Objectives: The objective was to develop and evaluate a new sentence test, the Sentence Test with Adaptive Randomized Roving levels, intended to emulate everyday listening experience, using both normal-hearing (NH) and cochlear implant (CI) groups, examining practicality, learning, test–retest variability, and interlist variability. Design: In experiment 1, each of 25 NH adults was tested using five lists, each comprising 30 sentences. One male and one female speaker each spoke 15 sentences. Ten sentences were presented at each of three presentation levels: 50, 65, and 80 dB SPL. The relative level of a speech-shaped noise was varied adaptively to estimate the speech reception threshold (SRT). Counterbalance for list order was achieved by staggering the allocation of lists to participants. To allow assessment of learning effects, no practice was given. The variability of mean SRTs across lists was small, but correction factors were derived for each list so that, after correction, all lists gave the same mean SRT. Test–retest variability was estimated by examining the corrected SRTs for each subject’s five lists. In experiment 2, 25 CI users each received one test list after a small amount of practice. Experiment 3 examined the effect of speech rate using time-compressed speech, for age-matched NH and CI users. Results: The mean SRT for the NH participants was approximately −6 dB and was similar for the male and female speakers. There was a small but significant improvement in SRTs between the first and later lists administered, but no further improvement for subsequent lists. On the basis of the variability of the corrected SRTs within each participant, a 2.2 dB difference in SRT is meaningful for comparisons using one test list per condition, for a single participant. The percentage of key words correct varied with presentation level over a 13% range, being best at 65 dB SPL. Only 40% of the CI group achieved an SRT lower than 20 dB for both speakers. There was large individual variability in the SRTs, and SRTs were higher for the female than for the male speaker. For the CI participants, the percentage of key words correct varied markedly with level, from 19% at the lowest level to 57% at the medium level. Time compression had a small effect for NH participants but a very large effect for CI participants. Conclusions: The Sentence Test with Adaptive Randomized Roving levels seems practical to administer and is reasonably sensitive. For NH participants, a 2.2 dB difference in SRT is meaningful for a single list per condition and a single participant. Although learning effects were small for NH participants, it seems prudent to provide some practice sentences when testing hearing-impaired or CI participants. The very large effect of time compression for the CI group has implications for live voice testing of children, because speech rate is only poorly controlled in such testing.

Background: This study examined electrical bioimpedance as a biomarker for intracochlear tissue changes after cochlear implant surgery, comparing monopolar, three-point, and four-point impedance measurements over time and evaluating different measurement systems and approaches. Methods: Impedance measurements were obtained from 21 participants during surgery and at four postoperative stages. Monopolar impedances were recorded using the Bionic Ear Data Collection System (BEDCS) and the Active Insertion Monitoring (AIM) system. Three- and four-point impedances were recorded directly using BEDCS, and indirect three-point impedances were additionally derived from Electrical Field Imaging matrices recorded using BEDCS or AIM. Results: There was an 11% relative error between monopolar measurements from BEDCS and AIM and a 25% discrepancy between direct and indirect three-point measurements. Despite this, direct and indirect measurements from both systems were useful for tracking postoperative impedance shifts. Three- and four-point measurements showed a strong relationship both during and after surgery. Our results suggest that three- and four-point measurements are more specific than monopolar impedances in capturing localized tissue changes. Conclusions: Three- and four-point impedance measurements are potential markers of intracochlear tissue changes over time. While direct three-point impedance measurements offer higher accuracy, indirect measurements provide a feasible alternative for monitoring intracochlear changes in clinical settings lacking the option of direct measurements.

In many healthcare systems electrical stimulation of the human auditory system, using cochlear implants, is a common treatment for severe to profound deafness. This chapter will describe how electrical stimulation manages to compensate for sensory-neural hearing loss by bypassing the damaged cochlea. The challenges involved in the design and application of cochlear implants will be outlined, including the programming of clinical systems to suit the needs of implanted patients. Today’s variety of patient will be reviewed: unilaterally and bilaterally implanted, bimodal users of a cochlear implant as well as a contralateral hearing aid, CROS device users having either asymmetrical hearing loss or single-sided deafness. Alternative devices such as auditory brainstem implants will be described, and additionally the more experimental auditory mid-brain implants and intraneural stimulation approaches. Research that is likely to bring medium term benefits to the clinical application of cochlear implants will also be described.

Objectives: Tip fold-over (TFO) is a rare but critical occurrence in cochlear implant procedures where the electrode array folds back on itself within the cochlea, compromising programming and device performance. Timely intraoperative detection is essential for immediate correction and optimal placement. Electric field imaging (EFI) has shown promise for identifying TFO both intra- and post-operatively. This study evaluates the performance of a TFO detection algorithm implemented in Target CI (Version 1.6) using Advanced Bionics’ cochlear implant systems, validated through bench and patient datasets. Methods: Sample data included (1) bench testing with a plastic cochlea and human temporal bones with and without induced TFOs, confirmed visually or radiographically; (2) intraoperative EFI measurements recorded using the AIM™ system, with electrode placement confirmed through imaging; and (3) historical EFI recordings from the Target CI DataLake, which lacks imaging and programming metadata. The TFO algorithm’s performance was evaluated by assessing its sensitivity and specificity using these datasets. Results: The TFO algorithm achieved 100% sensitivity and specificity in bench models and intraoperative EFI with imaging-confirmed placements. Among 226 intra-op cases, four TFOs were confirmed by imaging, and all were correctly identified by the algorithm. In the large set of DataLake cases (14,734 implants), 0.80% were flagged as potential TFOs. TFO prevalence was higher with pre-curved arrays (1.22%) than straight lateral wall arrays (0.32%). Conclusions: The TFO algorithm showed high reliability with 100% sensitivity and specificity using routine clinical EFI data. While not a replacement for imaging, the TFO algorithm serves as a fast, accessible tool to alert clinicians to potential TFOs.

Objectives: Extracochlear electrodes (EEs), defined as electrode contacts located outside the cochlea, can degrade cochlear implant (CI) performance. We present and validate an Electric Field Imaging (EFI)-based algorithm that helps detect EEs and can be used intra- or post-operatively. Methods: An algorithm for detecting EEs from EFI data was developed. Validation and testing were performed using three datasets: (a) bench models with known EE conditions (saline and resistive load model), (b) clinical EFI recordings from CI recipients with imaging confirmation (CT or plain X-ray), and (c) EFI recordings without imaging. Primary outcomes included the ability to differentiate extracochlear conditions from fully inserted electrode arrays, as well as the concordance between the number of EE contacts identified by the algorithm and those determined from controlled bench configurations or available imaging data. Results: The algorithm reliably differentiated full insertion from EE conditions on bench models and clinical EFI recordings from CI recipients with imaging confirmation. In the imaging-confirmed clinical cohort (6 EE cases among 226 CI recipients), the algorithm achieved 100% sensitivity and specificity. In clinical cases without imaging, the algorithm flagged 3.94% as having extracochlear electrodes, within the range of prevalence reported in the literature. Furthermore, the lateral-wall electrode arrays were associated with a significantly higher extracochlear electrode occurrence compared to the pre-curved arrays. Conclusions: This EFI-based algorithm may provide a useful screening tool for EEs using routine clinical measurements, supporting intra-operative and post-operative detection while reducing reliance on imaging and thereby aiding clinical decision-making. The method can be integrated into existing clinical fitting software workflow and complements recent work on EFI-based tip fold-over detection. The observed sensitivity and specificity suggest that this approach may provide a valuable tool for identifying EEs in situations where imaging is unavailable or impractical.

Objective: To determine whether the internal auditory canal (IAC) can be visualized using magnetic resonance imaging (MRI) in users of a cochlear implant (CI) model that can safely undergo MRI at 3 T. Patients: Four normally hearing controls and three individuals unilaterally implanted with a HiRes Ultra 3D (Advanced Bionics LLC, California, USA). Interventions: Participants underwent 3 T MRI using sequences appropriate for the postoperative surveillance of the IAC. Images in normally hearing individuals were acquired after placing a fully functional, unpowered, CI underneath a swimming cap at each of eight candidate scalp positions, four on each side of the head. Images were compared to a control condition without a CI present. and CI users were imaged with similar sequences. Main Outcome Measures: In normally hearing controls, the likely impact of the artifact on detection of pathology for multiple neuroradiological locations as rated by two independent radiologists. In CI users, a qualitative assessment of the diagnostic usability of images. Results: Visibility of the ipsilateral IAC and cochlea varied among the three CI users, with images from one participant deemed largely usable, while those from the other two participants exhibited less diagnostic certainty, likely due to differences in implant locations and cranial/neuroanatomical variations. Ratings of images in normally hearing participants showed that more middle-to-anterior CI locations were associated with reduced likelihood of overlooking gross abnormalities. Conclusion: Through meticulous surgical placement, bilateral IAC visualization may be achievable for monitoring chronic health conditions such as tumor surveillance in high-risk patients, and as a safety monitoring outcome measure in clinical trials.