech recognition outcomes. Frequency-to-place mismatch at 1500 Hz and scalar location were associated with word recognition only for precurved arrays. These findings suggest that, for patients with straight arrays, any interference produced by frequency-to-place mismatch may be overcome by adaptation, which could be supported by daily device use. However, for patients with precurved arrays, daily device use may not be sufficient to completely overcome electrode placement factors, including scalar location and mismatch.