Dataset Information

Effectiveness of skull X-RAY to determine cochlear implant insertion depth.

ABSTRACT:

Background

Cochlear implant (CI) insertion depth can affect residual hearing preservation, tonotopic range coverage, and Mapping. Therefore, determining insertion depth has the potential to maximize CI performance. A post-op skull X-RAY is commonly used to assess insertion depth, however its effectiveness has not been well established. Our primary objective was to assess the accuracy of post-op skull X-RAYs to determine insertion depth, compared to CT as the gold standard. Secondary objectives were to compare experience level of raters and different skull X-RAY views.

Methods

Thirteen patients with Advanced Bionic HiRes 90 K implants, and post-operative temporal bone CT scans were selected from the CI database at Sunnybrook Health Sciences Centre. Medical students, otology fellows, and CI surgeons evaluated insertion depths on post-op skull X-RAYs, while neuroradiologists evaluated CT scans. Descriptive statistics, regression analysis, and paired t-tests were used to compare the two types of imaging.

Results

X-RAYs and CTs provided an equivalent mean insertion depth of 337 degrees (p?=?0.93), a mean difference of -?0.9 degrees and a standard deviation of paired differences of 43 degrees. Although means were similar across rater groups, CI surgeons (45 degrees) had the lowest standard deviation of paired differences. Comparing X-RAY views, Caldwell (29 degrees) had less variation than Towne (59 degrees) for standard deviation of paired differences.

Conclusions

Skull X-RAYs provide accurate and reliable measurements for CI insertion depth. The Caldwell view alone may be sufficient for evaluations of insertion depth, and experience has a minor impact on the variability of estimates.

SUBMITTER: Fernandes V

PROVIDER: S-EPMC6122652 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Publications

Effectiveness of skull X-RAY to determine cochlear implant insertion depth.

Fernandes Vinay V Wang Yiqiao Y Yeung Robert R Symons Sean S Lin Vincent V

Journal of otolaryngology - head & neck surgery = Le Journal d'oto-rhino-laryngologie et de chirurgie cervico-faciale 20180903 1

<h4>Background</h4>Cochlear implant (CI) insertion depth can affect residual hearing preservation, tonotopic range coverage, and Mapping. Therefore, determining insertion depth has the potential to maximize CI performance. A post-op skull X-RAY is commonly used to assess insertion depth, however its effectiveness has not been well established. Our primary objective was to assess the accuracy of post-op skull X-RAYs to determine insertion depth, compared to CT as the gold standard. Secondary obje ...[more]

PMID: 30176926

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Project description:ObjectivesReliable determination of cochlear implant electrode positions shows promise for clinical applications, including anatomy-based fitting of audio processors or monitoring of electrode migration during follow-up. Currently, electrode positioning is measured using radiography. The primary objective of this study is to extend and validate an impedance-based method for estimating electrode insertion depths, which could serve as a radiation-free and cost-effective alternative to radiography. The secondary objective is to evaluate the reliability of the estimation method in the postoperative follow-up over several months.DesignThe ground truth insertion depths were measured from postoperative computed tomography scans obtained from the records of 56 cases with an identical lateral wall electrode array. For each of these cases, impedance telemetry records were retrieved starting from the day of implantation up to a maximum observation period of 60 mo. Based on these recordings, the linear and angular electrode insertion depths were estimated using a phenomenological model. The estimates obtained were compared with the ground truth values to calculate the accuracy of the model.ResultsAnalysis of the long-term recordings using a linear mixed-effects model showed that postoperative tissue resistances remained stable throughout the follow-up period, except for the two most basal electrodes, which increased significantly over time (electrode 11: ~10 Ω/year, electrode 12: ~30 Ω/year). Inferred phenomenological models from early and late impedance telemetry recordings were not different. The insertion depth of all electrodes was estimated with an absolute error of 0.9 mm ± 0.6 mm or 22° ± 18° angle (mean ± SD).ConclusionsInsertion depth estimations of the model were reliable over time when comparing two postoperative computed tomography scans of the same ear. Our results confirm that the impedance-based position estimation method can be applied to postoperative impedance telemetry recordings. Future work needs to address extracochlear electrode detection to increase the performance of the method.

Project description:IntroductionOnly a small percentage (6-10%) of patients who are candidates receive cochlear implants (CIs). One potential reason contributing to low usage rates may be confusion regarding which patients to refer for CI evaluation. The extent to which information provided by standard clinical audiologic assessments is sufficient for selecting appropriate CI evaluation referrals is uncertain. The objective of this study is to evaluate the capacity of standard clinical audiologic measures to differentiate CI candidates from noncandidates.MethodThe study design is a retrospective review of a prospectively maintained CI database from a university-based tertiary medical center of 518 patients undergoing CI evaluations from 2012 to 2020. Each ear of each patient was treated as an independent value. Receiver operating characteristic (ROCs) curves were constructed using aided AzBio sentence recognition scores in quiet and aided AzBio +10 dB signal-to-noise ratio scores <60% as binary classifiers for CI candidacy. For each ROC, we examined the capacity of multiple pure-tone thresholds, pure-tone average (PTA), and CNC word recognition scores (WRSs) measured under earphones to determine CI candidacy. Area under the curve ROC (AUC-ROC) values were calculated to demonstrate the capacity of each model to differentiate CI candidates from noncandidates.ResultsVariables with the greatest capacity to accurately differentiate CI candidates from noncandidates using aided AzBio in quiet scores were earphone CNC WRS, earphone pure-tone threshold at 1,000 Hz, and earphone PTA (AUC-ROC values = 0.86-0.88). Using aided AzBio +10 scores as the measure for candidacy, only CNC word recognition had a fair capacity to identify candidates (AUC-ROC value = 0.73). Based on the ROCs, a 1,000 Hz pure-tone threshold >50 dB HL, PTA >57 dB HL, and a monosyllabic WRS <60% can each serve as individual indicators for referral for CI evaluations.ConclusionThe current study provides initial indicators for referral and a first step at developing evidence-based criteria for CI evaluation referral using standard audiologic assessments.

Project description:Using long Med-El Combi40+ electrode arrays, it is now possible to cover the whole range of the cochlea, up to about two turns. Such insertion depths have received little attention. To evaluate the contribution of deeply inserted electrodes, five Med-El cochlear implant users were tested on vowel and consonant identification tests with fittings with first one, two, and up to five apical electrodes being deactivated. In addition, subjects performed pitch-ranking experiments, using loudness-balanced stimuli, to identify electrodes creating pitch confusions. Radiographs were taken to measure each electrode insertion depth. All subjects used each modified fitting for two periods of about 3 weeks. During the experiment, the same stimulation rate and frequency range were maintained across all the fittings used for each individual subject. After each trial period the subject had to perform three consonant and three vowel identification tests. All subjects showed deep electrode insertions ranging from 605 degrees to 720 degrees. The two subjects with the deepest electrode insertions showed significantly increased vowel- and consonant-identification performances with fittings with the two or three most apical electrodes deactivated compared to their standard fitting with all available electrodes activated. The other three subjects did not show significant improvements in performance when one or two of their most apical electrodes were deactivated. Four out of five subjects preferred to continue use of a fitting with one or more apical electrodes deactivated. The two subjects with the deepest insertions also showed pitch confusions between their most apical electrodes. Two possible reasons for these results are discussed. One is to reduce neural interactions related to electrodes producing pitch confusions. Another is to improve the alignment of the frequency components of sounds coded by the electrical signals delivered to each electrode to the overall pitch of the auditory perception produced by the electrical stimulation of auditory nerve fibers.

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Dataset Information

Effectiveness of skull X-RAY to determine cochlear implant insertion depth.

Background

Methods

Results

Conclusions

Publications

Effectiveness of skull X-RAY to determine cochlear implant insertion depth.

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