Tip Fold-over Research Articles

Characterizing Cochlear Implant Trans-Impedance Matrix Heatmaps in Patients With Abnormal Anatomy.

To characterize transimpedance matrix (TIM) heatmap patterns in patients at risk of labyrinthine abnormality to better understand accuracy and possible TIM limitations. Retrospective review of TIM patterns, preoperative, and postoperative imaging. Tertiary referral center. Patients undergoing cochlear implantation with risk of labyrinthine abnormality. None. Seventy-seven patients were evaluated. Twenty-five percent (n = 19) of patients had a TIM pattern variant identified. These variants were separated into 10 novel categories. Overall, 9% (n = 6) of electrodes were malpositioned on intraoperative x-ray, of which 50% (n = 3) were underinserted, 17% (n = 1) were overinserted, 17% (n = 1) had a tip foldover, and 17% (n = 1) had a coiled electrode. The number of patients with a variant TIM pattern and normal x-ray was 18% (n = 14), and the number of patients with normal TIM pattern and malposition noted on x-ray was 3% (n = 2; both were electrode underinsertions that were recognized due to open circuits and surgical visualization).A newly defined skip heat pattern was identified in patients with IP2/Mondini malformation and interscalar septum width <0.5 mm at the cochlear pars ascendens of the basal turn. This study defines novel patterns for TIM heatmap characterization to facilitate collaborative and comparative research moving forward. In doing so, it highlights a new pattern termed skip heat, which corresponds with a deficient interscalar septum of the cochlea pars ascendens of the basal turn in patients with IP2 malformation. Overall, the data assist the surgeon in better understanding the implications and limitations of TIM patterns within groups of patients with risk of labyrinthine abnormalities.

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

To evaluate the predictive value of intracochlear electrocochleography (ECochG) for identifying tip fold-over during cochlear implantation (CI) using the slim modiolar electrode (SME) array. Prospective cohort study. Tertiary referral center. From July 2022 to June 2023, 142 patients, including adults and children, underwent intracochlear ECochG monitoring during and after SME placement. Tone-bursts were presented from 250 Hz to 2 kHz at 108 to 114 dB HL. A fast Fourier transform (FFT) allowed for frequency-specific evaluation of ECochG response. ECochG patterns during insertion and postinsertion were evaluated using sensitivity and specificity analysis to predict tip fold-over. Intraoperative plain radiographs served as a reference standard. Fifteen tip fold-over cases occurred (10.6%) with significant ECochG response (>2 µV). Sixty-one cases without tip fold-over occurred (43.0%) with significant ECochG response. All tip fold-overs had both a nontonotopic postinsertion sweep and nonrobust active insertion pattern. No patients with robust insertion or tonotopic sweep patterns had tip fold-over. Sensitivity of detecting tip fold-over when having both nonrobust insertion and nontonotopic sweep patterns was 100% (95% confidence inteval [CI]78.2%-100%), specificity was 68.9% (95% CI55.7%-80.1%), and the overall accuracy was 72.0% (95% CI60.5%-81.7%). Intracochlear ECochG monitoring during cochlear implantation with the SME can be a valuable tool for identifying properly positioned electrode arrays. In cases where ECochG patterns are nonrobust on insertion and nontonotopic for electrode sweeps, there may be a concern for tip fold-over, and intraoperative imaging is necessary to confirm proper insertion.

Two Discrete Types of Tip Fold-Over in Cochlear Implantation Using Slim Modiolar Electrodes: Influence of Cochlear Duct Length on Tip Fold-Over.

Precise electrode positioning is crucial for achieving optimal audiological outcomes in cochlear implantation. The slim modiolar electrode (SME), a thin, flexible, and precurved electrode, exhibits favorable modiolar proximity. However, tip fold-over can affect optimal electrode placement. Herein, we share our experiences with tip fold-over in SMEs and present an analysis of conditions that may predispose to tip fold-over. Retrospective medical record review. In total, 475 patients (671 ears) underwent cochlear implantation using SMEs (Nucleus CI532 or CI632 from Cochlear) performed by a single surgeon at a tertiary center between June 14, 2018, and December 1, 2022. Intraoperative x-ray scans (cochlear view), operative records, and cochlear duct length (CDL) were reviewed. Tip fold-over patterns on plain x-ray images (proximal versus distal). Electrode tip fold-over was observed in 18 (2.7%) of the 671 ears with SMEs. This fold-over occurred more frequently in cases with long CDL (>36 mm). Among the 14 cases with available initial x-rays before correction of the tip fold-over, half were classified as proximal and the other half as distal. A predilection for proximal tip fold-over was found in those with a CDL of 36 mm or longer, and longer CDLs were observed for proximal cases than for distal cases. Our pilot data suggest that identifying the type of tip fold-over can aid in correcting it more efficiently. Tip fold-over of SME does not occur uniformly and is more common in ears with long CDL. This tendency is particularly pronounced for the proximal type of tip fold-over. Therefore, preoperative measurement of the CDL and meticulous examination of intraoperative imaging are essential for customized correction.

Detection of Tip Fold-Over of the Slim Modiolar Electrode Using Intraoperative Mobile Cone-Beam Computed Tomography.

This study aimed to evaluate the importance of mobile cone-beam computed tomography in detecting tip fold-over of a slim modiolar electrode within the cochlea during surgery. Retrospective case review. Tertiary medical center. From January 2020 to June 2022, 33 ears of 30 patients with normal cochlear morphology underwent cochlear implantation with slim modiolar electrodes and intraoperative mobile cone-beam computed tomography imaging. Furthermore, we retrospectively reviewed the medical records and images. The tip fold-over of the electrodes was detected using mobile cone-beam computed tomography in 3 out of 33 ears (9.1%). We could not identify the tip fold-over by scouting plain X-ray images in 2 out of 3 cases before taking the cone-beam computed tomography images. Electrode removal and reinsertion were performed before wound closure and the successful reinsertion was confirmed by mobile cone-beam computed tomography. The folded electrode tips were located at 238.8°, 152°, and 185.8°. Intraoperative mobile cone-beam computed tomography is useful in detecting the tip fold-over of the slim modiolar electrodes during surgery. Therefore, it was possible to reinsert the electrodes in all cases before closing the wound, eliminating the need for revision surgeries. Moreover, the analysis of mobile cone-beam computed tomography images may help to elucidate the mechanisms of electrode tip fold-over.

Cochlear implant electrode array tip-foldover detection by electrode voltage telemetry

Objectives With the introduction of more flexible and thinner electrodes, such as Cochlear’s Slim Modiolar Electrode, there is a higher risk of electrode insertion problems, in particular the tip foldover. Timely intraoperative detection of the problem would allow for direct intraoperative correction. This paper describes a non-radiological method for intraoperative tip foldover detection that is applicable in all surgical centers and can quickly deliver accurate results. Methods Postoperative radiographs of 118 CI-recipients implanted with Nucleus devices were retrospectively analyzed on the presence of a tip foldover. Electrode Voltage Telemetry (EVT), also called Electric Field Imaging, was performed by means of Cochlear’s EVT software tool, which is now integrated into Custom Sound–EP as the Trans-Impedance-Matrix measurement option. Tip foldover detection was automated by using the linear Hough transform for extracting straight-line patterns in the Trans-Impedance Matrix’s heatmap. Results The six cases of electrode tip foldover were accurately identified by the EVT measurements, including two cases with folding location very close to the electrode tip (contact 20). Conclusion Electrode Voltage Telemetry measures the Trans-Impedance Matrix, which can accurately detect tip foldovers of the cochlear implant electrodes within 1 min. This method can be reliably applied in all patients with normal cochlear anatomy and is able to intraoperatively detect foldovers localized even very close to the electrode tip. Application of the linear Hough transform allows for automatic detection of electrode tip foldovers that shows excellent agreement with visual evaluation of the radiological images and the transimpedance matrix’s heatmap.

Predictive Value of Transimpedance Matrix Measurements to Detect Electrode Tip Foldover.

To evaluate the ability of the transimpedance matrix (TIM) measurement to detect cochlear implant electrode tip foldover by comparing results to a "gold standard," the intraoperative plain film radiograph. Retrospective case series. Tertiary referral hospital. One hundred three patients who underwent cochlear implantation between June 2020 and August 2021. Intraoperative electrophysiologic monitoring (electrode impedances, neural response telemetry, and TIM measurement) and modified Stenver's view plain film radiographs. Identification of tip foldover on both TIM and plain films. In total, 103 patients (117 ears) had both a TIM measurement and intraoperative X-ray available for review, including 68 adults and 35 children. One hundred patients (85%) received the Cochlear Slim Modiolar electrode. Tip foldovers were noted in three of 117 implants (2.5%). In all cases, TIM was able to detect the foldover, and the electrode arrays were reinserted with the patients still under anesthesia, with repeat X-ray demonstrating a normal configuration. Two other abnormal TIM patterns were identified. One was in a patient with an obstructed cochlea in whom only 10 electrodes could be inserted, the other was in a patient with a common cavity abnormality. One additional patient underwent electrode repositioning intraoperatively because of overinsertion. In this patient, the TIM appeared to be within normal limits, but the over-insertion was apparent on X-ray. Overall, the sensitivity and specificity of TIM measurements in detecting electrode tip foldover were both 100%. TIM measurements were able to accurately identify tip foldovers. More research is needed to define the adjunctive role of TIM as an intraoperative measure.

Evaluation of a Transimpedance Matrix Algorithm to Detect Anomalous Cochlear Implant Electrode Position

Introduction: Transimpedance measurements from cochlear implant electrodes have the potential to identify anomalous electrode array placement, such as tip fold-over (TFO) or fold-back, basal electrode kinking, or buckling. Analysing transimpedance may thus replace intraoperative or post-operative radiological imaging to detect any potential misplacements. A transimpedance algorithm was previously developed to detect deviations from a normal electrode position with the aim of intraoperatively detecting TFO. The algorithm had been calibrated on 35 forced, tip folded electrode arrays in six temporal bones to determine the threshold criterion required to achieve a sensitivity of 100%. Our primary objective here was to estimate the specificity of this TFO algorithm in patients, in a prospective study, for a series of electrode arrays shown to be normally inserted by post-operative imaging. Methods: Intracochlear voltages were intraoperatively recorded for 157 ears, using Cochlear’s Custom Sound™ EP 5 electrophysiological software (Cochlear Ltd., Sydney, NSW, Australia), for both Nucleus® CI512 and CI532 electrode arrays. The algorithm analysed the recorded 22 × 22 transimpedance matrix (TIM) and results were displayed as a heatmap intraoperatively, only visible to the technician in the operating theatre. After all clinical data were collected, the algorithm was evaluated on the bench. The algorithm measures the transimpedance gradients and corresponding phase angles (θ) throughout the TIM and calculates the gradient phase range. If this was greater than the predetermined threshold, the algorithm classified the electrode array insertion as having a TFO. Results: Five ears had no intraoperative TIM and four anomalous matrices were identified from heatmaps and removed from the specificity analysis. Using the 148 remaining data sets (n = 103 CI532 and n = 45 CI512), the algorithm had an average specificity of 98.6% (95.80%–99.75%). Conclusion: The algorithm was found to be an effective screening tool for the identification of TFOs. Its specificity was within acceptable levels and resulted in a positive predictive value of 76%, with an estimated incidence of fold-over of 4% in perimodiolar arrays. This would mean 3 out of 4 cases flagged as a fold-over would be correctly identified by the algorithm, with the other being a false positive. The measurements were applied easily in theatre allowing it to be used as a routine clinical tool for confirming correct electrode placement.

Evaluating cochlear insertion trauma and hearing preservation after cochlear implantation (CIPRES): a study protocol for a randomized single-blind controlled trial

BackgroundIn order to preserve residual hearing in patients with sensorineural hearing loss (SNHL) who receive a cochlear implant (CI), insertion trauma to the delicate structures of the cochlea needs to be minimized. The surgical approach comprises the conventional mastoidectomy-posterior tympanotomy (MPT) to arrive at the middle ear, followed by either a cochleostomy (CO) or the round window (RW) approach. Both techniques have their benefits and disadvantages. Another important aspect in structure preservation is the design of the electrode array. Two different designs are used: a “straight” lateral wall lying electrode array (LW) or a “pre-curved” perimodiolar lying electrode array (PM). Interestingly, until now, the best surgical approach and design of the implant is uncertain. Our hypothesis is that there is a difference in hearing preservation outcomes between the four possible treatment options.MethodsWe designed a monocenter, multi-arm, randomized controlled trial to compare insertion trauma between four groups of patients, with each group having a unique combination of an electrode array type (LW or PM) and surgical approach (RW or CO). In total, 48 patients will be randomized into one of these four intervention groups. Our primary objective is the comparison of postoperative hearing preservation between these four groups. Secondly, we aim to assess structure preservation (i.e., scalar translocation, with basilar membrane disruption or tip fold-over of array) for each group. Thirdly, we will compare objective outcomes of hearing and structure preservation by way of electrocochleography (ECochG).DiscussionCochlear implantation by way of a cochleostomy or round window approach, using different electrode array types, is the standard medical care for patients with severe to profound bilateral sensorineural hearing loss, as it is a relatively simple and low-risk procedure that greatly benefits patients. However, loss of residual hearing remains a problem. This trial is the first randomized controlled trial that evaluates the effect of cochlear insertion trauma of several CI treatment options on hearing preservation.Trial registrationNetherlands Trial Register (NTR) NL8586. Registered on 4 May 2020. Retrospectively registered; 3/48 participants were included before registration.

Comparison Between Transimpedance Matrix (TIM) Measurement and X-ray Fluoroscopy for Intraoperative Electrode Array Tip Fold-Over Detection.

The aim of this study was to compare Transimpedance Matrix (TIM-) measurement and X-ray fluoroscopy for the intraoperative detection of electrode array tip fold-over in cochlear implant recipients. Retrospective agreement study. Tertiary referral hospital. Forty-two patients (47 ears) consecutively implanted with the Slim Modiolar Electrode. Five raters, with different levels of clinical experience, individually retrospectively evaluated the TIM-heatmaps and X-ray fluoroscopy images of all patients included in this study for electrode array tip fold-over. Agreement between raters' individual evaluation and the diagnosis given during clinical intraoperative evaluation for both modalities, as well as the inter-method agreement between TIM-measurement and fluoroscopy, and the inter-rater agreement for both modalities. A tip fold-over was found in three of the forty-seven implantations (6.4%) included in this study. The average agreement between raters' evaluation and the intraoperative evaluation was 88% (Cohens κ = 0.378) for fluoroscopy and 99% (Cohens κ = 0.915) for TIM-measurement. Two raters misdiagnosed at least one tip fold-over as being correctly positioned when evaluating the fluoroscopy images (1/3 and 3/3, respectively). Each of the raters correctly detected all three tip fold-overs using the TIM-heatmaps. The inter-rater agreement for fluoroscopy was classified as "fair" (Fleiss' κ = 0.286), while the inter-rater agreement for TIM-measurement was classified as "near-perfect" (Fleiss' κ = 0.850). TIM-measurement has a high potential to replace X-ray fluoroscopy for intraoperatively detecting electrode array tip fold-over in cochlear implantation, especially in patients implanted with flexible, precurved arrays.

Detection of “tip fold-over” of the cochlear implant electrode array with transimpedance matrix (TIM) measurement

In recent years, the cochlear implant has become a routine and effective treatment tool for severe hearing loss and total deafness. One of the commonly used and effective innovations of our time in cochlear implantation is the perimodiolar thin electrode array. The atraumatic electrode array, which closely embraces the central axis of the cochlea (modiolus), has served its popularity with very convincing results, with its performance in both electrophysiological measurements and acoustic hearing preservation. However, very few publications describe the frequency of improper positioning of the electrode array, which is known as 'tip fold-over'. The aim of our study is to incorporate a software technique, the transimpedance matrix (TIM), into routine intraoperative electrophysiological measurement methodologies to provide a potential objective diagnostic opportunity for early detection of tip fold-over of the electrode array. Following bilateral cochlear implantation of a three-year-old child, postoperative radiography showed the correct position of the electrode array on the left side, while tip fold-over of the intracochlear electrode array was detected on the right side. Following imaging, a TIM study was performed as an electrophysiological method. During the procedure, the measuring device transmits a voltage of the order of 1 V to the nearby structures of the cochlea at a constant current at the designated stimulus electrodes. Measuring electrodes were used to register the voltage measured on the tissues, and then converted into a TIM. Electrode tip fold-over was previously diagnosed by radiological examination, while it can also be diagnosed by objective electrophysiological measurements now, and these two tests correlate well. Standard radiological imaging techniques for electrode positioning can be supplemented or replaced by easy-to-perform, effective objective electrophysiological studies. Tip fold-over can be detected intraoperatively, even before wound closure, if the electrode array is in the wrong position, thus reducing the radiation exposure associated with radiological examinations as well as reducing relevant costs. Orv Hetil. 2021; 162(25): 988-996.

A new method to determine the optimal orientation of Slim Modiolar cochlear implant electrode array insertion.

Our goal was to determine the optimal orientation of insertion of the Slim Modiolar electrode and develop an easy-to-use method to aid implantation surgery. In some instances, the electrode arrays cannot be inserted in their full length. This can lead to buckling, interscalar dislocation or tip fold-over. In our opinion, one of the possible reasons of tip fold-over is unfavourable orientation of the electrode array. Our goal was to determine the optimal orientation of the Slim Modiolar electrode array relative to clear surgical landmarks and present our method in one specified case. For the measurement, we used the preoperative CT scan of one of our cochlear implant patients. These images were processed by an open source and free image visualization software: 3D Slicer. In the first step we marked the tip of the incus short process and then created the cochlear view. On this view we drew two straight lines: the first line represented the insertion guide of the cochlear implant and the second line was the orientation marker (winglet). We determined the angle enclosed by winglet and the line between the tip of the incus short process and the cross-section of previously created two lines. For the calculation we used a self-made python code. The result of our algorithm for the angle was 46.6055°. To validate this result, we segmented, from the CT scan, the auditory ossicles and the membranaceous labyrinth. From this segmentation we generated a 3D reconstruction. On the 3D view, we can see the position of the previous lines relative to the anatomical structures. After this we rotated the 3D model together with the lines so that the insertion guide forms a dot. In this view, the angle was measured with ImageJ and the result was 46.599°. We found that our method is easy, fast, and time-efficient. The surgery can be planned individually for each patient, based on their routine preoperative CT scan of the temporal bone, and the implantation procedure can be made safer. In the future we plan to use this method for all cochlear implantation surgeries, where the Slim Modiolar electrode is used.

Electrocochleography Observations in a Series of Cochlear Implant Electrode Tip Fold-Overs.

Tip fold-over is a rare but serious complication of cochlear implant (CI) surgery. The purpose of this study was to present intraoperative electrocochleography (ECochG) observations in a series of CI electrode tip fold-overs. Five pediatric subjects undergoing CI surgery through a round window (RW) approach with a perimodiolar electrode array, who were diagnosed with either auditory neuropathy spectrum disorder or enlarged vestibular aqueduct. Intraoperative RW ECochG during CI surgery: tone burst stimuli were presented from 95 to 110 dB SPL. Magnitude and phase characteristics of ECochG responses obtained intraoperatively before and immediately after electrode insertion were examined for patients with and without tip fold-over. Three subjects presented with tip fold-over and two formed the control group. Among fold-over cases, one participant exhibited an inversion in the starting phase of the cochlear microphonic response and a decrease in spectral magnitude from pre- to postinsertion. Both subjects who did not exhibit a change in phase had an increase in the ECochG-total response (ECochG-TR) magnitude. No case in the control group exhibited a change in starting phase. In regard to the ECochG-TR, all controls showed a decrease in the magnitude. Despite the small number of patients, heterogeneous ECochG response patterns were observed within the fold-over group. Though these results are not conclusive, they can serve as a framework to begin to understand ECochG's utility in detecting intraoperative tip fold-over.

Transimpedance Matrix (TIM) Measurement for the Detection of Intraoperative Electrode Tip Foldover Using the Slim Modiolar Electrode: A Proof of Concept Study.

The aim of this study is to report on our preliminary experience with Transimpedance Matrix (TIM)-measurement for the detection of cochlear implant electrode tip foldovers compared with intraoperative imaging in patients implanted with the slim modiolar electrode (SME). Proof of concept study. Tertiary university referral center. Twenty five ears (in 22 patients) implanted consecutively with the SME. Following cochlear implantation, intraoperative TIM-measurement and fluoroscopy were performed. One week postoperatively, the electrode position was evaluated using Computed Tomography (CT)-imaging. Electrode array tip foldover. Electrode array tip foldover occurred in three of the 25 cochlear implantations performed (12%). In each case, the foldover was detected by both TIM and fluoroscopy, leading to reposition and correct intracochlear placement of the array. TIM-measurement is a promising method for the intraoperative detection of an electrode array tip foldover. The TIM-tool with intuitive heatmap display is easy to use, fast, and readily available to clinics using TIM-software in the operating theatre.

Intraoperatives Tip-Foldover-Screening mittels Spread of Excitation Messungen

BackgroundIn rare cases, a cochlear implantation can lead to a so-called tip fold-over during insertion of the electrode array. In order to detect or exclude such a misalignment a radiological check of the cochlear implant (CI) electrode array is carried out intra- or often post-operatively (gold standard), thereby exposing the patient to additional radiation. Alternatively, successful electrode insertion can be verified by measuring the spread of excitation (SOE). However, interpretation of the test results requires considerable expertise, and standardized measurement protocols and reference values are also essential. Therefore, the aim of the study is to evaluate an automated screening procedure in order to obtain a reliable statement about the normal tonotopic position of the implanted CI electrode array intraoperatively and with as little effort as possible. MethodsFor CI surgery with Cochlear™ Nucleus® implants, an intraoperative tip-fold-over (TFO) screening was performed in a bi-centric study in over 100 adult patients: Firstly, threshold measurements for electrically evoked compound action potential (ECAP) using AutoNRT™ were recorded. Subsequently, SOE measurements were carried out on electrodes 13 and 22. The automated evaluation of the SOE data sets then made it possible to make a dichotomous decision about a normal or abnormal test result. The position of the electrode array was checked intra- or post-operatively using conventional transorbital X-ray (reference method). ResultsThe intraoperative TFO screening procedure is applicable in around 80% of cases. The accuracy of the screening for measurements via the active stimulation electrodes 13 / 22 is 63.9% / 95.4%. The classification error is 36.1% / 4.6% and the phi coefficient is 0.27 / 0.69. All radiologically proven tip-fold-overs were reliably identified with the intraoperative screening (sensitivity = 100%). A higher specificity (>95%) can be achieved only with measurements via electrode 22. ConclusionsThe TFO Screening via measurement at electrode 22 can successfully distinguish between a correct and incorrect position of the electrode array due to a tip-fold-over, and the remaining cases would require further imaging.

Cost-Effectiveness of Intraoperative CT Scanning in Cochlear Implantation in Fee-for-Service and Bundled Payment Models.

Electrode array tip fold-over is a complication of cochlear implant surgery that results in poor hearing outcomes and often leads to revision surgery. However, tip fold-over can be corrected immediately if identified through intraoperative computed tomography, which also potentially provides information about final intracochlear positioning. Our objective was to provide the first economic analysis of intraoperative computed tomography by generating models in fee-for-service and bundled payment reimbursement structures of payer and institutional cost-effectiveness of this technology used in cochlear implantation over 1, 5, and 10-year time periods. Cost data specific to a commerically available intraoperative computed tomography machine was obtained from the manufacturer, Xoran Technologies. Institutional tip fold-over rate was obtained from already published data. Medicare reimbursement rate for cochlear implantation was obtained from institutional accountants. Private payer reimbursement for and cost of revision cochlear implantation were estimated based on available data. At large volume centers, cost-effectiveness of this technology is possible in both fee-for-service and bundled payment reimbursement structures at various time points dependent on payer mix. Even low volume cochlear implantation centers (<150 per year) can financially benefit from intraoperative computed tomography in bundled payment models at 5- and 10-year periods regardless of payer mix. This model demonstrates key factors at play in determining cost-effectiveness of this technology including institutional factors and payer type and suggests this technology can align incentives both to improve patient care and outcomes with institutional and payer financial well-being.

Potential insertion complications with cochlear implant electrodes

Objectives: The aim of this discussion paper and literature review was to estimate the incidence of a variety of complications associated with the surgical placement of cochlear implant (CI) electrode arrays and to discuss the implications and management of sub-optimal electrode placement. Results: A review of the peer-reviewed literature suggests that the incidence of incomplete electrode insertion and kinking is more prevalent in straight arrays and not more than about 2% in CI recipients with normal cochlear anatomy/patency. Incidence of tip fold-over is greater with perimodiolar arrays but also occurs with straight arrays and is typically less than 5%. Conversely, electrode migration is more common with straight arrays, and high rates (up to 46%) have been reported in some studies. Scalar translocations have also been reported for both perimodiolar and straight arrays. Higher rates have been reported for stylet-based perimodiolar electrodes inserted via cochleostomy (up to 56%), but with much lower rates (<10%) with both sheath-based perimodiolar arrays and lateral wall arrays. Electrode positioning complications represent a significant proportion of perioperative CI complications and compromise the level of benefit from the device. Careful surgical planning and appropriate pre- and intraoperative imaging can reduce the likelihood and impact of electrode positioning complications. There is also evidence that newer array designs are less prone to certain complications, particularly scalar translocation. Conclusions: It is important that implanting surgeons are aware of the impact of sub-optimal electrode placement and the steps that can be taken to avoid, identify and manage such complications.

Use of intraoperative CT scanning for quality control assessment of cochlear implant electrode array placement*

Background: Imaging of cochlear implant (CI) electrode arrays (EAs) consists of intraoperative fluoroscopy to rule out tip fold-over and/or post-operative computerized tomography (CT) if concern exists regarding extrusion or misplacement of the EA. Intraoperative CT (iCT) can satisfy these current needs and enables specification of final intracochlear position.Aims/objectives: To describe iCT scanning of CI recipients at an academic medical center.Materials and methods: iCT was used to scan CI recipients within the operating room before recovering from general anesthesia.Results: In fiscal year 2019, 301 CI were placed (83 children, 218 adult). One hundred, seventy-five iCTs were performed (58% of total CIs) of which 52 were children (63% of pediatric CIs) and 123 were adult (57% of adult CIs). Of 7 CI surgeons, use of iCT ranged from 14% to 100% (mean 60%). Four tip fold-overs were identified and corrected intraoperatively. Surgeons reported using the images to improve technique (i.e. pulling back precurved EAs to improve perimodiolar positioning).Conclusion and significance: The current standard of care for CI is to insert EAs without feedback as to final location. iCT provides surgeons with rapid post-insertion feedback which allows detection and correction of suboptimally placed EAs as well as refinement of surgical technique.

Electrophysiological detection of electrode fold-over in perimodiolar cochlear implant electrode arrays: a multi-center study case series.

It is important for the surgeon to determine the position of the CI electrode array during and after its placement within the cochlea. Most preferably, this should be within the scala tympani to obtain the best audiological outcome. Thus, misplacement into the scala vestibuli or tip fold-over should be prevented. Since there are different ways to ensure proper positioning of the electrode array within the scala tympani (e.g., intraoperative radiography, electrophysiological recordings), our study was aimed at detecting intraoperative electrophysiologic characteristics to better understand the mechanisms of those electrode tip fold-overs. In a multi-centric, retrospective case-control series, patients with a postoperatively by radiography detected tip fold-over in perimodiolar electrodes were included. The point of fold-over (i.e., the electrode position) was determined and the intraoperative Auto-NRT recordings were analysed and evaluated. Four patients were found to have an electrode tip fold-over (out of 85 implantees). Significant changes of the Auto-NRT recordings were not detected. All tip fold-overs occurred in the most apical part of the electrodes. Cochlear implantation for hearing impaired patients plays a decisive role in modern auditory rehabilitation. Perimodiolar electrode arrays may fold over during the insertion and, hence, could have a negative impact on audiological outcome. Characteristic electrophysiologic changes to possibly predict this were not found in our series.

Incidence for Tip Foldover During Cochlear Implantation.

Incidence and clinical presentation of tip foldover during cochlear implantation (CI). Retrospective case review. Tertiary referral university hospital. One thousand three hundred twenty CI recipients who underwent postoperative Stenvers view, digital computed tomography (CT), or digital volume tomography (DVT). Tip foldover rates were evaluated with regard to perimodiolar (PM), lateral wall (LW), and mid-scalar (MS) electrode carriers; the electrode insertion angle was estimated and postoperative complications and the necessity for revisions were described. One thousand three hundred twenty CI recipients (1,722 ears) had detailed surgery reports and postoperative imaging available for review. Tip foldover occurred in 15 ears (0.87%) with the highest rate (1.67%) for PM electrodes. In three patients tip foldover was accompanied by costimulation of the facial nerve and one patient reported vertigo. Eleven patients underwent revision surgery. In two of them revision was performed in the same surgical intervention due to abnormality in spread of excitation measurement. In four patients no revision was conducted due to uncompromised aided speech perception. In a large academic center with experienced surgeons, tip foldover verified by CT/DVT arose at a rate of 0.87%. PM electrode carriers inherited the highest risk for this electrode malposition. Revision surgery was feasible in these cases.

Precurved Cochlear Implants and Tip Foldover: A Cadaveric Imaging Study.

Objective This study aims to define a reliable protocol for radiographic identification of placement and tip foldover of newly designed precurved and straight electrodes. Study Design Prospective imaging study. Setting Academic institution. Methods Three models of cochlear implants (Cochlear, MED-EL, and Advanced Bionics) were inserted into fresh cadaveric specimens (n = 2) in 3 configurations (normal positioning in the scala tympani, intracochlear tip foldover, and placement into the vestibular system) for a total of 9 implant scenarios. Specimens were imaged with plain radiography in Stenvers projection, as well as by high-resolution computed tomography. Results Electrode placement and presence or absence of electrode tip foldover were easily identified in all 9 scenarios on plain radiography based on the described technique. Each was confirmed with high-resolution computed tomography. Plain film temporal bone images of new electrode designs with proper and improper placement are provided for reference. Conclusion A defined protocol for intraoperative plain film radiography allowed for reliable imaging of 3 newly designed cochlear implant electrodes and immediate identification of extracochlear placement and tip foldover. Findings may be used for intraoperative confirmation of electrode array placement.