The smaller the frequency-to-place mismatch the better the hearing outcomes in cochlear implant recipients?

Electrocochleography-Based Tonotopic Map: II. Frequency-to-Place Mismatch Impacts Speech-Perception Outcomes in Cochlear Implant Recipients

OBJECTIVES

Modern cochlear implants (CIs) use varying-length electrode arrays inserted at varying insertion angles within variably sized cochleae. Thus, there exists an opportunity to enhance CI performance, particularly in postlinguistic adults, by optimizing the frequency-to-place allocation for electrical stimulation, thereby minimizing the need for central adaptation and plasticity. There has been interest in applying Greenwood or Stakhovskaya et al. function (describing the tonotopic map) to postoperative imaging of electrodes to improve frequency allocation and place coding. Acoustically-evoked electrocochleography (ECochG) allows for electrophysiologic best-frequency (BF) determination of CI electrodes and the potential for creating a personalized frequency allocation function. The objective of this study was to investigate the correlation between early speech-perception performance and frequency-to-place mismatch.

DESIGN

This retrospective study included 50 patients who received a slim perimodiolar electrode array. Following electrode insertion, five acoustic pure-tone stimuli ranging from 0.25 to 2 kHz were presented, and electrophysiological measurements were collected across all 22 electrode contacts. Cochlear microphonic tuning curves were subsequently generated for each stimulus frequency to ascertain the BF electrode or the location corresponding to the maximum response amplitude. Subsequently, we calculated the difference between the stimulus frequency and the patient's CI map's actual frequency allocation at each BF electrode, reflecting the frequency-to-place mismatch. BF electrocochleography-total response (BF-ECochG-TR), a measure of cochlear health, was also evaluated for each subject to control for the known impact of this measure on performance.

RESULTS

Our findings showed a moderate correlation (r = 0.51; 95% confidence interval: 0.23 to 0.76) between the cumulative frequency-to-place mismatch, as determined using the ECochG-derived BF map (utilizing 500, 1000, and 2000 Hz), and 3-month performance on consonant-nucleus-consonant words (N = 38). Larger positive mismatches, shifted basal from the BF map, led to enhanced speech perception. Incorporating BF-ECochG-TR, total mismatch, and their interaction in a multivariate model explained 62% of the variance in consonant-nucleus-consonant word scores at 3 months. BF-ECochG-TR as a standalone predictor tended to overestimate performance for subjects with larger negative total mismatches and underestimated the performance for those with larger positive total mismatches. Neither cochlear diameter, number of cochlear turns, nor apical insertion angle accounted for the variability in total mismatch.

CONCLUSIONS

Comparison of ECochG-BF derived tonotopic electrode maps to the frequency allocation tables reveals substantial mismatch, explaining 26.0% of the variability in CI performance in quiet. Closer examination of the mismatch shows that basally shifted maps at high frequencies demonstrate superior performance at 3 months compared with those with apically shifted maps (toward Greenwood and Stakhovskaya et al.). The implications of these results suggest that electrophysiological-based frequency reallocation might lead to enhanced speech-perception performance, especially when compared with conventional manufacturer maps or anatomic-based mapping strategies. Future research, exploring the prospective use of ECochG-based mapping techniques for frequency allocation is underway.

Comprehensive literature review on the application of the otological surgical planning software OTOPLAN® for cochlear implantation

BACKGROUND

The size of the human cochlear, measured by the diameter of the basal turn, varies between 7 and 11 mm. For hearing rehabilitation with cochlear implants (CI), the size of the cochlear influences the individual frequency map and the choice of electrode length. OTOPLAN® (CAScination AG [Bern, Switzerland] in cooperation with MED-EL [Innsbruck, Austria]) is a software tool with CE marking for clinical applications in CI treatment which allows for precise pre-planning based on cochlear size. This literature review aims to analyze all published data on the application of OTOPLAN®.

MATERIALS AND METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied to identify relevant studies published in the PubMed search engine between January 2015 and February 2023 using the search terms "otoplan" [title/abstract] OR "anatomy-based fitting" [title/abstract] OR "otological software tool" [title/abstract] OR "computed tomography-based software AND cochlear" [title/abstract].

RESULTS

The systematic review of the literature identified 32 studies on clinical use of OTOPLAN® in CI treatment. Most studies were reported from Germany (7 out of 32), followed by Italy (5), Saudi Arabia (4), the USA (4), and Belgium (3); 2 studies each were from Austria and China, and 1 study from France, India, Norway, South Korea, and Switzerland. In the majority of studies (22), OTOPLAN® was used to assess cochlear size, followed by visualizing the electrode position using postoperative images (5), three-dimensional segmentation of temporal bone structures (4), planning the electrode insertion trajectory (3), creating a patient-specific frequency map (3), planning of a safe drilling path through the facial recess (3), and measuring of temporal bone structures (1).

CONCLUSION

To date, OTOPLAN® is the only DICOM viewer with CE marking in the CI field that can process pre-, intra-, and postoperative images in the abovementioned applications.

Frequency-to-Place Mismatch Impacts Cochlear Implant Quality of Life, But Not Speech Recognition

OBJECTIVE

To retrospectively compare frequency-place mismatch among adult cochlear implant (CI) recipients with lateral wall (LW) and perimodiolar/Mid Scala (PM/MS) arrays, and to quantify the impact of these factors on early post-activation (3 months) speech recognition abilities and CI-specific quality of life.

METHODS

One hundred and twenty-six adult participants were separated into two groups: (1) 83 participants who underwent CI with a PM/MS array and 43 patients who underwent CI with a LW array. All participants completed the Cochlear Implant Quality of Life Profile (CIQOL-35 Profile) instrument. Angular insertion depth and semitone mismatch, which contribute to frequency-place mismatch, were assessed using post-operative CT scans. Word and speech recognition in quiet were determined using the Consonant-Nucleus-Consonant (CNC) and the AzBio tests, respectively (n = 82 patients).

RESULTS

LW arrays were more deeply inserted and exhibited less semitone mismatch compared to PM/MS arrays. No significant relationship was found between semitone mismatch and early post-operative speech perception scores for either PM/MS or LW arrays. However, greater degrees of semitone mismatch were associated with lower CIQOL-35 profile scores for PM/MS arrays.

CONCLUSIONS AND RELEVANCE

The results of this study indicate that both the degree of frequency-place mismatch, and its impact on CI-specific quality of life, vary by CI array design.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:2898-2905, 2024.

Nasal/Oral Vowel Perception in French-Speaking Children With Cochlear Implants and Children With Typical Hearing

PURPOSE

The present study investigates the perception of vowel nasality in French-speaking children with cochlear implants (CIs; CI group) and children with typical hearing (TH; TH group) aged 4-12 years. By investigating the vocalic nasality feature in French, the study aims to document more broadly the effects of the acoustic limitations of CI in processing segments characterized by acoustic cues that require optimal spectral resolution. The impact of various factors related to children's characteristics, such as chronological/auditory age, age of implantation, and exposure to cued speech, has been studied on performance, and the acoustic characteristics of the stimuli in perceptual tasks have also been investigated.

METHOD

Identification and discrimination tasks involving French nasal and oral vowels were administered to two groups of children: 13 children with CIs (CI group) and 25 children with TH (TH group) divided into three age groups (4-6 years, 7-9 years, and 10-12 years). French nasal vowels were paired with their oral phonological counterpart (phonological pairing) as well as to the closest oral vowel in terms of phonetic proximity (phonetic pairing). Post hoc acoustic analyses of the stimuli were linked to the performance in perception.

RESULTS

The results indicate an effect of the auditory status on the performance in the two tasks, with the CI group performing at a lower level than the TH group. However, the scores of the children in the CI group are well above chance level, exceeding 80%. The most common errors in identification were substitutions between nasal vowels and phonetically close oral vowels as well as confusions between the phoneme /u/ and other oral vowels. Phonetic pairs showed lower discrimination performance in the CI group with great variability in the results. Age effects were observed only in TH children for nasal vowel identification, whereas in children with CIs, a positive impact of cued speech practice and early implantation was found. Differential links between performance and acoustic characteristics were found within our groups, suggesting that in children with CIs, selective use of certain acoustic features, presumed to be better transmitted by the implant, leads to better perceptual performance.

CONCLUSIONS

The study's results reveal specific challenges in children with CIs when processing segments characterized by fine spectral resolution cues. However, the CI children in our study appear to effectively compensate for these difficulties by utilizing various acoustic cues assumed to be well transmitted by the implant, such as cues related to the temporal resolution of stimuli.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.25328704.

[Comprehensive literature review on the application of the otological-surgical planning software OTOPLAN® for cochlear implantation. German version]

BACKGROUND

The size of the human cochlear, measured by the diameter of the basal turn, varies between 7 and 11 mm. For hearing rehabilitation with cochlear implants (CI), the size of the cochlear influences the individual frequency map and the choice of electrode length. OTOPLAN® (CAScination AG [Bern, Switzerland] in cooperation with MED-EL [Innsbruck, Austria]) is a software tool with CE marking for clinical applications in CI treatment which allows for precise pre-planning based on cochlear size. This literature review aims to analyze all published data on the application of OTOPLAN®.

MATERIALS AND METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied to identify relevant studies published in the PubMed search engine between January 2015 and February 2023 using the search terms "otoplan" [title/abstract] OR "anatomy-based fitting" [title/abstract] OR "otological software tool" [title/abstract] OR "computed tomography-based software AND cochlear" [title/abstract].

RESULTS

The systematic review of the literature identified 32 studies on clinical use of OTOPLAN® in CI treatment. Most studies were reported from Germany (7 out of 32), followed by Italy (5), Saudi Arabia (4), the USA (4), and Belgium (3); 2 studies each were from Austria and China, and 1 study from France, India, Norway, South Korea, and Switzerland. In the majority of studies (22), OTOPLAN® was used to assess cochlear size, followed by visualizing the electrode position using postoperative images (5), three-dimensional segmentation of temporal bone structures (4), planning the electrode insertion trajectory (3), creating a patient-specific frequency map (3), planning of a safe drilling path through the facial recess (3), and measuring of temporal bone structures (1).

CONCLUSION

To date, OTOPLAN® is the only DICOM viewer with CE marking in the CI field that can process pre-, intra-, and postoperative images in the abovementioned applications.

Hearing outcomes following cochlear implantation with anatomic or default frequency mapping in postlingual deafness adults

PURPOSE

The aim of this study was to compare the outcomes of different mapping procedures based on anatomic or default frequency distribution in postlingual deafness adults who underwent cochlear implantation (CI).

METHODS

Forty-eight adults with postlingual deafness who underwent CI (MED-EL) from January 2021 to May 2022 in our hospital were prospectively recruited. The participants were randomly assigned to two groups (the anatomic group and the default group). Postoperative computerized tomography (CT) scans were evaluated with Otoplan® to determine the angular insertion depth (AID) and the specific locations of the intracochlear electrodes. Anatomic maps were imported into MAESTRO 9.0 software (MED-EL) for anatomy-based fitting for anatomic group, while default mapping program was set up for the default group. Hearing thresholds, Speech Recognition Scores (SRS), and subjects' auditory and musical abilities were evaluated 1 year after using the CI. Differences were determined in two groups using Stata statistical software, with significance defined as p < 0.05.

RESULTS

SRS under noisy conditions was significantly greater for anatomic group than the default group (p = 0.02). Under quiet conditions, however, mean hearing thresholds (0.5, 1, 2, and 4 kHz) and SRS did not differ significantly between the two groups (p = 0.07). Modified questionnaires showed that auditory (p = 0.02) and musical (p = 0.01) quality were significantly better following the anatomic mapping than the default procedure.

CONCLUSION

CI program based on the anatomic distribution may bring better SRS under noise conditions as well as better auditory and musical qualities than based on the default frequency distribution.

Advancing Cochlear Implant Programming: X-ray Guided Anatomy-Based Fitting

BACKGROUND

Anatomy-based fitting (ABF) is a new research area in the field of cochlear implants (CIs). Despite the reported benefits and acceptable levels of ABF among CI recipients, some limitations remain, like the postoperative computed tomography (CT) scan, which is preferred for confirming electrode array insertion.

OBJECTIVE

This study aimed to investigate the feasibility of using plain film radiography (X-ray) for postoperative electrode detection and for building ABF as an alternative to CT.

METHODS

A total of 53 ears with CI were studied. All cases had routine post-insertion X-rays in the cochlear view and additionally underwent postoperative CT. The insertion angles and center frequencies measured by two independent observers were compared for each imaging modality. The angular insertion depth and center frequencies resulting from the X-ray and CT scans were then compared.

RESULTS

No significant differences were observed between the X-ray- and CT-measured angles for the electrode contacts. Radiographic measurements between the two readers showed an almost perfect (≥0.8) or substantial (0.71) intraclass correlation coefficient along the electrode contacts. X-ray images showed a mean difference of 4.7 degrees from CT. The mean semitone deviation of the central frequency between the CT and X-ray images was 0.6.

CONCLUSIONS

X-ray imaging provides a valid and easy-to-perform alternative to CT imaging, with less radiation exposure and lower costs. The radiographs showed excellent concordance with the CT-measured angular insertion depth and consequently with the central frequency for most electrode contacts. Therefore, plain X-ray could be a viable alternative in building ABF for the CI recipients.

Comparison of Tonotopic and Default Frequency Fitting for Speech Understanding in Noise in New Cochlear Implantees: A Prospective, Randomized, Double-Blind, Cross-Over Study

OBJECTIVES

While cochlear implants (CIs) have provided benefits for speech recognition in quiet for subjects with severe-to-profound hearing loss, speech recognition in noise remains challenging. A body of evidence suggests that reducing frequency-to-place mismatch may positively affect speech perception. Thus, a fitting method based on a tonotopic map may improve speech perception results in quiet and noise. The aim of our study was to assess the impact of a tonotopic map on speech perception in noise and quiet in new CI users.

DESIGN

A prospective, randomized, double-blind, two-period cross-over study in 26 new CI users was performed over a 6-month period. New CI users older than 18 years with bilateral severe-to-profound sensorineural hearing loss or complete hearing loss for less than 5 years were selected in the University Hospital Centre of Rennes in France. An anatomical tonotopic map was created using postoperative flat-panel computed tomography and a reconstruction software based on the Greenwood function. Each participant was randomized to receive a conventional map followed by a tonotopic map or vice versa. Each setting was maintained for 6 weeks, at the end of which participants performed speech perception tasks. The primary outcome measure was speech recognition in noise. Participants were allocated to sequences by block randomization of size two with a ratio 1:1 (CONSORT Guidelines). Participants and those assessing the outcomes were blinded to the intervention.

RESULTS

Thirteen participants were randomized to each sequence. Two of the 26 participants recruited (one in each sequence) had to be excluded due to the COVID-19 pandemic. Twenty-four participants were analyzed. Speech recognition in noise was significantly better with the tonotopic fitting at all signal-to-noise ratio (SNR) levels tested [SNR = +9 dB, p = 0.002, mean effect (ME) = 12.1%, 95% confidence interval (95% CI) = 4.9 to 19.2, standardized effect size (SES) = 0.71; SNR = +6 dB, p < 0.001, ME = 16.3%, 95% CI = 9.8 to 22.7, SES = 1.07; SNR = +3 dB, p < 0.001 ME = 13.8%, 95% CI = 6.9 to 20.6, SES = 0.84; SNR = 0 dB, p = 0.003, ME = 10.8%, 95% CI = 4.1 to 17.6, SES = 0.68]. Neither period nor interaction effects were observed for any signal level. Speech recognition in quiet ( p = 0.66) and tonal audiometry ( p = 0.203) did not significantly differ between the two settings. 92% of the participants kept the tonotopy-based map after the study period. No correlation was found between speech-in-noise perception and age, duration of hearing deprivation, angular insertion depth, or position or width of the frequency filters allocated to the electrodes.

CONCLUSION

For new CI users, tonotopic fitting appears to be more efficient than the default frequency fitting because it allows for better speech recognition in noise without compromising understanding in quiet.

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/.

Postoperative Impedance-Based Estimation of Cochlear Implant Electrode Insertion Depth

OBJECTIVES

Reliable 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.

DESIGN

The 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.

RESULTS

Analysis 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).

CONCLUSIONS

Insertion 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.

Matching the pitch perception of the cochlear implanted ear with the contralateral ear in patients with single-sided deafness: a novel approach

PURPOSE

Single-sided deaf patients following cochlear implantation often compare the sound quality of their implanted ear with normal hearing. The interaural differences can result in dissatisfaction with speech comprehension and reduced time of usage of the speech processor; hence, prolonging auditory adaptation time. The proposed calibration method presented in this study demonstrates how the frequency distribution of the cochlear implant can be set to adequately approximate the pitch perception of the contralateral normal hearing ear towards improving speech intelligibility in a noisy environment.

METHODS

In 12 postlingual single-sided deaf patients, subjective interaural pitch-matching was carried out to determine new central frequencies for the reallocation of the frequency bands of their speech processor (CP910, CP950 or CP1000, Cochlear, Australia). The patients were asked to compare the pitch of the tones presented to their normal hearing ear to the pitch of individual channels of their cochlear implant (CI522 or CI622, Cochlear, Australia). A third-degree polynomial curve was fit to the acquired matching frequencies to create the new frequency allocation table. Audiological measurements (free-field aided thresholds, speech reception thresholds, and monosyllabic word recognition score) in noise, together with a Speech, Spatial and Qualities of Hearing Scale (SSQ12) questionnaire (short version of the original SSQ) results were evaluated prior to the pitch-matching procedure, and again, 2 weeks later.

RESULTS

The free-field aided thresholds of the patients showed no greater shift than ± 5 dB following the procedure; however, their monosyllabic word recognition score in noise improved significantly (mean - 9.58%, SD 4.98%, matched pairs t test comparison: p < 0.001). The results of the SSQ12 questionnaire also showed significant improvement in speech intelligibility, sound localization, and sound quality (mean 0.96 points, SD 0.45 points, matched pairs t test comparison: p < 0.001).

CONCLUSIONS

Matching the pitch perception of the implanted cochlea with the sensation of the normal hearing contralateral ear, resulted in significant changes in the quality of hearing in patients with single-sided deafness. It is plausible the procedure can usher positive results in bimodal patients or following sequential bilateral cochlear implantation.

Otological Planning Software-OTOPLAN: A Narrative Literature Review

The cochlear implant (CI) is a widely accepted option in patients with severe to profound hearing loss receiving limited benefit from traditional hearing aids. CI surgery uses a default setting for frequency allocation aiming to reproduce tonotopicity, thus mimicking the normal cochlea. One emerging instrument that may substantially help the surgeon before, during, and after the surgery is a surgical planning software product developed in collaboration by CASCINATION AG (Bern, Switzerland) and MED-EL (Innsbruck Austria). The aim of this narrative review is to present an overview of the main features of this otological planning software, called OTOPLAN®. The literature was searched on the PubMed and Web of Science databases. The search terms used were "OTOPLAN", "cochlear planning software" "three-dimensional imaging", "3D segmentation", and "cochlear implant" combined into different queries. This strategy yielded 52 publications, and a total of 31 studies were included. The review of the literature revealed that OTOPLAN is a useful tool for otologists and audiologists as it improves preoperative surgical planning both in adults and in children, guides the intraoperative procedure and allows postoperative evaluation of the CI.

Audiological outcomes of robot-assisted cochlear implant surgery

PURPOSE

The main objective of this study is to evaluate the short-term and long-term audiological outcomes in patients who underwent cochlear implantation with a robot-assisted system to enable access to the cochlea, and to compare outcomes with a matched control group of patients who underwent cochlear implantation with conventional access to the cochlea.

METHODS

In total, 23 patients were implanted by robot-assisted cochlear implant surgery (RACIS). To evaluate the effectiveness of robotic surgery in terms of audiological outcomes, a statistically balanced control group of conventionally implanted patients was created. Minimal outcome measures (MOM), consisting of pure-tone audiometry, speech understanding in quiet and speech understanding in noise were performed pre-operatively and at 3 months, 6 months, 12 months and 2 years post-activation of the audioprocessor.

RESULTS

There was no statistically significant difference in pure-tone audiometry, speech perception in quiet and speech perception in noise between robotically implanted and conventionally implanted patients pre-operatively, 3 months, 6 months, 12 months and 2 years post-activation. A significant improvement in pure-tone hearing thresholds, speech understanding in quiet and speech understanding in noise with the cochlear implant has been quantified as of the first measurements at 3 months and this significant improvement remained stable over a time period of 2 years for HEARO implanted patients.

CONCLUSION

Clinical outcomes in robot-assisted cochlear implant surgery are comparable to conventional cochlear implantation. CLINICALTRAILS.

GOV TRAIL REGISTRATION NUMBERS

NCT03746613 (date of registration: 19/11/2018), NCT04102215 (date of registration: 25/09/2019).

Evaluation of the Performance of OTOPLAN-Based Cochlear Implant Electrode Array Selection: A Retrospective Study

Otoplan is a surgical planning software designed to assist with cochlear implant surgery. One of its outputs is a recommendation of electrode array type based on imaging parameters. In this retrospective study, we evaluated the differences in auditory outcomes between patients who were implanted with arrays corresponding to those recommended by the Otoplan software versus those in which the array selection differed from the Otoplan recommendation. Pre-operative CT images from 114 patients were imported into the software, and array recommendations were generated. These were compared to the arrays which had actually been implanted during surgery, both in terms of array type and length. As recommended, 47% of patients received the same array, 34% received a shorter array, and 18% received a longer array. For reasons relating to structure and hearing preservation, 83% received the more flexible arrays. Those who received stiffer arrays had cochlear malformations or ossification. A negative, although non-statistically significant correlation was observed between the CNC scores at 12 months and the absolute value of the difference between recommended array and implanted array. In conclusion, clinicians may be slightly biased toward shorter electrode arrays due to their perceived greater ability to achieve full insertion. Using 3D imaging during the pre-operative planning may improve clinicians' confidence to implant longer electrode arrays, where appropriate, to achieve optimum hearing outcomes.

Using Anatomy-Based Fitting to Reduce Frequency-to-Place Mismatch in Experienced Bilateral Cochlear Implant Users: A Promising Concept

Fitting cochlear implant (CI) users can be challenging. Anatomy-based fitting (ABF) maps may have the potential to lead to better objective and subjective outcomes than conventional clinically based fitting (CBF) methods. ABF maps were created via information derived from exact electrode contact positions, which were determined via post-operative high-resolution flat panel volume computer tomography and clinical fitting software. The outcome measures were speech understanding in quiet and noise and self-perceived sound quality with the CBF map and with the ABF map. Participants were 10 experienced bilateral CI users. The ABF map provided better speech understanding in quiet and noisy environments compared to the CBF map. Additionally, two approaches of reducing the frequency-to-place mismatch revealed that participants are more likely to accept the ABF map if their electrode array is inserted deep enough to stimulate the apical region of their cochlea. This suggests an Angular Insertion Depth of the most apical contact of around 720°-620°. Participants had better speech understanding in quiet and noise with the ABF map. The maps' self-perceived sound quality was similar. ABF mapping may be an effective tool for compensating the frequency-to-place mismatch in experienced bilateral CI users.

Validation of Automatic Cochlear Measurements Using OTOPLAN® Software

INTRODUCTION

Electrode length selection based on case-related cochlear parameters is becoming a standard pre-operative step for cochlear implantation. The manual measurement of the parameters is often time-consuming and may lead to inconsistencies. Our work aimed to evaluate a novel, automatic measurement method.

MATERIALS AND METHODS

A retrospective evaluation of pre-operative HRCT images of 109 ears (56 patients) was conducted, using a development version of the OTOPLAN^® software. Inter-rater (intraclass) reliability and execution time were assessed for manual (surgeons R1 and R2) vs. automatic (AUTO) results. The analysis included A-Value (Diameter), B-Value (Width), H-Value (Height), and CDLOC-length (Cochlear Duct Length at Organ of Corti/Basilar membrane).

RESULTS

The measurement time was reduced from approximately 7 min ± 2 (min) (manual) to 1 min (AUTO). Cochlear parameters in mm (mean ± SD) for R1, R2 and AUTO, respectively, were A-value: 9.00 ± 0.40, 8.98 ± 0.40 and 9.16 ± 0.36; B-value: 6.81 ± 0.34, 6.71 ± 0.35 and 6.70 ± 0.40; H-value: 3.98 ± 0.25, 3.85 ± 0.25 and 3.76 ± 0.22; and the mean CDLoc-length: 35.64 ± 1.70, 35.20 ± 1.71 and 35.47 ± 1.87. AUTO CDLOC measurements were not significantly different compared to R1 and R2 (H0: Rx CDLOC = AUTO CDLOC: p = 0.831, p = 0.242, respectively), and the calculated intraclass correlation coefficient (ICC) for CDLOC was 0.9 (95% CI: 0.85, 0.932) for R1 vs. AUTO; 0.90 (95% CI: 0.85, 0.932) for R2 vs. AUTO; and 0.893 (95% CI: 0.809, 0.935) for R1 vs. R2.

CONCLUSIONS

We observed excellent inter-rater reliability, a high agreement of outcomes, and reduced execution time using the AUTO method.

Imaging-based frequency mapping for cochlear implants - Evaluated using a daily randomized controlled trial

Background

Due to variation in electrode design, insertion depth and cochlear morphology, patients with a cochlear implant (CI) often have to adapt to a substantial mismatch between the characteristic response frequencies of cochlear neurons and the stimulus frequencies assigned to electrode contacts. We introduce an imaging-based fitting intervention, which aimed to reduce frequency-to-place mismatch by aligning frequency mapping with the tonotopic position of electrodes. Results were evaluated in a novel trial set-up where subjects crossed over between intervention and control using a daily within-patient randomized approach, immediately from the start of CI rehabilitation.

Methods

Fourteen adult participants were included in this single-blinded, daily randomized clinical trial. Based on a fusion of pre-operative imaging and a post-operative cone beam CT scan (CBCT), mapping of electrical input was aligned to natural place-pitch arrangement in the individual cochlea. That is, adjustments to the CI's frequency allocation table were made so electrical stimulation of frequencies matched as closely as possible with corresponding acoustic locations in the cochlea. For a period of three months, starting at first fit, a scheme was implemented whereby the blinded subject crossed over between the experimental and standard fitting program using a daily randomized wearing schedule, and thus effectively acted as their own control. Speech outcomes (such as speech intelligibility in quiet and noise, sound quality and listening effort) were measured with both settings throughout the study period.

Results

On a group level, standard fitting obtained subject preference and showed superior results in all outcome measures. In contrast, two out of fourteen subjects preferred the imaging-based fitting and correspondingly had better speech understanding with this setting compared to standard fitting.

Conclusion

On average, cochlear implant fitting based on individual tonotopy did not elicit higher speech intelligibility but variability in individual results strengthen the potential for individualized frequency fitting. The novel trial design proved to be a suitable method for evaluation of experimental interventions in a prospective trial setup with cochlear implants.

Effect of interaural electrode insertion depth difference and independent band selection on sentence recognition in noise and spatial release from masking in simulated bilateral cochlear implant listening

PURPOSE

Inter-aural insertion depth difference (IEDD) in bilateral cochlear implant (BiCI) with continuous interleaved sampling (CIS) processing is known to reduce the recognition of speech in noise and spatial release from masking (SRM). However, the independent channel selection in the 'n-of-m' sound coding strategy might have a different effect on speech recognition and SRM when compared to the effects of IEDD in CIS-based findings. This study aimed to investigate the effect of bilateral 'n-of-m' processing strategy and interaural electrode insertion depth difference on speech recognition in noise and SRM under conditions that simulated bilateral cochlear implant listening.

METHODS

Five young adults with normal hearing sensitivity participated in the study. The target sentences were spatially filtered to originate from 0° and the masker was spatially filtered at 0°, 15°, 37.5°, and 90° using the Oldenburg head-related transfer function database for behind the ear microphone. A 22-channel sine wave vocoder processing based on 'n-of-m' processing was applied to the spatialized target-masker mixture, in each ear. The perceptual experiment involved a test of speech recognition in noise under one co-located condition (target and masker at 0°) and three spatially separated conditions (target at 0°, masker at 15°, 37.5°, or 90° to the right ear).

RESULTS

The results were analyzed using a three-way repeated measure analysis of variance (ANOVA). The effect of interaural insertion depth difference (F (2,8) = 3.145, p = 0.098, ɳ² = 0.007) and spatial separation between target and masker (F (3,12) = 1.239, p = 0.339, ɳ² = 0.004) on speech recognition in noise was not significant.

CONCLUSIONS

Speech recognition in noise and SRM were not affected by IEDD ≤ 3 mm. Bilateral 'n-of-m' processing resulted in reduced speech recognition in noise and SRM.

One Click Is Not Enough: Anatomy-Based Fitting in Experienced Cochlear Implant Users

OBJECTIVE

To evaluate a new methodological approach of applying anatomy-based fitting (ABF) in experienced cochlear implant (CI) users.

PARTICIPANTS

Three experienced unilateral and bilateral CI users with postlingual hearing loss.

INTERVENTION

Postoperative imaging, via a high-volume Dyna computed tomography, and exact electrode measurement positions were integrated into the clinical fitting software following a new procedure, which adapted individual frequency bandwidths within the audio processor.

MAIN OUTCOME MEASURES

Speech perception in quiet and noise, clinical mapping, and self-perceived level of auditory benefit were assessed.

RESULTS

For each CI user, ABF mapping provided better speech perception in quiet and in noise compared with the original clinical fitting mapping. In addition, ABF mapping was accepted in CI users despite unequal bilateral array insertion depths and lengths; however, acceptance was only established if the point of first electrode contact was less than 230 Hz.

CONCLUSIONS

ABF mapping increased the acceptance in CI users with longer electrode arrays and in bilateral CI users who were unsatisfied with their device experience. A larger prospective, randomized investigation is currently underway to assess longitudinal outcomes with ABF mapping.

A Web-Based Automated Image Processing Research Platform for Cochlear Implantation-Related Studies

The robust delineation of the cochlea and its inner structures combined with the detection of the electrode of a cochlear implant within these structures is essential for envisaging a safer, more individualized, routine image-guided cochlear implant therapy. We present Nautilus-a web-based research platform for automated pre- and post-implantation cochlear analysis. Nautilus delineates cochlear structures from pre-operative clinical CT images by combining deep learning and Bayesian inference approaches. It enables the extraction of electrode locations from a post-operative CT image using convolutional neural networks and geometrical inference. By fusing pre- and post-operative images, Nautilus is able to provide a set of personalized pre- and post-operative metrics that can serve the exploration of clinically relevant questions in cochlear implantation therapy. In addition, Nautilus embeds a self-assessment module providing a confidence rating on the outputs of its pipeline. We present a detailed accuracy and robustness analyses of the tool on a carefully designed dataset. The results of these analyses provide legitimate grounds for envisaging the implementation of image-guided cochlear implant practices into routine clinical workflows.

Image-Guided Cochlear Implant Programming: A Systematic Review and Meta-analysis

OBJECTIVE

To review studies evaluating clinically implemented image-guided cochlear implant programing (IGCIP) and to determine its effect on cochlear implant (CI) performance.

DATA SOURCES

PubMed, EMBASE, and Google Scholar were searched for English language publications from inception to August 1, 2021.

STUDY SELECTION

Included studies prospectively compared intraindividual CI performance between an image-guided experimental map and a patient's preferred traditional map. Non-English studies, cadaveric studies, and studies where imaging did not directly inform programming were excluded.

DATA EXTRACTION

Seven studies were identified for review, and five reported comparable components of audiological testing and follow-up times appropriate for meta-analysis. Demographic, speech, spectral modulation, pitch accuracy, and quality-of-life survey data were collected. Aggregate data were used when individual data were unavailable.

DATA SYNTHESIS

Audiological test outcomes were evaluated as standardized mean change (95% confidence interval) using random-effects meta-analysis with raw score standardization. Improvements in speech and quality-of-life measures using the IGCIP map demonstrated nominal effect sizes: consonant-nucleus-consonant words, 0.15 (-0.12 to 0.42); AzBio quiet, 0.09 (-0.05 to 0.22); AzBio +10 dB signal-noise ratio, 0.14 (-0.01 to 0.30); Bamford-Kowel-Bench sentence in noise, -0.11 (-0.35 to 0.12); Abbreviated Profile of Hearing Aid Benefit, -0.14 (-0.28 to 0.00); and Speech Spatial and Qualities of Hearing Scale, 0.13 (-0.02 to 0.28). Nevertheless, 79% of patients allowed to keep their IGCIP map opted for continued use after the investigational period.

CONCLUSION

IGCIP has potential to precisely guide CI programming. Nominal effect sizes for objective outcome measures fail to reflect subjective benefits fully given discordance with the percentage of patients who prefer to maintain their IGCIP map.

Difference in cochlear length between male and female patients

Objective: To compare cochlear duct length (CDL) between male and female patients by evaluating the diameter of the basal turn (distance A) on CT scans.Method: All temporal bone CT scans performed between 2014 and 2020 were reviewed in our medical center. Using multiplanar reconstructions, the length A, which is the greatest distance of the basal turn was measured on both sides. We performed an analysis of variance considering two factors: sex and side. Two different physicians carried out the measurements, an otolaryngologist and a neuroradiologist. The patients who had several CT scans allowed us to evaluate the reliability of our procedure.Results: Among the 888 CT scans reviewed, 8 were excluded because of cochlear malformations. The inter-sex difference of length A was found to be 0.29 millimeters(mm) 95% IC [0.26-0.34] and was longer in the male group (p < 0.0001). Using Alexiades' equation, we found that CDL was 34.5mm [34.37-34.61] in the male group and 33.3mm [33.13-33.38] in the female group. When one side was compared to the other, there was no significant difference (p = 0.226). An intra-class correlation found a good absolute agreement between the two screeners of 0.79.Conclusion: Males have a statistically significant longer CDL than females.