Evaluation of the Relationship between the NRT-Ratio, Cochlear Anatomy, and Insertions Depth of Perimodiolar Cochlear Implant Electrodes

The position of the cochlear implant electrode array within the scala tympani is essential for an optimal postoperative hearing benefit. If the electrode array changes in between the scalae intracochlearly (i.e., from scala tympani to scala vestibuli), a reduced auditory performance can be assumed. We established a neural response telemetry-ratio (NRT-ratio) which corresponds with the scalar position of the electrodes but shows within its limits a variability. The aim of this study was to determine if insertion depth angle or cochlea size influences the NRT-ratio. The intraoperative electrophysiological NRT data of 26 patients were evaluated. Using a flat panel tomography system, the position of the electrode array was evaluated radiologically. The insertion depth angle of the electrode, the cochlea size, and the NRT-ratio were calculated postoperatively. The radiological results were compared with the intraoperatively obtained electrophysiological data (NRT-ratio) and statistically evaluated. In all patients the NRT-ratio, the insertion depth angle, and the cochlea size could be determined. A significant correlation between insertional depth, cochlear size, and the NRT-ratio was not found. The NRT-ratio is a reliable electrophysiological tool to determine the scalar position of a perimodiolar electrode array. The NRT-ratio can be applied independent from insertion depth and cochlear size.

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Radiological and NRT-Ratio–Based Estimation of Slim Straight Cochlear Implant Electrode Positions

Annals of Otology Rhinology & Laryngology ◽

10.1177/0003489416675355 ◽

2016 ◽

Vol 126 (1) ◽

pp. 73-78 ◽

Cited By ~ 7

Author(s):

Philipp Mittmann ◽

Ingo Todt ◽

Arneborg Ernst ◽

Grit Rademacher ◽

Sven Mutze ◽

...

Keyword(s):

Electrode Array ◽

Controlled Study ◽

Data Sets ◽

Scala Tympani ◽

Tertiary Referral ◽

Flat Panel ◽

Tomography System ◽

Neural Response Telemetry ◽

Intracochlear Electrode Array ◽

Array Position

Objectives: An intraoperative neural response telemetry-ratio (NRT-ratio) was established, which can provide information about the intraoperative intracochlear electrode array position for perimodiolar electrodes. Methods: In a retrospective controlled study in 2 tertiary referral centers, the electrophysiological data sets of 50 patients with measured intraoperative auto-NRTs and postoperative radiological examinations were evaluated. All patients were implanted with Nucleus slim straight electrodes. The NRT-ratio was calculated by dividing the average auto-NRT data from electrodes 16 to 18 with the average from electrodes 5 to 7. Using a flat panel tomography system or a computed tomography, the position of the electrode array was certified radiological. Results: Radiologically, 2 out of 50 patients were identified with an electrode translocated from the scala tympani into the scala vestibuli. The radiologically estimated electrodes indicating a scalar change showed a regular NRT-ratio but nonspecific NRT-level changes at the localization of translocation.

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Clinical investigation of the Nucleus Slim Modiolar Electrode

Audiology and Neurotology ◽

10.1159/000480345 ◽

2017 ◽

Vol 22 (3) ◽

pp. 169-179 ◽

Cited By ~ 29

Author(s):

Antje Aschendorff ◽

Robert Briggs ◽

Goetz Brademann ◽

Silke Helbig ◽

Joachim Hornung ◽

...

Keyword(s):

Computed Tomography ◽

Cochlear Implant ◽

Temporal Bone ◽

Clinical Investigation ◽

Round Window ◽

Electrode Array ◽

Lateral Wall ◽

Scala Tympani ◽

Flat Panel ◽

Insertion Depth

Aims: The Nucleus CI532 cochlear implant incorporates a new precurved electrode array, i.e., the Slim Modiolar electrode (SME), which is designed to bring electrode contacts close to the medial wall of the cochlea while avoiding trauma due to scalar dislocation or contact with the lateral wall during insertion. The primary aim of this prospective study was to determine the final position of the electrode array in clinical cases as evaluated using flat-panel volume computed tomography. Methods: Forty-five adult candidates for unilateral cochlear implantation were recruited from 8 centers. Eleven surgeons attended a temporal bone workshop and received further training with a transparent plastic cochlear model just prior to the first surgery. Feedback on the surgical approach and use of the SME was collected via a questionnaire for each case. Computed tomography of the temporal bone was performed postoperatively using flat-panel digital volume tomography or cone beam systems. The primary measure was the final scalar position of the SME (completely in scala tympani or not). Secondly, medial-lateral position and insertion depth were evaluated. Results: Forty-four subjects received a CI532. The SME was located completely in scala tympani for all subjects. Pure round window (44% of the cases), extended round window (22%), and inferior and/or anterior cochleostomy (34%) approaches were successful across surgeons and cases. The SME was generally positioned close to the modiolus. Overinsertion of the array past the first marker tended to push the basal contacts towards the lateral wall and served only to increase the insertion depth of the first electrode contact without increasing the insertion depth of the most apical electrode. Complications were limited to tip fold-overs encountered in 2 subjects; both were attributed to surgical error, with both reimplanted successfully. Conclusions: The new Nucleus CI532 cochlear implant with SME achieved the design goal of producing little or no trauma as indicated by consistent scala tympani placement. Surgeons should be carefully trained to use the new deployment method such that tip fold-overs and over insertion may be avoided.

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Effect of Scala Tympani Height on Insertion Depth of Straight Cochlear Implant Electrodes

Otolaryngology ◽

10.1177/0194599820904941 ◽

2020 ◽

Vol 162 (5) ◽

pp. 718-724 ◽

Cited By ~ 1

Author(s):

William G. Morrel ◽

Jourdan T. Holder ◽

Benoit M. Dawant ◽

Jack H. Noble ◽

Robert F. Labadie

Keyword(s):

Cochlear Implant ◽

Retrospective Review ◽

Basilar Membrane ◽

Lateral Wall ◽

Scala Tympani ◽

Tertiary Referral ◽

Insertion Depth ◽

Tertiary Referral Center ◽

Relationship Of ◽

The Relationship

Objective Studies suggest lateral wall (LW) scala tympani (ST) height decreases apically, which may limit insertion depth. No studies have investigated the relationship of LW ST height with translocation rate or location. Study Design Retrospective review. Setting Cochlear implant program at tertiary referral center. Subjects and Methods LW ST height was measured in preoperative images for patients with straight electrodes. Scalar location, angle of insertion depth (AID), and translocation depth were measured in postoperative images. Audiologic outcomes were tracked. Results In total, 177 ears were identified with 39 translocations (22%). Median AID was 443° (interquartile range [IQR], 367°-550°). Audiologic outcomes (126 ears) showed a small, significant correlation between consonant-nucleus-consonant (CNC) word score and AID ( r = 0.20, P = .027), although correlation was insignificant if translocation occurred ( r = 0.11, P = .553). Translocation did not affect CNC score ( P = .335). AID was higher for translocated electrodes (503° vs 445°, P = .004). Median translocation depth was 381° (IQR, 222°-399°). Median depth at which a 0.5-mm electrode would not fit within 0.1 mm of LW was 585° (IQR, 405°-585°). Median depth at which a 0.5-mm electrode would displace the basilar membrane by ≥0.1 mm was 585° (IQR, 518°-765°); this was defined as predicted translocation depth (PTD). Translocation rate was 39% for insertions deeper than PTD and 14% for insertions shallower than PTD ( P = .008). Conclusion AID and CNC are directly correlated for straight electrodes when not translocated. Translocations generally occur around 380° and are more common with deeper insertions due to decreasing LW ST height. Risk of translocation increases significantly after 580°.

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Flat-Panel Volume Computed Tomography for Cochlear Implant Electrode Array Examination in Isolated Temporal Bone Specimens

Otology & Neurotology ◽

10.1097/00129492-200606000-00010 ◽

2006 ◽

Vol 27 (4) ◽

pp. 491-498 ◽

Cited By ~ 21

Author(s):

Soenke H. Bartling ◽

Rajiv Gupta ◽

Attila Torkos ◽

Christian Dullin ◽

Grabbe Eckhardt ◽

...

Keyword(s):

Computed Tomography ◽

Cochlear Implant ◽

Temporal Bone ◽

Electrode Array ◽

Flat Panel ◽

Volume Computed Tomography

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Computed-tomography estimates of interaural mismatch in insertion depth and scalar location in bilateral cochlear-implant users

10.1101/2021.02.26.21252533 ◽

2021 ◽

Author(s):

Matthew J Goupell ◽

Jack H Noble ◽

Sandeep A Phatak ◽

Elizabeth Kolberg ◽

Miranda Cleary ◽

...

Keyword(s):

Computed Tomography ◽

Cochlear Implant ◽

Surgical Techniques ◽

Superior Olivary Complex ◽

Negative Consequences ◽

Scala Tympani ◽

Insertion Depth ◽

Binaural Processing ◽

Bilateral Cochlear Implant ◽

Interaural Differences

Hypothesis: We hypothesized that the bilateral cochlear-implant (BI-CI) users would have a range of interaural insertion-depth mismatch because of different physical placements or characteristics of the arrays, but less than half of electrodes would have less than 75° or 3 mm of interaural insertion-depth mismatch. We also hypothesized that interaural insertion-depth mismatch would be more prevalent nearer the apex, when electrodes were located outside of scala tympani (i.e., possible interaural scalar mismatch), and when the arrays were a mix of pre-curved and straight types. Background: Brainstem neurons in the superior olivary complex are exquisitely sensitive to interaural differences, the cues to sound localization. These binaurally sensitive neurons rely on interaurally place-of-stimulation-matched inputs at the periphery. BI-CI users may have interaural differences in insertion depth and scalar location, causing interaural place-of-stimulation mismatch that impairs binaural abilities. Methods: Insertion depths and scalar locations were calculated from temporal-bone computed-tomography (CT) scans of 107 BI-CI users (27 Advanced Bionics, 62 Cochlear, and 18 Med-El). Each subject had either both pre-curved, both straight, or one of each type of array (mixed). Results: The median interaural insertion-depth mismatch was 23.4° or 1.3 mm. Relatively large interaural insertion-depth mismatch sufficient to disrupt binaural processing occurred for about 15% of electrode pairs [defined as >75° (13.0% of electrode pairs) or >3 mm (19.0% of electrode pairs)]. There was a significant three-way interaction of insertion depth, scalar location, and array type. Interaural insertion-depth mismatch was most prevalent when electrode pairs were more apically located, electrode pairs had interaural scalar mismatch (i.e., one in Scala Tympani, one in Scala Vestibuli), and when the arrays were both pre-curved. Conclusion: Large interaural insertion-depth mismatch can occur in BI-CI users. For new BI-CI users, improved surgical techniques to avoid interaural insertion-depth and scalar mismatch is recommended. For existing BI-CI users with interaural insertion-depth mismatch, interaural alignment of clinical frequency allocation tables by an audiologist might remediate any negative consequences to spatial-hearing abilities.

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Robot-Assisted Electrode Array Insertion Becomes Available in Pediatric Cochlear Implant Recipients: First Report and an Intra-Individual Study

Frontiers in Surgery ◽

10.3389/fsurg.2021.695728 ◽

2021 ◽

Vol 8 ◽

Author(s):

Huan Jia ◽

Jinxi Pan ◽

Wenxi Gu ◽

Haoyue Tan ◽

Ying Chen ◽

...

Keyword(s):

Cochlear Implantation ◽

Electrode Array ◽

Pure Tone Audiometry ◽

Lateral Wall ◽

Robot Assisted ◽

Insertion Depth ◽

Safety And Reliability ◽

Radiological Measurements ◽

Auditory Performance ◽

Temporal Bones

Background: As an advanced surgical technique to reduce trauma to the inner ear, robot-assisted electrode array (EA) insertion has been applied in adult cochlear implantation (CI) and was approved as a safe surgical procedure that could result in better outcomes. As the mastoid and temporal bones are generally smaller in children, which would increase the difficulty for robot-assisted manipulation, the clinical application of these systems for CI in children has not been reported. Given that the pediatric candidate is the main population, we aim to investigate the safety and reliability of robot-assisted techniques in pediatric cochlear implantation.Methods: Retrospective cohort study at a referral center in Shanghai including all patients of simultaneous bilateral CI with robotic assistance on one side (RobOtol® system, Collin ORL, Bagneux, France), and manual insertion on the other (same brand of EA and CI in both side), from December 2019 to June 2020. The surgical outcomes, radiological measurements (EA positioning, EA insertion depth, mastoidectomy size), and audiological outcomes (Behavior pure-tone audiometry) were evaluated.Results: Five infants (17.8 ± 13.5 months, ranging from 10 to 42 months) and an adult (39 years old) were enrolled in this study. Both perimodiolar and lateral wall EAs were included. The robot-assisted EA insertion was successfully performed in all cases, although the surgical zone in infants was about half the size in adults, and no difference was observed in mastoidectomy size between robot-assisted and manual insertion sides (p = 0.219). The insertion depths of EA with two techniques were similar (P = 0.583). The robot-assisted technique showed no scalar deviation, but scalar deviation occurred for one manually inserted pre-curved EA (16%). Early auditory performance was similar to both techniques.Conclusion: Robot-assisted technique for EA insertion is approved to be used safely and reliably in children, which is possible and potential for better scalar positioning and might improve long-term auditory outcome. Standard mastoidectomy size was enough for robot-assisted technique. This first study marks the arrival of the era of robotic CI for all ages.

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Evaluation of the HiFocus® electrode array with positioner in human temporal bones

The Journal of Laryngology & Otology ◽

10.1258/002221503322112932 ◽

2003 ◽

Vol 117 (7) ◽

pp. 527-531 ◽

Cited By ~ 32

Author(s):

Antje Aschendorff ◽

Thomas Klenzner ◽

Bernhard Richter ◽

Ralf Kubalek ◽

Heiner Nagursky ◽

...

Keyword(s):

Clinical Outcome ◽

Electrode Array ◽

Scala Tympani ◽

X Ray ◽

Temporal Bones ◽

Scala Vestibuli

The aim of the study presented was to assess the insertion mode and possible intracochlear trauma after implantation of the HiFocus® electrode with positioner in human temporal bones. The study was performed in five freshly frozen temporal bones. The position of electrodes was evaluated using conventional X-ray analysis, rotational tomography and histomorphological analysis. Insertion of the HiFocus® electrode with positioner resulted in considerable trauma to fine cochlear structures including fracture of the osseous spiral lamina, dislocation of the electrode array from the scala tympani into the scala vestibuli and fracture of the modiolus close to the cochleostomy. The implication of the results regarding clinical outcome will be discussed.

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Intra-operative skull X-ray for misdirection of the cochlear implant array into the vestibular labyrinth

The Journal of Laryngology & Otology ◽

10.1017/s0022215115001966 ◽

2015 ◽

Vol 129 (9) ◽

pp. 923-927 ◽

Cited By ~ 4

Author(s):

A M Hassan ◽

R Patel ◽

M Redleaf

Keyword(s):

Computed Tomography ◽

Cochlear Implant ◽

Case Series ◽

Electrode Array ◽

Plain Film ◽

Neural Response ◽

Reliable Indicator ◽

X Ray ◽

Vestibular Labyrinth ◽

Neural Response Telemetry

AbstractObjectives:This paper reports five cases of aberrant cochlear implant electrode array insertion into the vestibular labyrinth. A review of the literature was conducted in order to clarify reasonable preventive and detection strategies and endorse the routine use of intra-operative plain skull X-ray.Methods:The study entailed a clinical case series and literature review. The setting was a tertiary academic referral centre. The following data were evaluated: pre-operative temporal bone computed tomography, operative reports, intra-operative imaging, neural response telemetry/imaging and post-operative imaging.Results:There were no consistent pre-operative risk factors found on computed tomography scans and no reliable intra-operative signs of electrode array misdirection. All misdirections in our case series, and those in the literature, were easily detectable on intra-operative plain film X-ray.Conclusion:These reported cases demonstrate implant misdirection without the surgeon's awareness. Aberrant insertion cannot be anticipated, and neural response telemetry/imaging is not a reliable indicator of misdirection. Routine intra-operative anteroposterior plain X-ray of the head is a reliable indicator of misdirection, and is fast and relatively inexpensive.

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Factors Predicting Postoperative Sentence Scores in Postlinguistically Deaf Adult Cochlear Implant Patients

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348949210100410 ◽

1992 ◽

Vol 101 (4) ◽

pp. 342-348 ◽

Cited By ~ 144

Author(s):

Peter J. Blamey ◽

Brian C. Pyman ◽

Graeme M. Clark ◽

Richard C. Dowell ◽

Michael Gordon ◽

...

Keyword(s):

Regression Analysis ◽

Electrical Stimulation ◽

Cochlear Implant ◽

Electrode Array ◽

Frequency Discrimination ◽

Gap Detection ◽

Scala Tympani ◽

Central Institute ◽

Independent Variables ◽

Profound Deafness

A sample of 64 postlinguistically profoundly to totally deaf adult cochlear implant patients were tested without lipreading by means of the Central Institute for the Deaf (CID) sentence test 3 months postoperatively. Preoperative promontory stimulation results (thresholds, gap detection, and frequency discrimination), age, duration of profound deafness, cause of deafness, lipreading ability, postoperative intracochlear thresholds and dynamic ranges for electrical stimulation, depth of insertion of the electrode array into the scala tympani, and number of electrodes in use were considered as possible factors that might be related to the postoperative sentence scores. A multiple regression analysis with stepwise inclusion of independent variables indicated that good gap detection and frequency discrimination during preoperative promontory testing, larger numbers of electrodes in use, and greater dynamic ranges for intracochlear electrical stimulation were associated with better CID scores. The CID scores tended to decrease with longer periods of profound deafness.

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Intraoperative Correction of Cochlear Implant Electrode Translocation

Audiology and Neurotology ◽

10.1159/000515684 ◽

2021 ◽

pp. 1-5

Author(s):

William G. Morrel ◽

Nauman F. Manzoor ◽

Benoit M. Dawant ◽

Jack H. Noble ◽

Robert F. Labadie

Keyword(s):

Cochlear Implant ◽

Average Distance ◽

Electrode Array ◽

High Rate ◽

Insertion Depth ◽

Electrode Contact ◽

Temporal Bones ◽

Hearing Outcomes ◽

Rate Of Success

Introduction: Translocation of precurved cochlear implant (CI) electrodes reduces hearing outcomes, but it is not known whether it is possible to correct scalar translocation such that all electrodes reside fully in the scala tympani (ST). Methods: Six cadaveric temporal bones were scanned with CT and segmented to delineate intracochlear anatomy. Mastoidectomy with facial recess was performed. Precurved CI electrodes (CI532; Cochlear Limited) were implanted until scalar translocation was confirmed with postoperative CT. Then, electrodes were removed and replaced. CT scan was repeated to assess for translocation correction. Scalar position of electrode contacts, angular insertion depth (AID) of the electrode array, and M– (average distance between each electrode contact and the modiolus) were measured. An in vivo case is reported in which intraoperative translocation detection led to removal and replacement of the electrode. Results: Five of 6 cadaveric translocations (83%) were corrected with 1 attempt, resulting in full ST insertions. AID averaged 285 ± 77° for translocated electrodes compared to 344 ± 28° for nontranslocated electrodes (p = 0.109). M– averaged 0.75 ± 0.18 mm for translocated electrodes and 0.45 ± 0.11 mm for nontranslocated electrodes (p = 0.016). Reduction in M– with translocation correction averaged 38%. In the in vivo case, translocation was successfully corrected in a single attempt. Conclusion: Scalar translocation of precurved CI electrodes can be corrected by removal and reinsertion. This significantly improves the perimodiolar positioning of these electrodes. There was a high rate of success (83%) in this cadaveric model as well as a successful in vivo attempt.

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