Transimpedance Matrix Can Be Used to Estimate Electrode Positions Intraoperatively and to Monitor Their Positional Changes Postoperatively in Cochlear Implant Patients

OBJECTIVE

Accurate positioning of the electrode array during cochlear implant (CI) surgery is crucial for achieving optimal hearing outcomes. Traditionally, postoperative radiological imaging has been used to assess electrode position. Transimpedance matrix (TIM) measurements have also emerged as a promising method for assessing electrode position. This involves utilizing electric field imaging to create an electric distance matrix by analyzing voltage variations among adjacent electrodes. This study aimed to investigate the feasibility of using intraoperative TIM measurements to estimate electrode position and monitor postoperative changes.

STUDY DESIGN

Retrospective cohort study.

SETTING

University Medical center, tertiary academic referral center.

PATIENTS

Patients undergoing CI (CI622) surgery between January 2019 and June 2022.

INTERVENTION

CI electrode positions and maximal angular insertion depths (maxAID) were determined using X-ray imaging according to Stenvers' projection. The mean gradient phase (MGP) was extracted from the TIM, and a correlation between the MGP and maxAID was examined. A model was then built to estimate the maxAID using the MGP, and changes in electrode location over time were assessed using this model.

MAIN OUTCOME MEASURES

Twenty-four patients were included in this study. A positive correlation between the maxAID and the MGP ( R = 0.7, p = 0.0001) was found. The established model was able to predict the maxAID with an accuracy of 27.7 ± 4.4°. Comparing intraoperative and postoperative TIM measurements, a decrease of 24.1° ± 10.7° in maxAID over time was observed.

CONCLUSION

TIM measurements are useful for estimating the insertion depth of the electrode and monitoring changes in the electrode's position over time.

Effects of Intraoperative Cochlear Implant Electrode Conditioning on Impedances and Electrically Evoked Compound Action Potentials

OBJECTIVE

The current study investigates whether, during a Cochlear Implant (CI) surgery, conditioning (i.e. applying short bursts of electrical stimulation) within a saline solution can have positive effects on subsequent intra-operative measurements. We hypothesize that, based on previous research, the impedance values will be reduced, and that the reproducibility of Electrically Evoked Compound Action Potentials (ECAPs) is improved as a result of conditioning.

METHODS

We conditioned half of the electrode contacts, within a saline solution, before CI insertion, using 23 MED-EL implants. Impedance was measured for both the conditioned and non-conditioned groups at five time points. Repeated ECAP recordings were measured and compared between the conditioned and non-conditioned groups.

RESULTS

Impedance of the electrode contacts were reduced by 31% after conditioning in saline solution; however, there were no clinically relevant differences after the implantation of the electrode array. The hypothesis that measurement reproducibility would be increased after conditioning could not be confirmed with our data. Within the saline solution, we observed that 44% of the electrode contacts were covered with air bubbles, which most disappeared after implantation. However, these air bubbles limited the effectiveness of the conditioning within the saline solution. Lastly, the effect of conditioning on the reference electrode stimulation was approximately 16% of the total reduction in impedance.

CONCLUSION

Our data does not suggest that intraoperative conditioning is clinically required for cochlear implantation with MED-EL implants. Additionally, an in-vivo ECAP recording can be considered as a method of conditioning the electrode contacts.

SIGNIFICANCE

We confirm that the common clinical practice does not need to be changed.

[OLSA level control in monaural speech audiometry in background noise for the evaluation of the CI fitting result]

SCIENTIFIC BACKGROUND

Speech audiometry measurements under the influence of background noise are a fundamental part of evaluating the outcome of hearing care. As yet far, there are no recommendations for selecting a suitable method for adaptive speech audiometry measurements in background noise in cochlear implant (CI) care, so either the choice the adaptive level change of the speech signal (S) with constant noise (N) or the adaptive level change of N with constant S.

OBJECTIVES

Do the measurement results of the monaural speechrecognition threshold in noise (SRT) with the Oldenburg Sentence Test (OLSA) depend on the choice of level control?

MATERIAL AND METHODS

A total of 50 series of measurements with OLSA in noise and the Freiburg speech intelligibility test in quiet (FBE) on middle-aged CI patients from clinical routine.

RESULTS

There is no significant difference in the measurement results with different level controls when the SRT is less than 5 [Formula: see text]. Below 55 % monosyllabic intelligibility in quiet, the SRT in noise becomes greater than 5 [Formula: see text].

CONCLUSION

From a clinical, audiological and methodological point of view, it is advisable to carry out the adaptive monaural speech intelligibility measurement with a constant speech signal at 65 [Formula: see text].

[Interactive intraoperative annotation of surgical landmarks in student education to support learning efficiency and motivation]

BACKGROUND

The development of technological innovations has not only changed social life and the healthcare system, but also affects medical education. The aim of this pilot study was to evaluate whether students, when observing a microsurgical procedure of the temporal bone, gain an additional understanding of the anatomical structures and surgical site when visualization is used that provides identical views for the surgeon and viewer in 3D.

MATERIALS AND METHODS

During regular attendance tutorials, students were randomly assigned to three different groups: control group, 2D group, or 3D group. Evaluation questionnaires and intraoperative student annotation of the surgical view were used to assess the subjective didactic value of different visualization formats and resultant learning experiences for the students.

RESULTS

A total of 47 students were included in the investigations during conventional attendance tutorials. The majority indicated a high added value of the 3D visualization in terms of method (70%) and vividness (80%) compared to the 2D group and self-study; 69% of the students fully agreed with the statement that 2D and 3D visualization increases learning motivation and is a very good way to improve recognition of anatomical topography and structures.

CONCLUSION

New interactive visualization options in teaching promote learning efficiency and motivation among students. Especially 3D visualization and intraoperative annotation of the surgical view by the student is a useful didactic tool and increases the quality of clinical teaching. It supports the perception of anatomical topography and enables more focused surgical training.

Active Middle Ear Implant Evoked Auditory Brainstem Response Intensity-Latency Characteristics

Objective

To analyze intensity-latency functions of intraoperative auditory evoked brainstem responses (ABRs) to stimulation by the Vibrant Soundbridge (VSB) active middle ear implant with respect to coupling efficiency, VSB evoked ABR thresholds, and coupling modality [oval window (OW) placement vs. Incus placement and vs. round window (RW) placement].

Study Design

Exploratory study.

Setting

Bi-centric study at tertiary referral centers.

Patients

Twenty-four patients (10 female, 14 male, mean age: 58 years) who received a VSB.

Outcome Measures

Wave-V intensity-latency functions of intraoperative VSB evoked ABRs using a modified audio processor programmed to preoperative bone conduction thresholds for stimulation. Threshold level correction to coupling efficiency and ABR thresholds. Individual plots and exponential function fits.

Results

After ABR threshold level correction, the latency functions could be aligned. A large variance of latencies was observed at individual threshold level. Wave-V latency was longest in the Incus placement subgroup (9.73 ms, SD: 1.04) as compared to OW placement subgroup (9.47 ms, SD: 1.05), with the shortest latency in the RW placement subgroup (8.99 ms, SD: 0.68). For increasing stimulation levels, the variance decreased with intensity-latency function slopes converging toward a steady-state (saturation) latency caused by saturation of audio processor (stimulation) gain. Latency saturation was reached at a stimulation level of 50 dB nHL for the OW placement subgroup, 35 dB nHL for the Incus placement subgroup, and 30 dB nHL for the RW placement subgroup. The latency and saturation results indicated decreased dynamic range for RW placement, i.e., reverse stimulation.

Conclusions

VSB evoked ABR wave-V intensity-latency function slopes were similar to acoustic stimulation at high stimulation levels with a shift toward longer latencies caused by audio processor signal delay. Saturation of latencies occurred for higher stimulation levels due to saturation of audio processor gain. Thus, the analysis of VSB evoked intensity-latency functions appears to allow for the objective assessment of a patient's individual dynamic range. This can further improve diagnostics as well as intraoperative and postoperative quality control.

Interactive live-stream surgery contributes to surgical education in the context of contact restrictions

BACKGROUND

Attendance teaching is the predominant teaching method at universities but needs to be questioned in the context of digital transformation. This study establishes and evaluates a method to accomplish electronic learning to supplement traditional attendance courses.

MATERIALS AND METHODS

Surgery was transmitted in real-time conditions via an online live stream from the surgical theater. Visualization was transferred from a fully digital surgical microscope, an endoscope or an environmental camera in high definition quality. Students were able to participate at home from their personal computer. After following the surgery, they participated in an online-evaluation.

RESULTS

A total of 65 students participated in the live stream. The majority of students (61.54%) indicated a significant subjective increase in knowledge after participation. The majority of students (53.85%) indicated that live surgeries should be offered as a permanent component in addition to classroom teaching. Likewise, a broader offer was desired by many students (63.08%).

CONCLUSIONS

Live streaming of surgery is a promising approach as an alternative or supplement to traditional attendance teaching. An expansion of digital teaching can be explicitly supported on the basis of this study.

Mapping Cochlear Duct Length to Electrically Evoked Compound Action Potentials in Cochlear Implantation

OBJECTIVE

Objective measurements may assist in indicating cochlear implants and in predicting outcomes of cochlear implantation surgery. Using electrically evoked compound action potentials (ECAP), information about the function of the auditory nerve can be obtained by analyzing responses to electrical stimulation transmitted and derived by the recording electrode. The aim of this study was to determine whether ECAP characteristics differ depending on the stimulated intracochlear region and the size of the cochlea.

STUDY DESIGN

Retrospective cohort study.

SETTING

University Medical center, tertiary academic referral center.

PATIENTS

Patients undergoing cochlear implant surgery between 2015 and 2018.

INTERVENTION

Cochlear implantation with FLEXsoft electrode arrays (length 31.5 mm, 12 stimulating channels).

MAIN OUTCOME MEASURES

The cochlear duct length (CDL) and the cochlear coverage (CC) were measured using a new computed tomography-based software and correlated to the postoperative speech performance. Additionally, ECAP were measured and associated to the CDL.

RESULTS

A total of 59 ears of 53 cochlear implant users with a mean age of 63.6 (SD 14.9) years were included. The mean estimated CDL was 35.0 (SD 2.2) mm. The mean CC was 90.3% (SD 5.5%). A total of 4,873 ECAP were measured. A statistically significant, moderate, negative correlation between the ECAP slope and the site of stimulation was found (r = -0.29, 95% confidence interval: -0.32 to -0.27, p < 0.0001). No correlation between the CC and the speech performance was found (r = -0.08, 95% confidence interval: -0.33 to 0.18 p = 0.52).

CONCLUSION

ECAP slopes seem to be a reliable tool to identify the electrode's position inside the cochlea and also showed correlations to the anatomy of the patient. A combination of objective measurements such as anatomical parameters and ECAPs are helpful to assist the postoperative fitting and are promising tools to improve patient care.

The Role of Stimulus Type and Social Signal for Voice Perception in Cochlear Implant Users: Response to the Letter by Meister et al

Purpose In their letter, Meister et al. (2020) appropriately point to a potential influence of stimulus type, arguing cochlear implant (CI) users may have the ability to use timbre cues only for complex stimuli such as sentences but not for brief stimuli such as vowel-consonant-vowel or single words. While we cannot exclude this possibility on the basis of Skuk et al. (2020) alone, we hold that there is a strong need to consider type of social signal (e.g., gender, age, emotion, speaker identity) to assess the profile of preserved and impaired aspects of voice processing in CI users. We discuss directions for further research to systematically consider interactive effects of stimulus type and social signal. In our view, this is crucial to understand and enhance nonverbal vocal perception skills that are relevant to successful communication with a CI.

Parameter-Specific Morphing Reveals Contributions of Timbre and Fundamental Frequency Cues to the Perception of Voice Gender and Age in Cochlear Implant Users

Purpose Using naturalistic synthesized speech, we determined the relative importance of acoustic cues in voice gender and age perception in cochlear implant (CI) users. Method We investigated 28 CI users' abilities to utilize fundamental frequency (F0) and timbre in perceiving voice gender (Experiment 1) and vocal age (Experiment 2). Parameter-specific voice morphing was used to selectively control acoustic cues (F0; time; timbre, i.e., formant frequencies, spectral-level information, and aperiodicity, as defined in TANDEM-STRAIGHT) in voice stimuli. Individual differences in CI users' performance were quantified via deviations from the mean performance of 19 normal-hearing (NH) listeners. Results CI users' gender perception seemed exclusively based on F0, whereas NH listeners efficiently used timbre. For age perception, timbre was more informative than F0 for both groups, with minor contributions of temporal cues. While a few CI users performed comparable to NH listeners overall, others were at chance. Separate analyses confirmed that even high-performing CI users classified gender almost exclusively based on F0. While high performers could discriminate age in male and female voices, low performers were close to chance overall but used F0 as a misleading cue to age (classifying female voices as young and male voices as old). Satisfaction with CI generally correlated with performance in age perception. Conclusions We confirmed that CI users' gender classification is mainly based on F0. However, high performers could make reasonable usage of timbre cues in age perception. Overall, parameter-specific morphing can serve to objectively assess individual profiles of CI users' abilities to perceive nonverbal social-communicative vocal signals.

Intraoperative quantification of floating mass transducer coupling quality in active middle ear implants: a multicenter study

Purpose

Evaluating the effectiveness of intraoperative auditory brainstem responses (ABRs) to stimulation by the Vibrant Soundbridge (VSB) active middle ear implant for quantifying the implant’s floating mass transducer (FMT) coupling quality.

Methods

In a diagnostic multicentric study, patients (> 18 years) who received a VSB with different coupling modalities were included. Pre- and postoperative bone conduction thresholds, intraoperative VSB-evoked ABR thresholds (VSB-ABR) using a modified audio processor programmed to preoperative bone conduction thresholds, postoperative vibrogram thresholds, and postoperative VSB-ABR thresholds were measured. Coupling quality was calculated from the difference between the pure tone average at 1000, 2000, and 4000 Hz (3PTA) vibrogram and postoperative 3PTA bone conduction thresholds.

Results

Twenty-three patients (13 males, 10 females, mean age 56.6 (± 12.5) years) were included in the study. Intraoperative VSB-ABR response thresholds could be obtained in all except one patient where the threshold was > 30 dB nHL. Postoperatively, an insufficient coupling of 36.7 dB was confirmed in this patient. In a Bland–Altman analysis of the intraoperative VSB-ABRs and coupling quality, the limits of agreement exceeded ± 10 dB, i.e., the maximum allowed difference considered as not clinically important but the variation was within the general precision of auditory brainstem responses to predict behavioral thresholds. Five outliers were identified. In two patients, the postoperative VSB-ABR thresholds were in agreement with the coupling quality, indicating a change of coupling before the postoperative testing.

Conclusion

The response thresholds recorded in this set-up have the potential to predict the VSB coupling quality and optimize postoperative audiological results.

Automated detection of electrically evoked stapedius reflexes (eSR) during cochlear implantation

Introduction

In cochlear implantation, objective fitting methods are needed to optimize audiological results in small children or patients with poor compliance. Intraoperatively measured electrically evoked stapedius reflexes (eSR) can be used as a marker for the patient’s discomfort level. The aim of this study was to develop and evaluate an automated detection method for eSR and to compare it to the detection rate of the surgeon and independent observers.

Methods

Cochlear implantation using a fully digital surgical microscope was performed. Movements of the stapedius tendon were recorded and analyzed by means of computer vision technique. Differences in eSR elicited by stimulating electrodes at different cochlear locations (basal, middle and apical) were analyzed. The eSR detection rate of the image processing algorithm was compared to the surgeon’s detection rate and to those of two less experienced observers.

Results

A total of 387 electrically impulses were applied. The stimulation of middle turn electrodes showed significantly higher detection rates (50.4%) compared to the basal (40.0%; p = 0.001) and apical (43.6%; p = 0.03) turn. The software identified significantly more of the applied stimuli (58.4%) compared to the surgeon (46.3%; p = 0.0007), the intermediate observer (37.7%; p < 0.0001) and the unexperienced observer (41.3%; p < 0.0001).

Conclusion

The feasibility of an automated intraoperative software-based detection of eSR is demonstrated. By improving the eSR detection methods and their clinical applicability, their utility in objective cochlear implant fitting may be substantially increased.

Multizentrische Analyse des Nutzerverhaltens von Cochlea-Implantat-Trägern

Zusammenfassung Neuartige Cochlear-Implant-Sprachprozessoren bieten die Möglichkeit der Speicherung von Nutzungsdaten (Datalogging). Mit Hilfe dieser Informationen kann eine gezieltere individuelle Betreuung von Patienten ermöglicht werden. Allerdings fehlen bisher Normdaten in größerem Umfang zum individuellen Nutzungsverhalten.

Material und Methoden Im Rahmen einer retrospektiven Studie wurden die Nutzungsdaten von 2687 Patienten ausgewertet. Alle Patienten waren mit dem Nucleus 6-System der Firma Cochlear Ltd. versorgt.

Ergebnisse Die Daten ermöglichen für die Nutzungsdauer bzw. Tragedauern von Cochlear-Implant-Sprachprozessoren einen Normalbereich festzulegen. Ebenso ist die Identifikation von auffälligem Nutzungsverhalten möglich.