Electrode array design determines scalar position, dislocation rate and angle and postoperative speech perception

Is the Position of the Basal-Most Electrode Depending on Electrode Array Design and Influencing Postoperative Speech Perception? A Retrospective Analysis of 495 Ears

OBJECTIVE

The objective of this study is to examine the influence of electrode array design on the position of the basal-most electrode in cochlear implant (CI) surgery and therefore the stimulability of the basal cochlea. Specifically, we evaluated the angular insertion depth of the basal-most electrode in perimodiolar and straight electrode arrays in relation to postoperative speech perception.

MATERIALS AND METHODS

We conducted a retrospective analysis of 495 patients between 2013 and 2018 using the Cochlear™ Contour Advance® (CA), Cochlear™ Slim Straight® (SSA), or Cochlear™ Slim Modiolar® (SMA) electrode arrays, as well as the MED-EL Flex24 (F24), MED-EL Flex28 (F28), and MED-EL FlexSoft (F31.5) electrode arrays. Cochlear size and the position of the basal-most electrode were measured using rotational tomography or cone beam computed tomography, and the results were compared with postoperative speech perception in monosyllables and numbers.

RESULTS

The straight electrode arrays, specifically the F31.5 (31.5 mm length) and the F28 (28 mm length), exhibited a significantly greater angular insertion depth of the basal-most electrode. No significant correlation was found between cochlear morphology measurements and the position of the basal-most electrode artifact. Cochleostomy-inserted electrode arrays showed a significantly higher insertion depth of the basal-most electrode. Nevertheless, the position of the basal-most electrode did not have a significant impact on postoperative speech perception.

CONCLUSION

Straight electrode arrays with longer lengths achieved deeper angular insertion depths of the basal-most electrode. Cochlear morphology does not have a substantial influence on the position of basal-most electrode. The study confirms that the basal area of the cochlea, responsible for high-frequency range during acoustic stimulation, is not the primary region for speech understanding via electrical stimulation with CI.

Evaluation of insertion quality of a slim perimodiolar electrode array

OBJECTIVES

The influence of cochlear morphology and electrode array design on scalar position and dislocation rates is of great interest in CI surgery. The aim of this study is to evaluate scalar position and specific points of dislocation in relation to cochlear morphology in patients implanted with a new slim perimodiolar electrode array.

MATERIALS AND METHODS

Patients were implanted using the slim modiolar electrode array (= SMA) (= 532/632 electrode array of Cochlear™). Postoperative imaging was performed via cone beam computed tomography (CBCT) and the scans were analyzed regarding cochlear morphology (distances A and B and cochlear height), scalar location of the electrode array, basal insertion depth and apical insertion angle. Furthermore, electrode array design and surgical protocols were evaluated.

RESULTS

81 ears implanted with the SMA were retrospectively included. We evaluated 3 electrode array tip fold over intraoperatively via X-ray imaging and performed revision during the same surgery. The CBCT scans showed 76 initial scala tympani (ST) insertions without dislocation. Two ears showed a dislocated array, one at 77° and the other at 163°. Three arrays were inserted into scala vestibuli (SV) via cochleostomy. These patients showed no signs of obliteration. Cochlear morphology showed no influence on angular insertion depth and scalar position.

CONCLUSIONS

The SMA showed a very low rate of scalar dislocations due to its slim electrode array design (2.7%). We could find a learning curve regarding the handling and the risk of dislocation and tip fold over with this electrode array. The rate of intraoperative tip fold over detection via X-ray imaging was 3.7%. Therefore, we highly recommend X-ray imaging and transimpedance matrix measurements within the surgery protocol. Scala vestibuli insertions happened in patients with cochleostomy only. We could identify two specific points of dislocation depending on electrode array design.

[Insertion of a second electrode array-a rare complication of CI reimplantation. German version]

Due to a technical defect or a medical indication, it may be necessary to explant a cochlear implant. This case report shows that there is the risk of encountering a nonremovable electrode array-as described here from the scala tympani-during cochlear reimplantation. In the present case, insertion of a second electrode array into the free and nonobstructed scala vestibuli was successful. Nonetheless, the indication for reimplantation must be carefully considered, especially in patients with tolerable limitations with little or no loss of speech understanding. Furthermore, surgery should not be performed solely because an implant upgrade is desired.

Systematic Review of Intracochlear Measurements and Effect on Postoperative Auditory Outcomes after Cochlear Implant Surgery

OBJECTIVE

Quality and adequacy of the electrode neuron interface (ENI) is postulated to be a determining factor in affecting auditory outcomes after cochlear implantation. This study aims to review radiological parameters affecting ENI, including angular insertion (AngI), wrapping factor (WF), scalar translocation (ScaT), and electrode-modiolar distance (EMD) and their effect on auditory outcomes.

DATABASES REVIEWED

PubMed, MEDLINE, Embase, Scopus, OpenGrey, and Google Scholar from inception to 01 September 2022.

METHODS

Inclusion criteria were (i) all humans with any cochlear implant (CI); (ii) postoperative cross-sectional imaging with electrode position factors of AngI, ScaT, EMD, and/or WF; and (iii) associated auditory outcomes. Search was restricted to English-language literature. Two independent reviewers performed title and abstract screening, data extraction, and ROBINS-I risk of bias assessment. Formal statistical analysis not performed due to data heterogeneity. PROSPERO (CRD42022359198).

RESULTS

Thirty-one studies (n = 2,887 patients, 3,091 electrodes) underwent qualitative synthesis. Higher AngI (n = 1921 patients) demonstrated positive correlation in 11 studies, no correlation in eight studies, and negative correlation in four studies. ScaT (n = 2,115 patients) demonstrated negative correlation in 12 studies, none in six studies, and one unclear correlation. Larger EMD (n = 240 patients) showed negative correlation in two studies, no correlation in one, and unclear correlation in one study. Smaller WF (n = 369 patients) demonstrated no correlation in three studies and positive correlation in one study.

CONCLUSIONS

Our study finds variable reported relationship between AngI and auditory outcomes. CI electrodes with a ScaT or larger EMD are more likely to exhibit poorer outcomes, and WF does not correlate with outcomes.

Comparison of speech perception in bimodal cochlear implant patients with respect to the cochlear coverage

BACKGROUND

The hearing success of patients with bimodal fitting, utilizing both a cochlear implant (CI) and a hearing aid (HA), varies considerably: While some patients benefit from bimodal CI and HA, others do not.

OBJECTIVES

This retrospective study aimed to investigate speech perception in bimodally fitted patients and compare it with the cochlear coverage (CC).

METHODS

The CC was calculated with the OTOPLAN software, measuring the cochlear duct length on temporal bone CT scans of 39 patients retrospectively. The patients were categorized into two groups: CC ≤ 65% (CC500) and CC > 65% (CC600). Monaural speech intelligibility for monosyllables at a sound pressure level (SPL) of 65 dB in a free-field setting was assessed before and after CI at various time points. The two groups, one with preoperative HA and one with postoperative CI, were compared. Additionally, speech intelligibility was correlated with CC in the entire cohort before CI and at the last available follow-up (last observation time, LOT).

RESULTS

Overall, there was no significant difference in speech intelligibility between CC500 and CC600 patients, with both groups demonstrating a consistent improvement after implantation. While CC600 patients tended to exhibit earlier improvement in speech intelligibility, CC500 patients showed a slower initial improvement within the first 3 months but demonstrated a steeper learning curve thereafter. At LOT, the two patient groups converged, with no significant differences in expected speech intelligibility. There was no significant relationship between unimodal/unilateral free-field speech intelligibility and CC. Interestingly, patients with a CC of 70-75% achieved the highest speech intelligibility.

CONCLUSION

Despite of the lack of a significant correlation between CC and speech perception, patients appeared to reach their maximum in unimodal/unilateral speech perception primarily at a coverage level of 70-75%. Nevertheless, further investigation is warranted, as CC500 was associated with shorter cochlear duct length, and different types of electrodes were used in both groups.

Insertion of a second electrode array-a rare complication of CI reimplantation

Due to a technical defect or a medical indication, it may be necessary to explant a cochlear implant. This case report shows that there is the risk of encountering a nonremovable electrode array-as described here from the scala tympani-during cochlear reimplantation. In the present case, insertion of a second electrode array into the free and nonobstructed scala vestibuli was successful. Nonetheless, the indication for reimplantation must be carefully considered, especially in patients with tolerable limitations with little or no loss of speech understanding. Furthermore, surgery should not be performed solely because an implant upgrade is desired.

Word Recognition with a Cochlear Implant in Relation to Prediction and Electrode Position

BACKGROUND

the word recognition score (WRS) achieved with cochlear implants (CIs) varies widely. To account for this, a predictive model was developed based on patients' age and their pre-operative WRS. This retrospective study aimed to find out whether the insertion depth of the nucleus lateral-wall electrode arrays contributes to the deviation of the CI-achieved WRS from the predicted WRS.

MATERIALS AND METHODS

patients with a pre-operative maximum WRS > 0 or a pure-tone audiogram ≥80 dB were included. The insertion depth was determined via digital volume tomography.

RESULTS

fifty-three patients met the inclusion criteria. The median WRS achieved with the CI was 70%. The comparison of pre- and post-operative scores achieved with a hearing aid and a CI respectively in the aided condition showed a median improvement of 65 percentage points (pp). A total of 90% of the patients improved by at least 20 pp. The majority of patients reached or exceeded the prediction, with a median absolute error of 11 pp. No significant correlation was found between the deviation from the predicted WRS and the insertion depth.

CONCLUSIONS

our data support a previously published model for the prediction of the WRS after cochlear implantation. For the lateral-wall electrode arrays evaluated, the insertion depth did not influence the WRS with a CI.

Effect of Cochlear Implant Electrode Insertion Depth on Speech Perception Outcomes: A Systematic Review

Objective

The suitable electrode array choice is broadly discussed in cochlear implantation surgery. Whether to use a shorter electrode length under the aim of structure preservation versus choosing a longer array to achieve a greater cochlear coverage is a matter of debate. The aim of this review is to identify the impact of the insertion depth of a cochlear implant (CI) electrode array on CI users' speech perception outcomes.

Databases Reviewed

PubMed was searched for English-language articles that were published in a peer-reviewed journal from 1997 to 2022.

Methods

A systematic electronic search of the literature was carried out using PubMed to find relevant literature on the impact of insertion depth on speech perception. The review was conducted according to the preferred reporting items for systematic reviews and meta-analyses guidelines of reporting. Studies in both, children and adults with pre- or postlingual hearing loss, implanted with a CI were included in this study. Articles written in languages other than English, literature reviews, meta-analyses, animal studies, histopathological studies, or studies pertaining exclusively to imaging modalities without reporting correlations between insertion depth and speech outcomes were excluded. The risk of bias was determined using the "Risk of Bias in Nonrandomized Studies of Interventions" tool. Articles were extracted by 2 authors independently using predefined search terms. The titles and abstracts were screened manually to identify studies that potentially meet the inclusion criteria. The extracted information included: the study population, type of hearing loss, outcomes reported, devices used, speech perception outcomes, insertion depth (linear insertion depth and/or the angular insertion depth), and correlation between insertion depth and the speech perception outcomes.

Results

A total of 215 relevant studies were assessed for eligibility. Twenty-three studies met the inclusion criteria and were analyzed further. Seven studies found no significant correlation between insertion depth and speech perception outcomes. Fifteen found either a significant positive correlation or a positive effect between insertion depth and speech perception. Only 1 study found a significant negative correlation between insertion depth and speech perception outcomes.

Conclusion

Although most studies reported a positive effect of insertion depth on speech perception outcomes, one-third of the identified studies reported no correlation. Thus, the insertion depth must be considered as a contributing factor to speech perception rather than as a major decisive criterion.

Registration

This review has been registered in PROSPERO, the international prospective register of systematic reviews (CRD42021257547), available at https://www.crd.york.ac.uk/PROSPERO/.

Robot-Assisted and Manual Cochlear Implantation: An Intra-Individual Study of Speech Recognition

Cochlear implantation (CI) allows rehabilitation for patients with severe to profound hearing impairment. Although the use of a robotic assistant provides technical assistance to the surgeon, the assessment of the impact of its use on auditory outcomes remains uncertain. We aim to compare the hearing results of patients who underwent bilateral cochlear implantation; one side was performed with manual insertion and the other side with robot-assisted insertion. The electrode array intrascalar positioning and the surgery duration were also studied. This retrospective intra-individual study involved 10 patients who underwent bilateral cochlear implantation. The study included two infants and eight adults. The unique composition of this cohort enabled us to utilize each patient as their own control. Regarding speech disyllabic recognition, pure tone average, ECAP, ratio of array translocation, basilar membrane rupture, and percentage of translocated electrodes, there was no difference between manual and robot-assisted CI groups. This study is the first to compare intra-individual hearing performance after cochlear implantation, either manually or robot-assisted. The number of patients and the time delay between manual and robotic implantation may have led to a lack of power, but there was no apparent difference in hearing performance between manual and robotic implantation.

[Speech perception as a function of cochlear coverage-comparison in bimodally hearing cochlear implant patients. German version]

BACKGROUND

Hearing success in bimodally hearing patients with a cochlear implant (CI) and a hearing aid (HA) exhibits different results: while some benefit from bimodal CI and HA, others do not.

OBJECTIVE

The aim of this study was to investigate hearing success in terms of speech perception in bimodally fitted patients in relation to the cochlear coverage (CC) of the CI electrodes.

MATERIALS AND METHODS

Using the OTOPLAN software (CAScination AG, Bern, Switzerland), CC was retrospectively measured from CT scans of the temporal bone of 39 patients, who were then categorized into two groups: CC ≤ 65% (CC⁵⁰⁰) and CC > 65% (CC⁶⁰⁰). Monaural speech intelligibility for monosyllables at a sound pressure level (SPL) of 65 dB in open field was assessed at various timepoints, preoperatively with HA and postoperatively with CI, and compared between the groups. In addition, speech intelligibility was correlated with CC in the entire cohort before surgery and during follow-up (FU).

RESULTS

Overall, no significant differences in speech intelligibility were found between CC⁵⁰⁰ and CC⁶⁰⁰ patients at any of the FU timepoints. However, both CC⁵⁰⁰ and CC⁶⁰⁰ patients showed a steady improvement in speech intelligibility after implantation. While CC⁶⁰⁰ patients tended to show an earlier improvement in speech intelligibility, CC⁵⁰⁰ patients tended to show a slower improvement during the first 3 months and a steeper learning curve thereafter. The two patient groups converged during FU, with no significant differences in speech intelligibility. There was no significant relationship between unimodal/unilateral free-field speech intelligibility and CC. However, patients with a CC of 70-75% achieved maximum speech intelligibility.

CONCLUSION

Despite a nonsignificant correlation between CC and speech discrimination, patients seem to reach their maximum in unimodal/unilateral speech understanding mainly at 70-75% coverage. However, there is room for further investigation, as CC⁵⁰⁰ was associated with a shorter cochlear duct length (CDL), and long and very long electrodes were used in both groups.

Association between lateral wall electrode array insertion parameters and audiological outcomes in bilateral cochlear implantation

Purpose

The aims of this study were to compare speech recognition at different postoperative times for both ears in bilaterally implanted patients and to assess the influence of the time of deafness, frequency-to-place mismatch, angular insertion depth (AID) and angular separation between neighbouring electrode contacts on audiometric outcomes.

Methods

This study was performed at an academic tertiary referral centre. A total of 19 adult patients (6 men, 13 women), who received sequential bilateral implantation with lateral wall electrode arrays, were analysed in retrospective. Statistical analysis was performed using two-sided t test, Wilcoxon test, median test, and Spearman’s correlation.

Results

Postlingually deafened patients (deafness after the age of 10) had a significantly better speech perception (WRS65[CI]) than the perilingually deafened subjects (deafness at the age of 1–10 years) (p < 0.001). Comparison of cochlear duct length between peri- and postlingually deafened subjects showed a slightly significantly smaller cochleae in perilingual patients (p = 0.045). No association between frequency-to-place mismatch as well as angular separation and speech perception could be detected. There was even no significant difference between the both ears in the intraindividual comparison, even if insertion parameters differed.

Conclusion

The exact electrode position seems to have less influence on the speech comprehension of CI patients than already established parameters as preoperative speech recognition or duration of deafness.

Long-term data of the new transcutaneous partially implantable bone conduction hearing system Osia®

PURPOSE

The new active transcutaneous partially implantable osseointegrated system Cochlear™ Osia® System is indicated in case of conductive or mixed hearing loss (CHL/MHL) with a maximum average bone conduction hearing loss of 55 dB, or in single-sided deafness (SSD). The implant directly stimulates the bone via a piezoelectric transducer and is directed by an external sound processor. We conducted a monocentric retrospective longitudinal within-subject clinical study at our tertiary academic referral center. The aim was to investigate long-term data (2017-2021) on audiological outcomes and hearing-related quality of life for the Osia system.

METHODS

Between 2017 and 2020, 22 adults (18: CHL/MHL; 3: SSD) were implanted with the Osia100 implant; seven received bilateral implants. As of 10/2020, the sound processor was upgraded to Osia 2.

RESULTS

Mean Osia system use by 04/2021 was 30.9 ± 8.6 months (range 17-40 months). Unaided bone conduction thresholds were unchanged postoperatively. One patient had to be explanted because of prolonged wound infection. Aided hearing thresholds were significantly lower compared to the unaided thresholds preoperatively, along with a marked increase in speech recognition in quiet. Speech processor upgrade resulted in a stable benefit. Patients with CHL/MHL and SSD showed a similar improvement in self-rated hearing performance revealed by SSQ, APHAB, and HUI questionnaires.

CONCLUSION

The Osia system is a safe, effective and sustainable option for treatment of conductive and mixed hearing loss or single-sided deafness.